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Sample records for acoustic doppler current

  1. Buoyancy package for self-contained acoustic doppler current profiler mooring

    Venkatesan, R.; Krishnakumar, V.

    A buoyancy package for self-contained Acoustic Doppler Current Profiler(SC-ADCP 1200 RD instruments USA) was designed and fabricated indigenously, for subsurface mooring in coastal waters. The system design is discussed. The design to keep SC...

  2. Acoustic Doppler Current Profiling near Myrtle Bend, June 3, 2013, Kootenai River near Bonners Ferry, ID

    U.S. Geological Survey, Department of the Interior — Acoustic doppler current profiling (ADCP) data was collected to describe streamflow characteristics including total streamflow, velocity magnitude and secondary...

  3. Acoustic Doppler Current Profiling near Shorty's Island, June 1, 2012, Kootenai River near Bonners Ferry, ID

    U.S. Geological Survey, Department of the Interior — An Acoustic Doppler Current Profiler (ADCP) was used to survey streamflow characteristics including total streamflow, velocity magnitude and secondary flow...

  4. Estimation of Surface Winds From Upward Looking Acoustic Doppler Current Profilers

    Brown, Juan; Barton, Eric D.; Trasviña, Armando; Vélez, Héctor S.; Kosro, P. Michael; Robert L. Smith

    1992-01-01

    Three upward looking acoustic Doppler current profilers (ADCP) were deployed beneath meteorological buoys in the Gulf of Tehuantepec, Mexico, during winter 1988–1989. Hourly averaged wind speed data from the buoys and from ship when in the vicinity were compared with surface acoustic backscatter intensity recorded at the ADCPs. The backscatter was found to be a significant predictor of wind speeds from both buoy and ship, the latter when within 50 km of the mooring site. There was no apparent...

  5. Continuous measurements of discharge from a horizontal acoustic Doppler current profiler in a tidal river

    A. J. F. Hoitink; F. A. Buschman; Vermeulen, B.

    2009-01-01

    Acoustic Doppler current profilers (ADCPs) can be mounted horizontally at a river bank, yielding single-depth horizontal array observations of velocity across the river. This paper presents a semideterministic, semistochastic method to obtain continuous measurements of discharge from horizontal ADCP (HADCP) data in a tidal river. In the deterministic part, single-depth velocity data are converted to specific discharge by applying the law of the wall, which requires knowledge of local values o...

  6. High-resolution velocimetry in energetic tidal currents using a convergent-beam acoustic Doppler profiler

    Sellar, Brian [Univ. of Edinburgh, Scotland (United Kingdom); Harding, Samuel F. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Richmond, Marshall C. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2015-07-16

    An array of convergent acoustic Doppler velocimeters has been developed and tested for the high resolution measurement of three-dimensional tidal flow velocities in an energetic tidal site. This configuration has been developed to increase spatial resolution of velocity measurements in comparison to conventional acoustic Doppler profilers (ADPs) which characteristically use diverging acoustic beams emanating from a single instrument. This is achieved using converging acoustic beams with a sample volume at the focal point of 0.03 m3. The array is also able to simultaneously measure three-dimensional velocity components in a profile throughout the water column, and as such is referred to herein as a converging-beam acoustic Doppler profiler (CADP). Mid-depth profiling is achieved through integration of the sensor platform with the operational Alstom 1MW DeepGen-IV Tidal Turbine. This proof-of-concept paper outlines system configuration and comparison to measurements provided by co-installed reference instrumentation. Comparison of CADP to standard ADP velocity measurements reveals a mean difference of 8 mm/s, standard deviation of 18 mm/s, and order-of-magnitude reduction in realizable length-scale. CADP focal point measurements compared to a proximal single-beam reference show peak cross-correlation coefficient of 0.96 over 4.0 s averaging period and a 47% reduction in Doppler noise. The dual functionality of the CADP as a profiling instrument with a high resolution focal point make this configuration a unique and valuable advancement in underwater velocimetry enabling improved turbulence, resource and structural loading quantification and validation of numerical simulations. Alternative modes of operation have been implemented including noise-reducing bi-static sampling. Since waves are simultaneously measured it is expected that derivatives of this system will be a powerful tool in wave-current interaction studies.

  7. Ocean currents measured by Shipboard Acoustic Doppler Current Profilers (SADCP) from global oceans accumulated at Joint Archive for SADCP from 2004 to 2013 (NODC Accession 0123302)

    National Oceanic and Atmospheric Administration, Department of Commerce — Absolute U- and V-component ocean current vectors from Shipboard Acoustic Doppler Current Profilers (SADCP), as both a high-frequency sampling (nominally 5 minutes...

  8. Variance of discharge estimates sampled using acoustic Doppler current profilers from moving boats

    Garcia, Carlos M.; Tarrab, Leticia; Oberg, Kevin; Szupiany, Ricardo; Cantero, Mariano I.

    2012-01-01

    This paper presents a model for quantifying the random errors (i.e., variance) of acoustic Doppler current profiler (ADCP) discharge measurements from moving boats for different sampling times. The model focuses on the random processes in the sampled flow field and has been developed using statistical methods currently available for uncertainty analysis of velocity time series. Analysis of field data collected using ADCP from moving boats from three natural rivers of varying sizes and flow conditions shows that, even though the estimate of the integral time scale of the actual turbulent flow field is larger than the sampling interval, the integral time scale of the sampled flow field is on the order of the sampling interval. Thus, an equation for computing the variance error in discharge measurements associated with different sampling times, assuming uncorrelated flow fields is appropriate. The approach is used to help define optimal sampling strategies by choosing the exposure time required for ADCPs to accurately measure flow discharge.

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

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

    2015-06-01

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

  10. Monitoring suspended sediment transport in an ice-affected river using acoustic Doppler current profilers

    Moore, S. A.; Ghareh Aghaji Zare, S.; Rennie, C. D.; Ahmari, H.; Seidou, O.

    2013-12-01

    Quantifying sediment budgets and understanding the processes which control fluvial sediment transport is paramount to monitoring river geomorphology and ecological habitat. In regions that are subject to freezing there is the added complexity of ice. River ice processes impact flow distribution, water stage and sediment transport. Ice processes typically have the largest impact on sediment transport and channel morphodynamics when ice jams occur during ice cover formation and breakup. Ice jams may restrict flow and cause local acceleration when released. Additionally, ice can mechanically scour river bed and banks. Under-ice sediment transport measurements are lacking due to obvious safety and logistical reasons, in addition to a lack of adequate measurement techniques. Since some rivers can be covered in ice during six months of the year, the lack of data in winter months leads to large uncertainty in annual sediment load calculations. To address this problem, acoustic profilers are being used to monitor flow velocity, suspended sediment and ice processes in the Lower Nelson River, Manitoba, Canada. Acoustic profilers are ideal for under-ice sediment flux measurements since they can be operated autonomously and continuously, they do not disturb the flow in the zone of measurement and acoustic backscatter can be related to sediment size and concentration. In March 2012 two upward-facing profilers (1200 kHz acoustic Doppler current profiler, 546 KHz acoustic backscatter profiler) were installed through a hole in the ice on the Nelson River, 50 km downstream of the Limestone Generating Station. Data were recorded for four months, including both stable cover and breakup periods. This paper presents suspended sediment fluxes calculated from the acoustic measurements. Velocity data were used to infer the vertical distribution of sediment sizes and concentrations; this information was then used in the interpretation of the backscattered intensity data. It was found that

  11. Improving H-Q rating curves in temprorary streams by using Acoustic Doppler Current meters

    Marchand, P.; Salles, C.; Rodier, C.; Hernandez, F.; Gayrard, E.; Tournoud, M.-G.

    2012-04-01

    Intermittent rivers pose different challenges to stream rating due to high spatial and temporal gradients. Long dry periods, cut by short duration flush flood events explain the difficulty to obtain reliable discharge data, for low flows as well as for floods: problems occur with standard gauging, zero flow period, etc. Our study aims to test the use of an acoustic Doppler currentmeter (ADC) for improving stream rating curves in small catchments subject to large variations of discharge, solid transport and high eutrophication levels. The study is conducted at the outlet of the river Vène, a small coastal river (67 km2) located close to the city of Montpellier (France). The low flow period lasts for more than 6 month; during this period the river flow is sustained by effluents from urban sewage systems, which allows development of algae and macrophytes in the riverbed. The ADC device (Sontek ®Argonaut SW) is a pulsed Doppler current profiling system designed for measuring water velocity profiles and levels that are used to compute volumetric flow rates. It is designed for shallow waters (less than 4 meter depth). Its main advantages are its low cost and high accuracy (±1% of the measured velocity or ±0.05 m/sec, as reported by the manufacturer). The study will evaluate the improvement in rating curves in an intermittent flow context and the effect of differences in sensitivity between low and high water level, by comparing mean flow velocity obtained by ADC to direct discharges measurements. The study will also report long-term use of ADC device, by considering effects of biofilms, algae and macrophytes, as well as solid transport on the accuracy of the measurements. In conclusion, we show the possibility to improve stream rating and continuous data collection of an intermittent river by using a ADC with some precautions.

  12. Correcting acoustic Doppler current profiler discharge measurements biased by sediment transport

    Mueller, D.S.; Wagner, C.R.

    2007-01-01

    A negative bias in discharge measurements made with an acoustic Doppler current profiler (ADCP) is attributed to the movement of sediment on or near the streambed, and is an issue widely acknowledged by the scientific community. The integration of a differentially corrected global positioning system (DGPS) to track the movement of the ADCP can be used to avoid the systematic bias associated with a moving bed. DGPS, however, cannot provide consistently accurate positions because of multipath errors and satellite signal reception problems on waterways with dense tree canopy along the banks, in deep valleys or canyons, and near bridges. An alternative method of correcting for the moving-bed bias, based on the closure error resulting from a two-way crossing of the river, is presented. The uncertainty in the mean moving-bed velocity measured by the loop method is shown to be approximately 0.6cm/s. For the 13 field measurements presented, the loop method resulted in corrected discharges that were within 5% of discharges measured utilizing DGPS to compensate for moving-bed conditions. ?? 2007 ASCE.

  13. Validation of HF radar probing of the vertical shear of surface currents by acoustic Doppler current profiler measurements

    Ivonin, Dmitry V.; Broche, Pierre; Devenon, Jean-Luc; Shrira, Victor I.

    2004-04-01

    There exists no practical way of measuring vertical shear in the water just below the air/sea interface that contains information on air/water momentum fluxes. The paper is concerned with the validation of a recently proposed method of remote sensing of sea subsurface shear by means of a commonly used single-frequency HF radar based on the use of the second-order Bragg echo. To this end a dedicated field experiment was carried out off the French Mediterranean coast. In parallel with the HF radar probing, the independent simultaneous measurements of the subsurface shear profile were obtained by means of acoustic Doppler current profiler mounted on a floating platform, whose position was monitored by GPS. The comparison shows a fairly good agreement of the results (the discrepancy does not exceed 15%) and suggests a higher accuracy of the HF probing.

  14. Temperature, conductivity, pressure, oxygen concentration, beam attenuation, Chlorophyll-a fluorescence, current speed and direction, and particle size distribution collected from moored platform using CTD, ADCP, acoustic Doppler velocimeter, and benthic optical sensors in Monterey Bay from 2011-05-03 to 2012-10-29 (NODC Accession 0123606)

    National Oceanic and Atmospheric Administration, Department of Commerce — Observational oceanographic data obtained by an autonomous moored CTD profiler, thermistor mooring, acoustic Doppler current profiler, acoustic Doppler velocimeter,...

  15. Comparison of acoustic doppler current profiler and Price AA mechanical current meter measurements made during the 2011 Mississippi River Flood

    O'Brien, Patrick; Mueller, David; Pratt, Thad

    2012-01-01

    The Mississippi River and Tributaries project performed as designed during the historic 2011 Mississippi River flood, with many of the operational decisions based on discharge targets as opposed to stage. Measurement of discharge at the Tarbert Landing, Mississippi range provides critical information used in operational decisions for the floodways located in Louisiana. Historically, discharge measurements have been made using a Price AA current meter and the mid-section method, and a long record exists based on these types of measurements, including historical peak discharges. Discharge measurements made using an acoustic Doppler current profiler from a moving boat have been incorporated into the record since the mid 1990's, and are used along with the Price AA mid-section measurements. During the 2011 flood event, both methods were used and appeared to provide different results at times. The apparent differences between the measurement techniques are due to complex hydrodynamics at this location that created large spatial and temporal fluctuations in the flow. The data and analysis presented herein show the difference between the two methods to be within the expected accuracy of the measurements when the measurements are made concurrently. The observed fluctuations prevent valid comparisons of data collected sequentially or even with different observation durations.

  16. Acoustic Doppler current profiling from the JGOFS Arabian Sea cruises aboard the RV T.G. Thompson

    Kim, H.S.; Flagg, C.N.; Shi, Y. [Brookhaven National Lab., Upton, NY (United States). Oceanographic and Atmospheric Sciences Div.

    1996-12-01

    Acoustic Doppler current profiler (ADCP) data is part of the core data for the US JGOFS Arabian Sea project, along with hydrographic and nutrient data. Seventeen cruises are scheduled to take place between September 1994 and January 1996 on the R/V T.G. Thompson. Seven of the cruises follow a standard cruise track, taking hydrographic, chemical and biological measurements. The rest of the cruises, which take place generally within the standard cruise region defined by a set track, are for the deployment and recovery of moored equipment and towing of a SeaSoar. Detailed description of ADCP hardware, the AutoADCP data acquisition system, and the collection of navigation and compass data on the Thompson is documented in Section 2. Followed by data collection for each cruise together with a cruise track, Section 3 presents the processing and analysis of velocity and acoustic backscatter intensity data. Section 5 shows results of profile quality diagnosis.

  17. Acoustic Doppler Current Profiler Measurements in the Tailrace at John Day Dam

    Cook, Chris B.; Dibrani, Berhon; Serkowski, John A.; Richmond, Marshall C.; Titzler, P. Scott; Dennis, Gary W.

    2006-01-30

    Acoustic Doppler current profilers (ADCPs) were used to measure water velocities in the tailrace at John Day Dam over a two-week period in February 2005. Data were collected by the Pacific Northwest National Laboratory for the Hydraulic Design Section, Portland District, U.S. Army Corps of Engineers (USACE). The objective of this project was therefore to collect field measurements of water velocities in the near-field draft tube exit zone as well as the far-field tailrace to be used for improving these models. Field data were collected during the project using five separate ADCPs. Mobile ADCP data were collected using two ADCPs mounted on two separate boats. Data were collected by either holding the boat on-station at pre-defined locations for approximately 10 minutes or in moving transect mode when the boat would move over large distances during the data collection. Results from the mobile ADCP survey indicated a complex hydrodynamic flow field in the tailrace downstream of John Day Dam. A large gyre was noted between the skeleton section of the powerhouse and non-spilling portion of the spillway. Downstream of the spillway, the spillway flow is constrained against the navigation lock guide wall, and large velocities were noted in this region. Downstream of the guide wall, velocities decreased as the spillway jet dispersed. Near the tailrace island, the flow split was measured to be approximately equal on Day 2 (25.4 kcfs spillway/123 kcfs total). However, approximately 60% of the flow passed along the south shore of the island on Day 1 (15.0 kcfs spillway/150 kcfs total). At a distance of 9000 ft downstream of the dam, flows had equalized laterally and were generally uniform over the cross section. The collection of water velocities near the draft tube exit of an operating turbine unit is not routine, and equipment capable of measuring 3D water velocities in these zones are at the forefront of hydraulic measurement technology. Although the feasibility of

  18. Ocean currents measured by Shipboard Acoustic Doppler Current Profiler (SADCP) from global oceans as part of the Joint Archive for Shipboard ADCP holdings from 16 June 1985 to 22 July 2003 (NODC Accession 0001206)

    National Oceanic and Atmospheric Administration, Department of Commerce — Absolute U- and V-component ocean current vectors from Shipboard Acoustic Doppler Current Profilers (SADCP), as both a high frequency sampling (nominally 5 minutes...

  19. Ocean currents measured by Shipboard Acoustic Doppler Current Profiler (SADCP) from global oceans as part of the Joint Archive for Shipboard ADCP holdings from 16 June 1985 to 23 March 2001 (NCEI Accession 0000755)

    National Oceanic and Atmospheric Administration, Department of Commerce — Absolute U- and V-component ocean current vectors from Shipboard Acoustic Doppler Current Profilers (SADCP), as both a high frequency sampling (nominally 5 minutes...

  20. Ocean currents measured by Shipboard Acoustic Doppler Current Profiler (SADCP) from global oceans as part of the Joint Archive for SADCP holdings from 20 August 1999 to 13 May 2009 (NCEI Accession 0067774)

    National Oceanic and Atmospheric Administration, Department of Commerce — Absolute U- and V-component ocean current vectors from Shipboard Acoustic Doppler Current Profilers (SADCP), as both a high-frequency sampling (nominally 5 minutes...

  1. QRev—Software for computation and quality assurance of acoustic doppler current profiler moving-boat streamflow measurements—User’s manual for version 2.8

    Mueller, David S.

    2016-01-01

    The software program, QRev computes the discharge from moving-boat acoustic Doppler current profiler measurements using data collected with any of the Teledyne RD Instrument or SonTek bottom tracking acoustic Doppler current profilers. The computation of discharge is independent of the manufacturer of the acoustic Doppler current profiler because QRev applies consistent algorithms independent of the data source. In addition, QRev automates filtering and quality checking of the collected data and provides feedback to the user of potential quality issues with the measurement. Various statistics and characteristics of the measurement, in addition to a simple uncertainty assessment are provided to the user to assist them in properly rating the measurement. QRev saves an extensible markup language file that can be imported into databases or electronic field notes software. The user interacts with QRev through a tablet-friendly graphical user interface. This report is the manual for version 2.8 of QRev.

  2. Acoustic Doppler current profiler applications used in rivers and estuaries by the U.S. Geological Survey

    Gotvald, Anthony J.; Oberg, Kevin A.

    2009-01-01

    The U.S. Geological Survey (USGS) has collected streamflow information for the Nation's streams since 1889. Streamflow information is used to predict floods, manage and allocate water resources, design engineering structures, compute water-quality loads, and operate water-control structures. The current (2007) size of the USGS streamgaging network is over 7,400 streamgages nationwide. The USGS has progressively improved the streamgaging program by incorporating new technologies and techniques that streamline data collection while increasing the quality of the streamflow data that are collected. The single greatest change in streamflow measurement technology during the last 100 years has been the development and application of high frequency acoustic instruments for measuring streamflow. One such instrument, the acoustic Doppler current profiler (ADCP), is rapidly replacing traditional mechanical current meters for streamflow measurement (Muste and others, 2007). For more information on how an ADCP works see Simpson (2001) or visit http://hydroacoustics.usgs.gov/. The USGS has used ADCPs attached to manned or tethered boats since the mid-1990s to measure streamflow in a wide variety of conditions (fig. 1). Recent analyses have shown that ADCP streamflow measurements can be made with similar or greater accuracy, efficiency, and resolution than measurements made using conventional current-meter methods (Oberg and Mueller, 2007). ADCPs also have the ability to measure streamflow in streams where traditional current-meter measurements previously were very difficult or costly to obtain, such as streams affected by backwater or tides. In addition to streamflow measurements, the USGS also uses ADCPs for other hydrologic measurements and applications, such as computing continuous records of streamflow for tidally or backwater affected streams, measuring velocity fields with high spatial and temporal resolution, and estimating suspended-sediment concentrations. An overview

  3. Observations of near-inertial waves in acoustic Doppler current profiler measurements made during the Mixed Layer Dynamics Experiment

    Chereskin, T. K.; Levine, M. D.; Harding, A. J.; Regier, L. A.

    1989-06-01

    Measurements of upper ocean shear made during the Mixed Layer Dynamics Experiment (MILDEX) provide evidence of large horizontal scale motion at near-inertial frequency. The measurements consist of shipboard acoustic Doppler current profiles. Four large-scale spatial surveys of 2-4 days duration were made by the R/V Wecoma as a set of boxes approximately 60 km per side around a drifting current meter buoy. Velocity time series from the drifting buoy and from sonar measurements made from FLIP also indicated the presence of motions at near-inertial frequency. Horizontal length and time scales of the motion are estimated from the phase of the shear vector measured during the spatial surveys. Estimates of the length scale of the waves range from 500 to 1000 km, and the frequency is approximately 1.1f. The behavior of the phase is found to be consistent with a model of narrow-band inertial waves with vertical structure such that there is a zero crossing in velocity at the base of the mixed layer (40-60 m).

  4. Acoustic doppler methods for remote measurements of ocean flows - a review

    Joseph, A.

    The evolution of acoustic doppler methods for remote measurements of ocean flows has been briefly reviewed in historical perspective. Both Eulerian and profiling methods have been discussed. Although the first acoustic Doppler current meter has been...

  5. Acoustic Doppler current profiling from the JGOFS Arabian sea cruises aboard the RV T.G. Thompson

    Kim, Hyun-Sook; Flagg, C.N.; Shi, Yan

    1996-06-01

    Acoustic Doppler current profiler (ADCP) data is part of the core data for the U.S. JGOFS Arabian Sea project, along with hydrographic and nutrient data. Seventeen cruises are scheduled to take place between September 1994 and January 1996 on the R/V T.G. Thompson. They are numbered consecutively from the ship`s commissioning with the first JGOFS cruise designated TN039. Table 1 lists start and end dates of each cruise with its mission. All but the first cruise have been or will be staged from Muscat, Oman. Each cruise is scheduled for a duration of between two weeks and one month. Seven of the cruises, referred to as process cruises, follow a standard cruise track, taking hydrographic, chemical and biological measurements. The rest of the cruises, which take place generally within the standard cruise region defined by a set track, are for the deployment and recovery of moored equipments and towing of a SeaSoar. ADCP data are collected using an autonomous data acquisition system developed for ship-of-opportunity cruises, named the AutoADCP system. The system is an extension of RD instrument`s DAS version 2.48 using enhancements made possible with {open_quotes}user-exit{close_quotes} programs. It makes it possible to collect ADCP data without the constant monitoring usually necessary and insures constant data coverage and uniform data quality.

  6. Comparison of bottom-track to global positioning system referenced discharges measured using an acoustic Doppler current profiler

    Wagner, C.R.; Mueller, D.S.

    2011-01-01

    A negative bias in discharge measurements made with an acoustic Doppler current profiler (ADCP) can be caused by the movement of sediment on or near the streambed. The integration of a global positioning system (GPS) to track the movement of the ADCP can be used to avoid the systematic negative bias associated with a moving streambed. More than 500 discharge transects from 63 discharge measurements with GPS data were collected at sites throughout the US, Canada, and New Zealand with no moving bed to compare GPS and bottom-track-referenced discharges. Although the data indicated some statistical bias depending on site conditions and type of GPS data used, these biases were typically about 0.5% or less. An assessment of differential correction sources was limited by a lack of data collected in a range of different correction sources and different GPS receivers at the same sites. Despite this limitation, the data indicate that the use of Wide Area Augmentation System (WAAS) corrected positional data is acceptable for discharge measurements using GGA as the boat-velocity reference. The discharge data based on GPS-referenced boat velocities from the VTG data string, which does not require differential correction, were comparable to the discharges based on GPS-referenced boat velocities from the differentially-corrected GGA data string. Spatial variability of measure discharges referenced to GGA, VTG and bottom-tracking is higher near the channel banks. The spatial variability of VTG-referenced discharges is correlated with the spatial distribution of maximum Horizontal Dilution of Precision (HDOP) values and the spatial variability of GGA-referenced discharges is correlated with proximity to channel banks. ?? 2011 Published by Elsevier B.V.

  7. The Acoustic Doppler Current Profiler (adcp) as a Tool for Ocean Exploration

    Rossby, H. T.; Flagg, C. N.; Ortner, P. B.

    2010-12-01

    Although the ADCP has been around for three decades it remains somewhat underappreciated for its excellent exploratory potential in several areas. First and perhaps foremost because oceanographers have always been handicapped in their ability to resolve horizontal patterns below the surface, the ADCP opens up a powerful and very cost-effective window into the ocean water column to explore the meso- and submesoscale velocity field at very high resolution. This is particularly true when ADCP data are collected from just a single instrument mounted on a vessel operating repeatedly over an extended period of time in an area or along a route. The ADCP greatly expands upon hydrographic and XBT information by directly measuring the velocity field accurately without any assumptions about geostrophy or the velocity of reference layers. Second, vessels in transit can characterize currents and eddy activities across contrasting oceanic regimes and highlight their relation to the steering role of bottom topography. Third, even though the ADCP is a single frequency device the backscatter signal recorded by the ADCP is showing considerable skill in revealing space-time patterns of biomass variability. Here, through data we have taken over the past ten years, we survey the ADCP’s future as a tool of exploration across several dimensions: space, time, and parameter (physics and biology). Today, thanks to the ADCP we have a far more accurate picture of the velocity and vorticity structure of fronts and eddies. At the surface a front is simply a transition between different water masses, but the actual transition will often consist a water-mass and potential vorticity jump on a significantly smaller scale within the frontal feature. The same applies to the boundaries of rings and lenses. Commercial vessels equipped with ADCPs operating on a repeat schedule can document underlying patterns that single transects or cruises cannot detect due to inherent eddy activity. Newly

  8. Observation of wind forced circulation on the continental shelf off Point Sur, California from a self-contained acoustic doppler current profiler.

    Abbott, Christopher Lynn

    1991-01-01

    Approved for public release; distribution is unlimited To study the current structure of the California Current as it manifests itself on the continental shelf a subsurface mooring, P1, was anchored 5km west of Point Sur at 36(o), 17' N, 121(o), 59' W from 28 February through 11 May 1990. the P1 mooring, placed on the 84 m isobaths, consisted of a self-contained acoustic Doppler current profiler (SC-ADCP) housed in a syntactic foam sphere and secured to an anchor. The mooring geometry pl...

  9. Inverse Doppler Effects in Broadband Acoustic Metamaterials.

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

    2016-01-01

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

  10. Bathymetric surveys of Morse and Geist Reservoirs in central Indiana made with acoustic Doppler current profiler and global positioning system technology, 1996

    Wilson, J.T.; Morlock, S.E.; Baker, N.T.

    1997-01-01

    Acoustic Doppler current profiler, global positioning system, and geographic information system technology were used to map the bathymetry of Morse and Geist Reservoirs, two artificial lakes used for public water supply in central Indiana. The project was a pilot study to evaluate the use of the technologies for bathymetric surveys. Bathymetric surveys were last conducted in 1978 on Morse Reservoir and in 1980 on Geist Reservoir; those surveys were done with conventional methods using networks of fathometer transects. The 1996 bathymetric surveys produced updated estimates of reservoir volumes that will serve as base-line data for future estimates of storage capacity and sedimentation rates.An acoustic Doppler current profiler and global positioning system receiver were used to collect water-depth and position data from April 1996 through October 1996. All water-depth and position data were imported to a geographic information system to create a data base. The geographic information system then was used to generate water-depth contour maps and to compute the volumes for each reservoir.The computed volume of Morse Reservoir was 22,820 acre-feet (7.44 billion gallons), with a surface area of 1,484 acres. The computed volume of Geist Reservoir was 19,280 acre-feet (6.29 billion gallons), with a surface area of 1,848 acres. The computed 1996 reservoir volumes are less than the design volumes and indicate that sedimentation has occurred in both reservoirs. Cross sections were constructed from the computer-generated surfaces for 1996 and compared to the fathometer profiles from the 1978 and 1980 surveys; analysis of these cross sections also indicates that some sedimentation has occurred in both reservoirs.The acoustic Doppler current profiler, global positioning system, and geographic information system technologies described in this report produced bathymetric maps and volume estimates more efficiently and with comparable or greater resolution than conventional

  11. Acoustic Doppler Current Profiler observations in the southern Caspian Sea: shelf currents and flow field off Freidoonkenar Bay, Iran

    P. Ghaffari

    2009-12-01

    Full Text Available The results of offshore bottom-mounted ADCP measurements and wind records carried out from August to September 2003 in the coastal waters off Freidoonkenar Bay (FB in the south Caspian Sea (CS are examined in order to characterize the shelf motion, the steady current field and to determine the main driving forces of currents on the study area. Owing to closed basin and absence of the astronomical tide, the atmospheric forcing plays an important role in the flow field of the CS. The lasting regular sea breeze system is present almost throughout the year that performs motive force in diurnal and semi-diurnal bands similar to tides in other regions. In general, current field in the continental shelf could be separated into two distinguishable schemes, which in cross-shelf direction is dominated by high frequencies (1 cpd and higher frequencies, and in along-shelf orientation mostly proportional to lower frequencies in synoptic weather bands. Long-period wave currents, whose velocities are much greater than those of direct wind-induced currents, are dominating the current field in the continental shelf off FB. The propagation of the latter could be described in terms of shore-controlled waves that are remotely generated and travel across the shelf in the southern CS. It has also been shown that long term displacements in this area follow the classic cyclonic, circulation pattern in the southern CS.

  12. Acoustic Doppler Current Profiler observations in the southern Caspian Sea: shelf currents and flow field off Feridoonkenar Bay, Iran

    P. Ghaffari

    2010-07-01

    Full Text Available The results of offshore bottom-mounted ADCP measurements and wind records carried out from August to September 2003 in the coastal waters off Feridoon-kenar Bay (FB in the south Caspian Sea (CS are examined in order to characterize the shelf motion, the steady current field and to determine the main driving forces of currents on the study area. Owing to closed basin and absence of the astronomical tide, the atmospheric forcing plays an important role in the flow field of the CS. The lasting regular sea breeze system is present almost throughout the year. This system performs the forcing in diurnal and semi-diurnal bands similar to tides in other regions. In general, current field in the continental shelf could be separated into two distinguishable schemes, which in cross-shelf direction is dominated by high frequencies (1 cpd and higher frequencies, and in along-shelf orientation mostly proportional to lower frequencies in synoptic weather bands. Long-period wave currents, whose velocities are much greater than those of direct wind-induced currents, dominates the current field in the continental shelf off FB. The propagation of the latter could be described in terms of shore-controlled waves that are remotely generated and travel across the shelf in the southern CS. It has also been shown that long term displacements in this area follow the classic cyclonic, circulation pattern in the southern CS.

  13. Correcting acoustic Doppler current profiler discharge measurement bias from moving-bed conditions without global positioning during the 2004 Glen Canyon Dam controlled flood on the Colorado River

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

    2007-01-01

    Discharge measurements were made by acoustic Doppler current profiler at two locations on the Colorado River during the 2004 controlled flood from Glen Canyon Dam, Arizona. Measurement hardware and software have constantly improved from the 1980s such that discharge measurements by acoustic profiling instruments are now routinely made over a wide range of hydrologic conditions. However, measurements made with instruments deployed from moving boats require reliable boat velocity data for accurate measurements of discharge. This is normally accomplished by using special acoustic bottom track pings that sense instrument motion over bottom. While this method is suitable for most conditions, high current flows that produce downstream bed sediment movement create a condition known as moving bed that will bias velocities and discharge to lower than actual values. When this situation exists, one solution is to determine boat velocity with satellite positioning information. Another solution is to use a lower frequency instrument. Discharge measurements made during the 2004 Glen Canyon controlled flood were subject to moving-bed conditions and frequent loss of bottom track. Due to site conditions and equipment availability, the measurements were conducted without benefit of external positioning information or lower frequency instruments. This paper documents and evaluates several techniques used to correct the resulting underestimated discharge measurements. One technique produces discharge values in good agreement with estimates from numerical model and measured hydrographs during the flood. ?? 2007, by the American Society of Limnology and Oceanography, Inc.

  14. The diel vertical migration of sound scatterers observed by an acoustic Doppler current profiler in the Luzon Strait from July 2009 to April 2011

    YANG Chenghao; LIAO Guanghong; YUAN Yaochu; CHEN Hong; ZHU Xiaohua

    2013-01-01

    Acoustic Doppler current profiler (ADCP) receives echoes from sound scatterers, then their speed is calcu-lated by the Doppler effect. In the open ocean, most of these backscatterers are from the plankton. The sound scatterers descend down to depth at around dawn, their mean speed is 2.9 cm/s, then they ascend up to the surface layer at around dusk with a mean speed of 2.1 cm/s, in the Luzon Strait. The descending speed is faster, which suggests that this zooplankton population may accelerate its downward migration under the action of the gravity. The vertical distribution of a mean volume backscattering strength (MVB-S) in the nighttime has two peaks, which locate near the upper and lower boundary layers of halocline, respectively. However, the backscatterers only aggregate near the surface layer in the daytime. The diel ver-tical migration (DVM) of sound scatterers has several characteristic patterns, it is stronger in summer, but weaker in winter, and the maximum peak occurs in September. The DVM occurrence is synchronous with the seawater temperature increasing at around dawn and dusk, it may affect the ocean mixing and water stratification.

  15. Year-long measurements of flow-through the dover strait by HF radar and acoustic doppler current profilers (ADCP)

    Prandle, D.

    1993-01-01

    Contaminants from the Channel flow through the Dover Strait into the North Sea where they represent a significant fraction of the enhanced concentrations observed along the continental coast. Despite numerous previous investigations, the magnitude of this net flow and its dependency on various forcing factors remain uncertain. The new UK H.F. Radar system, OSCR (Ocean Surface Current Radar) developed for measuring nearshore surface currents offers a clear opportunity of establishing the magni...

  16. Experimental Observation of Reversed Doppler Effects in Acoustic Metamaterials

    Zhai, Shilong; Zhao, Xiaopeng; Liu, Song; Luo, Chunrong

    2015-01-01

    This paper reports an experimental observation of broadband reversed Doppler effects using an acoustic metamaterial with seven flute-like double-meta-molecule clusters. Simulations and experiments verify that this locally resonant acoustic metamaterial with simultaneous negative elastic modulus and mass density can realize negative refraction in a broad frequency range. The constructed metamaterial exhibits broadband reversed Doppler effects. The frequency shift increases continuously as the ...

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

    McCaffrey, Katherine

    Turbulence is inherently chaotic and unsteady, so observing it and modeling it are no easy tasks. The ocean's sheer size makes it even more difficult to observe, and its unpredictable and ever-changing forcings introduce additional complexities. Turbulence in the oceans ranges from basin scale to the scale of the molecular viscosity. The method of energy transfer between scales is, however, an area of active research, so observations of the ocean at all scales are crucial to understanding the basic dynamics of its motions. In this collection of work, I use a variety of datasets to characterize a wide range of scales of turbulence, including observations from multiple instruments and from models with different governing equations. I analyzed the largest scales of the turbulent range using the global salinity data of the Argo profiling float network. Taking advantage of the scattered and discontinuous nature of this dataset, the second-order structure function was calculated down to 2000m depth, and shown to be useful for predicting spectral slopes. Results showed structure function slopes of 2/3 at small scales, and 0 at large scales, which corresponds with spectral slopes of -5/3 at small scales, and -1 at large scales. Using acoustic Doppler velocity measurements, I characterized the meter- to kilometer-scale turbulence at a potential tidal energy site in the Puget Sound, WA. Acoustic Doppler current profiler (ADCP) and acoustic Doppler velocimeter (ADV) observations provided the data for an analysis that includes coherence, anisotropy, and intermittency. In order to more simply describe these features, a parameterization was done with four turbulence metrics, and the anisotropy magnitude, introduced here, was shown to most closely capture the coherent events. Then, using both the NREL TurbSim stochastic turbulence generator and the NCAR large-eddy simulation (LES) model, I calculated turbulence statistics to validate the accuracy of these methods in reproducing

  18. Ocean Current Velocity Moored Time-Series Records, collected from moored Acoustic Doppler Current Profilers (ADCP) during 2010 and 2011 in Vieques Sound and Virgin Passage (NODC Accession 0088063)

    National Oceanic and Atmospheric Administration, Department of Commerce — Nortek 600kHz Aquadopp acoustic current profilers were deployed between March 2010 and April 2011 on shallow water moorings located in Vieques Sound, Puerto Rico,...

  19. Ocean Current Velocity Moored Time-Series Records collected from moored Acoustic Doppler Current Profilers near Grammanik Bank Spawning Aggregation Site (SPAG) and Frenchcap Cay, United States Virgin Islands, from April 24, 2011 to September 25, 2011 (NODC Accession 0088064)

    National Oceanic and Atmospheric Administration, Department of Commerce — Nortek 600kHz Aquadopp acoustic current profilers were deployed between April 2011 and September 2011 on shallow water moorings located on the coastal shelf south...

  20. Ocean Current Velocity Moored Time-Series Records, collected from moored Acoustic Doppler Current Profilers (ADCP) during 2011 near Grammanik Bank SPAG and Frenchcap Cay, USVI (NODC Accession 0088064)

    National Oceanic and Atmospheric Administration, Department of Commerce — Nortek 600kHz Aquadopp acoustic current profilers were deployed between April 2011 and September 2011 on shallow water moorings located on the coastal shelf south...

  1. HF Doppler observations of acoustic waves excited by the earthquake

    Ichinose, T.; Takagi, K.; Tanaka, T.; Okuzawa, T.; Shibata, T.; Sato, Y.; Nagasawa, C.; Ogawa, T.

    1985-01-01

    Ionospheric disturbances caused by the earthquake of a relatively small and large epicentral distance have been detected by a network of HF-Doppler sounders in central Japan and Kyoto station, respectively. The HF-Doppler data of a small epicentral distance, together with the seismic data, have been used to formulate a mechanism whereby ionospheric disturbances are produced by the Urakawa-Oki earthquake in Japan. Comparison of the dynamic spectra of these data has revealed experimentally that the atmosphere acts as a low-pass filter for upward-propagating acoustic waves. By surveying the earthquakes for which the magnitude M is larger than 6.0, researchers found the ionospheric effect in 16 cases of 82 seismic events. As almost all these effects have occurred in the daytime, it is considered that it may result from the filtering effect of the upward-propagating acoustic waves.

  2. A New Underwater Acoustic Navigation Method Based on the Doppler Principle

    Jinsong Tang; Kun Fang; Sen Zhang

    2013-01-01

    In this paper, a new underwater acoustic navigation method is proposed, which is named from Doppler Acoustic Omnirange Beacon (DAOB). It is borrowed from the idea of Doppler VHF Omnirange (DVOR) and based on the Doppler principle. The cause of Doppler effect in the received signal is the motion or position change of one or two sources. The effect of multipath is analyzed, and an improved signal form is presented to solve the rigorous multipath environment underwater. Some simulation is presen...

  3. Use of Acoustic Doppler Instruments for Measuring Discharge in Streams with Appreciable Sediment Transport

    Mueller, D.S.

    2002-01-01

    The use of Acoustic Doppler current profilers (ADCP) for measuring discharge in streams with sediment transport was discussed. The studies show that the acoustic frequency of an ADCP in combination with the sediment transport characteristics in a river causes the ADCP bottom-tracking algorithms to detect a moving bottom. A moving bottom causes bottom-tracking-referenced water velocities and discharges to be biased low. The results also show that the use of differential global positioning system (DGPS) data allows accurate measurement of water velocities and discharges in such cases.

  4. Current-induced spin wave Doppler shift

    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).

  5. NODC Standard Product: World Ocean Circulation Program (WOCE) Global Data, Version 2: Acoustic doppler current profilers data on CD-ROM (NODC Accession 0000312)

    National Oceanic and Atmospheric Administration, Department of Commerce — World-Wide shipboard current data were collected from ADCP casts from the ALPHA HELIX and other platforms as part of World Ocean Circulation Experiment (WOCE). Data...

  6. CRED Acoustic Doppler Profiler (ADP); NWHI, MID; Long: -177.42181, Lat: 28.21826 (WGS84); Sensor Depth: 1.83m; Data Range: 20080926-20090321.

    National Oceanic and Atmospheric Administration, Department of Commerce — Data from Coral Reef Ecosystem Division (CRED), NOAA Pacific Island Fisheries Science Center Acoustic Doppler Profilers (ADP) provide a time series of water current...

  7. CRED Acoustic Doppler Profiler (ADP); AMSM, ROS; Long: -168.15481, Lat: -14.53510 (WGS84); Sensor Depth: 7.01m; Data Range: 20080311-20080314.

    National Oceanic and Atmospheric Administration, Department of Commerce — Data from Coral Reef Ecosystem Division (CRED), NOAA Pacific Island Fisheries Science Center Acoustic Doppler Profilers (ADP) provide a time series of water current...

  8. Field evaluation of boat-mounted acoustic Doppler instruments used to measure streamflow

    Mueller, D.S.

    2003-01-01

    The use of instruments based on the Doppler principle for measuring water velocity and computing discharge is common within the U.S. Geological Survey (USGS). The instruments and software have changed appreciably during the last 5 years; therefore, the USGS has begun field validation of the instruments used to make discharge measurements from a moving boat. Instruments manufactured by SonTek/YSI and RD Instruments, Inc. were used to collect discharge data at five different sites. One or more traditional discharge measurements were made using a Price AA current meter and standard USGS procedures concurrent with the acoustic instruments at each site. Discharges measured with the acoustic instruments were compared with discharges measured with Price AA current meters and the USGS stage-discharge rating for each site. The mean discharges measured by each acoustic instrument were within 5 percent of the Price AA-based measurement and (or) discharge from the stage-discharge rating.

  9. A New Underwater Acoustic Navigation Method Based on the Doppler Principle

    Jinsong Tang

    2013-07-01

    Full Text Available In this paper, a new underwater acoustic navigation method is proposed, which is named from Doppler Acoustic Omnirange Beacon (DAOB. It is borrowed from the idea of Doppler VHF Omnirange (DVOR and based on the Doppler principle. The cause of Doppler effect in the received signal is the motion or position change of one or two sources. The effect of multipath is analyzed, and an improved signal form is presented to solve the rigorous multipath environment underwater. Some simulation is presented to verify the performance.    

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

    Kilcher, Levi [National Renewable Energy Lab. (NREL), Golden, CO (United States); Thomson, Jim [Univ. of Washington, Seattle, WA (United States); Talbert, Joe [Univ. of Washington, Seattle, WA (United States); DeKlerk, Alex [Univ. of Washington, Seattle, WA (United States)

    2016-03-01

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

  11. Acoustic resolution photoacoustic Doppler velocimetry in blood-mimicking fluids

    Brunker, Joanna; Beard, Paul

    2016-02-01

    Photoacoustic Doppler velocimetry provides a major opportunity to overcome limitations of existing blood flow measuring methods. By enabling measurements with high spatial resolution several millimetres deep in tissue, it could probe microvascular blood flow abnormalities characteristic of many different diseases. Although previous work has demonstrated feasibility in solid phantoms, measurements in blood have proved significantly more challenging. This difficulty is commonly attributed to the requirement that the absorber spatial distribution is heterogeneous relative to the minimum detectable acoustic wavelength. By undertaking a rigorous study using blood-mimicking fluid suspensions of 3 μm absorbing microspheres, it was discovered that the perceived heterogeneity is not only limited by the intrinsic detector bandwidth; in addition, bandlimiting due to spatial averaging within the detector field-of-view also reduces perceived heterogeneity and compromises velocity measurement accuracy. These detrimental effects were found to be mitigated by high-pass filtering to select photoacoustic signal components associated with high heterogeneity. Measurement under-reading due to limited light penetration into the flow vessel was also observed. Accurate average velocity measurements were recovered using “range-gating”, which furthermore maps the cross-sectional velocity profile. These insights may help pave the way to deep-tissue non-invasive mapping of microvascular blood flow using photoacoustic methods.

  12. Doppler effect in a solid medium: Spin wave emission by a precessing domain wall drifting in spin current

    Xia, Hong; Chen, Jie; Zeng, Xiaoyan; Yan, Ming

    2016-04-01

    The Doppler effect is a fundamental physical phenomenon observed for waves propagating in vacuum or various media, commonly gaseous or liquid. Here, we report on the occurrence of a Doppler effect in a solid medium. Instead of a real object, a topological soliton, i.e., a magnetic domain wall (DW) traveling in a current-carrying ferromagnetic nanowire, plays the role of the moving wave source. The Larmor precession of the DW in an external field stimulates emission of monochromatic spin waves (SWs) during its motion, which show a significant Doppler effect, comparable to the acoustic one of a train whistle. This process involves two prominent spin-transfer-torque effects simultaneously, the current-driven DW motion and the current-induced SW Doppler shift. The latter gives rise to an interesting feature, i.e., the observed SW Doppler effect appears resulting from a stationary source and a moving observer, contrary to the laboratory frame.

  13. Reverse Doppler effect in backward spin waves scattered on acoustic waves

    A. V. Chumak; Dhagat, P.; Jander, A.; Serga, A. A.; Hillebrands, B

    2009-01-01

    We report on the observation of reverse Doppler effect in backward spin waves reflected off of surface acoustic waves. The spin waves are excited in a yttrium iron garnet (YIG) film. Simultaneously, acoustic waves are also generated. The strain induced by the acoustic waves in the magnetostrictive YIG film results in the periodic modulation of the magnetic anisotropy in the film. Thus, in effect, a travelling Bragg grating for the spin waves is produced. The backward spin waves reflecting off...

  14. Online Doppler Effect Elimination Based on Unequal Time Interval Sampling for Wayside Acoustic Bearing Fault Detecting System

    Kesai Ouyang

    2015-08-01

    Full Text Available The railway occupies a fairly important position in transportation due to its high speed and strong transportation capability. As a consequence, it is a key issue to guarantee continuous running and transportation safety of trains. Meanwhile, time consumption of the diagnosis procedure is of extreme importance for the detecting system. However, most of the current adopted techniques in the wayside acoustic defective bearing detector system (ADBD are offline strategies, which means that the signal is analyzed after the sampling process. This would result in unavoidable time latency. Besides, the acquired acoustic signal would be corrupted by the Doppler effect because of high relative speed between the train and the data acquisition system (DAS. Thus, it is difficult to effectively diagnose the bearing defects immediately. In this paper, a new strategy called online Doppler effect elimination (ODEE is proposed to remove the Doppler distortion online by the introduced unequal interval sampling scheme. The steps of proposed strategy are as follows: The essential parameters are acquired in advance. Then, the introduced unequal time interval sampling strategy is used to restore the Doppler distortion signal, and the amplitude of the signal is demodulated as well. Thus, the restored Doppler-free signal is obtained online. The proposed ODEE method has been employed in simulation analysis. Ultimately, the ODEE method is implemented in the embedded system for fault diagnosis of the train bearing. The results are in good accordance with the bearing defects, which verifies the good performance of the proposed strategy.

  15. Online Doppler Effect Elimination Based on Unequal Time Interval Sampling for Wayside Acoustic Bearing Fault Detecting System.

    Ouyang, Kesai; Lu, Siliang; Zhang, Shangbin; Zhang, Haibin; He, Qingbo; Kong, Fanrang

    2015-01-01

    The railway occupies a fairly important position in transportation due to its high speed and strong transportation capability. As a consequence, it is a key issue to guarantee continuous running and transportation safety of trains. Meanwhile, time consumption of the diagnosis procedure is of extreme importance for the detecting system. However, most of the current adopted techniques in the wayside acoustic defective bearing detector system (ADBD) are offline strategies, which means that the signal is analyzed after the sampling process. This would result in unavoidable time latency. Besides, the acquired acoustic signal would be corrupted by the Doppler effect because of high relative speed between the train and the data acquisition system (DAS). Thus, it is difficult to effectively diagnose the bearing defects immediately. In this paper, a new strategy called online Doppler effect elimination (ODEE) is proposed to remove the Doppler distortion online by the introduced unequal interval sampling scheme. The steps of proposed strategy are as follows: The essential parameters are acquired in advance. Then, the introduced unequal time interval sampling strategy is used to restore the Doppler distortion signal, and the amplitude of the signal is demodulated as well. Thus, the restored Doppler-free signal is obtained online. The proposed ODEE method has been employed in simulation analysis. Ultimately, the ODEE method is implemented in the embedded system for fault diagnosis of the train bearing. The results are in good accordance with the bearing defects, which verifies the good performance of the proposed strategy. PMID:26343657

  16. Current measurements from acoustic doppler current profilers (ADCP) in the southwest Atlantic Ocean from the World Ocean Circulation Experiment (WOCE) from 1991-01-03 to 1992-11-26 (NODC Accession 0087597)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter data from the ADCP instruments of BE/335 and BW/333 from January 3, 1991 to November 26, 1992 collected as part of the World Ocean Circulation...

  17. The Doppler Effect based acoustic source separation for a wayside train bearing monitoring system

    Zhang, Haibin; Zhang, Shangbin; He, Qingbo; Kong, Fanrang

    2016-01-01

    Wayside acoustic condition monitoring and fault diagnosis for train bearings depend on acquired acoustic signals, which consist of mixed signals from different train bearings with obvious Doppler distortion as well as background noises. This study proposes a novel scheme to overcome the difficulties, especially the multi-source problem in wayside acoustic diagnosis system. In the method, a time-frequency data fusion (TFDF) strategy is applied to weaken the Heisenberg's uncertainty limit for a signal's time-frequency distribution (TFD) of high resolution. Due to the Doppler Effect, the signals from different bearings have different time centers even with the same frequency. A Doppler feature matching search (DFMS) algorithm is then put forward to locate the time centers of different bearings in the TFD spectrogram. With the determined time centers, time-frequency filters (TFF) are designed with thresholds to separate the acoustic signals in the time-frequency domain. Then the inverse STFT (ISTFT) is taken and the signals are recovered and filtered aiming at each sound source. Subsequently, a dynamical resampling method is utilized to remove the Doppler Effect. Finally, accurate diagnosis for train bearing faults can be achieved by applying conventional spectrum analysis techniques to the resampled data. The performance of the proposed method is verified by both simulated and experimental cases. It shows that it is effective to detect and diagnose multiple defective bearings even though they produce multi-source acoustic signals.

  18. A Comparison of the Electromagnetic and Acoustic Doppler Effects Using Geometrical Diagrams

    Bokor, Nandor

    2009-01-01

    Students often find the difference in the electromagnetic and the acoustic Doppler formulae somewhat puzzling. As is shown below, geometrical diagrams and the concept of "event"--a point in spacetime having coordinates (x,y,z,t)--can be a useful and simple way to explain the physical background behind the fundamental differences between the two…

  19. Evaluation of performance of Son Tek Argonaut acoustic doppler velocity log in tow tank and sea

    Joseph, A.; Madhan, R.; Mascarenhas, A.A.M.Q.; Desai, R.G.P.; VijayKumar, K.; Dias, M.; Tengali, S.; Methar, A.

    Performance of a 500-kHz, 3-beam downward-looking Sontex Argonaut acoustic Doppler velocity log (DVL) based on measurements at tow-tank and sea is addressed. Its accuracy and linearity under tow-tank measurements were largely scattered...

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

    Pinkel, Robert; Smith, Jerome A.

    2004-11-01

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

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

    Tran MinhHai

    2016-01-01

    Full Text Available 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.

  2. Current-induced spin-wave Doppler shift.

    Vlaminck, Vincent; Bailleul, Matthieu

    2008-10-17

    Spin transfer appears to be a promising tool for improving spintronics devices. Experiments that quantitatively access the magnitude of the spin transfer are required for a fundamental understanding of this phenomenon. By inductively measuring spin waves propagating along a permalloy strip subjected to a large electrical current, we observed a current-induced spin wave Doppler shift that we relate to the adiabatic spin transfer torque. Because spin waves provide a well-defined system for performing spin transfer, we anticipate that they could be used as an accurate probe of spin-polarized transport in various itinerant ferromagnets. PMID:18927387

  3. Prospects for in vivo blood velocimetry using acoustic resolution photoacoustic Doppler

    Brunker, J.; Beard, P.

    2016-03-01

    Acoustic resolution photoacoustic Doppler flowmetry (AR-PAF) is a technique that has the potential to overcome the spatial resolution and depth penetration limitations of current blood flow measuring methods. Previous work has shown the potential of the technique using blood-mimicking phantoms, but it has proved difficult to make accurate measurements in blood, and thus in vivo application has not yet been possible. One explanation for this difficulty is that whole blood is insufficiently heterogeneous. Through experimental measurements in red blood cell suspensions of different concentrations, as well as in whole blood, we provide new insight and evidence that refutes this assertion. We show that the velocity measurement accuracy is influenced by bandlimiting not only due to the detector frequency response, but also due to spatial averaging of absorbers within the detector field-of-view. In addition, there is a detrimental effect of limited light penetration, but this can be mitigated by selecting less attenuated wavelengths of light, and also by employing range-gating signal processing. By careful choice of these parameters as well as the detector centre frequency, bandwidth and field-of-view, it is possible to make AR-PAF measurements in whole blood using transducers with bandwidths in the tens of MHz range. These findings have profound implications for the prospects of making deep tissue measurements of blood flow relevant to the study of microcirculatory abnormalities associated with cancer, diabetes, atherosclerosis and other conditions.

  4. Acoustic Doppler current profiling from the JGOFS Arabian Sea cruises aboard the RV T.G. THOMPSON: TN043, January 8, 1995--February 4, 1995; TN044, February 8, 1995--February 25, 1995; TN045, March 14, 1995--April 10, 1995; TN046, April 14, 1995--April 29, 1995

    Flagg, C.N.; Kim, H.S.; Shi, Y.

    1995-09-01

    Acoustic Doppler current profiler (ADCP) data from the R/V T.G. THOMPSON is part of the core data for the US JGOFS Arabian Sea project along with hydrographic and nutrient data. Seventeen cruises on the THOMPSON are scheduled to take place between September 1994 and January 1996. This is the second in a series of data reports covering the ADCP data from the Arabian Sea JGOFS cruises TNO43 through TNO46. ADCP data are being collected on all the JGOFS Arabian Sea cruises using an autonomous data acquisition system developed for ship-of-opportunity cruises. This system, referred to as the AutoADCP, makes it possible to collect the ADCP data without the constant monitoring usually necessary and assures constant data coverage and uniform data quality. This data report presents ADCP results from the second group of four JGOFS cruises, TNO43 through TNO46, concentrating on the data collection and processing methods. The ADCP data itself reside in a CODAS data base at Brookhaven National Laboratory and is generally available to JGOFS investigators through contact with the authors. The CODAS data base and associated ADCP processing software were developed over a number of years by Eric Firing and his group at the University of Hawaii. The CODAS software is shareware available for PC`s or Unix computers and is the single most widely used ADCP processing program for ship mounted units.

  5. Scanning Laser Doppler Vibrometry Application to Artworks: New Acoustic and Mechanical Exciters for Structural Diagnostics

    Agnani, A.; Esposito, E.

    After first attempts some years ago, the scanning laser Doppler vibrometer has become an effective way of diagnosing different types of artworks; successful applications regard frescoes, icons, mosaics, ceramic artefacts and wood inlays. Also application to historical bridges has been successfully developed and a recently approved European Commission project will see the employment of scanning laser Doppler Vibrometry (SLDV) for the dynamical characterization of ancient buildings. However, a critical issue consists in the adequate excitation of the structure under test. Moreover different types of defects and different kinds of artworks require different types of excitation, so this topic needs a deep consideration. In this work we will present two new types of exciters developed at our Department, namely an acoustic exciter and a mechanical one. Acoustic exciters allow remote non-invasive loading but are limited in the lower frequency range and in the amount of vibrational energy input into the structure. The proposed automatic tapping device based on a commercial impact hammer overcomes these problems. Also another acoustic exciter, a HyperSonic Sound (HSS) source has been evaluated, showing interesting features as regards sound radiation.

  6. Three dimensional measurements of Geodesic Acoustic Mode with correlation Doppler reflectometers

    Correlation Doppler reflectometers have been newly developed in the HL-2A Tokamak. Owing to the flexibility of the diagnostic arrangements, the multi-channel systems allow us to study, simultaneously, the radial properties of edge turbulence and its long-range correlation in both the poloidal and toroidal direction. With these reflectometers, three-dimensional spatial structure of Geodesic Acoustic Mode (GAM) is surveyed, including the symmetric feature of Er fluctuations in both poloidal and toroidal directions, and the radial propagation of GAMs. The bi-coherence analysis for the Er fluctuations suggests that the three-wave nonlinear interaction could be the mechanism for the generation of GAM. The temporal evolution of GAM during the plasma density modulation experiments has been studied. The results show that the collisional damping plays a role in suppressing the GAM magnitudes, and hence, weakening the regulating effects of GAM on ambient turbulence. Three dimensional correlation Doppler measurements of GAM activity demonstrate that the newly developed correlation Doppler reflectometers in HL-2A are powerful tools for edge turbulence studies with high reliability. A shorter version of this contribution is due to be published in PoS at: ''1st EPS conference on Plasma Diagnostics''

  7. Theory and signal processing of acoustic correlation techniques for current velocity measurement

    ZHU Weiqing; FENG Lei; WANG Changhong; WANG Yuling; QIU Wei

    2008-01-01

    A theoretical model and signal processing of acoustic correlation measurements to estimate current velocity are discussed. The sonar space-time correlation function of vol-ume reverberations within Fraunhofer zone is derived. The function, which is in exponential forms, is the theoretical model of acoustic correlation measurements. The characteristics of the correlation values around the maximum of the amplitude of the correlation function, where most information about current velocity is contained, are primarily analyzed. Localized Least Mean Squares (LLMS) criterion is put forward for velocity estimation. Sequential Quadratic Programming (SQP) method is adopted as the optimization method. So the systematic sig-nal processing method of acoustic correlation techniques for current velocity measurement is established. A prototype acoustic correlation current profiler (ACCP) underwent several sea trials, the results show that theoretical model approximately coincides with experimental re-sults. Current profiles including the speed and direction from ACCP are compared with those from acoustic Doppler current profiler (ADCP). The current profiles by both instruments agree reasonably well. Also, the standard deviation of velocity measurement by ACCP is statistically calculated and it is a little larger than predicted value.

  8. ALOHA Cabled Observatory (ACO): Acoustic Doppler Current Profiler (ADCP): Temperature

    National Oceanic and Atmospheric Administration, Department of Commerce — The University of Hawaii's ALOHA ("A Long-term Oligotrophic Habitat Assessment") Cabled Observatory (ACO) is located 100 km north of the island of Oahu, Hawaii (22...

  9. ALOHA Cabled Observatory (ACO): Acoustic Doppler Current Profiler (ADCP): Velocity

    National Oceanic and Atmospheric Administration, Department of Commerce — The University of Hawaii's ALOHA ("A Long-term Oligotrophic Habitat Assessment") Cabled Observatory (ACO) is located 100 km north of the island of Oahu, Hawaii (22...

  10. Linking water surface roughness to velocity patterns using terrestrial laser scanning and acoustic doppler velocimetry

    Heritage, George; Milan, David; Entwistle, Neil

    2010-05-01

    There are well established links between water surface characteristics and hydraulics. Biotope identification is currently an important part of the River Habitat Survey in England and Wales. Their differentiation is based upon recognition of a family of flow features exhibited on the water surface. Variability in this water surface ‘roughness' is dependent upon the interaction of flow with boundary roughness and flow depth. Past research that has attempted to differentiate biotopes based upon differences in Froude number (Fr) and Reynolds number (Re), however this linkage has only been limited to local analysis between flow velocity, depth and roughness. Milan et al. (2010) have recently demonstrated that terrestrial laser scanning (TLS) can be applied to produce fully quantitative maps of hydraulic habitat, based upon defined water surface roughness delimeters. However the nature of the linkages between water surface roughness, flow velocity and depth are still poorly understood, particularly at the reach-scale. This study attempts to provide a full spatial picture of the links between water surface roughness, flow depth and velocity. A Sontek Acoustic Doppler Velocity Profiler (ADVP) was used to provide detailed information on vertical velocity and water depth for a 300 m reach of the gravel-bed River Wharfe, Yorkshire, UK. Simultaneous to the ADVP measurements, a Riegl LMS-Z210 TLS was used to take a series of first return scans of the water surface. Categorisation of the point cloud elevation data for the water surface was achieved through the allocation of moving window standard deviation values to a regular grid, thus defining water surface roughness. The ADVP data demonstrate gross reach-scale variation in velocity and depth linked to bedforms, and more localised spatial and temporal variation within biotope units. The ADVP data was used to produce reach-scale maps of Fr and Re. The extent to which water surface roughness defined biotopes mapped onto these

  11. Particle Filter Based Fault-tolerant ROV Navigation using Hydro-acoustic Position and Doppler Velocity Measurements

    Zhao, Bo; Blanke, Mogens; Skjetne, Roger

    2012-01-01

    This paper presents a fault tolerant navigation system for a remotely operated vehicle (ROV). The navigation system uses hydro-acoustic position reference (HPR) and Doppler velocity log (DVL) measurements to achieve an integrated navigation. The fault tolerant functionality is based on a modied p...

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

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

    2015-09-01

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

  13. Estimating discharge using multi-level velocity data from acoustic doppler instruments

    Poulsen, Jane Bang; Rasmussen, Keld Rømer; Ovesen, Niels Bering

    ADCP-data have been collected for different stage-values. For each stage many-pull traverses (>20) have been combined in order to produce reliable high-density stream velocity profiles across the stream. Currently, the different sets of velocity data are being analyzed in order to investigate how well...... the discharge may be predicted from the in situ Dopplers. The poster will present the field-set up and the results of the data analysis....

  14. Relative contributions of sand and gravel bedload transport to acoustic Doppler bedload- velocity magnitudes in the Trinity River, California

    Gaeuman, D.; Pittman, S.

    2007-12-01

    Apparent bedload velocities measured using the bottom-track feature of acoustic Doppler current profilers (ADCPs) have received attention over the past few years as potential surrogate technique for estimating bedload transport rates and for investigating bedload dynamics. This poster reports findings from perhaps the first use of ADCP bedload velocity measurements in an applied sediment monitoring program. Sediment transport data reported here were collected under the auspices of the Trinity River Restoration Program as part of an intensive sediment monitoring effort to assess the effects of the 2006 flow release in the Trinity River of Northern California. A 1200-kHz ADCP was deployed for a subset of bedload samples collected during the release to evaluate whether acoustic bedload velocities can be used to aid interpolation between less-frequent physical samples. Paired conventional bedload samples and acoustic bedload velocity samples supplemented by underwater video showed that the instrument used in this study is sensitive primarily to the motion of sand-sized particles at the bed, but comparatively insensitive to the motion of gravel- and cobble-sized particles. High bed velocities were measured at times and in locations where sand transport rates at the bed were high, as determined by both physical samples and video. Low bed velocities were measured where both the video and bedload samples indicated that little or no bedload was being transported, irrespective of the persistence of fast-moving sand particles in the near-bed water column. To the extent that suspended or saltating particles influence the bottom- track signal, they are near enough to the bed to be captured in the physical sampler. Thus, contamination of the bottom-track signal by suspended particles (commonly referred to as water bias) is not a significant problem with this instrument in streams with low to moderate suspended sediment concentrations. These results demonstrate that acoustic

  15. Laser-Doppler acoustic probing of granular media with in-depth property gradient and varying pore pressures

    Non-contacting ultrasonic techniques recently proved to be efficient in the physical modeling of seismic-wave propagation at various application scales, as for instance in the context of geological analogue and seismic modeling. An innovative experimental set-up is proposed here to perform laser-Doppler acoustic probing of unconsolidated granular media with varying pore pressures. The preliminary experiments presented here provide reproducible results and exploitable data, thus validating both the proposed medium preparation and pressure gradient generation procedure.

  16. Applicability of acoustic Doppler devices for flow velocity measurements and discharge estimation in flows with sediment transport

    Nord, Guillaume; F. Gallart; Gratiot, N.; Soler, M.; Reid, Ian; Vachtman, Dina; Latron, Jerome; Martín-Vide, J. P.; Laronne, J. B.

    2014-01-01

    Acoustic Doppler devices (Unidata Starflow) have been deployed for velocity measurements and discharge estimates in five contrasted open-channel flow environments, with particular attention given to the influence of sediment transport on instrument performance. The analysis is based on both field observations and flume experiments. These confirm the ability of the Starflow to provide reliable discharge time-series, but point out its limitations when sediment is being transported. (i) After ca...

  17. Use of 'velocity projection' to estimate the variation of sea-surface height from HF Doppler radar current measurements

    Marmorino, G. O.; Shen, C. Y.; Evans, T. E.; Lindemann, G. J.; Hallock, Z. R.; Shay, L. K.

    2004-02-01

    The technique of 'velocity projection' (J. Geophys. Res. 106 (2001) 6973) is used to estimate the sea-surface height field and its change over time from measurements of surface velocity made using a shore-based HF Doppler radar over a 30×30-km region of the continental shelf located near the mouth of the Chesapeake Bay (USA). Projected current profiles are compared with measured currents from an array of acoustic Doppler current profilers, and the consistency and sensitivity of the projections to model assumptions are also examined. Using projected values of the local surface slope, a model sea-surface η( x, y) is least-squares fit over the study region at each measurement time. The error associated with these fits provides an internal check on the validity of the projection results. The slope of the model sea-surface shows a set-up toward the mouth of the Chesapeake Bay during downwelling-favorable winds and a counterclockwise rotation over the tidal cycle that is consistent with linear, shallow-water dynamics. A time series of sea-level difference extracted from the η maps shows a dominant M 2 tidal signal that compares well with measurements of bottom pressure made at two moorings. With proper attention to limits of applicability, such projection-based sea-surface slope fields (as well as other projection results) may be useful in diagnostic calculations or as nowcasts for use with prognostic models.

  18. Active control of passive acoustic fields: passive synthetic aperture/Doppler beamforming with data from an autonomous vehicle.

    D'Spain, Gerald L; Terrill, Eric; Chadwell, C David; Smith, Jerome A; Lynch, Stephen D

    2006-12-01

    The maneuverability of autonomous underwater vehicles (AUVs) equipped with hull-mounted arrays provides the opportunity to actively modify received acoustic fields to optimize extraction of information. This paper uses ocean acoustic data collected by an AUV-mounted two-dimensional hydrophone array, with overall dimension one-tenth wavelength at 200-500 Hz, to demonstrate aspects of this control through vehicle motion. Source localization is performed using Doppler shifts measured at a set of receiver velocities by both single elements and a physical array. Results show that a source in the presence of a 10-dB higher-level interferer having exactly the same frequency content (as measured by a stationary receiver) is properly localized and that white-noise-constrained adaptive beamforming applied to the physical aperture data in combination with Doppler beamforming provides greater spatial resolution than physical-aperture-alone beamforming and significantly lower sidelobes than single element Doppler beamforming. A new broadband beamformer that adjusts for variations in vehicle velocity on a sample by sample basis is demonstrated with data collected during a high-acceleration maneuver. The importance of including the cost of energy expenditure in determining optimal vehicle motion is demonstrated through simulation, further illustrating how the vehicle characteristics are an integral part of the signal/array processing structure. PMID:17225392

  19. Acoustic and Doppler radar detection of buried land mines using high-pressure water jets

    Denier, Robert; Herrick, Thomas J.; Mitchell, O. Robert; Summers, David A.; Saylor, Daniel R.

    1999-08-01

    The goal of the waterjet-based mine location and identification project is to find a way to use waterjets to locate and differentiate buried objects. When a buried object is struck with a high-pressure waterjets, the impact will cause characteristic vibrations in the object depending on the object's shape and composition. These vibrations will be transferred to the ground and then to the water stream that is hitting the object. Some of these vibrations will also be transferred to the air via the narrow channel the waterjet cuts in the ground. Currently the ground vibrations are detected with Doppler radar and video camera sensing, while the air vibrations are detected with a directional microphone. Data is collected via a Labview based data acquisition system. This data is then manipulated in Labview to produce the associated power spectrums. These power spectra are fed through various signal processing and recognition routines to determine the probability of there being an object present under the current test location and what that object is likely to be. Our current test area consists of a large X-Y positioning system placed over approximately a five-foot circular test area. The positioning system moves both the waterjet and the sensor package to the test location specified by the Labview control software. Currently we are able to locate buried land mine models at a distance of approximately three inches with a high degree of accuracy.

  20. Detection of geodesic acoustic mode oscillations, using multiple signal classification analysis of Doppler backscattering signal on Tore Supra

    This paper presents the first observation of geodesic acoustic modes (GAMs) on Tore Supra plasmas. Using the Doppler backscattering system, the oscillations of the plasma flow velocity, localized between r/a = 0.85 and r/a = 0.95, and with a frequency, typically around 10 kHz, have been observed at the plasma edge in numerous discharges. When the additional heating power is varied, the frequency is found to scale with Cs/R. The MUltiple SIgnal Classification (MUSIC) algorithm is employed to access the temporal evolution of the perpendicular velocity of density fluctuations. The method is presented in some detail, and is validated and compared against standard methods, such as the conventional fast Fourier transform method, using a synthetic signal. It stands out as a powerful data analysis method to follow the Doppler frequency with a high temporal resolution, which is important in order to extract the dynamics of GAMs. (paper)

  1. Detection of geodesic acoustic mode oscillations, using multiple signal classification analysis of Doppler backscattering signal on Tore Supra

    Vermare, L.; Hennequin, P.; Gürcan, Ö. D.; the Tore Supra Team

    2012-06-01

    This paper presents the first observation of geodesic acoustic modes (GAMs) on Tore Supra plasmas. Using the Doppler backscattering system, the oscillations of the plasma flow velocity, localized between r/a = 0.85 and r/a = 0.95, and with a frequency, typically around 10 kHz, have been observed at the plasma edge in numerous discharges. When the additional heating power is varied, the frequency is found to scale with Cs/R. The MUltiple SIgnal Classification (MUSIC) algorithm is employed to access the temporal evolution of the perpendicular velocity of density fluctuations. The method is presented in some detail, and is validated and compared against standard methods, such as the conventional fast Fourier transform method, using a synthetic signal. It stands out as a powerful data analysis method to follow the Doppler frequency with a high temporal resolution, which is important in order to extract the dynamics of GAMs.

  2. Uncertainty of canal seepage losses estimated using flowing water balance with acoustic Doppler devices

    Martin, Chad A.; Gates, Timothy K.

    2014-09-01

    Seepage losses from unlined irrigation canals amount to a large fraction of the total volume of water diverted for agricultural use, posing problems to both water conservation and water quality. Quantifying these losses and identifying areas where they are most prominent are crucial for determining the severity of seepage-related complications and for assessing the potential benefits of seepage reduction technologies and materials. A relatively easy and inexpensive way to estimate losses over an extensive segment of a canal is the flowing water balance, or inflow-outflow, method. Such estimates, however, have long been considered fraught with ambiguity due both to measurement error and to spatial and temporal variability. This paper presents a water balance analysis that evaluates uncertainty in 60 tests on two typical earthen irrigation canals. Monte Carlo simulation is used to account for a number of different sources of uncertainty. Issues of errors in acoustic Doppler flow measurement, in water level readings, and in evaporation estimates are considered. Storage change and canal wetted perimeter area, affected by variability in the canal prism, as well as lagged vs. simultaneous measurements of discharge at the inflow and outflow ends also are addressed. Mean estimated seepage loss rates for the tested canal reaches ranged from about -0.005 (gain) to 0.110 m3 s-1 per hectare of canal wetted perimeter (or -0.043 to 0.95 m d-1) with estimated probability distributions revealing substantial uncertainty. Across the tests, the average coefficient of variation was about 240% and the average 90th inter-percentile range was 0.143 m3 s-1 per hectare (1.24 m d-1). Sensitivity analysis indicates that while the predominant influence on seepage uncertainty is error in measured discharge at the upstream and downstream ends of the canal test reach, the magnitude and uncertainty of storage change due to unsteady flow also is a significant influence. Recommendations are

  3. Ocean current data measured by the Acoustic Doppler Current Profiler (ADCP) aboard the Discoverer Enterprise oil platform from May 23, 2010 to July 04, 2010 in the Gulf of Mexico in response to the Deepwater Horizon oil spill (NODC Accession 0083684)

    National Oceanic and Atmospheric Administration, Department of Commerce — Ocean current data were collected by ADCP aboard the Discoverer Enterprise in the Gulf of Mexico in response to the Deepwater Horizon oil spill event on April 20,...

  4. Ocean current data measured by the Acoustic Doppler Current Profiler (ADCP) aboard the Development Driller III from 2010-05-31 to 2010-07-04 in the Gulf of Mexico in response to the Deepwater Horizon oil spill (NODC Accession 0083634)

    National Oceanic and Atmospheric Administration, Department of Commerce — Ocean current data were collected by ADCP aboard the Discoverer Enterprise in the Gulf of Mexico in response to the Deepwater Horizon oil spill event on April 20,...

  5. The investigation of sediment processes in rivers by means of the Acoustic Doppler Profiler

    Guerrero, M.

    2014-09-01

    The measurement of sediment processes at the scale of a river cross-section is desirable for the evaluation of many issues related to river hydro-morphodynamics, such as the calibration and validation of numerical models for predicting the climate change impacts on water resources and efforts of maintenance of the navigation channel and other hydraulic works. Suspended- and bed-load have traditionally been measured by cumbersome techniques that are difficult to apply in large rivers. The acoustics for the investigation of small-scale sedimentological processes gained acceptance in the marine community because of its ability to simultaneously profile sediment concentration and size distribution, non-intrusively, and with high temporal and spatial resolution. The application of these methods in true riverine case studies presents additional difficulties, mainly related to water depths and stream currents that limit sound propagation into water and challenge the instruments deployment, especially during floods. This article introduces the motivations for using the ADCP for sediment processes investigation other than for flow discharge measurement, summarizes the developed methods and indicates future desirable improvements. In addition, an application on the Po River in Italy is presented, focusing on the calibration of the existing software by means of ADCP recordings. The calibrated model will assist in planning the dredging activities to maintain the navigation channel and the intake of a pump station for irrigation that is periodically obstructed with a sandbar.

  6. Compensation of Linear Multiscale Doppler for OFDM-Based Underwater Acoustic Communication Systems

    A. E. Abdelkareem

    2012-01-01

    Full Text Available In particular cases, such as acceleration, it is required to design a receiver structure that is capable of accomplishing time varying Doppler compensation. In this paper, two approaches are taken into consideration in order to estimate the symbol timing offset parameter. The first method employed to achieve an estimate of this particular parameter is based upon centroid localization and this prediction is reinforced by a second technique which utilises linear prediction, based on the assumption that the speed changes linearly during the OFDM symbol time. Subsequently, the two estimations of the symbol timing offset parameter are smoothed in order to obtain a fine tuned approximation of the Doppler scale. Additionally, the effects of weighting coefficients on smoothing the Doppler scale and on the performance of the receiver are also investigated. The proposed receiver is investigated, incorporating an improvement that includes fine tuning of the coarse timing synchronization in order to accommodate the time-varying Doppler. Based on this fine-tuned timing synchronization, an extension to the improved receiver is presented to assess the performance of two point correlations. The proposed algorithms' performances were investigated using real data obtained from an experiment that took place in the North Sea in 2009.

  7. Model of the Long Island Sound outflow: Comparison with year-long HF radar and Doppler current observations

    Mau, Jenq-Chi; Wang, Dong-Ping; Ullman, David S.; Codiga, Daniel L.

    2008-08-01

    A three-dimensional primitive-equation model is used to simulate the Long Island Sound (LIS) outflow for a 1-year (2001) period. The model domain includes LIS and New York Bight (NYB). Tidal and wind forcing are included, and seasonal salinity and temperature variations are assimilated. The model results are validated with the HF radar, moored acoustic Doppler current profiler (ADCP), and ferry-based ADCP observations. The agreement between simulated and observed flow patterns generally is very good. The difference in seasonal mean currents between the model and moored ADCP is about 0.01 m/s; the correlation of dominant velocity fluctuations between the model and HF radar is 0.83; and the difference in mean LIS transport between the model and shipboard ADCP is about 5%. However, the model predicts a prominent tidally generated headland eddy not supported by the HF radar observation. The model sensitivity study indicates that the tides, winds, and ambient coastal front all have important impact on the buoyant outflow. The tides and winds cause stronger vertical mixing, which reduces the surface plume strength. The ambient coastal front, on the other hand, tends to enhance the plume.

  8. Current Density Imaging through Acoustically Encoded Magnetometry: A Theoretical Exploration

    Sheltraw, Daniel J

    2014-01-01

    The problem of determining a current density confined to a volume from measurements of the magnetic field it produces exterior to that volume is known to have non-unique solutions. To uniquely determine the current density, or the non-silent components of it, additional spatial encoding of the electric current is needed. In biological systems such as the brain and heart, which generate electric current associated with normal function, a reliable means of generating such additional encoding, on a spatial and temporal scale meaningful to the study of such systems, would be a boon for research. This paper explores a speculative method by which the required additional encoding might be accomplished, on the time scale associated with the propagation of sound across the volume of interest, by means of the application of a radially encoding pulsed acoustic spherical wave.

  9. Design of Yagi antennas for a Doppler radar system that measures ocean surface currents

    The purpose of this study was to design Yagi antennas meeting the design criteria. The study consisted of numerical calculations made with the Lawrence Livermore Laboratory SWANT computer code. The code was modified to include a gain calculation, to incorporate normalized field-pattern calculations, and to output the plots and summaries presented in the 62 figures at the end of the report. These antennas were designed for the National Oceanographic and Atmospheric Administration (NOAA) for use in its Doppler backscatter radar system that monitors the near-coastline ocean surface currents

  10. Invariant currents in lossy acoustic waveguides with complete local symmetry

    Kalozoumis, P A; Diakonos, F K; Theocharis, G; Schmelcher, P

    2015-01-01

    We implement the concept of complete local symmetry in lossy acoustic waveguides. Despite the presence of losses, the existence of a spatially invariant current is shown theoretically and observed experimentally. We demonstrate how this invariant current leads to the generalization of the Bloch and parity theorems for lossy systems defining a mapping of the pressure field between symmetry related spatial domains. Using experimental data we verify this mapping with remarkable accuracy. For the performed experiment we employ a construction technique based on local symmetries which allows the design of setups with prescribed perfect transmission resonances in the lossless case. Our results reveal the fundamental role of symmetries in restricted spatial domains and clearly indicate that completely locally symmetric devices constitute a promising class of setups, regarding the manipulation of wave propagation.

  11. The acoustic Doppler effect applied to the study of linear motions

    In this work, the change of frequency of a sound wave due to the Doppler effect has been measured using a smartphone. For this purpose, a speaker at rest and a smartphone placed on a cart on an air track were used. The change in frequency was measured by using an application for Android™, ‘Frequency Analyzer’, which was developed by us specifically for this work. This made it possible to analyze four types of mechanical motions: uniform linear motion, uniform accelerated linear motion, harmonic oscillations and damped harmonic oscillations. These experiments are suitable for undergraduate students. The main novelty of this work was the possibility of measuring the instantaneous frequency as a function of time with high precision. The results were compared with alternative measurements yielding good agreement. (paper)

  12. Acoustic velocity measurement by means of Laser Doppler Velocimetry: Development of an Extended Kalman Filter and validation in free-field measurement

    Le Duff, Alain; Plantier, Guy; Valière, Jean C.; Gazengel, Bruno

    2016-03-01

    A signal processing technique, based on the use of an Extended Kalman Filter, has been developed to measure sound fields by means of Laser Doppler Velocimetry in weak flow. This method allows for the parametric estimation of both the acoustic particle and flow velocity for a forced sine-wave excitation where the acoustic frequency is known. The measurements are performed from the in-phase and the quadrature components of the Doppler downshifted signal thanks to an analog quadrature demodulation technique. Then, the estimated performance is illustrated by means of Monte-Carlo simulations obtained from synthesized signals and compared with asymptotic and analytical forms for the Cramer-Rao Bounds. Results allow the validity domain of the method to be defined and show the availability for free-field measurements in a large range. Finally, an application based on real data obtained in free field is presented.

  13. Online Doppler Effect Elimination Based on Unequal Time Interval Sampling for Wayside Acoustic Bearing Fault Detecting System

    Kesai Ouyang; Siliang Lu; Shangbin Zhang; Haibin Zhang; Qingbo He; Fanrang Kong

    2015-01-01

    The railway occupies a fairly important position in transportation due to its high speed and strong transportation capability. As a consequence, it is a key issue to guarantee continuous running and transportation safety of trains. Meanwhile, time consumption of the diagnosis procedure is of extreme importance for the detecting system. However, most of the current adopted techniques in the wayside acoustic defective bearing detector system (ADBD) are offline strategies, which means that the s...

  14. Design and performance of acoustic planar array antenna for Doppler sodar

    A.Kamalakumari

    2012-09-01

    Full Text Available The remote probing of the thermal structure and the wind velocity in the lower atmosphere requires highly directive antennas, which should have a half-power beam width of about ±10° (3-dB points, a 90°-sidelobe suppression of at least 40 dB, little volume reverberation, low wind sensitivity, and be made of weatherproofmaterial. In this paper, various off-axis planar antennas have been built and acoustically evaluated the design aspects, measured results and field patterns of an 8x8 acoustic planar array antennas are described. Tweeter elements are arranged in a planar geometry and are capable of transmitting vertical polarization when placed nearly horizontal, are appropriate for the sodar applications. The performance of 8x8 planar antennas are tested experimentally for the frequencies from 1.8KHz to 4KHz at elevation angles ranging between 0 to 180°.The experimental results, as well as the measured beam widths and field patterns of this antennas, are presented.

  15. Phononic crystal surface mode coupling and its use in acoustic Doppler velocimetry.

    Cicek, Ahmet; Salman, Aysevil; Kaya, Olgun Adem; Ulug, Bulent

    2016-02-01

    It is numerically shown that surface modes of two-dimensional phononic crystals, which are Bloch modes bound to the interface between the phononic crystal and the surrounding host, can couple back and forth between the surfaces in a length scale determined by the separation of two surfaces and frequency. Supercell band structure computations through the finite-element method reveal that the surface band of an isolated surface splits into two bands which support either symmetric or antisymmetric hybrid modes. When the surface separation is 3.5 times the lattice constant, a coupling length varying between 30 and 48 periods can be obtained which first increases linearly with frequency and, then, decreases rapidly. In the linear regime, variation of coupling length can be used as a means of measuring speeds of objects on the order of 0.1m/s by incorporating the Doppler shift. Speed sensitivity can be improved by increasing surface separation at the cost of larger device sizes. PMID:26565078

  16. Theory of the anomalous doppler instability during lower-hybrid current drive

    An instability condition is derived for electrostatic waves obeying the dispersion relation ω = ω/sub p//sub e/k/sub parallel//k using a two dimensional electron distribution function, f(v/sub parallel/,v/sub perpendicular/), appropriate for lower-hybrid current drive. It is found that when the raised plateau in f in the velocity range v12 has a sufficiently large anisotropy, T/sub p//sub parallel/>T/sub p//sub perpendicular/, this mode can become unstable. If the plateau velocities satisfy the condition v2/v1>1+ω/sub c//sub e//ω/sub p//sub e/ then waves exist with phase velocities in the plateau region and these waves are most easily destabilized by the anomalous doppler resonance, ω-k/sub parallel/v/sub parallel/ = -ω/sub c//sub e/

  17. Current recommendations for the study of carotid stenosis by doppler ultrasound and other imaging techniques

    Ischemic cerebrovascular disease has been one of the most frequent causes of death from chronic disease, as well as cause of long-term disabilities, in both the United States, and in Latin American countries during recent years. It is therefore, important to know about it. An updated review of international recommendations to the Costa Rican health system is performed for carotid imaging study in patients at risk of accidents and ischemic cerebrovascular disease; with special emphasis on carotid Doppler ultrasonography, due to its wide availability in the medical field Costa Rican. Furthermore, certain relevant concepts of other imaging techniques currently available are listed to determine the appropriate choice of each method according to the individual patient's condition, such as conventional angiography and tomographic angiography

  18. Continuous measurements of suspended sediment loads using dual frequency acoustic Doppler profile signals

    Antonini, Alessandro; Guerrero, Massimo; Rüther, Nils; Stokseth, Siri

    2016-04-01

    A huge thread to Hydropower plants (HPP) is incoming sediments in suspension from the rivers upstream. The sediments settle in the reservoir and reduce the effective head as well as the volume and reduce consequently the lifetime of the reservoir. In addition are the fine sediments causing severe damages to turbines and infrastructure of a HPP. For estimating the amount of in-coming sediments in suspension and the consequent planning of efficient counter measures, it is essential to monitor the rivers within the catchment of the HPP for suspended sediments. This work is considerably time consuming and requires highly educated personnel and is therefore expensive. Surrogate-indirect methods using acoustic and optic devices have bee developed since the last decades that may be efficiently applied for the continuous monitoring of suspended sediment loads. The presented study proposes therefore to establish a research station at a cross section of a river which is the main tributary to a reservoir of a HPP and equip this station with surrogate as well as with common method of measuring suspended load concentrations and related flow discharge and level. The logger at the research station delivers data automatically to a server. Therefore it is ensured that also large flood events are covered. Data during flood are of high interest to the HPP planners since they carried the most part of the sediment load in a hydrological year. Theses peaks can hardly be measured with common measurement methods. Preliminary results of the wet season 2015/2016 are presented. The data gives insight in the applicable range, in terms of scattering particles concentration-average size and corresponding flow discharge and level, eventually enabling the study of suspended sediment load-water flow correlations during peak events. This work is carried out as part of a larger research project on sustainable hydro power plants exposed to high sediment yield, SediPASS. SediPASS is funded by the

  19. Current state of the radiological diagnosis of acoustic neuroma

    Valavanis, A.; Dabir, K.; Hamdi, R.; Oguz, M.; Wellauer, J.

    1982-03-01

    Thin, overlapping section, contrast-enhanced, axial and coronal CT, with additional high-resulution (HR) treatment of the sections through the internal auditory canal, was performed on 31 patients clinically suspected of acoustic neuroma. With this technique 13 acoustic neuromas protruding more than 10 mm and eight acoustic neuromas protruding between 2 and 10 mm outside the internal auditory canal were unequivocally diagnosed. O/sub 2/CT cisternography was performed on ten patients. An intracanalicular neuroma was diagnosed in three cases with this technique, also a small extracanalicular neuroma in one case, and an acoustic neuroma was definitely excluded in six cases. It is concluded that O/sub 2/CT cisternography is the diagnostic procedure of choice for the detection of purely intracanalicular neuromas and the definite exclusion of acoustic neuroma. HR CT proved superior to polytomography for the evaluation of the internal auditory canal and should be performed in every case suspected of acoustic neuroma. A protocol for the radiological investigation of patients suspected of acoustic neuroma is given.

  20. An EOF analysis of HF Doppler radar current measurements of the Chesapeake Bay buoyant outflow

    Marmorino, G. O.; Shay, L. K.; Haus, B. K.; Handler, R. A.; Graber, H. C.; Horne, M. P.

    1999-02-01

    Surface currents measured by HF Doppler radar as part of a study of the Chesapeake Bay outflow plume are examined using a 'real-vector' empirical orthogonal function (EOF) analysis (Kaihatu et al., 1998). Based on about 23 days of nearly continuous data, the analysis shows that the first three EOF modes, judged to be the only significant modes, account for 76% of the variance in the data set. The buoyant outflow occurs primarily in the mean flow field. The first EOF mode is dominated by wind forcing and the second mode by across-shelf semi-diurnal tidal forcing. The third mode exhibits a large-scale horizontal shear and contains a curved region of weak relative flow which appears to delineate the offshore edge of the plume; also, the third-mode response varies over the spring-neap cycle, suggesting a modulation of the outflow plume by a tidal residual eddy. The analysis therefore has provided a useful, exploratory examination of this dataset of surface currents.

  1. Ion acoustic double layer in a current-carrying bounded plasma

    The experimental study of new type of ion acoustic double layer moving with the ion acoustic velocity in a current-carrying bounded plasma is presented. The structure of potential formation differs significantly from that observed in the recent experiment and existing theories do not fully account for the present structure. (author)

  2. Integration of a laser doppler vibrometer and adaptive optics system for acoustic-optical detection in the presence of random water wave distortions

    Land, Phillip; Robinson, Dennis; Roeder, James; Cook, Dean; Majumdar, Arun K.

    2016-05-01

    A new technique has been developed for improving the Signal-to-Noise Ratio (SNR) of underwater acoustic signals measured above the water's surface. This technique uses a Laser Doppler Vibrometer (LDV) and an Adaptive Optics (AO) system (consisting of a fast steering mirror, deformable mirror, and Shack-Hartmann Wavefront Sensor) for mitigating the effect of surface water distortions encountered while remotely recording underwater acoustic signals. The LDV is used to perform non-contact vibration measurements of a surface via a two beam laser interferometer. We have demonstrated the feasibility of this technique to overcome water distortions artificially generated on the surface of the water in a laboratory tank. In this setup, the LDV beam penetrates the surface of the water and travels down to be reflected off a submerged acoustic transducer. The reflected or returned beam is then recorded by the LDV as a vibration wave measurement. The LDV extracts the acoustic wave information while the AO mitigates the water surface distortions, increasing the overall SNR. The AO system records the Strehl ratio, which is a measure of the quality of optical image formation. In a perfect optical system the Strehl ratio is unity, however realistic systems with imperfections have Strehl ratios below one. The operation of the AO control system in open-loop and closed-loop configurations demonstrates the utility of the AO-based LDV for many applications.

  3. Doppler Velocimetry of Current Driven Spin Helices in a Two-Dimensional Electron Gas

    Yang, Luyi [Univ. of California, Berkeley, CA (United States)

    2013-05-17

    Spins in semiconductors provide a pathway towards the development of spin-based electronics. The appeal of spin logic devices lies in the fact that the spin current is even under time reversal symmetry, yielding non-dissipative coupling to the electric field. To exploit the energy-saving potential of spin current it is essential to be able to control it. While recent demonstrations of electrical-gate control in spin-transistor configurations show great promise, operation at room temperature remains elusive. Further progress requires a deeper understanding of the propagation of spin polarization, particularly in the high mobility semiconductors used for devices. This dissertation presents the demonstration and application of a powerful new optical technique, Doppler spin velocimetry, for probing the motion of spin polarization at the level of 1 nm on a picosecond time scale. We discuss experiments in which this technique is used to measure the motion of spin helices in high mobility n-GaAs quantum wells as a function of temperature, in-plane electric field, and photoinduced spin polarization amplitude. We find that the spin helix velocity changes sign as a function of wave vector and is zero at the wave vector that yields the largest spin lifetime. This observation is quite striking, but can be explained by the random walk model that we have developed. We discover that coherent spin precession within a propagating spin density wave is lost at temperatures near 150 K. This finding is critical to understanding why room temperature operation of devices based on electrical gate control of spin current has so far remained elusive. We report that, at all temperatures, electron spin polarization co-propagates with the high-mobility electron sea, even when this requires an unusual form of separation of spin density from photoinjected electron density. Furthermore, although the spin packet co-propagates with the two-dimensional electron gas, spin diffusion is strongly

  4. Integrating fluorescent dye flow-curve testing and acoustic Doppler velocimetry profiling for in situ hydraulic evaluation and improvement of clarifier performance.

    Tarud, F; Aybar, M; Pizarro, G; Cienfuegos, R; Pastén, P

    2010-08-01

    Enhancing the performance of clarifiers requires a thorough understanding of their hydraulics. Fluorescence spectroscopy and acoustic doppler velocimeter (ADV) profiling generally have been used separately to evaluate secondary settlers. We propose that simultaneous use of these techniques is needed to obtain a more reliable and useful evaluation. Experiments were performed on laboratory- and full-scale clarifiers. Factors affecting Fluorescein and Rhodamine 6G properties were identified. Underestimations up to 500% in fluorescence intensities may be derived from differential fluorescence quenching by oxygen. A careful control and interpretation of fluorescent dye experiments is needed to minimize artifacts in real settings. While flow-curve tests constructed under controlled conditions provided a more accurate overall quantitative estimation of the hydraulic performance, ADV velocity and turbulence profiling provided a detailed spatial understanding of flow patterns that was used to troubleshoot and fix the causes of hydraulic short-circuits. PMID:20853746

  5. Filamentation instability of nonextensive current-driven plasma in the ion acoustic frequency range

    The filamentation and ion acoustic instabilities of nonextensive current-driven plasma in the ion acoustic frequency range have been studied using the Lorentz transformation formulas. Based on the kinetic theory, the possibility of filamentation instability and its growth rate as well as the ion acoustic instability have been investigated. The results of the research show that the possibility and growth rate of these instabilities are significantly dependent on the electron nonextensive parameter and drift velocity. Besides, the increase of electrons nonextensive parameter and drift velocity lead to the increase of the growth rates of both instabilities. In addition, the wavelength region in which the filamentation instability occurs is more stretched in the presence of higher values of drift velocity and nonextensive parameter. Finally, the results of filamentation and ion acoustic instabilities have been compared and the conditions for filamentation instability to be dominant mode of instability have been presented

  6. Damping of an ion acoustic surface wave due to surface currents

    Lee, H J

    1999-01-01

    The well-known linear dispersion relation for an ion acoustic surface wave has been obtained by including the linear surface current density J sub z parallel to the interface and by neglecting the linear surface current density J sub x perpendicular to the interface. The neglect of J sub x is questionable although it leads to the popular boundary condition that the tangential electric field is continuous. In this work, linear dispersion relation for an ion acoustic surface wave is worked out by including both components of the linear current density J . When that is done, the ion acoustic wave turns out to be heavily damped. If the electron mass is taken to be zero (electrons are Bolzmann-distributed), the perpendicular component of the surface current density vanishes, and we have the well-known ion acoustic surface wave eigenmode. We conclude that an ion acoustic surface wave propagates as an eigenmode only when its phase velocity is much smaller than the electron thermal velocity.

  7. Currents and other physical parameters collected from moored current meters and various ADCPs offshore the United Kingdom, as part of British Oceanographic Data Center's (BODC) current meter series, from 21 June 1967 to 29 April 2007 (NODC Accession 0067029)

    National Oceanic and Atmospheric Administration, Department of Commerce — The BODC current meter data set provides all currents data held in the BODC National Oceanographic Database (NODB). It includes entries for Moored Acoustic Doppler...

  8. Are the Current Doppler Echocardiography Criteria Able to Discriminate Mitral Bileaflet Mechanical Heart Valve Malfunction? An In Vitro Study.

    Evin, Morgane; Guivier-Curien, Carine; Pibarot, Philippe; Kadem, Lyes; Rieu, Régis

    2016-05-01

    Malfunction of bileaflet mechanical heart valves in the mitral position could either be due to patient-prosthesis mismatch (PPM) or leaflet obstruction. The aim of this article is to investigate the validity of current echocardiographic criteria used for diagnosis of mitral prosthesis malfunction, namely maximum velocity, mean transvalvular pressure gradient, effective orifice area, and Doppler velocity index. In vitro testing was performed on a double activation left heart duplicator. Both PPM and leaflet obstruction were investigated on a St. Jude Medical Master. PPM was studied by varying the St. Jude prosthesis size (21, 25, and 29 mm) and stroke volume (70 and 90 mL). Prosthesis leaflet obstruction was studied by partially or totally blocking the movement of one valve leaflet. Mitral flow conditions were altered in terms of E/A ratios (0.5, 1.0, and 1.5) to simulate physiologic panel of diastolic function. Maximum velocity, effective orifice area, and Doppler velocity index are shown to be insufficient to distinguish normal from malfunctioning St. Jude prostheses. Doppler velocity index and effective orifice area were 1.3 ± 0.49 and 1.83 ± 0.43 cm(2) for testing conditions with no malfunction below the 2.2 and 2 cm(2) thresholds (1.19 cm(2) for severe PPM and 1.23 cm(2) for fully blocked leaflet). The mean pressure gradient reached 5 mm Hg thresholds for several conditions of severe PPM only (6.9 mm Hg and mean maximum velocity value: 183.4 cm/s) whereas such value was never attained in the case of leaflet obstruction. In the case of leaflet obstruction, the maximum velocity averaged over the nine pulsed-wave Doppler locations increased by 38% for partial leaflet obstruction and 75% for a fully blocked leaflet when compared with normal conditions. Current echocardiographic criteria might be suboptimal for the detection of bileaflet mechanical heart valve malfunction. Further developments and investigations are required in order

  9. Acoustic microfluidics: Capillary waves and vortex currents in a spherical fluid drop

    Lebedev-Stepanov, P. V.; Rudenko, O. V.

    2016-07-01

    We calculate the radiation forces in a spherical drop lying on a solid substrate. The forces form as a result of the action of a capillary wave on a fluid as it propagates along the free spherical surface. We study the structure of acoustic currents excited by the radiation forces.

  10. Current Applications of Scanning Coherent Doppler Lidar in Wind Energy Industry

    Krishnamurthy, R.; Boquet, M.; Osler, E.

    2016-06-01

    Scanning Doppler Lidars have become more prominent in the wind energy industry for a variety of applications. Scanning Lidar's provide spatial variation of winds and direction over a large area, which can be used to assess the spatial uncertainty of winds and analyze complex flows. Due to the recent growth in wind energy, wind farms are being built in complex terrain areas and fine tuning of the existing wind farms for optimized performance have gained significant interest. Scanning Lidar is an ideal tool for improved assessment of flow over complex terrains and wake characterization of large wind farms. In this article, the various applications of Lidar in the wind industry are discussed and results from several campaigns conducted in US and Europe is presented. The conglomeration of results provided in this article would assist wind energy developers and researchers in making improved decisions about their wind farm operations and pre-construction analysis using scanning Lidar's.

  11. The 2011 Tohoku tsunami south of Oahu: High-frequency Doppler radio observations and model simulations of currents

    Benjamin, L. R.; Flament, P.; Cheung, K. F.; Luther, D. S.

    2016-02-01

    A 16 MHz high-frequency Doppler radio (HFDR) deployed on the south shore of Oahu (Hawaii) detected oscillatory radial currents following the arrival of the 2011 Tohoku tsunami. The observations over a two-dimensional area provided an opportunity for intercomparison with the spatial patterns of currents and the resonant modes predicted by a nonhydrostatic model. Over the 50 m deep Penguin Bank, extending west from Molokai, the observed currents are intensified in two areas: 43 min period currents of 0.27 m s-1 lasting 6 h are observed on the south part of the bank, while 27 min period currents of 0.14 m s-1 lasting 2 h are observed on the north. The spatial EOFs suggest that standing full-waves and 3/2 waves formed over the bank. Modeled currents over Penguin Bank are similar to the observations but their north-south asymmetry is less pronounced than observed. Nearshore, observed alongshore currents showed long-period oscillations of 43 min that stretched along the entire coastline, while modeled currents show strong evidence for edge waves. EOF analysis of the nearshore signal suggests that the HFDR and model reveal different processes. The discrepancy might be attributed to the fact that both the Penguin Bank and nearshore observations are limited by HFDR sensitivity to azimuthal sidelobe contamination and decreased angular resolution at high steering angles.

  12. The Influence of Ion-Acoustic Turbulence on the Electron Acceleration in the Reconnecting Current Sheet

    Gui-Ping Wu; Guang-Li Huang; Yu-Hua Tang

    2005-01-01

    Through solving the single electron equation of motion and the FokkerPlanck equation including the terms of electric field strength and ion-acoustic turbulence, we study the influence of the ion-acoustic wave on the electron acceleration in turbulent reconnecting current sheets. It is shown that the ion-acoustic turbulence which causes plasma heating rather than particle acceleration should be considered. With typical parameter values, the acceleration time scale is around the order of 10-6 s, the accelerated electrons may have approximately a power-law distribution in the energy range 20 ~ 100 keV and the spectral index is about 3~10, which is basically consistent with the observed hard X-ray spectra in solar flares.

  13. The average direct current offset values for small digital audio recorders in an acoustically consistent environment.

    Koenig, Bruce E; Lacey, Douglas S

    2014-07-01

    In this research project, nine small digital audio recorders were tested using five sets of 30-min recordings at all available recording modes, with consistent audio material, identical source and microphone locations, and identical acoustic environments. The averaged direct current (DC) offset values and standard deviations were measured for 30-sec and 1-, 2-, 3-, 6-, 10-, 15-, and 30-min segments. The research found an inverse association between segment lengths and the standard deviation values and that lengths beyond 30 min may not meaningfully reduce the standard deviation values. This research supports previous studies indicating that measured averaged DC offsets should only be used for exclusionary purposes in authenticity analyses and exhibit consistent values when the general acoustic environment and microphone/recorder configurations were held constant. Measured average DC offset values from exemplar recorders may not be directly comparable to those of submitted digital audio recordings without exactly duplicating the acoustic environment and microphone/recorder configurations. PMID:24502252

  14. Persistence of Albunex (ALB) Ultrasound Contrast Agent – Invitro Study of the Effects of Pressure and Acoustic Power on Particle-Size, and the Duration of Contrast and Doppler Enhancement

    Shandas, Robin; Sahn, David J.; Bales, Gary; Elkadi, Taher; Yau, Kwong-Kun; Gharib, Morteza

    1990-01-01

    LV contrast intensity after intravenous ALB injection varies with the cardiac cycle, raising questions about the pressure related stability of the particle. We explored pressure stability and the influence of acoustic power on ALB effect in an in-vitro pulsatile model at receiving chamber (RC) pressures between 10-160 mmHg. Ultrasound imaging was performed at 5MHz along with 3.5MHz color Doppler at maximal and minimal levels of acoustic power output on a VingMed CFM ...

  15. Acoustics

    Goodman, Jerry R.; Grosveld, Ferdinand

    2007-01-01

    The acoustics environment in space operations is important to maintain at manageable levels so that the crewperson can remain safe, functional, effective, and reasonably comfortable. High acoustic levels can produce temporary or permanent hearing loss, or cause other physiological symptoms such as auditory pain, headaches, discomfort, strain in the vocal cords, or fatigue. Noise is defined as undesirable sound. Excessive noise may result in psychological effects such as irritability, inability to concentrate, decrease in productivity, annoyance, errors in judgment, and distraction. A noisy environment can also result in the inability to sleep, or sleep well. Elevated noise levels can affect the ability to communicate, understand what is being said, hear what is going on in the environment, degrade crew performance and operations, and create habitability concerns. Superfluous noise emissions can also create the inability to hear alarms or other important auditory cues such as an equipment malfunctioning. Recent space flight experience, evaluations of the requirements in crew habitable areas, and lessons learned (Goodman 2003; Allen and Goodman 2003; Pilkinton 2003; Grosveld et al. 2003) show the importance of maintaining an acceptable acoustics environment. This is best accomplished by having a high-quality set of limits/requirements early in the program, the "designing in" of acoustics in the development of hardware and systems, and by monitoring, testing and verifying the levels to ensure that they are acceptable.

  16. Ocean currents measured by shipboard ADCP from global oceans from the Joint Archive for Shipboard ADCP holdings from 2000-07 to 2012-02 (NODC Accession 0093159)

    National Oceanic and Atmospheric Administration, Department of Commerce — Absolute U- and V-component ocean current vectors from Shipboard Acoustic Doppler Current Profilers (SADCP), as both a high frequency sampling (nominally 5 minutes...

  17. Superharmonic microbubble Doppler effect in ultrasound therapy

    Pouliopoulos, Antonios N.; Choi, James J.

    2016-08-01

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

  18. A Comment on Interaction of Lower Hybrid Waves with the Current-Driven Ion-Acoustic Instability

    Schrittwieser, R.; Juul Rasmussen, Jens

    1985-01-01

    Majeski et al. (1984) have investigated the interaction between the current-driven 'ion-acoustic' instability and high frequency lower hybrid waves. The 'ion-acoustic' instability was excited by drawing an electron current through the plasma column of a single-ended Q-machine by means of a...... positively biased cold plate. Schmittwieser et al. do not believe that the observed instability is of the ion-acoustic type but that it is rather the so-called potential relaxation instability....

  19. Doppler blood flow indicator

    Byrtus, David

    2014-01-01

    This bachelor´s thesis deals with basis of ultra-acoustics. The project presents basic information about Doppler effect. It describes the methods of processing and analyzing of velocity and direction of blood at doppler’s systems with modulated and unmodulated carrier wave. The project presents the system design of non-directional doppler indicator with unmodulated carrier wave for 8 MHz frequency, generating intensity of ultrasound 100 mW/cm2 and diameter D-shaped transmitting transducer 8 m...

  20. A field intercomparison between an acoustic current profiler / ADCP and two Savonius type current meters

    Gytre, Trygve; Østensen, Øivind

    1990-01-01

    During an introductory experiment in Lofoten May 1990 data from a vessel mounted ADCP on an anchored research vessel were intercompared with corresponding data from two anchored rotor current meters in a region where the current speed varied between 0 and 30 cm/s. The results showed good agreements when the ships heading was stable. When the anchored ship described "S" or "O"- shaped horizontal motions due to varying wind stress, the ADCP added up to 15 cm/s. to its output signal.

  1. Study on Doppler Effects Estimate in Underwater Acoustic Communication Based on Fractional Fourier Transform%基于分数阶Fourier变换的水声通信多普勒系数估计技术研究

    霍雁明; 刘媛; 张晓

    2012-01-01

    An estimate method of the Doppler effects in mobile underwater acoustic communication based on fractional Fourier transform has been proposed.The Doppler coefficients are obtained by estimating chirp rate change of LFM signal with fractional Fourier transform(FRFT) in this paper.And the performance of the Doppler effects estimation method based on FRFT is verified by the computer simulation.%本文基于传统多普勒系数估计方法,提出一种基于分数阶Fourier变换的多普勒系数估计方法,该方法利用分数阶Fourier变换估计得到经过信道后LFM信号调频斜率的变化量值,进而得到多普勒系数的估计。通过计算机仿真研究验证了该方法的有效性与稳健性。

  2. Current state of acoustic emission as an aid to the structural integrity assessment of nuclear power plants

    As an integral method permitting continuous monitoring and remote defect location, acoustic emission offers promising benefits for the nuclear industry. The potential applications relating to the integrity of the primary pressure boundary of nuclear reactors that are considered in this presentation are: detection of flaws during pre-service and requalification hydrotests and continuous monitoring for crack growth and leakage. The correlations between fracture mechanics and acoustic emission are discussed on the basis of certain fundamentals of material emission behaviour. The influence of instrumentation and wave propagation related aspects on the detectability and evaluation of acoustic emission signals is considered. A critical review is given of the application of acoustic emission to the assessment of reactor pressure vessel integrity, which demands a precise knowledge of the method's ability to distinguish different origins of acoustic emission, to detect and locate cracks and to evaluate the severity of cracks. World wide, at least 40 reactor pressure vessels and nuclear primary systems have been monitored by acoustic emission, either during acceptance pressure tests at the manufacturer's shop or during pre-service testing after installation in a plant. Together with the monitoring of requalification hydrotests after a certain period of operation, these applications of acoustic emission are currently receiving the most attention. The experience gained with continuous monitoring by acoustic emission is reported. The technique of leak detection by acoustic emission shows promising results, which permit the location and quantification of leaks. It is expected that practical experience and future research work will enhance the accuracy and detection sensitivity. (author)

  3. Surface acoustic wave amplification by direct current-voltage supplied to graphene film

    Using a high-resolution X-Ray diffraction measurement method, the surface acoustic wave (SAW) propagation in a graphene film on the surface of a Ca3TaGa3Si2O14 (CTGS) piezoelectric crystal was investigated, where an external current was driven across the graphene film. Here, we show that the application of the DC field leads to a significant enhancement of the SAW magnitude and, as a result, to amplification of the diffraction satellites. Amplification of 33.2 dB/cm for the satellite +1, and of 13.8 dB/cm for the satellite +2, at 471 MHz has been observed where the external DC voltage of +10 V was applied. Amplification of SAW occurs above a DC field much smaller than that of a system using bulk semiconductor. Theoretical estimates are in reasonable agreement with our measurements and analysis of experimental data for other materials

  4. Reverse Doppler Effect of Sound

    Lee, Sam Hyeon; Park, Choon Mahn; Seo, Yong Mun; Wang, Zhi Guo; Kim, Chul Koo

    2009-01-01

    We report observation of reverse Doppler effect in a double negative acoustic metamaterial. The metamaterial exhibited negative phase velocity and positive group velocity. The dispersion relation is such that the wavelength corresponding to higher frequency is longer. We observed that the frequency was down-shifted for the approaching source, and up-shifted when the source receded.

  5. Acoustic Noise Alters Selective Attention Processes as Indicated by Direct Current (DC Brain Potential Changes

    Karin Trimmel

    2014-09-01

    Full Text Available Acoustic environmental noise, even of low to moderate intensity, is known to adversely affect information processing in animals and humans via attention mechanisms. In particular, facilitation and inhibition of information processing are basic functions of selective attention. Such mechanisms can be investigated by analyzing brain potentials under conditions of externally directed attention (intake of environmental information versus internally directed attention (rejection of environmental stimuli and focusing on memory/planning processes. This study investigated brain direct current (DC potential shifts—which are discussed to represent different states of cortical activation—of tasks that require intake and rejection of environmental information under noise. It was hypothesized that without background noise rejection tasks would show more positive DC potential changes compared to intake tasks and that under noise both kinds of tasks would show positive DC shifts as an expression of cortical inhibition caused by noise. DC potential shifts during intake and rejection tasks were analyzed at 16 standard locations in 45 persons during irrelevant speech or white noise vs. control condition. Without noise, rejection tasks were associated with more positive DC potential changes compared to intake tasks. During background noise, however, this difference disappeared and both kinds of tasks led to positive DC shifts. Results suggest—besides some limitations—that noise modulates selective attention mechanisms by switching to an environmental information processing and noise rejection mode, which could represent a suggested “attention shift”. Implications for fMRI studies as well as for public health in learning and performance environments including susceptible persons are discussed.

  6. Modificações da hemodinâmica fetal pelo estímulo sonoro: avaliação pela dopplervelocimetria colorida Vibro-acoustic stimulation induced hemodynamic fetal changes assessed by color doppler

    Francisco Mauad Filho

    1999-04-01

    Full Text Available Objetivos: verificar se ocorrem ou não alterações hemodinâmicas na aréria cerebral média (ACM aferido pela dopplervelocimetria colorida após realização de um estímulo sonoro. Métodos: trinta fetos de gestantes consideradas clinicamente normais com idade gestacional igual ou superior a 28 semanas foram submetidos a um estímulo sonoro. Examinamos as alterações da velocidade sangüínea na ACM fetal por meio do índice de resistência e da freqüência cardíaca fetal, pelo doppler colorido, antes e depois do estímulo acústico. Resultados: a média da freqüência cardíaca fetal (FCF antes do estímulo sonoro foi de 142,41 batimentos por minuto (bpm com desvio padrão de 9,01 e faixa de variação de 122 a 162 bpm. Após o estímulo sonoro, a média da FCF foi de 159,44 bpm com desvio padrão de 15,49, com faixa de variação de 130 a 187 bpm (pPurpose: to determine the possible occurrence of hemodynamic changes in the middle cerebral artery of the fetus (MCA using color doppler after vibro-acoustic stimulation. Methods: thirty fetuses from pregnant women considered to be clinically normal, with a gestational age of 28 weeks or more were submitted to vibro-acoustic stimulation. We examined the changes in blood flow rate in the middle cerebral artery of the fetus on the basis of resistance index (RI and fetal heart rate (FHR by color doppler before and after the sound stimulus. Results: mean FHR before vibro-acoustic stimulation was 142.41 beats per minute (bpm with a standard deviation of 9.01 and a range of 122 to 162 bpm. After stimulation, mean FHR was 159.44 bpm with a standard deviation of 15.49 and a range of 130 to 187 bpm (p<0.01. Mean RI in the MCA of the fetuses was 75.89% (range: 64 to 91% before the experiment. After the vibro-acoustic stimulation, mean RI was 66.93% (range: 47 to 83%; p < 0.01. Conclusions: we observed that a sound stimulus provokes the well-known immediate and significant elevation of FHR and a

  7. Amplification of surface acoustic waves by transverse electric current in piezoelectric semiconductors

    Gulyaev, Yuri V.

    1974-01-01

    It is shown that the principal characteristic feature of the surface acoustic waves in piezoelectrics—the presence of an alternating electric field transverse to the surface, which can be of the same order of magnitude as the longitudinal field—may not only give rise to the known transverse...... acoustoelectric effect but also lead to amplification of surface acoustic waves by electron drift perpendicular to the surface. For Love waves in a piezoelectric semiconductor film on a highly conducting substrate, the amplification coefficient is found and the conditions necessary for amplification...

  8. Validation of current acoustic dead-zone estimation methods in lakes with strongly sloped bottoms

    Tušer, Michal; Balk, H.; Mrkvička, T.; Frouzová, Jaroslava; Čech, Martin; Muška, Milan; Kubečka, Jan

    2011-01-01

    Roč. 9, - (2011), s. 507-514. ISSN 1541-5856 R&D Projects: GA ČR(CZ) GA206/07/1392 Grant ostatní: EEA FM, NFM(CZ) CZ 0091 Institutional research plan: CEZ:AV0Z60170517 Keywords : acoustic dead zone * bottom slope * lentic freshwater habitats Subject RIV: DA - Hydrology ; Limnology Impact factor: 1.535, year: 2011

  9. Acoustic phonons mediated non-equilibrium spin current in the presence of Rashba and Dresselhaus spin–orbit couplings

    Hasanirokh, K.; Phirouznia, A., E-mail: Phirouznia@azaruniv.ac.ir

    2013-10-30

    Influence of electrons interaction with longitudinal acoustic phonons on magnetoelectric and spin-related transport effects are investigated. The considered system is a two-dimensional electron gas system with both Rashba and Dresselhaus spin–orbit couplings. The works which have previously been performed in this field, have revealed that the Rashba and Dresselhaus couplings cannot be responsible for spin current in the non-equilibrium regime. In the current Letter, a semiclassical method was employed using the Boltzmann approach and it was shown that the spin current of the system, in general, does not go all the way to zero when the electron–phonon coupling is taken into account. It was also shown that spin accumulation of the system could be influenced by electron–phonon coupling.

  10. Speaker-Oriented Classroom Acoustics Design Guidelines in the Context of Current Regulations in European Countries

    Pelegrin Garcia, David; Brunskog, Jonas; Rasmussen, Birgit

    2014-01-01

    Most European countries have regulatory requirements or guidelines for reverberation time in classrooms which have the goal of enhancing speech intelligibility and reducing noise levels in schools. At the same time, school teachers suffer frequently from voice problems due to high vocal load...... experienced at work. With the aim of improving working conditions for teachers, this article presents guidelines for classroom acoustics design that meet simultaneously criteria of vocal comfort and speech intelligibility, which may be of use in future discussions for updating regulatory requirements in...

  11. [Acoustic emission diagnostic techniques for high-field high current-density super inducting poles

    Acoustic emission technology was introduced in the late 1970's to monitor superconducting magnets. It has now been firmly established that acoustic signals in superconducting magnets are emitted principally by mechanical events such as conductor strain, conductor motion, frictional motion, and epoxy cracking. Despite earlier suggestions, flux motion, except during flux jumping, does not appear to be an important source of AE signals in superconducting magnets. Of these several potential sources of AE signals in superconducting magnets, mechanical disturbances have been identified to be most important in high-performance, ''adiabatic'' magnets such as the dipoles used in accelerators. These mechanical disturbances are transitory, each generating a packet of AE signals that can be located with sensors. Source identification and location has been achieved with a number of superconducting magnets. In this section, the basic principle for the operation of adiabatic magnets is discussed, followed by presentation of some of the important experimental results relevant to the question of premature quench obtained at MIT

  12. Acoustic estimation of suspended sediment concentration

    ZHU; Weiqing(

    2001-01-01

    [1]Morse, P. H. , Theoretical Acoustics, New York: McGraw-Hill Book Co. , 1968.[2]Skudrjuk, E., Die Grundlagen der Akustik, Wien: Springer-Verlag, 1954.[3]Olshevskii, V. V., Statistical Characteristics of Sea Reverberation, Moscow: Nauka Publisher, 1966.[4]Thorne, P. D., Hardcastl, P. J., Soulsby, R. L., Analysis of acoustic measurements of suspended sediments, J. Geop.Res. , 1993, 98: 899.[5]Guo Jijie, Ren Laifa, Li Yunwu, ln-situ calibration of acoustic measurement of suspended sedienmt, Acta Oceanologica Sini-ca, 1998, (20): 120-125.[6]Zhang Shuying, Li Yunwu, Development and application of an acoustic suspended sediemnt monitoring system, Acta Oceanologica Sinica, 1998, (20): 114-119.[7]Zhang Shuying, Li Yunwu, A theoretical analysis of acoustic suspended sediment obsvervation, Acta Acoustica, 1999, (24):267-274.[8]Zhu Weiqing, Pan Feng, Zhu Min et al. , IOA-1 Multi-function Acoustic Doppler Current Profiler (MADCP), OCEAN'2000,Rhode Island, USA.

  13. Range-instantaneous Doppler imaging of inverse synthetic aperture sonar

    XU Jia; JIANG Xingzhou; TANG Jingsong

    2003-01-01

    Because the existing range-Doppler algorithm in inverse synthetic aperture sonar (ISAS) is based on target model of uniform motion, it may be invalidated for maneuvering targets due to the time-varying changes of both individual scatter′s Doppler and imaging projection plane. To resolve the problem, a new range-instantaneous Doppler imaging method is proposed for imaging maneuvering targets based on time-frequency analysis. The proposed approach is verified using real underwater acoustic data.

  14. Doppler tracking

    Thomas, Christopher Jacob

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

  15. Maximum Likelihood Estimator For Doppler Parameter And Cramer Rao Bound In ZP-OFDM UWA Channel

    Lyonnet, Bastien; Siclet, Cyrille; Brossier, Jean-Marc

    2010-01-01

    A Doppler estimation system using a maximum likelihood criterion is presented in the context of underwater acoustic communications between moving transmitter/receiver. We simulate the method for the estimation of the Doppler effect induced by an underwater acoustic channel (UWA) using Zero Padded-Orthogonal Frequency Division Multiplexing (ZP-OFDM). Among the wide range of physical processes that impact OFDM communications through the underwater environment, Doppler effect is an important cau...

  16. Laser double Doppler flowmeter

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

    2014-05-01

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

  17. HF Doppler observations

    Kikuchi, T.; Sugiuchi, H.; Ishimine, T.; Maeno, H.; Honma, S.

    1986-12-01

    This paper reports the solar flare and geomagnetic storm effects on the frequency of JJY signals received at Okinawa (f = 15 MHz) and Kokubunji (f = 5 and 8 MHz) during the period of June-September 1982. The increase in the electron density due to solar flares is deduced from the Doppler frequency deviation of 1 Hz as 2 x 10/sup 15/ electrons/m/sub 2/ below the reflection height. The result is in good agreement with the observation of the total electron content by the Faraday rotation measurements. On July 13, 1982, an abrupt increase of 0.8 Hz in frequency followed by a decrease of 0.6 Hz was observed in association with the huge storm sudden commencement. This fact indicates a successive transmission of westward electric field of 1.5 mV/m and eastward electric field of 1.1 mV/m from the outer magnetosphere to the low latitude ionosphere. It is shown that the decreases in Doppler frequency were associated with geomagnetic bays. The strength of the electric field (1.8 mV/m) derived from the Doppler frequency deviation is 20% of that of the electric field which is required to produce ionospheric electric currents responsible for the geomagnetic field variation on the ground. The large amplitude Doppler frequency oscillations of period of 1-1.5 h were observed at Kokubunji and Okinawa with a delay time of 20-25 min during the geomagnetic storm on September 6, 1982. It is suggested that the large-scale TID (Travelling Ionospheric Disturbance) with a phase velocity of 600 m/s and a wavelength of 2000 km is produced at high latitudes and is propagated to low latitudes.

  18. Current-driven ion-acoustic and potential-relaxation instabilities excited in plasma plume during electron beam welding

    Trushnikov, D. N., E-mail: trdimitr@yandex.ru [The department for Applied Physics, Perm National Research Polytechnic University, Perm, 614990 (Russian Federation); Mladenov, G. M., E-mail: gmmladenov@abv.bg; Koleva, E. G., E-mail: eligeorg@abv.bg [Institute of Electronics, Bulgarian Academy of Sciences, 72 Tzarigradsko Shose, 1784, Sofia (Bulgaria); Technology Centre of Electron Beam and Plasma Technologies and Techniques, 68-70 Vrania, ap.10, Banishora,1309, Sofia (Bulgaria); Belenkiy, V. Ya., E-mail: mtf@pstu.ru; Varushkin, S. V., E-mail: stepan.varushkin@mail.ru [The department for Welding Production and Technology of Constructional Materials, Perm National Research Polytechnic University, Perm, 614990 (Russian Federation)

    2014-04-15

    Many papers have sought correlations between the parameters of secondary particles generated above the beam/work piece interaction zone, dynamics of processes in the keyhole, and technological processes. Low- and high-frequency oscillations of the current, collected by plasma have been observed above the welding zone during electron beam welding. Low-frequency oscillations of secondary signals are related to capillary instabilities of the keyhole, however; the physical mechanisms responsible for the high-frequency oscillations (>10 kHz) of the collected current are not fully understood. This paper shows that peak frequencies in the spectra of the collected high-frequency signal are dependent on the reciprocal distance between the welding zone and collector electrode. From the relationship between current harmonics frequency and distance of the collector/welding zone, it can be estimated that the draft velocity of electrons or phase velocity of excited waves is about 1600 m/s. The dispersion relation with the properties of ion-acoustic waves is related to electron temperature 10 000 K, ion temperature 2 400 K and plasma density 10{sup 16} m{sup −3}, which is analogues to the parameters of potential-relaxation instabilities, observed in similar conditions. The estimated critical density of the transported current for creating the anomalous resistance state of plasma is of the order of 3 A·m{sup −2}, i.e. 8 mA for a 3–10 cm{sup 2} collector electrode. Thus, it is assumed that the observed high-frequency oscillations of the current collected by the positive collector electrode are caused by relaxation processes in the plasma plume above the welding zone, and not a direct demonstration of oscillations in the keyhole.

  19. Dual-Doppler Feasibility Study

    Huddleston, Lisa L.

    2012-01-01

    radar geometry issues at the NWS MLB radar, such as the "cone of silence" or beam blockage. In the event of a radar outage at one of the sites, the multi-radar algorithms would provide continuing coverage of the area through use of the data from the remaining operational radar sites. There are several options to collect, edit, synthesize and display dual-Doppler data sets. These options include commercial packages available for purchase and a variety of freeware packages available from the National Center for Atmospheric Research (NCAR) for processing raw radar data. However, evaluation of the freeware packages revealed that they do not have sufficient documentation and configuration control to be certified for 45 SW use. Additionally, a TI data line must be installed/leased from the NWS MLB office and CCAFS to enable the receipt of NWS MLB raw radar data to use in the dual-Doppler synthesis. Integration of the TI data line into the Eastern Range infrastructure that will meet the security requirements necessary for 45 SW use is time-consuming and costly. Overall evaluation indicates that establishment of the dual-Doppler capability using the existing operational radar systems is desirable and feasible with no technical concerns. Installation of such a system represents a significant enhancement to forecasting capabilities at the 45 WS and at NWS MLB. However, data security and cost considerations must be evaluated in light of current budgetary constraints. In any case, gaining the dual-Doppler capability will provide opportunities for better visualization of the wind field and better forecasting of the onset of convection and severe weather events to support space launch operations at KSC and CCAFS.

  20. Springer Handbook of Acoustics

    Rossing, Thomas D

    2007-01-01

    Acoustics, the science of sound, has developed into a broad interdisciplinary field encompassing the academic disciplines of physics, engineering, psychology, speech, audiology, music, architecture, physiology, neuroscience, and others. The Springer Handbook of Acoustics is an unparalleled modern handbook reflecting this richly interdisciplinary nature edited by one of the acknowledged masters in the field, Thomas Rossing. Researchers and students benefit from the comprehensive contents spanning: animal acoustics including infrasound and ultrasound, environmental noise control, music and human speech and singing, physiological and psychological acoustics, architectural acoustics, physical and engineering acoustics, signal processing, medical acoustics, and ocean acoustics. This handbook reviews the most important areas of acoustics, with emphasis on current research. The authors of the various chapters are all experts in their fields. Each chapter is richly illustrated with figures and tables. The latest rese...

  1. Physical and chemical signatures of a developing anticyclonic eddy in the Leeuwin Current, eastern Indian Ocean

    Paterson, Harriet L.; Feng, Ming; Waite, Anya M.; Gomis, Damià; Beckley, Lynnath E.; Holliday, David; Thompson, Peter A

    2008-01-01

    A multidisciplinary cruise aboard the R/V Southern Surveyor was conducted in May 2006 to sample a developing anticyclonic eddy of the Leeuwin Current off Western Australia. The eddy formed from a meander of the Leeuwin Current in mid-April 2006 and remained attached to the current until mid-August. In this study, a combination of satellite data (altimeter, sea surface temperature, and chlorophyll a) and shipboard measurements (acoustic Doppler current profiler and conductivity-temperature-dep...

  2. QRev—Software for computation and quality assurance of acoustic doppler current profiler moving-boat streamflow measurements—Technical manual for version 2.8

    Mueller, David S.

    2016-01-01

    The software program, QRev applies common and consistent computational algorithms combined with automated filtering and quality assessment of the data to improve the quality and efficiency of streamflow measurements and helps ensure that U.S. Geological Survey streamflow measurements are consistent, accurate, and independent of the manufacturer of the instrument used to make the measurement. Software from different manufacturers uses different algorithms for various aspects of the data processing and discharge computation. The algorithms used by QRev to filter data, interpolate data, and compute discharge are documented and compared to the algorithms used in the manufacturers’ software. QRev applies consistent algorithms and creates a data structure that is independent of the data source. QRev saves an extensible markup language (XML) file that can be imported into databases or electronic field notes software. This report is the technical manual for version 2.8 of QRev.

  3. A stator flux oriented current vector control of a sensorless 6/4 SRM for reduction of acoustic noise and vibration

    In this paper, a stator flux oriented current vector control of a sensorless three-phase 6/4 switched reluctance motor without position sensors is presented. Space current vector control technology based on torque angle estimation was used to reduce the acoustic noise and vibration of the motor drive system. The power converter for the 6/4 switched reluctance motor is three-phase full bridge inverter. The experimental results show that the maximum level of acoustic noises and vibration are 73 dB and 8 dB; m/s/s, respectively, and the steady speed error of the drive system is less than 0.1% operated at the rated load when the drive system was operated below 1500 rpm. In addition, the transient speed performance is also satisfactory

  4. Nearly simultaneous measurements of radar auroral heights and Doppler velocities at 398 MHz

    Nearly simultaneous measurements of radar auroral heights and Doppler velocities were obtained using the Homer, Alaska, 398-MHz phased-array radar over a total of 16 hours on four different days. The heights show a consistent variation with time, being highest near the time of electrojet current reversal, and lowest late in the morning. A variety of east-west height asymmetries were observed, different from those previously reported, which can be explained in terms of favorable flow angles preferentially favoring high-altitude primary two-stream waves to one side of the field of view. Low-velocity echoes, presumably due to secondary irregularities, are found to be more restricted in height range than echoes with ion acoustic velocities, which presumably come from primary two-stream instabilities. Echo power was examined as a function of velocity and height. For the westward electrojet it was found that echoes with ion acoustic velocities are relatively constant in strength over most of their height range, but for low-velocity echoes the power is a maximum between 100 and 105 km and falls off steadily at greater heights. Doppler speeds show a noticeable decrease at heights below 105 km, in agreement with the expected variation in ion acoustic velocity

  5. The Development of Automated Detection Techniques for Passive Acoustic Monitoring as a Tool for Studying Beaked Whale Distribution and Habitat Preferences in the California Current Ecosystem

    Yack, Tina M.

    The objectives of this research were to test available automated detection methods for passive acoustic monitoring and integrate the best available method into standard marine mammal monitoring protocols for ship based surveys. The goal of the first chapter was to evaluate the performance and utility of PAMGUARD 1.0 Core software for use in automated detection of marine mammal acoustic signals during towed array surveys. Three different detector configurations of PAMGUARD were compared. These automated detection algorithms were evaluated by comparing them to the results of manual detections made by an experienced bio-acoustician (author TMY). This study provides the first detailed comparisons of PAMGUARD automated detection algorithms to manual detection methods. The results of these comparisons clearly illustrate the utility of automated detection methods for odontocete species. Results of this work showed that the majority of whistles and click events can be reliably detected using PAMGUARD software. The second chapter moves beyond automated detection to examine and test automated classification algorithms for beaked whale species. Beaked whales are notoriously elusive and difficult to study, especially using visual survey methods. The purpose of the second chapter was to test, validate, and compare algorithms for detection of beaked whales in acoustic line-transect survey data. Using data collected at sea from the PAMGUARD classifier developed in Chapter 2 it was possible to measure the clicks from visually verified Baird's beaked whale encounters and use this data to develop classifiers that could discriminate Baird's beaked whales from other beaked whale species in future work. Echolocation clicks from Baird's beaked whales, Berardius bairdii, were recorded during combined visual and acoustic shipboard surveys of cetacean populations in the California Current Ecosystem (CCE) and with autonomous, long-term recorders at four different sites in the Southern

  6. Clinical Doppler ultrasound

    The authors begin with the basics: how Doppler signals are formed, reflected, and refracted - and how those facts apply to clinical practice; anatomy (blood and blood flow), the Doppler equation (explained from a radiologic, rather than a mathematical, perspective); and approaches to Doppler signal production. The available methods of signal processing - including audio, multifilter analysis, zero-crossing detection, autocorrelation, and the Fast Fourier Transform, as well as more sophisticated techniques of duplex and color flow imaging - are covered with an eye to helping the ultrasonographer obtain the most reliable and artifact-free information from every Doppler reading

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

    Kumar, A.; Anderson, N.; Phillips, W. D.; Eckel, S.; Campbell, G. K.; Stringari, S.

    2015-01-01

    The Doppler effect, the shift in the frequency of sound due to motion, is present in both classical gases and quantum superfluids. Here, we perform an in-situ, minimally destructive measurement, of the persistent current in a ring-shaped, superfluid Bose-Einstein condensate using the Doppler effect. Phonon modes generated in this condensate have their frequencies Doppler shifted by a persistent current. This frequency shift will cause a standing-wave phonon mode to be "dragged" along with the...

  8. Optical Doppler shift with structured light

    Belmonte A.; Belmonte, Aniceto; de Torres, Juan P; Torres J.P.

    2011-01-01

    When a light beam with a transverse spatially varying phase is considered for optical remote sensing, in addition to the usual longitudinal Doppler frequency shift of the returned signal induced by the motion of the scatter along the beam axis, a new transversal Doppler shift appears associated to the motion of the scatterer in the plane perpendicular to the beam axis. We discuss here how this new effect can be used to enhance the current capabilities of optical measurement system...

  9. Current clinical applications of spectral tissue Doppler echocardiography (E/E' ratio as a noninvasive surrogate for left ventricular diastolic pressures in the diagnosis of heart failure with preserved left ventricular systolic function

    Roux Emmanuel

    2007-03-01

    Full Text Available Abstract Congestive heart failure with preserved left ventricular systolic function has emerged as a growing epidemic medical syndrome in developed countries, which is characterized by high morbidity and mortality rates. Rapid and accurate diagnosis of this condition is essential for optimizing the therapeutic management. The diagnosis of congestive heart failure is challenging in patients presenting without obvious left ventricular systolic dysfunction and additional diagnostic information is most commonly required in this setting. Comprehensive Doppler echocardiography is the single most useful diagnostic test recommended by the ESC and ACC/AHA guidelines for assessing left ventricular ejection fraction and cardiac abnormalities in patients with suspected congestive heart failure, and non-invasively determined basal or exercise-induced pulmonary capillary hypertension is likely to become a hallmark of congestive heart failure in symptomatic patients with preserved left ventricular systolic function. The present review will focus on the current clinical applications of spectral tissue Doppler echocardiography used as a reliable noninvasive surrogate for left ventricular diastolic pressures at rest as well as during exercise in the diagnosis of heart failure with preserved left ventricular systolic function. Chronic congestive heart failure, a disease of exercise, and acute heart failure syndromes are characterized by specific pathophysiologic and diagnostic issues, and these two clinical presentations will be discussed separately.

  10. Doppler derived quantitative flow estimate in coronary artery bypass graft: a computational multiscale model for the evaluation of the current clinical procedure.

    Ponzini, Raffaele; Lemma, Massimo; Morbiducci, Umberto; Montevecchi, Franco M; Redaelli, Alberto

    2008-09-01

    In order to investigate the reliability of the so called mean velocity/vessel area formula adopted in clinical practice for the estimation of the flow rate using an intravascular Doppler guide wire instrumentation, a multiscale computational model was used to give detailed predictions on flow profiles within Y-shaped coronary artery bypass graft (CABG) models. At this purpose three CABG models were built from clinical patient's data and used to evaluate and compare, in each model, the computed flow rate and the flow rate estimated according to the assumption of parabolic velocity profile. A consistent difference between the exact and the estimated value of the flow rate was found in every branch of all the graft models. In this study we showed that this discrepancy in the flow rate estimation is coherent to the theory of Womersley regarding spatial velocity profiles in unsteady flow conditions. In particular this work put in evidence that the error in flow rate estimation can be reduced by using the estimation formula recently proposed by Ponzini et al. [Ponzini R, Vergara C, Redaelli A, Veneziani A. Reliable CFD-based estimation of flow rate in haemodynamics measures. Ultrasound Med Biol 2006;32(10):1545-55], accounting for the unsteady nature of blood, applicable in the clinical practice without resorting to further measurements. PMID:17980641

  11. Differential doppler heterodyning technique

    Lading, Lars

    1971-01-01

    Measuring velocity without disturbing the moving object is possible by use of the laser doppler heterodyning technique. Theoretical considerations on the doppler shift show that the antenna property of the photodetector can solve an apparent conflict between two different ways of calculating the...

  12. Complex Doppler effect in left-handed metamaterials

    Ziemkiewicz, David

    2014-01-01

    The Doppler shift is investigated in one-dimensional system with moving source. Theoretical findings are confirmed in numerical simulations of optical and acoustical waves propagation in simple metamaterial model, showing the reversed shift and the existence of multiple frequency modes. The properties of these waves are discussed. The effect of absorption on the phenomenon is outlined.

  13. Doppler ultrasound in obstetrics and gynecology. 2. rev. and enl. ed.

    The second edition of Doppler Ultrasound in Obstetrics and Gynecology has been expanded and comprehensively updated to present the current standards of practice in Doppler ultrasound and the most recent developments in the technology. Doppler Ultrasound in Obstetrics and Gynecology encompasses the full spectrum of clinical applications of Doppler ultrasound for the practicing obstetrician-gynecologist, including the latest advances in 3D and color Doppler and the newest techniques in 4D fetal echocardiography. Written by preeminent experts in the field, the book covers the basic and physical principles of Doppler ultrasound; the use of Doppler for fetal examination, including fetal cerebral circulation; Doppler echocardiography of the fetal heart; and the use of Doppler for postdated pregnancy and in cases of multiple gestation. Chapters on the use of Doppler for gynecologic investigation include ultrasound in ectopic pregnancy, for infertility, for benign disorders and for gynecologic malignancies. (orig.)

  14. Doppler ultrasound in obstetrics and gynecology. 2. rev. and enl. ed.

    Maulik, D. [Winthrop Univ. Hospital, Mineola, NY (United States). Dept. of Obstetrics and Gynecology; Zalud, I. (eds.) [Kapiolani Medical Center for Women and Children, Honolulu, HI (United States)

    2005-07-01

    The second edition of Doppler Ultrasound in Obstetrics and Gynecology has been expanded and comprehensively updated to present the current standards of practice in Doppler ultrasound and the most recent developments in the technology. Doppler Ultrasound in Obstetrics and Gynecology encompasses the full spectrum of clinical applications of Doppler ultrasound for the practicing obstetrician-gynecologist, including the latest advances in 3D and color Doppler and the newest techniques in 4D fetal echocardiography. Written by preeminent experts in the field, the book covers the basic and physical principles of Doppler ultrasound; the use of Doppler for fetal examination, including fetal cerebral circulation; Doppler echocardiography of the fetal heart; and the use of Doppler for postdated pregnancy and in cases of multiple gestation. Chapters on the use of Doppler for gynecologic investigation include ultrasound in ectopic pregnancy, for infertility, for benign disorders and for gynecologic malignancies. (orig.)

  15. The Estimation and Compensation of Doppler Effect on Underwater Acoustic Spread Spectrum Communication%水声扩频通信中多普勒估计与补偿算法研究

    袁兆凯; 隋天宇; 李宇; 黄海宁

    2012-01-01

    The Doppler effect is inherent in communication systems which makes the carrier synchronization critical to the whole system. In underwater communication environment, the Doppler effect is more severe due to the limited sound speed. In this paper, the Doppler effect of underwater channel is analyzed by formulas on a software-defined radio communication system. Then an effective algorithm is developed which can estimate and compensate the frequency shift. The simulation results show that this algorithm works out within the speed of 15 m/s, when the signal to noise ratio is above -22 dB. The sea experimental results show that the system can successfully achieve the carry wave synchronization with the speed to be 6 knots.%通信系统普遍受多普勒效应影响,因而载波同步成为通信中的一项关键技术.在水声通信中,由于声速有限,信道中的多普勒效应的影响更为明显.该文在一个基于软件无线电机制的水声扩频通信系统中,对水声信道的多普勒效应进行分析和建模,并在此基础上提出了一种有效的水声扩频多普勒估计与补偿算法.仿真实验表明,算法能够在-22 dB的情况下有效地对15 m/s以内产生的多普勒频移进行估计与补偿.算法经过海试测试,在6节速度及加速减速过程中,系统均能够成功地完成载波同步.

  16. Ultrasonic Doppler methods to extract signatures of a walking human.

    Mehmood, Asif; Sabatier, James M; Damarla, Thyagaraju

    2012-09-01

    Extraction of Doppler signatures that characterize human motion has attracted a growing interest in recent years. These Doppler signatures are generated by various components of the human body while walking, and contain unique features that can be used for human detection and recognition. Although, a significant amount of research has been done in radio frequency regime for human Doppler signature extraction, considerably less has been done in acoustics. In this work, 40 kHz ultrasonic sonar is employed to measure the Doppler signature generated by the motion of body segments using different electronic and signal processing schemes. These schemes are based on both analog and digital demodulation with homodyne and heterodyne receiver circuitry. The results and analyses from these different schemes are presented. PMID:22979839

  17. OFDM for Underwater Acoustic Communication

    Thottappilly, Arjun

    2011-01-01

    Communicating wirelessly underwater has been an area of interest for researchers, engineers, and practitioners alike. One of the main reasons for the slow rate of progress in this area is that the underwater acoustic channel is in general much more hostile â in terms of multipath, frequency selectivity, noise, and the Doppler effect â than the over-the-air radio frequency channel. In this work a time warp based technique which can be used to model time-varying wideband Doppler shifts (as ...

  18. Ultrasonic colour Doppler imaging

    Evans, David H; Jensen, Jørgen Arendt; Nielsen, Michael Bachmann

    2011-01-01

    Ultrasonic colour Doppler is an imaging technique that combines anatomical information derived using ultrasonic pulse-echo techniques with velocity information derived using ultrasonic Doppler techniques to generate colour-coded maps of tissue velocity superimposed on grey-scale images of tissue...... weaknesses, perhaps the greatest being that in conventional systems, the velocities measured and thus displayed are the components of the flow velocity directly towards or away from the transducer, while ideally the method would give information about the magnitude and direction of the three-dimensional flow...... vectors. This review briefly introduces the principles behind colour Doppler imaging and describes some clinical applications. It then describes the basic components of conventional colour Doppler systems and the methods used to derive velocity information from the ultrasound signal. Next, a number of new...

  19. Cosmology with Doppler Lensing

    Bacon, David; Andrianomena, Sambatra; Clarkson, Chris; Bolejko, C.; Maartens, Roy

    2014-01-01

    Doppler lensing is the apparent change in object size and magnitude due to peculiar velocities. Objects falling into an overdensity appear larger on its near side, and smaller on its far side, than typical objects at the same redshifts. This effect dominates over the usual gravitational lensing magnification at low redshift. Doppler lensing is a promising new probe of cosmology, and we explore in detail how to utilize the effect with forthcoming surveys. We present cosmological simulations of...

  20. Rotational Doppler Effect

    Halder, Amit

    2002-01-01

    A monochromatic linear source of light is rotated with certain angular frequency and when such light is analysed after reflection then a change of frequency or wavelength may be observed depending on the location of the observer. This change of frequency or wavelength is different from the classical Doppler effect [1] or relativistic Doppler effect [2]. The reason behind this shift in wavelength is that a certain time interval observed by an observer in the rotating frame is different from th...

  1. Characteristics Analysis of HFM Signal over Underwater Acoustic Channels

    YUAN Fei

    2013-01-01

    Full Text Available For pulse compression characteristics and not easily affected by noise, linear frequency modulation signal are widely used in underwater acoustic communication. This paper analyzes the characteristics of hyperbolic frequency modulation signal over underwater acoustic channels. Compared with linear frequency modulation signal, hyperbolic frequency modulation has the same performance of strong anti-noise and anti-multipath, what’s more, hyperbolic frequency modulation signal is better resist the influence of doppler. And discussed the influence of doppler on signal, simulation results show that the hyperbolic frequency modulation signal detection rate is better than linear frequency modulation signal in the doppler environment.

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

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

    2016-01-01

    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 such as Euclid, SPHEREx and SKA, however, we show that the Doppler term must be included. The effect of t...

  3. Development of the doppler electron velocimeter: theory.

    Reu, Phillip L.

    2007-03-01

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

  4. Seasonal variation of a coastal jet in the Long Island Sound outflow region based on HF radar and Doppler current observations

    Ullman, D. S.; Codiga, D. L.

    2004-07-01

    Surface current (HF radar) and velocity profile observations, obtained as part of the Front-Resolving Observational Network with Telemetry (FRONT) project over an approximately 2-year period, are used to describe the seasonal variability of a coastal jet in the Long Island Sound outflow region. The jet is observed in an area of the continental shelf where surface thermal fronts are frequently detected during both summer and winter. The current jet is coincident with a band of high summer frontal probability, and apparently arises from the interaction between Long Island Sound outflow and larger-scale alongshore currents on the shelf. The jet reaches peak strength in summer (transport of ˜0.07 Sv) and is weak or non-existent in winter. Flow is strongest near the surface and weakens with depth, with only moderate seasonal variations in the vertical shear. The relatively long data set of currents combined with historical hydrographic measurements and buoy wind observations is analyzed to examine the seasonal variability of the terms in the depth-averaged momentum balance. The depth-averaged pressure gradient is partitioned into a steric component, evaluated from the hydrography, and a non-steric component that is estimated as the residual of the computed terms in the momentum equation. The depth-averaged momentum balance is found to be approximately geostrophic in the across-shore direction. The seasonal variability in the jet arises due to the shifting balance between buoyancy-driven flow that is always downshelf but intensifies somewhat in summer and wind-driven flow which dominates in winter when wind stress becomes strongly upwelling favorable.

  5. The electronic structure of BSCCO in the presence of a super-current: Flux-flow, Doppler shift and quasiparticle pockets

    Naamneh, M.; Campuzano, J. C.; Kanigel, A.

    2016-01-01

    There are several ways to turn a superconductor into a normal conductor: increase the temperature, apply a high magnetic field, or run a large current. High-T$_c$ cuprate superconductors are unusual in the sense that experiments suggest that destroying superconductivity by heating the sample to temperatures above T$_c$ or by applying a high magnetic field result in different 'normal' states. Spectroscopic probes show that above T$_c$, in the pseudogap regime, the Fermi surface is partly gappe...

  6. Ultrasonic Doppler Modes

    Tortoli, Piero; Fidanzati, Paolo; Luca, Bassi

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

  7. Doppler-suuntima-algoritmi

    Rekis, Matti

    2014-01-01

    Doppler-ilmiö aiheuttaa havaitsijan ja signaalilähteen välisen suhteellisen liikkeen seurauksena taajuusvääristymää lähteen alkuperäisestä signaalista. Tämä mm. doppler-siirtymäksi kutsuttu vääristymä voidaan havaita signaalilähteen taajuudessa, aallonpituudessa ja vaiheessa. Doppler-siirtymän suuruuteen ja suuntaan vaikuttaa se, kasvaako vai pieneneekö havaitsijan ja lähteen välinen etäisyys sekä niiden välinen suhteellinen nopeus. Tätä ilmiötä voidaan hyödyntää mm. radiolähettimen paikantam...

  8. Doppler cooling a microsphere

    Barker, P F

    2010-01-01

    Doppler cooling the center-of-mass motion of an optically levitated microsphere via the velocity dependent scattering force from narrow whispering gallery mode (WGM) resonances is described. Light that is red detuned from the WGM resonance can be used to damp the center-of-mass motion in a process analogous to the Doppler cooling of atoms. Leakage of photons out of the microsphere when the incident field is near resonant with the narrow WGM resonance acts to damp the motion of the sphere. The scattering force is not limited by saturation, but can be controlled by the incident power. Cooling times on the order of seconds are calculated for a 20 micron diameter silica microsphere trapped within optical tweezers, with a Doppler temperature limit in the microKelvin regime.

  9. Communication Acoustics

    Blauert, Jens

    Communication Acoustics deals with the fundamentals of those areas of acoustics which are related to modern communication technologies. Due to the advent of digital signal processing and recording in acoustics, these areas have enjoyed an enormous upswing during the last 4 decades. The book...... the book a source of valuable information for those who want to improve or refresh their knowledge in the field of communication acoustics - and to work their way deeper into it. Due to its interdisciplinary character Communication Acoustics is bound to attract readers from many different areas, such as......: acoustics, cognitive science, speech science, and communication technology....

  10. Ocean acoustic hurricane classification.

    Wilson, Joshua D; Makris, Nicholas C

    2006-01-01

    Theoretical and empirical evidence are combined to show that underwater acoustic sensing techniques may be valuable for measuring the wind speed and determining the destructive power of a hurricane. This is done by first developing a model for the acoustic intensity and mutual intensity in an ocean waveguide due to a hurricane and then determining the relationship between local wind speed and underwater acoustic intensity. From this it is shown that it should be feasible to accurately measure the local wind speed and classify the destructive power of a hurricane if its eye wall passes directly over a single underwater acoustic sensor. The potential advantages and disadvantages of the proposed acoustic method are weighed against those of currently employed techniques. PMID:16454274

  11. Doppler ion program description

    The Doppler spectrometer is a conventional Czerny-Turner grating spectrometer with a 1024 channel multiple detector. Light is dispersed across the detector, and its output yields a spectrum covering approximately 200 A. The width of the spectral peak is directly proportional to the temperature of the emitting ions, and determination of the impurity ion temperature allows one to infer the plasma ion temperature. The Doppler ion software system developed at General Atomic uses a TRACOR Northern 1710-31 and an LSI-11/2. The exact configuration of Doublet III is different from TRACOR Northern systems at other facilities

  12. Pulse Doppler radar

    Alabaster, Clive

    2012-01-01

    This book is a practitioner's guide to all aspects of pulse Doppler radar. It concentrates on airborne military radar systems since they are the most used, most complex, and most interesting of the pulse Doppler radars; however, ground-based and non-military systems are also included. It covers the fundamental science, signal processing, hardware issues, systems design and case studies of typical systems. It will be a useful resource for engineers of all types (hardware, software and systems), academics, post-graduate students, scientists in radar and radar electronic warfare sectors and milit

  13. Doppler Cooling a Microsphere

    Barker, P F

    2010-01-01

    Doppler cooling the center-of-mass motion of an optically levitated microsphere via the velocity dependent scattering force from narrow whispering gallery mode (WGM) resonances is described. Light that is red detuned from the WGM resonance can be used to damp the center-of-mass motion in a process analogous to the Doppler cooling of atoms. Leakage of photons out of the microsphere when the incident field is near resonant with the narrow WGM resonance acts to damp the motion of the sphere. The...

  14. Polarimetric Doppler Weather Radar

    Bringi, V. N.; Chandrasekar, V.

    2001-10-01

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

  15. Acoustic Neuroma

    An acoustic neuroma is a benign tumor that develops on the nerve that connects the ear to the brain. ... can press against the brain, becoming life-threatening. Acoustic neuroma can be difficult to diagnose, because the ...

  16. Acoustic Neuroma

    An acoustic neuroma is a benign tumor that develops on the nerve that connects the ear to the brain. The tumor ... press against the brain, becoming life-threatening. Acoustic neuroma can be difficult to diagnose, because the symptoms ...

  17. Doppler-musical instrument

    We propose a possible ultra-high energy resolution backscattering spectrometer optimized to spallation neutron source. A combination of multi monochromator crystal and Doppler drive provides considerable neutron flux, together with the reasonable energy range -30 < E < 30 μeV, even when the ultra-high energy resolution of ΔE∼0.03 μeV is attained. (author)

  18. Doppler electron velocimetry : notes on creating a practical tool.

    Reu, Phillip L.; Milster, Tom (University of Arizona)

    2008-11-01

    The Doppler electron velocimeter (DEV) has been shown to be theoretically possible. This report attempts to answer the next logical question: Is it a practical instrument? The answer hinges upon whether enough electrons are available to create a time-varying Doppler current to be measured by a detector with enough sensitivity and bandwidth. The answer to both of these questions is a qualified yes. A target Doppler frequency of 1 MHz was set as a minimum rate of interest. At this target a theoretical beam current signal-to-noise ratio of 25-to-1 is shown for existing electron holography equipment. A detector is also demonstrated with a bandwidth of 1-MHz at a current of 10 pA. Additionally, a Linnik-type interferometer that would increase the available beam current is shown that would offer a more flexible arrangement for Doppler electron measurements over the traditional biprism.

  19. Doppler echocardiographic measurement of flow velocity in the ascending aorta during supine and upright exercise.

    Daley, P J; Sagar, K B; Wann, L S

    1985-01-01

    Doppler echocardiography was used to measure stroke volume, peak flow velocity, and acceleration of flow in the ascending aorta in 10 healthy young volunteers during unlimited supine bicycle exercise and upright treadmill exercise. High quality studies were obtained in all subjects through the suprasternal notch acoustic window; there was no appreciable degradation in Doppler signal caused by interference by increased respiration or chest wall motion. Stroke volume index increased from 54 ml/...

  20. Accurate determination of the Boltzmann constant by Doppler spectroscopy: Towards a new definition of the kelvin

    Darquié, Benoît; Sow, Papa Lat Tabara; Lemarchand, Cyril; Triki, Meriam; Tokunaga, Sean; Bordé, Christian J; Chardonnet, Christian; Daussy, Christophe

    2015-01-01

    Accurate molecular spectroscopy in the mid-infrared region allows precision measurements of fundamental constants. For instance, measuring the linewidth of an isolated Doppler-broadened absorption line of ammonia around 10 $\\mu$m enables a determination of the Boltzmann constant k B. We report on our latest measurements. By fitting this lineshape to several models which include Dicke narrowing or speed-dependent collisional effects, we find that a determination of k B with an uncertainty of a few ppm is reachable. This is comparable to the best current uncertainty obtained using acoustic methods and would make a significant contribution to any new value of k B determined by the CODATA. Furthermore, having multiple independent measurements at these accuracies opens the possibility of defining the kelvin by fixing k B, an exciting prospect considering the upcoming redefinition of the International System of Units.

  1. Acoustic cloaking and transformation acoustics

    In this review, we give a brief introduction to the application of the new technique of transformation acoustics, which draws on a correspondence between coordinate transformation and material properties. The technique is formulated for both acoustic waves and linear liquid surface waves. Some interesting conceptual devices can be designed for manipulating acoustic waves. For example, we can design acoustic cloaks that make an object invisible to acoustic waves, and the cloak can either encompass or lie outside the object to be concealed. Transformation acoustics, as an analog of transformation optics, can go beyond invisibility cloaking. As an illustration for manipulating linear liquid surface waves, we show that a liquid wave rotator can be designed and fabricated to rotate the wave front. The acoustic transformation media require acoustic materials which are anisotropic and inhomogeneous. Such materials are difficult to find in nature. However, composite materials with embedded sub-wavelength resonators can in principle be made and such 'acoustic metamaterials' can exhibit nearly arbitrary values of effective density and modulus tensors to satisfy the demanding material requirements in transformation acoustics. We introduce resonant sonic materials and Helmholtz resonators as examples of acoustic metamaterials that exhibit resonant behaviour in effective density and effective modulus. (topical review)

  2. Acoustic cloaking and transformation acoustics

    Chen Huanyang [School of Physical Science and Technology, Soochow University, Suzhou, Jiangsu 215006 (China); Chan, C T, E-mail: kenyon@ust.h, E-mail: phchan@ust.h [Department of Physics and the William Mong Institute of NanoScience and Technology, The Hong Kong University of Science and Technology, Clear Water Bay (Hong Kong)

    2010-03-24

    In this review, we give a brief introduction to the application of the new technique of transformation acoustics, which draws on a correspondence between coordinate transformation and material properties. The technique is formulated for both acoustic waves and linear liquid surface waves. Some interesting conceptual devices can be designed for manipulating acoustic waves. For example, we can design acoustic cloaks that make an object invisible to acoustic waves, and the cloak can either encompass or lie outside the object to be concealed. Transformation acoustics, as an analog of transformation optics, can go beyond invisibility cloaking. As an illustration for manipulating linear liquid surface waves, we show that a liquid wave rotator can be designed and fabricated to rotate the wave front. The acoustic transformation media require acoustic materials which are anisotropic and inhomogeneous. Such materials are difficult to find in nature. However, composite materials with embedded sub-wavelength resonators can in principle be made and such 'acoustic metamaterials' can exhibit nearly arbitrary values of effective density and modulus tensors to satisfy the demanding material requirements in transformation acoustics. We introduce resonant sonic materials and Helmholtz resonators as examples of acoustic metamaterials that exhibit resonant behaviour in effective density and effective modulus. (topical review)

  3. Laser Doppler imaging, revisited

    Atlan, Michael; Gross, Michel

    2006-01-01

    International audience We present a detection scheme designed to perform laser Doppler imaging in a wide-field configuration, aimed at slow flows characterization. The optical field which carries a spectral information about the local scatterers dynamic state that results from momentum transfer at each scattering event, is analyzed in the temporal frequencies domain. The setup is based on heterodyne off-axis digital holography.

  4. Holographic laser Doppler ophthalmoscopy

    Simonutti, Manuel; Sahel, J A; Gross, Michel; Samson, Benjamin; Magnain, Caroline; Atlan, Michael; 10.1364/OL.35.001941

    2010-01-01

    We report laser Doppler ophthalmoscopic fundus imaging in the rat eye with near-IR heterodyne holography. Sequential sampling of the beat of the reflected radiation against a frequency-shifted optical local oscillator is made onto an array detector. Wide-field maps of fluctuation spectra in the 10 Hz to 25 kHz band exhibit angiographic contrasts in the retinal vascular tree without requirement of an exogenous marker.

  5. Quantitative Laser Doppler Flowmetry

    Fredriksson, Ingemar

    2009-01-01

    Laser Doppler flowmetry (LDF) is virtually the only non-invasive technique, except for other laser speckle based techniques, that enables estimation of the microcirculatory blood flow. The technique was introduced into the field of biomedical engineering in the 1970s, and a rapid evolvement followed during the 1980s with fiber based systems and improved signal analysis. The first imaging systems were presented in the beginning of the 1990s. Conventional LDF, although unique in many aspects an...

  6. CRED Ocean Data Platform (ODP), Acoustic Doppler Profiler (ADP); MHI, KAU; Long: -159.51350, Lat: 22.21593 (WGS84); Sensor Depth: 15.24m; Data Range: 20060914-20070420.

    National Oceanic and Atmospheric Administration, Department of Commerce — The Ocean Data Platform (ODP) is placed on the sea floor to measure water current profiles, waves, temperature and conductivity. The ODP consists of an upward...

  7. CRED Ocean Data Platform (ODP), Acoustic Doppler Profiler (ADP); PRIA, JAR; Long: -160.01553, Lat: -00.37917 (WGS84); Sensor Depth: 15.00m; Data Range: 20020311-20040325.

    National Oceanic and Atmospheric Administration, Department of Commerce — The Ocean Data Platform (ODP) is placed on the sea floor to measure water current profiles, waves, temperature and conductivity. The ODP consists of an upward...

  8. CRED Ocean Data Platform (ODP), Acoustic Doppler Profiler (ADP); NWHI, PHR; Long: -175.88110, Lat: 27.78209 (WGS84); Sensor Depth: 21.34m; Data Range: 20070806-20070912.

    National Oceanic and Atmospheric Administration, Department of Commerce — The Ocean Data Platform (ODP) is placed on the sea floor to measure water current profiles, waves, temperature and conductivity. The ODP consists of an upward...

  9. CRED Ocean Data Platform (ODP), Acoustic Doppler Profiler (ADP); PRIA, BAK; Long: -176.46025, Lat: 00.19005 (WGS84); Sensor Depth: 18.90m; Data Range: 20040123-20060130.

    National Oceanic and Atmospheric Administration, Department of Commerce — The Ocean Data Platform (ODP) is placed on the sea floor to measure water current profiles, waves, temperature and conductivity. The ODP consists of an upward...

  10. CRED Ocean Data Platform (ODP), Acoustic Doppler Profiler (ADP); NWHI, PHR; Long: -175.88112, Lat: 27.78204 (WGS84); Sensor Depth: 21.34m; Data Range: 20060922-20070805.

    National Oceanic and Atmospheric Administration, Department of Commerce — The Ocean Data Platform (ODP) is placed on the sea floor to measure water current profiles, waves, temperature and conductivity. The ODP consists of an upward...

  11. CRED Ocean Data Platform (ODP), Acoustic Doppler Profiler (ADP); AMSM, SWA; Long: -171.09092, Lat: -11.05848 (WGS84); Sensor Depth: 15.00m; Data Range: 20020227-20021207.

    National Oceanic and Atmospheric Administration, Department of Commerce — The Ocean Data Platform (ODP) is placed on the sea floor to measure water current profiles, waves, temperature and conductivity. The ODP consists of an upward...

  12. CRED Ocean Data Platform (ODP), Acoustic Doppler Profiler (ADP); NWHI, NEC; Long: -164.71215, Lat: 23.56792 (WGS84); Sensor Depth: 24.90m; Data Range: 20050411-20060903.

    National Oceanic and Atmospheric Administration, Department of Commerce — The Ocean Data Platform (ODP) is placed on the sea floor to measure water current profiles, waves, temperature and conductivity. The ODP consists of an upward...

  13. CRED Ocean Data Platform (ODP), Acoustic Doppler Profiler (ADP); PRIA, JAR; Long: -160.01547, Lat: -00.37915 (WGS84); Sensor Depth: 14.60m; Data Range: 20040327-20051016.

    National Oceanic and Atmospheric Administration, Department of Commerce — The Ocean Data Platform (ODP) is placed on the sea floor to measure water current profiles, waves, temperature and conductivity. The ODP consists of an upward...

  14. CRED Ocean Data Platform (ODP), Acoustic Doppler Profiler (ADP); PRIA, BAK; Long: -176.46025, Lat: 00.19005 (WGS84); Sensor Depth: 18.90m; Data Range: 20020201-20040122.

    National Oceanic and Atmospheric Administration, Department of Commerce — The Ocean Data Platform (ODP) is placed on the sea floor to measure water current profiles, waves, temperature and conductivity. The ODP consists of an upward...

  15. CRED Ocean Data Platform (ODP), Acoustic Doppler Profiler (ADP); NWHI, MID; Long: -177.42977, Lat: 28.23180 (WGS84); Sensor Depth: 29.26m; Data Range: 20060916-20080928.

    National Oceanic and Atmospheric Administration, Department of Commerce — The Ocean Data Platform (ODP) is placed on the sea floor to measure water current profiles, waves, temperature and conductivity. The ODP consists of an upward...

  16. CRED Ocean Data Platform (ODP), Acoustic Doppler Profiler (ADP); Guam, SRR; Long: 144.41784, Lat: 12.83819 (WGS84); Sensor Depth: 20.40m; Data Range: 20030929-20050908.

    National Oceanic and Atmospheric Administration, Department of Commerce — The Ocean Data Platform (ODP) is placed on the sea floor to measure water current profiles, waves, temperature and conductivity. The ODP consists of an upward...

  17. CRED Ocean Data Platform (ODP), Acoustic Doppler Profiler (ADP); PRIA, BAK; Long: -176.46012, Lat: 00.18994 (WGS84); Sensor Depth: 19.81m; Data Range: 20080210-20100130.

    National Oceanic and Atmospheric Administration, Department of Commerce — The Ocean Data Platform (ODP) is placed on the sea floor to measure water current profiles, waves, temperature and conductivity. The ODP consists of an upward...

  18. CRED Ocean Data Platform (ODP), Acoustic Doppler Profiler (ADP); Guam, SRR; Long: 144.41778, Lat: 12.83819 (WGS84); Sensor Depth: 20.42m; Data Range: 20051007-20070121.

    National Oceanic and Atmospheric Administration, Department of Commerce — The Ocean Data Platform (ODP) is placed on the sea floor to measure water current profiles, waves, temperature and conductivity. The ODP consists of an upward...

  19. CRED Ocean Data Platform (ODP), Acoustic Doppler Profiler (ADP); PRIA, BAK; Long: -176.46012, Lat: 00.18994 (WGS84); Sensor Depth: 18.80m; Data Range: 20060131-20080209.

    National Oceanic and Atmospheric Administration, Department of Commerce — The Ocean Data Platform (ODP) is placed on the sea floor to measure water current profiles, waves, temperature and conductivity. The ODP consists of an upward...

  20. Small-scale field-aligned currents and ionospheric disturbances induced by vertical acoustic resonance during the 2015 eruption of Chile's Calbuco volcano

    Aoyama, T.; Iyemori, T.; Nakanishi, K.; Nishioka, M.

    2015-12-01

    Wave packet structure of small-scale magnetic fluctuations were observed by SWARM satellites just above the volcano and it's magnetic conjugate point after the eruption of Chile's Calbuco volcano on April 22, 2015. These magnetic fluctuations in low and middle latitudes generated by small-scale field aligned currents (FACs), and have about 10-30 seconds period along the satellites' orbit [Nakanishi et al., 2014] and about 200 (340) seconds temporal scale for meridional (longitudinal) magnetic components [Iyemori et al., 2015]. We also observed ionospheric disturbances and ground geomagnetic fluctuations just after the eruption. The 4-min period oscillations of total electron content (TEC) were observed by GPS receivers near the volcano. The 260 and 215 seconds spectral peaks in D component of ground based geomagnetic observation were found. Such oscillations and spectral peaks didn't exist before the eruption. All of these observations may have the same origin, i.e., vertical acoustic resonance between the ionosphere and the ground. In this presentation, we estimate the propagation velocity of the TEC oscillations and the spatial scale of the disturbance region in the E-layer where the FACs are generated by the ionospheric dynamo.

  1. Acoustical Imaging

    Litniewski, Jerzy; Kujawska, Tamara; 31st International Symposium on Acoustical Imaging

    2012-01-01

    The International Symposium on Acoustical Imaging is a unique forum for advanced research, covering new technologies, developments, methods and theories in all areas of acoustics. This interdisciplinary Symposium has been taking place continuously since 1968. In the course of the years the proceedings volumes in the Acoustical Imaging Series have become a reference for cutting-edge research in the field. In 2011 the 31st International Symposium on Acoustical Imaging was held in Warsaw, Poland, April 10-13. Offering both a broad perspective on the state-of-the-art as well as  in-depth research contributions by the specialists in the field, this Volume 31 in the Series contains an excellent collection of papers in six major categories: Biological and Medical Imaging Physics and Mathematics of Acoustical Imaging Acoustic Microscopy Transducers and Arrays Nondestructive Evaluation and Industrial Applications Underwater Imaging

  2. Acoustic telemetry.

    Drumheller, Douglas Schaeffer; Kuszmaul, Scott S.

    2003-08-01

    Broadcasting messages through the earth is a daunting task. Indeed, broadcasting a normal telephone conversion through the earth by wireless means is impossible with todays technology. Most of us don't care, but some do. Industries that drill into the earth need wireless communication to broadcast navigation parameters. This allows them to steer their drill bits. They also need information about the natural formation that they are drilling. Measurements of parameters such as pressure, temperature, and gamma radiation levels can tell them if they have found a valuable resource such as a geothermal reservoir or a stratum bearing natural gas. Wireless communication methods are available to the drilling industry. Information is broadcast via either pressure waves in the drilling fluid or electromagnetic waves in the earth and well tubing. Data transmission can only travel one way at rates around a few baud. Given that normal Internet telephone modems operate near 20,000 baud, these data rates are truly very slow. Moreover, communication is often interrupted or permanently blocked by drilling conditions or natural formation properties. Here we describe a tool that communicates with stress waves traveling through the steel drill pipe and production tubing in the well. It's based on an old idea called Acoustic Telemetry. But what we present here is more than an idea. This tool exists, it's drilled several wells, and it works. Currently, it's the first and only acoustic telemetry tool that can withstand the drilling environment. It broadcasts one way over a limited range at much faster rates than existing methods, but we also know how build a system that can communicate both up and down wells of indefinite length.

  3. Mitigating Doppler shift effect in HF multitone data modem

    Sonlu, Yasar

    1989-09-01

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

  4. [Feasibility study of the Doppler exploration of the renal artery].

    Milon, P; Clavier, E; Genevois, A; Benozio, M

    1990-03-01

    Using arteriography as a reference, the authors investigate the feasibility of pulsed doppler exploration of the normal or pathological renal arteries in 46 successive patients. The poor sensitivity of pulsed doppler, mainly due to the considerable anatomical variations of the renal pedicle, does not currently allow using this technique for the detection of renal arterial stenosis. When combined with angiography, pulsed doppler becomes a definite asset in therapeutic radiology to help in the choice of a treatment and in follow-up. PMID:2191123

  5. Considerations pertinent to the Doppler effect for space reactors

    This paper describes various theoretical aspects pertinent to the estimation of the Doppler effect for space reactors. The distinct characteristics of space reactors give rise to various issues that are not present in the more thoroughly studied Doppler effect of fast breeder reactors. Key issues concerning the existing resonance data and computational models are extensively discussed. Calculations of the Doppler coefficient for a generic space reactor design having features of current designs have also been carried out to illustrate various aspects of practical importance

  6. The Antarctic Circumpolar Current between the Falkland Islands and South Georgia

    Arhan, M.; Naveira Garabato, AC.; Heywood, KJ; Stevens, DP

    2002-01-01

    Hydrographic and lowered acoustic Doppler current profiler data along a line from the Falkland Islands to South Georgia via the Maurice Ewing Bank are used to estimate the flow of circumpolar water into the Argentine Basin, and to study the interaction of the Antarctic Circumpolar Current with the Falkland Plateau. The estimated net transport of 129 ± 21 Sv (Sv = 106 m3 s-1) across the section is shared between three major current bands. One is associated with the Subantarctic Front (SAF; 52 ...

  7. TIDDBIT HF Doppler Sounder Measurements of TIDs During the Wallops Island Rocket Launch of October 2007

    Reynolds, A.; Crowley, G.; Rodrigues, F.; Earle, G.; Bullett, T.; Bishop, R.

    2008-12-01

    The TID Detector Built In Texas (TIDDBIT) sounder was deployed on the East Coast near Wallops Island to support a rocket launch in October 2007. The purpose of the rocket experiment was to study mid-latitude spread-F (MSF), and TIDDBIT provided information on the TID characteristics during the launch and for several days surrounding the launch. The sounder data confirm that waves were present during the rocket launch. This presentation reviews the TIDDBIT results from the experiment, contrasting data collected on different days, and from the same dates a year earlier. HF Doppler sounders represent a low-cost and low- maintenance solution for monitoring acoustic and gravity wave activity in the F-region ionosphere. HF Doppler sounders together with modern data analysis techniques provide both horizontal and vertical phase trace velocities across the entire TID spectrum from periods of 30-s to several hours. ASTRA has extensive experience with HF systems, and is currently building TIDDBIT sounders in New Mexico, and Peru.

  8. Laser doppler perfusion imaging

    Waardell, K.

    1992-01-01

    Recording of tissue perfusion is important in assessing the influence of peripheral vascular diseases on the microcirculation. This thesis reports on a laser doppler perfusion imager based on dynamic light scattering in tissue. When a low power He-Ne laser beam sequentally scans the tissue, moving blood cells generate doppler components in the back-scattered light. A fraction of this light is detected by a photodetector and converted into an electrical signal. In the processor, a signal proportional to the tissue perfusion at each measurement site is calculated and stored. When the scanning procedure is completed, a color-coded perfusion image is presented on a monitor. To convert important aspects of the perfusion image into more quantitative parameters, data analysis functions are implemented in the software. A theory describing the dependence of the distance between individual measurement points and detector on the system amplification factor is proposed and correction algorithms are presented. The performance of the laser doppler perfusion imager was evaluated using a flow simulator. A linear relationship between processor output signal and flow through the simulator was demonstrated for blood cell concentrations below 0.2%. The median sampling depth of the laser beam was simulated by a Monte Carlo technique and estimated to 235 {mu}m. The perfusion imager has been used in the clinic to study perfusion changes in port wine stains treated with argon laser and to investigate the intensity and extension of the cutaneous axon reflex response after electrical nerve stimulation. The fact that perfusion can be visualized without touching the tissue implies elimination of sterilization problems, thus simplifying clinical investigations of perfusion in association with diagnosis and treatment of peripheral vascular diseases. 22 refs.

  9. Laser doppler perfusion imaging

    Waardell, K.

    1992-11-01

    Recording of tissue perfusion is important in assessing the influence of peripheral vascular diseases on the microcirculation. This thesis reports on a laser doppler perfusion imager based on dynamic light scattering in tissue. When a low power He-Ne laser beam sequentally scans the tissue, moving blood cells generate doppler components in the back-scattered light. A fraction of this light is detected by a photodetector and converted into an electrical signal. In the processor, a signal proportional to the tissue perfusion at each measurement site is calculated and stored. When the scanning procedure is completed, a color-coded perfusion image is presented on a monitor. To convert important aspects of the perfusion image into more quantitative parameters, data analysis functions are implemented in the software. A theory describing the dependence of the distance between individual measurement points and detector on the system amplification factor is proposed and correction algorithms are presented. The performance of the laser doppler perfusion imager was evaluated using a flow simulator. A linear relationship between processor output signal and flow through the simulator was demonstrated for blood cell concentrations below 0.2%. The median sampling depth of the laser beam was simulated by a Monte Carlo technique and estimated to 235 {mu}m. The perfusion imager has been used in the clinic to study perfusion changes in port wine stains treated with argon laser and to investigate the intensity and extension of the cutaneous axon reflex response after electrical nerve stimulation. The fact that perfusion can be visualized without touching the tissue implies elimination of sterilization problems, thus simplifying clinical investigations of perfusion in association with diagnosis and treatment of peripheral vascular diseases. 22 refs.

  10. Laser doppler perfusion imaging

    Recording of tissue perfusion is important in assessing the influence of peripheral vascular diseases on the microcirculation. This thesis reports on a laser doppler perfusion imager based on dynamic light scattering in tissue. When a low power He-Ne laser beam sequentally scans the tissue, moving blood cells generate doppler components in the back-scattered light. A fraction of this light is detected by a photodetector and converted into an electrical signal. In the processor, a signal proportional to the tissue perfusion at each measurement site is calculated and stored. When the scanning procedure is completed, a color-coded perfusion image is presented on a monitor. To convert important aspects of the perfusion image into more quantitative parameters, data analysis functions are implemented in the software. A theory describing the dependence of the distance between individual measurement points and detector on the system amplification factor is proposed and correction algorithms are presented. The performance of the laser doppler perfusion imager was evaluated using a flow simulator. A linear relationship between processor output signal and flow through the simulator was demonstrated for blood cell concentrations below 0.2%. The median sampling depth of the laser beam was simulated by a Monte Carlo technique and estimated to 235 μm. The perfusion imager has been used in the clinic to study perfusion changes in port wine stains treated with argon laser and to investigate the intensity and extension of the cutaneous axon reflex response after electrical nerve stimulation. The fact that perfusion can be visualized without touching the tissue implies elimination of sterilization problems, thus simplifying clinical investigations of perfusion in association with diagnosis and treatment of peripheral vascular diseases. 22 refs

  11. Acoustic engineering and technology '90

    Acoustic monitoring, testing and diagnosis in machines, production processes and products enhance the uptimes and profitability of machinery and plants. 18 papers discuss the current state of the art of acoustic monitoring systems including integrated factory planning as well as industrial health, and noise protection. (DG)

  12. Single mode, extreme precision Doppler spectrographs

    Schwab, Christian; Leon-Saval, Sergio G.; Betters, Christopher H.; Bland-Hawthorn, Joss; Mahadevan, Suvrath

    2012-01-01

    The 'holy grail' of exoplanet research today is the detection of an earth-like planet: a rocky planet in the habitable zone around a main-sequence star. Extremely precise Doppler spectroscopy is an indispensable tool to find and characterize earth-like planets; however, to find these planets around solar-type stars, we need nearly one order of magnitude better radial velocity (RV) precision than the best current spectrographs provide. Recent developments in astrophotonics (Bland-Hawthorn & Ho...

  13. Radiation acoustics

    Lyamshev, Leonid M

    2004-01-01

    Radiation acoustics is a developing field lying at the intersection of acoustics, high-energy physics, nuclear physics, and condensed matter physics. Radiation Acoustics is among the first books to address this promising field of study, and the first to collect all of the most significant results achieved since research in this area began in earnest in the 1970s.The book begins by reviewing the data on elementary particles, absorption of penetrating radiation in a substance, and the mechanisms of acoustic radiation excitation. The next seven chapters present a theoretical treatment of thermoradiation sound generation in condensed media under the action of modulated penetrating radiation and radiation pulses. The author explores particular features of the acoustic fields of moving thermoradiation sound sources, sound excitation by single high-energy particles, and the efficiency and optimal conditions of thermoradiation sound generation. Experimental results follow the theoretical discussions, and these clearl...

  14. High-Frequency Seafloor Acoustics

    Jackson, Darrell R

    2007-01-01

    High-Frequency Seafloor Acoustics is the first book in a new series sponsored by the Office of Naval Research on the latest research in underwater acoustics. This exciting new title provides ready access to experimental data, theory, and models relevant to high-frequency seafloor acoustics and will be of interest to sonar engineers and researchers working in underwater acoustics. The physical characteristics of the seafloor affecting acoustic propagation and scattering are covered, including physical and geoacoustic properties and surface roughness. Current theories for acoustic propagation in sediments are presented along with corresponding models for reflection, scattering, and seafloor penetration. The main text is backed up by an extensive bibliography and technical appendices.

  15. Acoustic and optical variations during rapid downward motion episodes in the deep north-western Mediterranean Sea

    van Haren, H; Aguilar, J A; Albert, A; Anghinolfi, M; Anton, G; Anvar, S; Ardid, M; Jesus, A C Assis; Astraatmadja, T; Aubert, J -J; Auer, R; Baret, B; Basa, S; Bazzotti, M; Bertin, V; Biagi, S; Bigongiari, C; Bou-Cabof, M; Bouwhuis, M C; Brown, A; Brunner, J; Busto, J; Camarena, F; Capone, A; Carminati, G; Carr, J; Castel, D; Castorina, E; Cavasinni, V; Cecchini, S; Charvis, Ph; Chiarusi, T; Circella, M; Coniglione, R; Costantini, H; Cottini, N; Coyleh, P; Curtil, C; De Bonis, G; Decowski, M P; Dekeyser, I; Deschamps, A; Distefano, C; Donzaud, C; Dornic, D; Drouhin, D; Eberl, T; Emanuele, U; Ernenwein, J -P; Escoffier, S; Fehr, F; Flaminio, V; Fratini, K; Fritsch, U; Fuda, J -L; Giacomelli, G; Gómez-González, J P; Graf, K; Guillard, G; Halladjian, G; Hallewell, G; Heijboer, A J; Hello, Y; Hernández-Rey, J J; Hößl, J; de Jong, M; Kalantar-Nayestanakia, N; Kalekin, O; Kappes, A; Katz, U; Kooijman, P; Kopper, C; Kouchner, A; Kretschmer, W; Lahmann, R; Lamare, P; Lambard, G; Laros, G; Laschinsky, H; Lefèvre, D; Lelaizant, G; Lim, G; Presti, D Lo; Loehner, H; Loucatos, S; Lucarelli, F; Lyons, K; Mangano, S; Marcelin, M; Margiotta, A; Martinez-Mora, J A; Maurin, G; Mazure, A; Melissas, M; Montaruli, T; Morganti, M; Moscoso, L; Motz, H; Naumann, C; Neff, M; Ostasch, R; Palioselitis, G; Păvălaş, G E; Payre, P; Petrovic, J; Piattelli, P; Picot-Clemente, N; Picqu, C; Pillet, R; Popa, V; Pradier, T; Presani, E; Racca, C; Radu, A; Reed, C; Riccobene, G; Richardt, C; Rujoiu, M; Russo, G V; Sales, F; Schoeck, F; Schuller, J -P; Shanidze, R; Simeone, F; Spurio, M; Steijger, J J M; Stolarczyk, Th; Tamburini, C; Tasca, L; Toscano, S; Vallage, B; Van Elewyck, V; Vecchi, M; Vernin, P; Wijnker, G; de Wolf, E; Yepes, H; Zaborov, D; Zornoza, J D; Zúñiga, J

    2011-01-01

    An Acoustic Doppler Current Profiler (ADCP) was moored at the deep-sea site of the ANTARES neutrino telescope near Toulon, France, thus providing a unique opportunity to compare high-resolution acoustic and optical observations between 70 and 170 m above the sea bed at 2475 m. The ADCP measured downward vertical currents of magnitudes up to 0.03 m s-1 in late winter and early spring 2006. In the same period, observations were made of enhanced levels of acoustic reflection, interpreted as suspended particles including zooplankton, by a factor of about 10 and of horizontal currents reaching 0.35 m s-1. These observations coincided with high light levels detected by the telescope, interpreted as increased bioluminescence. During winter 2006 deep dense-water formation occurred in the Ligurian subbasin, thus providing a possible explanation for these observations. However, the 10-20 days quasi-periodic episodes of high levels of acoustic reflection, light and large vertical currents continuing into the summer are ...

  16. Doppler speedometer for micro-organisms

    Objective of Investigations: Development and creation of the Doppler speedometer for micro-organisms which allows to evaluate, in a real temporal scale, variations in the state of water suspension of micro-organisms under the effect of chemical, physical and other external actions. Statement of the Problem The main problem is absence of reliable, accessible for users and simple, in view of application, Doppler speedometers for micro-organisms. Nevertheless, correlation Doppler spectrometry in the regime of heterodyning the supporting and cell-scattered laser radiation is welt known. The main idea is that the correlation function of photo-current pulses bears an information on the averages over the assembly of cell velocities. For solving the biological problems, construction of auto-correlation function in the real-time regime with the delay time values comprising, function in the real-time regime with the delay time values comprising, nearly, 100 me (10 khz) or higher is needed. Computers of high class manage this problem using but the program software. Due to this, one can simplify applications of the proposed techniques provided he creates the Doppler speedometer for micro-organism on a base of the Pentium. Expected Result Manufactured operable mock-up of the Doppler speedometer for micro-organisms in a form of the auxiliary computer block which allows to receive an information, in the real time scale, on the results of external effects of various nature on the cell assembly in transparent medium with a small volume of the studied cell suspension

  17. Myocardial Strain and Strain Rate Imaging: Comparison between Doppler Derived Strain Imaging and Speckle Tracking Echocardiography

    Anita Sadeghpour

    2013-05-01

    Full Text Available Regional myocardial function has been traditionally assessed by visual estimation (1. Echocardiographic strain imaging which is known as deformation imaging, has been emerged as a quantitative technique to accurately estimate regional myocardial function and contractility. Currently, strain imaging has been regarded as a research tool in the most echocardiography laboratories. However, in recent years, strain imaging has gain momentum in daily clinical practice (2. The following two techniques have dominated the research arena of echocardiography: (1 Doppler based tissue velocity measurements, frequently referred to tissue Doppler or myocardial Doppler, and (2 speckle tracking on the basis of displacement measurements (3. Over the past two decades, Tissue Doppler Imaging (TDI and Doppler –derived strain (S and strain rate (SR imaging were introduced to quantify regional myocardial function. However, Doppler–derived strain variables faced criticisms, with regard to the angle dependency, noise interference, and substantial intraobserver and interobserver variability. The angle dependency is the major weakness of Doppler based methodology; however, it has the advantage of online measurements of velocities and time intervals with excellent temporal resolution, which is essential for the assessment of ischemia (4. Speckle-tracking echocardiography (STE or Non Doppler 2D strain echocardiography is a relatively new, largely angle-independent technique that analyzes motion by tracking natural acoustic reflections and interference patterns within an ultrasonic window. The image-processing algorithm tracks elements with approximately 20 to 40 pixels containing stable patterns and are described as ‘‘speckles’’ or ‘‘fingerprints’’. The speckles seen in grayscale B-mode (2D images are tracked consecutively frame to frame (5, 6. Assessment of 2D strain by STE is a semiautomatic method that requires definition of the myocardium

  18. ANL Doppler flowmeter

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

    1985-10-01

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

  19. Trapping of superfluid persistent currents in superleaks

    Persistent currents in superleaks in contact with bulk superfluid helium have been investigated using Doppler shifts of the acoustic modes of an annular resonator partially packed with superleak and with a simple gyroscopic technique. In an annulus in which the bottom fraction is packed with fine powder and the upper part is left unpacked, there are two hybrid acoustic modes consisting of a combination of the three bulk sounds of superfluid helium, first, second and fourth sound. One mode, with velocity C/sub II/, consists of second sound modified by the presence of the superleak. The other mode, with velocity C14, is an interpolated first and fourth sound mode. The two modes have been studied between the temperatures 1.20K and the lambda temperature for annuli 20, 40, 60 and 80 percent filled with superleak. The velocities obtained were compared with the predictions of the two fluid hydrodynamic theory and good agreement was found. The doppler shifts of C/sub II/ and C14 were used to obtain the persistent current velocities in the unpacked or free section and the packed region of the resonator. It is found that the persistent current velocity in the powder is about the same as is found in a fully packed annulus. The decay of the observed persistent currents was observed for various initial velocities. These observations are discussed in terms of the vortex configurations in the annulus. Vortices form a sheath or cage on the surface of the superleak and prevent loss of angular momentum from the persistent current in the superleak. The arguments are extended to the case of a superleak without walls--a bare superleak--and it is shown that in this case the vortices close on themselves to form a cage to contain the current. Observations were made on a bare superleak by using a simple gyroscopic apparatus suspended from a torsion wire

  20. Doppler Beats or Interference Fringes?

    Kelly, Paul S.

    1979-01-01

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

  1. Cooperative OFDM underwater acoustic communications

    Cheng, Xilin; Cheng, Xiang

    2016-01-01

    Following underwater acoustic channel modeling, this book investigates the relationship between coherence time and transmission distances. It considers the power allocation issues of two typical transmission scenarios, namely short-range transmission and medium-long range transmission. For the former scenario, an adaptive system is developed based on instantaneous channel state information. The primary focus is on cooperative dual-hop orthogonal frequency division multiplexing (OFDM). This book includes the decomposed fountain codes designed to enable reliable communications with higher energy efficiency. It covers the Doppler Effect, which improves packet transmission reliability for effective low-complexity mirror-mapping-based intercarrier interference cancellation schemes capable of suppressing the intercarrier interference power level. Designed for professionals and researchers in the field of underwater acoustic communications, this book is also suitable for advanced-level students in electrical enginee...

  2. Laser Doppler measurement of cutaneous blood flow

    Laser Doppler velocimetry is an instrument system which has only recently been applied to the evaluation and quantitation of perfusion in the micro-vascular bed. The instrument is based on the Doppler principle, but uses low power laser light rather than the more commonly used ultrasound, and has a sample volume of approximately 1 mm/sup 3/. As it is non-invasive, it can be used on any skin surface or exposed microvascular bed and provides a continuous semi-quantitative measure of microcirculatory perfusion, it has a number of advantages as compared to other cutaneous blood flow measurement techniques. Initial studies have shown that it is easily used, and it has demonstrated good correlation with both xenon radio-isotope clearance and microsphere deposition techniques. Areas of current evaluation and utilization are in most major areas of medicine and surgery and include plastic, vascular and orthopaedic surgery, dermatology, gastro-enterology, rheumatology, burns and anaesthesiology

  3. Low-Frequency Gravitational Wave Searches Using Spacecraft Doppler Tracking

    Armstrong J. W.

    2006-01-01

    Full Text Available This paper discusses spacecraft Doppler tracking, the current-generation detector technology used in the low-frequency (~millihertz gravitational wave band. In the Doppler method the earth and a distant spacecraft act as free test masses with a ground-based precision Doppler tracking system continuously monitoring the earth-spacecraft relative dimensionless velocity $2 Delta v/c = Delta u/ u_0$, where $Delta u$ is the Doppler shift and $ u_0$ is the radio link carrier frequency. A gravitational wave having strain amplitude $h$ incident on the earth-spacecraft system causes perturbations of order $h$ in the time series of $Delta u/ u_0$. Unlike other detectors, the ~1-10 AU earth-spacecraft separation makes the detector large compared with millihertz-band gravitational wavelengths, and thus times-of-flight of signals and radio waves through the apparatus are important. A burst signal, for example, is time-resolved into a characteristic signature: three discrete events in the Doppler time series. I discuss here the principles of operation of this detector (emphasizing transfer functions of gravitational wave signals and the principal noises to the Doppler time series, some data analysis techniques, experiments to date, and illustrations of sensitivity and current detector performance. I conclude with a discussion of how gravitational wave sensitivity can be improved in the low-frequency band.

  4. Adaptive Spectral Doppler Estimation

    Gran, Fredrik; Jakobsson, Andreas; Jensen, Jørgen Arendt

    2009-01-01

    In this paper, 2 adaptive spectral estimation techniques are analyzed for spectral Doppler ultrasound. The purpose is to minimize the observation window needed to estimate the spectrogram to provide a better temporal resolution and gain more flexibility when designing the data acquisition sequence....... The methods can also provide better quality of the estimated power spectral density (PSD) of the blood signal. Adaptive spectral estimation techniques are known to pro- vide good spectral resolution and contrast even when the ob- servation window is very short. The 2 adaptive techniques are tested and...... compared with the averaged periodogram (Welch’s method). The blood power spectral capon (BPC) method is based on a standard minimum variance technique adapted to account for both averaging over slow-time and depth. The blood amplitude and phase estimation technique (BAPES) is based on finding a set of...

  5. Acoustical Imaging

    Akiyama, Iwaki

    2009-01-01

    The 29th International Symposium on Acoustical Imaging was held in Shonan Village, Kanagawa, Japan, April 15-18, 2007. This interdisciplinary Symposium has been taking place every two years since 1968 and forms a unique forum for advanced research, covering new technologies, developments, methods and theories in all areas of acoustics. In the course of the years the volumes in the Acoustical Imaging Series have developed and become well-known and appreciated reference works. Offering both a broad perspective on the state-of-the-art in the field as well as an in-depth look at its leading edge research, this Volume 29 in the Series contains again an excellent collection of seventy papers presented in nine major categories: Strain Imaging Biological and Medical Applications Acoustic Microscopy Non-Destructive Evaluation and Industrial Applications Components and Systems Geophysics and Underwater Imaging Physics and Mathematics Medical Image Analysis FDTD method and Other Numerical Simulations Audience Researcher...

  6. Acoustic telemetry

    National Oceanic and Atmospheric Administration, Department of Commerce — To determine movements of green turtles in the nearshore foraging areas, we deployed acoustic tags and determined their movements through active and passive...

  7. Acoustics Research

    National Oceanic and Atmospheric Administration, Department of Commerce — Fisheries acoustics data are collected from more than 200 sea-days each year aboard the FRV DELAWARE II and FRV ALBATROSS IV (decommissioned) and the FSV Henry B....

  8. Battlefield acoustics

    Damarla, Thyagaraju

    2015-01-01

    This book presents all aspects of situational awareness in a battlefield using acoustic signals. It starts by presenting the science behind understanding and interpretation of sound signals. The book then goes on to provide various signal processing techniques used in acoustics to find the direction of sound source, localize gunfire, track vehicles, and detect people. The necessary mathematical background and various classification and fusion techniques are presented. The book contains majority of the things one would need to process acoustic signals for all aspects of situational awareness in one location. The book also presents array theory, which is pivotal in finding the direction of arrival of acoustic signals. In addition, the book presents techniques to fuse the information from multiple homogeneous/heterogeneous sensors for better detection. MATLAB code is provided for majority of the real application, which is a valuable resource in not only understanding the theory but readers, can also use the code...

  9. Reverberant Acoustic Test Facility (RATF)

    Federal Laboratory Consortium — The very large Reverberant Acoustic Test Facility (RATF) at the NASA Glenn Research Center (GRC), Plum Brook Station, is currently under construction and is due to...

  10. Strong acoustic wave action

    Gokhberg, M. B.

    1983-07-01

    Experiments devoted to acoustic action on the atmosphere-magnetosphere-ionosphere system using ground based strong explosions are reviewed. The propagation of acoustic waves was observed by ground observations over 2000 km in horizontal direction and to an altitude of 200 km. Magnetic variations up to 100 nT were detected by ARIEL-3 satellite near the epicenter of the explosion connected with the formation of strong field aligned currents in the magnetosphere. The enhancement of VLF emission at 800 km altitude is observed.

  11. Holographic imaging of surface acoustic waves

    Bruno, Francois; Royer, Daniel; Atlan, Michael

    2014-01-01

    We report on an experimental demonstration of surface acoustic waves monitoring on a thin metal plate with heterodyne optical holography. Narrowband imaging of local optical pathlength modulation is achieved with a frequency-tunable time-averaged laser Doppler holographic imaging scheme on a sensor array, at video-rate. This method enables robust and quantitative mapping of out-of-plane vibrations of nanometric amplitudes at radiofrequencies.

  12. Wayside Bearing Fault Diagnosis Based on a Data-Driven Doppler Effect Eliminator and Transient Model Analysis

    Fang Liu; Changqing Shen; Qingbo He; Ao Zhang; Yongbin Liu; Fanrang Kong

    2014-01-01

    A fault diagnosis strategy based on the wayside acoustic monitoring technique is investigated for locomotive bearing fault diagnosis. Inspired by the transient modeling analysis method based on correlation filtering analysis, a so-called Parametric-Mother-Doppler-Wavelet (PMDW) is constructed with six parameters, including a center characteristic frequency and five kinematic model parameters. A Doppler effect eliminator containing a PMDW generator, a correlation filtering analysis module, ...

  13. Feasability of a ARFI/B-mode/Doppler system for real-time, freehand scanning of the cardiovascular system

    Dumont, Douglas M.; Lee, Seung-Yun; Doherty, Joshua R.; Trahey, Gregg E.

    2011-03-01

    Acoustic radiation force impulse (ARFI) imaging has been previously described for the visualization of the cardiovascular system, including assessment of cerebral and lower-limb vascular disease, myocardial function, and cardiac RF ablation monitoring. Given that plaque imposes a 3-dimensional burden on the artery and that accurate visualization of all lesion borders are important for ablation guidance, it would be convenient if an entire plaque or lesion volume could be acquired, either using a 3D system or 2D freehand scanning. Currently, ARFI imaging uses single-frame acquisition, with acquisition times ranging from 100-200ms. Such a system would be cumbersome for real-time, freehand scanning. In this work, we evaluate the feasibility of using ARFI for freehand, real-time scanning of the cardiovascular system. New techniques are presented which acquire B-mode / ARFI/ and Color-flow Doppler (BACD) information in less than 50 ms. Freehand feasibility is evaluated by sweeping the BACD system across lesion phantoms and vascular phantoms modeling a thin-cap fibroatheroma at sweep rates currently utilized in conventional B-mode systems. Stationary in vivo BACD images were then formed from the carotid artery of a canine model, demonstrating the system's potential. The results suggest that little loss in either ARFI or Doppler quality occurs during translational-stage controlled, quasi-freehand sweeps.

  14. High-frequency Doppler ultrasound transducer for the peripheral circulatory system

    Bae, Youngmin; Yang, Jeongwon; Kang, Uk; Kim, Guanghoon [Korea Electrotechnology Research Institute, Ansan (Korea, Republic of)

    2011-12-15

    A Doppler ultrasound transducer was designed and implemented to measure the blood flow velocity in tiny vessels near the skin of hands or feet. The geometric parameters of the transducer for defining the observation volume were derived and implemented with an acoustic window made of polystyrene. The observation volume designed in this study was located 6.5 mm from the transducer, which was comparable to the value predicted geometrically. The two-way insertion loss of the transducer was -11.3 dB on ultrasound frequency of 20 MHz, and the 3-dB bandwidth was approximately 2 MHz. In addition, the Doppler shift in the frequency measured by using a Doppler device composed of the transducer and a Doppler signal processing unit was proportional to the flow velocity generated by a homemade flowing system. Finally, we concluded that the transducer could be applied to measure the blood flow velocity in hands or feet.

  15. How to study the Doppler effect with Audacity software

    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.

  16. High Resolution Doppler Lidar

    1996-01-01

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

  17. Wind climatology observed over Kalpakkam using Doppler sodar

    Acoustic remote sensing of the prevailing winds in the boundary layer finds an important application in studying the problems related to air pollution meteorology. Analysis of the seasonal variation of vertical and horizontal wind speed with altitude is made using the Doppler sodar data collected at an atomic research centre, Kalpakkam. A pictorial representation of horizontal wind flow for each season is given in the form of wind roses at three lower levels of probing, namely 100, 300 and 500 m. Such analysis would prove to be a basic reference material for taking necessary meaningful emergency measures in similar climatic regions. (author). 18 refs., 10 figs

  18. Acoustic emission

    This paper is related to our activities on acoustic emission (A.E.). The work is made with different materials: metals and fibre reinforced plastics. At present, acoustic emission transducers are being developed for low and high temperature. A test to detect electrical discharges in electrical transformers was performed. Our experience in industrial tests to detect cracks or failures in tanks or tubes is also described. The use of A.E. for leak detection is considered. Works on pattern recognition of A.E. signals are also being performed. (Author)

  19. Study of bed load measurement with Acoustic Doppler Current Profiler in Yantze River estuary%基于ADCP的长江口推移质运动遥测技术研究

    胡浩; 程和琴; 杨忠勇; 计娜

    2014-01-01

    利用ADCP底跟踪技术遥测了长江河口北港段推移质运动过程,并对推移质运动状态进行了分段研究。结果表明:无推移质运动状态下,测量误差主要受近底悬沙影响,推移质流速沿水流方向被高估;部分推移质运动状态下,推移质运动视速度与垂线平均流速呈指数相关;普遍推移质运动状态下,两者线性相关显著,且推移质运动速度误差将随流速变化而改变,测量精度主要受脉冲长度和近底悬沙影响。基于ADCP测量数据的推移质单宽输沙率公式合理有效,可以用于河口推移质输沙率的快速定量。%ADCP was used to measure the bed load transport process in Beigang Channel of Yantze River estuary and the bed load transport status in different stages was studied. The results show that if there is no bed load transport, the measuring error was influenced by suspended load near bed and the movement velocity of bed load in the flow direction is over estimated;if there is partial bed load transport, the apparent velocity of bed load has exponential correlation with mean velocity in vertical;if there is much bed load transport, the apparent velocity of bed load and mean velocity in vertical is in obvious linear correlation, and the error of apparent velocity varies with flow velocity. However, the measurement accuracy is mainly affected by the pulse range and the near-bottom suspended sediment. The formula of bed load transport rate per unit width measured by ADCP is reasona-ble, which can be used to rapidly determine the bed load transport rate in Yantze River estuary.

  20. Hull-Mounted (shipboard) Acoustic Doppler Current Profiler (ADCP) data collected during shipboard surveys during 2010 and 2011 in Vieques Sound, Virgin Passage and surrounding regions (NODC Accession 0088063)

    National Oceanic and Atmospheric Administration, Department of Commerce — Teledyne RD Instruments Ocean Surveyor 150kHz and Workhorse 300kHz ADCPs were utilized during cruises conducted between March 2010 and April 2011 in Vieques Sound,...

  1. Acoustic doppler current meter data collected in support of the Minerals Management Service-supported Deep Water Program in the the Gulf of Mexico, 1999 - 2003 (NODC Accession 0002196)

    National Oceanic and Atmospheric Administration, Department of Commerce — A research program has been initiated by the Minerals Management Service (Contract No. 1435-01-99-CT-30991) to gain better knowledge of the benthic communities of...

  2. Use of a tethersonde measurement system to conduct a Doppler SODAR performance audit

    Wilkerson, G.W. [North American Weather Consultants, Salt Lake City, UT (United States); Catizone, P.A. [TRC Environmental Corp., Windsor, CT (United States); Coble, T.D. [ASARCO Inc., East Helena, MT (United States)

    1994-12-31

    With the increased usage of dispersion models that require stack top wind information, such as the Complex Terrain Dispersion Model (CTDM), the need for a reliable method to collect elevated wind data has also increased. Doppler Sound Detection and Ranging (SODAR) instruments have gained recognition as a viable means of collecting such data. SODAR technology has improved greatly over the last decade and is now a cost effective alternative to tall meteorological towers. SODARs are remote sensing devices that sample the atmosphere and calculate wind speed and wind direction data at different altitudes. This is accomplished by measuring the doppler shift of an acoustic pulse emitted by a ground level antenna.

  3. Planetary Doppler Imaging

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

    2014-12-01

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

  4. Doppler evaluation of valvular regurgitation

    The many examples described in this chapter show that there are several major points to keep in mind when examining patients for the presence of valvular insufficiency. One practical point not previously emphasized is that the audible output may be more sensitive than the spectral display. It is not infrequent that a given lesion is heard by audio but cannot be adequately recorded on the spectral hard copy. Interpretation in these cases is often difficult and, in our experience, usually involves a tradeoff. Accepting audio evidence of a regurgitant lesion without hard-copy confirmation increases the sensitivity of the procedure but will also result in an increased number of false-positive diagnoses. Currently, we require hard-copy confirmation before we will report definite evidence of valvular regurgitation. Second, it is important for the operator to take time to search for small regurgitant jets. When searching for insufficiency by pulsed wave with an instrument that has a variable sample volume size, one should not routinely begin the examination with a sample volume size that is as large as possible. Although this may seem desirable for locating small jets, the operator must remember that this process will frequently result in a loss of system sensitivity. Third, the opertor should expect regurgitant jets to exceed a velocity of 1.5m/sec and result in aliasing when in pulsed wave mode. This is certainly true in most adults, since regurgitant lesions are located far enough away from the transducer to cause the Nyquist limit to be exceeded. Thus, in almost every instance, pulsed Doppler operators should expect aliasing of regurgitant lesion. Fourth, particularly beginners should be prepared to switch back and forth between pulsed and continuous wave modes

  5. Inverse Doppler Effects in Flute

    Zhao, Xiao P; Liu, Song; Shen, Fang L; Li, Lin L; Luo, Chun R

    2015-01-01

    Here we report the observation of the inverse Doppler effects in a flute. It is experimentally verified that, when there is a relative movement between the source and the observer, the inverse Doppler effect could be detected for all seven pitches of a musical scale produced by a flute. Higher tone is associated with a greater shift in frequency. The effect of the inverse frequency shift may provide new insights into why the flute, with its euphonious tone, has been popular for thousands of years in Asia and Europe.

  6. Doppler Ultrasound Doppler and their applications in maternal medicine

    In this paper the technical aspects and physical principles of Doppler ultrasound are discussed, as well as the analysis that can be made from the quantitative and qualitative data. Finally, its utility in perinatal medicine is reviewed with emphasis in the clinical implications

  7. Comparisons between PW Doppler system and enhanced FM Doppler system

    Wilhjelm, Jens E.; Pedersen, P. C.

    system exploits the direct relationship between arrival time of the received signal and range from the transducer. In the FM Doppler systems, a similar relationship exists in the spectral domain of the demodulated received signals, so that range is represented by frequency. Thus, a shift in location of...

  8. Acoustic lenses

    Acoustic lenses focus ultrasound to produce pencil-like beams with reduced near fields. When fitted to conventional (flat-faced) transducers, such lenses greatly improve the ability to detect and size defects. This paper describes a program developed to design acoustic lenses for use in immersion or contact inspection, using normal or angle beam mode with flat or curved targets. Lens surfaces are circular in geometry to facilitate machining. For normal beam inspection of flat plate, spherical or cylindrical lenses are used. For angle beam or curved surface inspections, a compound lens is required to correct for the extra induced aberration. Such a lens is aspherical with one radius of curvature in the plane of incidence, and a different radius of curvature in the plane perpendicular to the incident plane. The resultant beam profile (i.e., location of the acoustic focus, beam diameter, 6 dB working range) depends on the degree of focusing and the transducer used. The operating frequency and bandwidth can be affected by the instrumentation used. Theoretical and measured beam profiles are in good agreement. Various applications, from zone focusing used for defect sizing in thick plate, to line focusing for pipe weld inspection, are discussed

  9. Field Measurements at River and Tidal Current Sites for Hydrokinetic Energy Development: Best Practices Manual

    Neary, Vincent S [ORNL; Gunawan, Budi [Oak Ridge National Laboratory (ORNL)

    2011-09-01

    In this report, existing data collection techniques and protocols for characterizing open channel flows are reviewed and refined to further address the needs of the MHK industry. The report provides an overview of the hydrodynamics of river and tidal channels, and the working principles of modern acoustic instrumentation, including best practices in remote sensing methods that can be applied to hydrokinetic energy site characterization. Emphasis is placed upon acoustic Doppler velocimeter (ADV) and acoustic-Doppler current profiler (ADCP) instruments, as these represent the most practical and economical tools for use in the MHK industry. Incorporating the best practices as found in the literature, including the parameters to be measured, the instruments to be deployed, the instrument deployment strategy, and data post-processing techniques. The data collected from this procedure aims to inform the hydro-mechanical design of MHK systems with respect to energy generation and structural loading, as well as provide reference hydrodynamics for environmental impact studies. The standard metrics and protocols defined herein can be utilized to guide field experiments with MHK systems.

  10. Doppler tomography in fusion plasmas and astrophysics

    Salewski, Mirko; Heidbrink, Bill; Jacobsen, Asger Schou; Korsholm, Soren Bang; Leipold, Frank; Madsen, Jens; Moseev, Dmitry; Nielsen, Stefan Kragh; Rasmussen, Jesper; Stagner, Luke; Steeghs, Danny; Stejner, Morten; Tardini, Giovani; Weiland, Markus

    2015-01-01

    Doppler tomography is a well-known method in astrophysics to image the accretion flow, often in the shape of thin discs, in compact binary stars. As accretion discs rotate, all emitted line radiation is Doppler-shifted. In fast-ion D-alpha (FIDA) spectroscopy measurements in magnetically confined plasma, the D-alpha-photons are likewise Doppler-shifted ultimately due to gyration of the fast ions. In either case, spectra of Doppler-shifted line emission are sensitive to the velocity distribution of the emitters. Astrophysical Doppler tomography has lead to images of accretion discs of binaries revealing bright spots, spiral structures, and flow patterns. Fusion plasma Doppler tomography has lead to an image of the fast-ion velocity distribution function in the tokamak ASDEX Upgrade. This image matched numerical simulations very well. Here we discuss achievements of the Doppler tomography approach, its promise and limits, analogies and differences in astrophysical and fusion plasma Doppler tomography, and what ...