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Sample records for acoustic backscatter abs

  1. Fundamentals of Acoustic Backscatter Imagery

    DTIC Science & Technology

    2011-09-20

    pressure, I,, of 1 /iPa, corresponds to 0.67 x 10- 8 Wim2. Assuming spherical spreading, the one meter distance reference frame, and the definition of dB (Eq...then be approximated by an infinite series Fundamentals ofAcoustic Backscatter Imagery 11 W(r) = Wm (r) + X Fjsc (r) j=O where "tic(r) is the incident...f( x ,y, Z)Iz=h(xy) = 0 f( x , y, z)I z=h( x ,y)= f( x , y, Z) I z o + h di+ h 2 d2f +zz z= The function ftx,y,z) can represent, for example, the stress

  2. Bathymetry and acoustic backscatter: Estero Bay, California

    USGS Publications Warehouse

    Hartwell, Stephen R.; Finlayson, David P.; Dartnell, Peter; Johnson, Samuel Y.

    2013-01-01

    Between July 30 and August 9, 2012, scientists from the U.S. Geological Survey (USGS), Pacific Coastal and Marine Science Center (PCMSC), acquired bathymetry and acoustic-backscatter data from Estero Bay, San Luis Obispo, California, under PCMSC Field Activity ID S-05-12-SC. The survey was done using the R/V Parke Snavely outfitted with a multibeam sonar for swath mapping and highly accurate position and orientation equipment for georeferencing. This report provides these data in a number of different formats, as well as a summary of the mapping mission, maps of bathymetry and backscatter, and Federal Geographic Data Committee (FGDC) metadata.

  3. Modeling and Measuring Acoustic Backscatter from Fish Aggregations

    DTIC Science & Technology

    1999-09-30

    of the abundance, spatial distribution, schooling behaviour and acoustic backscatter of the Namibian pilchard. Cruise Report 99-4, Dr. Fridtjof ... Nansen . 103 pp. Rudstam, L, Horne, J., Fleischer, G. Report from the Great Lakes Acoustic Workshop III: Translation of acoustic data to fish abundance

  4. Estimating sub-surface dispersed oil concentration using acoustic backscatter response.

    PubMed

    Fuller, Christopher B; Bonner, James S; Islam, Mohammad S; Page, Cheryl; Ojo, Temitope; Kirkey, William

    2013-05-15

    The recent Deepwater Horizon disaster resulted in a dispersed oil plume at an approximate depth of 1000 m. Several methods were used to characterize this plume with respect to concentration and spatial extent including surface supported sampling and autonomous underwater vehicles with in situ instrument payloads. Additionally, echo sounders were used to track the plume location, demonstrating the potential for remote detection using acoustic backscatter (ABS). This study evaluated use of an Acoustic Doppler Current Profiler (ADCP) to quantitatively detect oil-droplet suspensions from the ABS response in a controlled laboratory setting. Results from this study showed log-linear ABS responses to oil-droplet volume concentration. However, the inability to reproduce ABS response factors suggests the difficultly in developing meaningful calibration factors for quantitative field analysis. Evaluation of theoretical ABS intensity derived from the particle size distribution provided insight regarding method sensitivity in the presence of interfering ambient particles.

  5. Acoustic Coherent Backscatter Enhancement from Aggregations of Point Scatterers

    DTIC Science & Technology

    2014-09-30

    acoustic multiple scattering from two- and now three-dimensional aggregations of omni-directional point scatterers to determine the parametric realms in...given by the sum in (1), N is the number of scatterers , gn is the scattering coefficient of the nth scatterer , ψn(rn) is the field incident on the nth...SUBTITLE Acoustic Coherent Backscatter Enhancement from Aggregations of Point Scatterers 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT

  6. Floc Growth and Changes in ADV Acoustic Backscatter Signal

    NASA Astrophysics Data System (ADS)

    Rouhnia, M.; Keyvani, A.; Strom, K.

    2013-12-01

    A series of experiments were conducted to examine the effect of mud floc growth on the acoustic back-scatter signal recorded by a Nortek Vector acoustic Doppler velocimeter (ADV). Several studies have shown that calibration equations can be developed to link the backscatter strength with average suspended sediment concentration (SSC) when the sediment particle size distribution remains constant. However, when mud is present, the process of flocculation can alter the suspended particle size distribution. Past studies have shown that it is still unclear as to the degree of dependence of the calibration equation on changes in floc size. Part of the ambiguity lies in the fact that flocs can be porous and rather loosely packed and therefore might not scatter to the same extent as a grain of sand. In addition, direct, detailed measurements of floc size have not accompanied experiments examining the dependence of ADV backscatter and suspended sediment concentration. In this research, a set of laboratory experiments is used to test how floc growth affects the backscatter strength. The laboratory data is examined in light of an analytic model that was developed based on scatter theory to account for changes in both SSC and the floc properties of size and density. For the experiments, a turbulent suspension was created in a tank with a rotating paddle. Fixed concentrations of a mixture of kaolinite and montmorillonite were added to the tank in a step-wise manner. For each step, the flocs were allowed to grow to their equilibrium size before breaking the flocs with high turbulent mixing, adding more sediment, and then returning the mixing rate to a range suitable for the re-growth of flocs. During each floc growth phase, data was simultaneously collected at the same elevation in the tank using a floc camera to capture the changes in floc size, a Nortek Vector ADV for the acoustic backscatter, and a Campbell Scientific OBS 3+ for optical backscatter. Physical samples of the

  7. Acoustic Coherent Backscatter Enhancement from Aggregations of Point Scatterers

    DTIC Science & Technology

    2013-09-30

    Figure 2 for a cubical aggregation with a five- wavelength edge, 256 to 1024 Monte - Carlo trials, = 3.5, and four different average scatterer spacings...ensemble average over Monte - Carlo trials. The central peak at ϕ = 0 for k0s = 3.2 and 2.5 is produced by coherent backscattering enhancement...were placed in a cubical aggregation with 5 wavelength edges. The ensemble average was computed from 256 to 1024 Monte - Carlo trials. The acoustic

  8. Kinetic Enhancement of Raman Backscatter, and Electron Acoustic Thomson Scatter

    SciTech Connect

    Strozzi, D J; Williams, E A; Langdon, A B; Bers, A

    2006-09-01

    1-D Eulerian Vlasov-Maxwell simulations are presented which show kinetic enhancement of stimulated Raman backscatter (SRBS) due to electron trapping in regimes of heavy linear Landau damping. The conventional Raman Langmuir wave is transformed into a set of beam acoustic modes [L. Yin et al., Phys. Rev. E 73, 025401 (2006)]. For the first time, a low phase velocity electron acoustic wave (EAW) is seen developing from the self-consistent Raman physics. Backscatter of the pump laser off the EAW fluctuations is reported and referred to as electron acoustic Thomson scatter. This light is similar in wavelength to, although much lower in amplitude than, the reflected light between the pump and SRBS wavelengths observed in single hot spot experiments, and previously interpreted as stimulated electron acoustic scatter [D. S. Montgomery et al., Phys. Rev. Lett. 87, 155001 (2001)]. The EAW observed in our simulations is strongest well below the phase-matched frequency for electron acoustic scatter, and therefore the EAW is not produced by it. The beating of different beam acoustic modes is proposed as the EAW excitation mechanism, and is called beam acoustic decay. Supporting evidence for this process, including bispectral analysis, is presented. The linear electrostatic modes, found by projecting the numerical distribution function onto a Gauss-Hermite basis, include beam acoustic modes (some of which are unstable even without parametric coupling to light waves) and a strongly-damped EAW similar to the observed one. This linear EAW results from non-Maxwellian features in the electron distribution, rather than nonlinearity due to electron trapping.

  9. Bathymetry and Acoustic Backscatter: Northern Santa Barbara Channel, Southern California

    USGS Publications Warehouse

    Dartnell, Pete; Finlayson, David; Conrad, Jamie; Cochrane, Guy; Johnson, Samuel

    2010-01-01

    In the summer of 2008, as part of the California Seafloor Mapping Program (CSMP) the U.S. Geological Survey, Coastal and Marine Geology mapped a nearshore region of the northern Santa Barbara Channel in Southern California (fig 1). The CSMP is a cooperative partnership between Federal and State agencies, Universities, and Industry to create a comprehensive coastal/marine geologic and habitat basemap series to support the Marine Life Protection Act (MLPA) inititive. The program is supported by the California Ocean Protection Council and the California Coastal Conservancy. The 2008 mapping collected high resolution bathymetry and acoustic backscatter data using a bathymetric side scan system within State waters from about the 10-m isobath out over 3-nautical miles. This Open-File Report provides these data in a number of different formats, as well as a summary of the mapping mission, maps of bathymetry and backscatter, and FGDC metadata.

  10. A multiple case study for calibrating acoustic backscatter to total suspended material in a large river system

    NASA Astrophysics Data System (ADS)

    Gunkel, Brittany Lynne

    Sediment transport measurements are determined using techniques such as bed-material and suspended-sediment sampling, and more recently the conversion of acoustic backscatter (ABS). Acoustic waves scatter and attenuate while passing through a water-sediment mixture and the backscatter is converted to sediment concentration, size, and shape. A multiple case study performed using data from West Bay, Old River, and Mississippi River at Vicksburg show the variability of a large river system TSM flux during assorted hydrographs and two methods (CHL and moving boat) capture the events. After processing and applying the two methods the results showed that the methods are typically within 8% to 41% of each other when computing sediment flux. The conversion of total suspended material (TSM) from ABS was an average of 0.2% to 69% from the sample TSM. Peak part of the hydrograph had the highest average suspended sediment concentration (SSC) and descending had the lowest average SSC.

  11. Acoustic backscatter of the 1995 flood deposit on the Eel shelf

    USGS Publications Warehouse

    Borgeld, J.C.; Hughes-Clarke, John E.; Goff, John A.; Mayer, Larry A.; Curtis, Jennifer A.

    1999-01-01

    Acoustic swath mapping and sediment box coring conducted on the continental shelf near the mouth of the Eel River revealed regional variations in acoustic backscatter that can be related to the shelf sedimentology. The acoustic-backscatter variations observed on the shelf were unusually narrow compared to the response of similar sediment types documented in other areas. However, the acoustic data revealed four principal bottom types on the shelf that can be related to sedimentologic differences observed in cores. The four areas are: (1) low acoustic backscatter associated with the nearshore-sand facies and the prodelta terraces of the Eel and Mad rivers, composed of fine sands and coarse silts with low porosity; (2) high acoustic backscatter associated with fine silts characterized by high porosity and deposited by the 1995 flood of the Eel River; (3) intermediate acoustic backscatter in the outer-shelf muds, where clayey silts are accumulating and the 1995 flood apparently had limited direct effect; and (4) intermediate acoustic backscatter near the fringes of the 1995 flood deposits and in areas where the flood sediments were more disrupted by post-depositional processes. The highest acoustic backscatter was identified in areas where the 1995 flood sediments remained relatively intact and near the shelf surface into the summer of 1995. Cores collected from these areas contained wavy or lenticular bedding. The rapid deposition of the high-porosity muddy layers results in better preservation of incorporated ripple forms than in areas less directly impacted by the flood deposit. The high-porosity muddy layers allow acoustic penetration into the sediments and result in greater acoustic backscatter from incorporated roughness elements.

  12. Acoustic backscattering and radiation force on a rigid elliptical cylinder in plane progressive waves.

    PubMed

    Mitri, F G

    2016-03-01

    This work proposes a formal analytical theory using the partial-wave series expansion (PWSE) method in cylindrical coordinates, to calculate the acoustic backscattering form function as well as the radiation force-per-length on an infinitely long elliptical (non-circular) cylinder in plane progressive waves. The major (or minor) semi-axis of the ellipse coincides with the direction of the incident waves. The scattering coefficients for the rigid elliptical cylinder are determined by imposing the Neumann boundary condition for an immovable surface and solving a resulting system of linear equations by matrix inversion. The present method, which utilizes standard cylindrical (Bessel and Hankel) wave functions, presents an advantage over the solution for the scattering that is ordinarily expressed in a basis of elliptical Mathieu functions (which are generally non-orthogonal). Furthermore, an integral equation showing the direct connection of the radiation force function with the square of the scattering form function in the far-field from the scatterer (applicable for plane waves only), is noted and discussed. An important application of this integral equation is the adequate evaluation of the radiation force function from a bistatic measurement (i.e., in the polar plane) of the far-field scattering from any 2D object of arbitrary shape. Numerical predictions are evaluated for the acoustic backscattering form function and the radiation force function, which is the radiation force per unit length, per characteristic energy density, and per unit cross-sectional surface of the ellipse, with particular emphasis on the aspect ratio a/b, where a and b are the semi-axes, as well as the dimensionless size parameter kb, without the restriction to a particular range of frequencies. The results are particularly relevant in acoustic levitation, acousto-fluidics and particle dynamics applications.

  13. Hydrodynamic influences on acoustical and optical backscatter in a fringing reef environment

    NASA Astrophysics Data System (ADS)

    Pawlak, Geno; Moline, Mark A.; Terrill, Eric J.; Colin, Patrick L.

    2017-01-01

    Observations of hydrodynamics along with optical and acoustical water characteristics in a tropical fringing reef environment reveal a distinct signature associated with flow characteristics and tidal conditions. Flow conditions are dominated by tidal forcing with an offshore component from the reef flat during ebb. Measurements span variable wave conditions enabling identification of wave effects on optical and acoustical water properties. High-frequency acoustic backscatter (6 MHz) is strongly correlated with tidal forcing increasing with offshore directed flow and modulated by wave height, indicating dominant hydrodynamic influence. Backscatter at 300 and 1200 kHz is predominantly diurnal suggesting a biological component. Optical backscatter is closely correlated with high-frequency acoustic backscatter across the range of study conditions. Acoustic backscatter frequency dependence is used along with changes in optical properties to interpret particle-size variations. Changes across wave heights suggest shifts in particle-size distributions with increases in relative concentrations of smaller particles for larger wave conditions. Establishing a connection between the physical processes of a fringing tropical reef and the resulting acoustical and optical signals allows for interpretation and forecasting of the remote sensing response of these phenomena over larger scales.

  14. LISST-ABS: A Low-Cost Submersible Acoustic Sediment Sensor

    NASA Astrophysics Data System (ADS)

    Slade, W. H.; Agrawal, Y. C.; Dana, D. R.; Leeuw, T.; Pottsmith, C.

    2015-12-01

    The development of low-cost optical sensors (i.e., transmissometers and optical backscattering sensors, OBS) produced the last significant advance in in-situ monitoring of suspended sediment concentration. However, it was well-known from fundamental physics of light scattering and laboratory work, that their response suffered from a severe non-uniformity to grain-size (varying as 1/diameter), susceptibility to biofouling, and limited dynamic range. Here we present the development of a new, low cost, single-point, 8 MHz acoustic backscatter sensor, LISST-ABS that improves on all these shortcomings. For example, the response is nearly flat over 30-400 micron diameters varying within ±30% of the mean (compared with roughly ±400% for OBS over the same size range), fouling is less serious, and the dynamic range spans 5 decades without change of electronic gain. A key innovation of the LISST-ABS is the use of backscatter signal from two range cells in order to measure and compensate for sediment attenuation, allowing a working concentration range exceeding 1 mg/L to 70 g/L (for 7 micron particles).

  15. Acoustic backscatter by suspended cohesive sediments: Field observations, Seine Estuary, France

    NASA Astrophysics Data System (ADS)

    Sahin, Cihan; Verney, Romaric; Sheremet, Alexandru; Voulgaris, George

    2017-02-01

    Observations of suspended sediment size and concentration, flow and acoustic backscatter intensity collected on the Seine Estuary (France) are used to study the acoustic response in cohesive-sediment dominated environments. Estimates of suspended sediment concentration based on optical backscatter sensors and water samples are used to calibrate the acoustic backscatter intensity. The vertical structure of suspended sediment concentration is then estimated from acoustic backscatter information. To our knowledge, this is the first field application of the recently proposed model of acoustic scattering by flocculating suspensions based on the variation of particle density (floc-scattering model). The estimates of sediment concentration reproduce well the observations under different tidal (neap/spring) conditions, confirming the applicability of the new model in the field when detailed particle size measurements are available. When particle size measurements are not available, using estimated floc sizes based on the turbulence intensities may provide reasonable SSC profiles. During spring tide events (associated with strong currents, small flocs and large concentrations), the performances of the new floc-scattering model and the previous models given for solid particle-scattering are comparable. The floc-scattering model increases the quality of the SSC estimates especially during low-energy conditions characterized with larger flocs.

  16. Bathymetry and acoustic backscatter: Elwha River Delta, Washington

    USGS Publications Warehouse

    Finlayson, David P.; Miller, Ian M.; Warrick, Jonathan A.

    2011-01-01

    The surveys were conducted using the R/V Parke Snavely outfitted with an interferometric sidescan sonar for swath mapping and real-time kinematic navigation equipment for accurate shallow water operations. This report provides these data in a number of different formats, as well as a summary of the mapping mission, maps of bathymetry and backscatter, and Federal Geographic Data Committee (FGDC) metadata.

  17. Characterising nuclear simulant suspensions in situ with an acoustic backscatter system

    SciTech Connect

    Bux, Jaiyana; Hunter, Timothy N.; Paul, Neepa; Biggs, Simon R.; Dodds, Jonathan M.; Peakall, Jeffrey

    2013-07-01

    In situ characterisation of radio-toxic sludges and slurries is critical to numerous operations including those involving their transport and retrieval. An inexpensive, flexible acoustic backscatter system has been employed for the first time here to a 4/10. scale active storage tank comprising of a nuclear simulant suspension, to verify its application. Intricate suspension characteristics and tank operation features emerged. (authors)

  18. Anisotropy in high-frequency broadband acoustic backscattering in the presence of turbulent microstructure and zooplankton.

    PubMed

    Leong, Doris; Ross, Tetjana; Lavery, Andone

    2012-08-01

    High-frequency broadband (120-600 kHz) acoustic backscattering measurements have been made in the vicinity of energetic internal waves. The transducers on the backscattering system could be adjusted so as to insonify the water-column either vertically or horizontally. The broadband capabilities of the system allowed spectral classification of the backscattering. The distribution of spectral shapes is significantly different for scattering measurements made with the transducers oriented horizontally versus vertically, indicating that scattering anisotropy is present. However, the scattering anisotropy could not be unequivocally explained by either turbulent microstructure or zooplankton, the two primary sources of scattering expected in internal waves. Daytime net samples indicate a predominance of short-aspect-ratio zooplankton. Using zooplankton acoustic scattering models, a preferential orientation of the observed zooplankton cannot explain the measured anisotropy. Yet model predictions of scattering from anisotropic turbulent microstructure, with inputs from coincident microstructure measurements, were not consistent with the observations. Possible explanations include bandwidth limitations that result in many spectra that cannot be unambiguously attributed to turbulence or zooplankton based on spectral shape. Extending the acoustic bandwidth to cover the range from 50 kHz to 2 MHz could help improve identification of the dominant sources of backscattering anisotropy.

  19. Acoustic Coherent Backscatter Enhancement from Aggregations of Point Scatterers

    DTIC Science & Technology

    2015-09-30

    an aggregation of omnidirectional point scatterers [1]. If ψ(r) is the harmonic acoustic pressure field at frequency ω at the point r and ψ0(r) is...the harmonic field incident on the aggregation of scatterers located at rn, then , (1) where ψ(r) is the

  20. Bathymetry and acoustic backscatter-outer mainland shelf, eastern Santa Barbara Channel, California

    USGS Publications Warehouse

    Dartnell, Peter; Finlayson, David P.; Ritchie, Andrew C.; Cochrane, Guy R.; Erdey, Mercedes D.

    2012-01-01

    In 2010 and 2011, scientists from the U.S. Geological Survey (USGS), Pacific Coastal and Marine Science Center (PCMSC), acquired bathymetry and acoustic-backscatter data from the outer shelf region of the eastern Santa Barbara Channel, California. These surveys were conducted in cooperation with the Bureau of Ocean Energy Management (BOEM). BOEM is interested in maps of hard-bottom substrates, particularly natural outcrops that support reef communities in areas near oil and gas extraction activity. The surveys were conducted using the USGS R/V Parke Snavely, outfitted with an interferometric sidescan sonar for swath mapping and real-time kinematic navigation equipment. This report provides the bathymetry and backscatter data acquired during these surveys in several formats, a summary of the mapping mission, maps of bathymetry and backscatter, and Federal Geographic Data Committee (FGDC) metadata.

  1. Bathymetry and acoustic backscatter: outer mainland shelf and slope, Gulf of Santa Catalina, southern California

    USGS Publications Warehouse

    Dartnell, Peter; Conrad, James E.; Ryan, Holly F.; Finlayson, David P.

    2014-01-01

    In 2010 and 2011, scientists from the U.S. Geological Survey (USGS), Coastal and Marine Geology Program, acquired bathymetry and acoustic-backscatter data from the outer shelf and slope region offshore of southern California. The surveys were conducted as part of the USGS Marine Geohazards Program. Assessment of the hazards posed by offshore faults, submarine landslides, and tsunamis are facilitated by accurate and detailed bathymetric data. The surveys were conducted using the USGS R/V Parke Snavely outfitted with a 100-kHz Reson 7111 multibeam-echosounder system. This report provides the bathymetry and backscatter data acquired during these surveys in several formats, a summary of the mapping mission, maps of bathymetry and backscatter, and Federal Geographic Data Committee (FGDC) metadata.

  2. Field Demonstration of a Broadband Acoustical Backscattering System Mounted on a REMUS-100 for Inferences of Zooplankton Size and Abundance

    DTIC Science & Technology

    2012-09-30

    Backscattering System Mounted on a REMUS-100 for Inferences of Zooplankton Size and Abundance Andone C. Lavery Department of Applied Ocean Physics and...SUBTITLE Field Demonstration of a Broadband Acoustical Backscattering System Mounted on a REMUS-100 for Inferences of Zooplankton Size and Abundance 5a...of this REMUS- mounted broadband backscattering system with regards to inferring fish and zooplankton distribution, size and abundance in comparison

  3. Bathymetry, acoustic backscatter, and seafloor character of Farallon Escarpment and Rittenburg Bank, northern California

    USGS Publications Warehouse

    Dartnell, Peter; Cochrane, Guy R.; Finlayson, David P.

    2014-01-01

    In 2011, scientists from the U.S. Geological Survey’s Coastal and Marine Geology Program acquired bathymetry and acoustic-backscatter data along the upper slope of the Farallon Escarpment and Rittenburg Bank within the Gulf of the Farallones National Marine Sanctuary offshore of the San Francisco Bay area. The surveys were funded by the National Oceanic and Atmospheric Administration’s Deep Sea Coral Research and Technology Program to identify potential deep sea coral habitat prior to planned sampling efforts. Bathymetry and acoustic-backscatter data can be used to map seafloor geology (rock, sand, mud), and slope of the sea floor, both of which are useful for the prediction of deep sea coral habitat. The data also can be used for the prediction of sediment and contaminant budgets and transport, and for the assessment of earthquake and tsunami hazards. The surveys were conducted aboard National Oceanic and Atmospheric Administration’s National Marine Sanctuary Program’s 67-foot-long research vessel Fulmar outfitted with a U.S. Geological Survey 100-kHz Reson 7111 multibeam-echosounder system. This report provides the bathymetry and backscatter data acquired during these surveys, interpretive seafloor character maps in several formats, a summary of the mapping mission, maps of bathymetry and backscatter, and Federal Geographic Data Committee metadata.

  4. The effect of artificial rain on backscattered acoustic signal: first measurements

    NASA Astrophysics Data System (ADS)

    Titchenko, Yuriy; Karaev, Vladimir; Meshkov, Evgeny; Goldblat, Vladimir

    The problem of rain influencing on a characteristics of backscattered ultrasonic and microwave signal by water surface is considered. The rain influence on backscattering process of electromagnetic waves was investigated in laboratory and field experiments, for example [1-3]. Raindrops have a significant impact on backscattering of microwave and influence on wave spectrum measurement accuracy by string wave gauge. This occurs due to presence of raindrops in atmosphere and modification of the water surface. For measurements of water surface characteristics during precipitation we propose to use an acoustic system. This allows us obtaining of the water surface parameters independently on precipitation in atmosphere. The measurements of significant wave height of water surface using underwater acoustical systems are well known [4, 5]. Moreover, the variance of orbital velocity can be measure using these systems. However, these methods cannot be used for measurements of slope variance and the other second statistical moments of water surface that required for analyzing the radar backscatter signal. An original design Doppler underwater acoustic wave gauge allows directly measuring the surface roughness characteristics that affect on electromagnetic waves backscattering of the same wavelength [6]. Acoustic wave gauge is Doppler ultrasonic sonar which is fixed near the bottom on the floating disk. Measurements are carried out at vertically orientation of sonar antennas towards water surface. The first experiments were conducted with the first model of an acoustic wave gauge. The acoustic wave gauge (8 mm wavelength) is equipped with a transceiving antenna with a wide symmetrical antenna pattern. The gauge allows us to measure Doppler spectrum and cross section of backscattered signal. Variance of orbital velocity vertical component can be retrieved from Doppler spectrum with high accuracy. The result of laboratory and field experiments during artificial rain is presented

  5. Colored shaded-relief bathymetry, acoustic backscatter, and selected perspective views of the Inner Continental Borderland, southern California

    USGS Publications Warehouse

    Dartnell, Peter; Driscoll, Neal W.; Brothers, Daniel S.; Conrad, James E.; Kluesner, Jared; Kent, Graham; Andrews, Brian D.

    2015-01-01

    In late 2013, Scripps Institution of Oceanography collected multibeam bathymetry and acoustic-backscatter data of the Inner Continental Borderland Region, Southern California. The U.S. Geological Survey Pacific Coastal and Marine Science Center processed these data, and this report provides the data in a number of different formats in addition to a set of map sheets. The data catalog provides the new bathymetry and acoustic-backscatter data, collected mainly in the Gulf of Santa Catalina and San Diego Trough, as well as this new bathymetry data merged with other publically available bathymetry data from the region. Sheet 1 displays a colored shaded-relief bathymetry map of the Inner Continental Borderland generated from the merged bathymetry data. Sheet 2 displays the new acoustic-backscatter data along with other available backscatter data in the region. Sheet 3 displays selected perspective views of the bathymetry data highlighting submarine canyon and channel systems, knolls, and tectonic features.

  6. Seasonal dynamics of zooplankton in the southern Chukchi Sea revealed from acoustic backscattering strength

    NASA Astrophysics Data System (ADS)

    Kitamura, Minoru; Amakasu, Kazuo; Kikuchi, Takashi; Nishino, Shigeto

    2017-02-01

    To understand the seasonal dynamics of zooplankton in the southern Chukchi Sea, we use observations from a moored multi-frequency echo-sounder from July 2012 to July 2014. Zooplankton biomass, as indicated by area backscattering strength, was high during autumn and low in early spring; the seasonal peak in zooplankton biomass did not coincide with the spring phytoplankton bloom. This suggests that the seasonal zooplankton dynamics in the southern Chukchi Sea are less influenced by local growth of zooplankton during the spring phytoplankton bloom and more influenced by advection of zooplankton from the Bering Sea. The differences between volume backscattering strengths at 200 and 125 kHz suggest that the main acoustic scatterers are large zooplankton (euphausiids and Neocalanus cristatus) in late summer and autumn and small zooplankton (other copepods) in other seasons. The decrease in acoustic backscatter from large zooplankton from winter to early summer also suggests the unsuccessful overwintering of advected Pacific zooplankton. The temporal mismatch between zooplankton and phytoplankton production suggests that there is still tight pelagic-benthic coupling in the southern Chukchi Sea.

  7. Eigenfunction analysis of stochastic backscatter for characterization of acoustic aberration in medical ultrasound imaging

    NASA Astrophysics Data System (ADS)

    Varslot, Trond; Krogstad, Harald; Mo, Eirik; Angelsen, Bjørn A.

    2004-06-01

    Presented here is a characterization of aberration in medical ultrasound imaging. The characterization is optimal in the sense of maximizing the expected energy in a modified beamformer output of the received acoustic backscatter. Aberration correction based on this characterization takes the form of an aberration correction filter. The situation considered is frequently found in applications when imaging organs through a body wall: aberration is introduced in a layer close to the transducer, and acoustic backscatter from a scattering region behind the body wall is measured at the transducer surface. The scattering region consists of scatterers randomly distributed with very short correlation length compared to the acoustic wavelength of the transmit pulse. The scatterer distribution is therefore assumed to be δ correlated. This paper shows how maximizing the expected energy in a modified beamformer output signal naturally leads to eigenfunctions of a Fredholm integral operator, where the associated kernel function is a spatial correlation function of the received stochastic signal. Aberration characterization and aberration correction are presented for simulated data constructed to mimic aberration introduced by the abdominal wall. The results compare well with what is obtainable using data from a simulated point source.

  8. Calibration techniques and sampling resolution requirements for groundtruthing multibeam acoustic backscatter (EM3000) and QTC VIEW™ classification technology

    NASA Astrophysics Data System (ADS)

    Sutherland, T. F.; Galloway, J.; Loschiavo, R.; Levings, C. D.; Hare, R.

    2007-12-01

    Both acoustic and sediment surveys were carried out in the Broughton Archipelago, British Columbia, in order to map a former aquaculture site and calibrate acoustic surveys with georeferenced sediment properties. The acoustic surveys included EM3000 Multibeam (including backscatter) and QTC VIEW™ (Series IV) technologies, while the geotechnical survey entailed Van Veen grab sampling of surface sediments and associated analyses. The two acoustic technologies were consistent in their ability to identify distinct regions of seafloor characterized by rock outcrops, consolidated substrates, or gel-mud depositional fields. Both multibeam backscatter data and QTC VIEW™ number-coded classifications were extracted across a range of circular areas located at each georeferenced sampling station (radii: 2, 3, 4, 5, 8, 12, 16, 20 m). Statistical correlations were observed between backscatter and certain geotechnical properties, such as sediment porosity, sediment grain size fractions (<2 μm, silt content), and particulate sulfur concentration. The areal resolution of backscatter extraction was explored in terms of determining a sensitive calibration technique between backscatter and sediment properties. In general the highest r2 values between backscatter and sediment variables were observed across extraction radii between 8 and 20 m. Such groundtruthing techniques could be used to interpolate seafloor characteristics between sampling stations and provide a steering tool for sampling designs associated with benthic monitoring programs.

  9. Acoustic excitation of the circular Bragg{endash}Fresnel lens in backscattering geometry

    SciTech Connect

    Souvorov, A.; Snigireva, I.; Snigirev, A.; Aristova, E.; Hartman, Y.

    1997-02-01

    An increment of the x-ray flux in crystal Bragg{endash}Fresnel lens (BFL) focus in backscattering geometry obtained by means of acoustic excitation of the BFL crystal substrate has been investigated. The dependence of the x ray{close_quote}s total reflected power versus ultrasound parameters has been studied in a low frequency range (10{endash}50 MHz). The proposed technique allows an increase in the flux in a BFL focus by a factor of 2 which almost achieves the kinematic limit. {copyright} {ital 1997 American Institute of Physics.}

  10. Experimental investigation of geodesic acoustic modes on JET using Doppler backscattering

    NASA Astrophysics Data System (ADS)

    Silva, C.; Hillesheim, J. C.; Hidalgo, C.; Belonohy, E.; Delabie, E.; Gil, L.; Maggi, C. F.; Meneses, L.; Solano, E.; Tsalas, M.; Contributors, JET

    2016-10-01

    Geodesic acoustic modes (GAMs) have been investigated in JET ohmic discharges using mainly Doppler backscattering. Characteristics and scaling properties of the GAM are studied. Time and spatial resolved measurements of the perpendicular velocity indicate that GAMs are located in a narrow layer at the edge density gradient region with amplitude corresponding to about 50% of the mean local perpendicular velocity. GAMs on JET appear to be regulated by the turbulence drive rather than by their damping rate. It is also shown that the GAM amplitude is ~20% larger in deuterium than in hydrogen plasmas.

  11. Diel vertical migration of zooplankton at the S1 biogeochemical mooring revealed from acoustic backscattering strength

    NASA Astrophysics Data System (ADS)

    Inoue, Ryuichiro; Kitamura, Minoru; Fujiki, Tetsuichi

    2016-02-01

    We examined the diel vertical migration of zooplankton by using the backscatter strength obtained from moored acoustic Doppler current profilers at mooring site S1 in the North Pacific subtropical gyre. There was seasonal variability in the vertical distribution and migration of the high-backscatter layers in that they became deeper than the euphotic zone (<100 m) in winter and were confined above this depth in other seasons. Seasonal changes in daylight hours also affected the timing of the diel migration. We found that lunar cycles affected vertical distributions of zooplankton near the surface by changing the light intensity. Physical events, such as mixed-layer deepening and restratification and the passage of a mesoscale eddy, also affected zooplankton behavior possibly by changing food environment in the euphotic zone. Since the comparison with net samples indicated that the backscatter likely represents the bulk biomass, the accuracy of biomass estimates based on net samples could be influenced by the high temporal variability of zooplankton distributions.

  12. Time-dependent seafloor acoustic backscatter (10-100 kHz).

    PubMed

    Sternlicht, Daniel D; de Moustier, Christian P

    2003-11-01

    A time-dependent model of the acoustic intensity backscattered by the seafloor is described and compared with data from a calibrated, vertically oriented, echo-sounder operating at 33 and 93 kHz. The model incorporates the characteristics of the echo-sounder and transmitted pulse, and the water column spreading and absorption losses. Scattering from the water-sediment interface is predicted using Helmholtz-Kirchhoff theory, parametrized by the mean grain size, the coherent reflection coefficient, and the strength and exponent of a power-law roughness spectrum. The composite roughness approach of Jackson et al. [J. Acoust. Soc. Am. 79, 1410-1422 (1986)], modified for the finite duration of the transmitted signal, is used to predict backscatter from subbottom inhomogeneities. It depends on the sediment's volume scattering and attenuation coefficients, as well as the interface characteristics governing sound transmission into the sediment. Estimation of model parameters (mean grain size, roughness spectrum strength and exponent, volume scattering coefficient) reveals ambiguous ranges for the two spectral components. Analyses of model outputs and of physical measurements reported in the literature yield practical constraints on roughness spectrum parameter settings appropriate for echo-envelope-based sediment classification procedures.

  13. Comparisons among ten models of acoustic backscattering used in aquatic ecosystem research.

    PubMed

    Jech, J Michael; Horne, John K; Chu, Dezhang; Demer, David A; Francis, David T I; Gorska, Natalia; Jones, Benjamin; Lavery, Andone C; Stanton, Timothy K; Macaulay, Gavin J; Reeder, D Benjamin; Sawada, Kouichi

    2015-12-01

    Analytical and numerical scattering models with accompanying digital representations are used increasingly to predict acoustic backscatter by fish and zooplankton in research and ecosystem monitoring applications. Ten such models were applied to targets with simple geometric shapes and parameterized (e.g., size and material properties) to represent biological organisms such as zooplankton and fish, and their predictions of acoustic backscatter were compared to those from exact or approximate analytical models, i.e., benchmarks. These comparisons were made for a sphere, spherical shell, prolate spheroid, and finite cylinder, each with homogeneous composition. For each shape, four target boundary conditions were considered: rigid-fixed, pressure-release, gas-filled, and weakly scattering. Target strength (dB re 1 m(2)) was calculated as a function of insonifying frequency (f = 12 to 400 kHz) and angle of incidence (θ = 0° to 90°). In general, the numerical models (i.e., boundary- and finite-element) matched the benchmarks over the full range of simulation parameters. While inherent errors associated with the approximate analytical models were illustrated, so were the advantages as they are computationally efficient and in certain cases, outperformed the numerical models under conditions where the numerical models did not converge.

  14. Fluvial suspended sediment characteristics by high-resolution, surrogate metrics of turbidity, laser-diffraction, acoustic backscatter, and acoustic attenuation

    NASA Astrophysics Data System (ADS)

    Landers, Mark Newton

    Sedimentation is a primary and growing environmental, engineering, and agricultural issue around the world. However, collection of the data needed to develop solutions to sedimentation issues has declined by about three-fourths since 1983. Suspended-sediment surrogates have the potential to obtain sediment data using methods that are more accurate, of higher spatial and temporal resolution, and with less manually intensive, costly, and hazardous methods. The improved quality of sediment data from high-resolution surrogates may inform improved understanding and solutions to sedimentation problems. The field experiments for this research include physical samples of suspended sediment collected concurrently with surrogate metrics from instruments including 1.2, 1.5, and 3.0 megahertz frequency acoustic doppler current profilers, a nephelometric turbidity sensor, and a laser-diffraction particle size analyzer. This comprehensive data set was collected over five storms in 2009 and 2010 at Yellow River near Atlanta, Georgia. Fluvial suspended sediment characteristics in this study can be determined by high-resolution surrogate parameters of turbidity, laser-diffraction and acoustics with model errors 33% to 49% lower than traditional methods using streamflow alone. Hysteresis in sediment-turbidity relations for single storm events was observed and quantitatively related to PSD changes of less than 10 microns in the fine silt to clay size range. Suspended sediment particle size detection (PSD) is significantly correlated with ratios of measured acoustic attenuation at different frequencies; however the data do not fit the theoretical relations. Using both relative acoustic backscatter (RB) and acoustic attenuation as explanatory variables results in a significantly improved model of suspended sediment compared with traditional sonar equations using only RB. High resolution PSD data from laser diffraction provide uniquely valuable information; however the size detection

  15. Acoustic characterization of echogenic liposomes: Frequency-dependent attenuation and backscatter

    PubMed Central

    Kopechek, Jonathan A.; Haworth, Kevin J.; Raymond, Jason L.; Douglas Mast, T.; Perrin, Stephen R.; Klegerman, Melvin E.; Huang, Shaoling; Porter, Tyrone M.; McPherson, David D.; Holland, Christy K.

    2011-01-01

    Ultrasound contrast agents (UCAs) are used clinically to aid detection and diagnosis of abnormal blood flow or perfusion. Characterization of UCAs can aid in the optimization of ultrasound parameters for enhanced image contrast. In this study echogenic liposomes (ELIPs) were characterized acoustically by measuring the frequency-dependent attenuation and backscatter coefficients at frequencies between 3 and 30 MHz using a broadband pulse-echo technique. The experimental methods were initially validated by comparing the attenuation and backscatter coefficients measured from 50-μm and 100-μm polystyrene microspheres with theoretical values. The size distribution of the ELIPs was measured and found to be polydisperse, ranging in size from 40 nm to 6 μm in diameter, with the highest number observed at 65 nm. The ELIP attenuation coefficients ranged from 3.7 ± 1.0 to 8.0 ± 3.3 dB/cm between 3 and 25 MHz. The backscatter coefficients were 0.011 ± 0.006 (cm str)−1 between 6 and 9 MHz and 0.023 ± 0.006 (cm str)−1 between 13 and 30 MHz. The measured scattering-to-attenuation ratio ranged from 8% to 22% between 6 and 25 MHz. Thus ELIPs can provide enhanced contrast over a broad range of frequencies and the scattering properties are suitable for various ultrasound imaging applications including diagnostic and intravascular ultrasound. PMID:22088022

  16. Geomorphology, acoustic backscatter, and processes in Santa Monica Bay from multibeam mapping.

    PubMed

    Gardner, James V; Dartnell, Peter; Mayer, Larry A; Hughes Clarke, John E

    2003-01-01

    Santa Monica Bay was mapped in 1996 using a high-resolution multibeam system, providing the first substantial update of the submarine geomorphology since the initial compilation by Shepard and Emery [(1941) Geol. Soc. Amer. Spec. Paper 31]. The multibeam mapping generated not only high-resolution bathymetry, but also coregistered, calibrated acoustic backscatter at 95 kHz. The geomorphology has been subdivided into six provinces; shelf, marginal plateau, submarine canyon, basin slope, apron, and basin. The dimensions, gradients, and backscatter characteristics of each province is described and related to a combination of tectonics, climate, sea level, and sediment supply. Fluctuations of eustatic sea level have had a profound effect on the area; by periodically eroding the surface of Santa Monica plateau, extending the mouth of the Los Angeles River to various locations along the shelf break, and by connecting submarine canyons to rivers. A wetter glacial climate undoubtedly generated more sediment to the rivers that then transported the increased sediment load to the low-stand coastline and canyon heads. The trends of Santa Monica Canyon and several bathymetric highs suggest a complex tectonic stress field that has controlled the various segments. There is no geomorphic evidence to suggest Redondo Canyon is fault controlled. The San Pedro fault can be extended more than 30 km to the northwest by the alignment of a series of bathymetric highs and abrupt changes in direction of channel thalwegs.

  17. Estimating suspended solids concentrations from backscatter intensity measured by acoustic Doppler current profiler in San Francisco Bay, California

    USGS Publications Warehouse

    Gartner, J.W.

    2004-01-01

    The estimation of mass concentration of suspended solids is one of the properties needed to understand the characteristics of sediment transport in bays and estuaries. However, useful measurements or estimates of this property are often problematic when employing the usual methods of determination from collected water samples or optical sensors. Analysis of water samples tends to undersample the highly variable character of suspended solids, and optical sensors often become useless from biological fouling in highly productive regions. Acoustic sensors, such as acoustic Doppler current profilers that are now routinely used to measure water velocity, have been shown to hold promise as a means of quantitatively estimating suspended solids from acoustic backscatter intensity, a parameter used in velocity measurement. To further evaluate application of this technique using commercially available instruments, profiles of suspended solids concentrations are estimated from acoustic backscatter intensity recorded by 1200- and 2400-kHz broadband acoustic Doppler current profilers located at two sites in San Francisco Bay, California. ADCP backscatter intensity is calibrated using optical backscatterance data from an instrument located at a depth close to the ADCP transducers. In addition to losses from spherical spreading and water absorption, calculations of acoustic transmission losses account for attenuation from suspended sediment and correction for nonspherical spreading in the near field of the acoustic transducer. Acoustic estimates of suspended solids consisting of cohesive and noncohesive sediments are found to agree within about 8-10% (of the total range of concentration) to those values estimated by a second optical backscatterance sensor located at a depth further from the ADCP transducers. The success of this approach using commercially available Doppler profilers provides promise that this technique might be appropriate and useful under certain conditions in

  18. Broadband acoustic backscatter and high-resolution morphology of fish: Measurement and modeling

    NASA Astrophysics Data System (ADS)

    Reeder, D. Benjamin; Jech, J. Michael; Stanton, Timothy K.

    2004-08-01

    Broadband acoustic backscattering measurements, advanced high-resolution imaging of fish morphology using CT scans and phase-contrast x rays (in addition to traditional x rays), and associated scattering modeling using the images have been conducted involving alewife (Alosa pseudoharengus), a swimbladder-bearing fish. A greater-than-octave bandwidth (40-95 kHz) signal was used to insonify live, individual, adult alewife that were tethered while being rotated in 1-deg increments over all angles in two planes of rotation (lateral and dorsal/ventral). These data, in addition to providing the orientation dependence of the scattering over a continuous band of frequencies, were also used (after pulse compression) to identify dominant scattering features of the fish (including the skull and swimbladder). The x-ray and CT scan images of the swimbladder were digitized and incorporated into two scattering models: (1) Kirchhoff-ray mode (KRM) model [Clay and Horne, J. Acoust. Soc. Am. 96, 1661-1668 (1994)] and (2) conformal-mapping-based Fourier matching method (FMM), which has recently been extended to finite-length bodies [Reeder and Stanton, J. Acoust. Soc. Am. 116. 729-746 (2004)]. Comparisons between the scattering predictions and data demonstrate the utility of the CT scan imagery for use in scattering models, as it provided a means for rapidly and noninvasively measuring the fish morphology in three dimensions and at high resolution. In addition to further validation of the KRM model, the potential of the new FMM formulation was demonstrated, which is a versatile approach, valid over a wide range of shapes, all frequencies and all angles of orientation.

  19. Investigations into Ebb Tidal Fronts Using in Situ Acoustic Backscatter and Optical Satellite Imagery

    NASA Astrophysics Data System (ADS)

    Sun, D.; Ortiz-Suslow, D. G.; Haus, B. K.; Laxague, N.; Graber, H. C.; Hargrove, J.; Williams, N. J.

    2014-12-01

    The Office of Naval Research sponsored the Riverine and Estuarine Transport (RIVET) experiment during May 2012 at New River Inlet, North Carolina, in an effort to better understand the complex wave-current-wind interactions typical of tidal inlets. Over the course of a month, this highly sheared zone was intensely sampled with an array of Eulerian and Lagrangian instruments, in part, as a means of creating a synoptic, three-dimensional data set for validating various satellite remote sensing platforms. A component of this project was to deploy the Surface Physics Experimental Catamaran (SPEC), which is a mobile vessel designed specifically for collecting detailed meteorological and oceanographic data in coastal waters. Among its suite of instruments, SPEC was outfitted with a pair of acoustic doppler velocimeters (ADV), an acoustic doppler current profiler (ADCP), and an optical backscatter sensor (OBS). This instrument package allowed for high resolution mapping of the acoustic signature of the ebb tidal plume and the sub-surface, two-dimensional flow field. On May 8th, at 18:40 UTC, a panchromatic satellite image with a 0.6 m resolution, covering 122 km2, was taken of the New River Inlet Estuary and the inner shelf waters just off-shore. Numerous interesting features are visible in the image, such as the river outflow plume, surface streaks and slicks, a complex wave-field, and a remnant frontal edge from the past ebb tide. Interpretation of the surface features in these types of optical images remains a significant challenge and we have used data collected by SPEC immediately after the image acquisition to help illuminate the processes underlying these signatures.

  20. Wintertime water dynamics and moonlight disruption of the acoustic backscatter diurnal signal in an ice-covered Northeast Greenland fjord

    NASA Astrophysics Data System (ADS)

    Petrusevich, Vladislav; Dmitrenko, Igor; Kirillov, Sergey; Rysgaard, Søren; Falk-Petersen, Stig; Barber, David; Ehn, Jens

    2016-04-01

    Six and a half month time series of acoustic backscatter and velocity from three ice-tethered Acoustic Doppler Current Profilers deployed in the Young Sound fjord in Northeast Greenland were used to analyse the acoustic signal. During period of civil polar night below the land-fast ice, the acoustic data suggest a systematic diel vertical migration (DVM) of backscatters likely comprised of zooplankton. The acoustic backscatter and vertical velocity data were also arranged in a form of actograms. Results show that the acoustic signal pattern typical to DVM in Young Sound persists throughout the entire winter including the period of civil polar night. However, polynya-enhanced estuarine-like cell circulation that occurred during winter disrupted the DVM signal favouring zooplankton to occupy the near-surface water layer. This suggests that zooplankton avoided spending additional energy crossing the interface with a relatively strong velocity gradient comprised by fjord inflow in the intermediate layer and outflow in the subsurface layer. Instead the zooplankton tended to favour remaining in the upper 40 m layer where also the relatively warmer water temperatures associated with upward heat flux during enhanced estuarine-like circulation could be energetically favourable. Furthermore, our data show moonlight disruption of DVM in the subsurface layer and weaker intensity of vertical migration beneath snow covered land-fast ice during polar night. Using existing models for lunar illuminance and light transmission through sea ice and snow cover we estimated under ice illuminance and compared it with known light sensitivity for Arctic zooplankton species.

  1. Acoustic backscattering by deepwater fish measured in situ from a manned submersible

    NASA Astrophysics Data System (ADS)

    Benoit-Bird, Kelly J.; Au, Whitlow W. L.; Kelley, Christopher D.; Taylor, Christopher

    2003-02-01

    An outstanding problem in fisheries acoustics is the depth dependence of scattering characteristics of swimbladder-bearing fish, and the effects of pressure on the target strength of physoclistous fish remain unresolved. In situ echoes from deepwater snappers were obtained with a sonar transducer mounted on a manned submersible next to a low-light video camera, permitting simultaneous echo recording and identification of species, fish size and orientation. The sonar system, consisting of a transducer, single board computer, hard disk, and analog-to-digital converter, used a 80 μs, broadband signal (bandwidth 35 kHz, center frequency 120 kHz). The observed relationship between fish length and in situ target strength shows no difference from the relationship measured at the surface. No differences in the species-specific temporal echo characteristics were observed between surface and in situ measures. This indicates that the size and shape of the snappers' swimbladders are maintained both at the surface and at depths of up to 250 m. Information obtained through controlled backscatter measurements of tethered, anesthetized fish at the surface can be applied to free-swimming fish at depth. This is the first published account of the use of a manned submersible to measure in situ scattering from identified, individual animals with known orientations. The distinct advantage of this technique compared with other in situ techniques is the ability to observe the target fish, obtaining accurate species, size, and orientation information.

  2. Erratum: ?Stimulated Brillouin Backscattering and Ion Acoustic Wave Secondary Instability? [Phys. Plasmas 16, 032701 (2009)

    SciTech Connect

    Cohen, B I; Williams, E A; Berger, R L; Pesme, D; Riconda, C

    2009-04-20

    This Erratum addresses errors that occurred in some of the analysis in our recent publication (Ref. 1). The main elements of Ref. 1 are (1) the presentation of kinetic simulations of simulated Brillouin backscattering (SBS) and the accompanying secondary instability of the primary SBS ion acoustic wave (IAW) with and without the inclusion of the second harmonic of the primary IAW; (2) analyses of the four-wave (primary IAW, low-frequency IAW, and two sidebands of the primary IAW) and seven-wave (includes the second harmonic of the primary IAW and its two sidebands, as well as the four waves defined in the foregoing) dispersion relations for the secondary IAW instability; (3) comparisons of the results of solving the dispersion relations to the two particle simulations; (4) mode coupling calculations for SBS and the four-wave system of IAWs that model the particle simulations; and (5) a discussion and summary. However, the simplified 7-wave dispersion relation used in Ref. 1 propagated a typographical error in Eq.(44) in Ref. 2, the Pesme, Riconda, and Tikhonchuk (PRT) paper. This Erratum corrects Eq.(44) of Ref. 2 (discussed in more detail in an Erratum3 for Ref. 2) and revises Sec. IV of Ref. 1 by correcting the analysis and comparisons of the 4-wave and 7-wave dispersion relations, and the comparison of the 7-wave dispersion relation to the particle simulations. We find that the results of the corrected 7-wave dispersion relation are not profoundly different from the corresponding results in Ref. 1 and the 7-wave growth rates of the most unstable modes are more similar to the results of the 4-wave dispersion relation. The main results of Ref. 1 are unchanged: (1) the particle simulations exhibit a secondary IAW instability that is a modulational instability involving parallel and obliquely propagating IAWs; (2) the two types of particle simulation exhibit similar spectra, and the second harmonic IAW is a transient feature in the first particle simulation that is

  3. Acoustic backscatter and effective scatterer size estimates using a 2D CMUT transducer

    NASA Astrophysics Data System (ADS)

    Liu, W.; Zagzebski, J. A.; Hall, T. J.; Madsen, E. L.; Varghese, T.; Kliewer, M. A.; Panda, S.; Lowery, C.; Barnes, S.

    2008-08-01

    Compared to conventional piezoelectric transducers, new capacitive microfabricated ultrasonic transducer (CMUT) technology is expected to offer a broader bandwidth, higher resolution and advanced 3D/4D imaging inherent in a 2D array. For ultrasound scatterer size imaging, a broader frequency range provides more information on frequency-dependent backscatter, and therefore, generally more accurate size estimates. Elevational compounding, which can significantly reduce the large statistical fluctuations associated with parametric imaging, becomes readily available with a 2D array. In this work, we show phantom and in vivo breast tumor scatterer size image results using a prototype 2D CMUT transducer (9 MHz center frequency) attached to a clinical scanner. A uniform phantom with two 1 cm diameter spherical inclusions of slightly smaller scatterer size was submerged in oil and scanned by both the 2D CMUT and a conventional piezoelectric linear array transducer. The attenuation and scatterer sizes of the sample were estimated using a reference phantom method. RF correlation analysis was performed using the data acquired by both transducers. The 2D CMUT results indicate that at a 2 cm depth (near the transmit focus for both transducers) the correlation coefficient reduced to less than 1/e for 0.2 mm lateral or 0.25 mm elevational separation between acoustic scanlines. For the conventional array this level of decorrelation requires a 0.3 mm lateral or 0.75 mm elevational translation. Angular and/or elevational compounding is used to reduce the variance of scatterer size estimates. The 2D array transducer acquired RF signals from 140 planes over a 2.8 cm elevational direction. If no elevational compounding is used, the fractional standard deviation of the size estimates is about 12% of the mean size estimate for both the spherical inclusion and the background. Elevational compounding of 11 adjacent planes reduces it to 7% for both media. Using an experimentally estimated

  4. Acoustic backscatter and effective scatterer size estimates using a 2D CMUT transducer

    PubMed Central

    Liu, W; Zagzebski, J A; Hall, T J; Madsen, E L; Varghese, T; Kliewer, M A; Panda, S; Lowery, C; Barnes, S

    2009-01-01

    Compared to conventional piezoelectric transducers, new capacitive microfabricated ultrasonic transducer (CMUT) technology is expected to offer a broader bandwidth, higher resolution and advanced 3D/4D imaging inherent in a 2D array. For ultrasound scatterer size imaging, a broader frequency range provides more information on frequency-dependent backscatter, and therefore, generally more accurate size estimates. Elevational compounding, which can significantly reduce the large statistical fluctuations associated with parametric imaging, becomes readily available with a 2D array. In this work, we show phantom and in vivo breast tumor scatterer size image results using a prototype 2D CMUT transducer (9 MHz center frequency) attached to a clinical scanner. A uniform phantom with two 1 cm diameter spherical inclusions of slightly smaller scatterer size was submerged in oil and scanned by both the 2D CMUT and a conventional piezoelectric linear array transducer. The attenuation and scatterer sizes of the sample were estimated using a reference phantom method. RF correlation analysis was performed using the data acquired by both transducers. The 2D CMUT results indicate that at a 2 cm depth (near the transmit focus for both transducers) the correlation coefficient reduced to less than 1/e for 0.2 mm lateral or 0.25 mm elevational separation between acoustic scanlines. For the conventional array this level of decorrelation requires a 0.3 mm lateral or 0.75 mm elevational translation. Angular and/or elevational compounding is used to reduce the variance of scatterer size estimates. The 2D array transducer acquired RF signals from 140 planes over a 2.8 cm elevational direction. If no elevational compounding is used, the fractional standard deviation of the size estimates is about 12% of the mean size estimate for both the spherical inclusion and the background. Elevational compounding of 11 adjacent planes reduces it to 7% for both media. Using an experimentally estimated

  5. Quantitative broadband ultrasonic backscatter - An approach to nondestructive evaluation in acoustically inhomogeneous materials

    NASA Technical Reports Server (NTRS)

    Odonnell, M.; Miller, J. G.

    1981-01-01

    The use of a broadband backscatter technique to obtain the frequency dependence of the longitudinal-wave ultrasonic backscatter coefficient from a collection of scatterers in a solid is investigated. Measurements of the backscatter coefficient were obtained over the range of ultrasonic wave vector magnitude-glass sphere radius product between 0.1 and 3.0 from model systems consisting of dilute suspensions of randomly distributed crown glass spheres in hardened polyester resin. The results of these measurements were in good agreement with theoretical prediction. Consequently, broadband measurements of the ultrasonic backscatter coefficient may represent a useful approach toward characterizing the physical properties of scatterers in intrinsically inhomogeneous materials such as composites, metals, and ceramics, and may represent an approach toward nondestructive evaluation of these materials.

  6. Wintertime water dynamics and moonlight disruption of the acoustic backscatter diurnal signal in an ice-covered Northeast Greenland fjord

    NASA Astrophysics Data System (ADS)

    Petrusevich, Vladislav; Dmitrenko, Igor A.; Kirillov, Sergey A.; Rysgaard, Søren; Falk-Petersen, Stig; Barber, David G.; Boone, Wieter; Ehn, Jens K.

    2016-07-01

    Six and a half month records from three ice-tethered Acoustic Doppler Current Profilers deployed in October 2013 in Young Sound fjord in Northeast Greenland are used to analyze the acoustic backscatter signal. The acoustic data suggest a systematic diel vertical migration (DVM) of scatters below the land-fast ice during polar night. The scatters were likely composed of zooplankton. The acoustic signal pattern typical to DVM persisted in Young Sound throughout the entire winter including the period of civil polar night. However, polynya-enhanced estuarine-like cell circulation that occurred during winter disrupted the DVM signal favoring zooplankton to occupy the near-surface water layer. This suggests that zooplankton avoided spending additional energy crossing the interface with a relatively strong velocity gradient comprised by fjord inflow in the intermediate layer and outflow in the subsurface layer. Instead, the zooplankton tended to remain in the upper 40 m layer where relatively warmer water temperatures associated with upward heat flux during enhanced estuarine-like circulation could be energetically favorable. Furthermore, our data show moonlight disruption of DVM in the subsurface layer and weaker intensity of vertical migration beneath snow covered land-fast ice during polar night. Finally, by using existing models for lunar illuminance and light transmission through sea ice and snow cover, we estimated under ice illuminance and compared it with known light sensitivity of Arctic zooplankton species.

  7. Buoyancy characteristics of the bloater (Coregonus hoyi) in relation to patterns of vertical migration and acoustic backscattering

    USGS Publications Warehouse

    Fleischer, Guy W.; TeWinkel, Leslie M.

    1998-01-01

    Acoustic studies in Lake Michigan found that bloaters (Coregonus hoyi) were less reflective per size than the other major pelagic species. This difference in in situ acoustic backscattering could indicate that the deep-water bloaters have compressed swimbladders for much of their vertical range with related implications on buoyancy. To test this hypothesis, the buoyancy characteristics of bloaters were determined with fish placed in a cage that was lowered to bottom and monitored with an underwater camera. We found bloaters were positively buoyant near surface, neutrally buoyant at intermediate strata, and negatively buoyant near bottom. This pattern was consistent for the range of depths bloaters occur. The depth of neutral buoyancy (near the 50-n strata) corresponds with the maximum extent of vertical migration for bloaters observed in acoustic surveys. Fish below this depth would be negatively buoyant which supports our contention that bloaters deeper in the water column have compressed swimbladders. Understanding the buoyancy characteristics of pelagic fishes will help to predict the effects of vertical migration on target strength measurement and confirms the use of acoustics as a tool to identify and quantify the ecological phenomenon of vertical migration.

  8. Random matrix theory applied to acoustic backscattering and imaging in complex media.

    PubMed

    Aubry, Alexandre; Derode, Arnaud

    2009-02-27

    The singular values distribution of the propagation operator in a random medium is investigated in a backscattering configuration. Experiments are carried out with pulsed ultrasonic waves around 3 MHz, using an array of transducers. Coherent backscattering and field correlations are taken into account. Interestingly, the distribution of singular values shows a dramatically different behavior in the single and multiple-scattering regimes. Based on a matrix separation of single and multiple-scattered waves, an experimental illustration of imaging through a highly scattering slab is presented.

  9. Use of acoustic backscatter to estimate continuous suspended sediment and phosphorus concentrations in the Barton River, northern Vermont, 2010-2013

    USGS Publications Warehouse

    Medalie, Laura; Chalmers, Ann T.; Kiah, Richard G.; Copans, Benjamin

    2014-01-01

    The U.S. Geological Survey, in cooperation with the Vermont Department of Environmental Conservation, investigated the use of acoustic backscatter to estimate concentrations of suspended sediment and total phosphorus at the Barton River near Coventry, Vermont. The hypothesis was that acoustic backscatter—the reflection of sound waves off objects back to the source from which they came—measured by an acoustic Doppler profiler (ADP) and recorded as ancillary data for the calculation of discharge, also could be used to generate a continuous concentration record of suspended sediment and phosphorus at the streamgage, thereby deriving added value from the instrument. Suspended-sediment and phosphorus concentrations are of particular interest in Vermont, where impairment of surface waters by suspended sediments and phosphorus is a major concern. Regression models for estimating suspended-sediment concentrations (SSCs) and total phosphorus concentrations evaluated several independent variables: measured backscatter (MB), water-corrected backscatter (WCB), sediment-corrected backscatter (SCB), discharge, fluid-absorption coefficient, sediment-driven acoustic attenuation coefficient, and discharge hysteresis. The best regression equations for estimating SSC used backscatter as the predictor, reflecting the direct relation between acoustic backscatter and SSC. Backscatter was a better predictor of SSC than discharge in part because hysteresis between SSC and backscatter was less than for SSC and discharge. All three backscatter variables—MB, WCB, and SCB—performed equally as predictors of SSC and phosphorus concentrations at the Barton River site. The similar abilities to predict SSC among backscatter terms may partially be attributed to the low values and narrow range of the sediment-driven acoustic attenuation in the Barton River. The regression based on SCB was selected for estimating SSC because it removes potential bias caused by attenuation and temperature

  10. Quantifying quagga mussel veliger abundance and distribution in Copper Basin Reservoir (California) using acoustic backscatter.

    PubMed

    Anderson, Michael A; Taylor, William D

    2011-11-01

    Quagga mussels (Dreissena bugensis) have been linked to oligotrophication of lakes, alteration of aquatic food webs, and fouling of infrastructure associated with water supply and power generation, causing potentially billions of dollars in direct and indirect damages. Understanding their abundance and distribution is key in slowing their advance, assessing their potential impacts, and evaluating effectiveness of control strategies. Volume backscatter strength (Sv) measurements at 201- and 430-kHz were compared with quagga mussel veliger and zooplankton abundances determined from samples collected using a Wisconsin closing net from the Copper Basin Reservoir on the Colorado River Aqueduct. The plankton within the lower portion of the water column (>18 m depth) was strongly dominated by D-shaped quagga mussel veligers, comprising up to 95-99% of the community, and allowed direct empirical measurement of their mean backscattering cross-section. The upper 0-18 m of the water column contained a smaller relative proportion of veligers based upon net sampling. The difference in mean volume backscatter strength at these two frequencies was found to decrease with decreasing zooplankton abundance (r(2) = 0.94), allowing for correction of Sv due to the contribution of zooplankton and the determination of veliger abundance in the reservoir. Hydroacoustic measurements revealed veligers were often present at high abundances (up to 100-200 ind L(-1)) in a thin 1-2 m layer at the thermocline, with considerable patchiness in their distribution observed along a 700 m transect on the reservoir. Under suitable conditions, hydroacoustic measurements can rapidly provide detailed information on the abundance and distribution of quagga mussel veligers over large areas with high horizontal and vertical resolution.

  11. Analysis of Backscatter and Seafloor Acoustical Properties across deepwater sandwaves in Cook Strait, New Zealand

    NASA Astrophysics Data System (ADS)

    Lurton, X.; Lamarche, G.

    2011-12-01

    Central Cook Strait, New Zealand presents a variety of geological landforms subjected to intense hydrodynamic conditions. A comprehensive EM300 multibeam coverage of the strait was used to develop a method to objectively characterise the seafloor substrate. Specific post-processing was applied to the backscatter data to correct the signal from sensor bias, and was completed by correlating a quantitative description of backscatter with the field data. The final calibrated Backscattering Strength (BS) provides information on the physical characteristics of the seafloor. The BS imagery was used for both qualitative and quantitative interpretation, and give access to a level of detail higher than with conventional multibeam bathymetry. We developed a functional descriptive model of the physical BS angular response, describing satisfactorily the various typical BS responses met over Cook Strait and providing a first-order interpretation of the substrate composition. The full model needs 6 input parameters, but a practical classification can be obtained with only two (the BS value at 45° and the specular-to-oblique contrast). We analyse the BS angular response of sandwaves and erosional bedforms typically met in the central Cook Strait. The sandwave fields occur in 200-350 m of water depth and exhibit large-scale topographical features (wavelengths 100 - 250 m; vertical amplitudes 2 - 10 m). They are conspicuous in the backscatter imagery, and analysing their BS variations according to topography is specially informative. The BS level has a sharp minimum at the wave crests and is maximal inside the troughs, with a typical dynamics of 6 dB. Such a variation cannot be explained by the dependence on incident angle retrieved from local high-resolution bathymetry. Hence we infer that the reflectivity variations observed on the sandwaves are due to sediment facies changes, from fine to coarse sand in this case. This is corroborated by the fact that some sandwave fields with

  12. Acoustic measurement of suspensions of clay and silt particles using single frequency attenuation and backscatter

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The use of ultrasonic acoustic technology to measure the concentration of fine suspended sediments has the potential to greatly increase the temporal and spatial resolution of sediment measurements while reducing the need for personnel to be present at gauging stations during storm events. The conv...

  13. Bathymetry and acoustic backscatter data collected in 2010 from Cat Island, Mississippi

    USGS Publications Warehouse

    Buster, Noreen A.; Pfeiffer, William R.; Miselis, Jennifer L.; Kindinger, Jack G.; Wiese, Dana S.; Reynolds, B.J.

    2012-01-01

    Scientists from the U.S. Geological Survey (USGS), St. Petersburg Coastal and Marine Science Center (SPCMSC), in collaboration with the U.S. Army Corps of Engineers (USACE), conducted geophysical and sedimentological surveys around Cat Island, the westernmost island in the Mississippi-Alabama barrier island chain (fig. 1). The objectives of the study were to understand the geologic evolution of Cat Island relative to other barrier islands in the northern Gulf of Mexico and to identify relationships between the geologic history, present day morphology, and sediment distribution. This report contains data from the bathymetry and side-scan sonar portion of the study collected during two geophysical cruises. Interferometric swath bathymetry and side-scan sonar data were collected aboard the RV G.K. Gilbert September 7-15, 2010. Single-beam bathymetry was collected in shallow water around the island (< 2 meter (m)) from the RV Streeterville from September 28 to October 2, 2010, to cover the data gap between the landward limit of the previous cruise and the shoreline. This report serves as an archive of processed interferometric swath and single-beam bathymetry and side scan sonar data. GIS data products include a 50-m cell size interpolated gridded bathymetry surface, trackline maps, and an acoustic side-scan sonar image. Additional files include error analysis maps, Field Activity Collection System (FACS) logs, and formal Federal Geographic Data Committee (FDGC) metadata.

  14. Evaluation of Backscatter in the northeastern Red Sea using a Lowered Acoustic Doppler Profiler, Simrad EK60 Echosounder and in situ Observations

    NASA Astrophysics Data System (ADS)

    Torres, D. J.; Klevjer, T. A.; Solberg, I.; Bower, A. S.; Kaartvedt, S.

    2010-12-01

    An oceanographic research cruise aboard the R/V Aegaeo was conducted in the Red Sea from 16-29 March 2010. The primary objective of the cruise was to undertake the first large-scale physical oceanographic survey of the northeastern quadrant of the Red Sea, including observations of top-to-bottom ocean currents and water properties such as temperature, salinity, dissolved oxygen, turbidity and fluorescence. Additional objectives were to take seawater samples throughout the water column for carbonate chemistry and microbial studies, and to survey the distribution of pelagic fishes using acoustic methods. A total of 111 casts were made during the cruise which covered nine transects ranging from 22°-28°N. A modified SeaBird 9/11+ rosette/CTD system equipped with a pair of upward and downward facing 300 kHz Lowered Acoustic Doppler Current Profilers (LADCP) from Teledyne RD Instruments was used for station sampling. The LADCP system is primarily used for measuring full water column absolute velocity profiles. However, this study focuses on using the LADCP echo intensity data to measure ocean backscatter. Complex methods are usually required for calibration of acoustic instruments to measure backscatter due to attenuation and absorption of sound in water. Here we present a method for data processing which eliminates the need for calibration by using a single bin at a fixed distance from the ADCP transducers. We also present data from a Simrad EK60 echosounder which collected underway acoustic data throughout the cruise. Diurnal migration patterns of mesopelagic fish (an abundant and important part of the Red Sea ecosystem) are clearly evident in both data sets. Although the LADCP (due to bin size settings optimized for water velocity measurements) cannot resolve the thinner layers of acoustic scatterers compared to the 38 kHz EK60 data, it can be a very useful tool for measuring fish and zooplankton distribution from ships not equipped with high end acoustic

  15. A multivariate analytical method to characterize sediment attributes from high-frequency acoustic backscatter and ground-truthing data (Jade Bay, German North Sea coast)

    NASA Astrophysics Data System (ADS)

    Biondo, Manuela; Bartholomä, Alexander

    2017-04-01

    One of the burning issues on the topic of acoustic seabed classification is the lack of solid, repeatable, statistical procedures that can support the verification of acoustic variability in relation to seabed properties. Acoustic sediment classification schemes often lead to biased and subjective interpretation, as they ultimately aim at an oversimplified categorization of the seabed based on conventionally defined sediment types. However, grain size variability alone cannot be accounted for acoustic diversity, which will be ultimately affected by multiple physical processes, scale of heterogeneity, instrument settings, data quality, image processing and segmentation performances. Understanding and assessing the weight of all of these factors on backscatter is a difficult task, due to the spatially limited and fragmentary knowledge of the seabed from of direct observations (e.g. grab samples, cores, videos). In particular, large-scale mapping requires an enormous availability of ground-truthing data that is often obtained from heterogeneous and multidisciplinary sources, resulting into a further chance of misclassification. Independently from all of these limitations, acoustic segments still contain signals for seabed changes that, if appropriate procedures are established, can be translated into meaningful knowledge. In this study we design a simple, repeatable method, based on multivariate procedures, with the scope to classify a 100 km2, high-frequency (450 kHz) sidescan sonar mosaic acquired in the year 2012 in the shallow upper-mesotidal inlet of the Jade Bay (German North Sea coast). The tool used for the automated classification of the backscatter mosaic is the QTC SWATHVIEWTMsoftware. The ground-truthing database included grab sample data from multiple sources (2009-2011). The method was designed to extrapolate quantitative descriptors for acoustic backscatter and model their spatial changes in relation to grain size distribution and morphology. The

  16. Acoustic backscatter measurements with a 153 kHz ADCP in the northeastern Gulf of Mexico: determination of dominant zooplankton and micronekton scatterers

    NASA Astrophysics Data System (ADS)

    Ressler, Patrick H.

    2002-11-01

    A 153 kHz narrowband acoustic Doppler current profiler (ADCP) was used to measure volume backscattering strength ( Sv) during a deepwater oceanographic survey of cetacean and seabird habitat in the northeastern Gulf of Mexico. Sv was positively related to zooplankton and micronekton biomass (wet displacement volume) in 'sea-truth' net hauls made with a 1 m 2 Multiple Opening-Closing Net Environmental Sensing System (MOCNESS). A subset of these MOCNESS tows was used to explore the relationship between the numerical densities of various taxonomic categories of zooplankton and the ADCP backscatter signal. Crustaceans, small fish, and fragments of non-gas-bearing siphonophores in the net samples all showed significant, positive correlations with the acoustic signal, while other types of gelatinous zooplankton, pteropod and atlantid molluscs, and gas-filled siphonophore floats showed no significant correlation with Sv. Previously published acoustic scattering models for zooplankton were used to calculate expected scattering for several general zooplankton types and sizes for comparison with the field data. Even though gelatinous material often made up a large fraction of the total biomass, crustaceans, small fish, and pteropods were most likely the important scatterers. Since only crustacean and small fish densities were significantly correlated with Sv, it is suggested that Sv at 153 kHz can be used as a relative proxy for the abundance of these organisms in the Gulf of Mexico.

  17. Use of SDWBA predictions for acoustic volume backscattering and the Self-Organizing Map to discern frequencies identifying Meganyctiphanes norvegica from mesopelagic fish species

    NASA Astrophysics Data System (ADS)

    Peña, M.; Calise, L.

    2016-04-01

    To acoustically assess the biomass of multiple species or taxa within a survey region, the volume backscatter data should be apportioned to the constituent sound scatterers. Typically, measured backscatter is attributed to certain species using predictions at different frequencies, mostly based on the difference in scattering at the frequencies of 38 and 120 kHz (dual frequency method). We used the full version of the stochastic distortedwave Born approximation (SDWBA) model to predict backscatter spectra for Meganyctiphanes norvegica and to explore the sensitivities of ΔMVBS to the model parameters, e.g. acoustic frequency and incidence angle, and animal density and sound speed contrast, length, and shape. The orientation is almost the unique parameter responsible for variation, with fatness affecting longer lengths. We present a summary of ΔMVBS that can serve as the basis for identification algorithms. Next, we simulate the scenario encountered in the Balearic Sea (western Mediterranean) where Northern krill are mixed with mesopelagic fish species (bristlemouths and lanternfishes), which are modeled with a prolate spheroid model. Simulated numerical data are employed to emulate the discrimination process with the most common identification techniques and typical survey frequencies. The importance of using density-independent techniques for acoustic classification is highlighted. Finally, an unsupervised neural network, the Self-Organizing Map (SOM), is used to cluster these theoretical data and identify the frequencies that provide, in this case, the most classification potential. The simulation results confirm that pairs of frequencies spanning the Rayleigh and geometric scattering regimes of the targets are the most useful for clustering; a minimum of four frequencies are necessary to separate the three species, while three frequencies are able to differentiate krill from mesopelagic fish species.

  18. Development of an Autonomous, Compact, Broadband Acoustic Backscattering System for Remote Characterization of Zooplankton Variability (PART II)

    DTIC Science & Technology

    2010-09-30

    temporal scales (e.g. Holliday and Pieper , 1980, 1995; Pieper et al., 1990; Napp et al., 1993; Wiebe et al., 1996; Benfield et al., 1998; Brierley et...Holliday, D.V. and Pieper , R.E. (1980). “Volume scattering strengths and zooplankton distributions at acoustic frequencies between 0.5 and 3 MHz,” J...Acoust. Soc. Am. 67(1), 135-146. Holliday, V.D. and Pieper , R.E. (1995). “Bioacoustical oceanography at high frequencies,” ICES J. Mar. Sci. 52

  19. Intermediate and High-Frequency Acoustic Backscattering Cross Sections for Water-Ice Interfaces: I. Two-Component Profile Models.

    DTIC Science & Technology

    2014-09-26

    Ice Research in the Arctic Ocean via Submarine," Trans. N.Y. Acad. of Sciences 23, 662-674, 1961. [2]. R. H. Mellen, "Underwater Acoustic Scattering...Backscattenng Cross Sections for Water- Ice Interfaces: I. Two.Component Profile Models r2avid Middleton CV) (Consultant) Associate Technical Director LC...Distribution unlimited. --. Preface This work was accomplished under NUSC’s Arctic Program, Code 01Y and Code 10. The sponsoring activity is the Naval

  20. Field Demonstration of a Broadband Acoustical Backscattering System Mounted on a REMUS-100 for Inferences of Zooplankton Size and Abundancy

    DTIC Science & Technology

    2011-09-30

    the Rayleigh-to-geometric scattering transition is within the frequency band of the WHOI broadband system (e.g., copepods ), and either larger fluid...that numerical abundance of zooplankton was dominated by small copepods that were relatively evenly distributed throughout the water-column...indication in either the MONESS or the VPR that the acoustic scattering layer was correlated to an increased abundance of zooplankton. Small copepods

  1. A novel imaging technique based on the spatial coherence of backscattered waves: demonstration in the presence of acoustical clutter

    NASA Astrophysics Data System (ADS)

    Dahl, Jeremy J.; Pinton, Gianmarco F.; Lediju, Muyinatu; Trahey, Gregg E.

    2011-03-01

    In the last 20 years, the number of suboptimal and inadequate ultrasound exams has increased. This trend has been linked to the increasing population of overweight and obese individuals. The primary causes of image degradation in these individuals are often attributed to phase aberration and clutter. Phase aberration degrades image quality by distorting the transmitted and received pressure waves, while clutter degrades image quality by introducing incoherent acoustical interference into the received pressure wavefront. Although significant research efforts have pursued the correction of image degradation due to phase aberration, few efforts have characterized or corrected image degradation due to clutter. We have developed a novel imaging technique that is capable of differentiating ultrasonic signals corrupted by acoustical interference. The technique, named short-lag spatial coherence (SLSC) imaging, is based on the spatial coherence of the received ultrasonic wavefront at small spatial distances across the transducer aperture. We demonstrate comparative B-mode and SLSC images using full-wave simulations that include the effects of clutter and show that SLSC imaging generates contrast-to-noise ratios (CNR) and signal-to-noise ratios (SNR) that are significantly better than B-mode imaging under noise-free conditions. In the presence of noise, SLSC imaging significantly outperforms conventional B-mode imaging in all image quality metrics. We demonstrate the use of SLSC imaging in vivo and compare B-mode and SLSC images of human thyroid and liver.

  2. Evaluating external nutrient and suspended-sediment loads to Upper Klamath Lake, Oregon, using surrogate regressions with real-time turbidity and acoustic backscatter data

    USGS Publications Warehouse

    Schenk, Liam N.; Anderson, Chauncey W.; Diaz, Paul; Stewart, Marc A.

    2016-12-22

    Executive SummarySuspended-sediment and total phosphorus loads were computed for two sites in the Upper Klamath Basin on the Wood and Williamson Rivers, the two main tributaries to Upper Klamath Lake. High temporal resolution turbidity and acoustic backscatter data were used to develop surrogate regression models to compute instantaneous concentrations and loads on these rivers. Regression models for the Williamson River site showed strong correlations of turbidity with total phosphorus and suspended-sediment concentrations (adjusted coefficients of determination [Adj R2]=0.73 and 0.95, respectively). Regression models for the Wood River site had relatively poor, although statistically significant, relations of turbidity with total phosphorus, and turbidity and acoustic backscatter with suspended sediment concentration, with high prediction uncertainty. Total phosphorus loads for the partial 2014 water year (excluding October and November 2013) were 39 and 28 metric tons for the Williamson and Wood Rivers, respectively. These values are within the low range of phosphorus loads computed for these rivers from prior studies using water-quality data collected by the Klamath Tribes. The 2014 partial year total phosphorus loads on the Williamson and Wood Rivers are assumed to be biased low because of the absence of data from the first 2 months of water year 2014, and the drought conditions that were prevalent during that water year. Therefore, total phosphorus and suspended-sediment loads in this report should be considered as representative of a low-water year for the two study sites. Comparing loads from the Williamson and Wood River monitoring sites for November 2013–September 2014 shows that the Williamson and Sprague Rivers combined, as measured at the Williamson River site, contributed substantially more suspended sediment to Upper Klamath Lake than the Wood River, with 4,360 and 1,450 metric tons measured, respectively.Surrogate techniques have proven useful at

  3. Chromospheric heating by acoustic shocks - A confrontation of GHRS observations of Alpha Tauri (K5 III) with ab initio calculations

    NASA Technical Reports Server (NTRS)

    Judge, P. G.; Cuntz, M.

    1993-01-01

    We compare ab initio calculations of semiforbidden C II line profiles near 2325 A with recently published observations of the inactive red giant Alpha Tau (K5 III) obtained using the GHRS on board the Hubble Space Telescope. Our one-dimensional, time-dependent calculations assume that the chromosphere is heated by stochastic acoustic shocks generated by photospheric convection. We calculate various models using results from traditional (mixing length) convection zone calculations as input to hydrodynamical models. The semiforbidden C II line profiles and ratios provide sensitive diagnostics of chromospheric velocity fields, electron densities, and temperatures. We identify major differences between observed and computed line profiles which are related to basic gas dynamics and which are probably not due to technical modeling restrictions. If the GHRS observations are representative of chromospheric conditions at all epochs, then one (or more) of our model assumptions must be incorrect. Several possibilities are examined. We predict time variability of semiforbidden C II lines for comparison with observations. Based upon data from the IUE archives, we argue that photospheric motions associated with supergranulation or global pulsation modes are unimportant in heating the chromosphere of Alpha Tau.

  4. Infrared backscattering

    NASA Technical Reports Server (NTRS)

    Bohren, Craig F.; Nevitt, Timothy J.; Singham, Shermila Brito

    1989-01-01

    All particles in the atmosphere are not spherical. Moreover, the scattering properties of randomly oriented nonspherical particles are not equivalent to those of spherical particles no matter how the term equivalent is defined. This is especially true for scattering in the backward direction and at the infrared wavelengths at which some atmospheric particles have strong absorption bands. Thus calculations based on Mie theory of infrared backscattering by dry or insoluble atmospheric particles are suspect. To support this assertion, it was noted that peaks in laboratory-measured infrared backscattering spectra show appreciable shifts compared with those calculated using Mie theory. One example is ammonium sulfate. Some success was had in modeling backscattering spectra of ammonium sulfate particles using a simple statistical theory called the continuous distribution of ellipsoids (CDE) theory. In this theory, the scattering properties of an ensemble are calculated. Recently a modified version of this theory was applied to measured spectra of scattering by kaolin particles. The particles were platelike, so the probability distribution of ellipsoidal shapes was chosen to reflect this. As with ammonium sulfate, the wavelength of measured peak backscattering is shifted longward of that predicted by Mie theory.

  5. Evaluation of suspended sediment concentrations, sediment fluxes and sediment depositions along a reservoir by using laser diffraction and acoustic backscatter data

    NASA Astrophysics Data System (ADS)

    Lizano, Laura; Haun, Stefan

    2015-04-01

    Costa Rica was investigated where huge depositions have been recorded since the reservoir was built. The SSC's were measured with a LISST-SL (Laser In-Situ Scattering and Transmissometry instrument) which is based on the laser diffraction method and measures simultaneously the SSC as well as the particle size distribution. The measured SSC's were subsequently used to calculate the sediment fluxes within the transects, based on the intensity of backscattered sound from an acoustic measurement device. The total amount of deposited sediments could be calculated from the sediment fluxes, obtained by moving ADCP measurements (Acoustic Doppler Current Profiler) along chosen transects and so an image of the amount of settled sediments could be drawn. The results of this study show the advantage of using two highly sophisticated measurement devices in parallel to receive accurate numbers for sediment fluxes within reservoirs, which can in addition be used in further studies to develop management strategies to reduce sediment depositions.

  6. Use of acoustic backscatter and vertical velocity to estimate concentration and dynamics of suspended solids in Upper Klamath Lake, south-central Oregon: Implications for Aphanizomenon flos-aquae

    USGS Publications Warehouse

    Wood, Tamara M.; Gartner, Jeffrey W.

    2010-01-01

    Vertical velocity and acoustic backscatter measurements by acoustic Doppler current profilers were used to determine seasonal, subseasonal (days to weeks), and diel variation in suspended solids in a freshwater lake where massive cyanobacterial blooms occur annually. During the growing season, the suspended material in the lake is dominated by the buoyancy-regulating cyanobacteria, Aphanizomenon flos-aquae. Measured variables (water velocity, relative backscatter [RB], wind speed, and air and water temperatures) were averaged over the deployment season at each sample time of day to determine average diel cycles. Phase shifts between diel cycles in RB and diel cycles in wind speed, vertical water temperature differences (delta T(degree)), and horizontal current speeds were found by determining the lead or lag that maximized the linear correlation between the respective diel cycles. Diel cycles in RB were more in phase with delta T(degree) cycles, and, to a lesser extent, wind cycles, than to water current cycles but were out of phase with the cycle that would be expected if the vertical movement of buoyant cyanobacteria colonies was controlled primarily by light. Clear evidence of a diel cycle in vertical velocity was found only at the two deepest sites in the lake. Cycles of vertical velocity, where present, were out of phase with expected vertical motion of cyanobacterial colonies based on the theoretical cycle for light-driven vertical movement. This suggests that water column stability and turbulence were more important factors in controlling vertical distribution of colonies than light. Variations at subseasonal time scales were determined by filtering data to pass periods between 1.2 and 15 days. At subseasonal time scales, correlations between RB and currents or air temperature were consistent with increased concentration of cyanobacterial colonies near the surface when water column stability increased (higher air temperatures or weaker currents) and

  7. Acoustics

    NASA Technical Reports Server (NTRS)

    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.

  8. Project PROBE Leg I - Report and archive of multibeam bathymetry and acoustic backscatter , CTD/XBT and GPS navigation data collected during USGS Cruise 02051 (NOAA Cruise RB0208) Puerto Rico Trench September 24, 2002 to September 30, 2002

    USGS Publications Warehouse

    ten Brink, Uri S.; Worley, Charles R.; Smith, Shep; Stepka, Thomas; Williams, Glynn F.

    2006-01-01

    On September 24-30, 2002, six days of scientific surveying to map a section of the Puerto Rico Trench (PRT) took place aboard the National Oceanic and Atmospheric Administration (NOAA) ship Ron Brown. The cruise was funded by NOAA's Office of Ocean Exploration. Multibeam bathymetry and acoustic-backscatter data were collected over an area of about 25,000 sq. km of the Puerto Rico trench and its vicinity at water depths of 4000-8400 m. Weather conditions during the entire survey were good; there were light to moderate winds and 1-2 foot swells experiencing minor chop. The roll and pitch of the ship's interaction with the ocean were not conspicuous. Cruise participants included personnel from USGS, NOAA, and University of New Hampshire Center for Coastal and Ocean Mapping/Joint Hydrographic Center. The cruise resulted in the discovery of a major active strike-slip fault system close to the trench, submarine slides on the descending North American tectonic plate, and an extinct mud volcano, which was cut by the strike-slip fault system. Another strike-slip fault system closer to Puerto Rico that was previously considered to accommodate much of the relative plate motion appears to be inactive. The seaward continuation of the Mona Rift, a zone of extension between Puerto Rico and the Dominican Republic that generated a devastating tsunami in 1918, was mapped for the first time.

  9. Effects of Ion-Ion Collisions and Inhomogeneity in Two-Dimensional Kinetic Ion Simulations of Stimulated Brillouin Backscattering

    SciTech Connect

    Cohen, B I; Divol, L; Langdon, A B; Williams, E A

    2005-10-17

    Two-dimensional simulations with the BZOHAR [B.I. Cohen, B.F. Lasinski, A.B. Langdon, and E.A. Williams, Phys. Plasmas 4, 956 (1997)] hybrid code (kinetic particle ions and Boltzmann fluid electrons) have been used to investigate the saturation of stimulated Brillouin backscatter (SBBS) instability including the effects of ion-ion collisions and inhomogeneity. Ion-ion collisions tend to increase ion-wave dissipation, which decreases the gain exponent for stimulated Brillouin backscattering; and the peak Brillouin backscatter reflectivities tend to decrease with increasing collisionality in the simulations. Two types of Langevin-operator, ion-ion collision models were implemented in the simulations. In both models used the collisions are functions of the local ion temperature and density, but the collisions have no velocity dependence in the first model. In the second model, the collisions are also functions of the energy of the ion that is being scattered so as to represent a Fokker-Planck collision operator. Collisions decorrelate the ions from the acoustic waves in SBS, which disrupts ion trapping in the acoustic wave. Nevertheless, ion trapping leading to a hot ion tail and two-dimensional physics that allows the SBS ion waves to nonlinearly scatter remain robust saturation mechanisms for SBBS in a high-gain limit over a range of ion collisionality. SBS backscatter in the presence of a spatially nonuniform plasma flow is also investigated. Simulations show that depending on the sign of the spatial gradient of the flow relative to the backscatter, ion trapping effects that produce a nonlinear frequency shift can enhance (auto-resonance) or decrease (anti-auto-resonance) reflectivities in agreement with theoretical arguments.

  10. Dynamic coherent backscattering mirror

    PubMed Central

    Xu, M.

    2016-01-01

    The phase of multiply scattered light has recently attracted considerable interest. Coherent backscattering is a striking phenomenon of multiple scattered light in which the coherence of light survives multiple scattering in a random medium and is observable in the direction space as an enhancement of the intensity of backscattered light within a cone around the retroreflection direction. Reciprocity also leads to enhancement of backscattering light in the spatial space. The random medium behaves as a reciprocity mirror which robustly converts a diverging incident beam into a converging backscattering one focusing at a conjugate spot in space. Here we first analyze theoretically this coherent backscattering mirror (CBM) phenomenon and then demonstrate the capability of CBM compensating and correcting both static and dynamic phase distortions occurring along the optical path. CBM may offer novel approaches for high speed dynamic phase corrections in optical systems and find applications in sensing and navigation. PMID:26937296

  11. Dynamic coherent backscattering mirror

    SciTech Connect

    Zeylikovich, I.; Xu, M.

    2016-02-15

    The phase of multiply scattered light has recently attracted considerable interest. Coherent backscattering is a striking phenomenon of multiple scattered light in which the coherence of light survives multiple scattering in a random medium and is observable in the direction space as an enhancement of the intensity of backscattered light within a cone around the retroreflection direction. Reciprocity also leads to enhancement of backscattering light in the spatial space. The random medium behaves as a reciprocity mirror which robustly converts a diverging incident beam into a converging backscattering one focusing at a conjugate spot in space. Here we first analyze theoretically this coherent backscattering mirror (CBM) phenomenon and then demonstrate the capability of CBM compensating and correcting both static and dynamic phase distortions occurring along the optical path. CBM may offer novel approaches for high speed dynamic phase corrections in optical systems and find applications in sensing and navigation.

  12. Preliminary Analysis of Low-Frequency Backscatter Data from the Blake Escarpment

    DTIC Science & Technology

    1990-06-01

    distr ibtion and strength of acoustic energy backscattered fromot1e Blake Escarpment. The angular variability of backscatter surces on the Blake...data where scattered energy has been transformed to the appropriate scattering surface) are used to estimate the size and distribution of scatterers...In Figure 4 strong backscattered energy centered at 2.4 km range with reflection times less than 1.0 s denote a promontory near the top of the

  13. NOAA backscatter studies

    NASA Technical Reports Server (NTRS)

    Post, Madison J.

    1991-01-01

    In the past year, NOAA has measured and analyzed another year's worth of backscatter over Boulder, CO. The average profile was computed from 80 satellite observations of backscatter spread throughout the year, using NOAA's CO2 coherent lidar operating at a wavelength of 10.59 microns. The seasonal averages show a familiar trend (highest backscattering in spring, perhaps due to Asian dust or biomass burning, and lowest backscattering in fall). The 1990 average profile was not significantly different from the 1988 or 1989 profiles, except that it displays a slight increase in the upper troposphere, perhaps due to the Redoubt Volcano. The NOAA's backscatter processing program (BETA) was refined to enable the calculation of gaseous absorption effects based on rawinsonde measurements, as well as using atmospheric models. NOAA participated in two intercomparisons of aerosol measuring instruments near Boulder, called FRLAB (Front Range Lidar, Aircraft, and Balloon Experiment). Considerable effort was also put into developing a multiagency science proposal to NASA headquarters to work with both JPL and NASA-Marshall to produce an airborne Doppler lidar facility for the DC-8.

  14. GLOBE backscatter - Climatologies and mission results. [Global Backscatter Experiment

    NASA Technical Reports Server (NTRS)

    Menzies, Robert T.; Post, Madison J.

    1991-01-01

    The Global Backscatter Experiment (GLOBE) goals require intensive study of the global climatology of atmospheric aerosol backscatter at IR wavelengths. Airborne and ground-based lidars have been developed to measure atmospheric backscatter profiles at CO2 laser wavelengths. Descriptions of the calibration techniques and selected measurement results are presented.

  15. THERMAL NEUTRON BACKSCATTER IMAGING.

    SciTech Connect

    VANIER,P.; FORMAN,L.; HUNTER,S.; HARRIS,E.; SMITH,G.

    2004-10-16

    Objects of various shapes, with some appreciable hydrogen content, were exposed to fast neutrons from a pulsed D-T generator, resulting in a partially-moderated spectrum of backscattered neutrons. The thermal component of the backscatter was used to form images of the objects by means of a coded aperture thermal neutron imaging system. Timing signals from the neutron generator were used to gate the detection system so as to record only events consistent with thermal neutrons traveling the distance between the target and the detector. It was shown that this time-of-flight method provided a significant improvement in image contrast compared to counting all events detected by the position-sensitive {sup 3}He proportional chamber used in the imager. The technique may have application in the detection and shape-determination of land mines, particularly non-metallic types.

  16. A relationship between ultrasonic integrated backscatter and myocardial contractile function.

    PubMed Central

    Wickline, S A; Thomas, L J; Miller, J G; Sobel, B E; Perez, J E

    1985-01-01

    We have shown previously that the physiologic, mechanical cardiac cycle is associated with a parallel, cardiac cycle-dependent variation of integrated backscatter (IB). However, the mechanisms responsible are not known. The mathematical and physiological considerations explored in the present study suggest that the relationship between backscatter and myocardial contractile function reflects cyclic alterations in myofibrillar elastic parameters, with the juxtaposition of intracellular and extracellular elastic elements that have different intrinsic acoustic impedances providing an appropriately sized scattering interface at the cellular level. Cardiac cycle-dependent changes in the degree of local acoustic impedance mismatch therefore may elicit concomitant changes in backscatter. Because acoustic impedance is determined partly by elastic modulus, changes in local elastic moduli resulting from the non-Hookian behavior of myocardial elastic elements exposed to stretch may alter the extent of impedance mismatch. When cardiac cell mechanical behavior is represented by a three-component Maxwell-type model of muscle mechanics, the systolic decrease in IB that we have observed experimentally is predicted. Our prior observations of regional intramural differences in IB and the dependence of IB on global contractile function are accounted for as well. When the model is tested experimentally by assessing its ability to predict the regional and global behavior of backscatter in response to passive left ventricular distention, good concordance is observed. Images PMID:3908482

  17. Recovering an electromagnetic obstacle by a few phaseless backscattering measurements

    NASA Astrophysics Data System (ADS)

    Li, Jingzhi; Liu, Hongyu; Wang, Yuliang

    2017-03-01

    We consider the electromagnetic scattering from a convex polyhedral PEC or PMC obstacle due to a time-harmonic incident plane wave. It is shown that the modulus of the far-field pattern in the backscattering aperture possesses a certain local maximum behavior. Using the local maximum indicating phenomena, one can determine the exterior unit normal directions, as well as the face areas, of the front faces of the obstacle. Then we propose a recovery scheme of reconstructing the obstacle by phaseless backscattering measurements. This work significantly extends our recent study in Li and Liu (2014 preprint) from two dimensions and acoustic scattering to the more challenging three dimensions and electromagnetic scattering.

  18. Quantifying Fish Backscattering using SONAR Instrument and Kirchhoff Ray Mode (KRM) Model

    NASA Astrophysics Data System (ADS)

    Manik, Henry M.

    2016-08-01

    Sonar instrument was used to study backscattering from tuna fish. Extraction of target strength, incidence angle, and frequency dependence of the backscattered signal for individual scatterer was important for biological information. For this purpose, acoustic measurement of fish backscatter was conducted in the laboratory. Characteristics and general trends of the target strength of fish with special reference to tuna fish were investigated by using a Kirchhoff Ray Mode (KRM) model. Backscattering strength were calculated for the KRM having typical morphological and physical parameters of actual fish. Those backscattering amplitudes were shown as frequency, body length, backscattering patterns, the density and sound speed dependences, and orientation dependence. These results were compared with experimentally measured target strength data and good agreement was found. Measurement and model showed the target strength from the fish are depend on the presence of swimbladder. Target Strength increase with increasing the frequency and fish length.

  19. In-situ optical and acoustical measurements of the buoyant cyanobacterium p. Rubescens: spatial and temporal distribution patterns.

    PubMed

    Hofmann, Hilmar; Peeters, Frank

    2013-01-01

    Optical (fluorescence) and acoustic in-situ techniques were tested in their ability to measure the spatial and temporal distribution of plankton in freshwater ecosystems with special emphasis on the harmful and buoyant cyanobacterium P. rubescens. Fluorescence was measured with the multi-spectral FluoroProbe (Moldaenke FluoroProbe, MFP) and a Seapoint Chlorophyll Fluorometer (SCF). In-situ measurements of the acoustic backscatter strength (ABS) were conducted with three different acoustic devices covering multiple acoustic frequencies (614 kHz ADCP, 2 MHz ADP, and 6 MHz ADV). The MFP provides a fast and reliable technique to measure fluorescence at different wavelengths in situ, which allows discriminating between P. rubescens and other phytoplankton species. All three acoustic devices are sensitive to P. rubescens even if other scatterers, e.g., zooplankton or suspended sediment, are present in the water column, because P. rubescens containing gas vesicles has a strong density difference and hence acoustic contrast to the ambient water and other scatterers. After calibration, the combination of optical and acoustical measurements not only allows qualitative and quantitative observation of P. rubescens, but also distinction between P. rubescens, other phytoplankton, and zooplankton. As the measuring devices can sample in situ at high rates they enable assessment of plankton distributions at high temporal (minutes) and spatial (decimeters) resolution or covering large temporal (seasonal) and spatial (basin scale) scales.

  20. Side-looking sonar backscatter response at dual frequencies

    NASA Astrophysics Data System (ADS)

    Ryan, William B. F.; Flood, Roger D.

    1996-12-01

    Dual-frequency side-looking sonars have the potential to be used as remote sensing tools to characterize subaqueous terrains. In one case study of the carbonate-ooze-coated Blake Plateau off-shore of Georgia, U.S.A., the difference in acoustic attenuation for 50 and 20 mm wavelengths (30 and 72 kHz frequency) permits the discrimination of sub-bottom scatterers from seabed surface textural features to reveal patchy regions where a buried hard ground had been pock-marked by karst-like depressions. In a second study of the Upper Hudson River in New York, U.S.A., related to environmental contaminates, the backscatter response at 15 and 3 mm acoustic wavelengths (100 and 500 kHz frequency) serves as a useful proxy for sediment grain size with coarser detritus distinguished from finer sediments. Sand and gravel regions inferred from the backscatter were confirmed by ground truth sampling.

  1. Aerosol backscatter studies supporting LAWS

    NASA Technical Reports Server (NTRS)

    Rothermel, Jeffry

    1989-01-01

    Optimized Royal Signals and Radar Establishment (RSRE), Laser True Airspeed System (LATAS) algorithm for low backscatter conditions was developed. The algorithm converts backscatter intensity measurements from focused continuous-wave (CW) airborne Doppler lidar into backscatter coefficients. The performance of optimized algorithm under marginal backscatter signal conditions was evaluated. The 10.6 micron CO2 aerosol backscatter climatologies were statistically analyzed. Climatologies reveal clean background aerosol mode near 10(exp -10)/kg/sq m/sr (mixing ratio units) through middle and upper troposhere, convective mode associated with planetary boundary layer convective activity, and stratospheric mode associated with volcanically-generated aerosols. Properties of clean background mode are critical to design and simulation studies of Laser Atmospheric Wind Sounder (LAWS), a MSFC facility Instrument on the Earth Observing System (Eos). Previous intercomparisons suggested correlation between aerosol backscatter at CO2 wavelength and water vapor. Field measurements of backscatter profiles with MSFC ground-based Doppler lidar system (GBDLS) were initiated in late FY-88 to coincide with independent program of local rawinsonde releases and overflights by Multi-spectral Atmospheric Mapping Sensor (MAMS), a multi-channel infrared radiometer capable of measuring horizontal and vertical moisture distributions. Design and performance simulation studies for LAWS would benefit from the existence of a relationship between backscatter and water vapor.

  2. Backscattering of agglomerate particles

    NASA Astrophysics Data System (ADS)

    Zubko, Evgenij; Ovcharenko, Andrey; Bondarenko, Sergey; Shkuratov, Yuriy; Scotto, Cathy S.; Merritt, Charles; Hart, Matthew B.; Eversole, Jay D.; Videen, Gorden W.

    2004-12-01

    We examine how aggregation affects the light-scattering signatures, especially the polarization in the near-backward-scattering direction. We use the discrete dipole approximation (DDA) to study the backscatter of agglomerate particles consisting of oblong monomers. We examine the effects of monomer number and packing structure on the resulting negative polarization branch at small phase angle. We find large a dependence on the orientation of the monomers within the agglomerate and a smaller dependence on the number of monomers, suggesting that the mechanism producing the negative polarization minimum depends strongly on the interactions between the individual monomers. We also examine experimental measurements of substrates composed of biological cells. We find that the light-scattering signatures in the backward direction are not only different for different spore species, but for spores that have been prepared using different methodologies. These signatures are reproducible in different substrates composed of the spores from the same batches.

  3. Riverbed sediment classification using multi-beam echo-sounder backscatter data.

    PubMed

    Amiri-Simkooei, AliReza; Snellen, Mirjam; Simons, Dick G

    2009-10-01

    A method has recently been developed that employs multi-beam echo-sounder backscatter data to both obtain the number of sediment classes and discriminate between them by applying the Bayes decision rule to multiple hypotheses [Simons and Snellen, Appl. Acoust. 70, 1258-1268 (2009)]. In deep water, the number of scatter pixels within the beam footprint is large enough to ensure Gaussian distributions for the backscatter strengths and to increase the discriminative power between acoustic classes. In very shallow water (<10 m), however, this number is too small. This paper presents an extension of this high-frequency methodology for these environments, together with a demonstration of its performance using backscatter data from the river Waal, The Netherlands. The objective of this work is threefold. (i) Increasing the discriminating power of the classification method: high-resolution bathymetry data allow precise bottom slope corrections for obtaining the true incident angle, and the high-resolution backscatter data reduce the statistical fluctuations via an averaging procedure. (ii) Performing a correlation analysis: the dependence of acoustic backscatter classification on sediment physical properties is verified by observing a significant correlation of 0.75 (and a disattenuated correlation of 0.90) between the classification results and sediment mean grain size. (iii) Enhancing the statistical description of the backscatter intensities: angular evolution of the K-distribution shape parameter indicates that the riverbed is a rough surface, in agreement with the results of the core analysis.

  4. Acoustic iridescence.

    PubMed

    Cox, Trevor J

    2011-03-01

    An investigation has been undertaken into acoustic iridescence, exploring how a device can be constructed which alter sound waves, in a similar way to structures in nature that act on light to produce optical iridescence. The main construction had many thin perforated sheets spaced half a wavelength apart for a specified design frequency. The sheets create the necessary impedance discontinuities to create backscattered waves, which then interfere to create strongly reflected sound at certain frequencies. Predictions and measurements show a set of harmonics, evenly spaced in frequency, for which sound is reflected strongly. And the frequency of these harmonics increases as the angle of observation gets larger, mimicking the iridescence seen in natural optical systems. Similar to optical systems, the reflections become weaker for oblique angles of reflection. A second construction was briefly examined which exploited a metamaterial made from elements and inclusions which were much smaller than the wavelength. Boundary element method predictions confirmed the potential for creating acoustic iridescence from layers of such a material.

  5. Acoustic neuroma

    MedlinePlus

    Vestibular schwannoma; Tumor - acoustic; Cerebellopontine angle tumor; Angle tumor; Hearing loss - acoustic; Tinnitus - acoustic ... Acoustic neuromas have been linked with the genetic disorder neurofibromatosis type 2 (NF2). Acoustic neuromas are uncommon.

  6. Remembering AB

    NASA Astrophysics Data System (ADS)

    Belyayev, S. T.

    2013-06-01

    In 1947 I became a second-year student at Moscow State University's Physics and Engineering Department, where a part of the week's classes were taught at base organizations. Our group's base was the future Kurchatov Institute, at that time known as the mysterious "Laboratory N^circ 2," and later as LIPAN. . Besides group lectures and practical work at the experimental laboratories, we also had access to the general seminars which Igor Vasilyevich Kurchatov tried to hold, with Leonid Vasilyevich Groshev filling in when he was absent. At the seminar, theorists spoke as welcome co-presenters and commentators. In 1949 I felt ready to approach A. B. Migdal to ask if I could transfer to his theoretical sector. In response, he suggested a number of simple qualitative problems, which I then successfully solved. (Incidentally, AB used the very same "introductory problems" for screening many generations of students.) So I wound up among AB's students. From 1952 on (for 10 years) I also served as an employee of the Migdal Sector. My memoirs here are mainly inspired by these years of constant communication with AB. After my departure for Novosibirsk in 1962, although our meetings still took place, they became occasional....

  7. Stimulated brillouin backscatter of a short-pulse laser

    SciTech Connect

    Hinkel, D.E.; Williams, E.A.; Berger, R.L.

    1994-11-03

    Stimulated Brillouin backscattering (SBBS) from a short-pulse laser, where the pulse length is short compared to the plasma length, is found to be qualitatively different than in the long pulse regime, where the pulse length is long compared to the plasma length. We find that after an initial transient of order the laser pulse length transit time, the instability reaches a steady state in the variables x{prime} = x {minus} V{sub g}t, t{prime} = t, where V{sub g} is the pulse group velocity. In contrast, SBBS in a long pulse can be absolutely unstable and grows indefinitely, or until nonlinearities intervene. We find that the motion of the laser pulse induces Doppler related effects that substantially modify the backscattered spectrum at higher intensities, where the instability is strongly coupled (i.e. , has a growth rate large compared to the ion acoustic frequency).

  8. A simulation algorithm for ultrasound liver backscattered signals.

    PubMed

    Zatari, D; Botros, N; Dunn, F

    1995-11-01

    In this study, we present a simulation algorithm for the backscattered ultrasound signal from liver tissue. The algorithm simulates backscattered signals from normal liver and three different liver abnormalities. The performance of the algorithm has been tested by statistically comparing the simulated signals with corresponding signals obtained from a previous in vivo study. To verify that the simulated signals can be classified correctly we have applied a classification technique based on an artificial neural network. The acoustic features extracted from the spectrum over a 2.5 MHz bandwidth are the attenuation coefficient and the change of speed of sound with frequency (dispersion). Our results show that the algorithm performs satisfactorily. Further testing of the algorithm is conducted by the use of a data acquisition and analysis system designed by the authors, where several simulated signals are stored in memory chips and classified according to their abnormalities.

  9. 3D Backscatter Imaging System

    NASA Technical Reports Server (NTRS)

    Turner, D. Clark (Inventor); Whitaker, Ross (Inventor)

    2016-01-01

    Systems and methods for imaging an object using backscattered radiation are described. The imaging system comprises both a radiation source for irradiating an object that is rotationally movable about the object, and a detector for detecting backscattered radiation from the object that can be disposed on substantially the same side of the object as the source and which can be rotationally movable about the object. The detector can be separated into multiple detector segments with each segment having a single line of sight projection through the object and so detects radiation along that line of sight. Thus, each detector segment can isolate the desired component of the backscattered radiation. By moving independently of each other about the object, the source and detector can collect multiple images of the object at different angles of rotation and generate a three dimensional reconstruction of the object. Other embodiments are described.

  10. Changes in backscatter of liver tissue due to thermal coagulation induced by focused ultrasound.

    PubMed

    Shishitani, Takashi; Matsuzawa, Ryo; Yoshizawa, Shin; Umemura, Shin-ichiro

    2013-08-01

    Ultrasonic imaging has advantages in its self-consistency in guiding and monitoring ultrasonic treatment such as high-intensity focused ultrasound (HIFU) treatment. Changes in ultrasonic backscatter of tissues due to HIFU treatment have been observed, but their mechanism is still under discussion. In this paper, ultrasonic backscatter of excised and degassed porcine liver tissue was observed before and after HIFU exposure using a diagnostic scanner, and its acoustic impedance was mapped using an ultrasonic microscope. The histology of its pathological specimen was also observed using an optical microscope. The observed decrease in backscatter intensity due to HIFU exposure was consistent with a spatial Fourier analysis of the histology, which also showed changes due to the exposure. The observed increase in acoustic impedance due to the exposure was also consistent with the histological change assuming that the increase was primarily caused by the increase in the concentration of hepatic cells.

  11. Photoelectron backscattering in vacuum phototubes

    NASA Astrophysics Data System (ADS)

    Lubsandorzhiev, B. K.; Vasiliev, R. V.; Vyatchin, Y. E.; Shaibonov, B. A. J.

    2006-11-01

    In this article we describe results of studies of a photoelectron backscattering effect in vacuum phototubes: classical photomultipliers (PMT) and hybrid phototubes (PH). Late pulses occurring in PMTs are attributed to the photoelectron backscattering and distinguished from pulses due to an anode glow effect. The late pulses are measured in a number of PMTs and HPs with various photocathode sizes covering 1 50 cm range and different types of the first dynode materials and construction designs. It is shown that the late pulses are a generic feature of all vacuum photodetectors—PMTs and PHs—and they do not deteriorate dramatically amplitude and timing responses of vacuum phototubes.

  12. Validation of automated supervised segmentation of multibeam backscatter data from the Chatham Rise, New Zealand

    NASA Astrophysics Data System (ADS)

    Hillman, Jess I. T.; Lamarche, Geoffroy; Pallentin, Arne; Pecher, Ingo A.; Gorman, Andrew R.; Schneider von Deimling, Jens

    2017-01-01

    Using automated supervised segmentation of multibeam backscatter data to delineate seafloor substrates is a relatively novel technique. Low-frequency multibeam echosounders (MBES), such as the 12-kHz EM120, present particular difficulties since the signal can penetrate several metres into the seafloor, depending on substrate type. We present a case study illustrating how a non-targeted dataset may be used to derive information from multibeam backscatter data regarding distribution of substrate types. The results allow us to assess limitations associated with low frequency MBES where sub-bottom layering is present, and test the accuracy of automated supervised segmentation performed using SonarScope® software. This is done through comparison of predicted and observed substrate from backscatter facies-derived classes and substrate data, reinforced using quantitative statistical analysis based on a confusion matrix. We use sediment samples, video transects and sub-bottom profiles acquired on the Chatham Rise, east of New Zealand. Inferences on the substrate types are made using the Generic Seafloor Acoustic Backscatter (GSAB) model, and the extents of the backscatter classes are delineated by automated supervised segmentation. Correlating substrate data to backscatter classes revealed that backscatter amplitude may correspond to lithologies up to 4 m below the seafloor. Our results emphasise several issues related to substrate characterisation using backscatter classification, primarily because the GSAB model does not only relate to grain size and roughness properties of substrate, but also accounts for other parameters that influence backscatter. Better understanding these limitations allows us to derive first-order interpretations of sediment properties from automated supervised segmentation.

  13. Backscatter measurements for NIF ignition targets (invited).

    PubMed

    Moody, J D; Datte, P; Krauter, K; Bond, E; Michel, P A; Glenzer, S H; Divol, L; Niemann, C; Suter, L; Meezan, N; MacGowan, B J; Hibbard, R; London, R; Kilkenny, J; Wallace, R; Kline, J L; Knittel, K; Frieders, G; Golick, B; Ross, G; Widmann, K; Jackson, J; Vernon, S; Clancy, T

    2010-10-01

    Backscattered light via laser-plasma instabilities has been measured in early NIF hohlraum experiments on two beam quads using a suite of detectors. A full aperture backscatter system and near backscatter imager (NBI) instrument separately measure the stimulated Brillouin and stimulated Raman scattered light. Both instruments work in conjunction to determine the total backscattered power to an accuracy of ∼15%. In order to achieve the power accuracy we have added time-resolution to the NBI for the first time. This capability provides a temporally resolved spatial image of the backscatter which can be viewed as a movie.

  14. Backscatter absorption gas imaging system

    DOEpatents

    McRae, T.G. Jr.

    A video imaging system for detecting hazardous gas leaks. Visual displays of invisible gas clouds are produced by radiation augmentation of the field of view of an imaging device by radiation corresponding to an absorption line of the gas to be detected. The field of view of an imager is irradiated by a laser. The imager receives both backscattered laser light and background radiation. When a detectable gas is present, the backscattered laser light is highly attenuated, producing a region of contrast or shadow on the image. A flying spot imaging system is utilized to synchronously irradiate and scan the area to lower laser power requirements. The imager signal is processed to produce a video display.

  15. Backscatter absorption gas imaging system

    DOEpatents

    McRae, Jr., Thomas G.

    1985-01-01

    A video imaging system for detecting hazardous gas leaks. Visual displays of invisible gas clouds are produced by radiation augmentation of the field of view of an imaging device by radiation corresponding to an absorption line of the gas to be detected. The field of view of an imager is irradiated by a laser. The imager receives both backscattered laser light and background radiation. When a detectable gas is present, the backscattered laser light is highly attenuated, producing a region of contrast or shadow on the image. A flying spot imaging system is utilized to synchronously irradiate and scan the area to lower laser power requirements. The imager signal is processed to produce a video display.

  16. Electromagnetic backscattering by corner reflectors

    NASA Technical Reports Server (NTRS)

    Balanis, C. A.; Griesser, T.

    1986-01-01

    The Geometrical Theory of Diffraction (GTD), which supplements Geometric Optics (GO), and the Physical Theory of Diffraction (PTD), which supplements Physical Optics (PO), are used to predict the backscatter cross sections of dihedral corner reflectors which have right, obtuse, or acute included angles. These theories allow individual backscattering mechanisms of the dihedral corner reflectors to be identified and provide good agreement with experimental results in the azimuthal plane. The advantages and disadvantages of the geometrical and physical theories are discussed in terms of their accuracy, usefulness, and complexity. Numerous comparisons of analytical results with experimental data are presented. While physical optics alone is more accurate and more useful than geometrical optics alone, the combination of geometrical optics and geometrical diffraction seems to out perform physical optics and physical diffraction when compared with experimental data, especially for acute angle dihedral corner reflectors.

  17. Los Angeles and San Diego Margin High-Resolution Multibeam Bathymetry and Backscatter Data

    USGS Publications Warehouse

    Dartnell, Peter; Gardner, James V.; Mayer, Larry A.; Hughes-Clarke, John E.

    2004-01-01

    Summary -- The U.S. Geological Survey in cooperation with the University of New Hampshire and the University of New Brunswick mapped the nearshore regions off Los Angeles and San Diego, California using multibeam echosounders. Multibeam bathymetry and co-registered, corrected acoustic backscatter were collected in water depths ranging from about 3 to 900 m offshore Los Angeles and in water depths ranging from about 17 to 1230 m offshore San Diego. Continuous, 16-m spatial resolution, GIS ready format data of the entire Los Angeles Margin and San Diego Margin are available online as separate USGS Open-File Reports. For ongoing research, the USGS has processed sub-regions within these datasets at finer resolutions. The resolution of each sub-region was determined by the density of soundings within the region. This Open-File Report contains the finer resolution multibeam bathymetry and acoustic backscatter data that the USGS, Western Region, Coastal and Marine Geology Team has processed into GIS ready formats as of April 2004. The data are available in ArcInfo GRID and XYZ formats. See the Los Angeles or San Diego maps for the sub-region locations. These datasets in their present form were not originally intended for publication. The bathymetry and backscatter have data-collection and processing artifacts. These data are being made public to fulfill a Freedom of Information Act request. Care must be taken not to confuse artifacts with real seafloor morphology and acoustic backscatter.

  18. Measuring Ultrasonic Backscatter in the Presence of Nonlinear Propagation

    NASA Astrophysics Data System (ADS)

    Stiles, Timothy; Guerrero, Quinton

    2011-11-01

    A goal of medical ultrasound is the formation of quantitative ultrasound images in which contrast is determined by acoustic or physical properties of tissue rather than relative echo amplitude. Such images could greatly enhance early detection of many diseases, including breast cancer and liver cirrhosis. Accurate determination of the ultrasonic backscatter coefficient from patients remains a difficult task. One reason for this difficulty is the inherent nonlinear propagation of ultrasound at high intensities used for medical imaging. The backscatter coefficient from several tissue-mimicking samples were measured using the planar reflector method. In this method, the power spectrum from a sample is compared to the power spectrum of an optically flat sample of quartz. The results should be independent of incident pressure amplitude. Results demonstrate that backscatter coefficients can vary by more than an order of magnitude when ultrasound pressure varies from 0.1 MPa to 1.5 MPa at 5.0 MHz. A new method that incorporates nonlinear propagation is proposed to explain these discrepancies.

  19. Coherent and incoherent ultrasound backscatter from cell aggregates.

    PubMed

    de Monchy, Romain; Destrempes, François; Saha, Ratan K; Cloutier, Guy; Franceschini, Emilie

    2016-09-01

    The effective medium theory (EMT) was recently developed to model the ultrasound backscatter from aggregating red blood cells [Franceschini, Metzger, and Cloutier, IEEE Trans. Ultrason. Ferroelectr. Freq. Control 58, 2668-2679 (2011)]. The EMT assumes that aggregates can be treated as homogeneous effective scatterers, which have effective properties determined by the aggregate compactness and the acoustical characteristics of the cells and the surrounding medium. In this study, the EMT is further developed to decompose the differential backscattering cross section of a single cell aggregate into coherent and incoherent components. The coherent component corresponds to the squared norm of the average scattering amplitude from the effective scatterer, and the incoherent component considers the variance of the scattering amplitude (i.e., the mean squared norm of the fluctuation of the scattering amplitude around its mean) within the effective scatterer. A theoretical expression for the incoherent component based on the structure factor is proposed and compared with another formulation based on the Gaussian direct correlation function. This theoretical improvement is assessed using computer simulations of ultrasound backscatter from aggregating cells. The consideration of the incoherent component based on the structure factor allows us to approximate the simulations satisfactorily for a product of the wavenumber times the aggregate radius krag around 2.

  20. Interlaboratory comparison of backscatter coefficient estimates for tissue-mimicking phantoms.

    PubMed

    Anderson, Janelle J; Herd, Maria-Teresa; King, Michael R; Haak, Alexander; Hafez, Zachary T; Song, Jun; Oelze, Michael L; Madsen, Ernest L; Zagzebski, James A; O'Brien, William D; Hall, Timothy J

    2010-01-01

    Ultrasonic backscatter is useful for characterizing tissues and several groups have reported methods for estimating backscattering properties. Previous interlaboratory comparisons have been made to test the ability to accurately estimate the backscatter coefficient (BSC) by different laboratories around the world. Results of these comparisons showed variability in BSC estimates but were acquired only for a relatively narrow frequency range, and, most importantly, lacked reference to any independent predictions from scattering theory. The goal of this study was to compare Faran-scattering-theory predictions with cooperatively-measured backscatter coefficients for low-attenuating and tissue-like attenuating phantoms containing glass sphere scatterers of different sizes for which BSCs can independently be predicted. Ultrasonic backscatter measurementswere made for frequencies from 1 to 12 MHz. Backscatter coefficients were estimated using two different planar-reflector techniques at two laboratories for two groups of phantoms. Excellent agreement was observed between BSC estimates from both laboratories. In addition, good agreement with the predictions of Faran's theory was obtained, with average fractional (bias) errors ranging from 8-14%. This interlaboratory comparison demonstrates the ability to accurately estimate parameters derived from the BSC, including an effective scatterer size and the acoustic concentration, both of which may prove useful for diagnostic applications of ultrasound tissue characterization.

  1. Deep Seafloor Acoustic Backscattering Measurements Using Sea Beam

    DTIC Science & Technology

    1985-12-01

    seafloor down to maximum ocean depth (11 km). Since 1977 when the first system became operational aboard the French R/V Jean Charcot , nine other...Geological Observatory), Surveyor (National Oceanographic • and Atmospheric Administration), and Jean Charcot (IFREMER). Sea Beam •investigators who...1967. Renard, V. and J. P. Allenou, Seabeam, multi-beam echo-sounding in " Jean Charcot " . Description, evaluation and first results, Internat’l

  2. Acoustic Neuroma

    MedlinePlus

    ... search IRSA's site Unique Hits since January 2003 Acoustic Neuroma Click Here for Acoustic Neuroma Practice Guideline ... to microsurgery. One doctor's story of having an acoustic neuroma In August 1991, Dr. Thomas F. Morgan ...

  3. Observations of backscatter from sand and gravel seafloors between 170 and 250 kHz.

    PubMed

    Weber, Thomas C; Ward, Larry G

    2015-10-01

    Interpreting observations of frequency-dependence in backscatter from the seafloor offers many challenges, either because multiple frequencies are used for different observations that will later be merged or simply because seafloor scattering models are not well-understood above 100 kHz. Hindering the understanding of these observations is the paucity of reported, calibrated acoustic measurements above 100 kHz. This manuscript seeks to help elucidate the linkages between seafloor properties and frequency-dependent seafloor backscatter by describing observations of backscatter collected from sand, gravel, and bedrock seafloors at frequencies between 170 and 250 kHz and at a grazing angle of 45°. Overall, the frequency dependence appeared weak for all seafloor types, with a slight increase in seafloor scattering strength with increasing frequency for an area with unimodal, very poorly to moderately well sorted, slightly granular to granular medium sand with significant amounts of shell debris and a slight decrease in all other locations.

  4. Sidescan backscatter variations of cold seeps on the Hikurangi Margin (New Zealand): indications for different stages in seep development

    NASA Astrophysics Data System (ADS)

    Dumke, Ines; Klaucke, Ingo; Berndt, Christian; Bialas, Jörg

    2014-06-01

    Cold seeps on the Hikurangi Margin off New Zealand exhibit various seabed morphologies producing different intensity patterns in sidescan backscatter images. Acoustic backscatter characteristics of 25 investigated seep sites fall into four distinct types characterised by variations in backscatter intensity, distribution and inferred structural heights. The types reflect different carbonate morphologies including up to 20-m-high structures (type 1), low-relief crusts (type 2), scattered blocks (type 3) and carbonate-free sites (type 4). Each seep corresponds to a single type; intermediates were not observed. This correlates well with published data on seep fauna at each site, with the four types representing three different faunal habitats of successive stages of seep development. Backscatter signatures in sidescan sonar images of cold seeps may therefore serve as a convenient proxy for variations in faunal habitats.

  5. Beta Backscatter Measures the Hardness of Rubber

    NASA Technical Reports Server (NTRS)

    Morrissey, E. T.; Roje, F. N.

    1986-01-01

    Nondestructive testing method determines hardness, on Shore scale, of room-temperature-vulcanizing silicone rubber. Measures backscattered beta particles; backscattered radiation count directly proportional to Shore hardness. Test set calibrated with specimen, Shore hardness known from mechanical durometer test. Specimen of unknown hardness tested, and radiation count recorded. Count compared with known sample to find Shore hardness of unknown.

  6. Lake Michigan fish acoustic data from 2011 to 2016

    USGS Publications Warehouse

    Warner, David M.; Claramunt, Randall M.; Hanson, Dale

    2016-01-01

    Each line in the file “Lake Michigan fish acoustic data from 2011 to 2016.csv” represents the acoustic data and estimated fish density for a single depth layer of water. Surveys are conducted along transects, transects are divided horizontally into successive intervals, and then within an interval there are multiple successive depth layers. Area backscattering (ABC), mean acoustic size (sigma), and fish density are reported for each unique transect-interval – layer from Lake Michigan in the years 2011-2016. Area backscattering (PRC_ABC), mean acoustic size (sigma), and fish density in the intervals and layers of acoustic survey transects of Lake Michigan in the years 2011-2016. The survey is carried out using a stratified, systematic design with transect locations randomized within each stratum. As a result, transect location varies each year.

  7. Mobile spectrometer measures radar backscatter

    NASA Technical Reports Server (NTRS)

    Gogineni, S.; Moore, R. K.; Onstott, R. G.; Kim, Y. S.; Bushnell, D.

    1984-01-01

    The present article is concerned with a helicopter-borne spectrometer (Heloscat), which has been developed to permit high-quality scattering measurements from a mobile platform at remote sites. The term 'spectrometer' referes to a class of scatterometers. The term 'scatterometer' is employed to denote a specialized radar for measuring scattering coefficients as a function of angle. A spectrometer, on the other hand, is a scatterometer which can measure backscatter at several frequencies. The Heloscat system is discussed, taking into account two antennas, RF hardware, and an externally mounted pendulum for angle encoding. A dual-antenna configuration is used for cross-polarized measurements, while a single-antenna system is used for like-polarized measurements. Attention is also given to oscillator characteristics, efficient data handling, and aspects of calibration.

  8. Range compensation for backscattering measurements in the difference-frequency nearfield of a parametric sonar.

    PubMed

    Foote, Kenneth G

    2012-05-01

    Measurement of acoustic backscattering properties of targets requires removal of the range dependence of echoes. This process is called range compensation. For conventional sonars making measurements in the transducer farfield, the compensation removes effects of geometrical spreading and absorption. For parametric sonars consisting of a parametric acoustic transmitter and a conventional-sonar receiver, two additional range dependences require compensation when making measurements in the nonlinearly generated difference-frequency nearfield: an apparently increasing source level and a changing beamwidth. General expressions are derived for range compensation functions in the difference-frequency nearfield of parametric sonars. These are evaluated numerically for a parametric sonar whose difference-frequency band, effectively 1-6 kHz, is being used to observe Atlantic herring (Clupea harengus) in situ. Range compensation functions for this sonar are compared with corresponding functions for conventional sonars for the cases of single and multiple scatterers. Dependences of these range compensation functions on the parametric sonar transducer shape, size, acoustic power density, and hydrography are investigated. Parametric range compensation functions, when applied with calibration data, will enable difference-frequency echoes to be expressed in physical units of volume backscattering, and backscattering spectra, including fish-swimbladder-resonances, to be analyzed.

  9. Discriminant classification of different fish-species backscattering

    NASA Astrophysics Data System (ADS)

    Zhang, Qiao; Xu, Feng; Liu, Yin; Zhang, Chun

    2012-11-01

    The complex structure of fish and multispecies composition complicate the analysis of acoustic data. Consequently, it is difficult to obtain a highly accurate rate of classification by using current approaches. This paper introduces two discriminating methods: the adaptive segmentation temporal centroid method and the wavelet packet multi-scale information entropy method. To verify and compare these two methods, an ex situ experiment has been performed with three kinds of fish: Crucian carp (Carassius auratus), Yellow-headed catfish (Pelteobagrus fulvidraco) and Bluntnose black bream (Megalobrama amblycephale). The backscattering signals of these fishes are obtained. Then the temporal centroid in the divided sub-segmentation of the backscattering envelope is calculated, and the multi-scale information entropy of the wavelet packet decomposition in different frequency bands is extracted. Finally, three kinds of fish are successfully classified by using a BP neural network. The result shows that the adaptive segmentation temporal centroid method is 4% more accurate than the wavelet packet multi-scale information entropy method.

  10. Control of collective FSBS and backscatter SRS through plasma composition

    NASA Astrophysics Data System (ADS)

    Rose, Harvey; Lushnikov, Pavel

    2005-10-01

    Nominal NIF parameters are near the collective forward SBS (FSBS) threshold (P. M. Lushnikov and H. A. Rose, Phys. Rev. Lett. 92, 255003 (2004), ``L&R''). It will be shown that being on this instability edge can be used as a control lever: a small amount of high Z dopant may lead to qualitative change in FSBS regime at fixed laser intensity, possibly reducing backscatter instability losses (Such results have already been observed, but absent SSD, a key aspect of our theory: R. M. Stevenson et al., Phys. Plasmas 11, 2709 (2004); L. J. Suter et al., 2738, ib.). Ponderomotive FSBS regimes are determined by the parameter I=F^2( vosc / vosc ve . - ve )^2( ne / ne nc . - nc ) / ( ne / ne nc . - nc ) ν . - ν, with ν the dimensionless ion acoustic damping coefficient and F the optic f/#. Analytical results will be presented which show a decrease of I1pt's threshold value through the addition of high Z dopant to low Z plasma, owing to increased thermal contribution to FSBS. Alternatively, one may raise the threshold by managing the value of νby, e.g., adding He to SiO2. For nominal NIF parameters, a range of He fraction in SiO2 plasma is predicted to suppress backscatter SRS while maintaining control of forward SBS.

  11. [Backscattering spectrum analysis of nonspheroid soot particle].

    PubMed

    Xing, Jian; Sun, Xiao-gang; Yuan, Gui-bin; Qi, Xu; Tang, Hong

    2010-08-01

    In the process of measuring soot concentration and grain diameter, the backscattering spectrum of soot particle model was calculated to ascertain and analyze main effective factor of backscattering intensity. In the present paper, ellipsoid, column and generalized Chebyshev, three nonspheroid models, were selected according to micrograph of practical soot particle, which aims to simulate practical soot particle with equivalent diameter of about 1 microm. T-matrix method was used to calculate backscattering spectrum of the three nonspheriod models, and the main effective factor curves of intensity were obtained, too. Both numerical computer simulations and experimental results illustrate that nonspheroid particle backscattering intensity is stronger than that of spheroid particle in the visible/infrared spectrum band, especially for generalized Chebyshev model, whose backscattering intensity can be even 3.5 times higher than that of forward scattering. Meanwhile, the absorbency non-spheroid particle (complex refractive index m = 1.57 - 0.56i) backscattering intensity is stronger than that of non-absorbency nonspheriod particle (complex refractive index m = 1.57 - 0.001i). Furthermore, with the increase in particle equivalent radius, the light source wavelength also needs to be increase to obtain more light intensity information. The backscattering light spectrum information provides a reasonable basis for selecting light source and measure angle.

  12. Acoustic Neuroma

    MedlinePlus

    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 ...

  13. Using bathymetric derivatives to detect seabed features and assessment of backscatter variability of morphologically complex seabed

    NASA Astrophysics Data System (ADS)

    Alevizos, E.; Greinert, J.; Meysman, F. J.

    2013-12-01

    This study examines the application of bathymetry derivatives for seabed classification with respect in geomorphological seabed mapping of complex areas. Our dataset comprises of multibeam bathymetry and backscatter from a geomorphological complex site off the shore of Grevelingen (North Sea, Netherlands). The site comprises significant variability due to previous dredging activity and proximity to the shore whereas it includes a dump site for shells. By utilizing the Benthic Terrain Modeler add-in of ArcGIS we calculated first and second order bathymetric derivatives according to which we produced a morphological classification map of the area using the standardized process of the Greene & Bizzaro, Coded Classification Scheme. Bathymetric terrain analysis revealed the existence of low-relief large scale bedforms that could not be distinguished sufficiently in the bathymetry raster and the backscatter mosaic. This is of particular importance in bedform mapping and hydrodynamic modeling of such areas. Additionally backscatter data was mosaicked and classified by utilizing the Angular Response Analysis method. The ARA results include mean grain size, acoustic impedance and roughness predictions. We validated the results using several ground truth samples against predicted mean grain size values. Generally, some grade of discrepancy between actual and predicted grain size was identified. By having the grain size variation generally low over different parts of the area we suggest that acoustic impedance and seabed micro-roughness possibly control the backscatter intensity for the given area with the sonar frequency used. Therefore it is proposed that future ground truth data shall include measurements for sediment shear strength and fine-scale underwater stereo photography which will add valuable information in backscatter classification over morphologically complex seabed.

  14. Anisotropic physical properties of myocardium characterized by ultrasonic measurements of backscatter, attenuation, and velocity

    NASA Astrophysics Data System (ADS)

    Baldwin, Steven L.

    The goal of elucidating the physical mechanisms underlying the propagation of ultrasonic waves in anisotropic soft tissue such as myocardium has posed an interesting and largely unsolved problem in the field of physics for the past 30 years. In part because of the vast complexity of the system being studied, progress towards understanding and modeling the mechanisms that underlie observed acoustic parameters may first require the guidance of careful experiment. Knowledge of the causes of observed ultrasonic properties in soft tissue including attenuation, speed of sound, and backscatter, and how those properties are altered with specific pathophysiologies, may lead to new noninvasive approaches to the diagnosis of disease. The primary aim of this Dissertation is to contribute to an understanding of the physics that underlies the mechanisms responsible for the observed interaction of ultrasound with myocardium. To this end, through-transmission and backscatter measurements were performed by varying acoustic properties as a function of angle of insonification relative to the predominant myofiber direction and by altering the material properties of myocardium by increased protein cross-linking induced by chemical fixation as an extreme form of changes that may occur in certain pathologies such as diabetes. Techniques to estimate acoustic parameters from backscatter were broadened and challenges to implementing these techniques in vivo were addressed. Provided that specific challenges identified in this Dissertation can be overcome, techniques to estimate attenuation from ultrasonic backscatter show promise as a means to investigate the physical interaction of ultrasound with anisotropic biological media in vivo. This Dissertation represents a step towards understanding the physics of the interaction of ultrasonic waves with anisotropic biological media.

  15. Cyclone diagnostics. [rainfall estimation, backscatter, and lidar

    NASA Technical Reports Server (NTRS)

    1984-01-01

    A GOES IR rainfall estimation algorithm was completed and verified. The technique was applied to the South Pacific convergent zone. The NASA earth observation mission series is discussed briefly. Backscatter was investigated using 10.6 micron coherent lidar.

  16. C-band backscattering from corn canopies

    NASA Technical Reports Server (NTRS)

    Daughtry, C. S. T.; Ranson, K. J.; Biehl, L. L.

    1991-01-01

    A frequency-modulatad continuous-wave C-band (4.8 GHz) scatterometer was mounted on an aerial lift truck, and backscatter coefficients of corn (Zea mays L.) were acquired as functions of polarizations, view angles, and row directions. As phytomass and green-leaf area index increased, the backscatter also increased. Near anthesis, when the canopies were fully developed, the major scattering elements were located in the upper 1 m of the 2.8 m tall canopy and little backscatter was measured below that level for view angles of 30 deg or greater. C-band backscatter data could provide information to monitor tillage operations at small view zenith angles and vegetation at large view zenith angles.

  17. Coherent microwave backscatter of natural snowpacks

    NASA Technical Reports Server (NTRS)

    Linlor, W. I.; Angelakos, D. J.; Clapp, F. D.; Smith, J. L.

    1977-01-01

    The backscatter of natural snowpacks was measured using a swept-frequency system operating from 5.8 to 8.0 GHz. Snow layering produced sequences of maxima and minima in backscatter intensity, with typical peak-to-valley ratios of 15 db. Wetness produced in the upper portion of the snowpack by solar heat input enhanced the effect of layering. The layer response persisted for incidence exhibits predominantly coherent properties. Frequency modulation of the incident signal masked the layer response by averaging the unmodulated response over the bandwidth represented by the modulation. Further changes in backscatter were attributed to changes in wetness in the surface regions of the snowpack; for a fixed frequency of 13.5 GHz and incidence angle of 39 deg, the backscatter decreased typically 15 db between 11 A.M. and noon, and returned to approximately its initial level of overnight.

  18. Acoustic Seaglider

    DTIC Science & Technology

    2008-03-07

    a national naval responsibility. Acoustic sensors on mobile, autonomous platforms will enable basic research topics on temporal and spatial...problem and acoustic navigation and communications within the context of distributed autonomous persistent undersea surveillance sensor networks...Acoustic sensors on mobile, autonomous platforms will enable basic research topics on temporal and spatial coherence and the description of ambient

  19. Acoustic seal

    NASA Technical Reports Server (NTRS)

    Steinetz, Bruce M. (Inventor)

    2006-01-01

    The invention relates to a sealing device having an acoustic resonator. The acoustic resonator is adapted to create acoustic waveforms to generate a sealing pressure barrier blocking fluid flow from a high pressure area to a lower pressure area. The sealing device permits noncontacting sealing operation. The sealing device may include a resonant-macrosonic-synthesis (RMS) resonator.

  20. Acoustic Seal

    NASA Technical Reports Server (NTRS)

    Steinetz, Bruce M. (Inventor)

    2006-01-01

    The invention relates to a sealing device having an acoustic resonator. The acoustic resonator is adapted to create acoustic waveforms to generate a sealing pressure barrier blocking fluid flow from a high pressure area to a lower pressure area. The sealing device permits noncontacting sealing operation. The sealing device may include a resonant-macrosonic-synthesis (RMS) resonator.

  1. Lidar backscattering measurements of background stratospheric aerosols

    NASA Technical Reports Server (NTRS)

    Remsberg, E. E.; Northam, G. B.; Butler, C. F.

    1979-01-01

    A comparative lidar-dustsonde experiment was conducted in San Angelo, Texas, in May 1974 in order to estimate the uncertainties in stratospheric-aerosol backscatter for the NASA Langley 48-inch lidar system. The lidar calibration and data-analysis procedures are discussed. Results from the Texas experiment indicate random and systematic uncertainties of 35 and 63 percent, respectively, in backscatter from a background stratospheric-aerosol layer at 20 km.

  2. Multispectral Backscattering: A Fractal-Structure Probe

    DTIC Science & Technology

    2000-01-01

    discussed in more details below in Sec.D. 2.1 Orientation-Averaged T - Matrix Code In principle, for the case of rigid aggregate of homogeneous spheres, the...reliable approximation up to the largest values of x attainable by T - matrix code with our computers. 3 Backscattering Coefficient The backscattering...basic T - matrix code may be found at http://www.giss.nasa.gov crmim/, and original DDA code comes from http://www.astro.princeton.edu

  3. Backscatter correction factor for megavoltage photon beam

    SciTech Connect

    Hu, Yida; Zhu, Timothy C.

    2011-10-15

    Purpose: For routine clinical dosimetry of photon beams, it is often necessary to know the minimum thickness of backscatter phantom material to ensure that full backscatter condition exists. Methods: In case of insufficient backscatter thickness, one can determine the backscatter correction factor, BCF(s,d,t), defined as the ratio of absorbed dose measured on the central-axis of a phantom with backscatter thickness of t to that with full backscatter for square field size s and forward depth d. Measurements were performed in SAD geometry for 6 and 15 MV photon beams using a 0.125 cc thimble chamber for field sizes between 10 x 10 and 30 x 30 cm at depths between d{sub max} (1.5 cm for 6 MV and 3 cm for 15 MV) and 20 cm. Results: A convolution method was used to calculate BCF using Monte-Carlo simulated point-spread kernels generated for clinical photon beams for energies between Co-60 and 24 MV. The convolution calculation agrees with the experimental measurements to within 0.8% with the same physical trend. The value of BCF deviates more from 1 for lower energies and larger field sizes. According to our convolution calculation, the minimum BCF occurs at forward depth d{sub max} and 40 x 40 cm field size, 0.970 for 6 MV and 0.983 for 15 MV. Conclusions: The authors concluded that backscatter thickness is 6.0 cm for 6 MV and 4.0 cm for 15 MV for field size up to 10 x 10 cm when BCF = 0.998. If 4 cm backscatter thickness is used, BCF is 0.997 and 0.983 for field size of 10 x 10 and 40 x 40 cm for 6 MV, and is 0.998 and 0.990 for 10 x 10 and 40 x 40 cm for 15 MV, respectively.

  4. Observations of Enhanced Radar Backscatter (ERB) from Millstone Hill

    NASA Technical Reports Server (NTRS)

    Lee, M. C.

    1991-01-01

    Intense enhancements of the incoherent radar backscatter spectrum from the topside ionosphere were observed with the Millstone Hill UHF radar. Enhancements occurring at the local ion acoustic frequency causing large asymmetries in the measured ion line may be produced by current driven instabilities. These enhancements pose a practical problem for space surveillance systems because their cross section and spectral width are characteristic of satellites. Conversely, their hard target signature complicates the study of naturally occurring ERB events; it is nearly impossible to distinguish them from satellites based on a single measurement. Statistical comparisons of observed coherent echo distributions with predictions from a satellite catalog were used to broadly identify periods of ERB activity. A series of experiments using multiple diagnostics, including satellite instruments, for simultaneous observations have established the association of ERB with large fluxes of soft suprathermal electrons carrying field aligned currents. Zenith data are also presented which show the asymmetric growth of ion acoustic waves directly above Millstone Hill. Details of these results are presented.

  5. Cavitation inception by the backscattering of pressure waves from a bubble interface

    SciTech Connect

    Takahira, Hiroyuki Ogasawara, Toshiyuki Mori, Naoto Tanaka, Moe

    2015-10-28

    The secondary cavitation that occurs by the backscattering of focused ultrasound from a primary cavitation bubble caused by the negative pressure part of the ultrasound (Maxwell, et al., 2011) might be useful for the energy exchange due to bubble oscillations in High Intensity Focused Ultrasound (HIFU). The present study is concerned with the cavitation inception by the backscattering of ultrasound from a bubble. In the present experiment, a laser-induced bubble which is generated by a pulsed focused laser beam with high intensity is utilized as a primary cavitation bubble. After generating the bubble, focused ultrasound is emitted to the bubble. The acoustic field and the bubble motion are observed with a high-speed video camera. It is confirmed that the secondary cavitation bubble clouds are generated by the backscattering from the laser-induced bubble. The growth of cavitation bubble clouds is analyzed with the image processing method. The experimental results show that the height and width of the bubble clouds grow in stepwise during their evolution. The direct numerical simulations are also conducted for the backscattering of incident pressure waves from a bubble in order to evaluate a pressure field near the bubble. It is shown that the ratio of a bubble collapse time t{sub 0} to a characteristic time of wave propagation t{sub S}, η = t{sub 0}/t{sub s}, is an important determinant for generating negative pressure region by backscattering. The minimum pressure location by the backscattering in simulations is in good agreement with the experiment.

  6. SNR characterization in distributed acoustic sensing

    NASA Astrophysics Data System (ADS)

    Gabai, Haniel; Eyal, Avishay

    2016-05-01

    In this paper we study the SNR associated with acoustic detection in Rayleigh-based Distributed Acoustic Sensing (DAS) systems. The study is focused on phase sensitive DAS due to its superiority in terms of linearity and sensitivity. Since DAS is based on coherent interference of backscattered light from multiple scatterers it is prone to signal fading. When left unresolved, the issue of signal fading renders the associated SNR randomly dependent on position and time. Hence, its proper measurement and characterization requires statistical tools. Here such tools are introduced and a methodology for finding the mean SNR and its distribution is implemented in both experiment and simulation. It is shown that the distribution of the DAS-SNR can be obtained from the distribution of backscattered power in OTDR and the mean DAS-SNR is proportional to the energy of the interrogation pulse.

  7. Hulu Sungai Perak Bed Sediment Mapping Using Underwater Acoustic Sonar

    NASA Astrophysics Data System (ADS)

    Arriafdi, N.; Zainon, O.; Din, U.; Rasid, A. W.; Mat Amin, Z.; Othman, R.; Mardi, A. S.; Mahmud, R.; Sulaiman, N.

    2016-09-01

    Development in acoustic survey techniques in particular side scan sonar have revolutionized the way we are able to image, map and understand the riverbed environment. It is now cost effective to image large areas of the riverbed using these techniques and the backscatter image created from surveys provides base line data from which thematic maps of the riverbed environment including maps of morphological geology, can be derived when interpreted in conjunction with in situ sampling data. This article focuses on investigation characteristics of sediments and correlation of side scan backscatter image with signal strength. The interpretation of acoustic backscatter rely on experienced interpretation by eye of grey scale images produced from the data. A 990F Starfish Side Scan Sonar was used to collect and develop a series of sonar images along 6 km of Hulu Sungai Perak. Background sediments could be delineated accurately and the image textures could be linked to the actual river floor appearance through grab sampling. A major difference was found in the acoustic returns from the two research area studies: the upstream area shows much rougher textures. This is due to an actual differences in riverbed roughness, caused by a difference in bottom currents and sediment dynamics in the two areas. The highest backscatter correlates with coarsest and roughness sediment. Result suggest that image based backscatter classification shows considerable promise for interpretation of side scan sonar data for the production of geological maps.

  8. GLObal Backscatter Experiment (GLOBE) Pacific survey mission

    NASA Technical Reports Server (NTRS)

    Bowdle, David A.; Rothermel, Jeffry; Arnold, James E.; Williams, Steven F.

    1991-01-01

    NASA conducted the GLObal Backscatter Experiment (GLOBE) Survey Mission over the near coastal and remote Pacific Ocean during 6 to 30 Nov. 1989 (GLOBE 1) and 13 May to 5 Jun. 1990 (GLOBE 2). These missions studied the optical, physical, and chemical properties of atmospheric aerosols. Particular emphasis was given to the magnitude and spatial variability of aerosol backscatter coefficients at mid-infrared wavelengths, and to the remote middle and upper troposphere, where these aerosol properties are poorly understood. Survey instruments were selected to provide either direct beta measurements at the key wavelengths, empirical links with long term or global scale aerosol climatologies, or aerosol microphysics data required to model any of these quantities. The survey deployment included both long distance 6 to 8 hour transit flights and detailed 4 to 6 hour local flights. Several general features were observed from preliminary Survey data analyses. Validation and intercomparison results have shown good agreement, usually better than a factor of two. Atmospheric aerosols frequently exhibited a three layer vertical structure, with (1) high and fairly uniform backscatter in the shallow cloud capped marine boundary layer; (2) moderate and highly variable backscatter in a deeper overlaying cloud pumped layer; and (3) low, regionally uniform, but seasonally and latitudinally variable backscatter in the middle and upper troposphere. The survey missions represent two isolated snapshots of a small portion of the global aerosol system. Consequently, Survey results can best be understood by synthesizing them with the more comprehensive GLOBE data base, which is being compiled at NASA-Marshall.

  9. Reducing parametric backscattering by polarization rotation

    SciTech Connect

    Barth, Ido; Fisch, Nathaniel J.

    2016-10-01

    When a laser passes through underdense plasmas, Raman and Brillouin Backscattering can reflect a substantial portion of the incident laser energy. This is a major loss mechanism, for example, in employing lasers in inertial confinement fusion. But, by slow rotation of the incident linear polarization, the overall reflectivity can be reduced significantly. Particle in cell simulations show that, for parameters similar to those of indirect drive fusion experiments, polarization rotation reduces the reflectivity by a factor of 5. A general, fluid-model based analytical estimation for the reflectivity reduction agrees with simulations. However, in identifying the source of the backscatter reduction, it is difficult to disentangle the rotating polarization from the frequency separation based approach used to engineer the beam's polarization. Though the backscatter reduction arises similarly to other approaches that employ frequency separation, in the case here, the intensity remains constant in time.

  10. Reducing parametric backscattering by polarization rotation

    DOE PAGES

    Barth, Ido; Fisch, Nathaniel J.

    2016-10-01

    When a laser passes through underdense plasmas, Raman and Brillouin Backscattering can reflect a substantial portion of the incident laser energy. This is a major loss mechanism, for example, in employing lasers in inertial confinement fusion. But, by slow rotation of the incident linear polarization, the overall reflectivity can be reduced significantly. Particle in cell simulations show that, for parameters similar to those of indirect drive fusion experiments, polarization rotation reduces the reflectivity by a factor of 5. A general, fluid-model based analytical estimation for the reflectivity reduction agrees with simulations. However, in identifying the source of the backscatter reduction,more » it is difficult to disentangle the rotating polarization from the frequency separation based approach used to engineer the beam's polarization. Though the backscatter reduction arises similarly to other approaches that employ frequency separation, in the case here, the intensity remains constant in time.« less

  11. Reducing parametric backscattering by polarization rotation

    NASA Astrophysics Data System (ADS)

    Barth, Ido; Fisch, Nathaniel J.

    2016-10-01

    When a laser passes through underdense plasmas, Raman and Brillouin Backscattering can reflect a substantial portion of the incident laser energy. This is a major loss mechanism, for example, in employing lasers in inertial confinement fusion. However, by slow rotation of the incident linear polarization, the overall reflectivity can be reduced significantly. Particle in cell simulations show that, for parameters similar to those of indirect drive fusion experiments, polarization rotation reduces the reflectivity by a factor of 5. A general, fluid-model based analytical estimation for the reflectivity reduction agrees with simulations. However, in identifying the source of the backscatter reduction, it is difficult to disentangle the rotating polarization from the frequency separation based approach used to engineer the beam's polarization. Although the backscatter reduction arises similarly to other approaches that employ frequency separation, in the case here, the intensity remains constant in time.

  12. The use of multibeam backscatter intensity data as a tool for mapping glacial deposits in the Central North Sea, UK

    NASA Astrophysics Data System (ADS)

    Stewart, Heather; Bradwell, Tom

    2014-05-01

    Multibeam backscatter intensity data acquired offshore eastern Scotland and north-eastern England have been used to map drumlin fields, large arcuate moraine ridges, smaller scale moraine ridges, and incised channels on the sea floor. The study area includes the catchments of the previously proposed, but only partly mapped, Strathmore, Forth-Tay, and Tweed palaeo-ice streams. The ice sheet glacial landsystem is extremely well preserved on the sea bed and comprehensive mapping of the seafloor geomorphology has been undertaken. The authors demonstrate the value in utilising not only digital terrain models (both NEXTMap and multibeam bathymetry derived) in undertaking geomorphological mapping, but also examining the backscatter intensity data that is often overlooked. Backscatter intensity maps were generated using FM Geocoder by the British Geological Survey. FM Geocoder corrects the backscatter intensities registered by the multibeam echosounder system, and then geometrically corrects and positions each acoustic sample in a backscatter mosaic. The backscatter intensity data were gridded at the best resolution per dataset (between 2 and 5 m). The strength of the backscattering is dependent upon sediment type, grain size, survey conditions, sea-bed roughness, compaction and slope. A combination of manual interpretation and semi-automated classification of the backscatter intensity data (a predictive method for mapping variations in surficial sea-bed sediments) has been undertaken in the study area. The combination of the two methodologies has produced a robust glacial geomorphological map for the study area. Four separate drumlin fields have been mapped in the study area indicative of fast-flowing and persistent ice-sheet flow configurations. A number of individual drumlins are also identified located outside the fields. The drumlins show as areas of high backscatter intensity compared to the surrounding sea bed, indicating the drumlins comprise mixed sediments of

  13. Noninvasive measurement of local thermal diffusivity using backscattered ultrasound and focused ultrasound heating.

    PubMed

    Anand, Ajay; Kaczkowski, Peter J

    2008-09-01

    Previously, noninvasive methods of estimating local tissue thermal and acoustic properties using backscattered ultrasound have been proposed in the literature. In this article, a noninvasive method of estimating local thermal diffusivity in situ during focused ultrasound heating using beamformed acoustic backscatter data and applying novel signal processing techniques is developed. A high intensity focused ultrasound (HIFU) transducer operating at subablative intensities is employed to create a brief local temperature rise of no more than 10 degrees C. Beamformed radio-frequency (RF) data are collected during heating and cooling using a clinical ultrasound scanner. Measurements of the time-varying "acoustic strain", that is, spatiotemporal variations in the RF echo shifts induced by the temperature related sound speed changes, are related to a solution of the heat transfer equation to estimate the thermal diffusivity in the heated zone. Numerical simulations and experiments performed in vitro in tissue mimicking phantoms and excised turkey breast muscle tissue demonstrate agreement between the ultrasound derived thermal diffusivity estimates and independent estimates made by a traditional hot-wire technique. The new noninvasive ultrasonic method has potential applications in thermal therapy planning and monitoring, physiological monitoring and as a means of noninvasive tissue characterization.

  14. Eigenfunction analysis of stochastic backscatter for aberration correction in medical ultrasound imaging

    NASA Astrophysics Data System (ADS)

    Varslot, Trond; Mo, Eirik; Krogstad, Harald; Angelsen, Bjørn

    2004-05-01

    A filter for aberration correction in medical ultrasound imaging is presented. The filter is optimal in the sense of maximizing the expected energy in a modified beamformer output of the received acoustic backscatter. The situation considered is frequently found in applications when imaging organs through a body wall: aberration is introduced in a layer close to the transducer, and acoustic backscatter from a scattering region behind the body wall is measured at the transducer surface. The scattering region consists of scatterers randomly distributed with very short correlation length compared to the acoustic wave length of the transmit pulse. The scatterer distribution is therefore assumed to be δ-correlated. Theoretical considerations imply that maximizing the expected energy in a modified beamformer output signal naturally leads to eigenfunctions of a Fredholm integral operator, where the associated kernel function is a spatial correlation function of the received stochastic signal. Aberration characterization and aberration correction have been studied for simulated data constructed to mimic aberration introduced by the abdominal wall. The results compare well with what is obtained using a diffraction limited time-reversal filter based on simulated point source data.

  15. SAR backscatter from coniferous forest gaps

    NASA Technical Reports Server (NTRS)

    Day, John L.; Davis, Frank W.

    1992-01-01

    A study is in progress comparing Airborne Synthetic Aperture Radar (AIRSAR) backscatter from coniferous forest plots containing gaps to backscatter from adjacent gap-free plots. Issues discussed are how do gaps in the range of 400 to 1600 sq m (approximately 4-14 pixels at intermediate incidence angles) affect forest backscatter statistics and what incidence angles, wavelengths, and polarizations are most sensitive to forest gaps. In order to visualize the slant-range imaging of forest and gaps, a simple conceptual model is used. This strictly qualitative model has led us to hypothesize that forest radar returns at short wavelengths (eg., C-band) and large incidence angles (e.g., 50 deg) should be most affected by the presence of gaps, whereas returns at long wavelengths and small angles should be least affected. Preliminary analysis of 1989 AIRSAR data from forest near Mt. Shasta supports the hypothesis. Current forest backscatter models such as MIMICS and Santa Barbara Discontinuous Canopy Backscatter Model have in several cases correctly predicted backscatter from forest stands based on inputs of measured or estimated forest parameters. These models do not, however, predict within-stand SAR scene texture, or 'intrinsic scene variability' as Ulaby et al. has referred to it. For instance, the Santa Barbara model, which may be the most spatially coupled of the existing models, is not truly spatial. Tree locations within a simulated pixel are distributed according to a Poisson process, as they are in many natural forests, but tree size is unrelated to location, which is not the case in nature. Furthermore, since pixels of a simulated stand are generated independently in the Santa Barbara model, spatial processes larger than one pixel are not modeled. Using a different approach, Oliver modeled scene texture based on an hypothetical forest geometry. His simulated scenes do not agree well with SAR data, perhaps due to the simple geometric model used. Insofar as texture

  16. Multibeam Sonar Backscatter Data Acquisition and Processing: Guidelines and Recommendations from the GEOHAB Backscatter Working Group

    NASA Astrophysics Data System (ADS)

    Heffron, E.; Lurton, X.; Lamarche, G.; Brown, C.; Lucieer, V.; Rice, G.; Schimel, A.; Weber, T.

    2015-12-01

    Backscatter data acquired with multibeam sonars are now commonly used for the remote geological interpretation of the seabed. The systems hardware, software, and processing methods and tools have grown in numbers and improved over the years, yet many issues linger: there are no standard procedures for acquisition, poor or absent calibration, limited understanding and documentation of processing methods, etc. A workshop organized at the GeoHab (a community of geoscientists and biologists around the topic of marine habitat mapping) annual meeting in 2013 was dedicated to seafloor backscatter data from multibeam sonars and concluded that there was an overwhelming need for better coherence and agreement on the topics of acquisition, processing and interpretation of data. The GeoHab Backscatter Working Group (BSWG) was subsequently created with the purpose of documenting and synthetizing the state-of-the-art in sensors and techniques available today and proposing methods for best practice in the acquisition and processing of backscatter data. Two years later, the resulting document "Backscatter measurements by seafloor-mapping sonars: Guidelines and Recommendations" was completed1. The document provides: An introduction to backscatter measurements by seafloor-mapping sonars; A background on the physical principles of sonar backscatter; A discussion on users' needs from a wide spectrum of community end-users; A review on backscatter measurement; An analysis of best practices in data acquisition; A review of data processing principles with details on present software implementation; and finally A synthesis and key recommendations. This presentation reviews the BSWG mandate, structure, and development of this document. It details the various chapter contents, its recommendations to sonar manufacturers, operators, data processing software developers and end-users and its implication for the marine geology community. 1: Downloadable at https://www.niwa.co.nz/coasts-and-oceans/research-projects/backscatter-measurement-guidelines

  17. Musical Acoustics

    NASA Astrophysics Data System (ADS)

    Gough, Colin

    This chapter provides an introduction to the physical and psycho-acoustic principles underlying the production and perception of the sounds of musical instruments. The first section introduces generic aspects of musical acoustics and the perception of musical sounds, followed by separate sections on string, wind and percussion instruments.

  18. Laser-speckle-visibility acoustic spectroscopy in soft turbid media

    NASA Astrophysics Data System (ADS)

    Wintzenrieth, Frédéric; Cohen-Addad, Sylvie; Le Merrer, Marie; Höhler, Reinhard

    2014-01-01

    We image the evolution in space and time of an acoustic wave propagating along the surface of turbid soft matter by shining coherent light on the sample. The wave locally modulates the speckle interference pattern of the backscattered light, which is recorded using a camera. We show both experimentally and theoretically how the temporal and spatial correlations in this pattern can be analyzed to obtain the acoustic wavelength and attenuation length. The technique is validated using shear waves propagating in aqueous foam. It may be applied to other kinds of acoustic waves in different forms of turbid soft matter such as biological tissues, pastes, or concentrated emulsions.

  19. Snowcover influence on backscattering from terrain

    NASA Technical Reports Server (NTRS)

    Ulaby, F. T.; Abdelrazik, M.; Stiles, W. H.

    1984-01-01

    The effects of snowcover on the microwave backscattering from terrain in the 8-35 GHz region are examined through the analysis of experimental data and by application of a semiempirical model. The model accounts for surface backscattering contributions by the snow-air and snow-soil interfaces, and for volume backscattering contributions by the snow layer. Through comparisons of backscattering data for different terrain surfaces measured both with and without snowcover, the masking effects of snow are evaluated as a function of snow water equivalent and liquid water content. The results indicate that with dry snowcover it is not possible to discriminate between different types of ground surface (concrete, asphalt, grass, and bare ground) if the snow water equivalent is greater than about 20 cm (or a depth greater than 60 cm for a snow density of 0.3 g/cu cm). For the same density, however, if the snow is wet, a depth of 10 cm is sufficient to mask the underlying surface.

  20. Window flaw detection by backscatter lighting

    NASA Technical Reports Server (NTRS)

    Crockett, L. K.; Minton, F. R.

    1978-01-01

    Portable fiber-optic probe detects tiny flaws in transparent materials. Probe transmits light through surface to illuminate interior of material by backscattering off its edges. Light-sensitive contact paper records scratch pattern. Technique can be used for rapid visual checks. Flexible fiber optics are safely used in explosive or flammable areas; they present no hazard of breakage or contamination in controlled environments.

  1. Visualization of x-ray backscatter data

    SciTech Connect

    Greenawald, E.C.; Ham, Y.S.; Poranski, C.F. Jr.

    1993-12-31

    Of the several processes which occur when x-rays interact with matter, Compton scattering is dominant in the range of energies commonly used in industrial radiography. The Compton interaction between an x-ray photon and a free or outer shell electron causes the electron to recoil and the photon to be propagated in a new direction with a reduced energy. Regardless of the incident beam energy, some photons are always scattered in the backwards direction. The potential for determining material properties by the detection of x-ray backscatter has been recognized for years. Although work in this area has been eclipsed by the rapid development of computerized tomography (CT), a variety of industrial backscatter imaging techniques and applications have been demonstrated. Backscatter inspection is unique among x-ray methods in its applicability with access to only one side of the object. The authors are currently developing the application of x-ray backscatter tomography (XBT) to the inspection of steel-reinforced rubber sonar domes on US Navy vessels. In this paper, the authors discuss the visualization methods they use to interpret the XBT data. They present images which illustrate the capability of XBT as applied to sonar domes and a variety of other materials and objects. They also demonstrate and discuss the use of several data visualization software products.

  2. Laser Forward and Backscattering in Particulate Media,

    DTIC Science & Technology

    1985-03-01

    puissance jdoit Itre beaucoup plus petite qua l’unitG. Tor T ~ ~ ITI GRa vTT TPS’~ UNCLASSIFIED TABLE OF CONTENTS LIST OF SYMBOLS...ktnown effects of the mltiple-scattering phenomenon, in parti- cular its greater influence on the backscatter than on the transmission measurements

  3. Incidence angle normalization of radar backscatter data

    Technology Transfer Automated Retrieval System (TEKTRAN)

    NASA’s Soil Moisture Passive Active (SMAP) satellite (~2014) will include a radar system that will provide L-band multi-polarization backscatter at a constant incidence angle of 40º. During the pre-launch phase of the project there is a need for observations that will support the radar-based soil mo...

  4. Laissez-Faire : Fully Asymmetric Backscatter Communication

    PubMed Central

    Hu, Pan; Zhang, Pengyu; Ganesan, Deepak

    2016-01-01

    Backscatter provides dual-benefits of energy harvesting and low-power communication, making it attractive to a broad class of wireless sensors. But the design of a protocol that enables extremely power-efficient radios for harvesting-based sensors as well as high-rate data transfer for data-rich sensors presents a conundrum. In this paper, we present a new fully asymmetric backscatter communication protocol where nodes blindly transmit data as and when they sense. This model enables fully flexible node designs, from extraordinarily power-efficient backscatter radios that consume barely a few micro-watts to high-throughput radios that can stream at hundreds of Kbps while consuming a paltry tens of micro-watts. The challenge, however, lies in decoding concurrent streams at the reader, which we achieve using a novel combination of time-domain separation of interleaved signal edges, and phase-domain separation of colliding transmissions. We provide an implementation of our protocol, LF-Backscatter, and show that it can achieve an order of magnitude or more improvement in throughput, latency and power over state-of-art alternatives. PMID:28286885

  5. Ultrasonic backscatter coefficients for weakly scattering, agar spheres in agar phantoms

    PubMed Central

    King, Michael R.; Anderson, Janelle J.; Herd, Maria-Teresa; Ma, Darryl; Haak, Alexander; Wirtzfeld, Lauren A.; Madsen, Ernest L.; Zagzebski, James A.; Oelze, Michael L.; Hall, Timothy J.; O’Brien, William D.

    2010-01-01

    Applicability of ultrasound phantoms to biological tissue has been limited because most phantoms have generally used strong scatterers. The objective was to develop very weakly scattering phantoms, whose acoustic scattering properties are likely closer to those of tissues and then compare theoretical simulations and experimental backscatter coefficient (BSC) results. The phantoms consisted of agar spheres of various diameters (nominally between 90 and 212 μm), containing ultrafiltered milk, suspended in an agar background. BSC estimates were performed at two institutions over the frequency range 1–13 MHz, and compared to three models. Excellent agreement was shown between the two laboratory results as well as with the three models. PMID:20707460

  6. Ab-initio Studies Of Lithium Oxide

    NASA Astrophysics Data System (ADS)

    Gupta, M. K.; Goel, Prabhatasree; Mittal, R.; Chaplot, S. L.

    2010-12-01

    Lithium oxide is an important material because of its high thermal conductivity and superionic behavior at high temperature. It behaves like a superionic conductor above 1200 K. Phonon frequencies have been calculated using ab-initio method. The calculations of phonon dispersion relation near unit cell volume corresponding to the superionic transition indicate softening of zone boundary transverse acoustic phonon mode along (110). The instability of phonon mode could lead to the dynamical disorder of lithium sub lattice. Thermal expansion and equation of states are also computed. The results compare well with our previous semi-empirical potential calculations.

  7. Synthetic aperture acoustic imaging of non-metallic cords

    NASA Astrophysics Data System (ADS)

    Glean, Aldo A. J.; Good, Chelsea E.; Vignola, Joseph F.; Judge, John A.; Ryan, Teresa J.; Bishop, Steven S.; Gugino, Peter M.; Soumekh, Mehrdad

    2012-06-01

    This work presents a set of measurements collected with a research prototype synthetic aperture acoustic (SAA) imaging system. SAA imaging is an emerging technique that can serve as an inexpensive alternative or logical complement to synthetic aperture radar (SAR). The SAA imaging system uses an acoustic transceiver (speaker and microphone) to project acoustic radiation and record backscatter from a scene. The backscattered acoustic energy is used to generate information about the location, morphology, and mechanical properties of various objects. SAA detection has a potential advantage when compared to SAR in that non-metallic objects are not readily detectable with SAR. To demonstrate basic capability of the approach with non-metallic objects, targets are placed in a simple, featureless scene. Nylon cords of five diameters, ranging from 2 to 15 mm, and a joined pair of 3 mm fiber optic cables are placed in various configurations on flat asphalt that is free of clutter. The measurements were made using a chirp with a bandwidth of 2-15 kHz. The recorded signal is reconstructed to form a two-dimensional image of the distribution of acoustic scatterers within the scene. The goal of this study was to identify basic detectability characteristics for a range of sizes and configurations of non-metallic cord. It is shown that for sufficiently small angles relative to the transceiver path, the SAA approach creates adequate backscatter for detectability.

  8. Study on demodulated signal distribution and acoustic pressure phase sensitivity of a self-interfered distributed acoustic sensing system

    NASA Astrophysics Data System (ADS)

    Shang, Ying; Yang, Yuan-Hong; Wang, Chen; Liu, Xiao-Hui; Wang, Chang; Peng, Gang-Ding

    2016-06-01

    We propose a demodulated signal distribution theory for a self-interfered distributed acoustic sensing system. The distribution region of Rayleigh backscattering including the acoustic sensing signal in the sensing fiber is investigated theoretically under different combinations of both the path difference and pulse width Additionally we determine the optimal solution between the path difference and pulse width to obtain the maximum phase change per unit length. We experimentally test this theory and realize a good acoustic pressure phase sensitivity of  -150 dB re rad/(μPa·m) of fiber in the frequency range from 200 Hz to 1 kHz.

  9. Application of Acoustic and Optic Methods for Estimating Suspended-Solids Concentrations in the St. Lucie River Estuary, Florida

    USGS Publications Warehouse

    Patino, Eduardo; Byrne, Michael J.

    2004-01-01

    Acoustic and optic methods were applied to estimate suspended-solids concentrations in the St. Lucie River Estuary, southeastern Florida. Acoustic Doppler velocity meters were installed at the North Fork, Speedy Point, and Steele Point sites within the estuary. These sites provide varying flow, salinity, water-quality, and channel cross-sectional characteristics. The monitoring site at Steele Point was not used in the analyses because repeated instrument relocations (due to bridge construction) prevented a sufficient number of samples from being collected at the various locations. Acoustic and optic instruments were installed to collect water velocity, acoustic backscatter strength (ABS), and turbidity data that were used to assess the feasibility of estimating suspended-solids concentrations in the estuary. Other data collected at the monitoring sites include tidal stage, salinity, temperature, and periodic discharge measurements. Regression analyses were used to determine the relations of suspended-solids concentration to ABS and suspended-solids concentration to turbidity at the North Fork and Speedy Point sites. For samples used in regression analyses, measured suspended-solids concentrations at the North Fork and Speedy Point sites ranged from 3 to 37 milligrams per liter, and organic content ranged from 50 to 83 percent. Corresponding salinity for these samples ranged from 0.12 to 22.7 parts per thousand, and corresponding temperature ranged from 19.4 to 31.8 ?C. Relations determined using this technique are site specific and only describe suspended-solids concentrations at locations where data were collected. The suspended-solids concentration to ABS relation resulted in correlation coefficients of 0.78 and 0.63 at the North Fork and Speedy Point sites, respectively. The suspended-solids concentration to turbidity relation resulted in correlation coefficients of 0.73 and 0.89 at the North Fork and Speedy Point sites, respectively. The adequacy of the

  10. The Minnaert Bubble: An Acoustic Approach

    ERIC Educational Resources Information Center

    Devaud, Martin; Hocquet, Thierry; Bacri, Jean-Claude; Leroy, Valentin

    2008-01-01

    We propose an "ab initio" introduction to the well-known Minnaert pulsating bubble at graduate level. After a brief recall of the standard stuff, we begin with a detailed discussion of the radial movements of an air bubble in water. This discussion is managed from an acoustic point of view, and using the Lagrangian rather than the Eulerian…

  11. Electromagnetic backscattering from one-dimensional drifting fractal sea surface II: Electromagnetic backscattering model

    NASA Astrophysics Data System (ADS)

    Tao, Xie; William, Perrie; Shang-Zhuo, Zhao; He, Fang; Wen-Jin, Yu; Yi-Jun, He

    2016-07-01

    Sea surface current has a significant influence on electromagnetic (EM) backscattering signals and may constitute a dominant synthetic aperture radar (SAR) imaging mechanism. An effective EM backscattering model for a one-dimensional drifting fractal sea surface is presented in this paper. This model is used to simulate EM backscattering signals from the drifting sea surface. Numerical results show that ocean currents have a significant influence on EM backscattering signals from the sea surface. The normalized radar cross section (NRCS) discrepancies between the model for a coupled wave-current fractal sea surface and the model for an uncoupled fractal sea surface increase with the increase of incidence angle, as well as with increasing ocean currents. Ocean currents that are parallel to the direction of the wave can weaken the EM backscattering signal intensity, while the EM backscattering signal is intensified by ocean currents propagating oppositely to the wave direction. The model presented in this paper can be used to study the SAR imaging mechanism for a drifting sea surface. Project supported by the National Natural Science Foundation of China (Grant No. 41276187), the Global Change Research Program of China (Grant No. 2015CB953901), the Priority Academic Program Development of Jiangsu Higher Education Institutions, China, the Program for the Innovation Research and Entrepreneurship Team in Jiangsu Province, China, the Canadian Program on Energy Research and Development, and the Canadian World Class Tanker Safety Service Program.

  12. Control of coherent backscattering by breaking optical reciprocity

    NASA Astrophysics Data System (ADS)

    Bromberg, Y.; Redding, B.; Popoff, S. M.; Cao, H.

    2016-02-01

    Reciprocity is a universal principle that has a profound impact on many areas of physics. A fundamental phenomenon in condensed-matter physics, optical physics, and acoustics, arising from reciprocity, is the constructive interference of quantum or classical waves which propagate along time-reversed paths in disordered media, leading to, for example, weak localization and metal-insulator transition. Previous studies have shown that such coherent effects are suppressed when reciprocity is broken. Here we experimentally show that by tuning a nonreciprocal phase we can coherently control complex coherent phenomena, rather than simply suppress them. In particular, we manipulate coherent backscattering of light, also known as weak localization. By utilizing a magneto-optical effect, we control the interference between time-reversed paths inside a multimode fiber with strong mode mixing, observe the optical analog of weak antilocalization, and realize a continuous transition from weak localization to weak antilocalization. Our results may open new possibilities for coherent control of waves in complex systems.

  13. Room Acoustics

    NASA Astrophysics Data System (ADS)

    Kuttruff, Heinrich; Mommertz, Eckard

    The traditional task of room acoustics is to create or formulate conditions which ensure the best possible propagation of sound in a room from a sound source to a listener. Thus, objects of room acoustics are in particular assembly halls of all kinds, such as auditoria and lecture halls, conference rooms, theaters, concert halls or churches. Already at this point, it has to be pointed out that these conditions essentially depend on the question if speech or music should be transmitted; in the first case, the criterion for transmission quality is good speech intelligibility, in the other case, however, the success of room-acoustical efforts depends on other factors that cannot be quantified that easily, not least it also depends on the hearing habits of the listeners. In any case, absolutely "good acoustics" of a room do not exist.

  14. Evaluation of ADCP backscatter inversion to suspended sediment concentration in estuarine environments

    NASA Astrophysics Data System (ADS)

    Park, Hyo-Bong; Lee, Guan-hong

    2016-03-01

    Acoustic Doppler Current Profilers (ADCP), designed for measuring velocity profiles, are widely used for the estimation of suspended sediment concentration from acoustic backscatter strength, but its application to estuarine environments requires further refinement. In this study, we examined the inversion capability of two ADCPs with 600 and 1200 kHz in three Korean estuaries: the supra-macrotidal Han River Estuary (HRE), microtidal Nakdong River Estuary (NRE), and anthropogenically altered macrotidal Yeongsan River Estuary (YRE). In particular, we examined the relative importance of the sound attenuations due to water (αw) and sediment (αs) in response to sediment characteristics (size and concentration) as well as changing salinity and temperature. The inverted concentration was compared with reference concentrations obtained either from water samples or Optical Backscatter Sensors. In NRE and YRE, where suspended sediment concentrations were less than 0.2 g/l, the acoustic inversion performed poorly only with αs (r = 0.20 and 0.38 for NRE and YRE, respectively), but well with αw (r = 0.66 and 0.42 for NRE and YRE, respectively). Thus, it is important to accurately constrain αw in low-concentration estuarine environments. However, we did not find that the varying αw performed considerably better than the constant αw. On the other hand, the acoustic inversion was poorest at HRE regardless of αw and αs (r = 0.71 and mean relative error = 45%). The large discrepancy appears to result from the poorly constrained, spatially and temporally varying sediment characteristics (grain size, density and concentration) due to non-local sediment transport in the macrotidal HRE.

  15. Spectra of Particulate Backscattering in Natural Waters

    NASA Technical Reports Server (NTRS)

    Gordon, Howard, R.; Lewis, Marlon R.; McLean, Scott D.; Twardowski, Michael S.; Freeman, Scott A.; Voss, Kenneth J.; Boynton, Chris G.

    2009-01-01

    Hyperspectral profiles of downwelling irradiance and upwelling radiance in natural waters (oligotrophic and mesotrophic) are combined with inverse radiative transfer to obtain high resolution spectra of the absorption coefficient (a) and the backscattering coefficient (bb) of the water and its constituents. The absorption coefficient at the mesotrophic station clearly shows spectral absorption features attributable to several phytoplankton pigments (Chlorophyll a, b, c, and Carotenoids). The backscattering shows only weak spectral features and can be well represented by a power-law variation with wavelength (lambda): b(sub b) approx. Lambda(sup -n), where n is a constant between 0.4 and 1.0. However, the weak spectral features in b(sub b), suggest that it is depressed in spectral regions of strong particle absorption. The applicability of the present inverse radiative transfer algorithm, which omits the influence of Raman scattering, is limited to lambda < 490 nm in oligotrophic waters and lambda < 575 nm in mesotrophic waters.

  16. Aerosol backscatter lidar calibration and data interpretation

    NASA Technical Reports Server (NTRS)

    Kavaya, M. J.; Menzies, R. T.

    1984-01-01

    A treatment of the various factors involved in lidar data acquisition and analysis is presented. This treatment highlights sources of fundamental, systematic, modeling, and calibration errors that may affect the accurate interpretation and calibration of lidar aerosol backscatter data. The discussion primarily pertains to ground based, pulsed CO2 lidars that probe the troposphere and are calibrated using large, hard calibration targets. However, a large part of the analysis is relevant to other types of lidar systems such as lidars operating at other wavelengths; continuous wave (CW) lidars; lidars operating in other regions of the atmosphere; lidars measuring nonaerosol elastic or inelastic backscatter; airborne or Earth-orbiting lidar platforms; and lidars employing combinations of the above characteristics.

  17. Microwave backscattering from an anisotropic soybean canopy

    NASA Technical Reports Server (NTRS)

    Lang, R. H.; Saatchi, S.; Levine, D. M.

    1986-01-01

    Electromagnetic backscattering from a soybean canopy is modeled in the L band region of the spectrum. Mature soybean plants are taken as an ensemble of leaves and stems which are represented by lossy dielectric disks and rods respectively. Field data indicated that leaves and stems are not distributed uniformly in the azimuth coordinate. The plant has a tendency to grow out into the area between the rows. The effects on backscattered radar waves was computed by the distorted Born approximation. Results for look directions along the rows and perpendicular to the rows show that only a modest difference occurs in the L band frequency range. The use of another nonuniform distribution, different from those observed experimentally, results in a significant effect due to vegetation asymmetry.

  18. Backscattering power spectrum for randomly moving vegetation

    NASA Astrophysics Data System (ADS)

    Jiankang, J.; Zhongzhi, Z.; Zhong, S.

    1986-08-01

    The vegetation backscattering power spectrum in the presence of winds is derived. The physical process of the action of stems and leaves of the vegetation is analyzed. A statistical distribution of the random velocity of stems and leaves is obtained, and the vegetation backscattering power spectral density which is dependent on the wind speed and direction as well as the incident wave parameters is given. In the case of uniform notion of vegetation in the direction of winds, the results provide a good interpretation of Fishbein's empirical model. The determination of the values of the equivalent parameters in the spectrum is discussed, and comparisons are made between the derived spectrum and measured published spectra with satisfactory consistence.

  19. Connecting forest ecosystem and microwave backscatter models

    NASA Technical Reports Server (NTRS)

    Kasischke, Eric S.; Christensen, Norman L., Jr.

    1990-01-01

    A procedure is outlined to connect data obtained from active microwave remote sensing systems with forest ecosystem models. The hierarchy of forest ecosystem models is discussed, and the levels at which microwave remote sensing data can be used as inputs are identified. In addition, techniques to utilize forest ecosystem models to assist in the validation of theoretical microwave backscatter models are identified. Several examples to illustrate these connecting processes are presented.

  20. Backscatter Correction Algorithm for TBI Treatment Conditions

    SciTech Connect

    Sanchez-Nieto, B.; Sanchez-Doblado, F.; Arrans, R.; Terron, J.A.; Errazquin, L.

    2015-01-15

    The accuracy requirements in target dose delivery is, according to ICRU, ±5%. This is so not only in standard radiotherapy but also in total body irradiation (TBI). Physical dosimetry plays an important role in achieving this recommended level. The semi-infinite phantoms, customarily used for dosimetry purposes, give scatter conditions different to those of the finite thickness of the patient. So dose calculated in patient’s points close to beam exit surface may be overestimated. It is then necessary to quantify the backscatter factor in order to decrease the uncertainty in this dose calculation. The backward scatter has been well studied at standard distances. The present work intends to evaluate the backscatter phenomenon under our particular TBI treatment conditions. As a consequence of this study, a semi-empirical expression has been derived to calculate (within 0.3% uncertainty) the backscatter factor. This factor depends lineally on the depth and exponentially on the underlying tissue. Differences found in the qualitative behavior with respect to standard distances are due to scatter in the bunker wall close to the measurement point.

  1. Modeling strategies of ultrasound backscattering by blood

    NASA Astrophysics Data System (ADS)

    Guy, Cloutier; David, Savery; Isabelle, Fontaine; Beng Ghee, Teh

    2002-05-01

    Tissue characterization using ultrasound (US) scattering can allow the identification of relevant cellular biophysical information noninvasively. The characterization of the level of red blood cell (RBC) aggregation is one of the proposed applications. Different modeling strategies have been investigated by our group to better understand the mechanisms of US backscattering by blood, and to propose relevant measurable indices of aggregation. It could be hypothesized from these studies that the microstructure formed by RBC clusters is a main determinant of US backscattered power. The structure factor, which is related to the Fourier transform of the microscopic density function of RBCs, is described and used to explain the scattering behavior for different spatial arrangements of nonaggregated and aggregated RBCs. The microscopic density function was described by the Percus-Yevick approximation (nonaggregated RBCs), and for aggregated RBCs, by the Poisson distribution, the Neyman-Scott point process, and very recently by a flow-dependent rheological model. These statistical and microrheological models allowed the study of US backscattered power as a function of the hematocrit, scatterers' size, insonification frequency, and level of RBC aggregation. Experimental results available from the literature were used to validate the different approaches. [Work supported by Canadian Institutes of Health Research (MOP-36467), HSFQ, FCAR, and FRSQ.

  2. Backscatter and attenuation characterization of ventricular myocardium

    NASA Astrophysics Data System (ADS)

    Gibson, Allyson Ann

    2009-12-01

    This Dissertation presents quantitative ultrasonic measurements of the myocardium in fetal hearts and adult human hearts with the goal of studying the physics of sound waves incident upon anisotropic and inhomogeneous materials. Ultrasound has been used as a clinical tool to assess heart structure and function for several decades. The clinical usefulness of this noninvasive approach has grown with our understanding of the physical mechanisms underlying the interaction of ultrasonic waves with the myocardium. In this Dissertation, integrated backscatter and attenuation analyses were performed on midgestational fetal hearts to assess potential differences in the left and right ventricular myocardium. The hearts were interrogated using a 50 MHz transducer that enabled finer spatial resolution than could be achieved at more typical clinical frequencies. Ultrasonic data analyses demonstrated different patterns and relative levels of backscatter and attenuation from the myocardium of the left ventricle and the right ventricle. Ultrasonic data of adult human hearts were acquired with a clinical imaging system and quantified by their magnitude and time delay of cyclic variation of myocardial backscatter. The results were analyzing using Bayes Classification and ROC analysis to quantify potential advantages of using a combination of two features of cyclic variation of myocardial backscatter over using only one or the other feature to distinguish between groups of subjects. When the subjects were classified based on hemoglobin A1c, the homeostasis model assessment of insulin resistance, and the ratio of triglyceride to high-density lipoprotein-cholesterol, differences in the magnitude and normalized time delay of cyclic variation of myocardial backscatter were observed. The cyclic variation results also suggested a trend toward a larger area under the ROC curve when information from magnitude and time delay of cyclic variation is combined using Bayes classification than when

  3. Leaky Rayleigh wave ultrasonic backscattering enhancements: Experimental tests of theory for tilted solid cylinders and cubes

    NASA Astrophysics Data System (ADS)

    Gipson, Karen

    Backscattering enhancements due to acoustic wave coupling into leaky Rayleigh waves on solid elastic cubes and cylinders submerged in water are investigated. A quantitative ray description of the launching and propagation of the leaky Rayleigh waves is verified to be useful. Leaky Rayleigh waves are launched on the surface of an elastic object if the acoustic wavevector's projection along the surface matches the wavevector associated with leaky Rayleigh wave propagation. Once launched, leaky Rayleigh waves on the surface of an elastic object will be partially reflected at the object's truncations, and under certain conditions the reflection process may result in a reversal of the leaky wavevector on the surface so that the leaky radiation is oriented in the backscattering direction. Furthermore, the radiated wavefront can have a vanishing Gaussian curvature which produces a far-field caustic. The leaky wave pressure on the surface of the scatterer is approximated by convolving the incident pressure with an appropriate function describing the response of the surface to a localized pressure input, and the method of images is used to approximate the reflection processes. The resulting reflected pressure field on or near the target's surface is then propagated to the far field using the Rayleigh-Sommerfeld diffraction integral. Tone burst experiments confirm that this approach provides reasonable predictions for a variety of cases including the retroreflection of leaky waves around a comer on the face of a cube, the retroreflection of meridional leaky waves along the length of a cylinder, and the retroreflection of leaky waves launched diagonally across the flat face of a cylinder. The frequency dependence of these mechanisms for backscattering from a cylinder was also investigated using a pressure source capable of producing an impulsive pressure, and the observed time returns for end-reflected helical waves agree with theoretical predictions. For the high frequencies

  4. Observation of stimulated electron acoustic wave scattering: the case for nonlinear kinetic effects

    NASA Astrophysics Data System (ADS)

    Montgomery, D. S.; Cobble, J. A.; Fernandez, J. C.; Rose, H. A.; Focia, R. J.; Russell, D. A.

    2001-10-01

    Electrostatic waves with a frequency and phase velocity between an ion acoustic wave (IAW) and an electron plasma wave (EPW) have been observed with Thomson scattering in inhomogeneous plasmas, and in the backscattered spectrum for homogeneous single hot spot laser plasmas. We show that these waves are consistent with an electron-acoustic wave (EAW) that is a BGK-like mode due to electron trapping. The nonlinear dispersion relation for BGK-like EPW and EAW is discussed, and previous inhomogeneous Trident and Nova data are re-examined in this context. The possible implications of these results for backscattered SRS on the NIF are discussed.

  5. Erythema ab igne.

    PubMed

    Miller, Kristen; Hunt, Raegan; Chu, Julie; Meehan, Shane; Stein, Jennifer

    2011-10-15

    Erythema ab igne is a reticulated, erythematous or hyperpigmented dermatosis that results from chronic and repeated exposure to low levels of infrared radiation. Multiple heat sources have been reported to cause this condition, which include heated reclining chairs, heating pads, hot water bottles, car heaters, electric space heaters, and, more recently, laptop computers. Treatment consists of withdrawing the inciting heat source. Although erythema ab igne carries a good prognosis, it is not necessarily a self-limited diagnosis as patients are at long-term risk of developing subsequent cutaneous malignant conditions, which include squamous cell and merkel-cell carcinomas.

  6. Acoustic biosensors

    PubMed Central

    Fogel, Ronen; Seshia, Ashwin A.

    2016-01-01

    Resonant and acoustic wave devices have been researched for several decades for application in the gravimetric sensing of a variety of biological and chemical analytes. These devices operate by coupling the measurand (e.g. analyte adsorption) as a modulation in the physical properties of the acoustic wave (e.g. resonant frequency, acoustic velocity, dissipation) that can then be correlated with the amount of adsorbed analyte. These devices can also be miniaturized with advantages in terms of cost, size and scalability, as well as potential additional features including integration with microfluidics and electronics, scaled sensitivities associated with smaller dimensions and higher operational frequencies, the ability to multiplex detection across arrays of hundreds of devices embedded in a single chip, increased throughput and the ability to interrogate a wider range of modes including within the same device. Additionally, device fabrication is often compatible with semiconductor volume batch manufacturing techniques enabling cost scalability and a high degree of precision and reproducibility in the manufacturing process. Integration with microfluidics handling also enables suitable sample pre-processing/separation/purification/amplification steps that could improve selectivity and the overall signal-to-noise ratio. Three device types are reviewed here: (i) bulk acoustic wave sensors, (ii) surface acoustic wave sensors, and (iii) micro/nano-electromechanical system (MEMS/NEMS) sensors. PMID:27365040

  7. Acoustic biosensors.

    PubMed

    Fogel, Ronen; Limson, Janice; Seshia, Ashwin A

    2016-06-30

    Resonant and acoustic wave devices have been researched for several decades for application in the gravimetric sensing of a variety of biological and chemical analytes. These devices operate by coupling the measurand (e.g. analyte adsorption) as a modulation in the physical properties of the acoustic wave (e.g. resonant frequency, acoustic velocity, dissipation) that can then be correlated with the amount of adsorbed analyte. These devices can also be miniaturized with advantages in terms of cost, size and scalability, as well as potential additional features including integration with microfluidics and electronics, scaled sensitivities associated with smaller dimensions and higher operational frequencies, the ability to multiplex detection across arrays of hundreds of devices embedded in a single chip, increased throughput and the ability to interrogate a wider range of modes including within the same device. Additionally, device fabrication is often compatible with semiconductor volume batch manufacturing techniques enabling cost scalability and a high degree of precision and reproducibility in the manufacturing process. Integration with microfluidics handling also enables suitable sample pre-processing/separation/purification/amplification steps that could improve selectivity and the overall signal-to-noise ratio. Three device types are reviewed here: (i) bulk acoustic wave sensors, (ii) surface acoustic wave sensors, and (iii) micro/nano-electromechanical system (MEMS/NEMS) sensors.

  8. Global Backscatter Experiment (GLOBE) Results: Aerosol Backscatter Global Distribution and Wavelength Dependence

    NASA Technical Reports Server (NTRS)

    Bowdle, David A.

    1992-01-01

    The GLObal Backscatter Experiment (GLOBE) was initiated by NASA in 1986 as an interagency and international research effort to characterize tropospheric backscatter properties. The primary objective of the program is to develop realistic aerosol backscatter inputs for design and simulation studies for NASA's prospective Laser Atmospheric Wind Sounder (LAWS). To achieve this, GLOBE incorporates several different types of aerosol sensors, which operate from a variety of sensor platforms, covering a wide range of spatial and temporal scales, and measure a diverse set of aerosol physical, chemical, and optical properties. The results of this analysis have provided important new information on the life cycles and physicochemical properties of global scale tropospheric aerosol systems. In addition, GLOBE analytical methods will be useful for the Earth Observing System (EOS) and other studies that involve the assimilation of large, complex atmospheric aerosol databases.

  9. Signal Processing and Calibration of Continuous-Wave Focused CO2 Doppler Lidars for Atmospheric Backscatter Measurement

    NASA Technical Reports Server (NTRS)

    Rothermel, Jeffry; Chambers, Diana M.; Jarzembski, Maurice A.; Srivastava, Vandana; Bowdle, David A.; Jones, William D.

    1996-01-01

    Two continuous-wave(CW)focused C02 Doppler lidars (9.1 and 10.6 micrometers) were developed for airborne in situ aerosol backscatter measurements. The complex path of reliably calibrating these systems, with different signal processors, for accurate derivation of atmospheric backscatter coefficients is documented. Lidar calibration for absolute backscatter measurement for both lidars is based on range response over the lidar sample volume, not solely at focus. Both lidars were calibrated with a new technique using well-characterized aerosols as radiometric standard targets and related to conventional hard-target calibration. A digital signal processor (DSP), a surface acoustic and spectrum analyzer and manually tuned spectrum analyzer signal analyzers were used. The DSP signals were analyzed with an innovative method of correcting for systematic noise fluctuation; the noise statistics exhibit the chi-square distribution predicted by theory. System parametric studies and detailed calibration improved the accuracy of conversion from the measured signal-to-noise ratio to absolute backscatter. The minimum backscatter sensitivity is approximately 3 x 10(exp -12)/m/sr at 9.1 micrometers and approximately 9 x 10(exp -12)/m/sr at 10.6 micrometers. Sample measurements are shown for a flight over the remote Pacific Ocean in 1990 as part of the NASA Global Backscatter Experiment (GLOBE) survey missions, the first time to our knowledge that 9.1-10.6 micrometer lidar intercomparisons were made. Measurements at 9.1 micrometers, a potential wavelength for space-based lidar remote-sensing applications, are to our knowledge the first based on the rare isotope C-12 O(2)-18 gas.

  10. Radio acoustic measurement of temperature profile in the troposphere and stratosphere

    NASA Astrophysics Data System (ADS)

    Matuura, N.; Masuda, Y.; Inuki, H.; Kato, S.; Fukao, S.; Sato, T.; Tsuda, T.

    1986-10-01

    The radio acoustic sounding system (RASS) uses radar to measure the temperature profile in the atmosphere. In the standard technique of atmospheric radar, the radar backscatter results from electrical permittivity variations due to natural phenomena such as turbulence and precipitation. In the RASS technique, the radar backscatter results from periodical permittivity variations due to density/temperature variations imposed on the atmosphere by an acoustic wave artificially generated in such a way that the acoustic wavelength is half the radar (electromagnetic) wavelength. This `Bragg condition' is necessary for efficient backscattering. The backscatter echo of the RASS is affected by the Doppler frequency shift arising both from the speed at which the longitudinal acoustic perturbations propagate (the sound speed), and from the radial bulk velocity in the common volume of the atmosphere-the latter can be measured by the standard technique of turbulence scatter. The observed sound speed is reduced to give the local atmospheric temperature. Here we report an experiment using the RASS, carried out on 1-3 August 1985, which consisted of a high-power, very-high-frequency (VHF) Doppler radar at Shigaraki, Shiga, Japan and a movable high-power acoustic transmitter, and which gave the first experimental proof of the possibility of temperature profiling in the troposphere and stratosphere up to an altitude of ~20 km.

  11. Modeling the frequency dependence (5-120 MHz) of ultrasound backscattering by red cell aggregates in shear flow at a normal hematocrit

    NASA Astrophysics Data System (ADS)

    Fontaine, Isabelle; Cloutier, Guy

    2003-05-01

    The frequency dependence of the ultrasound signal backscattered by blood in shear flow was studied using a simulation model. The ultrasound backscattered signal was computed with a linear model that considers the characteristics of the ultrasound system and tissue acoustic properties. The tissue scattering properties were related to the position and shape of the red blood cells (RBCs). A 2D microrheological model simulated the RBC dynamics in a Couette shear flow system. This iterative model, described earlier [Biophys. J. 82, 1696-1710 (2002)], integrates the hydrodynamic effect of the flow, as well as adhesive and repulsive forces between RBCs. RBC aggregation was simulated at 40% hematocrit and shear rates of 0.05-2 s-1. The RBC aggregate sizes ranged, on average, from 3.3 RBCs at 2 s-1 to 33.5 cells at 0.05 s-1. The ultrasound backscattered power was studied at frequencies between 5-120 MHz and insonification angles between 0-180°. At frequencies below approximately 30 MHz, the ultrasound backscattered power increased as the shear rate was decreased and the size of the aggregates was raised. A totally different scattering behavior was noted above 30 MHz. Typical spectral slopes of the backscattered power (log-log scale) between 5-25 MHz equaled 3.8, whereas slopes down to 0.6 were measured at 0.05 s-1, between 40-60 MHz. The ultrasound backscattered power was shown to be angle dependent at low frequencies (5-25 MHz). The anisotropy persisted at high frequencies (>25 MHz) for small aggregates (at 2 s-1). In conclusion, this study sheds some light on the blood backscattering behavior with an emphasis on the non-Rayleigh regime. Additional experimental studies may be necessary to validate the simulation results, and to fully understand the relation between the ultrasound backscattered power, level of RBC aggregation, shear rate, frequency, and insonification angle.

  12. Atmospheric Backscatter Model Development for CO Sub 2 Wavelengths

    NASA Technical Reports Server (NTRS)

    Deepak, A.; Kent, G.; Yue, G. K.

    1982-01-01

    The results of investigations into the problems of modeling atmospheric backscatter from aerosols, in the lowest 20 km of the atmosphere, at CO2 wavelengths are presented, along with a summary of the relevant aerosol characteristics and their variability, and a discussion of the measurement techniques and errors involved. The different methods of calculating the aerosol backscattering function, both from measured aerosol characteristics and from optical measurements made at other wavelengths, are discussed in detail, and limits are placed on the accuracy of these methods. The effects of changing atmospheric humidity and temperature on the backscatter are analyzed and related to the actual atmosphere. Finally, the results of modeling CO2 backscatter in the atmosphere are presented and the variation with height and geographic location discussed, and limits placed on the magnitude of the backscattering function. Conclusions regarding modeling techniques and modeled atmospheric backscatter values are presented in tabular form.

  13. Mudrocks examined by backscattered electron microscopy

    NASA Technical Reports Server (NTRS)

    Pye, K.; Krinsley, D.

    1983-01-01

    A method of studying mudrocks is developed using backscattered electrons (BSE) in scanning electron microscopy. Commercially available detectors are utilized to mix the BSE and secondary electron signals in order to obtain the optimum image for a particular material. Thin sections or polished rock chip surfaces are examined with BSE which provides both the atomic number contrast and topographic contrast. This technique provides very detailed information about the form and composition of individual grains in the mudrock thin sections and can be used in studies of the source, mode of deposition, diagenesis, and tectonic deformational history of mudrocks.

  14. Elementary polarization properties in the backscattering configuration.

    PubMed

    Arteaga, Oriol; Garcia-Caurel, Enric; Ossikovski, Razvigor

    2014-10-15

    In the normal incidence backscattering configuration, a polarimetric measurement always preserves the reciprocal symmetry. For a reciprocal Jones matrix, the number of elementary polarization properties is reduced from six to four. In this work, the physical interpretation of these properties is examined and they are compared with the equivalent polarization properties in transmission. It is found that, with the exception of natural optical activity, a polarimetric backreflection experiment can essentially provide the same type of information about the anisotropy of a medium as a transmission analysis, although transmission and backreflection information comes in a completely different form. Experimental examples are provided to illustrate the discussion.

  15. Determination of Backscattering Sources in Various Targets

    NASA Technical Reports Server (NTRS)

    Moore, R. K.; Zoughi, R.; Wu, L. K. (Principal Investigator)

    1985-01-01

    The objectives of this research are to identify the primary contributors to 10 GHz radar backscatter from various natural and man-made surfaces and objects, and to use this information in developing new and better models for the scatter. When the true sources are known for the scattering that leads to variation in intensity on radar images, the images (and sets of them) may be interpreted more meaningfully in terms of the variation of parameters of interest for science or application. For example, better interpretation of vegetation images may be possible for yield forecasting and stress detection.

  16. Strain Determination Using Electron Backscatter Diffraction

    SciTech Connect

    Krause, M.; Graff, A.; Altmann, F.

    2010-11-24

    In the present paper we demonstrate the use of electron backscatter diffraction (EBSD) for high resolution elastic strain determination. Here, we focus on analysis methods based on determination of small shifts in EBSD pattern with respect to a reference pattern using cross-correlation algorithms. Additionally we highlight the excellent spatial and depth resolution of EBSD and introduce the use of simulated diffraction patterns based on dynamical diffraction theory for sensitivity estimation. Moreover the potential of EBSD for strain analysis of strained thin films with particular emphasis on appropriate target preparation which respect to occurring lattice defects is demonstrated.

  17. Theoretical and Experimental Study of Radar Backscatter from Sea Ice

    DTIC Science & Technology

    1984-01-01

    predicts that the depolarized backscattering coefficient is zero. Moreover, there is no distinction in this model between vertical and horizontal... Backscattering Cross-Section of First-Year Ice at 13 GHz. 38 angles except vertical incidence, mainly due to the 3rewster angle effect. The depolarized ...theories to properly explain the polarization dependence of the backscatter from sea ice. Because depolarization is a secondary effect for the surface

  18. Nonlinear Acoustics

    DTIC Science & Technology

    1974-02-14

    Wester- velt. [60] Streaming. In 1831, Michael Faraday [61] noted that currents of air were set up in the neighborhood of vibrating plates-the first... ducei in the case of a paramettc amy (from Berktay an Leahy 141). C’ "". k•, SEC 10.1 NONLINEAR ACOUSTICS 345 The principal results of their analysis

  19. Independent measurement of extinction and backscatter profiles in cirrus clouds by using a combined Raman elastic-backscatter lidar.

    PubMed

    Ansmann, A; Wandinger, U; Riebesell, M; Weitkamp, C; Michaelis, W

    1992-11-20

    Height profiles of the extinction and the backscatter coefficients in cirrus clouds are determined independently from elastic- and inelastic- (Raman) backscatter signals. An extended error analysis is given. Examples covering the measured range of extinction-to-backscatter ratios (lidar ratios) in ice clouds are presented. Lidar ratios between 5 and 15 sr are usually found. A strong variation between 2 and 20 sr can be observed within one cloud profile. Particle extinction coefficients determined from inelastic-backscatter signals and from elastic-backscatter signals by using the Klett method are compared. The Klett solution of the extinction profile can be highly erroneous if the lidar ratio varies along the measuring range. On the other hand, simple backscatter lidars can provide reliable information about the cloud optical depth and the mean cloud lidar ratio.

  20. Coherent Backscattering by Particulate Planetary Media of Nonspherical Particles

    NASA Astrophysics Data System (ADS)

    Muinonen, Karri; Penttila, Antti; Wilkman, Olli; Videen, Gorden

    2014-11-01

    The so-called radiative-transfer coherent-backscattering method (RT-CB) has been put forward as a practical Monte Carlo method to compute multiple scattering in discrete random media mimicking planetary regoliths (K. Muinonen, Waves in Random Media 14, p. 365, 2004). In RT-CB, the interaction between the discrete scatterers takes place in the far-field approximation and the wave propagation faces exponential extinction. There is a significant constraint in the RT-CB method: it has to be assumed that the form of the scattering matrix is that of the spherical particle. We aim to extend the RT-CB method to nonspherical single particles showing significant depolarization characteristics. First, ensemble-averaged single-scattering albedos and phase matrices of nonspherical particles are matched using a phenomenological radiative-transfer model within a microscopic volume element. Second, the phenomenologial single-particle model is incorporated into the Monte Carlo RT-CB method. In the ray tracing, the electromagnetic phases within the microscopic volume elements are omitted as having negligible lengths, whereas the phases are duly accounted for in the paths between two or more microscopic volume elements. We assess the computational feasibility of the extended RT-CB method and show preliminary results for particulate media mimicking planetary regoliths. The present work can be utilized in the interpretation of astronomical observations of asteroids and other planetary objects. In particular, the work sheds light on the depolarization characteristics of planetary regoliths at small phase angles near opposition. The research has been partially funded by the ERC Advanced Grant No 320773 entitled “Scattering and Absorption of Electromagnetic Waves in Particulate Media” (SAEMPL), by the Academy of Finland (contract 257966), NASA Outer Planets Research Program (contract NNX10AP93G), and NASA Lunar Advanced Science and Exploration Research Program (contract NNX11AB25G).

  1. Multiscale Interactions and Backscatter in Premixed Combustion

    NASA Astrophysics Data System (ADS)

    Hamlington, Peter; Towery, Colin; O'Brien, Jeffrey; Poludnenko, Alexei; Urzay, Javier; Ihme, Matthias

    2015-11-01

    Multiscale interactions and energy transfer between turbulence and flames are fundamental to understanding and modeling premixed turbulent reacting flows. To investigate such flows, direct numerical simulations of statistically planar turbulent premixed flames have been performed, and the dynamics of kinetic energy transfer are examined in both spectral and physical spaces. In the spectral analysis, two-dimensional kinetic energy spectra and triadic interactions are computed through the flame brush. It is found that there is suppression of turbulent small-scale motions in the combustion products, along with backscatter of energy for a range of scales near the thermal laminar flame width. In the physical-space analysis, a differential filter is applied to examine the transfer of kinetic energy between subgrid and resolved scales in the context of large eddy simulations. Subgrid-scale backscatter of kinetic energy driven by combustion is found to prevail over forward scatter throughout the flame brush. The spectral- and physical-space analyses thus both suggest an enhancement of reverse-cascade phenomena in the flame brush, which is possibly driven by accumulation of kinetic energy in the scales where combustion-induced heat release is preferentially deployed.

  2. Compton backscattered collimated x-ray source

    DOEpatents

    Ruth, Ronald D.; Huang, Zhirong

    1998-01-01

    A high-intensity, inexpensive and collimated x-ray source for applications such as x-ray lithography is disclosed. An intense pulse from a high power laser, stored in a high-finesse resonator, repetitively collides nearly head-on with and Compton backscatters off a bunched electron beam, having relatively low energy and circulating in a compact storage ring. Both the laser and the electron beams are tightly focused and matched at the interaction region inside the optical resonator. The laser-electron interaction not only gives rise to x-rays at the desired wavelength, but also cools and stabilizes the electrons against intrabeam scattering and Coulomb repulsion with each other in the storage ring. This cooling provides a compact, intense bunch of electrons suitable for many applications. In particular, a sufficient amount of x-rays can be generated by this device to make it an excellent and flexible Compton backscattered x-ray (CBX) source for high throughput x-ray lithography and many other applications.

  3. Compton backscattered collmated X-ray source

    DOEpatents

    Ruth, Ronald D.; Huang, Zhirong

    2000-01-01

    A high-intensity, inexpensive and collimated x-ray source for applications such as x-ray lithography is disclosed. An intense pulse from a high power laser, stored in a high-finesse resonator, repetitively collides nearly head-on with and Compton backscatters off a bunched electron beam, having relatively low energy and circulating in a compact storage ring. Both the laser and the electron beams are tightly focused and matched at the interaction region inside the optical resonator. The laser-electron interaction not only gives rise to x-rays at the desired wavelength, but also cools and stabilizes the electrons against intrabeam scattering and Coulomb repulsion with each other in the storage ring. This cooling provides a compact, intense bunch of electrons suitable for many applications. In particular, a sufficient amount of x-rays can be generated by this device to make it an excellent and flexible Compton backscattered x-ray (CBX) source for high throughput x-ray lithography and many other applications.

  4. Radar backscatter properties of milo and soybeans

    NASA Technical Reports Server (NTRS)

    Bush, T. F.; Ulaby, F. T.; Metzler, T.

    1975-01-01

    The radar backscatter from fields of milo and soybeans was measured with a ground based radar as a function of frequency (8-18 GHz), polarization (HH and VV) and angle of incidence (0 deg-70 deg) during the summer of 1974. Supporting ground truth was gathered contemporaneously with the backscatter data. At nadir sigma deg of milo correlated highly, r = 0.96, with soil moisture in the milo field at 8.6 GHz but decreased to a value of r = 0.78 at a frequency of 17.0 GHz. Correlation studies of the variations of sigma deg with soil moisture in the soybean fields were not possible due to a lack of a meaningful soil moisture dynamic range. At the larger angles of incidence, however, sigma deg of soybeans did appear to be dependent on precipitation. It is suggested this phenomenon was caused by the rain altering plant geometry. In general sigma deg of both milo and soybeans had a relatively small dynamic range at the higher angles of incidence and showed no significant dependence on the measured crop parameters.

  5. Compton backscattered collimated x-ray source

    DOEpatents

    Ruth, R.D.; Huang, Z.

    1998-10-20

    A high-intensity, inexpensive and collimated x-ray source is disclosed for applications such as x-ray lithography is disclosed. An intense pulse from a high power laser, stored in a high-finesse resonator, repetitively collides nearly head-on with and Compton backscatters off a bunched electron beam, having relatively low energy and circulating in a compact storage ring. Both the laser and the electron beams are tightly focused and matched at the interaction region inside the optical resonator. The laser-electron interaction not only gives rise to x-rays at the desired wavelength, but also cools and stabilizes the electrons against intrabeam scattering and Coulomb repulsion with each other in the storage ring. This cooling provides a compact, intense bunch of electrons suitable for many applications. In particular, a sufficient amount of x-rays can be generated by this device to make it an excellent and flexible Compton backscattered x-ray (CBX) source for high throughput x-ray lithography and many other applications. 4 figs.

  6. Acoustic transducer for acoustic microscopy

    DOEpatents

    Khuri-Yakub, Butrus T.; Chou, Ching H.

    1990-01-01

    A shear acoustic transducer-lens system in which a shear polarized piezoelectric material excites shear polarized waves at one end of a buffer rod having a lens at the other end which excites longitudinal waves in a coupling medium by mode conversion at selected locations on the lens.

  7. Acoustic transducer for acoustic microscopy

    DOEpatents

    Khuri-Yakub, B.T.; Chou, C.H.

    1990-03-20

    A shear acoustic transducer-lens system is described in which a shear polarized piezoelectric material excites shear polarized waves at one end of a buffer rod having a lens at the other end which excites longitudinal waves in a coupling medium by mode conversion at selected locations on the lens. 9 figs.

  8. Acoustic topological insulator and robust one-way sound transport

    NASA Astrophysics Data System (ADS)

    He, Cheng; Ni, Xu; Ge, Hao; Sun, Xiao-Chen; Chen, Yan-Bin; Lu, Ming-Hui; Liu, Xiao-Ping; Chen, Yan-Feng

    2016-12-01

    Topological design of materials enables topological symmetries and facilitates unique backscattering-immune wave transport. In airborne acoustics, however, the intrinsic longitudinal nature of sound polarization makes the use of the conventional spin-orbital interaction mechanism impossible for achieving band inversion. The topological gauge flux is then typically introduced with a moving background in theoretical models. Its practical implementation is a serious challenge, though, due to inherent dynamic instabilities and noise. Here we realize the inversion of acoustic energy bands at a double Dirac cone and provide an experimental demonstration of an acoustic topological insulator. By manipulating the hopping interaction of neighbouring ’atoms’ in this new topological material, we successfully demonstrate the acoustic quantum spin Hall effect, characterized by robust pseudospin-dependent one-way edge sound transport. Our results are promising for the exploration of new routes for experimentally studying topological phenomena and related applications, for example, sound-noise reduction.

  9. Evaluation of image-based multibeam sonar backscatter classification for benthic habitat discrimination and mapping at Stanton Banks, UK

    NASA Astrophysics Data System (ADS)

    McGonigle, Chris; Brown, Craig; Quinn, Rory; Grabowski, Jonathan

    2009-02-01

    In recent years, efforts have increased to develop quantitative, computer-directed methods for segmentation of multibeam (MBES) backscatter data. This study utilises MBES backscatter data acquired at Stanton Banks (UK) and subsequently processed through the QTC-Multiview software environment in a bid to evaluate the program's ability to perform unsupervised classification. Statistical comparison with ground-truth data (grab, stills and video) enabled cross validation of acoustic segmentation and biological assemblages observed at the site. 132 unspecified variables were extracted from user-specified rectangular patches of the backscatter image, reduced to three vectors by PCA, then clustered and classified by the software. Multivariate analyses of ground-truth data were conducted on 75 stills images and 51 grab samples. Video footage coincident with the stills was divided into 30 s segments and coded by dominant substrate and species. Cross tabulation determined the interrelationship between software classifications, multivariate analysis of the biological assemblages and coded video segments. Multiview optimally identified 19 classes using the automated clustering engine. These were revised to 6 habitats a posteriori, using combined analysis of ground-truth data and Multiview data products. These habitats broadly correspond to major physiographic provinces within the region. Multivariate statistical analysis reveals low levels of assemblage similarity (<35%) for samples occurring within Multiview classes, irrespective of the mode of acquisition. Coded video data is more spatially appropriate than the other methods of ground-truthing investigated, although it is less well suited to the extraction of truly quantitative data. Multivariate analysis indicates assemblages within physiographically distinct Multiview classes have a low degree of biological similarity, supporting the notion that abiotic proxies may be contraindicative of benthic assemblage variations. QTC

  10. Acoustic chaos

    SciTech Connect

    Lauterborn, W.; Parlitz, U.; Holzfuss, J.; Billo, A.; Akhatov, I.

    1996-06-01

    Acoustic cavitation, a complex, spatio-temporal dynamical system, is investigated with respect to its chaotic properties. The sound output, the {open_quote}{open_quote}noise{close_quote}{close_quote}, is subjected to time series analysis. The spatial dynamics of the bubble filaments is captured by high speed holographic cinematography and subsequent digital picture processing from the holograms. Theoretical models are put forward for describing the pattern formation. {copyright} {ital 1996 American Institute of Physics.}

  11. Medical Acoustics

    NASA Astrophysics Data System (ADS)

    Beach, Kirk W.; Dunmire, Barbrina

    Medical acoustics can be subdivided into diagnostics and therapy. Diagnostics are further separated into auditory and ultrasonic methods, and both employ low amplitudes. Therapy (excluding medical advice) uses ultrasound for heating, cooking, permeablizing, activating and fracturing tissues and structures within the body, usually at much higher amplitudes than in diagnostics. Because ultrasound is a wave, linear wave physics are generally applicable, but recently nonlinear effects have become more important, even in low-intensity diagnostic applications.

  12. Optical backscatter characteristics of Arctic polar stratospheric clouds

    NASA Technical Reports Server (NTRS)

    Kent, G. S.; Schaffner, S. K.; Poole, L. R.; Mccormick, M. P.; Hunt, W. H.

    1990-01-01

    Airborne lidar measurements have been made of polar stratospheric clouds (PSCs) during the Airborne Arctic Stratospheric Expedition in January-February 1989. These show the existence of a systematic relationship between the backscatter depolarization ratio and the (aerosol + molecular)/molecular backscatter ratio. The data are consistent with a two population PSC particle model.

  13. Fading characteristics of panchromatic radar backscatter from selected agricultural targets

    NASA Technical Reports Server (NTRS)

    Bush, T. F.; Ulaby, F. T.

    1973-01-01

    An experiment was performed to empirically determine the fading characteristics of backscattered radar signals from four agricultural targets at 9 GHz. After a short review of the statistics of Rayleigh fading backscatter, the data processing method and results of the data are analyzed. Comparison with theory shows adequate agreement with the experimental results, provided of course, the targets are modeled in a correct manner.

  14. Harmonic generation of ion waves due to Brillouin backscattering

    SciTech Connect

    Estabrook, K.; Kruer, W.L.; Haines, M.G.

    1985-05-22

    We report results of simulations of stimulated Brillouin backscatter in which we see the second spatial harmonic of the ion density fluctuation and compare with linear, fluid theory. We also describe examples of the competition between Raman and Brillouin backscatter. 21 refs., 3 figs.

  15. Relating P-band AIRSAR backscatter to forest stand parameters

    NASA Technical Reports Server (NTRS)

    Wang, Yong; Melack, John M.; Davis, Frank W.; Kasischke, Eric S.; Christensen, Norman L., Jr.

    1993-01-01

    As part of research on forest ecosystems, the Jet Propulsion Laboratory (JPL) and collaborating research teams have conducted multi-season airborne synthetic aperture radar (AIRSAR) experiments in three forest ecosystems including temperate pine forest (Duke, Forest, North Carolina), boreal forest (Bonanza Creek Experimental Forest, Alaska), and northern mixed hardwood-conifer forest (Michigan Biological Station, Michigan). The major research goals were to improve understanding of the relationships between radar backscatter and phenological variables (e.g. stand density, tree size, etc.), to improve radar backscatter models of tree canopy properties, and to develop a radar-based scheme for monitoring forest phenological changes. In September 1989, AIRSAR backscatter data were acquired over the Duke Forest. As the aboveground biomass of the loblolly pine forest stands at Duke Forest increased, the SAR backscatter at C-, L-, and P-bands increased and saturated at different biomass levels for the C-band, L-band, and P-band data. We only use the P-band backscatter data and ground measurements here to study the relationships between the backscatter and stand density, the backscatter and mean trunk dbh (diameter at breast height) of trees in the stands, and the backscatter and stand basal area.

  16. Acoustic dose and acoustic dose-rate.

    PubMed

    Duck, Francis

    2009-10-01

    Acoustic dose is defined as the energy deposited by absorption of an acoustic wave per unit mass of the medium supporting the wave. Expressions for acoustic dose and acoustic dose-rate are given for plane-wave conditions, including temporal and frequency dependencies of energy deposition. The relationship between the acoustic dose-rate and the resulting temperature increase is explored, as is the relationship between acoustic dose-rate and radiation force. Energy transfer from the wave to the medium by means of acoustic cavitation is considered, and an approach is proposed in principle that could allow cavitation to be included within the proposed definitions of acoustic dose and acoustic dose-rate.

  17. A method for removing arm backscatter from EPID images

    SciTech Connect

    King, Brian W.; Greer, Peter B.

    2013-07-15

    Purpose: To develop a method for removing the support arm backscatter from images acquired using current Varian electronic portal imaging devices (EPIDs).Methods: The effect of arm backscatter on EPID images was modeled using a kernel convolution method. The parameters of the model were optimized by comparing on-arm images to off-arm images. The model was used to develop a method to remove the effect of backscatter from measured EPID images. The performance of the backscatter removal method was tested by comparing backscatter corrected on-arm images to measured off-arm images for 17 rectangular fields of different sizes and locations on the imager. The method was also tested using on- and off-arm images from 42 intensity modulated radiotherapy (IMRT) fields.Results: Images generated by the backscatter removal method gave consistently better agreement with off-arm images than images without backscatter correction. For the 17 rectangular fields studied, the root mean square difference of in-plane profiles compared to off-arm profiles was reduced from 1.19% (standard deviation 0.59%) on average without backscatter removal to 0.38% (standard deviation 0.18%) when using the backscatter removal method. When comparing to the off-arm images from the 42 IMRT fields, the mean {gamma} and percentage of pixels with {gamma} < 1 were improved by the backscatter removal method in all but one of the images studied. The mean {gamma} value (1%, 1 mm) for the IMRT fields studied was reduced from 0.80 to 0.57 by using the backscatter removal method, while the mean {gamma} pass rate was increased from 72.2% to 84.6%.Conclusions: A backscatter removal method has been developed to estimate the image acquired by the EPID without any arm backscatter from an image acquired in the presence of arm backscatter. The method has been shown to produce consistently reliable results for a wide range of field sizes and jaw configurations.

  18. Rutherford backscattering analysis of contaminants in PET

    NASA Astrophysics Data System (ADS)

    Pierce, D. E.; Pfeffer, R. L.; Sadler, G. D.

    1997-05-01

    Rutherford Backscattering Spectrometry (RBS) was used to understand the sorption and desorption of organic contaminants in the polymer Poly(ethylene terephthalate), or PET. Samples were exposed to a range of organics to simulate contamination of PET that can take place in the post-consumer waste stream. From RBS analysis, concentration depth profiles were shown to vary from a monolayer regime surface layer to a saturation level, depending on the contaminant. Heat treatments were also applied to contaminated polymer to simulate thermal processing steps in the recycling of PET. Heating caused a dramatic decrease in contaminants and in some cases a complete removal of contamination was achieved to the limit of RBS detectability.

  19. Reducing parametric backscattering by polarization rotation

    NASA Astrophysics Data System (ADS)

    Barth, Ido; Fisch, Nathaniel

    2016-10-01

    When a laser passes through underdense plasmas, Raman and Brillouin Backscattering can reflect a substantial portion of the incident laser energy. This is a major loss mechanism, for example, in inertial confinement fusion. However, by slow rotation of the incident linear polarization, the overall reflectivity can be reduced significantly. Particle in cell simulations show that, for parameters similar to those of indirect drive fusion experiments, polarization rotation reduces the reflectivity by a factor of 5. A general, fluid-model based, analytical estimation for the reflectivity reduction agrees with simulations. This work was supported by NNSA Grant No. DE- NA0002948, AFOSR Grant No. FA9550-15-1-0391, and DOE Contract No. DE-AC02-09CH11466.

  20. A dynamic localization model with stochastic backscatter

    NASA Technical Reports Server (NTRS)

    Carati, Daniele; Ghosal, Sandip

    1994-01-01

    The modeling of subgrid scales in large-eddy simulation (LES) has been rationalized by the introduction of the dynamic localization procedure. This method allows one to compute rather than prescribe the unknown coefficients in the subgrid-scale model. Formally, the LES equations are supposed to be obtained by applying to the Navier-Stokes equations a 'grid filter' operation. Though the subgrid stress itself is unknown, an identity between subgrid stresses generated by different filters has been derived. Although preliminary tests of the Dynamic Localization Model (DLM) with k-equation have been satisfactory, the use of a negative eddy viscosity to describe backscatter is probably a crude representation of the physics of reverse transfer of energy. Indeed, the model is fully deterministic. Knowing the filtered velocity field and the subgrid-scale energy, the subgrid stress is automatically determined. We know that the LES equations cannot be fully deterministic since the small scales are not resolved. This stems from an important distinction between equilibrium hydrodynamics and turbulence. In equilibrium hydrodynamics, the molecular motions are also not resolved. However, there is a clear separation of scale between these unresolved motions and the relevant hydrodynamic scales. The result of molecular motions can then be separated into an average effect (the molecular viscosity) and some fluctuations. Due to the large number of molecules present in a box with size of the order of the hydrodynamic scale, the ratio between fluctuations and the average effect should be very small (as a result of the 'law of large numbers'). For that reason, the hydrodynamic balance equations are usually purely deterministic. In turbulence, however, there is no clear separation of scale between small and large eddies. In that case, the fluctuations around a deterministic eddy viscosity term could be significant. An eddy noise would then appear through a stochastic term in the subgrid

  1. Acoustic Tooth Cleaner

    NASA Technical Reports Server (NTRS)

    Heyman, J. S.

    1984-01-01

    Acoustically-energized water jet aids in plaque breakdown. Acoustic Wand includes acoustic transducer 1/4 wave plate, and tapered cone. Together elements energize solution of water containing mild abrasive injected into mouth to help prevent calculous buildup.

  2. Characterizing riverbed sediment using high-frequency acoustics 1: spectral properties of scattering

    USGS Publications Warehouse

    Buscombe, Daniel D.; Grams, Paul E.; Kaplinski, Matt A.

    2014-01-01

    Bed-sediment classification using high-frequency hydro-acoustic instruments is challenging when sediments are spatially heterogeneous, which is often the case in rivers. The use of acoustic backscatter to classify sediments is an attractive alternative to analysis of topography because it is potentially sensitive to grain-scale roughness. Here, a new method is presented which uses high-frequency acoustic backscatter from multibeam sonar to classify heterogeneous riverbed sediments by type (sand, gravel,rock) continuously in space and at small spatial resolution. In this, the first of a pair of papers that examine the scattering signatures from a heterogeneous riverbed, methods are presented to construct spatially explicit maps of spectral properties from geo-referenced point clouds of geometrically and radiometrically corrected echoes. Backscatter power spectra are computed to produce scale and amplitude metrics that collectively characterize the length scales of stochastic measures of riverbed scattering, termed ‘stochastic geometries’. Backscatter aggregated over small spatial scales have spectra that obey a power-law. This apparently self-affine behavior could instead arise from morphological- and grain-scale roughnesses over multiple overlapping scales, or riverbed scattering being transitional between Rayleigh and geometric regimes. Relationships exist between stochastic geometries of backscatter and areas of rough and smooth sediments. However, no one parameter can uniquely characterize a particular substrate, nor definitively separate the relative contributions of roughness and acoustic impedance (hardness). Combinations of spectral quantities do, however, have the potential to delineate riverbed sediment patchiness, in a data-driven approach comparing backscatter with bed-sediment observations (which is the subject of part two of this manuscript).

  3. Laptop induced erythema ab igne.

    PubMed

    Nayak, Sudhir U K; Shenoi, Shrutakirthi D; Prabhu, Smitha

    2012-03-01

    Erythema ab igne is a reticular, pigmented dermatosis caused by prolonged and repeated exposure to infrared radiation that is insufficient to produce a burn. The use of laptop computers has increased manifold in the recent past. Prolonged contact of the laptop with the skin can lead to the development of erythema ab igne. We present a case of erythema ab igne secondary to laptop use in an Indian student.

  4. Acoustic transducer

    DOEpatents

    Drumheller, D.S.

    1997-12-30

    An acoustic transducer is described comprising a one-piece hollow mandrel into the outer surface of which is formed a recess with sides perpendicular to the central axis of the mandrel and separated by a first distance and with a bottom parallel to the central axis and within which recess are a plurality of washer-shaped discs of a piezoelectric material and at least one disc of a temperature-compensating material with the discs being captured between the sides of the recess in a pre-stressed interference fit, typically at 2,000 psi of compressive stress. The transducer also includes a power supply and means to connect to a measurement device. The transducer is intended to be used for telemetry between a measurement device located downhole in an oil or gas well and the surface. The transducer is of an construction that is stronger with fewer joints that could leak fluids into the recess holding the piezoelectric elements than is found in previous acoustic transducers. 4 figs.

  5. Acoustic transducer

    DOEpatents

    Drumheller, Douglas S.

    1997-01-01

    An acoustic transducer comprising a one-piece hollow mandrel into the outer surface of which is formed a recess with sides perpendicular to the central axis of the mandrel and separated by a first distance and with a bottom parallel to the central axis and within which recess are a plurality of washer-shaped discs of a piezoelectric material and at least one disc of a temperature-compensating material with the discs being captured between the sides of the recess in a pre-stressed interference fit, typically at 2000 psi of compressive stress. The transducer also includes a power supply and means to connect to a measurement device. The transducer is intended to be used for telemetry between a measurement device located downhole in an oil or gas well and the surface. The transducer is of an construction that is stronger with fewer joints that could leak fluids into the recess holding the piezoelectric elements than is found in previous acoustic transducers.

  6. Interference phenomena at backscattering by ice crystals of irregular shape

    NASA Astrophysics Data System (ADS)

    Konoshonkin, Alexander V.; Kustova, Natalia V.; Borovoi, Anatoli G.

    2015-11-01

    It is shown that light backscattering by hexagonal ice crystals of cirrus clouds is formed by both diffraction and interference phenomena. Diffraction determines the angular width of the backscattering peak and interference produces the interference rings inside the peak. By use of a simplest model for distortion of the pristine hexagonal shape, we show that the shape distortion leads to both oscillations of the scattering (Mueller) matrix within the backscattering peak and to a strong increase of the depolarization, color, and lidar ratios needed for interpretation of lidar signals.

  7. X-ray backscatter imaging of nuclear materials

    DOEpatents

    Chapman, Jeffrey Allen; Gunning, John E; Hollenbach, Daniel F; Ott, Larry J; Shedlock, Daniel

    2014-09-30

    The energy of an X-ray beam and critical depth are selected to detect structural discontinuities in a material having an atomic number Z of 57 or greater. The critical depth is selected by adjusting the geometry of a collimator that blocks backscattered radiation so that backscattered X-ray originating from a depth less than the critical depth is not detected. Structures of Lanthanides and Actinides, including nuclear fuel rod materials, can be inspected for structural discontinuities such as gaps, cracks, and chipping employing the backscattered X-ray.

  8. Interference phenomena at backscattering by ice crystals of cirrus clouds.

    PubMed

    Borovoi, Anatoli; Kustova, Natalia; Konoshonkin, Alexander

    2015-09-21

    It is shown that light backscattering by hexagonal ice crystals of cirrus clouds is formed within the physical-optics approximation by both diffraction and interference phenomena. Diffraction determines the angular width of the backscattering peak and interference produces the interference rings inside the peak. By use of a simple model for distortion of the pristine hexagonal shape, we show that the shape distortion leads to both oscillations of the scattering (Mueller) matrix within the backscattering peak and to a strong increase of the depolarization, color, and lidar ratios needed for interpretation of lidar signals.

  9. Backscattering measurements of micron-sized spherical particles.

    PubMed

    Heffernan, Brendan M; Heinson, Yuli W; Maughan, Justin B; Chakrabarti, Amitabha; Sorensen, Christopher M

    2016-04-20

    An apparatus was designed and assembled to measure scattered light in the range of 180°±6° where enhanced backscattering, the cause of a glory, occurs. The apparatus was calibrated and tested using Fraunhofer circular aperture diffraction, angle of incidence correction, and a diffuse reflector. Theory indicates that backscattering is strongly dependent on particle size, refractive index, and shape. Experimental measurements from polystyrene latex spheres of two sizes and water droplets showed good agreement with Mie theory, but also indicated the extreme sensitivity of the backscattering to particle parameters. The results presented should have use in the fields of particle scattering, particle metrology, and LIDAR.

  10. X-Ray Backscatter Machine Support Frame

    NASA Technical Reports Server (NTRS)

    Cannon, Brooke

    2010-01-01

    This summer at Kennedy Space Center, I spent 10 weeks as an intern working at the Prototype Development Lab. During this time I learned about the design and machining done here at NASA. I became familiar with the process from where a design begins in Pro/Engineer and finishes at the hands of the machinists. As an intern I was given various small jobs to do and then one project of my own. My personal project was a job for the Applied Physics Lab; in their work they use an X-Ray Backscatter machine. Previously it was resting atop a temporary frame that limited the use of the machine. My job was to design a frame for the machine to rest upon that would allow a full range of sample sizes. The frame was required to support the machine and provide a strain relief for the cords attached to the machine as it moved in the x and y directions. Calculations also had to be done to be sure the design would be able to withstand any loads or outside sources of stress. After the calculations proved the design to be ready to withstand the requirements, the parts were ordered or fabricated, as required. This helped me understand the full process of jobs sent to the Prototype Development Lab.

  11. Portable fluorescence meter with reference backscattering channel

    NASA Astrophysics Data System (ADS)

    Kornilin, Dmitriy V.; Grishanov, Vladimir N.; Zakharov, Valery P.; Burkov, Dmitriy S.

    2016-09-01

    Methods based on fluorescence and backscattering are intensively used for determination of the advanced glycation end products (AGE) concentration in the biological tissues. There are strong correlation between the AGE concentration and the severity of such diseases like diabetes, coronary heart disease and renal failure. This fact can be used for diagnostic purposes in medical applications. Only few investigations in this area can be useful for development of portable and affordable in vivo AGE meter because the most of them are oriented on using spectrometers. In this study we describe the design and the results of tests on volunteers of portable fluorescence meter based on two photodiodes. One channel of such fluorimeter is used for measurement of the autofluorescence (AF) intensity, another one - for the intensity of elastically scattered radiation, which can be used as a reference. This reference channel is proposed for normalization of the skin autofluorescence signal to the human skin photo type. The fluorimeter, that was developed is relatively compact and does not contain any expensive optical and electronic components. The experimental results prove that proposed tool can be used for the AGE estimation in human skin.

  12. Acoustic cryocooler

    DOEpatents

    Swift, Gregory W.; Martin, Richard A.; Radenbaugh, Ray

    1990-01-01

    An acoustic cryocooler with no moving parts is formed from a thermoacoustic driver (TAD) driving a pulse tube refrigerator (PTR) through a standing wave tube. Thermoacoustic elements in the TAD are spaced apart a distance effective to accommodate the increased thermal penetration length arising from the relatively low TAD operating frequency in the range of 15-60 Hz. At these low operating frequencies, a long tube is required to support the standing wave. The tube may be coiled to reduce the overall length of the cryocooler. One or two PTR's are located on the standing wave tube adjacent antinodes in the standing wave to be driven by the standing wave pressure oscillations. It is predicted that a heat input of 1000 W at 1000 K will maintian a cooling load of 5 W at 80 K.

  13. Acoustic transducer

    DOEpatents

    Drumheller, Douglas S.

    2000-01-01

    An active acoustic transducer tool for use down-hole applications. The tool includes a single cylindrical mandrel including a shoulder defining the boundary of a narrowed portion over which is placed a sandwich-style piezoelectric tranducer assembly. The piezoelectric transducer assembly is prestressed by being placed in a thermal interference fit between the shoulder of the mandrel and the base of an anvil which is likewise positioned over the narrower portion of the mandrel. In the preferred embodiment, assembly of the tool is accomplished using a hydraulic jack to stretch the mandrel prior to emplacement of the cylindrical sandwich-style piezoelectric transducer assembly and anvil. After those elements are positioned and secured, the stretched mandrel is allowed to return substantially to its original (pre-stretch) dimensions with the result that the piezoelectric transducer elements are compressed between the anvil and the shoulder of the mandrel.

  14. Acoustic Performance of 3D Printed Nanocomposite Earmuff

    PubMed Central

    Ahmadi, Saeid; Nassiri, Parvin; Ghasemi, Ismaeil; Monazzam Ep, Mohammad R.

    2016-01-01

    Introduction: Hearing protection devices are one of the primary noise reduction tools in developing countries. This study is intended to produce and apply acrylonitrile butadiene styrene (ABS)/clay nanocomposites to fabricate a laboratory single cup earmuffs and then compare it with double cup and single cup pure ABS earmuffs in terms of noise attenuation performance and comfort. In addition, the noise attenuation performance of single cup pure ABS earmuffs is compared with double cup pure ABS earmuffs. Methods: ABS/nanoclay filament was fabricated using a twin screw extruder. A three dimensional (3D) printing machine and a 3D model of earcup, designed by solid work software, were applied to print single and double cup earmuffs using ABS/nanoclay composite and pure ABS filaments. Finally, using an acoustic test fixture, objective noise attenuation test was performed on three different types of earmuffs, including with and without nano material and a secondary cup. Moreover, earmuffs weight was measured as a comfort component. Results: Insertion loss and calculated noise reduction rating (NRR) of single cup ABS/nanoclay earmuffs (NRR=19.4 dB) and double cup pure ABS earmuffs (NRR=18.93 dB) were improved in comparison with single cup pure ABS earmuffs (NRR=15.7 dB). Additionally, both single cup earmuffs were significantly lighter than double cup earmuffs. Although single cup nano and double cup earmuffs had nearly the same attenuation performance, single cup nano earmuffs were 74 gr lighter than double cup earmuffs, so with reference to comfort, single cup nano earmuffs will probably be more acceptable. Conclusions: From this survey it might be concluded that, even though single cup ABS/nanoclay earmuffs was lighter than double cup pure ABS earmuffs, it had approximately more attenuation performance in comparison with double cup pure ABS earmuffs. Consequently, users are probably more prone to wear light- weight single cup ABS/nanoclay earmuffs as a result of

  15. Analysis of the backscatter spectrum in an ionospheric modification experiment

    NASA Technical Reports Server (NTRS)

    Kim, H.

    1973-01-01

    Predictions of the backscatter spectrum are compared, including effects of ionospheric inhomogeneity with experimental observations of incoherent backscatter from an artificially heated region. Calculations show that the strongest backscatter echo received is not, in fact, from the reflection level, but from a region some distance below (about 0.5 km for an experiment carried out at Arecibo), where the pump wave from a HF transmitter approximately 100 kW) is below the threshold for parametric amplification. By taking the standing wave pattern of the pump into account, asymmetry is explained of the up-shifted and down-shifted plasma lines in the backscatter spectrum, and the several peaks typically observed in the region of the spectrum near the HF transmitter frequency.

  16. Objective backscattering properties measurements at 2.52 terahertz

    NASA Astrophysics Data System (ADS)

    Li, Qi; Zhou, Yi; Li, Qian; Fan, Chang-Kun; Zhao, Yong-Peng; Chen, De-Ying

    2016-10-01

    We present a system to measure objective backscattering properties at 2.52 terahertz (THz). The optical setup combining 90° off-axis parabolic mirrors with 15° off-axis parabolic mirror decreases the size of the system and then realizes its compact structure. The calibration object, a conducting sphere with a diameter of 50 mm, was introduced to eliminate the influence of the instability of THz radiation and the background noise on measurement results. The lock-in amplifier was adopted to enhance the signal-to-noise ratio (SNR) and then make it possible to observe delicate backscattering behaviors on the surface of the object. Backscattering properties of four scale models were measured in this paper. Experimental results indicate that the maximal error of our system is less than 1 dB, paving the way for practical measurements of objective backscattering properties at THz frequencies.

  17. Power coupling characteristics between FBG and back-scattering signals

    NASA Astrophysics Data System (ADS)

    Li, Jianzhi; Zhao, Desheng; Hou, Yuemin; Sun, Baochen

    2017-03-01

    The property and compatibility between fiber Bragg grating (FBG) and back-scattering signals are investigated by employing optical time domain reflectometry. We compare the power spectrums of spontaneous Brillouin scattering (SpBS), simultaneous Brillouin scattering (SBS) and Rayleigh scattering (RS), and coupling mechanism between FBG and back-scattering signal is explored. Experimental results show that the region of FBG contributes to the backscatter power and causes the desired reflection, and the power peak of FBG in SBS power spectrum is the sharpest among back-scattering light power spectrums and broadens with the decrease of spatial resolution. Moreover, the FBG-based method is used to find the location of temperature or stain event for scatter-based distributed sensors.

  18. Coherent backscattering of light with nonlinear atomic scatterers

    SciTech Connect

    Wellens, T.; Gremaud, B.; Delande, D.; Miniatura, C.

    2006-01-15

    We study coherent backscattering of a monochromatic laser by a dilute gas of cold two-level atoms in the weakly nonlinear regime. The nonlinear response of the atoms results in a modification of both the average field propagation (nonlinear refractive index) and the scattering events. Using a perturbative approach, the nonlinear effects arise from inelastic two-photon scattering processes. We present a detailed diagrammatic derivation of the elastic and inelastic components of the backscattering signal for both scalar and vectorial photons. In particular, we show that the coherent backscattering phenomenon originates in some cases from the interference between three different scattering amplitudes. This is in marked contrast with the linear regime where it is due to the interference between two different scattering amplitudes. In particular we show that, if elastically scattered photons are filtered out from the photodetection signal, the nonlinear backscattering enhancement factor exceeds the linear barrier of 2, consistently with a three-amplitude interference effect.

  19. Aerosol measurement program strategy for global aerosol backscatter model development

    NASA Technical Reports Server (NTRS)

    Bowdle, David A.

    1985-01-01

    The purpose was to propose a balanced program of aerosol backscatter research leading to the development of a global model of aerosol backscatter. Such a model is needed for feasibility studies and systems simulation studies for NASA's prospective satellite-based Doppler lidar wind measurement system. Systems of this kind measure the Doppler shift in the backscatter return from small atmospheric aerosol wind tracers (of order 1 micrometer diameter). The accuracy of the derived local wind estimates and the degree of global wind coverage for such a system are limited by the local availability and by the global scale distribution of natural aerosol particles. The discussions here refer primarily to backscatter model requirements at CO2 wavelengths, which have been selected for most of the Doppler lidar systems studies to date. Model requirements for other potential wavelengths would be similar.

  20. Preliminary Lidar Experiment to Study the Backscatter Amplification

    NASA Astrophysics Data System (ADS)

    Razenkov, Igor A.; Banakh, Victor A.

    2016-06-01

    Long-term continuous measurements for detection relative backscatter amplification on a horizontal path of 2 km long are performed by using a specific micro pulse lidar. The laser beam path is limited by a solid obstacle. The lidar is located next to an ultrasonic anemometer that measures 3D wind velocity and temperature; the laser spot on the obstacle is observed by using a telephoto lens. The results showed that the backscatter amplification has a clear diurnal variation. Moreover, the backscatter amplification was completely absent in the morning and evening under neutral stratification in the atmospheric surface layer. At night and in the daytime there was a significant increase of the backscatter amplification coefficient.

  1. Coherent backscattering of light in nematic liquid crystals

    SciTech Connect

    Aksenova, E. V. Kuz'min, V. L.; Romanov, V. P.

    2009-03-15

    Multiple light scattering by director fluctuations in nematic liquid crystals is considered. A uniform director orientation is assumed to be specified by an applied magnetic field. The coherent backscattering effect, which consists in the presence of a sharp light backscattering peak, is studied. The Bethe-Salpeter equation is used to calculate the multiple scattering intensity taking into account the contributions of ladder and cyclic diagrams. An analytical expression for the angular and polarization dependences of the coherent backscattering intensity is obtained in terms of the diffusion approximation. The calculation and experimental results are compared. The developed theory is shown to qualitatively describe the elliptical shape of the backscattering cone, to explain the absence of a coherent contribution for crossed polarizations, and to calculate the relative peak height.

  2. Terrain-analysis procedures for modeling radar backscatter

    NASA Technical Reports Server (NTRS)

    Schaber, G. G.; Berlin, G. L.; Pike, R. J.

    1980-01-01

    Procedures developed to obtain both raw measured and surface roughness statistics for radar backscatter modeling are described. A comprehensive and highly flexible software package for terrain analysis is introduced.

  3. BASIS: A New Backscattering Spectrometer at the SNS

    SciTech Connect

    Mamontov, Eugene; Zamponi, Michaela M; Hammons, Stephanie E; Keener, Wylie S; Hagen, Mark E; Herwig, Kenneth W

    2008-01-01

    A new spectrometer named BASIS has recently entered the general user program at the Spallation Neutron Source. BASIS is an acronym for Backscattering Silicon Spectrometer. While there are several operational reactor-based spectrometers that utilize backscattering reflection from silicon single crystals, such as IN10 and IN16 [1] at the ILL, France; HFBS [2] at the NCNR, USA; and SPHERES [3] at the FRM-II, JCNS, Germany, BASIS is the first silicon backscattering spectrometer built on a spallation neutron source. Conceptually, it is similar to previously built time-of-flight backscattering spectrometers that utilize reflections from pyrolytic graphite or mica, such as IRIS [4] and OSIRIS [5] at the ISIS, UK; LAM-80 [6] at the KENS, Japan; or MARS [7] at the SINQ, Switzerland.

  4. Automatic scaling of HF swept-frequency backscatter ionograms

    NASA Astrophysics Data System (ADS)

    Song, Huan; Hu, Yaogai; Jiang, Chunhua; Zhou, Chen; Zhao, Zhengyu

    2015-05-01

    This paper describes a method for automatically scaling HF swept-frequency backscatter ionograms, which can be applied to a low-power oblique backscatter sounding system. Based on the information of vertical echo in the ionogram, propagation mode is recognized from the amplitude differences between E layer and F layer echoes. Points on the leading edge are extracted by using minimum group path delay theory. The spurious points are removed by using residual analysis. A multiple linear polynomial was adopted to fit the extracted leading edge points. Smooth fitting curves can then be obtained. Automatic scaling results from 362 ionograms show that the proposed method can efficiently recognize propagation modes and extract leading edge curves by taking full advantages of echo characteristics and echo amplitudes in the ionograms. This novel method can be applied into real-time backscatter ionogram scaling, which facilitates the extensive usage of oblique backscatter soundings.

  5. Monte Carlo simulation of laser backscatter from sea water

    NASA Astrophysics Data System (ADS)

    Koerber, B. W.; Phillips, D. M.

    1982-01-01

    A Monte Carlo simulation study of laser backscatter from sea water has been carried out to provide data required to assess the feasibility of measuring inherent optical propagation properties of sea water from an aircraft. The possibility was examined of deriving such information from the backscatter component of the return signals measured by the WRELADS laser airborne depth sounder system. Computations were made for various water turbidity conditions and for different fields of view of the WRELADS receiver. Using a simple model fitted to the computed backscatter data, it was shown that values of the scattering data absorption coefficients can be derived from the initial amplitude and the decay rate of the backscatter envelope.

  6. Simulation of coherent backscattering of light in nematic liquid crystals

    SciTech Connect

    Aksenova, E. V. Kokorin, D. I. Romanov, V. P.

    2012-08-15

    Multiple scattering of light by the fluctuations of the director in a nematic liquid crystal (NLC) aligned by a magnetic field is considered. A peak of coherent backscattering is calculated by numerical simulation. Since the indicatrix of single scattering for a liquid crystal (LC) is known exactly, the calculations are carried out without any simplifying assumptions on the parameters of the liquid crystal. Multiple scattering is simulated as a random walk of photons in the medium. A peak of coherent backscattering in such a medium is very narrow; therefore, the so-called semianalytical method is applied. The parameters of the backscattering peak obtained by numerical simulation are compared with the available experimental data and with the results of analytical approximations. It turns out that the experimental data are in good agreement with the results of simulation. The results of numerical simulation adequately describe the anisotropy and the width of the backscattering peak.

  7. Acoustic telemetry.

    SciTech Connect

    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.

  8. Directional ultrasonic backscattering in polycrystals with elongated grains

    NASA Astrophysics Data System (ADS)

    Lobkis, O. I.; Yang, L.; Li, J.; Rokhlin, S. I.

    2012-05-01

    An analytical solution for a three dimensional integral representation of the backscattering (BS) coefficient in polycrystals with elongated grains is obtained. The theory was applied to evaluation of experimental data in Ti alloy with duplex microstructure, which consists of micro-textured regions (MTR) and smaller crystallites. Experiment shows that for microstructure characterization there is significant advantage in using the directional ratios of backscattering coefficients instead their absolute values for data analysis.

  9. E and F Layer H.F. Volume Backscatter Reflectivities.

    DTIC Science & Technology

    1980-02-01

    operations were scheduled for two twenty-four hour runs each week. Three backscatter ionograms , one on boresight and one to east and west of boresight...were made each hour. The ionograms covered 6 to 26 MNlz in freq., and 1000 to 4000 km in range which is the full operating range of the radar. The three... ionograms required about four minutes to complete. ,These were followed by a series of fixed frequency backscatter surroundings to examine the signal

  10. Improving riverbed sediment classification using backscatter and depth residual features of multi-beam echo-sounder systems.

    PubMed

    Eleftherakis, Dimitrios; Amiri-Simkooei, AliReza; Snellen, Mirjam; Simons, Dick G

    2012-05-01

    Riverbed and seafloor sediment classification using acoustic remote sensing techniques is of high interest due to their high coverage capabilities at limited cost. This contribution presents the results of riverbed sediment classification using multi-beam echo-sounder data based on an empirical method. Two data sets are considered, both taken at the Waal River, namely Sint Andries and Nijmegen. This work is a follow-up to the work carried out by Amiri-Simkooei et al. [J. Acoust. Soc. Am. 126(4), 1724-1738 (2009)]. The empirical method bases the classification on features of the backscatter strength and depth residuals. A principal component analysis is used to identify the most appropriate and informative features. Clustering is then applied to the principal components resulting from this set of features to assign a sediment class to each measurement. The results show that the backscatter strength features discriminate between different classes based on the sediment properties, whereas the depth residual features discriminate classes based on riverbed forms such as the "fixed layer" (stone having riprap structure) and riverbed ripples. Combination of these two sets of features is highly recommended because they provide complementary information on both the composition and the structure of the riverbed.

  11. Laser speckle visibility acoustic spectroscopy in soft turbid media

    NASA Astrophysics Data System (ADS)

    Wintzenrieth, Frédéric; Cohen-Addad, Sylvie; Le Merrer, Marie; Höhler, Reinhard

    2014-03-01

    We image the evolution in space and time of an acoustic wave propagating along the surface of turbid soft matter by shining coherent light on the sample. The wave locally modulates the speckle interference pattern of the backscattered light and the speckle visibility[2] is recorded using a camera. We show both experimentally and theoretically how the temporal and spatial correlations in this pattern can be analyzed to obtain the acoustic wavelength and attenuation length. The technique is validated using shear waves propagating in aqueous foam.[3] It may be applied to other kinds of acoustic wave in different forms of turbid soft matter, such as biological tissues, pastes or concentrated emulsions. Now at Université Lyon 1 (ILM).

  12. Subgrid-scale backscatter in transitional and turbulent flows

    NASA Technical Reports Server (NTRS)

    Piomelli, Ugo; Cabot, William H.; Moin, Parviz; Lee, Sangsan

    1990-01-01

    Most subgrid-scale (SGS) models for large-eddy simulations are absolutely dissipative (that is, they remove energy from the large scales at each point in the physical space). The actual SGS stresses, however, may transfer energy to the large scales (backscatter) at a given location. Direct numerical simulations of turbulent channel flow and compressible isotropic turbulence are used to study the backscatter phenomena. In all flows considered roughly 50 percent of the grid points were experiencing backscatter when a Fourier cutoff filter was used. The backscatter fraction was less with a Gaussian filter, and intermediate with a box filter in physical space. Moreover, the backscatter and forward scatter contributions to the SGS dissipation were comparable, and each was often much larger than the total SGS dissipation. The SGS dissipation (normalized by total dissipation) increased with filter width almost independently of filter type and Reynolds number. The amount of backscatter showed an increasing trend with Reynolds numbers. In the near-wall region of the channel, events characterized by strong Reynolds shear stress correlated fairly well with areas of high SGS dissipation (both forward and backward). In compressible isotropic turbulence similar results were obtained, independent of fluctuation Mach number.

  13. TCR backscattering characterization for microwave remote sensing

    NASA Astrophysics Data System (ADS)

    Riccio, Giovanni; Gennarelli, Claudio

    2014-05-01

    A Trihedral Corner Reflector (TCR) is formed by three mutually orthogonal metal plates of various shapes and is a very important scattering structure since it exhibits a high monostatic Radar Cross Section (RCS) over a wide angular range. Moreover it is a handy passive device with low manufacturing costs and robust geometric construction, the maintenance of its efficiency is not difficult and expensive, and it can be used in all weather conditions (i.e., fog, rain, smoke, and dusty environment). These characteristics make it suitable as reference target and radar enhancement device for satellite- and ground-based microwave remote sensing techniques. For instance, TCRs have been recently employed to improve the signal-to-noise ratio of the backscattered signal in the case of urban ground deformation monitoring [1] and dynamic survey of civil infrastructures without natural corners as the Musmeci bridge in Basilicata, Italy [2]. The region of interest for the calculation of TCR's monostatic RCS is here confined to the first quadrant containing the boresight direction. The backscattering term is presented in closed form by evaluating the far-field scattering integral involving the contributions related to the direct illumination and the internal bouncing mechanisms. The Geometrical Optics (GO) laws allow one to determine the field incident on each TCR plate and the patch (integration domain) illuminated by it, thus enabling the use of a Physical Optics (PO) approximation for the corresponding surface current densities to consider for integration on each patch. Accordingly, five contributions are associated to each TCR plate: one contribution is due to the direct illumination of the whole internal surface; two contributions originate by the impinging rays that are simply reflected by the other two internal surfaces; and two contributions are related to the impinging rays that undergo two internal reflections. It is useful to note that the six contributions due to the

  14. An Integrated Backscatter Ultrasound Technique for the Detection of Coronary and Carotid Atherosclerotic Lesions

    PubMed Central

    Kawasaki, Masanori

    2015-01-01

    The instability of carotid and coronary plaques has been reported to be associated with acute coronary syndrome, strokes and other cerebrovascular events. Therefore, recognition of the tissue characteristics of carotid and coronary plaques is important to understand and prevent coronary and cerebral artery disease. Recently, an ultrasound integrated backscatter (IB) technique has been developed. The ultrasound IB power ratio is a function of the difference in acoustic characteristic impedance between the medium and target tissue, and the acoustic characteristic impedance is determined by the density of tissue multiplied by the speed of sound. This concept allows for tissue characterization of carotid and coronary plaques for risk stratification of patients with coronary and cerebral artery disease. Two- and three-dimensional IB color-coded maps for the evaluation of tissue components consist of four major components: fibrous, dense fibrosis, lipid pool and calcification. Although several ultrasound techniques using special mathematical algorithms have been reported, a growing body of literature has shown the reliability and usefulness of the IB technique for the tissue characterization of carotid and coronary plaques. This review summarizes concepts, experimental procedures, image reliability and the application of the IB technique. Furthermore, the IB technique is compared with other techniques. PMID:25574937

  15. An integrated backscatter ultrasound technique for the detection of coronary and carotid atherosclerotic lesions.

    PubMed

    Kawasaki, Masanori

    2015-01-07

    The instability of carotid and coronary plaques has been reported to be associated with acute coronary syndrome, strokes and other cerebrovascular events. Therefore, recognition of the tissue characteristics of carotid and coronary plaques is important to understand and prevent coronary and cerebral artery disease. Recently, an ultrasound integrated backscatter (IB) technique has been developed. The ultrasound IB power ratio is a function of the difference in acoustic characteristic impedance between the medium and target tissue, and the acoustic characteristic impedance is determined by the density of tissue multiplied by the speed of sound. This concept allows for tissue characterization of carotid and coronary plaques for risk stratification of patients with coronary and cerebral artery disease. Two- and three-dimensional IB color-coded maps for the evaluation of tissue components consist of four major components: fibrous, dense fibrosis, lipid pool and calcification. Although several ultrasound techniques using special mathematical algorithms have been reported, a growing body of literature has shown the reliability and usefulness of the IB technique for the tissue characterization of carotid and coronary plaques. This review summarizes concepts, experimental procedures, image reliability and the application of the IB technique. Furthermore, the IB technique is compared with other techniques.

  16. The measurement of ultrasound backscattering from cell pellet biophantoms and tumors ex vivo

    PubMed Central

    Han, Aiguo; Abuhabsah, Rami; Miller, Rita J.; Sarwate, Sandhya; O'Brien, William D.

    2013-01-01

    Simple scattering media fit scattering model theories much better than more complex scattering media. Tissue is much more complex as an acoustic scattering media and to date there has not been an adequate scattering model that fits it well. Previous studies evaluated the scattering characteristics of simple media (grouping of cells at various number densities) and fit them to the concentric spheres scattering model theory. This study is to increase the complexity of the media to provide insight into the acoustic scattering characteristics of tissue, and specifically two tumor types. Complementing the data from the tumors is 100% volume fraction cell pellets of the same cell lines. Cell pellets and ex vivo tumors are scanned using high-frequency single-element transducers (9–105 MHz), and the attenuation and backscatter coefficient (BSC) are estimated. BSC comparisons are made between cell pellets and tumors. The results show that the 4T1 (ATCC #CRL-2539) cell pellets and tumors have similar BSC characteristics, whereas the MAT (ATCC #CRL-1666) cell pellets and tumors have significantly different BSC characteristics. Factors that yield such differences are explored. Also, the fluid-filled sphere and the concentric spheres models are evaluated against the BSC characteristics, demonstrating that further work is required. PMID:23862841

  17. A test-bed for Langmuir wave turbulence modeling of stimulated Raman backscatter

    SciTech Connect

    Rose, H.A.

    1999-02-01

    Stimulated Raman backscatter (SRS) may incorporate several, qualitatively different regimes of Langmuir wave dynamics, as it grows convectively in space. These typically include a strictly linear regime at the far end of the plasma from the laser, where SRS comes up from thermal Langmuir wave fluctuations; which may progress to a regime where the primary SRS daughter Langmuir wave is unstable to the Langmuir wave decay instability (LDI); and perhaps to a regime of strong Langmuir wave turbulence (SLT). The accurate description of the spatial transition between these regimes, which may involve large Langmuir wave correlation lengths, is a great challenge for turbulence modeling. In this paper a highly idealized model of SRS in periodic geometry is introduced which allows for the presence of a unique Langmuir wave regime for a given set of physical parameters, and therefore presents the minimal challenge for a turbulence model. One- and two-dimensional simulations of this SRS model, which allows for LDI and SLT as described by Zakharov{close_quote}s model of nonlinear Langmuir wave dynamics, are compared with the predictions of a recently introduced turbulence model, and quantitative agreement is obtained, without the use of any {ital ad hoc} parameters, for the SRS reflectivity and correlation length, and Langmuir and acoustic wave energy densities, over an order of magnitude variation of SRS growth rate and ion acoustic damping rate. {copyright} {ital 1999 American Institute of Physics.}

  18. Temporal and spatial variability of ADCP backscatter on a continental slope

    NASA Astrophysics Data System (ADS)

    Sindlinger, Laurie R.; Biggs, Douglas C.; DiMarco, Steven F.

    2005-01-01

    Previous research has shown that acoustic volume backscatter intensity (ABI) from an acoustic Doppler current profiler (ADCP) can be a proxy for zooplankton and micronekton biomass over time or space. As part of NOAA's Sperm Whale and Acoustic Monitoring Program (SWAMP) and a follow-on ichthyoplankton survey (SEAMAP), a ship-mounted 300-kHz broadband ADCP collected current velocity and ABI data from July to September 2001 in the northeast Gulf of Mexico. The present study sought to compare/contrast the variability in ABI both spatially and temporally using the data obtained from the SWAMP and SEAMAP cruises. The ADCP data were averaged over 2 min and 4 m vertical bins from 16 to 56 m below sea surface. Usually, ABI in this epipelagic realm averaged 3 dB higher at night than during the day because of diel vertical migration of zooplankton and micronekton into these near surface waters, while in a region having cyclonic circulation along the continental margin of the northeast Gulf, ABI averaged 6 dB higher than in an anticyclonic warm filament there. Wet displacement volumes (WDV) were measured using Bongo net tows to estimate that a 6 dB increase in ABI was equivalent to an increase from 9 to 10.5 ml WDV of plankton+micronekton per 100 m 3. Sperm whale abundance has been shown to be positively correlated with regions of locally high ABI, and sperm whale sightings during SWAMP were also compared to our ABI measurements. Spectral and Empirical Orthogonal Function analyses were performed on subsets of the ABI data for which 10-14 day time series were available and showed 2-3 day periodicity near-surface, corresponding to spatial scales of 10 1-10 2 km. During summer 2001, the mesoscale circulation along the subtropical continental margin in the northeastern Gulf was found to be the principal forcing factor for low frequency ABI variation. Increased backscatter observations are also correlated with offshore flow from the continental margin to the deep ocean

  19. Ab Interno Trabeculectomy

    PubMed Central

    Pantcheva, Mina B.; Kahook, Malik Y.

    2010-01-01

    Anterior chamber drainage angle surgery, namely trabeculotomy and goniotomy, has been commonly utilized in children for many years. Its’ reported success has ranged between 68% and 100% in infants and young children with congenital glaucoma. However, the long-term success of these procedures has been limited in adults presumably due to the formation of anterior synechiae (AS) in the postoperative phase. Recently, ab interno trabeculectomy with the Trabectome™ has emerged as a novel surgical approach to effectively and selectively remove and ablate the trabecular meshwork and the inner wall of the Schlemm’s canal in an attempt to avoid AS formation or other forms of wound healing with resultant closure of the cleft. This procedure seems to have an appealing safety profile with respect to early hypotony or infection if compared to trabeculectomy or glaucoma drainage device implantation. This might be advantageous in some of the impoverish regions of the Middle East and Africa where patients experience difficulties keeping up with their postoperative visits. It is important to note that no randomized trial comparing the Trabectome to other glaucoma procedures appears to have been published to date. Trabectome surgery is not a panacea, however, and it is associated with early postoperative intraocular pressure spikes that may require additional glaucoma surgery as well as a high incidence of hyphema. Reported results show that postoperative intraocular pressure (IOP) remains, at best, in the mid-teen range making it undesirable in patients with low-target IOP goals. A major advantage of Trabectome surgery is that it does not preclude further glaucoma surgery involving the conjunctiva, such as a trabeculectomy or drainage device implantation. As prospective randomized long-term clinical data become available, we will be better positioned to elucidate the exact role of this technique in the glaucoma surgical armamentarium. PMID:21180426

  20. Criteria of backscattering in chiral one-way photonic crystals

    NASA Astrophysics Data System (ADS)

    Cheng, Pi-Ju; Chang, Shu-Wei

    2016-03-01

    Optical isolators are important devices in photonic circuits. To reduce the unwanted reflection in a robust manner, several setups have been realized using nonreciprocal schemes. In this study, we show that the propagating modes in a strongly-guided chiral photonic crystal (no breaking of the reciprocity) are not backscattering-immune even though they are indeed insensitive to many types of scatters. Without the protection from the nonreciprocity, the backscattering occurs under certain circumstances. We present a perturbative method to calculate the backscattering of chiral photonic crystals in the presence of chiral/achiral scatters. The model is, essentially, a simplified analogy to the first-order Born approximation. Under reasonable assumptions based on the behaviors of chiral photonic modes, we obtained the expression of reflection coefficients which provides criteria for the prominent backscattering in such chiral structures. Numerical examinations using the finite-element method were also performed and the results agree well with the theoretical prediction. From both our theory and numerical calculations, we find that the amount of backscattering critically depends on the symmetry of scatter cross sections. Strong reflection takes place when the azimuthal Fourier components of scatter cross sections have an order l of 2. Chiral scatters without these Fourier components would not efficiently reflect the chiral photonic modes. In addition, for these chiral propagating modes, disturbances at the most significant parts of field profiles do not necessarily result in the most effective backscattering. The observation also reveals what types of scatters or defects should be avoided in one-way applications of chiral structures in order to minimize the backscattering.

  1. Using ultrasound backscattering signals and Nakagami statistical distribution to assess regional cataract hardness.

    PubMed

    Caixinha, Miguel; Jesus, Danilo A; Velte, Elena; Santos, Mário J; Santos, Jaime B

    2014-12-01

    This study aims to analyze the protein aggregates spatial distribution for different cataract degrees, and correlate this information with the lens acoustical parameters and by this way, assess the cataract regional hardness. Different cataract degrees were induced ex vivo in porcine lenses. A 25 MHz ultrasonic transducer was used to obtain the acoustical parameters (velocity, attenuation, and backscattering signals). B-scan and Nakagami images were constructed. Also, lenses with different cataract degrees were sliced in two regions (nucleus and cortex), for fibers and collagen detection. A significant increase with cataract formation was found for the velocity, attenuation, and brightness intensity of the B-scan images and Nakagami m parameter ( ). The acoustical parameters showed a good to moderate correlation with the m parameter for the different stages of cataract formation. A strong correlation was found between the protein aggregates in the cortex and the m parameter. Lenses without cataract are characterized using a classification and regression tree, by a mean brightness intensity ≤0.351, a variance of the B-scan brightness intensity ≤0.070, a velocity ≤1625 m/s, and an attenuation ≤0.415 dB/mm·MHz (sensitivity: 100% and specificity: 72.6%). To characterize different cataract degrees, the m parameter should be considered. Initial stages of cataract are characterized by a mean brightness intensity >0.351 and a variance of the m parameter >0.110. Advanced stages of cataract are characterized by a mean brightness intensity >0.351, a variance of the m parameter ≤0.110, and a mean m parameter >0.374. For initial and advanced stages of cataract, a sensitivity of 78.4% and a specificity of 86.5% are obtained.

  2. Acoustic source for generating an acoustic beam

    DOEpatents

    Vu, Cung Khac; Sinha, Dipen N.; Pantea, Cristian

    2016-05-31

    An acoustic source for generating an acoustic beam includes a housing; a plurality of spaced apart piezo-electric layers disposed within the housing; and a non-linear medium filling between the plurality of layers. Each of the plurality of piezoelectric layers is configured to generate an acoustic wave. The non-linear medium and the plurality of piezo-electric material layers have a matching impedance so as to enhance a transmission of the acoustic wave generated by each of plurality of layers through the remaining plurality of layers.

  3. Coherent Backscattering in Los Albedo Media

    NASA Astrophysics Data System (ADS)

    Nelson, R. M.; Hapke, B. W.; Hale, A. S.; Smythe, W. D.; Piatek, J.

    2002-09-01

    The opposition effect [1] observed in phase curves of materials in the lab and on planetary surfaces is attributed to two processes: 'shadow hiding opposition effect' (SHOE) and 'coherent backscattering opposition effect' (CBOE) [2,3,4]. The relative contributions of SHOE and CBOE are studied by measuring reflectance phase curves in circularly polarized light. If single scattering predominates, the circular polarization ratio (CPR) decreases with decreasing phase angle. If multiple scattering predominates, the CPR strongly increases. We observed this increase in CPR in highly reflective media [5,6,7]. In low reflectance media most of the returned signal is singly scattered and CPR is not expected to sharply increase. We have found that most such materials indeed exhibit only a slight CPR increase. However, lunar soils show a strong CPR increase [8]. Recently we encountered another interesting counter example in Boron Carbide-a material with albedo even lower than the Moon's. We find a significant CPR increase, a result inconsistent with the conventional interpretation of CBOE [8]. This suggests that albedo alone is not the principal regulator of CBOE. This CBOE may be due to multiple scattering within individual particles [10]. Unusual particle shapes may facilitate this process. Understanding this behavior contributes to the development of models that can retrieve textural properties from remote sensing data. Work performed at JPL/PITT under NASA PG&G grants. 1.Geherels, T. Astrophys. J, 123, 331-338, 1956. 2. Hapke, B. Icarus, 67, 246-280, 1986. 3. Shkuratov, Yu. SA-A.J., 27, 581-583, 1983. 4. Hapke, B. Icarus, 88, 407-417, 1990. 5. Nelson, R., et al. Icarus 131, 223-230, 1998. 6. Nelson, R., et al Icarus, 147, 545-558, 2000. 7. Nelson, R., et al. Planet. Space Sci, 2002. 8. Hapke B. et al. Science, 260, 509-511. 9. Mishchenko, M.I. Earth, Moon and Planets, 58, 127-144, 1992. 10. Hapke, B. Icarus, 157, 534-537, 2002

  4. Canonical Acoustics and Its Application to Surface Acoustic Wave on Acoustic Metamaterials

    NASA Astrophysics Data System (ADS)

    Shen, Jian Qi

    2016-08-01

    In a conventional formalism of acoustics, acoustic pressure p and velocity field u are used for characterizing acoustic waves propagating inside elastic/acoustic materials. We shall treat some fundamental problems relevant to acoustic wave propagation alternatively by using canonical acoustics (a more concise and compact formalism of acoustic dynamics), in which an acoustic scalar potential and an acoustic vector potential (Φ ,V), instead of the conventional acoustic field quantities such as acoustic pressure and velocity field (p,u) for characterizing acoustic waves, have been defined as the fundamental variables. The canonical formalism of the acoustic energy-momentum tensor is derived in terms of the acoustic potentials. Both the acoustic Hamiltonian density and the acoustic Lagrangian density have been defined, and based on this formulation, the acoustic wave quantization in a fluid is also developed. Such a formalism of acoustic potentials is employed to the problem of negative-mass-density assisted surface acoustic wave that is a highly localized surface bound state (an eigenstate of the acoustic wave equations). Since such a surface acoustic wave can be strongly confined to an interface between an acoustic metamaterial (e.g., fluid-solid composite structures with a negative dynamical mass density) and an ordinary material (with a positive mass density), it will give rise to an effect of acoustic field enhancement on the acoustic interface, and would have potential applications in acoustic device design for acoustic wave control.

  5. What Is an Acoustic Neuroma

    MedlinePlus

    ... ANAUSA.org Connect with us! What is an Acoustic Neuroma? Each heading slides to reveal information. Important ... Acoustic Neuroma Important Points To Know About an Acoustic Neuroma An acoustic neuroma, also called a vestibular ...

  6. Observations regarding coarse sediment classification based on multi-beam echo-sounder's backscatter strength and depth residuals in Dutch rivers.

    PubMed

    Eleftherakis, Dimitrios; Snellen, Mirjam; Amiri-Simkooei, AliReza; Simons, Dick G; Siemes, Kerstin

    2014-06-01

    This contribution investigates the behavior of two important riverbed sediment classifiers, derived from multi-beam echo-sounder (MBES)-operating at 300 kHz-data, in very coarse sediment environments. These are the backscatter strength and the depth residuals. Four MBES data sets collected at different parts of rivers in the Netherlands are employed. From previous research the backscatter strength was found to increase for increasing mean grain sizes. Depth residuals, however, are often found to have lower values for coarser sediments. Investigation of the four data sets indicates that these statements are valid only for moderately coarse sediment such as sand. For very coarse sediments (e.g., coarse gravel) the backscatter strength is found to decrease and the depth residuals increase for increasing mean grain sizes. This is observed when the sediment mean grain size becomes significantly larger than the acoustic wavelength of the MBES (5 mm). Knowledge regarding this behavior is of high importance when using backscatter strength and depth residuals for sediment classification purposes as the reverse in behavior can induce ambiguity in the classification.

  7. Acoustic measuring techniques for suspended sediment

    NASA Astrophysics Data System (ADS)

    Gruber, P.; Felix, D.; Storti, G.; Lattuada, M.; Fleckenstein, P.; Deschwanden, F.

    2016-11-01

    Acoustic signals can be used in various ways for suspended sediment monitoring. One possibility which lends itself particularly well in the context of hydropower plants (HPPs), is to use installations for acoustic discharge measurement (ADM). Such installations already exist at waterways of many HPPs. Similar to certain turbidimeters, the attenuation of the forward scattered signal travelling through the water-sediment mixture is correlated with suspended sediment concentration (SSC). This correlation can be based on reference SSCs, e.g. from gravimetric analyses of bottle samples. Without the need of additional sensors and practically maintenance-free, this method is used successfully in the HPP Fieschertal to warn the HPP operator of high SSC to prevent excessive turbine abrasion. Acoustic methods and systems that allow for estimating both SSC and particle size distribution (PSD) are under development. The simultaneous determination of SSC and PSD is not possible using a single frequency. Therefore, multi-frequency approaches are investigated for generally scattered signals. When backscattered signals are used, a stronger frequency dependency can be exploited. However, the reliable simultaneous determination of particle size (and distribution) and concentration is still a major challenge due to a low signal-to-noise ratio and an ill- posed problem of estimating concentration and size from recorded signals. The optimal setup configuration (angles, frequencies) for such a system is not unique and further investigations are recommended.

  8. Autonomous Biological System (ABS) experiments.

    PubMed

    MacCallum, T K; Anderson, G A; Poynter, J E; Stodieck, L S; Klaus, D M

    1998-12-01

    Three space flight experiments have been conducted to test and demonstrate the use of a passively controlled, materially closed, bioregenerative life support system in space. The Autonomous Biological System (ABS) provides an experimental environment for long term growth and breeding of aquatic plants and animals. The ABS is completely materially closed, isolated from human life support systems and cabin atmosphere contaminants, and requires little need for astronaut intervention. Testing of the ABS marked several firsts: the first aquatic angiosperms to be grown in space; the first higher organisms (aquatic invertebrate animals) to complete their life cycles in space; the first completely bioregenerative life support system in space; and, among the first gravitational ecology experiments. As an introduction this paper describes the ABS, its flight performance, advantages and disadvantages.

  9. Modeling multi-frequency diurnal backscatter from a walnut orchard

    NASA Technical Reports Server (NTRS)

    Mcdonald, Kyle C.; Dobson, Myron C.; Ulaby, Fawwaz T.

    1991-01-01

    The Michigan Microwave Canopy Scattering Model (MIMICS) is used to model scatterometer data that were obtained during the August 1987 EOS (Earth Observing System) synergism study. During this experiment, truck-based scatterometers were used to measure radar backscatter from a walnut orchard in Fresno County, California. Multipolarized L- and X-band data were recorded for orchard plots for which dielectric and evapotranspiration characteristics were monitored. MIMICS is used to model a multiangle data set in which a single orchard plot was observed at varying impedance angles and a series of diurnal measurements in which backscatter from this same plot was measured continuously over several 24-h periods. MIMICS accounts for variations in canopy backscatter driven by changes in canopy state that occur diurnally as well as on longer time scales. L-band backscatter is dependent not only on properties of the vegetation but also on properties of the underlying soil surface. The behavior of the X-band backscatter is dominated by properties of the tree crowns.

  10. Symptoms of Acoustic Neuroma

    MedlinePlus

    ... Watch and Wait Radiation Microsurgery Acoustic Neuroma Decision Tree Questions for Your Physician Questions to Ask Yourself ... Watch and Wait Radiation Microsurgery Acoustic Neuroma Decision Tree Questions for Your Physician Questions to Ask Yourself ...

  11. NPL closes acoustics department

    NASA Astrophysics Data System (ADS)

    Extance, Andy

    2016-11-01

    The UK's National Physical Laboratory (NPL) has withdrawn funding for its acoustics, polymer and thermoelectrics groups, triggering concern among airborne acoustics specialists that the move could undermine the country's noise-management policies.

  12. Identifying the Acoustic Neuroma

    MedlinePlus

    ... Watch and Wait Radiation Microsurgery Acoustic Neuroma Decision Tree Questions for Your Physician Questions to Ask Yourself ... Watch and Wait Radiation Microsurgery Acoustic Neuroma Decision Tree Questions for Your Physician Questions to Ask Yourself ...

  13. Computer Modeling of Direct Path, Backscattered Bottom Reverberations for the Acoustic Reverberation Special Research Program (ARSRP)

    DTIC Science & Technology

    1990-10-01

    34 .. .:. ..... . . ... H3Od KV38 F-0 (cc .ILI 0 L) C7C) LS..i~i *Q p a 5 -- ,s g v -J -J C)c Z1 E~ KV3 K’o - S.- ’ " , ’ , ~~.. .... ..... . ......., , -inn *Q o c "<g - aa...a -IC) | *."I I I I!-) Sa ao <o o3~ INY3U U) CQC CC) -C0 r- 0 - CD C> CC CC)) ZJ3M~d KV3 ct: Loo 00 00 CE~ ~ ~ ..... 43~ NV3 C’,) I 0 I

  14. Verification and Validation Study for Extraction of Ocean Bottom Acoustic Backscattering Strengths

    DTIC Science & Technology

    2008-07-28

    kernel” of SABLE is the ability to use raytracing and beampattern information to calculate the latitude/longitude cell (or “grid cell”) of the...series. In the general case, an appropriate time interval is selected for computation of the mean reverberation level and the raytrace information is...Transmission loss (TL): NRL and ARL:UT use different models for transmission loss. NRL uses raytrace code written in the 1980’s by R. Pitre [8], while

  15. Investigation of High-Frequency Acoustic Backscattering Model Parameters: Environmental Data from the Arafura Sea

    DTIC Science & Technology

    1989-02-01

    gorgonaceans and pennatulaceans), stalked sponges, stoloniferous bryozoa , and anemones (actiniarians and ceriantharians) are visible. Figure 9 shows...shape ofthesoft-bodied organisms themselves. Algae, bryozoa , and soft corals in particular need a hard substrate to attach the holdfasts: gravel-sized

  16. Acoustic emission frequency discrimination

    NASA Technical Reports Server (NTRS)

    Sugg, Frank E. (Inventor); Graham, Lloyd J. (Inventor)

    1988-01-01

    In acoustic emission nondestructive testing, broadband frequency noise is distinguished from narrow banded acoustic emission signals, since the latter are valid events indicative of structural flaws in the material being examined. This is accomplished by separating out those signals which contain frequency components both within and beyond (either above or below) the range of valid acoustic emission events. Application to acoustic emission monitoring during nondestructive bond verification and proof loading of undensified tiles on the Space Shuttle Orbiter is considered.

  17. Deep Water Ocean Acoustics

    DTIC Science & Technology

    2015-07-17

    under-ice scattering , bathymetric diffraction and the application of the ocean acoustic Parabolic Equation to infrasound. 2. Tasks a. Task 1...QSR-14C0172-Ocean Acoustics -063015 Figure 10. Estimated reflection coefficient as a function of frequency by taking the difference of downgoing and...OASIS, INC. 1 Report No. QSR-14C0172-Ocean Acoustics -063015 Quarterly Progress Report Technical and Financial Deep Water Ocean Acoustics

  18. Deep Water Ocean Acoustics

    DTIC Science & Technology

    2015-10-19

    OASIS, INC. 1 Report No. QSR-14C0172-Ocean Acoustics-093015 Quarterly Progress Report Technical and Financial Deep Water Ocean Acoustics...number. 1. REPORT DATE OCT 2015 2. REPORT TYPE 3. DATES COVERED 01-07-2015 to 30-09-2015 4. TITLE AND SUBTITLE Deep Water Ocean Acoustics...understanding of the impact of the ocean and seafloor environmental variability on deep- water (long-range) ocean acoustic propagation and to develop

  19. Shallow Water Acoustics Studies

    DTIC Science & Technology

    2015-09-30

    1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Shallow Water Acoustics Studies James F. Lynch MS #12...N00014-14-1-0040 http://acoustics.whoi.edu/sw06/ LONG TERM GOALS The long term goals of our shallow water acoustics work are to: 1) understand the...nature of low frequency (10-1500 Hz) acoustic propagation, scattering and noise in shallow water when strong oceanic variability is present in the

  20. Comment on "Anomalous wave propagation in a one-dimensional acoustic metamaterial having simultaneously negative mass density and Young's modulus" [J. Acoust. Soc. Am. 132, 2887-2895 (2012)].

    PubMed

    Marston, Philip L

    2014-03-01

    The phase and group velocities of elastic guided waves are important in the physical interpretation of high frequency scattering by fluid-loaded elastic shells. Outside the context of scattering, those properties are also important for understanding the energy flow in acoustic metamaterials. In a recent investigation of acoustic metamaterials exhibiting anomalous wave propagation [J. Acoust. Soc. Am. 132, 2887-2895 (2012)] criticism of negative group velocity terminology was generalized to elastic waves guided on ordinary materials. Some context and justification for retaining the identification of negative group velocities associated with a type of backscattering enhancement for shells are explained here. The phase evolution direction is determined by the boundary conditions.

  1. Coding Acoustic Metasurfaces.

    PubMed

    Xie, Boyang; Tang, Kun; Cheng, Hua; Liu, Zhengyou; Chen, Shuqi; Tian, Jianguo

    2017-02-01

    Coding acoustic metasurfaces can combine simple logical bits to acquire sophisticated functions in wave control. The acoustic logical bits can achieve a phase difference of exactly π and a perfect match of the amplitudes for the transmitted waves. By programming the coding sequences, acoustic metasurfaces with various functions, including creating peculiar antenna patterns and waves focusing, have been demonstrated.

  2. Tutorial on architectural acoustics

    NASA Astrophysics Data System (ADS)

    Shaw, Neil; Talaske, Rick; Bistafa, Sylvio

    2002-11-01

    This tutorial is intended to provide an overview of current knowledge and practice in architectural acoustics. Topics covered will include basic concepts and history, acoustics of small rooms (small rooms for speech such as classrooms and meeting rooms, music studios, small critical listening spaces such as home theatres) and the acoustics of large rooms (larger assembly halls, auditoria, and performance halls).

  3. Laser light backscatter from intermediate and high Z plasmas

    NASA Astrophysics Data System (ADS)

    Berger, R. L.; Constantin, C.; Divol, L.; Meezan, N.; Froula, D. H.; Glenzer, S. H.; Suter, L. J.; Niemann, C.

    2006-09-01

    In experiments at the Omega Laser Facility [J. M. Soures et al., Fusion Technol. 30, 492 (1996)], stimulated Brillouin backscatter (SBS) from gasbags filled with krypton and xenon gases was ten times lower than from CO2-filled gasbags with similar electron densities. The SBS backscatter was a 1%-5% for both 527 and 351nm interaction beams at an intensity of ˜1015W /cm2. The SRS backscatter was less than 1%. The 351nm interaction beam is below the threshold for filamentation and the SBS occurs in the density plateau between the blast waves. Inverse bremsstrahlung absorption of the incident and SBS light account for the lower reflectivity from krypton than from CO2. The 527nm interaction beam filaments in the blowoff plasma before the beam propagates through the blast wave, where it is strongly absorbed. Thus, most of the 527nm SBS occurs in the flowing plasma outside the blast waves.

  4. Calculations of radar backscattering coefficient of vegetation-covered soils

    NASA Technical Reports Server (NTRS)

    Mo, T.; Schmugge, T. J.; Jackson, T. J. (Principal Investigator)

    1983-01-01

    A model for simulating the measured backscattering coefficient of vegetation-covered soil surfaces includes both coherent and incoherent components of the backscattered radar pulses from a rough sil surface. The effect of vegetation canopy scattering is also incorporated into the model by making the radar pulse subject to two-way attenuation and volume scattering when it passes through the vegetation layer. Model results agree well with the measured angular distributions of the radar backscattering coefficient for HH polarization at the 1.6 GHz and 4.75 GHz frequencies over grass-covered fields. It was found that the coherent scattering component is very important at angles near nadir, while the vegetation volume scattering is dominant at incident angles 30 degrees.

  5. Effects of optical backscattering on silicon photonic hybrid laser performance

    NASA Astrophysics Data System (ADS)

    Pacradouni, V.; Klein, J.; Pond, J.

    2016-04-01

    We present numerical results on the effect of backscattering at the junctions of double bus ring resonators in a Vernier ring hybrid laser design. The structure is comprised off a pair of III-V gain media evanescently coupled to a silicon on insulator racetrack comprised of a pair of double bus ring resonators coupled together through straight and flared waveguide sections. We show how the small backscattering at the ring resonator junctions has the effect of splitting and shifting the resonances off the clockwise and counter clockwise propagating modes thereby modifying the feedback spectrum from the ideal case. We then simulate results such as light current (LI) curves, relative intensity noise (RIN) and laser spectrum, and compare the laser performance including backscattering effects with the ideal case.

  6. Backscatter and attenuation properties of mammalian brain tissues

    NASA Astrophysics Data System (ADS)

    Wijekularatne, Pushpani Vihara

    Traumatic Brain Injury (TBI) is a common category of brain injuries, which contributes to a substantial number of deaths and permanent disability all over the world. Ultrasound technology plays a major role in tissue characterization due to its low cost and portability that could be used to bridge a wide gap in the TBI diagnostic process. This research addresses the ultrasonic properties of mammalian brain tissues focusing on backscatter and attenuation. Orientation dependence and spatial averaging of data were analyzed using the same method resulting from insertion of tissue sample between a transducer and a reference reflector. Apparent backscatter transfer function (ABTF) at 1 to 10 MHz, attenuation coefficient and backscatter coefficient (BSC) at 1 to 5 MHz frequency ranges were measured on ovine brain tissue samples. The resulting ABTF was a monotonically decreasing function of frequency and the attenuation coefficient and BSC generally were increasing functions of frequency, results consistent with other soft tissues such as liver, blood and heart.

  7. Investigation of phonon coherence and backscattering using silicon nanomeshes

    NASA Astrophysics Data System (ADS)

    Lee, Jaeho; Lee, Woochul; Wehmeyer, Geoff; Dhuey, Scott; Olynick, Deirdre L.; Cabrini, Stefano; Dames, Chris; Urban, Jeffrey J.; Yang, Peidong

    2017-01-01

    Phonons can display both wave-like and particle-like behaviour during thermal transport. While thermal transport in silicon nanomeshes has been previously interpreted by phonon wave effects due to interference with periodic structures, as well as phonon particle effects including backscattering, the dominant mechanism responsible for thermal conductivity reductions below classical predictions still remains unclear. Here we isolate the wave-related coherence effects by comparing periodic and aperiodic nanomeshes, and quantify the backscattering effect by comparing variable-pitch nanomeshes. We measure identical (within 6% uncertainty) thermal conductivities for periodic and aperiodic nanomeshes of the same average pitch, and reduced thermal conductivities for nanomeshes with smaller pitches. Ray tracing simulations support the measurement results. We conclude phonon coherence is unimportant for thermal transport in silicon nanomeshes with periodicities of 100 nm and higher and temperatures above 14 K, and phonon backscattering, as manifested in the classical size effect, is responsible for the thermal conductivity reduction.

  8. Measurement of Bubble Size Distribution Based on Acoustic Propagation in Bubbly Medium

    NASA Astrophysics Data System (ADS)

    Wu, Xiongjun; Hsiao, Chao-Tsung; Choi, Jin-Keun; Chahine, Georges

    2013-03-01

    Acoustic properties are strongly affected by bubble size distribution in a bubbly medium. Measurement of the acoustic transmission becomes increasingly difficulty as the void fraction of the bubbly medium increases due to strong attenuation, while acoustic reflection can be measured more easily with increasing void fraction. The ABS ACOUSTIC BUBBLE SPECTROMETER®\\copyright, an instrument for bubble size measurement that is under development tries to take full advantage of the properties of acoustic propagation in bubbly media to extract bubble size distribution. Properties of both acoustic transmission and reflection in the bubbly medium from a range of short single-frequency bursts of acoustic waves at different frequencies are measured in an effort to deduce the bubble size distribution. With the combination of both acoustic transmission and reflection, assisted with validations from photography, the ABS ACOUSTIC BUBBLE SPECTROMETER®\\copyright has the potential to measure bubble size distributions in a wider void fraction range. This work was sponsored by Department of Energy SBIR program

  9. Bruce Thompson: Adventures and advances in ultrasonic backscatter

    NASA Astrophysics Data System (ADS)

    Margetan, Frank J.

    2012-05-01

    Over the course of his professional career Dr. R. Bruce Thompson published several hundred articles on non-destructive evaluation, the majority dealing with topics in ultrasonics. One longtime research interest of Dr. Thompson, with applications both to microstructure characterization and defect detection, was backscattered grain noise in metals. Over a 20 year period he led a revolving team of staff members and graduate students investigating various aspects of ultrasonic backscatter. As a member of that team I had the privilege of working along side Dr. Thompson for many years, serving as a sort of Dr. Watson to Bruce's Sherlock Holmes. This article discusses Dr. Thompson's general approaches to modeling backscatter, the research topics he chose to explore to systematically elucidate a better understanding of the phenomena, and the many contributions to the field achieved under his leadership. The backscatter work began in earnest around 1990, motivated by a need to improve inspections of aircraft engine components. At that time Dr. Thompson launched two research efforts. The first led to the heuristic Independent Scatterer Model which could be used to estimate the average grain noise level that would be seen in any given ultrasonic inspection. There the contribution from the microstructure was contained in a measureable parameter known as the Figure-of-Merit or FOM. The second research effort, spearheaded by Dr. Jim Rose, led to a formal relationship between FOM and details of the metal microstructure. The combination of the Independent Scattering Model and Rose's formalism provided a powerful tool for investigating backscatter in metals. In this article model developments are briefly reviewed and several illustrative applications are discussed. These include: the determination of grain size and shape from ultrasonic backscatter; grain noise variability in engine-titanium billets and forgings; and the design of ultrasonic inspection systems to improve defect

  10. Attenuation Estimation and Temperature Imaging Using Backscatter for Extracorporeal HIFU Treatment Planning

    NASA Astrophysics Data System (ADS)

    Civale, John; Bamber, Jeff; Miller, Naomi; Rivens, Ian; ter Haar, Gail

    2007-05-01

    For HIFU to be widely applicable in the clinic, problems relating to treatment planning, delivery and monitoring need to be resolved. The characterisation of the acoustic and thermal properties of specific tissues is an important pre-requisite to determining the optimal exposure parameters for individual treatments. We describe a preliminary evaluation of two methods that may be of use in deriving such planning information prior to HIFU. Both methods have been implemented on a diagnostic ultrasound scanner. One is backscatter attenuation estimation (BAE), which uses pulse-echo data and an axial beam translation substitution method to estimate the average attenuation coefficient of tissue overlying the region to be treated. The second method is backscatter temperature imaging (BTI) applied to a non-lesioning test exposure, which is normally used to determine the focal position but here the observed peak temperature rise is employed to provide an estimate of all case-specific losses involved in delivering a dose of thermal energy. HIFU lesioning experiments were performed in ex vivo bovine liver tissue, and used to test the ability of BAE and BTI to provide accurate information for adjusting the HIFU power so as to compensate for varying ultrasonic attenuation by overlying tissues (mimicked by gels with different attenuation properties). HIFU-induced lesions were made according to two types of exposure regime, (a) without regard for the differing attenuation coefficients of gels placed between the HIFU transducer and the tissue to be treated, and (b) after adjusting the HIFU drive power according to corrections derived from BAE and BTI measurements. Both correction methods were found to improve lesion size reproducibility, as measured from cut lesioned tissue specimens, although BTI performed better than BAE. The paper discusses likely reasons for this, as well as problems to be overcome if either method is to be clinically useful.

  11. Broadband enhanced backscattering spectroscopy of strongly scattering media.

    PubMed

    Muskens, O L; Lagendijk, A

    2008-01-21

    We report on a new experimental method for enhanced backscattering spectroscopy (EBS) of strongly scattering media over a bandwidth from 530-1000 nm. The instrument consists of a supercontinuum light source and an angle-dependent detection system using a fiber-coupled grating spectrometer. Using a combination of two setups, the backscattered intensity is obtained over a large angular range and using circularly polarized light. We present broadband EBS of a TiO(2) powder and of a strongly scattering porous GaP layer. In combination with theoretical model fits, the EBS system yields the optical transport mean free path over the available spectral window.

  12. Light backscattering efficiency and related properties of some phytoplankters

    NASA Astrophysics Data System (ADS)

    Ahn, Yu-Hwan; Bricaud, Annick; Morel, André

    1992-11-01

    By using a set-up that combines an integrating sphere with a spectroradiometer LI-1800 UW, the backscattering properties of nine different phytoplankters grown in culture have been determined experimentally for the wavelengths domain ν = 400 up to 850 nm. Simultaneously, the absorption and attenuation properties, as well as the size distribution function, have been measured. This set of measurements allowed the spectral values of refractive index, and subsequently the volume scattering functions (VSF) of the cells, to be derived, by operating a scattering model previously developed for spherical and homogeneous cells. The backscattering properties, measured within a restricted angular domain (approximately between 132 and 174°), have been compared to theoretical predictions. Although there appear some discrepancies between experimental and predicted values (probably due to experimental errors as well as deviations of actual cells from computational hypotheses), the overall agreement is good; in particular the observed interspecific variations of backscattering values, as well as the backscattering spectral variation typical of each species, are well accounted for by theory. Using the computed VSF, the measured backscattering properties can be converted (assuming spherical and homogeneous cells) into efficiency factors for backscattering ( overlineQbb) . Thhe spectral behavior of overlineQbb appears to be radically different from that for total scattering overlineQb. For small cells, overlineQ (λ) is practically constant over the spectrum, whereas overlineQb(λ) varies approximately according to a power law (λ -2). As the cell size increases, overlineQbb conversely, becomes increasingly featured, whilst overlineQb becomes spectrally flat. The chlorophyll-specific backscattering coefficients ( b b∗ appear highly variable and span nearly two orders of magnitude. The chlorophyll-specific absorption and scattering coefficients, a ∗ and b ∗, are mainly ruled by

  13. Target reflectance measurements for calibration of lidar atmospheric backscatter data

    NASA Technical Reports Server (NTRS)

    Kavaya, M. J.; Menzies, R. T.; Haner, D. A.; Oppenheim, U. P.; Flamant, P. H.

    1983-01-01

    Wavelength and angular dependence of reflectances and depolarization in the 9-11 micron region are reported for four standard targets: flowers of sulfur, flame-sprayed aluminum, 20-grit sandblasted aluminum, and 400-grit silicon carbon sandpaper. Measurements are presented and compared using a CW CO2 grating-tunable laser in a laboratory backscatter apparatus, an integrating sphere, and a coherent pulsed TEA-CO2 lidar system operating in the 9-11 micron region. Reflectance theory related to the use of hard targets to calibrate lidar atmospheric backscatter data is discussed.

  14. Coherent Effects in Microwave Backscattering Models for Forest Canopies

    NASA Technical Reports Server (NTRS)

    Saatchi, Sasan; McDonald, Kyle

    1995-01-01

    In modeling forest canopies, several scattering mechanisms are taken into account: 1) volume scattering, 2) surface-volume interaction, and 3) surface scattering from forest floor. Depending on the structural and dielectric characteristics of forest canopies, the relative contribution of each mechanism in the total backscatter signal of an imaging radar can vary. In this paper, two commonly used first order discrete scattering models, Distorted Born Approximation (DBA) and Radiative Transfer (RT) are used to simulate the backscattered power received by polarimetric radars at P-, L-, and C-bands over coniferous and deciduous forests. The difference between the two models resides on the coherent effect in the surface-volume interaction terms.

  15. Light Backscattering Polarization Patterns from Turbid Media: Theory and Experiment

    NASA Astrophysics Data System (ADS)

    Rakovic, Milun J.; Kattawar, George W.; Mehrubeoglu, Mehrube; Cameron, Brent D.; Wang, Lihong V.; Rastegar, Sohi; Coté, Gerard L.

    1999-05-01

    We present both experimental measurements and Monte-Carlo-based simulations of the diffusely backscattered intensity patterns that arise from illuminating a turbid medium with a polarized laser beam. It is rigorously shown that, because of axial symmetry of the system, only seven elements of the effective backscattering Mueller matrix are independent. A new numerical method that allows simultaneous calculation of all 16 elements of the two-dimensional Mueller matrix is used. To validate our method we compared calculations to measurements from a turbid medium that consisted of polystyrene spheres of different sizes and concentrations in deionized water. The experimental and numerical results are in excellent agreement.

  16. Light backscattering polarization patterns from turbid media: theory and experiment.

    PubMed

    Raković, M J; Kattawar, G W; Mehrubeoğlu, M B; Cameron, B D; Wang, L V; Rastegar, S; Coté, G L

    1999-05-20

    We present both experimental measurements and Monte-Carlo-based simulations of the diffusely backscattered intensity patterns that arise from illuminating a turbid medium with a polarized laser beam. It is rigorously shown that, because of axial symmetry of the system, only seven elements of the effective backscattering Mueller matrix are independent. A new numerical method that allows simultaneous calculation of all 16 elements of the two-dimensional Mueller matrix is used. To validate our method we compared calculations to measurements from a turbid medium that consisted of polystyrene spheres of different sizes and concentrations in deionized water. The experimental and numerical results are in excellent agreement.

  17. Thresholds of Raman backscatter: effects of collisions and Landau damping

    SciTech Connect

    Estabrook, K.; Kruer, W.L.

    1983-11-03

    We present 1.5 dimensional simulations and theory of the threshold of Raman backscatter for a variety of density profiles, background temperatures and collision frequencies, nu/sub ei/. The simulations show Raman backscatter of approx. 4 x 10/sup -4/ at intensities approx. 30 times below the del n threshold which we suggest is due to light scattering off of noise electron plasma waves. The absorption drops significantly and the threshold rises as the Landau damping ..omega../sub i/ and/or nu/sub ei/ approach the growth rate ..gamma../sub 0/. Many experiments are already in the collisional regime.

  18. X-ray backscatter imaging for aerospace applications

    SciTech Connect

    Shedlock, Daniel; Edwards, Talion; Toh, Chin

    2011-06-23

    Scatter x-ray imaging (SXI) is a real time, digital, x-ray backscatter imaging technique that allows radiographs to be taken from one side of an object. This x-ray backscatter imaging technique offers many advantages over conventional transmission radiography that include single-sided access and extremely low radiation fields compared to conventional open source industrial radiography. Examples of some applications include the detection of corrosion, foreign object debris, water intrusion, cracking, impact damage and leak detection in a variety of material such as aluminum, composites, honeycomb structures, and titanium.

  19. Ab initio study of hot electrons in GaAs.

    PubMed

    Bernardi, Marco; Vigil-Fowler, Derek; Ong, Chin Shen; Neaton, Jeffrey B; Louie, Steven G

    2015-04-28

    Hot carrier dynamics critically impacts the performance of electronic, optoelectronic, photovoltaic, and plasmonic devices. Hot carriers lose energy over nanometer lengths and picosecond timescales and thus are challenging to study experimentally, whereas calculations of hot carrier dynamics are cumbersome and dominated by empirical approaches. In this work, we present ab initio calculations of hot electrons in gallium arsenide (GaAs) using density functional theory and many-body perturbation theory. Our computed electron-phonon relaxation times at the onset of the Γ, L, and X valleys are in excellent agreement with ultrafast optical experiments and show that the ultrafast (tens of femtoseconds) hot electron decay times observed experimentally arise from electron-phonon scattering. This result is an important advance to resolve a controversy on hot electron cooling in GaAs. We further find that, contrary to common notions, all optical and acoustic modes contribute substantially to electron-phonon scattering, with a dominant contribution from transverse acoustic modes. This work provides definitive microscopic insight into hot electrons in GaAs and enables accurate ab initio computation of hot carriers in advanced materials.

  20. Ab initio study of hot electrons in GaAs

    PubMed Central

    Bernardi, Marco; Vigil-Fowler, Derek; Ong, Chin Shen; Neaton, Jeffrey B.; Louie, Steven G.

    2015-01-01

    Hot carrier dynamics critically impacts the performance of electronic, optoelectronic, photovoltaic, and plasmonic devices. Hot carriers lose energy over nanometer lengths and picosecond timescales and thus are challenging to study experimentally, whereas calculations of hot carrier dynamics are cumbersome and dominated by empirical approaches. In this work, we present ab initio calculations of hot electrons in gallium arsenide (GaAs) using density functional theory and many-body perturbation theory. Our computed electron–phonon relaxation times at the onset of the Γ, L, and X valleys are in excellent agreement with ultrafast optical experiments and show that the ultrafast (tens of femtoseconds) hot electron decay times observed experimentally arise from electron–phonon scattering. This result is an important advance to resolve a controversy on hot electron cooling in GaAs. We further find that, contrary to common notions, all optical and acoustic modes contribute substantially to electron–phonon scattering, with a dominant contribution from transverse acoustic modes. This work provides definitive microscopic insight into hot electrons in GaAs and enables accurate ab initio computation of hot carriers in advanced materials. PMID:25870287

  1. Ab Initio and Ab Exitu No-Core Shell Model

    SciTech Connect

    Vary, J P; Navratil, P; Gueorguiev, V G; Ormand, W E; Nogga, A; Maris, P; Shirokov, A

    2007-10-02

    We outline two complementary approaches based on the no core shell model (NCSM) and present recent results. In the ab initio approach, nuclear properties are evaluated with two-nucleon (NN) and three-nucleon interactions (TNI) derived within effective field theory (EFT) based on chiral perturbation theory (ChPT). Fitting two available parameters of the TNI generates good descriptions of light nuclei. In a second effort, an ab exitu approach, results are obtained with a realistic NN interaction derived by inverse scattering theory with off-shell properties tuned to fit light nuclei. Both approaches produce good results for observables sensitive to spin-orbit properties.

  2. Indoor acoustic gain design

    NASA Astrophysics Data System (ADS)

    Concha-Abarca, Justo Andres

    2002-11-01

    The design of sound reinforcement systems includes many variables and usually some of these variables are discussed. There are criteria to optimize the performance of the sound reinforcement systems under indoor conditions. The equivalent acoustic distance, the necessary acoustic gain, and the potential acoustic gain are parameters which must be adjusted with respect to the loudspeaker array, electric power and directionality of loudspeakers, the room acoustics conditions, the distance and distribution of the audience, and the type of the original sources. The design and installation of front of the house and monitoring systems have individual criteria. This article is about this criteria and it proposes general considerations for the indoor acoustic gain design.

  3. US Atlantic Margin Methane Plumes Identified From Water Column Backscatter Data Acquired by NOAA Ship Okeanos Explorer

    NASA Astrophysics Data System (ADS)

    Kodis, M.; Skarke, A. D.; Ruppel, C. D.; Weber, T.; Lobecker, E.; Malik, M.

    2013-12-01

    The NOAA Office of Ocean Exploration and Research routinely uses NOAA Ship Okeanos Explorer to collect EM302 (30 kHz) multibeam bathymetric data and water column backscatter imagery. These backscatter data have been used to identify gas plumes associated with seafloor methane seeps as part of previous investigations in the Gulf of Mexico and at Blake Ridge. Here, we use QPS Fledermaus Midwater software to analyze over 200,000 km2 of multibeam data acquired on the continental slope and outer shelf of the US Atlantic margin in 2011, 2012, and 2013. Preliminary application of this analytical methodology in late 2012 revealed the first deepwater (> 1000 m water depth) cold seeps found on the US Atlantic margin north of Cape Hatteras as well as 47 new upper slope seeps (http://www.noaanews.noaa.gov/stories2012/20121219_gas_seeps.html). In this new analysis, we identify over 500 water column backscatter anomalies (WCA) originating at the seafloor and extending to various heights in the water column between Cape Hatteras and the Nantucket margin. Data set quality control was achieved through secondary independent analysis of all WCA backscatter records by a highly experienced researcher who assigned a quality factor to each anomaly. Additionally, a subset of the data was analyzed using a Matlab code designed to automatically detect WCA in backscatter data. These quality-control and WCA comparison procedures provide confidence that several hundred of the WCA are robust picks. The observed WCA are structurally consistent with previously confirmed gas bubble plumes, being vertically elongate, rooted at the seafloor, and deflected by currents. They are not structurally consistent with other common WCA such as schooling or swarming organisms. Additionally, the bases of selected WCA that were identified in this analysis have recently been visually and acoustically confirmed to be associated with emission of gas bubbles from the seafloor by the NOAA remotely operated vehicle

  4. Bluefin autonomous underwater vehicles: Programs, systems, and acoustic issues

    NASA Astrophysics Data System (ADS)

    Bondaryk, Joseph E.

    2001-05-01

    Bluefin Robotics Corporation has been manufacturing autonomous underwater vehicles (AUVs) since spinning out of the MIT Sea Grant Laboratory in 1997. Bluefin currently makes three different diameter models of AUVs; the 9, 12, and 21, all based on the same free-flooded architecture and vectored-thrust propulsion design. Auxiliary acoustic systems include acoustic abort, ranging beacons, and acoustic modems. Vehicle navigation is aided by a downward-looking acoustic Doppler velocity logger (DVL). Sonar payloads can include: bottom profiler, side-scan sonar, SAS, forward-looking imagers (DIDSON), as well as horizontal and vertical discrete hydrophone arrays. Acoustic issues that arise include: (1) transmission of sound through the ABS plastic vehicle shell; (2) the impact of vehicle self-noise on data; (3) interoperability of sonars with other acoustic emitters present on and off the vehicle; and (4) the impact of navigation on some acoustic operations like SAS. This talk will illustrate these issues with real data collected on various Bluefin vehicles.

  5. Simulation of Neutron Backscattering applied to organic material detection

    SciTech Connect

    Forero, N. C.; Cruz, A. H.; Cristancho, F.

    2007-10-26

    The Neutron Backscattering technique is tested when performing the task of localizing hydrogenated explosives hidden in soil. Detector system, landmine, soil and neutron source are simulated with Geant4 in order to obtain the number of neutrons detected when several parameters like mine composition, relative position mine-source and soil moisture are varied.0.

  6. Backscattering enhancement from a conducting surface with isotropic roughness

    NASA Astrophysics Data System (ADS)

    Knotts, M. E.; O'Donnell, K. A.

    1993-05-01

    Measurements are presented of the angular distribution of scattered intensity associated with backscattering enhancement from a conducting surface with two-dimensional roughness. For a linearly polarized incident wave, the diffusely scattered intensity is found to be significantly polarization-dependent.

  7. Simultaneous 2D Doppler backscattering from edge turbulence

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  8. Method and Apparatus for Computed Imaging Backscatter Radiography

    NASA Technical Reports Server (NTRS)

    Shedlock, Daniel (Inventor); Meng, Christopher (Inventor); Sabri, Nissia (Inventor); Dugan, Edward T. (Inventor); Jacobs, Alan M. (Inventor)

    2013-01-01

    Systems and methods of x-ray backscatter radiography are provided. A single-sided, non-destructive imaging technique utilizing x-ray radiation to image subsurface features is disclosed, capable of scanning a region using a fan beam aperture and gathering data using rotational motion.

  9. Alpha particle backscattering measurements used for chemical analysis of surfaces

    NASA Technical Reports Server (NTRS)

    Patterson, J. H.

    1967-01-01

    Alpha particle backscattering performs a chemical analysis of surfaces. The apparatus uses a curium source and a semiconductor detector to determine the energy spectrum of the particles. This in turn determines the chemical composition of the surface after calibration to known samples.

  10. AST Launch Vehicle Acoustics

    NASA Technical Reports Server (NTRS)

    Houston, Janice; Counter, D.; Giacomoni, D.

    2015-01-01

    The liftoff phase induces acoustic loading over a broad frequency range for a launch vehicle. These external acoustic environments are then used in the prediction of internal vibration responses of the vehicle and components which result in the qualification levels. Thus, predicting these liftoff acoustic (LOA) environments is critical to the design requirements of any launch vehicle. If there is a significant amount of uncertainty in the predictions or if acoustic mitigation options must be implemented, a subscale acoustic test is a feasible pre-launch test option to verify the LOA environments. The NASA Space Launch System (SLS) program initiated the Scale Model Acoustic Test (SMAT) to verify the predicted SLS LOA environments and to determine the acoustic reduction with an above deck water sound suppression system. The SMAT was conducted at Marshall Space Flight Center and the test article included a 5% scale SLS vehicle model, tower and Mobile Launcher. Acoustic and pressure data were measured by approximately 250 instruments. The SMAT liftoff acoustic results are presented, findings are discussed and a comparison is shown to the Ares I Scale Model Acoustic Test (ASMAT) results.

  11. An improved multivariate analytical method to assess the accuracy of acoustic sediment classification maps.

    NASA Astrophysics Data System (ADS)

    Biondo, M.; Bartholomä, A.

    2014-12-01

    High resolution hydro acoustic methods have been successfully employed for the detailed classification of sedimentary habitats. The fine-scale mapping of very heterogeneous, patchy sedimentary facies, and the compound effect of multiple non-linear physical processes on the acoustic signal, cause the classification of backscatter images to be subject to a great level of uncertainty. Standard procedures for assessing the accuracy of acoustic classification maps are not yet established. This study applies different statistical techniques to automated classified acoustic images with the aim of i) quantifying the ability of backscatter to resolve grain size distributions ii) understanding complex patterns influenced by factors other than grain size variations iii) designing innovative repeatable statistical procedures to spatially assess classification uncertainties. A high-frequency (450 kHz) sidescan sonar survey, carried out in the year 2012 in the shallow upper-mesotidal inlet the Jade Bay (German North Sea), allowed to map 100 km2 of surficial sediment with a resolution and coverage never acquired before in the area. The backscatter mosaic was ground-truthed using a large dataset of sediment grab sample information (2009-2011). Multivariate procedures were employed for modelling the relationship between acoustic descriptors and granulometric variables in order to evaluate the correctness of acoustic classes allocation and sediment group separation. Complex patterns in the acoustic signal appeared to be controlled by the combined effect of surface roughness, sorting and mean grain size variations. The area is dominated by silt and fine sand in very mixed compositions; in this fine grained matrix, percentages of gravel resulted to be the prevailing factor affecting backscatter variability. In the absence of coarse material, sorting mostly affected the ability to detect gradual but significant changes in seabed types. Misclassification due to temporal discrepancies

  12. Calculation of the effects of ice on the backscatter of a ground plane

    NASA Technical Reports Server (NTRS)

    Lambert, K. M.; Peters, L., Jr.

    1988-01-01

    Described is a technique for examining the effect of a rough ice layer on the backscatter of a ground plane. The technique is applied to the special case of a rough ice layer that is periodic in space. By assuming that the roughness is periodic, the backscatter of the ground plane can be found from the backscatter of a single period. Backscatter calculations are presented for a single period in which the thickness of the ice layer has a Gaussian shape.

  13. Acoustic Translation of an Acoustically Levitated Sample

    NASA Technical Reports Server (NTRS)

    Barmatz, M. B.; Allen, J. L.

    1986-01-01

    Acoustic-levitation apparatus uses only one acoustic mode to move sample from one region of chamber to another. Sample heated and cooled quickly by translation between hot and cold regions of levitation chamber. Levitated sample is raised into furnace region by raising plunger. Frequency of sound produced by transducers adjusted by feedback system to maintain (102) resonant mode, which levitates sample midway between transducers and plunger regardless of plunger position.

  14. Multiwavelength Comparison of Modeled and Measured Remote Tropospheric Aerosol Backscatter Over Pacific Ocean

    NASA Technical Reports Server (NTRS)

    Cutten, D. R.; Pueschel, R. F.; Srivastava, V.; Clarke, A. D.; Rothermel, J.; Spinhirne, J. D.; Menzies, R. T.

    1996-01-01

    Aerosol concentrations and size distributions in the middle and upper troposphere over the remote Pacific Ocean were measured with a forward scattering spectrometer probe (FSSP) on the NASA DC-8 aircraft during NASA's Global Backscatter Experiment (GLOBE) in May-June 1990. The FSSP size channels were recalibrated based on refractive index estimates from flight-level aerosol volatility measurements with a collocated laser optical particle counter (LOPC). The recalibrated FSSP size distributions were averaged over 100-s intervals, fitted with lo-normal distributions and used to calculate aerosol backscatter coefficients at selected wavelengths. The FSSP-derived backscatter estimates were averaged over 300-s intervals to reduce large random fluctuations. The smoothed FSSP aerosol backscatter coefficients were then compared with LOPC-derived backscatter values and with backscatter measured at or near flight level from four lidar systems operating at 0.53, 1.06, 9.11, 9.25, and 10.59 micrometers. Agreement between FSSP-derived and lidar-measured backscatter was generally best at flight level in homogeneous aerosol fields and at high backscatter values. FSSP data often underestimated low backscatter values especially at the longer wavelengths due to poor counting statistics for larger particles (greater than 0.8 micrometers diameter) that usually dominate aerosol backscatter at these wavelengths. FSSP data also underestimated backscatter at shorter wavelengths when particles smaller than the FSSP lower cutoff diameter (0.35 micrometers) made significant contributions to the total backscatter.

  15. 3D Visualization of Radar Backscattering Diagrams Based on OpenGL

    NASA Astrophysics Data System (ADS)

    Zhulina, Yulia V.

    2004-12-01

    A digital method of calculating the radar backscattering diagrams is presented. The method uses a digital model of an arbitrary scattering object in the 3D graphics package "OpenGL" and calculates the backscattered signal in the physical optics approximation. The backscattering diagram is constructed by means of rotating the object model around the radar-target line.

  16. Quasioptical design of integrated Doppler backscattering and correlation electron cyclotron emission systems on the DIII-D tokamak

    SciTech Connect

    Rhodes, T. L.; Peebles, W. A.; Nguyen, X.; Hillesheim, J. C.; Schmitz, L.; Wang, G.; White, A. E.

    2010-10-15

    The quasioptical design of a new integrated Doppler backscattering (DBS) and correlation electron cyclotron emission (CECE) system is presented. The design provides for simultaneous measurements of intermediate wavenumber density and long wavelength electron temperature turbulence behavior. The Doppler backscattering technique is sensitive to plasma turbulence flow and has been utilized to determine radial electric field, geodesic acoustic modes, zonal flows, and intermediate scale (k{approx}1-6 cm{sup -1}) density turbulence. The correlation ECE system measures a second turbulent field, electron temperature fluctuations, and is sensitive to long poloidal wavelength (k{<=}1.8 cm{sup -1}). The integrated system utilizes a newly installed in-vessel focusing mirror that produces a beam waist diameter of 3.5-5 cm in the plasma depending on the frequency. A single antenna (i.e., monostatic operation) is used for both launch and receive. The DBS wavenumber is selected via an adjustable launch angle and variable probing frequency. Due to the unique system design both positive and negative wavenumbers can be obtained, with a range of low to intermediate wavenumbers possible (approximately -3 to 10 cm{sup -1}). A unique feature of the design is the ability to place the DBS and CECE measurements at the same radial and poloidal locations allowing for cross correlation studies (e.g., measurement of nT cross-phase).

  17. Simulation of Cloud-aerosol Lidar with Orthogonal Polarization (CALIOP) Attenuated Backscatter Profiles Using the Global Model of Aerosol Processes (GLOMAP)

    NASA Astrophysics Data System (ADS)

    Young, Stuart; Cope, Martin; Lee, Sunhee; Emmerson, Kathryn; Woodhouse, Matthew; Bellouin, Nicolas

    2016-06-01

    To permit the calculation of the radiative effects of atmospheric aerosols, we have linked our aerosol-chemical transport model (CTMGLOMAP) to a new radiation module (UKCARADAER). In order to help assess and improve the accuracy of the radiation code, in particular the height dependence of the predicted scattering, we have developed a module that simulates attenuated backscatter (ABS) profiles that would be measured by the satellite-borne Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) if it were to sample an atmosphere with the same aerosol loading as predicted by the CTM. Initial results of our comparisons of the predicted ABS profiles with actual CALIOP data are encouraging but some differences are noted, particularly in marine boundary layers where the scattering is currently under-predicted and in dust layers where it is often over-predicted. The sources of these differences are being investigated.

  18. Nearfield Acoustical Holography

    NASA Astrophysics Data System (ADS)

    Hayek, Sabih I.

    Nearfield acoustical holography (NAH) is a method by which a set of acoustic pressure measurements at points located on a specific surface (called a hologram) can be used to image sources on vibrating surfaces on the acoustic field in three-dimensional space. NAH data are processed to take advantage of the evanescent wavefield to image sources that are separated less that one-eighth of a wavelength.

  19. Deep Water Acoustics

    DTIC Science & Technology

    2016-06-28

    Estimates of basin-wide sound speed ( temperature ) fields obtained by the combination of acoustic, altimetry, and other data types with ocean...of acoustic coherence at long ranges in the ocean. Estimates of basin-wide sound speed ( temperature ) fields obtained by the combination of acoustic...index.html Award Number N00014-13-1-0053 LONG-TERM GOALS The ultimate limitations to the performance of long-range sonar are due to ocean sound speed

  20. Acoustic Communications (ACOMMS) ATD

    DTIC Science & Technology

    2016-06-14

    Acoustic Communications (ACOMMS) ATD Tam Nguyen 2531 Jefferson Davis Hwy Arlington, VA 22242 phone: (703) 604-6013 ext 520 fax: (703) 604-6056...email: NguyenTL@navsea.navy.mil Award # N0001499PD30007 LONG-TERM GOALS The goal of the recently completed Acoustic Communications Advanced...Technology Demonstration program (ACOMMS ATD) was to demonstrate long range and moderate data rate underwater acoustic communications between a submarine

  1. Deep Water Ocean Acoustics

    DTIC Science & Technology

    2016-04-30

    OASIS, INC. 1 Report No. QSR-14C0172-Ocean Acoustics-043016 Quarterly Progress Report Technical and Financial Deep Water Ocean Acoustics...understanding of the impact of the ocean and seafloor environmental variability on deep- water (long-range) ocean acoustic propagation and to...improve our understanding. During the past few years, the physics effects studied have been three-dimensional propagation on global scales, deep water

  2. Registration of nine sorghum seed parent (A/B) lines

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Nine sorghum [Sorghum bicolor (L.) Moench] A1 cyto plasmic-genic male sterile seed parent (A) and their maintainer (B) lines [KS 133A/B, KS 134A/B, KS 135A/B, KS 136A/B, KS 137A/B, KS 138A/B, KS 139A/B, KS 140A/B and KS 141A/B] were released by the Kansas State University, Agricultural Research Cent...

  3. Acoustic dispersive prism

    NASA Astrophysics Data System (ADS)

    Esfahlani, Hussein; Karkar, Sami; Lissek, Herve; Mosig, Juan R.

    2016-01-01

    The optical dispersive prism is a well-studied element, which allows separating white light into its constituent spectral colors, and stands in nature as water droplets. In analogy to this definition, the acoustic dispersive prism should be an acoustic device with capability of splitting a broadband acoustic wave into its constituent Fourier components. However, due to the acoustical nature of materials as well as the design and fabrication difficulties, there is neither any natural acoustic counterpart of the optical prism, nor any artificial design reported so far exhibiting an equivalent acoustic behaviour. Here, based on exotic properties of the acoustic transmission-line metamaterials and exploiting unique physical behaviour of acoustic leaky-wave radiation, we report the first acoustic dispersive prism, effective within the audible frequency range 800 Hz–1300 Hz. The dispersive nature, and consequently the frequency-dependent refractive index of the metamaterial are exploited to split the sound waves towards different and frequency-dependent directions. Meanwhile, the leaky-wave nature of the structure facilitates the sound wave radiation into the ambient medium.

  4. Acoustic dispersive prism.

    PubMed

    Esfahlani, Hussein; Karkar, Sami; Lissek, Herve; Mosig, Juan R

    2016-01-07

    The optical dispersive prism is a well-studied element, which allows separating white light into its constituent spectral colors, and stands in nature as water droplets. In analogy to this definition, the acoustic dispersive prism should be an acoustic device with capability of splitting a broadband acoustic wave into its constituent Fourier components. However, due to the acoustical nature of materials as well as the design and fabrication difficulties, there is neither any natural acoustic counterpart of the optical prism, nor any artificial design reported so far exhibiting an equivalent acoustic behaviour. Here, based on exotic properties of the acoustic transmission-line metamaterials and exploiting unique physical behaviour of acoustic leaky-wave radiation, we report the first acoustic dispersive prism, effective within the audible frequency range 800 Hz-1300 Hz. The dispersive nature, and consequently the frequency-dependent refractive index of the metamaterial are exploited to split the sound waves towards different and frequency-dependent directions. Meanwhile, the leaky-wave nature of the structure facilitates the sound wave radiation into the ambient medium.

  5. Low frequency acoustic microscope

    DOEpatents

    Khuri-Yakub, Butrus T.

    1986-11-04

    A scanning acoustic microscope is disclosed for the detection and location of near surface flaws, inclusions or voids in a solid sample material. A focused beam of acoustic energy is directed at the sample with its focal plane at the subsurface flaw, inclusion or void location. The sample is scanned with the beam. Detected acoustic energy specularly reflected and mode converted at the surface of the sample and acoustic energy reflected by subsurface flaws, inclusions or voids at the focal plane are used for generating an interference signal which is processed and forms a signal indicative of the subsurface flaws, inclusions or voids.

  6. Acoustic dispersive prism

    PubMed Central

    Esfahlani, Hussein; Karkar, Sami; Lissek, Herve; Mosig, Juan R.

    2016-01-01

    The optical dispersive prism is a well-studied element, which allows separating white light into its constituent spectral colors, and stands in nature as water droplets. In analogy to this definition, the acoustic dispersive prism should be an acoustic device with capability of splitting a broadband acoustic wave into its constituent Fourier components. However, due to the acoustical nature of materials as well as the design and fabrication difficulties, there is neither any natural acoustic counterpart of the optical prism, nor any artificial design reported so far exhibiting an equivalent acoustic behaviour. Here, based on exotic properties of the acoustic transmission-line metamaterials and exploiting unique physical behaviour of acoustic leaky-wave radiation, we report the first acoustic dispersive prism, effective within the audible frequency range 800 Hz–1300 Hz. The dispersive nature, and consequently the frequency-dependent refractive index of the metamaterial are exploited to split the sound waves towards different and frequency-dependent directions. Meanwhile, the leaky-wave nature of the structure facilitates the sound wave radiation into the ambient medium. PMID:26739504

  7. Geological Interpretation of Bathymetric and Backscatter Imagery of the Sea Floor off Eastern Cape Cod, Massachusetts

    USGS Publications Warehouse

    Poppe, Larry J.; Paskevich, Valerie F.; Butman, Bradford; Ackerman, Seth D.; Danforth, William W.; Foster, Dave S.; Blackwood, Dann S.

    2006-01-01

    The imagery, interpretive data layers, and data presented herein were derived from multibeam echo-sounder data collected off Eastern Cape Cod, Massachusetts, and from the stations occupied to verify these acoustic data. The basic data layers show sea-floor topography, sun-illuminated shaded relief, and backscatter intensity; interpretive layers show the distributions of surficial sediment and sedimentary environments. Presented verification data include new and historical sediment grain-size analyses and a gallery of still photographs of the seabed. The multibeam data, which cover a narrow band of the sea floor extending from Provincetown around the northern tip of Cape Cod and south southeastward to off Monomoy Island, were collected during transits between concurrent mapping projects in the Stellwagen Bank National Marine Sanctuary (Valentine and others, 2001; Butman and others, 2004; and Valentine, 2005) and Great South Channel (Valentine and others, 2003a, b, c, d). Although originally collected to maximize the use of time aboard ship, these data provide a fundamental framework for research and management activities in this part of the Gulf of Maine (Noji and others, 2004), show the composition and terrain of the seabed, and provide information on sediment transport and benthic habitat. These data and interpretations also support ongoing modeling studies of the lower Cape's aquifer system (Masterson, 2004) and of erosional hotspots along the Cape Cod National Seashore (List and others, 2006).

  8. 12 CFR Appendixes A-B - [Reserved

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 12 Banks and Banking 6 2014-01-01 2012-01-01 true A Appendixes A-B Banks and Banking OFFICE OF THRIFT SUPERVISION, DEPARTMENT OF THE TREASURY CAPITAL Regulatory Capital Requirements Appendixes A-B...

  9. 12 CFR Appendixes A-B - [Reserved

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 12 Banks and Banking 6 2013-01-01 2012-01-01 true A Appendixes A-B Banks and Banking OFFICE OF THRIFT SUPERVISION, DEPARTMENT OF THE TREASURY CAPITAL Regulatory Capital Requirements Appendixes A-B...

  10. 12 CFR Appendixes A-B - [Reserved

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 12 Banks and Banking 5 2010-01-01 2010-01-01 false A Appendixes A-B Banks and Banking OFFICE OF THRIFT SUPERVISION, DEPARTMENT OF THE TREASURY CAPITAL Regulatory Capital Requirements Appendixes A-B...

  11. 12 CFR Appendixes A-B - [Reserved

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 12 Banks and Banking 5 2011-01-01 2011-01-01 false A Appendixes A-B Banks and Banking OFFICE OF THRIFT SUPERVISION, DEPARTMENT OF THE TREASURY CAPITAL Regulatory Capital Requirements Appendixes A-B...

  12. 12 CFR Appendixes A-B - [Reserved

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 12 Banks and Banking 6 2012-01-01 2012-01-01 false A Appendixes A-B Banks and Banking OFFICE OF THRIFT SUPERVISION, DEPARTMENT OF THE TREASURY CAPITAL Regulatory Capital Requirements Appendixes A-B...

  13. Retrieval of ocean subsurface particulate backscattering coefficient from space-borne CALIOP lidar measurements.

    PubMed

    Lu, Xiaomei; Hu, Yongxiang; Pelon, Jacques; Trepte, Charles; Liu, Katie; Rodier, Sharon; Zeng, Shan; Lucker, Patricia; Verhappen, Ron; Wilson, Jamie; Audouy, Claude; Ferrier, Christophe; Haouchine, Said; Hunt, Bill; Getzewich, Brian

    2016-12-12

    A new approach has been proposed to determine ocean subsurface particulate backscattering coefficient bbp from CALIOP 30° off-nadir lidar measurements. The new method also provides estimates of the particle volume scattering function at the 180° scattering angle. The CALIOP based layer-integrated lidar backscatter and particulate backscattering coefficients are compared with the results obtained from MODIS ocean color measurements. The comparison analysis shows that ocean subsurface lidar backscatter and particulate backscattering coefficient bbp can be accurately obtained from CALIOP lidar measurements, thereby supporting the use of space-borne lidar measurements for ocean subsurface studies.

  14. Topographic and Acoustic Estimates of Grain-Scale Roughness from High-Resolution Multibeam Echo-Sounder: Examples from the Colorado River in Marble and Grand Canyons.

    NASA Astrophysics Data System (ADS)

    Buscombe, D.; Grams, P. E.

    2014-12-01

    High-frequency (several hundred kilohertz) multibeam echo-sounder (MBES) systems have the potential to provide complete coverage of large areas (km2) of the bed, rapidly (mins to hrs), at high resolution (cm2), and with high positional accuracy (cm). Here, we explore the use of MBES data to estimate grain-scale roughness of submerged riverbed sediment. There are two broad approaches: 1) using digital elevation models constructed from depth soundings, and 2) using acoustic backscatter. We discuss the relative merits of both approaches using examples from data collected on the Colorado River in Marble and Grand Canyons, Arizona, USA. The primary advantage of acoustic backscatter over topography from soundings, for the purposes of sediment classification, is the potential to distinguish between sediment at a higher resolution. This is because soundings are point measurements, whereas a recorded backscatter magnitude is the integral of backscattered sound from all scatterers in the insonified area. In addition, this acoustic return contains information about both the roughness and the hardness/impedance of the sediment. The statistics of backscatter magnitudes alone are found to be a poor discriminator between sediment types perhaps because, using our 400 kHz system, the scattering regime changes from Rayleigh (sound scattering by particles smaller than the sound wavelength) for fine sand, to geometric (scattering by larger-than-sound-wavelength particles) for substrates coarser than sand. However, simple measures derived from backscatter power spectra (namely, the variance, integral lengthscale, and the intercept and slope from a power-law form - see Figure) are found to distinguish between patches of sand, gravel, cobbles and boulders. Using this dependence, we present a new data-driven approach to classify grain-scale roughness, developed by comparing the spectral properties of backscatter with bed-sediment observations using geo-referenced underwater video.

  15. Suspended particulate matter estimates using optical and acoustic sensors: application in Nestos River plume (Thracian Sea, North Aegean Sea).

    PubMed

    Anastasiou, Sotiria; Sylaios, Georgios K; Tsihrintzis, Vassilios A

    2015-06-01

    The present study investigates the use of combined methods of optical and acoustic sensors, in collaboration with direct in situ measurements, for the calibration and validation of a model transforming acoustic backscatter intensity series into suspended particulate matter (SPM) concentration datasets. The model follows previously elaborated techniques, placing particular attention to the parameterization of the acoustic absorption index as a function of water physical properties. Results were obtained from the annual deployment (during 2007-2008) of an upward-facing acoustic Doppler current profiler (ADCP) (307 kHz), equipped with a Wave Array, and an optical backscatter sensor (OBS), at the bottom of Thassos Passage near Nestos River plume (Thracian Sea, Northern Greece). The OBS was calibrated through linear regression, using 2007 and 2012 field sampling data, exhibiting an error of 13-14 % due to chlorophyll presence. The ADCP signal was calibrated through simultaneous measurements of backscatter intensity and turbidity profiles. Harmonic analysis on the model-produced SPM concentrations explained the tidal influence on their variability, especially during the summer. Empirical orthogonal functions analysis revealed the impact of waves and wave-induced currents on SPM variability. Finally, Nestos River sediment load was found uncorrelated to the SPM change in Thassos Passage, due to the dispersal and sediment deposition near the river mouth.

  16. A simple backscattering microscope for fast tracking of biological molecules

    NASA Astrophysics Data System (ADS)

    Sowa, Yoshiyuki; Steel, Bradley C.; Berry, Richard M.

    2010-11-01

    Recent developments in techniques for observing single molecules under light microscopes have helped reveal the mechanisms by which molecular machines work. A wide range of markers can be used to detect molecules, from single fluorophores to micron sized markers, depending on the research interest. Here, we present a new and simple objective-type backscattering microscope to track gold nanoparticles with nanometer and microsecond resolution. The total noise of our system in a 55 kHz bandwidth is ˜0.6 nm per axis, sufficient to measure molecular movement. We found our backscattering microscopy to be useful not only for in vitro but also for in vivo experiments because of lower background scattering from cells than in conventional dark-field microscopy. We demonstrate the application of this technique to measuring the motion of a biological rotary molecular motor, the bacterial flagellar motor, in live Escherichia coli cells.

  17. Corrosion detection in aircraft by X-ray backscatter methods

    PubMed

    Dunn; Yacout

    2000-10-01

    A limited-scan backscatter technique for detecting hidden corrosion and other flaws in aircraft has been demonstrated. Both simulation and experimental results indicate that as little as 5% material loss at depths up to 0.508 cm (0.200 in.) and 10% material loss at depths up to 0.635 cm (0.250 in.) beneath aircraft skin surfaces can be realiably detected. The technology involves analysis of backscattered photon data to yield a figure-of-merit whose value as a function of position indicates with high probability of detection whether or not flaws--such as corrosion, disbonding, macro-cracks, or voids--exist within scanned samples.

  18. Present State of Electron Backscatter Diffraction and Prospective Developments

    SciTech Connect

    Schwarzer, R A; Field, D P; Adams, B L; Kumar, M; Schwartz, A J

    2008-10-24

    Electron backscatter diffraction (EBSD), when employed as an additional characterization technique to a scanning electron microscope (SEM), enables individual grain orientations, local texture, point-to-point orientation correlations, and phase identification and distributions to be determined routinely on the surfaces of bulk polycrystals. The application has experienced rapid acceptance in metallurgical, materials, and geophysical laboratories within the past decade (Schwartz et al. 2000) due to the wide availability of SEMs, the ease of sample preparation from the bulk, the high speed of data acquisition, and the access to complementary information about the microstructure on a submicron scale. From the same specimen area, surface structure and morphology of the microstructure are characterized in great detail by the relief and orientation contrast in secondary and backscatter electron images, element distributions are accessed by energy dispersive spectroscopy (EDS), wavelength dispersive spectroscopy (WDS), or cathodoluminescence analysis, and the orientations of single grains and phases can now be determined, as a complement, by EBSD.

  19. RFID tag modification for full depth backscatter modulation

    DOEpatents

    Scott, Jeffrey Wayne [Pasco, WA; Pratt, Richard M [Richland, WA

    2010-07-20

    A modulated backscatter radio frequency identification device includes a diode detector configured to selectively modulate a reply signal onto an incoming continuous wave; communications circuitry configured to provide a modulation control signal to the diode detector, the diode detector being configured to modulate the reply signal in response to be modulation control signal; and circuitry configured to increase impedance change at the diode detector which would otherwise not occur because the diode detector rectifies the incoming continuous wave while modulating the reply signal, whereby reducing the rectified signal increases modulation depth by removing the reverse bias effects on impedance changes. Methods of improving depth of modulation in a modulated backscatter radio frequency identification device are also provided.

  20. Airborne backscatter lidar measurements at three wavelengths during ELITE

    NASA Astrophysics Data System (ADS)

    Schreiber, H. G.; Wirth, Martin; Moerl, P.; Renger, Wolfgang

    1995-09-01

    The German Aerospace Establishment (DLR) operates an airborne backscatter lidar based on a Nh:YAG laser which is flashlamp-pumped at 10 Hz. It works on the wavelengths 1064, 532, and 354 nm. It is mounted downward-looking on the research aircraft Falcon 20, flying at about 12 km altitude at speeds of 200 m/s. We present airborne measurements correlated with the orbit tracks of the shuttle-borne LITE-instrument (lidar in-space technology experiment). The emphasis in data evalution is on the comparison between the airborne and the shuttle- borne lidars. First results show excellent agreement between the two instruments even on details of cirrus clouds. The results comprise cloud geometrical and optical depths, as well as profiles of aerosol backscattering coefficients at three wavelengths.

  1. Depolarization of light backscattered by randomly oriented nonspherical particles.

    PubMed

    Mishchenko, M I; Hovenier, J W

    1995-06-15

    We derive theoretically and validate numerically general relationships for the elements of the backscattering matrix and for the linear, delta(L), and circular, delta(C), backscattering depolarization ratios for nonspherical particles in random orientation. For the practically important case of randomly oriented particles with a plane of symmetry or particles and their mirror particles occurring in equal numbers and in random orientation, delta(C) = 2delta(L)/(1 - delta(L)). Extensive T-matrix computations for randomly oriented spheroids demonstrate that, although both delta(L) and delta(C) are indicators of particle nonsphericity, they cannot be considered a universal measure of the departure of particle shape from that of a sphere and have no simple dependence on particle size and refractive index.

  2. Lidar extinction-to-backscatter ratio of the ocean.

    PubMed

    Churnside, James H; Sullivan, James M; Twardowski, Michael S

    2014-07-28

    Bio-optical models are used to develop a model of the lidar extinction-to-backscatter ratio applicable to oceanographic lidar. The model is based on chlorophyll concentration, and is expected to be valid for Case 1 waters. The limiting cases of narrow- and wide-beam lidars are presented and compared with estimates based on in situ optical measurements. Lidar measurements are also compared with the model using in situ or satellite estimates of chlorophyll concentration. A modified lidar ratio is defined, in which the properties of pure sea water are removed. This modified ratio is shown to be nearly constant for wide-beam lidar operating in low-chlorophyll waters, so accurate inversion to derive extinction and backscattering is possible under these conditions. This ratio can also be used for lidar calibration.

  3. Stimulated Raman backscattering of laser radiation in deep plasma channels

    NASA Astrophysics Data System (ADS)

    Kalmykov, S. Yu.; Shvets, G.

    2004-10-01

    Stimulated Raman backscattering (RBS) of intense laser radiation confined by a single-mode plasma channel with a radial variation of plasma frequency greater than a homogeneous-plasma RBS bandwidth is characterized by a strong transverse localization of resonantly driven electron plasma waves (EPW). The EPW localization reduces the peak growth rate of RBS and increases the amplification bandwidth. The continuum of nonbound modes of backscattered radiation shrinks the transverse field profile in a channel and increases the RBS growth rate. Solution of the initial-value problem shows that an electromagnetic pulse amplified by the RBS in the single-mode deep plasma channel has a group velocity higher than in the case of homogeneous-plasma Raman amplification. Implications to the design of a RBS pulse compressor in a plasma channel are discussed.

  4. Effects of vegetation canopy on the radar backscattering coefficient

    NASA Technical Reports Server (NTRS)

    Mo, T.; Blanchard, B. J.; Schmugge, T. J.

    1983-01-01

    Airborne L- and C-band scatterometer data, taken over both vegetation-covered and bare fields, were systematically analyzed and theoretically reproduced, using a recently developed model for calculating radar backscattering coefficients of rough soil surfaces. The results show that the model can reproduce the observed angular variations of radar backscattering coefficient quite well via a least-squares fit method. Best fits to the data provide estimates of the statistical properties of the surface roughness, which is characterized by two parameters: the standard deviation of surface height, and the surface correlation length. In addition, the processes of vegetation attenuation and volume scattering require two canopy parameters, the canopy optical thickness and a volume scattering factor. Canopy parameter values for individual vegetation types, including alfalfa, milo and corn, were also determined from the best-fit results. The uncertainties in the scatterometer data were also explored.

  5. Porosity estimation of alumina samples based on resonant backscattering spectrometry

    NASA Astrophysics Data System (ADS)

    Mokhles Gerami, F.; Kakuee, O.; Mohammadi, S.

    2016-04-01

    In this work, columnar porous alumina samples were investigated using the 16O(α,α)16O resonance scattering at 3.045 MeV. If the incident energy is slightly above the resonance energy, a resonance peak appears in the energy spectra of the backscattered ions. The position and width of this peak for non-porous samples are mainly determined by the experimental setup, whilst for porous materials, the peak position shifts towards higher energies under certain conditions. This effect can be explained by the lower amount of material which the ions encounter along the backscattered trajectories. The energy shift of the resonance peak towards higher energies was revealed experimentally and discussed theoretically. The estimated porosities of the samples based on this energy shift were compared with those evaluated from the graphical analysis of the images obtained by field emission scanning electron microscopy.

  6. The effects of changes in loblolly pine biomass and soil moisture on ERS-1 SAR backscatter

    SciTech Connect

    Wang, Y.; Melack, J.M.; Davis, F.W. . Center for Remote Sensing and Environmental Optics); Kasischke, E.S.; Christensen, N.L. Jr. . School of the Environment)

    1994-07-01

    For young loblolly pine stands at Duke Forest (North Carolina, USA), when the ground was wet, the observed ERS-1 SAR backscatter from short-grass fields of 0.05 kg/m[sup 2] biomass was [ge] the backscatter from the stands, and there was no significant correlation between the backscatter and biomass. Under dry soil conditions, the backscatter increased about 2--3 dB as the biomass increased from 0.05 kg/m[sup 2] to about 0.5--1.5 kg/m[sup 2], and the backscatter may be saturated near a 0.5--1.5 kg/m[sup 2] biomass level. The correlation coefficient between the backscatter and biomass was r[sup 2] = 0.46. When the Santa Barbara microwave canopy backscatter model was applied to simulate the ERS-1 SAR backscatter from the stands over dry ground, modeled and observed backscatter had similar trends with increasing biomass. For these stands, sensitivity analyses using the model showed that as the surface-soil moisture increased, the major contributor to the total backscatter was changed from canopy volume scattering to surface backscatter between 0.4 kg/m[sup 2] and about 1 kg/m[sup 2]. Signal saturating at low standing biomass and high sensitivity to soil moisture conditions limit the value of a short-wave (C-band) and steep local incidence angle (23[degree]) microwave sensor such as the ERS-1 SAR for forest monitoring.

  7. Comparison of Modeled Backscatter using Measured Aerosol Microphysics with Focused CW Lidar Data over Pacific

    NASA Technical Reports Server (NTRS)

    Srivastava, Vandana; Clarke, Antony D.; Jarzembski, Maurice A.; Rothermel, Jeffry

    1997-01-01

    During NASA's GLObal Backscatter Experiment (GLOBE) II flight mission over the Pacific Ocean in May-June 1990, extensive aerosol backscatter data sets from two continuous wave, focused CO2 Doppler lidars and an aerosol microphysics data set from a laser optical particle counter (LOPC) were obtained. Changes in aerosol loading in various air masses with associated changes in chemical composition, from sulfuric acid and sulfates to dustlike crustal material, significantly affected aerosol backscatter, causing variation of about 3 to 4 orders of magnitude. Some of the significant backscatter features encountered in different air masses were the low backscatter in subtropical air with even lower values in the tropics near the Intertropical Convergence Zone (ITCZ), highly variable backscatter in the ITCZ, mid-tropospheric aerosol backscatter background mode, and high backscatter in an Asian dust plume off the Japanese coast. Differences in aerosol composition and backscatter for northern and southern hemisphere also were observed. Using the LOPC measurements of physical and chemical aerosol properties, we determined the complex refractive index from three different aerosol mixture models to calculate backscatter. These values provided a well-defined envelope of modeled backscatter for various atmospheric conditions, giving good agreement with the lidar data over a horizontal sampling of approximately 18000 km in the mid-troposphere.

  8. Multiple scattering wavelength dependent backscattering of kaolin dust in the IR: Measurements and theory

    NASA Technical Reports Server (NTRS)

    Ben-David, Avishai

    1992-01-01

    Knowing the optical properties of aerosol dust is important for designing electro-optical systems and for modeling the effect on propagation of light in the atmosphere. As CO2 lidar technology becomes more advanced and is used for multiwavelength measurements, information on the wavelength dependent backscattering of aerosol dust particles is required. The volume backscattering coefficient of aerosols in the IR is relatively small. Thus, only a few field measurements of backscattering, usually at only a few wavelengths, are reported in the literature. We present spectral field measurements of backscattering of kaolin dust in the 9-11 micron wavelength range. As the quantity of dust increases, multiple scattering contributes more to the measured backscattered signal. The measurements show the effect of the dust quantity of the spectral backscatter measurements. A simple analytical two stream radiative transfer model is applied to confirm the measurements and to give insight to the multiple scattering spectra of backscattering.

  9. Measurement of magnetic field using Rayleigh backscattering in optical fibres

    SciTech Connect

    Wuilpart, M.; Caucheteur, C.; Goussarov, A.; Aerssens, M.; Massaut, V.; Megret, P.

    2011-07-01

    In this paper, we investigate the use of optical reflectometry in optical fibres for the measurement of magnetic field. The dedicated application concerns the measurement of plasma current in the fusion reactor. The measurement is based on the rotation of the polarization state of the Rayleigh backscattered signal when an optical pulse is launched in the fibre. Particular care has been undertaken to evaluate the impact of linear birefringence on the measurement performance. (authors)

  10. Anderson Mobility Gap Probed by Dynamic Coherent Backscattering.

    PubMed

    Cobus, L A; Skipetrov, S E; Aubry, A; van Tiggelen, B A; Derode, A; Page, J H

    2016-05-13

    We use dynamic coherent backscattering to study one of the Anderson mobility gaps in the vibrational spectrum of strongly disordered three-dimensional mesoglasses. Comparison of experimental results with the self-consistent theory of localization allows us to estimate the localization (correlation) length as a function of frequency in a wide spectral range covering bands of diffuse transport and a mobility gap delimited by two mobility edges. The results are corroborated by transmission measurements on one of our samples.

  11. Reduced Brillouin backscatter in CO2 laser-target interaction

    NASA Astrophysics Data System (ADS)

    Ng, A.; Offenberger, A. A.; Karttunen, S. J.

    1981-02-01

    A substantially reduced Brillouin reflection has been found for CO2 laser-irradiated high-density gas targets. In contrast to the high reflectivity (60%) previously observed for underdense hydrogen plasma, total backscatter (stimulated plus specular) is found to peak at 30% for incident intensity 5 times 10 to the twelfth W per square centimeter and decrease thereafter to 18% at 10 to the thirteenth W per square centimeter. The ponderomotive effects are postulated to account for these observations.

  12. Method and apparatus for measuring lung density by Compton backscattering

    DOEpatents

    Loo, Billy W.; Goulding, Frederick S.

    1991-01-01

    The density of the lung of a patient suffering from pulmonary edema is monitored by irradiating the lung by a single collimated beam of monochromatic photons and measuring the energies of photons Compton backscattered from the lung by a single high-resolution, high-purity germanium detector. A compact system geometry and a unique data extraction scheme are utilized to monimize systematic errors due to the presence of the chestwall and multiple scattering.

  13. Method and apparatus for measuring lung density by Compton backscattering

    DOEpatents

    Loo, B.W.; Goulding, F.S.

    1988-03-11

    The density of the lung of a patient suffering from pulmonary edema is monitored by irradiating the lung by a single collimated beam of monochromatic photons and measuring the energies of photons compton back-scattered from the lung by a single high-resolution, high-purity germanium detector. A compact system geometry and a unique data extraction scheme are utilized to minimize systematic errors due to the presence of the chestwall and multiple scattering. 11 figs., 1 tab.

  14. Surface effects on the microwave backscatter and emission of snow

    NASA Technical Reports Server (NTRS)

    Fung, A. K.; Stiles, W. H.; Ulaby, F. T.

    1980-01-01

    Measurements were performed with active and passive microwave sensors for both dry and wet snow conditions. A layer of Rayleigh scatterers with irregular surface boundaries is found to be a reasonable model for interpreting passive and active measurements in X- and Ku-bands. It was found that roughness had a significant effect on both backscatter and emission from wet snow; however, only a small effect was noted for dry snow.

  15. Turbulent Diffusivity under High Winds from Acoustic Measurements of Bubbles

    NASA Astrophysics Data System (ADS)

    Wang, D. W.; Wijesekera, H. W.; Jarosz, E.; Teague, W. J.; Pegau, W. S.

    2015-12-01

    Breaking surface waves generate layers of bubble clouds as air parcels entrain into the upper-ocean by the action of turbulent motions. The turbulent diffusivity in the bubble cloud layer was investigated by combining measurements of surface winds, waves, bubble acoustic backscatter, currents, and hydrography. These measurements were made at water depths of 60-90 m on the shelf of the Gulf of Alaska near Kayak Island during late December 2012, a period where the ocean was experiencing winds and significant wave heights up to 22 m s-1 and 9 m, respectively. Vertical profiles of acoustic backscatter decayed exponentially from the wave surface with e-folding lengths of about 0.6 to 6 m, while the bubble penetration depths were about 3 to 30 m. Both e-folding lengths and bubble depths were highly correlated with surface wind and wave conditions. The turbulent diffusion coefficients, inferred from e-folding length and bubble depth, varied from about 0.01 m2 s-1 to 0.4 m2 s-1. Our analysis suggests that the turbulent diffusivity in the bubble layer can be parameterized as a function of the cube of the wind friction velocity with a proportionality coefficient that depends weakly on wave age. Furthermore, in the bubble layer, on average, the shear production of the turbulent kinetic energy estimated by the diffusion coefficients was a similar order magnitude as the dissipation rate predicted by the wall boundary-layer theory.

  16. Backscatter LIDAR signal simulation applied to spacecraft LIDAR instrument design

    NASA Astrophysics Data System (ADS)

    Fochesatto, J.; Ristori, P.; Flamant, P.; Machado, M. E.; Singh, U.; Quel, E.

    2004-01-01

    In the framework of the scientific cooperation between the CEILAP laboratory (Argentina) and IPSL Institut Pierre Simon Laplace (France), devoted to the development of LIDAR techniques for Atmospheric sciences, a new area of scientific research, involving LIDARs, is starting in Argentine space technology. This new research area is under consideration at CEILAP in a joint effort with CONAE, the Argentine space agency, responsible for the development of future space missions. The LIDAR technique is necessary to improve our knowledge of meteorological, dynamic, and radiative processes in the South American region, for the whole troposphere and the lower stratosphere. To study this future mission, a simple model for the prediction of backscatter LIDAR signal from a spacecraft platform has been used to determine dimensions and detection characteristics of the space borne LIDAR instrument. The backscatter signal was retrieved from a modeled atmosphere considering its molecular density profile and taking into account different aerosols and clouds conditions. Signal-to-noise consideration, within the interval of possible dimension of the instrument parameters, allows us to constrain the telescope receiving area and to derive maximum range achievable, integration time and the final spatial and temporal resolutions of backscatter profiles.

  17. Visibility related to backscatter at 1.54 micron

    NASA Technical Reports Server (NTRS)

    Barber, T. L.; Larson, D. R.

    1986-01-01

    The lidar process was shown to have the necessary potential to fulfill the need for a remote measurement of visibility. Visibility can be inferred from a lidar return optical extinction. The wavelength 1.54 micron was chosen, being near the visible wavelength region and having a high eye safety threshol, 200,000 times higher than 1.06 micron; 1.54 is the erbium laser wavelength. This research utilized 105 measured height profiles of natural droplet size distributions data, taken in clouds, fog, and haze. These profiles were examined to determine the completeness of the droplet counting data. It was found that the particle spectrometer data were incomplete in the very light ford and haze so this portion of the data was eliminated. Utilizing the Mie theory, these droplet size distribution profiles were converted to backscatter at 1.54 micron and extinction in the visible region, 0.55 micron. Using Koschmeider's relationship, the extinction profiles were converted to visibility. The visibility and backscatter profiles were compared to develop a relationship between visibility and backscatter at 1.54 micron.

  18. Experimental findings in 180{degree} backscattering enhancement from solids

    SciTech Connect

    Ellmer, H.; Fischer, W.; Klose, A.; Semrad, D.

    1997-02-01

    We use a backscattering assembly developed recently to investigate the enhanced backscattering from polycrystalline materials near 180{degree}. The nominal scattering angle can be continuously varied between exactly 180.0{degree} and 178.5{degree}. It is shown that the stochastic model of flux peaking, though its predictions are surprisingly consistent with experimental results, either does not apply to real measurements or does only take account of a negligible fraction of the effect, which cannot be documented by experiment. The energy loss of He projectiles along correlated inward and outward trajectories turns out to be the same as in any random direction. To get the enhancement factor unaffected from detector resolution we measured the integrated backscattering yield from a number of targets with different thickness and deduced the yield by two different methods. For 400 keV He projectiles scattered from partly oxidized Ta a maximum enhancement factor of 2.8 is found. {copyright} {ital 1997} {ital The American Physical Society}

  19. Laser transmission-backscattering through inhomogeneous cirrus clouds.

    PubMed

    Ou, Szu-Cheng; Takano, Yoshihide; Liou, Kuo-Nan; Lefevre, Randy J; Johnson, Michael W

    2002-09-20

    We have developed a two-dimensional (2D) model for inhomogeneous cirrus clouds in plane-parallel and spherical geometries for the analysis of the transmission and backscattering of high-energy laser beams. The 2D extinction-coefficient and mean effective ice-crystal size fields for cirrus clouds can be determined from a combination of the remote sensing of cirrus clouds by use of the Advanced Very High Resolution Radiometer on board National Oceanic and Atmospheric Administration satellites and the vertical profiling of ice-crystal size distributions available from limited measurements. We demonstrate that satellite remote sensing of the position and the composition of high cirrus can be incorporated directly in the computer model developed for the transmission and backscattering of high-energy laser beams in realistic atmospheres. The results of laser direct transmission, forward scattering, and backscattering are analyzed carefully with respect to aircraft height, cirrus cloud optical depth, and ice-crystal size and orientation. Uncertainty in laser transmission that is due to errors in the retrieved ice-crystal size is negligible. But uncertainty of the order of 2% can be produced if the retrieved optical depth has errors of +/-0.05. With both the aircraft and the target near the cloud top, the direct transmission decreases, owing to the propagation of the laser beam through the curved portion of the cloud top. This effect becomes more pronounced as the horizontal distance between the aircraft and the target increases.

  20. Dependence of radar backscatter on coniferous forest biomass

    SciTech Connect

    Dobson, M.C.; Ulaby, F.T. ); LeToan, T.; Beaudoin, A. ); Kasischke, E.S. ); Christensen, N. )

    1992-03-01

    This paper discusses two independent experimental efforts which have examined the dependence of radar backscatter on aboveground biomass of mono specie conifer forests using polarimetric airborne SAR data at P-, L- and C-bands. Plantations of maritime pines near Landes, France range in age from 8 to 46 years with aboveground biomass between 5 and 105 tons/ha. Loblolly pine stands established on abandoned agricultural fields near Duke, NC range in age from 4 to 90 years and extend the range of aboveground biomass to 560 tons/ha for the older stands. These two experimental forests are largely complementary with respect to biomass. Radar backscatter is found to increase approximately linearly with increasing biomass until it saturates at a biomass level that depends on the radar frequency. The biomass saturation level is about 200 tons/ha at P-band and 100 tons/ha at L-band, and the C-band backscattering coefficient shows much less sensitivity to total aboveground biomass.

  1. Investigation of phonon coherence and backscattering using silicon nanomeshes

    PubMed Central

    Lee, Jaeho; Lee, Woochul; Wehmeyer, Geoff; Dhuey, Scott; Olynick, Deirdre L.; Cabrini, Stefano; Dames, Chris; Urban, Jeffrey J.; Yang, Peidong

    2017-01-01

    Phonons can display both wave-like and particle-like behaviour during thermal transport. While thermal transport in silicon nanomeshes has been previously interpreted by phonon wave effects due to interference with periodic structures, as well as phonon particle effects including backscattering, the dominant mechanism responsible for thermal conductivity reductions below classical predictions still remains unclear. Here we isolate the wave-related coherence effects by comparing periodic and aperiodic nanomeshes, and quantify the backscattering effect by comparing variable-pitch nanomeshes. We measure identical (within 6% uncertainty) thermal conductivities for periodic and aperiodic nanomeshes of the same average pitch, and reduced thermal conductivities for nanomeshes with smaller pitches. Ray tracing simulations support the measurement results. We conclude phonon coherence is unimportant for thermal transport in silicon nanomeshes with periodicities of 100 nm and higher and temperatures above 14 K, and phonon backscattering, as manifested in the classical size effect, is responsible for the thermal conductivity reduction. PMID:28051081

  2. The Acoustical Environment.

    ERIC Educational Resources Information Center

    Smith, Melissa

    Asserting that without an adequate acoustical environment, learning activities can be hindered, this paper reviews the literature on classroom acoustics, particularly noise, reverberation, signal-to-noise ratio, task performance, and recommendations for improvement. Through this review, the paper seeks to determine whether portable classrooms…

  3. Cystic acoustic schwannomas.

    PubMed

    Lunardi, P; Missori, P; Mastronardi, L; Fortuna, A

    1991-01-01

    Three cases with large space-occupying cysts in the cerebellopontine angle are reported. CT and MRI findings were not typical for acoustic schwannomas but at operation, besides the large cysts, small acoustic schwannomas could be detected and removed. The clinical and neuroradiological features of this unusual variety and the CT and MRI differential diagnosis of cerebellopontine angle lesions are discussed.

  4. Application of acoustic reflection tomography to sonar imaging.

    PubMed

    Ferguson, Brian G; Wyber, Ron J

    2005-05-01

    Computer-aided tomography is a technique for providing a two-dimensional cross-sectional view of a three-dimensional object through the digital processing of many one-dimensional views (or projections) taken at different look directions. In acoustic reflection tomography, insonifying the object and then recording the backscattered signal provides the projection information for a given look direction (or aspect angle). Processing the projection information for all possible aspect angles enables an image to be reconstructed that represents the two-dimensional spatial distribution of the object's acoustic reflectivity function when projected on the imaging plane. The shape of an idealized object, which is an elliptical cylinder, is reconstructed by applying standard backprojection, Radon transform inversion (using both convolution and filtered backprojections), and direct Fourier inversion to simulated projection data. The relative merits of the various reconstruction algorithms are assessed and the resulting shape estimates compared. For bandpass sonar data, however, the wave number components of the acoustic reflectivity function that are outside the passband are absent. This leads to the consideration of image reconstruction for bandpass data. Tomographic image reconstruction is applied to real data collected with an ultra-wideband sonar transducer to form high-resolution acoustic images of various underwater objects when the sonar and object are widely separated.

  5. Acoustic Remote Sensing

    NASA Astrophysics Data System (ADS)

    Dowling, David R.; Sabra, Karim G.

    2015-01-01

    Acoustic waves carry information about their source and collect information about their environment as they propagate. This article reviews how these information-carrying and -collecting features of acoustic waves that travel through fluids can be exploited for remote sensing. In nearly all cases, modern acoustic remote sensing involves array-recorded sounds and array signal processing to recover multidimensional results. The application realm for acoustic remote sensing spans an impressive range of signal frequencies (10-2 to 107 Hz) and distances (10-2 to 107 m) and involves biomedical ultrasound imaging, nondestructive evaluation, oil and gas exploration, military systems, and Nuclear Test Ban Treaty monitoring. In the past two decades, approaches have been developed to robustly localize remote sources; remove noise and multipath distortion from recorded signals; and determine the acoustic characteristics of the environment through which the sound waves have traveled, even when the recorded sounds originate from uncooperative sources or are merely ambient noise.

  6. Acoustic suspension system

    NASA Technical Reports Server (NTRS)

    Lee, M. C.; Wang, T. G. (Inventor)

    1983-01-01

    An acoustic levitation system is described, with single acoustic source and a small reflector to stably levitate a small object while the object is processed as by coating or heating it. The system includes a concave acoustic source which has locations on opposite sides of its axis that vibrate towards and away from a focal point to generate a converging acoustic field. A small reflector is located near the focal point, and preferably slightly beyond it, to create an intense acoustic field that stably supports a small object near the reflector. The reflector is located about one-half wavelength from the focal point and is concavely curved to a radius of curvature (L) of about one-half the wavelength, to stably support an object one-quarter wavelength (N) from the reflector.

  7. Virtual acoustics displays

    NASA Technical Reports Server (NTRS)

    Wenzel, Elizabeth M.; Fisher, Scott S.; Stone, Philip K.; Foster, Scott H.

    1991-01-01

    The real time acoustic display capabilities are described which were developed for the Virtual Environment Workstation (VIEW) Project at NASA-Ames. The acoustic display is capable of generating localized acoustic cues in real time over headphones. An auditory symbology, a related collection of representational auditory 'objects' or 'icons', can be designed using ACE (Auditory Cue Editor), which links both discrete and continuously varying acoustic parameters with information or events in the display. During a given display scenario, the symbology can be dynamically coordinated in real time with 3-D visual objects, speech, and gestural displays. The types of displays feasible with the system range from simple warnings and alarms to the acoustic representation of multidimensional data or events.

  8. Cochlear bionic acoustic metamaterials

    NASA Astrophysics Data System (ADS)

    Ma, Fuyin; Wu, Jiu Hui; Huang, Meng; Fu, Gang; Bai, Changan

    2014-11-01

    A design of bionic acoustic metamaterial and acoustic functional devices was proposed by employing the mammalian cochlear as a prototype. First, combined with the experimental data in previous literatures, it is pointed out that the cochlear hair cells and stereocilia cluster are a kind of natural biological acoustic metamaterials with the negative stiffness characteristics. Then, to design the acoustic functional devices conveniently in engineering application, a simplified parametric helical structure was proposed to replace actual irregular cochlea for bionic design, and based on the computational results of such a bionic parametric helical structure, it is suggested that the overall cochlear is a local resonant system with the negative dynamic effective mass characteristics. There are many potential applications in the bandboard energy recovery device, cochlear implant, and acoustic black hole.

  9. Acoustic integrated extinction

    PubMed Central

    Norris, Andrew N.

    2015-01-01

    The integrated extinction (IE) is defined as the integral of the scattering cross section as a function of wavelength. Sohl et al. (2007 J. Acoust. Soc. Am. 122, 3206–3210. (doi:10.1121/1.2801546)) derived an IE expression for acoustic scattering that is causal, i.e. the scattered wavefront in the forward direction arrives later than the incident plane wave in the background medium. The IE formula was based on electromagnetic results, for which scattering is causal by default. Here, we derive a formula for the acoustic IE that is valid for causal and non-causal scattering. The general result is expressed as an integral of the time-dependent forward scattering function. The IE reduces to a finite integral for scatterers with zero long-wavelength monopole and dipole amplitudes. Implications for acoustic cloaking are discussed and a new metric is proposed for broadband acoustic transparency. PMID:27547100

  10. Direct Field Acoustic Testing

    NASA Technical Reports Server (NTRS)

    Larkin, Paul; Goldstein, Bob

    2008-01-01

    This paper presents an update to the methods and procedures used in Direct Field Acoustic Testing (DFAT). The paper will discuss some of the recent techniques and developments that are currently being used and the future publication of a reference standard. Acoustic testing using commercial sound system components is becoming a popular and cost effective way of generating a required acoustic test environment both in and out of a reverberant chamber. This paper will present the DFAT test method, the usual setup and procedure and the development and use of a closed-loop, narrow-band control system. Narrow-band control of the acoustic PSD allows all standard techniques and procedures currently used in random control to be applied to acoustics and some examples are given. The paper will conclude with a summary of the development of a standard practice guideline that is hoped to be available in the first quarter of next year.

  11. Virtual acoustics displays

    NASA Astrophysics Data System (ADS)

    Wenzel, Elizabeth M.; Fisher, Scott S.; Stone, Philip K.; Foster, Scott H.

    1991-03-01

    The real time acoustic display capabilities are described which were developed for the Virtual Environment Workstation (VIEW) Project at NASA-Ames. The acoustic display is capable of generating localized acoustic cues in real time over headphones. An auditory symbology, a related collection of representational auditory 'objects' or 'icons', can be designed using ACE (Auditory Cue Editor), which links both discrete and continuously varying acoustic parameters with information or events in the display. During a given display scenario, the symbology can be dynamically coordinated in real time with 3-D visual objects, speech, and gestural displays. The types of displays feasible with the system range from simple warnings and alarms to the acoustic representation of multidimensional data or events.

  12. Ab initio electronic and lattice dynamical properties of cerium dihydride

    NASA Astrophysics Data System (ADS)

    Gurel, Tanju; Eryigit, Resul

    2007-03-01

    The rare-earth metal hydrides are interesting systems because of the dramatic structural and electronic changes due to the hydrogen absorption and desorption. Among them, cerium dihydride (CeH2) is one of the less studied rare-earth metal-hydride. To have a better understanding, we have performed an ab initio study of electronic and lattice dynamical properties of CeH2 by using pseudopotential density functional theory within local density approximation (LDA) and a plane-wave basis. Electronic band structure of CeH2 have been obtained within LDA and as well as GW approximation. Lattice dynamical properties are calculated using density functional perturbation theory. The phonon spectrum is found to contain a set of high-frequency (˜ 850-1000 cm-1) optical bands, mostly hydrogen related, and low frequency cerium related acoustic modes climbing to 160 cm^ -1 at the zone boundary.

  13. Long-term continuous acoustical suspended-sediment measurements in rivers - Theory, application, bias, and error

    USGS Publications Warehouse

    Topping, David J.; Wright, Scott A.

    2016-05-04

    It is commonly recognized that suspended-sediment concentrations in rivers can change rapidly in time and independently of water discharge during important sediment‑transporting events (for example, during floods); thus, suspended-sediment measurements at closely spaced time intervals are necessary to characterize suspended‑sediment loads. Because the manual collection of sufficient numbers of suspended-sediment samples required to characterize this variability is often time and cost prohibitive, several “surrogate” techniques have been developed for in situ measurements of properties related to suspended-sediment characteristics (for example, turbidity, laser-diffraction, acoustics). Herein, we present a new physically based method for the simultaneous measurement of suspended-silt-and-clay concentration, suspended-sand concentration, and suspended‑sand median grain size in rivers, using multi‑frequency arrays of single-frequency side‑looking acoustic-Doppler profilers. The method is strongly grounded in the extensive scientific literature on the incoherent scattering of sound by random suspensions of small particles. In particular, the method takes advantage of theory that relates acoustic frequency, acoustic attenuation, acoustic backscatter, suspended-sediment concentration, and suspended-sediment grain-size distribution. We develop the theory and methods, and demonstrate the application of the method at six study sites on the Colorado River and Rio Grande, where large numbers of suspended-sediment samples have been collected concurrently with acoustic attenuation and backscatter measurements over many years. The method produces acoustical measurements of suspended-silt-and-clay and suspended-sand concentration (in units of mg/L), and acoustical measurements of suspended-sand median grain size (in units of mm) that are generally in good to excellent agreement with concurrent physical measurements of these quantities in the river cross sections at

  14. Acoustic and optical methods to infer water transparency at Time Series Station Spiekeroog, Wadden Sea

    NASA Astrophysics Data System (ADS)

    Schulz, Anne-Christin; Badewien, Thomas H.; Garaba, Shungudzemwoyo P.; Zielinski, Oliver

    2016-11-01

    Water transparency is a primary indicator of optical water quality that is driven by suspended particulate and dissolved material. A data set from the operational Time Series Station Spiekeroog located at a tidal inlet of the Wadden Sea was used to perform (i) an inter-comparison of observations related to water transparency, (ii) correlation tests among these measured parameters, and (iii) to explore the utility of both acoustic and optical tools in monitoring water transparency. An Acoustic Doppler Current Profiler was used to derive the backscatter signal in the water column. Optical observations were collected using above-water hyperspectral radiometers and a submerged turbidity metre. Bio-fouling on the turbidity sensors optical windows resulted in measurement drift and abnormal values during quality control steps. We observed significant correlations between turbidity collected by the submerged metre and that derived from above-water radiometer observations. Turbidity from these sensors was also associated with the backscatter signal derived from the acoustic measurements. These findings suggest that both optical and acoustic measurements can be reasonable proxies of water transparency with the potential to mitigate gaps and increase data quality in long-time observation of marine environments.

  15. Integrating Acoustic Imaging of Flow Regimes With Bathymetry: A Case Study, Main Endeavor Field

    NASA Astrophysics Data System (ADS)

    Bemis, K. G.; Rona, P. A.; Jackson, D. R.; Jones, C. D.

    2003-12-01

    A unified view of the seafloor and the hydrothermal flow regimes (plumes and diffuse flow) is constructed for three major vent clusters in the Main Endeavour Field (e.g., Grotto, S&M, and Salut) of the Endeavour Segment, Juan de Fuca Ridge. The Main Endeavour Field is one of RIDGE 2000's Integrated Study Sites. A variety of visualization techniques are used to reconstruct the plumes (3D) and the diffuse flow field (2D) based on our acoustic imaging data set (July 2000 cruise). Plumes are identified as volumes of high backscatter intensity (indicating high particulate content or sharp density contrasts due to temperature variations) that remained high intensity when successive acoustic pings were subtracted (indicating that the acoustic targets producing the backscatter were in motion). Areas of diffuse flow are detected using our acoustic scintillation technique (AST). For the Grotto vent region (where a new Doppler technique was used to estimate vertical velocities in the plume), we estimate the areal partitioning between black smoker and diffuse flow in terms of volume fluxes. The volumetric and areal regions, where plume and diffuse flow were imaged, are registered over the bathymetry and compared to geologic maps of each region. The resulting images provide a unified view of the seafloor by integrating hydrothermal flow with geology.

  16. Acoustic mapping velocimetry

    NASA Astrophysics Data System (ADS)

    Muste, M.; Baranya, S.; Tsubaki, R.; Kim, D.; Ho, H.; Tsai, H.; Law, D.

    2016-05-01

    Knowledge of sediment dynamics in rivers is of great importance for various practical purposes. Despite its high relevance in riverine environment processes, the monitoring of sediment rates remains a major and challenging task for both suspended and bed load estimation. While the measurement of suspended load is currently an active area of testing with nonintrusive technologies (optical and acoustic), bed load measurement does not mark a similar progress. This paper describes an innovative combination of measurement techniques and analysis protocols that establishes the proof-of-concept for a promising technique, labeled herein Acoustic Mapping Velocimetry (AMV). The technique estimates bed load rates in rivers developing bed forms using a nonintrusive measurements approach. The raw information for AMV is collected with acoustic multibeam technology that in turn provides maps of the bathymetry over longitudinal swaths. As long as the acoustic maps can be acquired relatively quickly and the repetition rate for the mapping is commensurate with the movement of the bed forms, successive acoustic maps capture the progression of the bed form movement. Two-dimensional velocity maps associated with the bed form migration are obtained by implementing algorithms typically used in particle image velocimetry to acoustic maps converted in gray-level images. Furthermore, use of the obtained acoustic and velocity maps in conjunction with analytical formulations (e.g., Exner equation) enables estimation of multidirectional bed load rates over the whole imaged area. This paper presents a validation study of the AMV technique using a set of laboratory experiments.

  17. Acoustic cooling engine

    DOEpatents

    Hofler, Thomas J.; Wheatley, John C.; Swift, Gregory W.; Migliori, Albert

    1988-01-01

    An acoustic cooling engine with improved thermal performance and reduced internal losses comprises a compressible fluid contained in a resonant pressure vessel. The fluid has a substantial thermal expansion coefficient and is capable of supporting an acoustic standing wave. A thermodynamic element has first and second ends and is located in the resonant pressure vessel in thermal communication with the fluid. The thermal response of the thermodynamic element to the acoustic standing wave pumps heat from the second end to the first end. The thermodynamic element permits substantial flow of the fluid through the thermodynamic element. An acoustic driver cyclically drives the fluid with an acoustic standing wave. The driver is at a location of maximum acoustic impedance in the resonant pressure vessel and proximate the first end of the thermodynamic element. A hot heat exchanger is adjacent to and in thermal communication with the first end of the thermodynamic element. The hot heat exchanger conducts heat from the first end to portions of the resonant pressure vessel proximate the hot heat exchanger. The hot heat exchanger permits substantial flow of the fluid through the hot heat exchanger. The resonant pressure vessel can include a housing less than one quarter wavelength in length coupled to a reservoir. The housing can include a reduced diameter portion communicating with the reservoir. The frequency of the acoustic driver can be continuously controlled so as to maintain resonance.

  18. Acoustic sniper localization system

    NASA Astrophysics Data System (ADS)

    Prado, Gervasio; Dhaliwal, Hardave; Martel, Philip O.

    1997-02-01

    Technologies for sniper localization have received increased attention in recent months as American forces have been deployed to various trouble spots around the world. Among the technologies considered for this task acoustics is a natural choice for various reasons. The acoustic signatures of gunshots are loud and distinctive, making them easy to detect even in high noise background environments. Acoustics provides a passive sensing technology with excellent range and non line of sight capabilities. Last but not least, an acoustic sniper location system can be built at a low cost with off the shelf components. Despite its many advantages, the performance of acoustic sensors can degrade under adverse propagation conditions. Localization accuracy, although good, is usually not accurate enough to pinpoint a sniper's location in some scenarios (for example which widow in a building or behind which tree in a grove). For these more demanding missions, the acoustic sensor can be used in conjunction with an infra red imaging system that detects the muzzle blast of the gun. The acoustic system can be used to cue the pointing system of the IR camera in the direction of the shot's source.

  19. The room acoustic rendering equation.

    PubMed

    Siltanen, Samuel; Lokki, Tapio; Kiminki, Sami; Savioja, Lauri

    2007-09-01

    An integral equation generalizing a variety of known geometrical room acoustics modeling algorithms is presented. The formulation of the room acoustic rendering equation is adopted from computer graphics. Based on the room acoustic rendering equation, an acoustic radiance transfer method, which can handle both diffuse and nondiffuse reflections, is derived. In a case study, the method is used to predict several acoustic parameters of a room model. The results are compared to measured data of the actual room and to the results given by other acoustics prediction software. It is concluded that the method can predict most acoustic parameters reliably and provides results as accurate as current commercial room acoustic prediction software. Although the presented acoustic radiance transfer method relies on geometrical acoustics, it can be extended to model diffraction and transmission through materials in future.

  20. PRSEUS Acoustic Panel Fabrication

    NASA Technical Reports Server (NTRS)

    Nicolette, Velicki; Yovanof, Nicolette P.; Baraja, Jaime; Mathur, Gopal; Thrash, Patrick; Pickell, Robert

    2011-01-01

    This report describes the development of a novel structural concept, Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS), that addresses the demanding fuselage loading requirements for the Hybrid Wing or Blended Wing Body (BWB) airplane configuration with regards to acoustic response. A PRSEUS panel was designed and fabricated and provided to NASA-LaRC for acoustic response testing in the Structural Acoustics Loads and Transmission (SALT) facility). Preliminary assessments of the sound transmission characteristics of a PRSEUS panel subjected to a representative Hybrid Wing Body (HWB) operating environment were completed for the NASA Environmentally Responsible Aviation (ERA) Program.

  1. Acoustic well cleaner

    DOEpatents

    Maki, Jr., Voldi E.; Sharma, Mukul M.

    1997-01-21

    A method and apparatus are disclosed for cleaning the wellbore and the near wellbore region. A sonde is provided which is adapted to be lowered into a borehole and which includes a plurality of acoustic transducers arranged around the sonde. Electrical power provided by a cable is converted to acoustic energy. The high intensity acoustic energy directed to the borehole wall and into the near wellbore region, redissolves or resuspends the material which is reducing the permeability of the formation and/or restricting flow in the wellbore.

  2. Acoustical heat pumping engine

    DOEpatents

    Wheatley, John C.; Swift, Gregory W.; Migliori, Albert

    1983-08-16

    The disclosure is directed to an acoustical heat pumping engine without moving seals. A tubular housing holds a compressible fluid capable of supporting an acoustical standing wave. An acoustical driver is disposed at one end of the housing and the other end is capped. A second thermodynamic medium is disposed in the housing near to but spaced from the capped end. Heat is pumped along the second thermodynamic medium toward the capped end as a consequence both of the pressure oscillation due to the driver and imperfect thermal contact between the fluid and the second thermodynamic medium.

  3. Acoustical heat pumping engine

    DOEpatents

    Wheatley, J.C.; Swift, G.W.; Migliori, A.

    1983-08-16

    The disclosure is directed to an acoustical heat pumping engine without moving seals. A tubular housing holds a compressible fluid capable of supporting an acoustical standing wave. An acoustical driver is disposed at one end of the housing and the other end is capped. A second thermodynamic medium is disposed in the housing near to but spaced from the capped end. Heat is pumped along the second thermodynamic medium toward the capped end as a consequence both of the pressure oscillation due to the driver and imperfect thermal contact between the fluid and the second thermodynamic medium. 2 figs.

  4. Estimation of Mars radar backscatter from measured surface rock populations

    USGS Publications Warehouse

    Baron, J.E.; Simpson, R.A.; Tyler, G.L.; Moore, H.J.; Harmon, J.K.

    1998-01-01

    Reanalysis of rock population data at the Mars Viking Lander sites has yielded updated values of rock fractional surface coverage (about 0.16 at both sites, including outcrops) and new estimates of rock burial depths and axial ratios. These data are combined with a finite difference time domain (FDTD) numerical scattering model to estimate diffuse backscatter due to rocks at both the Lander l (VL1) and Lander 2 (VL2) sites. We consider single scattering from both surface and subsurface objects of various shapes, ranging from an ideal sphere to an accurate digitized model of a terrestrial rock. The FDTD cross-section calculations explicitly account for the size, shape, composition, orientation, and burial state of the scattering object, the incident wave angle and polarization, and the composition of the surface. We calculate depolarized specific cross sections at 12.6 cm wavelength due to lossless rock-like scatterers of about 0.014 at VL1 and 0.023 at VL2, which are comparable to the measured ranges of 0.019-0.032 and 0.012-0.018, respectively. We also discuss the variation of the diffuse cross section as the local angle of incidence, ??i, changes. Numerical calculations for a limited set of rock shapes indicate a marked difference between the angular backscattering behavior of wavelength-scale surface and subsurface rocks: while subsurface rocks scatter approximately as a cosine power law, surface rocks display a complex variation, often with peak backscattering at high incidence angles (??i = 70??-75??). Copyright 1998 by the American Geophysical Union.

  5. Evaluation of a compact sensor for backscattering and absorption

    NASA Astrophysics Data System (ADS)

    Gainusa Bogdan, Alina; Boss, Emmanuel S.

    2011-07-01

    Seawater inherent optical properties (IOPs) are key parameters in a wide range of applications in environmental studies and oceanographic research. In particular, the absorption coefficient (a) is the typical IOP used to obtain the concentration of chlorophyll-a in the water---a critical parameter in biological oceanography studies and the backscattering coefficient (bb) is used as a measure of turbidity. In this study, we test a novel instrument concept designed to obtain both the absorption and backscattering coefficients. The instrument would emit a collimated monochromatic light beam into the water retrieving the backscattered light intensity as a function of distance from the center of illumination. We use Monte Carlo modeling of light propagation to create an inversion algorithm that translates the signal from such an instrument into values of a and bb. Our results, based on simulations spanning the bulk of natural values of seawater IOP combinations, indicate that a 6.2cm diameter instrument with a radial resolution of 1cm would be capable of predicting bb within less than 13.4% relative difference and a within less than 57% relative difference (for 90% of the inverted a values, the relative errors fall below 29.7%). Additionally, these errors could be further reduced by constraining the inversion algorithm with information from concurrent measurements of other IOPs. Such a compact and relatively simple device could have multiple applications for in situ optical measurements, including a and bb retrievals from instrumentation mounted on autonomous underwater vehicles. Furthermore, the same methodology could possibly be used for an out-of-water sensor.

  6. Concentration measurement of yeast suspensions using high frequency ultrasound backscattering.

    PubMed

    Elvira, Luis; Vera, Pedro; Cañadas, Francisco Jesús; Shukla, Shiva Kant; Montero, Francisco

    2016-01-01

    This work proposes the use of an ultrasound based technique to measure the concentration of yeasts in liquid suspension. This measurement was achieved by the detection and quantification of ultrasonic echoes backscattered by the cells. More specifically, the technique was applied to the detection and quantification of Saccharomyces cerevisiae. A theoretical approach was proposed to get the average density and sound speed of the yeasts, which were found to be 1116 kg/m(3) and 1679 m/s, respectively. These parameters were needed to model the waves backscattered by each single cell. A pulse-echo arrangement working around 50 MHz, being able to detect echoes from single yeasts was used to characterize experimentally yeast solutions from 10(2) to 10(7)cells/ml. The Non-negative Matrix Factorization denoising technique was applied for data analysis. This technique required a previous learning of the spectral patterns of the echoes reflected from yeasts in solution and the base noise from the liquid medium. Comparison between pulse correlation (without denoising) and theoretical and experimental pattern learning was made to select the best signal processing. A linear relation between ultrasound output and concentration was obtained with correlation coefficient R(2)=0.996 for the experimental learning. Concentrations from 10(4) to 10(7)cells/ml were detected above the base noise. These results show the viability of using the ultrasound backscattering technique to detect yeasts and measure their concentration in liquid cultures, improving the sensitivity obtained using spectrophotometric methods by one order of magnitude.

  7. The relationship between ultrasonic backscatter and trabecular anisotropic microstructure in cancellous bone

    NASA Astrophysics Data System (ADS)

    Liu, Chengcheng; Ta, Dean; Fujita, Fuminori; Hachiken, Takuma; Matsukawa, Mami; Mizuno, Katsunori; Wang, Weiqi

    2014-02-01

    To investigate the relationship between ultrasonic backscatter and trabecular microstructure, ultrasonic backscatter measurements were performed on cylindrical bovine cancellous bone samples in vitro. The backscatter signals from different specimen angles were obtained by rotating the specimen at various central frequencies. The backscatter signal varied a lot as the specimen angle changed. The main trabecular alignment (MTA) orientation was estimated by the maximum of signal energy and integrated reflection coefficient, or the minor axis of fitted ellipse for apparent integrated backscatter and the backscattered spectrum centroid frequency versus specimen angle. The degree of anisotropy (DA) was estimated by the eccentricity of the fitted ellipse with highly significant correlations. The MTA orientation and DA value estimation method proposed in this study is useful for ultrasonic cancellous bone assessment.

  8. Relating the microwave backscattering coefficient to leaf area index

    NASA Technical Reports Server (NTRS)

    Ulaby, F. T.; Allen, C. T.; Eger, G., III; Kanemasu, E.

    1984-01-01

    This paper examines the relationship between the microwave backscattering coefficient of a vegetation canopy, sigma (can, 0) and the canopy's leaf area index (LAI). The relationship is established through the development of one model for corn and sorghum and another for wheat. Both models are extensions of the cloud model of Attema and Ulaby (1978). Analysis of experimental data measured at 8.6, 13.0, 17.0, and 35.6 GHz indicates that most of the temporal variations of sigma (can, 0) can be accounted for through variations in green LAI alone, if the latter is greater than 0.5.

  9. Coherent Backscattering in the Cross-Polarized Channel

    NASA Technical Reports Server (NTRS)

    Mischenko, Michael I.; Mackowski, Daniel W.

    2011-01-01

    We analyze the asymptotic behavior of the cross-polarized enhancement factor in the framework of the standard low-packing-density theory of coherent backscattering by discrete random media composed of spherically symmetric particles. It is shown that if the particles are strongly absorbing or if the smallest optical dimension of the particulate medium (i.e., the optical thickness of a plane-parallel slab or the optical diameter of a spherically symmetric volume) approaches zero, then the cross-polarized enhancement factor tends to its upper-limit value 2. This theoretical prediction is illustrated using direct computer solutions of the Maxwell equations for spherical volumes of discrete random medium.

  10. DUNBID, the Delft University neutron backscattering imaging detector.

    PubMed

    Bom, V R; van Eijk, C W E; Ali, M A

    2005-01-01

    In the search for low-metallic land mines, the neutron backscattering technique may be applied if the soil is sufficiently dry. An advantage of this method is the speed of detection: the scanning speed may be made comparable to that of a metal detector. A two-dimensional position sensitive detector is tested to obtain an image of the back scattered thermal neutron radiation. Results of experiments using a radionuclide neutron source are presented. The on-mine to no-mine signal ratio can be improved by the application of a window on the neutron time-of-flight. Results using a pulsed neutron generator are also presented.

  11. Backscatter by azimuthally oriented ice crystals of cirrus clouds.

    PubMed

    Konoshonkin, Alexander; Wang, Zhenzhu; Borovoi, Anatoli; Kustova, Natalia; Liu, Dong; Xie, Chenbo

    2016-09-05

    The backscattering Mueller matrix has been calculated for the first time for the hexagonal ice columns and plates with both zenith and azimuth preferential orientations. The possibility of a vertically pointing polarization lidar measuring the full Mueller matrix for retrieving the orientation distributions of the crystals is considered. It is shown that the element m44 or, equivalently, the circular depolarization ratio distinguishes between the low and high zenith tilts of the crystals. Then, at their low or high zenith tilts, either the element m22 or m34, respectively, should be measured to retrieve the azimuth tilts.

  12. Backscattering by hexagonal ice crystals of cirrus clouds.

    PubMed

    Borovoi, Anatoli; Konoshonkin, Alexander; Kustova, Natalia

    2013-08-01

    Light backscattering by randomly oriented hexagonal ice crystals of cirrus clouds is considered within the framework of the physical-optics approximation. The fine angular structure of all elements of the Mueller matrix in the vicinity of the exact backward direction is first calculated and discussed. In particular, an approximate equation for the differential scattering cross section is obtained. Its simple spectral dependence is discussed. Also, a hollow of the linear depolarization ratio around the exact backward direction inherent to the long hexagonal columns is revealed.

  13. HAB detection based on absorption and backscattering properties of phytoplankton

    NASA Astrophysics Data System (ADS)

    Lei, Hui; Pan, Delu; Bai, Yan; Chen, Xiaoyan; Zhou, Yan; Zhu, Qiankun

    2011-11-01

    The coastal area of East China Sea (ECS) suffers from the harmful algal blooms (HAB) frequently every year in the warm season. The most common causative phytoplankton algal species of HAB in the ECS in recent years are Prorocentrum donghaiense (dinoflagellates), Karenia mikimotoi (dinoflagellates which could produce hemolytic and ichthyotoxins) and Skeletonema costatum (diatom). The discrimination between the dinoflagellates and diatom HAB through ocean color remote sensing approach can add the knowledge of HAB events in ECS and help to the precaution. A series of in-situ measurement consisted of absorption coefficient, total scattering and particulate backscattering coefficient was conducted in the southern coast of Zhejiang Province in May 2009, and the estuary of Changjiang River in August 2009 and December 2010, which encountered two HAB events and a moderate bloom. The Inherent Optical Properties (IOPs) of the bloom waters have significant difference between phytoplankton species in absorption and backscattering properties. The chlorophyll a specific absorption coefficient (a*phy(λ)) for the bloom patches (chlorophyll a concentration >6mg m-3) differ greatly from the adjacent normal seawater, with the a*phy(λ) of bloom water lower than 0.03 m2 mg-1 while the a*phy(λ) of the adjacent normal seawater is much higher (even up to 0.06 m2 mg-1). Meanwhile, the backscattering coefficients at 6 wavebands (420, 442, 470, 510, 590 and 700nm) are also remarkably lower for bloom waters (<0.01 m-1) than the normal seawater (> 0.02 m-1). The backscattering coefficient ratio (Rbp(λ)) is much lower for diatom bloom waters than for dinoflagellates types (0.01079 vs. 0.01227). A discrimination model based on IOPs is established, and several typical dinoflagellates and diatom bloom events including Prorocentrum donghaiense, Karenia mikimotoi and Skeletonema costatum in the ECS are picked out for testing with the MODIS-L2 and L3 ocean color remote sensing products from NASA

  14. Relating the radar backscattering coefficient to leaf-area index

    NASA Technical Reports Server (NTRS)

    Ulaby, F. T. (Principal Investigator); Allen, C.; Eger, G.; Kanemasu, E.

    1983-01-01

    The relationship between the radar backscattering coefficient of a vegetation canopy, sigma(0) sub can, and the canopy's leaf area index (LAI) is examined. The relationship is established through the development of a model for corn and sorghum and another for wheat. Both models are extensions of the cloud model of Attema and Ulaby (1978). Analysis of experimental data measured at 8.6, 13.0, 17.0, and 35.6 GHz indicates that most of the temporal variations of sigma(0) sub can can be accounted for through variations in green LAI alone, if the latter is greater than 0.5.

  15. Computed laser backscattering from turbid liquids - Comparison with laboratory results

    NASA Technical Reports Server (NTRS)

    Poole, L. R.

    1982-01-01

    A recently developed semianalytic Monte Carlo radiative transfer model applicable to oceanographic lidar systems (SALMON) has been used to simulate a series of laboratory experiments studying the backscatter of laser light from dispersions of Teflon spheres. Results obtained with SALMON, using best estimates of pertinent optical parameters, compared quite well with experimental data in both a qualitative and quantitative sense, with the largest relative discrepancies being approximately 30%. The results firmly establish the validity of SALMON in studying the performance of real oceanographic lidar systems.

  16. Computed laser backscattering from turbid liquids - Comparison with laboratory results

    NASA Astrophysics Data System (ADS)

    Poole, L. R.

    1982-06-01

    A recently developed semianalytic Monte Carlo radiative transfer model applicable to oceanographic lidar systems (SALMON) has been used to simulate a series of laboratory experiments studying the backscatter of laser light from dispersions of Teflon spheres. Results obtained with SALMON, using best estimates of pertinent optical parameters, compared quite well with experimental data in both a qualitative and quantitative sense, with the largest relative discrepancies being approximately 30%. The results firmly establish the validity of SALMON in studying the performance of real oceanographic lidar systems.

  17. A compton backscattering polarimeter for measuring longitudinal electron polarization

    SciTech Connect

    I. Passchier; Douglas W. Higinbotham; N. Vodinas; N. Papadakis; Kees de Jager; Ricardo Alarcon; T. Bauer; J.F.J. van den Brand; D. Boersma; T. Botto; M. Bouwhuis; H.J. Bulten; L. van Buuren; Rolf Ent; D. Geurts; M. Ferro-Luzzi; M. Harvey; Peter Heimberg; Blaine Norum; H.R. Poolman; M. van der Putte; E. Six; J.J.M. Steijger; D. Szczerba; H. de Vries

    1997-08-01

    Compton backscattering polarimetry provides a fast measurement of the polarization of an electron beam in a storage ring. Since the method is non-destructive, the polarization of the electrons can be monitored during internal target experiments. At NIKHEF a Compton polarimeter has been constructed to measure the polarization of the longitudinally polarized electrons stored in the AmPS ring. First results obtained with the polarimeter, the first Compton polarimeter to measure the polarization of a stored longitudinally polarized electron beam, are presented in this paper.

  18. Backscattering from dental restorations and splint materials during therapeutic radiation

    SciTech Connect

    Farman, A.G.; Sharma, S.; George, D.I.; Wilson, D.; Dodd, D.; Figa, R.; Haskell, B.

    1985-08-01

    Models were constructed to simulate as closely as possible the human oral cavity. Radiation absorbed doses were determined for controls and various test situations involving the presence of dental restorative and splint materials during cobalt-60 irradiation of the models. Adjacent gold full crowns and adjacent solid dental silver amalgam cores both increased the dose to the interproximal gingivae by 20%. Use of orthodontic full bands for splinting the jaws increased the dose to the buccal tissues by an average of 10%. Augmentation of dose through backscatter radiation was determined to be only slight for intracoronal amalgam fillings and stainless steel or plastic bracket splints.

  19. Low-Frequency Electromagnetic Backscatter from Buried Tunnels

    SciTech Connect

    Casey, K; Pao, H

    2006-06-21

    This progress report is submitted under a contract between the Special Project Office of DARPA and Lawrence Livermore National Laboratory. The Project Manager at DARPA is Dr. Michael Zatman. Our purpose under this contract is to investigate interactions between electromagnetic waves and a class of buried targets located in multilayered media with rough interfaces. In this report, we investigate three preliminary problems. In each case our specific goal is to understand various aspects of the electromagnetic wave interaction mechanisms with targets in layered media. The first problem, discussed in Section 2, is that of low-frequency electromagnetic backscattering from a tunnel that is cut into a lossy dielectric half-space. In this problem, the interface between the upper (free space) region and the lower (ground) region is smooth. The tunnel is assumed to be a cylindrical free-space region of infinite extent in its axial direction and with a diameter that is small in comparison to the free-space wavelength. Because its diameter is small, the tunnel can be modeled as a buried ''wire'' described by an equivalent impedance per unit length. In Section 3 we extend the analysis to include a statistically rough interface between the air and ground regions. The interface is modeled as a random-phase screen. Such a screen reduces the coherent power in a plane wave that is transmitted through it, scattering some of the total power into an incoherent field. Our analysis of this second problem quantifies the reduction in the coherent power backscattered from the buried tunnel that is caused by the roughness of the air-ground interface. The problem of low-frequency electromagnetic backscattering from two buried tunnels, parallel to each other but at different locations in the ground, is considered in Section 4. In this analysis, we wish to determine the conditions under which the presence of more than one tunnel can be detected via backscattering. Section 5 concludes the report

  20. One-way regular electromagnetic mode immune to backscattering.

    PubMed

    Deng, Xiaohua; Hong, Lujun; Zheng, Xiaodong; Shen, Linfang

    2015-05-10

    In this paper, we present a basic model of robust one-way electromagnetic modes at microwave frequencies, which is formed by a semi-infinite gyromagnetic yttrium-iron-garnet with dielectric cladding terminated by a metal plate. It is shown that this system supports not only one-way surface magnetoplasmons (SMPs) but also a one-way regular mode, which is guided by the mechanism of total internal reflection. Like one-way SMPs, the one-way regular mode can be immune to backscattering, and two types of one-way modes together make up a complete dispersion band for the system.

  1. Acoustic imaging system

    DOEpatents

    Smith, Richard W.

    1979-01-01

    An acoustic imaging system for displaying an object viewed by a moving array of transducers as the array is pivoted about a fixed point within a given plane. A plurality of transducers are fixedly positioned and equally spaced within a laterally extending array and operatively directed to transmit and receive acoustic signals along substantially parallel transmission paths. The transducers are sequentially activated along the array to transmit and receive acoustic signals according to a preestablished sequence. Means are provided for generating output voltages for each reception of an acoustic signal, corresponding to the coordinate position of the object viewed as the array is pivoted. Receptions from each of the transducers are presented on the same display at coordinates corresponding to the actual position of the object viewed to form a plane view of the object scanned.

  2. Compact acoustic refrigerator

    SciTech Connect

    Bennett, G.A.

    1991-12-31

    This invention is comprised of a compact acoustic refrigeration system that actively cools components, e.g., electrical circuits, in a borehole environment. An acoustic engine includes first thermodynamic elements for generating a standing acoustic wave in a selected medium. An acoustic refrigerator includes second thermodynamic elements located in the standing wave for generating a relatively cold temperature at a first end of the second thermodynamic elements and a relatively hot temperature at a second end of the second thermodynamic elements. A resonator volume cooperates with the first and second thermodynamic elements to support the standing wave. To accommodate the high heat fluxes required for heat transfer to/from the first and second thermodynamic elements, first heat pipes transfer heat from the heat load to the second thermodynamic elements and second heat pipes transfer heat from first and second thermodynamic elements to the borehole environment.

  3. Acoustic borehole logging

    SciTech Connect

    Medlin, W.L.; Manzi, S.J.

    1990-10-09

    This patent describes an acoustic borehole logging method. It comprises traversing a borehole with a borehole logging tool containing a transmitter of acoustic energy having a free-field frequency spectrum with at least one characteristic resonant frequency of vibration and spaced-apart receiver, repeatedly exciting the transmitter with a swept frequency tone burst of a duration sufficiently greater than the travel time of acoustic energy between the transmitter and the receiver to allow borehole cavity resonances to be established within the borehole cavity formed between the borehole logging tool and the borehole wall, detecting acoustic energy amplitude modulated by the borehole cavity resonances with the spaced-apart receiver, and recording an amplitude verses frequency output of the receiver in correlation with depth as a log of the borehole frequency spectrum representative of the subsurface formation comprising the borehole wall.

  4. Acoustic imaging system

    NASA Technical Reports Server (NTRS)

    Kendall, J. M., Jr.

    1977-01-01

    Tool detects noise sources by scanning sound "scene" and displaying relative location of noise-producing elements in area. System consists of ellipsoidal acoustic mirror and microphone and a display device.

  5. Compact acoustic refrigerator

    DOEpatents

    Bennett, G.A.

    1992-11-24

    A compact acoustic refrigeration system actively cools components, e.g., electrical circuits, in a borehole environment. An acoustic engine includes first thermodynamic elements for generating a standing acoustic wave in a selected medium. An acoustic refrigerator includes second thermodynamic elements located in the standing wave for generating a relatively cold temperature at a first end of the second thermodynamic elements and a relatively hot temperature at a second end of the second thermodynamic elements. A resonator volume cooperates with the first and second thermodynamic elements to support the standing wave. To accommodate the high heat fluxes required for heat transfer to/from the first and second thermodynamic elements, first heat pipes transfer heat from the heat load to the second thermodynamic elements and second heat pipes transfer heat from first and second thermodynamic elements to the borehole environment. 18 figs.

  6. Compact acoustic refrigerator

    DOEpatents

    Bennett, Gloria A.

    1992-01-01

    A compact acoustic refrigeration system actively cools components, e.g., electrical circuits (22), in a borehole environment. An acoustic engine (12, 14) includes first thermodynamic elements (12) for generating a standing acoustic wave in a selected medium. An acoustic refrigerator (16, 26, 28) includes second thermodynamic elements (16) located in the standing wave for generating a relatively cold temperature at a first end of the second thermodynamic elements (16) and a relatively hot temperature at a second end of the second thermodynamic elements (16). A resonator volume (18) cooperates with the first and second thermodynamic elements (12, 16) to support the standing wave. To accommodate the high heat fluxes required for heat transfer to/from the first and second thermodynamic elements (12, 16), first heat pipes (24, 26) transfer heat from the heat load (22) to the second thermodynamic elements (16) and second heat pipes (28, 32) transfer heat from first and second thermodynamic elements (12, 16) to the borehole environment.

  7. Acoustic bubble traps

    NASA Astrophysics Data System (ADS)

    Geisler, Reinhard; Kurz, Thomas; Lauterborn, Werner

    2000-07-01

    A small, oscillating bubble in a liquid can be trapped in the antinode of an acoustic standing wave field. Bubble stability is required for the study of single bubble sonoluminescence (SBSL). The properties of the acoustic resonator are essential for the stable trapping of sonoluminescing bubbles. Resonators can be chosen according to the intended application: size and geometry can be varied in a wide range. In this work, the acoustic responses of different resonators were measured by means of holographic interferometry, hydrophones and a laser vibrometer. Also, high-speed photography was used to observe the bubble dynamics. Several single, stable sonoluminescent bubbles were trapped simultaneously within an acoustic resonator in the pressure antinodes of a higher harmonic mode (few bubble sonoluminescence, FBSL).

  8. Department of Cybernetic Acoustics

    NASA Astrophysics Data System (ADS)

    The development of the theory, instrumentation and applications of methods and systems for the measurement, analysis, processing and synthesis of acoustic signals within the audio frequency range, particularly of the speech signal and the vibro-acoustic signal emitted by technical and industrial equipments treated as noise and vibration sources was discussed. The research work, both theoretical and experimental, aims at applications in various branches of science, and medicine, such as: acoustical diagnostics and phoniatric rehabilitation of pathological and postoperative states of the speech organ; bilateral ""man-machine'' speech communication based on the analysis, recognition and synthesis of the speech signal; vibro-acoustical diagnostics and continuous monitoring of the state of machines, technical equipments and technological processes.

  9. Basic Linear Acoustics

    NASA Astrophysics Data System (ADS)

    Pierce, Alan D.

    This chapter deals with the physical and mathematical aspects of sound when the disturbances are, in some sense, small. Acoustics is usually concerned with small-amplitude phenomena, and consequently a linear description is usually acoustics applicable. Disturbances are governed by the properties of the medium in which they occur, and the governing equations are the equations of continuum mechanics, which apply equally to gases, liquids, and solids. These include the mass, momentum, and energy equations, as well as thermodynamic principles. The viscosity and thermal conduction enter into the versions of these equations that apply to fluids. Fluids of typical great interest are air and sea water, and consequently this chapter includes a summary of their relevant acoustic properties. The foundation is also laid for the consideration of acoustic waves in elastic solids, suspensions, bubbly liquids, and porous media.

  10. Acoustics lecturing in Mexico

    NASA Astrophysics Data System (ADS)

    Beristain, Sergio

    2002-11-01

    Some thirty years ago acoustics lecturing started in Mexico at the National Polytechnic Institute in Mexico City, as part of the Bachelor of Science degree in Communications and Electronics Engineering curricula, including the widest program on this field in the whole country. This program has been producing acoustics specialists ever since. Nowadays many universities and superior education institutions around the country are teaching students at the B.Sc. level and postgraduate level many topics related to acoustics, such as Architectural Acoustics, Seismology, Mechanical Vibrations, Noise Control, Audio, Audiology, Music, etc. Also many institutions have started research programs in related fields, with participation of medical doctors, psychologists, musicians, engineers, etc. Details will be given on particular topics and development.

  11. Acoustic Neuroma Association

    MedlinePlus

    ... this sponsor... Platinum Sponsor More from this sponsor... Gold Sponsor University of Colorado Acoustic Neuroma Program Rocky Mountain Gamma Knife Center More from this sponsor... Gold Sponsor NYU Langone Medical Center Departments of Neurosurgery ...

  12. Wavefront modulation and subwavelength diffractive acoustics with an acoustic metasurface

    NASA Astrophysics Data System (ADS)

    Xie, Yangbo; Wang, Wenqi; Chen, Huanyang; Konneker, Adam; Popa, Bogdan-Ioan; Cummer, Steven A.

    2014-11-01

    Metasurfaces are a family of novel wavefront-shaping devices with planar profile and subwavelength thickness. Acoustic metasurfaces with ultralow profile yet extraordinary wave manipulating properties would be highly desirable for improving the performance of many acoustic wave-based applications. However, designing acoustic metasurfaces with similar functionality to their electromagnetic counterparts remains challenging with traditional metamaterial design approaches. Here we present a design and realization of an acoustic metasurface based on tapered labyrinthine metamaterials. The demonstrated metasurface can not only steer an acoustic beam as expected from the generalized Snell’s law, but also exhibits various unique properties such as conversion from propagating wave to surface mode, extraordinary beam-steering and apparent negative refraction through higher-order diffraction. Such designer acoustic metasurfaces provide a new design methodology for acoustic signal modulation devices and may be useful for applications such as acoustic imaging, beam steering, ultrasound lens design and acoustic surface wave-based applications.

  13. Wavefront modulation and subwavelength diffractive acoustics with an acoustic metasurface.

    PubMed

    Xie, Yangbo; Wang, Wenqi; Chen, Huanyang; Konneker, Adam; Popa, Bogdan-Ioan; Cummer, Steven A

    2014-11-24

    Metasurfaces are a family of novel wavefront-shaping devices with planar profile and subwavelength thickness. Acoustic metasurfaces with ultralow profile yet extraordinary wave manipulating properties would be highly desirable for improving the performance of many acoustic wave-based applications. However, designing acoustic metasurfaces with similar functionality to their electromagnetic counterparts remains challenging with traditional metamaterial design approaches. Here we present a design and realization of an acoustic metasurface based on tapered labyrinthine metamaterials. The demonstrated metasurface can not only steer an acoustic beam as expected from the generalized Snell's law, but also exhibits various unique properties such as conversion from propagating wave to surface mode, extraordinary beam-steering and apparent negative refraction through higher-order diffraction. Such designer acoustic metasurfaces provide a new design methodology for acoustic signal modulation devices and may be useful for applications such as acoustic imaging, beam steering, ultrasound lens design and acoustic surface wave-based applications.

  14. Comparison of Lidar Backscatter with Particle Distribution and GOES-7 Data in Hurricane Juliette

    NASA Technical Reports Server (NTRS)

    Jarzembski, Maurice A.; Srivastava, Vandana; McCaul, Eugene W., Jr.; Jedlovec, Gary J.; Atkinson, Robert J.; Pueschel, Rudolf F.; Cutten, Dean R.

    1997-01-01

    Measurements of calibrated backscatter, using two continuous wave Doppler lidars operating at wavelengths 9.1 and 10.6 micrometers were obtained along with cloud particle size distributions in Hurricane Juliette on 21 September 1995 at altitude approximately 11.7 km. Agreement between backscatter from the two lidars and with the cloud particle size distribution is excellent. Features in backscatter and particle number density compare well with concurrent GOES-7 infrared images.

  15. Characterization of polycrystals with elongated duplex microstructure by inversion of ultrasonic backscattering data

    SciTech Connect

    Lobkis, O. I.; Rokhlin, S. I.

    2010-04-19

    In this letter a simple analytical ultrasonic backscattering model is proposed for determination of characteristic microstructural scales in polycrystalline materials with elongated grains. The inversion methodology for microstructural parameters is based on backscattering coefficient ratios measured in different propagation directions. The ultrasonic backscattering measurements were performed on a Ti alloy sample with a duplex microstructure and the model was applied to experimental data inversion to size the material microtexture.

  16. Ocean Acoustic Observatory Federation

    DTIC Science & Technology

    2001-09-30

    J., C. G. Fox, and F. K. Duennebier, Hydroacoustic detection of submarine landslides on Kilauea volcano , Geophys. Res. Lett., vol. 28, 1811-1814...acoustic tomography experiments in the vicinity of coastal North America, • Monitor, in real time, marine mammals, earthquakes and volcanoes in the...distances, coastal tomography and thermometry, and earthquakes and volcanoes in the northern Pacific. APPROACH The members of the Ocean Acoustic

  17. Numerical Techniques in Acoustics

    NASA Technical Reports Server (NTRS)

    Baumeister, K. J. (Compiler)

    1985-01-01

    This is the compilation of abstracts of the Numerical Techniques in Acoustics Forum held at the ASME's Winter Annual Meeting. This forum was for informal presentation and information exchange of ongoing acoustic work in finite elements, finite difference, boundary elements and other numerical approaches. As part of this forum, it was intended to allow the participants time to raise questions on unresolved problems and to generate discussions on possible approaches and methods of solution.

  18. The neonatal acoustic reflex.

    PubMed

    Weatherby, L A; Bennett, M J

    1980-01-01

    Probe tones from 220 Hz to 2 000 Hz were used to measure the static and dynamic acoustic impedance of 44 neonates. Acoustic reflex thresholds to broad band noise were obtained from every neonate tested when employing the higher frequency probe tones. The reflex threshold levels measured are similar to those of adults. The static impedance values are discussed to give a possible explanation of why reflex thresholds cannot be detected using conventional 220 Hz impedance bridges.

  19. Directional Acoustic Density Sensor

    DTIC Science & Technology

    2010-09-13

    fluctuations of fluid density at a point . (2) DESCRIPTION OF THE PRIOR ART [0004] Conventional vector sensors measure particle velocity, v (vx,Vytvz...dipole-type or first order sensor that is realized by measuring particle velocity at a point , (which is the vector sensor sensing approach for...underwater sensors), or by measuring the gradient of the acoustic pressure at two closely spaced (less than the wavelength of an acoustic wave) points as it

  20. Low Frequency Acoustics

    DTIC Science & Technology

    2016-06-13

    with NOAA , ONR is providing technical services that will help establish a baseline for assessment of long- term VLF acoustic trends in selected...ABSTRACT unclassified c. THIS PAGE unclassified Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18 sponsored by NOAA , was added to the...with NOAA (NMFS) and other parties has dealt with ocean acoustics related to issues stimulated by the Marine Mammal Protection Act. A focal point has

  1. AB INITIO AND CALPHAD THERMODYNAMICS OF MATERIALS

    SciTech Connect

    Turchi, P A

    2004-04-14

    Ab initio electronic structure methods can supplement CALPHAD in two major ways for subsequent applications to stability in complex alloys. The first one is rather immediate and concerns the direct input of ab initio energetics in CALPHAD databases. The other way, more involved, is the assessment of ab initio thermodynamics {acute a} la CALPHAD. It will be shown how these results can be used within CALPHAD to predict the equilibrium properties of multi-component alloys.

  2. Acoustic Scattering by an Heterogeneous River Bed: Relationship to Bathymetry and Implications for Sediment Classification using Multibeam Echosounder Data

    NASA Astrophysics Data System (ADS)

    Buscombe, D.; Grams, P. E.; Kaplinski, M. A.

    2013-12-01

    Bed sediment classification using backscatter intensities from multibeam echosounder (MBES) systems in rivers is attractive due to its high coverage and resolution, limited costs compared to conventional sampling, and the potential combination of bathymetric and bottom sediment mapping in one instrument. Sediment classification by means of hydro-acoustic remote sensing is becoming an established discipline in oceanography. A number of techniques have been proposed, none of which has become the preferred method. In rivers, however, the field is relatively new and faces challenges not typically encountered in deep ocean settings. For example, river beds tend to have larger mean and maximum slopes than typical seabeds. Shallow water depths not only make MBES deployments more difficult, but also make the size of the beam footprint on the bed small which can lead to relatively noisy backscatter data. In particular, sediments can more heterogeneous in terms of: 1) range of particle sizes (both in a given area and over an entire mapped reach); 2) range of grain size over proximal bedform fields; 3) superimposed bedforms; and 4) abrupt sedimentological transitions over small scales. This sediment heterogeneity means grain-size usually changes along swath, which has a number of implications for existing sediment classification methods which use the distribution of backscatter intensities over all acoustic beams. We discuss these implications with reference to MBES data collected from the Colorado River in Grand Canyon, Arizona. We analyze the scale-dependence of probability density functions (PDF) of measured elevations in different sedimentological settings, which reveals the appropriate spatial scale at which to apply acoustic scattering theories. We also discuss the joint PDF of elevation and backscatter over different scales as a means by which to create an adaptive gridding scheme in which each grid is scaled appropriately, in situations with rapidly changing

  3. Pacific Hake Characteristics Affecting the Conduct of an Acoustic Clutter Experiment off the West Coast of the United States

    DTIC Science & Technology

    2012-07-04

    the assessment process. Echo sounder /trawl surveys of hake have been conducted by the National Marine Fisheries Service (NMFS) since 1977 to assess...3] There will be an NMFS hake survey in 2012. [20] The echo sounder /trawl method uses echo sounders to measure the total acoustic backscattering...NMFS echo sounder /trawl surveys have focused on fish age two or greater. Age-1 hake are generally more southerly and closer to shore than adults and

  4. Ocean acoustic reverberation tomography.

    PubMed

    Dunn, Robert A

    2015-12-01

    Seismic wide-angle imaging using ship-towed acoustic sources and networks of ocean bottom seismographs is a common technique for exploring earth structure beneath the oceans. In these studies, the recorded data are dominated by acoustic waves propagating as reverberations in the water column. For surveys with a small receiver spacing (e.g., <10 km), the acoustic wave field densely samples properties of the water column over the width of the receiver array. A method, referred to as ocean acoustic reverberation tomography, is developed that uses the travel times of direct and reflected waves to image ocean acoustic structure. Reverberation tomography offers an alternative approach for determining the structure of the oceans and advancing the understanding of ocean heat content and mixing processes. The technique has the potential for revealing small-scale ocean thermal structure over the entire vertical height of the water column and along long survey profiles or across three-dimensional volumes of the ocean. For realistic experimental geometries and data noise levels, the method can produce images of ocean sound speed on a smaller scale than traditional acoustic tomography.

  5. Effects of soil and canopy characteristics on microwave backscattering of vegetation

    NASA Technical Reports Server (NTRS)

    Daughtry, C. S. T.; Ranson, K. J.

    1991-01-01

    A frequency modulated continuous wave C-band (4.8 GHz) scatterometer was mounted on an aerial lift truck and backscatter coefficients of corn were acquired as functions of polarizations, view angles, and row directions. As phytomass and green leaf area index increased, the backscatter also increased. Near anthesis when the canopies were fully developed, the major scattering elements were located in the upper 1 m of the 2.8 m tall canopy and little backscatter was measured below that level. C-band backscatter data could provide information to monitor vegetation at large view zenith angles.

  6. Ab initio Thermal Transport in Compound Semiconductors

    DTIC Science & Technology

    2013-04-02

    Appendix). Important phonon scattering processes of the type acoustic + acoustic ↔ optic ( aao ) are completely forbidden by energy conservation due to the...with increasing temperature than κpure for AlAs and AlSb due to stronger aao scattering in AlP as optic phonons are increasingly thermally populated. At...than typical acoustic phonons. Since aao and ooo scattering channels are completely forbidden by energy conservation, aoo scattering provides the only

  7. Averaged indicators of secondary flow in repeated acoustic Doppler current profiler crossings of bends

    USGS Publications Warehouse

    Dinehart, R.L.; Burau, J.R.

    2005-01-01

    [1] Cross-stream velocity was measured in a large river bend at high spatial resolution over three separate survey episodes. A suite of methods for resolving cross-stream velocity distributions was tested on data collected using acoustic Doppler current profilers (ADCP) in the sand-bedded Sacramento River, California. The bend was surveyed with repeated ADCP crossings at eight cross sections during a rising limb of high discharge in February 2004 and twice on recession in March 2004. By translating and interpolating repeated ADCP crossings to planar grids, velocity ensembles at similar positions along irregular boat paths could be averaged. The averaging minimized turbulent fluctuations in streamwise velocities over 1 m/s, enabling the resolution of weaker cross-stream velocities (???15-30 cm/s). Secondary-flow influence on suspended sediment was inferred from a lateral region of acoustic backscatter intensity aligned with outward flow over the point bar. A near-bed decrease in backscatter intensity across the pool corresponded with inward cross-stream flow. These suspension indicators were used to orient averaged velocity grids for unambiguously defining the cross-stream velocity magnitudes. Additional field investigations could test whether the correlation between cross-stream velocity and backscatter intensity patterns results from helical recirculation of suspended sediment to the inside of the bend. These river measurements, consistent with classic and recent laboratory studies, show that ADCP surveys can provide refined views of secondary flow and sediment movement in large rivers.

  8. Automatic backscatter analysis of regional left ventricular systolic function using color kinesis.

    PubMed

    Schwartz, S L; Cao, Q L; Vannan, M A; Pandian, N G

    1996-06-15

    Assessment of regional wall motion by 2-dimensional echocardiography can be performed by either semiquantitative wall motion scoring or by quantitative analysis. The former is subjective and requires expertise. Quantitative methods are too time-consuming for routine use in a busy clinical laboratory. Color kinesis is a new algorithm utilizing acoustic backscatter analysis. It provides a color encoded map of endocardial motion in real time. In each frame a new color layer is added; the thickness of the color beam represents endocardial motion during that frame. The end-systolic image has multiple color layers, representing regional and temporal heterogeneity of segmental motion. The purpose of this study was to validate the use of color kinesis for semiquantitative analysis of regional left ventricular systolic function and quantitatively in measurement of endocardial excursion. Semiquantitative wall motion scoring was performed in 18 patients using both 2-dimensional echo and color kinesis. Scoring was identical in 74% of segments; there was 84% agreement in definition of normal vs. abnormal. There was less interobserver variability in wall motion scoring using color kinesis. Endocardial excursion was quantified in 21 patients. 70% of the imaged segments were suitable for analysis. Correlation between 2-dimensional echocardiographic measurements and color kinesis was excellent, r = 0.87. The mean difference in excursion as measured by the 2 methods was -0.05 +/- 2.0 mm. In conclusion, color kinesis is a useful method for assessing regional contraction by displaying a color map of systolic endocardial excursion. This algorithm may improve the confidence and accuracy of assessment of segmental ventricular function by echocardiographic methods.

  9. Review of Quantitative Ultrasound: Envelope Statistics and Backscatter Coefficient Imaging and Contributions to Diagnostic Ultrasound.

    PubMed

    Oelze, Michael L; Mamou, Jonathan

    2016-02-01

    Conventional medical imaging technologies, including ultrasound, have continued to improve over the years. For example, in oncology, medical imaging is characterized by high sensitivity, i.e., the ability to detect anomalous tissue features, but the ability to classify these tissue features from images often lacks specificity. As a result, a large number of biopsies of tissues with suspicious image findings are performed each year with a vast majority of these biopsies resulting in a negative finding. To improve specificity of cancer imaging, quantitative imaging techniques can play an important role. Conventional ultrasound B-mode imaging is mainly qualitative in nature. However, quantitative ultrasound (QUS) imaging can provide specific numbers related to tissue features that can increase the specificity of image findings leading to improvements in diagnostic ultrasound. QUS imaging can encompass a wide variety of techniques including spectral-based parameterization, elastography, shear wave imaging, flow estimation, and envelope statistics. Currently, spectral-based parameterization and envelope statistics are not available on most conventional clinical ultrasound machines. However, in recent years, QUS techniques involving spectral-based parameterization and envelope statistics have demonstrated success in many applications, providing additional diagnostic capabilities. Spectral-based techniques include the estimation of the backscatter coefficient (BSC), estimation of attenuation, and estimation of scatterer properties such as the correlation length associated with an effective scatterer diameter (ESD) and the effective acoustic concentration (EAC) of scatterers. Envelope statistics include the estimation of the number density of scatterers and quantification of coherent to incoherent signals produced from the tissue. Challenges for clinical application include correctly accounting for attenuation effects and transmission losses and implementation of QUS on

  10. Observations of HF backscatter decay rates from HAARP generated FAI

    NASA Astrophysics Data System (ADS)

    Bristow, William; Hysell, David

    2016-07-01

    Suitable experiments at the High-frequency Active Auroral Research Program (HAARP) facilities in Gakona, Alaska, create a region of ionospheric Field-Aligned Irregularities (FAI) that produces strong radar backscatter observed by the SuperDARN radar on Kodiak Island, Alaska. Creation of FAI in HF ionospheric modification experiments has been studied by a number of authors who have developed a rich theoretical background. The decay of the irregularities, however, has not been so widely studied yet it has the potential for providing estimates of the parameters of natural irregularity diffusion, which are difficult measure by other means. Hysell, et al. [1996] demonstrated using the decay of radar scatter above the Sura heating facility to estimate irregularity diffusion. A large database of radar backscatter from HAARP generated FAI has been collected over the years. Experiments often cycled the heater power on and off in a way that allowed estimates of the FAI decay rate. The database has been examined to extract decay time estimates and diffusion rates over a range of ionospheric conditions. This presentation will summarize the database and the estimated diffusion rates, and will discuss the potential for targeted experiments for aeronomy measurements. Hysell, D. L., M. C. Kelley, Y. M. Yampolski, V. S. Beley, A. V. Koloskov, P. V. Ponomarenko, and O. F. Tyrnov, HF radar observations of decaying artificial field aligned irregularities, J. Geophys. Res. , 101, 26,981, 1996.

  11. Classification of kidney and liver tissue using ultrasound backscatter data

    NASA Astrophysics Data System (ADS)

    Aalamifar, Fereshteh; Rivaz, Hassan; Cerrolaza, Juan J.; Jago, James; Safdar, Nabile; Boctor, Emad M.; Linguraru, Marius G.

    2015-03-01

    Ultrasound (US) tissue characterization provides valuable information for the initialization of automatic segmentation algorithms, and can further provide complementary information for diagnosis of pathologies. US tissue characterization is challenging due to the presence of various types of image artifacts and dependence on the sonographer's skills. One way of overcoming this challenge is by characterizing images based on the distribution of the backscatter data derived from the interaction between US waves and tissue. The goal of this work is to classify liver versus kidney tissue in 3D volumetric US data using the distribution of backscatter US data recovered from end-user displayed Bmode image available in clinical systems. To this end, we first propose the computation of a large set of features based on the homodyned-K distribution of the speckle as well as the correlation coefficients between small patches in 3D images. We then utilize the random forests framework to select the most important features for classification. Experiments on in-vivo 3D US data from nine pediatric patients with hydronephrosis showed an average accuracy of 94% for the classification of liver and kidney tissues showing a good potential of this work to assist in the classification and segmentation of abdominal soft tissue.

  12. Nimbus 7 solar backscatter ultraviolet (SBUV) ozone products user's guide

    NASA Technical Reports Server (NTRS)

    Fleig, Albert J.; Mcpeters, R. D.; Bhartia, P. K.; Schlesinger, Barry M.; Cebula, Richard P.; Klenk, K. F.; Taylor, Steven L.; Heath, Donald F.

    1990-01-01

    Three ozone tape products from the Solar Backscatter Ultraviolet (SBUV) experiment aboard Nimbus 7 were archived at the National Space Science Data Center. The experiment measures the fraction of incoming radiation backscattered by the Earth's atmosphere at 12 wavelengths. In-flight measurements were used to monitor changes in the instrument sensitivity. Total column ozone is derived by comparing the measurements with calculations of what would be measured for different total ozone amounts. The altitude distribution is retrieved using an optimum statistical technique for the inversion. The estimated initial error in the absolute scale for total ozone is 2 percent, with a 3 percent drift over 8 years. The profile error depends on latitude and height, smallest at 3 to 10 mbar; the drift increases with increasing altitude. Three tape products are described. The High Density SBUV (HDSBUV) tape contains the final derived products - the total ozone and the vertical ozone profile - as well as much detailed diagnostic information generated during the retrieval process. The Compressed Ozone (CPOZ) tape contains only that subset of HDSBUV information, including total ozone and ozone profiles, considered most useful for scientific studies. The Zonal Means Tape (ZMT) contains daily, weekly, monthly and quarterly averages of the derived quantities over 10 deg latitude zones.

  13. Almost perfect sequences applied for ionospheric oblique backscattering detection

    NASA Astrophysics Data System (ADS)

    Chen, Gang; Zhao, Zhengyu; Pu, Tianyao; Huang, Yujie; Zhu, Guoqiang

    2009-10-01

    Pseudorandom sequences are often used in radio systems; however, the nonzero out-of-phase autocorrelation of many binary sequences induces range sidelobes which significantly reduce the echo signal-to-noise ratio (SNR). In this paper, the use of almost perfect sequences, exhibiting zero out-of-phase autocorrelation except one value in the middle is examined with reference to common m sequences and perfect sequence. The ambiguity functions demonstrate that it is possible to use the almost perfect sequences for ranging without sidelobes and that their Doppler measurement performance is similar to m sequence of the same length. This is an important result for ionospheric oblique backscattering detection where the echoes are superposed and where range sidelobes can submerge the main lobes of weak signals. The 124-bit almost perfect sequence and the 127-bit m sequence are applied to the Wuhan Ionospheric Oblique Backscattering Sounding System for sequence testing. The test results have proven that the almost perfect sequence exhibits a higher echo SNR for the same detection conditions.

  14. Noninvasive fluid flow measurements in microfluidic channels with backscatter interferometry.

    PubMed

    Markov, Dmitry A; Dotson, Stephen; Wood, Scott; Bornhop, Darryl J

    2004-11-01

    The ability to measure fluid velocity within picoliter volumes or on-chip noninvasively, is important toward fully realizing the potential of microfluidics and micrototal analysis systems, particularly in applications such as micro-high-performance liquid chromatography (HPLC) or in metering mixing where the flow rate must be quantified. Additionally, these measurements need to be performed directly on moving fluids in a noninvasive fashion. We presented here the proof of principle experiments showing nonintrusive fluid flow measurements can be accomplished on-chip using a pump and probe configuration with backscattering interferometry. The on-chip interferometric backscatter detector (OCIBD) is based on a fiber-coupled HeNe laser that illuminates a portion of an isotropically etched 40 microm radius channel and a position sensitive transducer to measure fringe pattern shifts. An infrared laser with a mechanical shutter is used to heat a section of a flowing volume and the resulting refractive index (RI) change is detected with the OCIBD downstream as a time-dependent RI perturbation. Fluid velocity is quantified as changes in the phase difference between the shutter signal and the OCIBD detected signal in the Fourier domain. The experiments are performed in the range of 3-6 microL/h with 3sigma detection limits determined to be 0.127 nL/s. Additionally, the RI response of the system is calibrated using temperature changes as well as glycerol solutions.

  15. X-band microwave backscattering from ocean waves

    SciTech Connect

    Lee, P.H.Y.; Barter, J.D.; Beach, K.L.

    1994-01-04

    Backscattering experiments at microwave frequencies were conducted off the west coast of Scotland in the summer of 1991. Using a dual-polarization, 8-frequency X-band coherent scatterometer mounted on the bow of a boat, we measured time-resolved backscattering from ocean waves at a range of grazing angles from 10{degrees} to 70{degrees}. From the grazing-angle-dependent signals and their Doppler spectra, we differentiate Bragg scattering from non-Bragg scattering and resolve ``peak separation`` between the vertical and horizontal polarizations. We observe instances of ``super`` events, i.e., instances when the horizontal polarization return power equals or exceeds the vertical polarization power. We find that ``super`` events occur not only at low grazing angles but at any grazing angle for against-wind viewing directions. Statistics for such occurrences as a function of grazing angle are obtained. We study the coherence properties of scatterers and find strong evidence that at low grazing angles, lifetime-dominated, non-Bragg scattering contributes noticeably to returns of both polarizations, but is dominant in providing returns for the horizontal polarization. We examine ``spiking`` events and find that they can be related to, but need not be limited to, breaking wave events. By comparing the data of against-wind runs with cross-wind and circle runs, we obtain wind-direction dependence of Doppler spectra which further assists in the identification of scattering mechanisms.

  16. Feasibility of using Backscattered Mueller Matrix Images for Bioaerosol Detection

    NASA Astrophysics Data System (ADS)

    Li, Changhui; Kattawar, George W.

    2006-03-01

    It has been shown that by looking at the backscattered radiance from an object illuminated by a laser beam one could effectively distinguish different morphologies from one another. However, if one wants to obtain all the information possible from elastic scattering either from a single particle or an ensemble of particles then one must use the Mueller matrix which contains all the polarization and radiance information available. In this talk, we will show that if we take advantage of the polarization information of the object, many more images related to the overall morphology as well as the internal structure of the object can be obtained. We will present images of the complete Mueller matrix to show the sensitivity of its sixteen components to both external and internal particle properties. We will also show that by using only one or two elements of this matrix one might be able to distinguish bioaerosols such as anthrax from more benign aerosols. We also show that the backscattering Mueller images contain more information than the forward scattering ones.

  17. Measuring and modeling the backscattering cross section of a leaf

    NASA Technical Reports Server (NTRS)

    Senior, T. B. A.; Sarabandi, K.; Ulaby, F. T.

    1987-01-01

    Leaves are a significant feature of any vegetation canopy, and for remote sensing purposes it is important to develop an effective model for predicting the scattering from a leaf. From measurements of the X band backscattering cross section of a coleus leaf in varying stages of dryness, it is shown that a uniform resistive sheet constitutes such a model for a planar leaf. The scattering is determined by the (complex) resistivity which is, in turn, entirely specified by the gravimetric moisture content of the leaf. Using an available asymptotic expression for the scattering from a rectangular resistive plate which includes, as a special case, a metallic plate whose resistivity is zero, the computed backscattering cross sections for both principal polarizations are found to be in excellent agreement with data measured for rectangular sections of leaves with different moisture contents. If the resistivity is sufficiently large, the asymptotic expressions do not differ significantly from the physical optics ones, and for naturally shaped leaves as well as rectangular sections, the physical optics approximation in conjunction with the resistive sheet model faithfully reproduces the dominant feataures of the scattering patterns under all moisture conditions.

  18. Terrain-analysis procedures for modeling radar backscatter

    USGS Publications Warehouse

    Schaber, Gerald G.; Pike, Richard J.; Berlin, Graydon Lennis

    1978-01-01

    The collection and analysis of detailed information on the surface of natural terrain are important aspects of radar-backscattering modeling. Radar is especially sensitive to surface-relief changes in the millimeter- to-decimeter scale four conventional K-band (~1-cm wavelength) to L-band (~25-cm wavelength) radar systems. Surface roughness statistics that characterize these changes in detail have been generated by a comprehensive set of seven programmed calculations for radar-backscatter modeling from sets of field measurements. The seven programs are 1) formatting of data in readable form for subsequent topographic analysis program; 2) relief analysis; 3) power spectral analysis; 4) power spectrum plots; 5) slope angle between slope reversals; 6) slope angle against slope interval plots; and 7) base length slope angle and curvature. This complete Fortran IV software package, 'Terrain Analysis', is here presented for the first time. It was originally developed a decade ago for investigations of lunar morphology and surface trafficability for the Apollo Lunar Roving Vehicle.

  19. Radar Backscatter and Coherence Information Supporting High Quality Urban Mapping

    NASA Astrophysics Data System (ADS)

    Fischer, P.; Perski, Z.; Wannemacher, S.

    2004-06-01

    The potential of a synergetic use of different data sources for a high quality mapping of urban features is described in this paper. In the urban application domain, beside the different EO-sensors and products there are a lot of high resolution and high quality GIS- and digital map databases available (e.g. ATKIS in Germany), provided by public authorities but also by private industry. Fusing this ground-based data with remotely sensed information is resulting in high quality thematic datasets. Using ATKIS Geodata, IKONOS multispectral- and ERS-SAR / ENVISAT-ASAR data as input, in the research described we implemented a GIS-based expert system to derive in a first step the degree of sealing in the regions of interest (ROI). Joining the reclassified ATKIS-data with a vegetation index, the backscatter- and the coherence information, the output of the processing chain is a vector data layer dividing the ROI in different classes of sealing. Adding the SAR-/ASAR derived backscatter and coherence data into the spatial analysis results in a partial improvement of the classification process, especially in rural areas.

  20. Assembly for Rutherford backscattering at exactly 180{degree}

    SciTech Connect

    Ellmer, H.; Fischer, W.; Klose, A.; Semrad, D.

    1996-05-01

    We describe a facility which allows us to measure projectiles scattered at an angle arbitrarily near 180{degree}. The backscattered projectiles are deflected in the horizontal plane out of the incoming beam by a combination of electric and magnetic fields. The charged particles, which are spatially dispersed according to their energy, are detected by a cooled 300 mm{sup 2} ion implanted silicon detector. By a judicious choice of the relative strength of both fields we ensure that the essential parts of the spectrum will not be distorted due to an energy dependent percentage of projectiles missing the detector. As the projectiles are also dispersed according to their charge state we are able to distinguish between, e.g., singly and doubly charged He projectiles as they hit the detector at different positions. The detector can be moved in the vertical direction to continuously vary the backscattering angle between 180{degree} and 178.5{degree}. This experimental result shows for the first time the angular range to which the 180{degree} enhancement is confined. Such a device is ideally suited for investigating single crystals by uniaxial channeling blocking. {copyright} {ital 1996 American Institute of Physics.}

  1. Investigation of microwave backscatter from the air-sea interface

    NASA Technical Reports Server (NTRS)

    Mcintosh, Robert E.; Carswell, James R.

    1995-01-01

    Monitoring the ocean surface winds and mean ocean surface level is essential for improving our knowledge of the climate. Two instruments that may provide us with this information are satellite-based scatterometers and altimeters. However, these instruments measure the backscatter characteristics of the ocean surface from which other physical parameters, such as the wind speed or ocean surface height, are derived. To improve the algorithms or models that relate the electromagnetic backscatter to the desired physical parameters, the University of Massachusetts (UMass) Microwave Remote Sensing Laboratory (MIRSL) designed and fabricated three airborne scatterometers: a C-band scatterometer (CSCAT), Ku-band scatterometer (KUSCAT) and C/Ku-band scatterometer (EMBR). One or more of these instruments participated in the Electromagnetic Bias experiment (EM Bias), Shelf Edge Exchange Processes experiment (SEEP), Surface Wave Dynamics Experiment (SWADE), Southern Ocean Wave Experiment (SOWEX), Hurricane Tina research flights, Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE), and Ladir In-space Technology Experiment (LITE). This document describes the three scatterometers, summarizes our measurement campaigns and major contributions to the scientific and engineering communities, lists the publications that resulted, and presents the degrees earned under the support of this NASA grant.

  2. Coherent Effects in Microwave Backscattering Models for Forrest Canopies

    NASA Technical Reports Server (NTRS)

    Saatchi, Sasan S.; McDonald, Kyle C.

    1997-01-01

    In modeling forest canopies, several scattering mechanisms are taken into account: (1) volume scattering; (2) surface-volume interaction; and (3) surface scattering from forest floor. Depending on the structural and dielectric characteristics of forest canopies, the relative contribution of each mechanism in the total backscatter signal of an imaging radar can vary. In this paper, two commonly used first-order discrete scattering models, distorted born approximation (DBA) and radiative transfer (RT) are used to simulate the backscattered power received by polarimetric radars at P-, L-, and C-bands over coniferous and deciduous forests. The difference between the two models resides on the coherent effect in the surface-volume interaction terms. To demonstrate this point, the models are first compared based on their underlying theoretical assumptions and then according to simulation results over coniferous and deciduous forests. It is shown that by using the same scattering functions for various components of trees (i.e., leaf, branch, stem), the radiative transfer and distorted Born models are equivalent, except in low frequencies, where surface-volume interaction terms may become important, and the coherent contribution may be significant. In this case, the difference between the two models can reach up to 3 dB in both co-polarized and cross-polarized channels, which can influence the performance of retrieval algorithms.

  3. Backscatter Mossbauer Spectrometer (BaMS) for extraterrestrial applications

    NASA Astrophysics Data System (ADS)

    Agresti, D. G.; Shelfer, T. D.; Pimperl, M. M.; Wills, E. L.; Shen, M. H.; Morris, R. V.

    1993-06-01

    Mossbauer spectroscopy is a nuclear gamma resonance technique particularly well suited to the study of materials that contain iron (Fe-57). It can provide information on the oxidation state of iron as well as the type and proportion of iron-containing mineral species in a sample of interest. Iron Mossbauer spectroscopy (FeMS) has been applied to samples believed to have come from Mars (SNC meteorites) and has been helpful in refining the choice among putative Martian surface materials by suggesting a likely nanophase component of the Martian regolity. FeMS spectrum of a Martial analogue material (Hawaiian palagonite) is shown; it is dominated by ferric-bearing phases and shows evidence of a nanophase component. FeMS has also been applied to lunar materials. It can be used to measure the maturity of lunar surface material and has been proposed as a prospector for lunar ilmenite, an oxygen resource mineral. Several years ago we suggested a backscatter Mossbauer spectrometer (BaMS) for a Mars rover mission. Backscatter design was selected as most appropriate for in-situ application because no sample preparation is required. Since that time, we have continued to develop the BaMS instrument in anticipation that it would eventually find a home on a NASA planetary mission. Gooding proposed BaMS as a geochemistry instrument on MESUR. More recently, an LPI workshop has recommended that BaMS be included in a three-instrument payload on the next (1996?) lunar lander.

  4. Backscattering measuring system for optimization of intravenous laser irradiation dose

    NASA Astrophysics Data System (ADS)

    Rusina, Tatyana V.; Popov, V. D.; Melnik, Ivan S.; Dets, Sergiy M.

    1996-11-01

    Intravenous laser blood irradiation as an effective method of biostimulation and physiotherapy becomes a more popular procedure. Optimal irradiation conditions for each patient are needed to be established individually. A fiber optics feedback system combined with conventional intravenous laser irradiation system was developed to control of irradiation process. The system consists of He-Ne laser, fiber optics probe and signal analyzer. Intravenous blood irradiation was performed in 7 healthy volunteers and 19 patients with different diseases. Measurements in vivo were related to in vitro blood irradiation which was performed in the same conditions with force-circulated venous blood. Comparison of temporal variations of backscattered light during all irradiation procedures has shown a strong discrepancy on optical properties of blood in patients with various health disorders since second procedure. The best cure effect was achieved when intensity of backscattered light was constant during at least five minutes. As a result, the optical irradiation does was considered to be equal 20 minutes' exposure of 3 mW He-Ne laser light at the end of fourth procedure.

  5. Detection of Explosive Devices using X-ray Backscatter Radiation

    NASA Astrophysics Data System (ADS)

    Faust, Anthony A.

    2002-09-01

    It is our goal to develop a coded aperture based X-ray backscatter imaging detector that will provide sufficient speed, contrast and spatial resolution to detect Antipersonnel Landmines and Improvised Explosive Devices (IED). While our final objective is to field a hand-held detector, we have currently constrained ourselves to a design that can be fielded on a small robotic platform. Coded aperture imaging has been used by the observational gamma astronomy community for a number of years. However, it has been the recent advances in the field of medical nuclear imaging which has allowed for the application of the technique to a backscatter scenario. In addition, driven by requirements in medical applications, advances in X-ray detection are continually being made, and detectors are now being produced that are faster, cheaper and lighter than those only a decade ago. With these advances, a coded aperture hand-held imaging system has only recently become a possibility. This paper will begin with an introduction to the technique, identify recent advances which have made this approach possible, present a simulated example case, and conclude with a discussion on future work.

  6. Backscatter Mossbauer Spectrometer (BaMS) for extraterrestrial applications

    NASA Technical Reports Server (NTRS)

    Agresti, D. G.; Shelfer, T. D.; Pimperl, M. M.; Wills, E. L.; Shen, M. H.; Morris, R. V.

    1993-01-01

    Mossbauer spectroscopy is a nuclear gamma resonance technique particularly well suited to the study of materials that contain iron (Fe-57). It can provide information on the oxidation state of iron as well as the type and proportion of iron-containing mineral species in a sample of interest. Iron Mossbauer spectroscopy (FeMS) has been applied to samples believed to have come from Mars (SNC meteorites) and has been helpful in refining the choice among putative Martian surface materials by suggesting a likely nanophase component of the Martian regolity. FeMS spectrum of a Martial analogue material (Hawaiian palagonite) is shown; it is dominated by ferric-bearing phases and shows evidence of a nanophase component. FeMS has also been applied to lunar materials. It can be used to measure the maturity of lunar surface material and has been proposed as a prospector for lunar ilmenite, an oxygen resource mineral. Several years ago we suggested a backscatter Mossbauer spectrometer (BaMS) for a Mars rover mission. Backscatter design was selected as most appropriate for in-situ application because no sample preparation is required. Since that time, we have continued to develop the BaMS instrument in anticipation that it would eventually find a home on a NASA planetary mission. Gooding proposed BaMS as a geochemistry instrument on MESUR. More recently, an LPI workshop has recommended that BaMS be included in a three-instrument payload on the next (1996?) lunar lander.

  7. Extinction and backscatter cross sections of biological materials

    NASA Astrophysics Data System (ADS)

    Thomas, M. E.; Hahn, D. V.; Carr, A. K.; Limsui, D.; Carter, C. C.; Boggs, N. T.; Jackman, J.

    2008-04-01

    Aerosol backscatter and extinction cross-sections are required to model and evaluate the performance of both active and passive detection systems. A method has been developed that begins with laboratory measurements of thin films and suspensions of biological material to obtain the complex index refraction of the biological material from the UV to the LWIR. Using that result with particle size distribution and shape information as inputs to T-matrix or discrete dipole approximation (DDA) calculations yields the extinction cross-section and backscatter cross section as a function of wavelength. These are important inputs to the lidar equation. In a continuing effort to provide validated optical cross-sections, measurements have been made on a number of high purity biological species in the laboratory as well as measurements of material released at recent field tests. The resulting observed differences between laboratory and field measurements aid in distinguishing between intrinsic and extrinsic effects, which can affect the characteristic signatures of important biological aerosols. A variety of biological and test aerosols are examined, including Bacillus atrophaeus (BG), and Erwina, ovalbumin, silica and polystyrene.

  8. Subgrid-scale backscatter after the shock-turbulence interaction

    NASA Astrophysics Data System (ADS)

    Livescu, Daniel; Li, Zhaorui

    2017-01-01

    The statistics of the subgrid scales (SGS) are studied in the context of Large Eddy Simulations (LES) of turbulence after the interaction with a nominally normal shock wave. In general, in practical applications, the shock wave width is much smaller than the turbulence scales and the upstream turbulent Mach number is modest. In this case, recent high resolution shock-resolved Direct Numerical Simulations (DNS) (Ryu and Livescu, J. Fluid Mech., 756, R1, 2014) show that the interaction can be described by the Linear Interaction Approximation (LIA). By using LIA to alleviate the need to resolve the shock wave, DNS post-shock data can be generated at much higher Reynolds numbers than previously possible. Here, such results with Taylor Reynolds number ≈ 180 are used for an analysis of the SGS backscatter properties. In particular, it is shown that the interaction with the shock wave decreases the asymmetry of the SGS dissipation Probability Density Function (PDF) as the shock Mach number increases, with a significant enhancement in size of the regions and magnitude of backscatter.

  9. Radar Backscatter Saturation with Forest Biomass: Facts and Myths

    NASA Astrophysics Data System (ADS)

    Saatchi, S. S.

    2012-12-01

    In recent years, climate change policies and scientific research created a widespread interest in quantify the carbon stock and changes of global forests extending from forest patches to national and regional scales. However, because of the large spatial extent of forests, their heterogeneity from structural and species diversity causing meters to kilometer scales variations, their complex dynamics causing landscape scale differences in changes of biomass, and their continues degradation from human activities, the quantification of forest biomass from conventional inventory data alone has become a major challenge. Remote sensing techniques with Lidar and Radar are considered to be the most efficient way of estimating forest biomass at large scales and with uncertainty comparable to estimation from inventory plots. Radar backscatter and interferometric based estimation of forest biomass has been studied extensively and considered as dedicated spaceborne options of monitoring and quantifying forest biomass. However, the literature on the radar-based estimation techniques of biomass has been misleading in defining the sensitivity and lack of sensitivity, so called saturation effect of radar measurements. In this paper, I provide results from a combination of observations and model simulations to demonstrate the physical nature of the loss of sensitivity of radar backscatter to biomass, examine the biophysical that impact the sensitivity, extend the results to other radar measurements including polarimetric and interferometric modes.

  10. Ab initio dynamical vertex approximation

    NASA Astrophysics Data System (ADS)

    Galler, Anna; Thunström, Patrik; Gunacker, Patrik; Tomczak, Jan M.; Held, Karsten

    2017-03-01

    Diagrammatic extensions of dynamical mean-field theory (DMFT) such as the dynamical vertex approximation (DΓ A) allow us to include nonlocal correlations beyond DMFT on all length scales and proved their worth for model calculations. Here, we develop and implement an Ab initio DΓ A approach (AbinitioDΓ A ) for electronic structure calculations of materials. The starting point is the two-particle irreducible vertex in the two particle-hole channels which is approximated by the bare nonlocal Coulomb interaction and all local vertex corrections. From this, we calculate the full nonlocal vertex and the nonlocal self-energy through the Bethe-Salpeter equation. The AbinitioDΓ A approach naturally generates all local DMFT correlations and all nonlocal G W contributions, but also further nonlocal correlations beyond: mixed terms of the former two and nonlocal spin fluctuations. We apply this new methodology to the prototypical correlated metal SrVO3.

  11. Acoustic droplet vaporization for diagnostic and therapeutic applications

    NASA Astrophysics Data System (ADS)

    Kripfgans, Oliver Daniel

    A technology, termed Acoustic Droplet Vaporization (ADV), is developed whereby superheated droplets are caused to vaporize by application of an ultrasonic field. The droplet emulsion (90% <6 um diameter) is made by mixing saline, albumin, and perfluorocarbon at high speed. It has been observed that an acoustic pressure threshold exists above which the droplets vaporize into bubbles approximately 25-times the original droplet diameter. For frequencies between 1.5 and 8 MHz, the threshold decreases from 4.5 to 0.75 MPa peak rarefactional pressure. The single pulse efficiency of ADV has been measured as 26%. This technology might be useful for tissue occlusion in cancer treatment as well as for aberration correction in acoustic imaging. To demonstrate these potential applications, gas bubbles were made in vivo in animal models by ADV. It was found that ADV could be used to temporarily form large gas bubbles (>30 um) in vivo, which at large number density occluded targeted tissues and reduced the blood flow by 34%. Alternatively, for a very sparse droplet population, gas bubbles could serve as potential point beacons for phase aberration correction given their backscatter amplitudes of 24 dB above tissue background. Other possible applications include drug delivery, indicator for cryo therapy, pressure/radiation beacons, hyperthermia, and cavitation nuclei. ADV of individual droplets showed that during acoustic irradiation, droplets perform dipole-type oscillations and that such oscillations increased in amplitude with acoustic intensity. Smaller droplets required more acoustic intensity for vaporization than larger droplets; however, independent of droplet diameter, a maximum oscillation amplitude of 1.3 um, was required. This threshold corresponds to a Reynolds number of ˜5 x 104. Vaporization started either as a spot on the axis of oscillation close to a pole of the droplet, or homogeneously throughout the droplet's imaged cross-section. It is concluded that

  12. Hydroacoustic detection of dumped ammunition in the Ocean with multibeam snippet backscatter analyses. A case study from the 'Kolberger Heide' ammunition dump site (Baltic Sea, Germany)

    NASA Astrophysics Data System (ADS)

    Kunde, Tina; Schneider von Deimling, Jens

    2016-04-01

    Dumped ammunition in the sea is a matter of great concern in terms of safe navigation and environmental threads. Because corrosion of the dumped ammunition's hull is ongoing, future contamination of the ambient water by their toxic interior is likely to occur. The location of such dump sites is approximately known from historical research and ship log book analyses. Subsequent remote sensing of ammunition dumping sites (e.g. mines) on the seafloor is preferentially performed with hydro-acoustic methods such as high resolution towed side scan or by the sophisticated synthetic aperture sonar approach with autonomous underwater vehicles. However, these are time consuming and expensive procedures, while determining the precise position of individual mines remains a challenging task. To mitigate these shortcomings we suggest using ship-born high-frequency multibeam sonar in shallow water to address the task of mine detection and precise localization on the seabed. Multibeam sonar systems have improved their potential in regard to backscatter analyses significantly over the past years and nowadays present fast and accurate tools for shallow water surveying to (1) detect mines in multibeam snippet backscatter data (2) determine their precise location with high accuracy intertial navigation systems. A case study was performed at the prominent ammunition dumping site 'Kolberger Heide' (Baltic Sea, Germany) in the year 2014 using a modern hydro-acoustic multibeam echosounder system with 200-400 kHz (KONGSBERG EM2040c). With an average water depth of not even 20 m and the proximity to the shore line and dense waterways, this investigated area requires permanent navigational care. Previously, the study area was surveyed by the Navy with the very sophisticated HUGIN AUV equipped with a synthetic aperture sonar with best resolution by current technology. Following an evaluation of the collected data, various ammunition bodies on the sea floor could be clearly detected. Analyses

  13. Ultrasound Biomicroscopy Comparison of Ab Interno and Ab Externo Intraocular Lens Scleral Fixation.

    PubMed

    Horiguchi, Lie; Garcia, Patricia Novita; Malavazzi, Gustavo Ricci; Allemann, Norma; Gomes, Rachel L R

    2016-01-01

    Purpose. To compare ab interno and ab externo scleral fixation of posterior chamber intraocular lenses (PCIOL) using ultrasound biomicroscopy (UBM). Methods. Randomized patients underwent ab externo or ab interno scleral fixation of a PCIOL. Ultrasound biomicroscopy was performed 3 to 6 months postoperatively, to determine PCIOL centration, IOL distance to the iris at 12, 3, 6, and 9 hours, and haptics placement in relation to the ciliary sulcus. Results. Fifteen patients were enrolled in the study. The ab externo technique was used in 7 eyes (46.6%) and the ab interno in 8 eyes (53.3%). In the ab externo technique, 14 haptics were located: 4 (28.57%) in the ciliary sulcus; 2 (14.28%) anterior to the sulcus; and 8 (57.14%) posterior to the sulcus, 6 in the ciliary body and 2 posterior to the ciliary body. In the ab interno group, 4 haptics (25.0%) were in the ciliary sulcus, 2 (12.50%) anterior to the sulcus, and 10 (75.0%) posterior to the sulcus, 4 in the ciliary body and 6 posterior to the ciliary body. Conclusions. Ab externo and ab interno scleral fixation techniques presented similar results in haptic placement. Ab externo technique presented higher vertical tilt when compared to the ab interno.

  14. Measuring acoustic habitats.

    PubMed

    Merchant, Nathan D; Fristrup, Kurt M; Johnson, Mark P; Tyack, Peter L; Witt, Matthew J; Blondel, Philippe; Parks, Susan E

    2015-03-01

    1. Many organisms depend on sound for communication, predator/prey detection and navigation. The acoustic environment can therefore play an important role in ecosystem dynamics and evolution. A growing number of studies are documenting acoustic habitats and their influences on animal development, behaviour, physiology and spatial ecology, which has led to increasing demand for passive acoustic monitoring (PAM) expertise in the life sciences. However, as yet, there has been no synthesis of data processing methods for acoustic habitat monitoring, which presents an unnecessary obstacle to would-be PAM analysts. 2. Here, we review the signal processing techniques needed to produce calibrated measurements of terrestrial and aquatic acoustic habitats. We include a supplemental tutorial and template computer codes in matlab and r, which give detailed guidance on how to produce calibrated spectrograms and statistical analyses of sound levels. Key metrics and terminology for the characterisation of biotic, abiotic and anthropogenic sound are covered, and their application to relevant monitoring scenarios is illustrated through example data sets. To inform study design and hardware selection, we also include an up-to-date overview of terrestrial and aquatic PAM instruments. 3. Monitoring of acoustic habitats at large spatiotemporal scales is becoming possible through recent advances in PAM technology. This will enhance our understanding of the role of sound in the spatial ecology of acoustically sensitive species and inform spatial planning to mitigate the rising influence of anthropogenic noise in these ecosystems. As we demonstrate in this work, progress in these areas will depend upon the application of consistent and appropriate PAM methodologies.

  15. Measuring acoustic habitats

    PubMed Central

    Merchant, Nathan D; Fristrup, Kurt M; Johnson, Mark P; Tyack, Peter L; Witt, Matthew J; Blondel, Philippe; Parks, Susan E

    2015-01-01

    1. Many organisms depend on sound for communication, predator/prey detection and navigation. The acoustic environment can therefore play an important role in ecosystem dynamics and evolution. A growing number of studies are documenting acoustic habitats and their influences on animal development, behaviour, physiology and spatial ecology, which has led to increasing demand for passive acoustic monitoring (PAM) expertise in the life sciences. However, as yet, there has been no synthesis of data processing methods for acoustic habitat monitoring, which presents an unnecessary obstacle to would-be PAM analysts. 2. Here, we review the signal processing techniques needed to produce calibrated measurements of terrestrial and aquatic acoustic habitats. We include a supplemental tutorial and template computer codes in matlab and r, which give detailed guidance on how to produce calibrated spectrograms and statistical analyses of sound levels. Key metrics and terminology for the characterisation of biotic, abiotic and anthropogenic sound are covered, and their application to relevant monitoring scenarios is illustrated through example data sets. To inform study design and hardware selection, we also include an up-to-date overview of terrestrial and aquatic PAM instruments. 3. Monitoring of acoustic habitats at large spatiotemporal scales is becoming possible through recent advances in PAM technology. This will enhance our understanding of the role of sound in the spatial ecology of acoustically sensitive species and inform spatial planning to mitigate the rising influence of anthropogenic noise in these ecosystems. As we demonstrate in this work, progress in these areas will depend upon the application of consistent and appropriate PAM methodologies. PMID:25954500

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

    NASA Astrophysics Data System (ADS)

    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

  17. Erythema ab igne: Usual site, unusual cause.

    PubMed

    Manoharan, D

    2015-04-01

    Erythema ab igne is reticular erythematous pigmented dermatoses seen in patients exposed to prolonged or repeated sub-threshold Infrared radiation inadequate to cause burns. Here, we report a case of erythema ab igne in a 40-year-old male patient seen over the abdomen due to prolonged laptop use.

  18. Acoustic emission monitoring system

    DOEpatents

    Romrell, Delwin M.

    1977-07-05

    Methods and apparatus for identifying the source location of acoustic emissions generated within an acoustically conductive medium. A plurality of acoustic receivers are communicably coupled to the surface of the medium at a corresponding number of spaced locations. The differences in the reception time of the respective sensors in response to a given acoustic event are measured among various sensor combinations prescribed by the monitoring mode employed. Acoustic reception response encountered subsequent to the reception by a predetermined number of the prescribed sensor combinations are inhibited from being communicated to the processing circuitry, while the time measurements obtained from the prescribed sensor combinations are translated into a position measurement representative of the location on the surface most proximate the source of the emission. The apparatus is programmable to function in six separate and five distinct operating modes employing either two, three or four sensory locations. In its preferred arrangement the apparatus of this invention will re-initiate a monitoring interval if the predetermined number of sensors do not respond to a particular emission within a given time period.

  19. Kinematics of Compton backscattering x-ray source for angiography

    SciTech Connect

    Blumberg, L.N.

    1992-05-01

    Calculations of X-Ray production rates, energy spread, and spectrum of Compton-backscattered photons from a Free Electron Laser on an electron beam in a low energy (136-MeV) compact (8.5-m circumference) storage ring indicate that an X-Ray intensity of 34.6 10{sup 7} X-Ray photons per 0.5-mm {times} 0.5-mm pixel for Coronary Angiography near the 33.169-keV iodine K-absorption edge can be achieved in a 4-msec pulse within a scattering cone of 1-mrad half angle. This intensity, at 10-m from the photon-electron interaction point to the patient is about a factor of 10 larger than presently achieved from a 4.5-T superconducting wiggler source in the NSLS 2.5-GeV storage ring and over an area about 5 times larger. The 2.2-keV energy spread of the Compton-backscattered beam is, however, much larger than the 70-eV spread presently attained form the wiggler source and use of a monochromator. The beam spot at the 10-m interaction point-to-patient distance is 20-mm diameter; larger spots are attainable at larger distances but with a corresponding reduction in X-Ray flux. Such a facility could be an inexpensive clinical alternative to present methods of non-invasive Digital Subtraction Angiography (DSA), small enough to be deployed in an urban medical center, and could have other medical, industrial and aerospace applications. Problems with the Compton backscattering source include laser beam heating of the mirror in the FEL oscillator optical cavity, achieving a large enough X-Ray beam spot at the patient, and obtaining radiation damping of the transverse oscillations and longitudinal emittance dilution of the storage ring electron beam resulting from photon-electron collisions without going to higher electron energy where the X-Ray energy spread becomes excessive for DSA. 38 refs.

  20. ACOUSTICS IN ARCHITECTURAL DESIGN, AN ANNOTATED BIBLIOGRAPHY ON ARCHITECTURAL ACOUSTICS.

    ERIC Educational Resources Information Center

    DOELLE, LESLIE L.

    THE PURPOSE OF THIS ANNOTATED BIBLIOGRAPHY ON ARCHITECTURAL ACOUSTICS WAS--(1) TO COMPILE A CLASSIFIED BIBLIOGRAPHY, INCLUDING MOST OF THOSE PUBLICATIONS ON ARCHITECTURAL ACOUSTICS, PUBLISHED IN ENGLISH, FRENCH, AND GERMAN WHICH CAN SUPPLY A USEFUL AND UP-TO-DATE SOURCE OF INFORMATION FOR THOSE ENCOUNTERING ANY ARCHITECTURAL-ACOUSTIC DESIGN…

  1. L-Band SAR Backscatter Prospects for Burn Severity Estimation in Boreal Forests

    NASA Astrophysics Data System (ADS)

    Tanase, Mihai; Santoro, Maurizio; de la Riva, Juan; Kasischke, Eric; Korets, Michael A.

    2010-12-01

    L-band Synthetic Aperture Radar (SAR) data has been investigated to establish the relationship between backscatter and burn severity in boreal forests. Advanced Land Observation Satellite (ALOS) Phased Array-type L-band Synthetic Aperture Radar (PALSAR) dual polarized images were available for the study of the backscattering coefficient at two locations. Statistical analysis was used to assess the average backscatter coefficient as a function of burn severity level after stratifying the data by local incidence angle. Determination coefficients were used to quantify the relationship between radar data and burn severity estimates. The analysis for a given range of local incidence angle showed that HH and HV polarized backscatter decreases with burn severity for both polarizations when images are acquired under dry environmental conditions. For data acquired under wet conditions HH polarized backscatter increased with burn severity. The higher backscatter of the severely burned areas was explained by the enhanced contribution of the ground component due to higher soil moisture content. Backscatter variation between burned and unburned forest was around 2-3 dB at HH polarization and around 3-6 dB at HV polarization. This study indicates that L- band SAR backscatter trend as a function of burn severity is not significantly different when compared to previously studied mediterranean forests.

  2. The relationship between strength of turbulence and backscattering radar power at HF and VHF

    NASA Technical Reports Server (NTRS)

    Hocking, W. K.

    1983-01-01

    The formulae relating turbulence and other atmospheric parameters to backscattered power for radar observations are reviewed. Emphasis is on the case of scatter from turbulent irregularities which have scales corresponding to the range of isotropic, inertial range turbulence. The applicability of this assumption is discussed. A formula is introduced for the mesosphere which relates ionospheric electron densities to backscattered power.

  3. Application of a coherent model in simulating the backscattering coefficient of a mangrove forest

    NASA Astrophysics Data System (ADS)

    Thirion, L.; Chênerie, I.; Galy, C.

    2004-04-01

    In this paper, a single scattering model is presented for a coherent forest scattering simulation. It is tested on the backscattering coefficient of mangrove forests, which are known to involve large coherent effects. Analysis of branches, leaves and ground contributions is done to understand the backscattering coefficient composition. Finally the sensitivity of the code is investigated.

  4. Identification of major backscattering sources in trees and shrubs at 10 GHz

    NASA Technical Reports Server (NTRS)

    Zoughi, R.; Wu, L. K.; Moore, R. K.

    1986-01-01

    A short-range very-fine-resolution FM-CW radar scatterometer has been used to identify the primary contributors to 10-GHz radar backscatter from pine, pin oak, American sycamore and sugar maple trees, and from creeping juniper shrubs. This system provided a range resolution of 11 cm and gave a 16-cm diameter illumination area at the target range of about 4 m. For a pine tree, the needles caused the strongest backscatter as well as the strongest attenuation in the radar signal. Cones, although insignificant contributors to the total backscatter, were more important for backscattering than for attenuation. For the rest of the trees, leaves were the strongest cause of backscattering and attenuation. However, in the absence of leaves, the petioles, small twigs, and branches gave relatively strong backscatter. For American sycamore and sugar maple trees, the fruits did not affect the total backscatter unless they were packed in clusters. For creeping juniper the backscattered energy and attenuation in the radar signal were mainly due to the top two layers of the evergreen scales. The contribution of the tree trunks was not determined.

  5. Effect of the cortex on ultrasonic backscatter measurements of cancellous bone.

    PubMed

    Hoffmeister, Brent K; Holt, Andrew P; Kaste, Sue C

    2011-10-07

    Ultrasonic backscatter techniques offer a promising new approach for detecting changes in bone caused by osteoporosis. However, several challenges impede clinical implementation of backscatter techniques. This study examines how the dense outer surface of bone (the cortex) affects backscatter measurements of interior regions of porous (cancellous) bone tissue. Fifty-two specimens of bone were prepared from 13 human femoral heads so that the same region of cancellous bone could be ultrasonically interrogated through the cortex or along directions that avoided the cortex. Backscatter signals were analyzed over a frequency range of 0.8-3.0 MHz to determine two ultrasonic parameters: apparent integrated backscatter (AIB) and frequency slope of apparent backscatter (FSAB). The term 'apparent' means that the parameters are sensitive to the frequency-dependent effects of diffraction and attenuation. Significant (p < 0.001) changes in AIB and FSAB indicated that measurements through the cortex decreased the apparent backscattered power and increased the frequency dependence of the power. However, the cortex did not affect the correlation of AIB and FSAB with the x-ray bone mineral density of the specimens. This suggests that results from many previous in vitro backscatter studies of specimens of purely cancellous bone may be extrapolated with greater confidence to in vivo conditions.

  6. Compton backscattering of intracavity storage ring free-electron laser radiation

    SciTech Connect

    Dattoli, G.; Giannessi, L.; Torre, A.

    1995-12-31

    We discuss the{gamma}-ray production by Compton backscattering of intracavity storage ring Free-Electron Laser radiation. We use a semi-analytical model which provides the build up of the signal combined with the storage ring damping mechanism and derive simple relations yielding the connection between backscattered. Photons brightness and the intercavity laser equilibrium intensity.

  7. A New Wave of Acoustics.

    ERIC Educational Resources Information Center

    Beyer, Robert

    1981-01-01

    Surveys 50 years of acoustical studies by discussing selected topics including the ear, nonlinear representations, underwater sound, acoustical diagnostics, absorption, electrolytes, phonons, magnetic interaction, and superfluidity and the five sounds. (JN)

  8. Passive broadband acoustic thermometry

    NASA Astrophysics Data System (ADS)

    Anosov, A. A.; Belyaev, R. V.; Klin'shov, V. V.; Mansfel'd, A. D.; Subochev, P. V.

    2016-04-01

    The 1D internal (core) temperature profiles for the model object (plasticine) and the human hand are reconstructed using the passive acoustothermometric broadband probing data. Thermal acoustic radiation is detected by a broadband (0.8-3.5 MHz) acoustic radiometer. The temperature distribution is reconstructed using a priori information corresponding to the experimental conditions. The temperature distribution for the heated model object is assumed to be monotonic. For the hand, we assume that the temperature distribution satisfies the heat-conduction equation taking into account the blood flow. The average error of reconstruction determined for plasticine from the results of independent temperature measurements is 0.6 K for a measuring time of 25 s. The reconstructed value of the core temperature of the hand (36°C) generally corresponds to physiological data. The obtained results make it possible to use passive broadband acoustic probing for measuring the core temperatures in medical procedures associated with heating of human organism tissues.

  9. Architectural-acoustics consulting

    NASA Astrophysics Data System (ADS)

    Hoover, Anthony K.

    2004-05-01

    Consulting involves both the science of acoustics and the art of communication, requiring an array of inherent and created skills. Perhaps because consulting on architectural acoustics is a relatively new field, there is a remarkable variety of career paths, all influenced by education, interest, and experience. Many consultants juggle dozens of chargeable projects at a time, not to mention proposals, seminars, teaching, articles, business concerns, and professional-society activities. This paper will discuss various aspects of career paths, projects, and clients as they relate to architectural-acoustics consulting. The intended emphasis will be considerations for those who may be interested in such a career, noting that consultants generally seem to thrive on the numerous challenges.

  10. High temperature acoustic levitator

    NASA Technical Reports Server (NTRS)

    Barmatz, M. B. (Inventor)

    1984-01-01

    A system is described for acoustically levitating an object within a portion of a chamber that is heated to a high temperature, while a driver at the opposite end of the chamber is maintained at a relatively low temperature. The cold end of the chamber is constructed so it can be telescoped to vary the length (L sub 1) of the cold end portion and therefore of the entire chamber, so that the chamber remains resonant to a normal mode frequency, and so that the pressure at the hot end of the chamber is maximized. The precise length of the chamber at any given time, is maintained at an optimum resonant length by a feedback loop. The feedback loop includes an acoustic pressure sensor at the hot end of the chamber, which delivers its output to a control circuit which controls a motor that varies the length (L) of the chamber to a level where the sensed acoustic pressure is a maximum.

  11. Basic Linear Acoustics

    NASA Astrophysics Data System (ADS)

    Pierce, Alan

    This chapter deals with the physical and mathematical aspects of sound when the disturbances are, in some sense, small. Acoustics is usually concerned with small-amplitude phenomena, and consequently a linear description is usually applicable. Disturbances are governed by the properties of the medium in which they occur, and the governing equations are the equations of continuum mechanics, which apply equally to gases, liquids, and solids. These include the mass, momentum, and energy equations, as well as thermodynamic principles. The viscosity and thermal conduction enter into the versions of these equations that apply to fluids. Fluids of typical great interest are air and sea water, and consequently this chapter includes a summary of their relevant acoustic properties. The foundation is also laid for the consideration of acoustic waves in elastic solids, suspensions, bubbly liquids, and porous media.

  12. Acoustic Liners for Turbine Engines

    NASA Technical Reports Server (NTRS)

    Jones, Michael G (Inventor); Grady, Joseph E (Inventor); Kiser, James D. (Inventor); Miller, Christopher (Inventor); Heidmann, James D. (Inventor)

    2016-01-01

    An improved acoustic liner for turbine engines is disclosed. The acoustic liner may include a straight cell section including a plurality of cells with straight chambers. The acoustic liner may also include a bent cell section including one or more cells that are bent to extend chamber length without increasing the overall height of the acoustic liner by the entire chamber length. In some cases, holes are placed between cell chambers in addition to bending the cells, or instead of bending the cells.

  13. Spacecraft Internal Acoustic Environment Modeling

    NASA Technical Reports Server (NTRS)

    Allen, Christopher; Chu, S. Reynold

    2008-01-01

    The objective of the project is to develop an acoustic modeling capability, based on commercial off-the-shelf software, to be used as a tool for oversight of the future manned Constellation vehicles to ensure compliance with acoustic requirements and thus provide a safe and habitable acoustic environment for the crews, and to validate developed models via building physical mockups and conducting acoustic measurements.

  14. Time-of-flight detector for heavy ion backscattering spectrometry

    SciTech Connect

    Knapp, J.A.; Banks, J.C.; Doyle, B.L.

    1994-04-01

    This report describes the results of a two-year laboratory directed research and development project to explore advanced concepts in Heavy Ion Backscattering Spectrometry (HIBS), undertaken with the goal of extending the sensitivity of this relatively new technique to levels unattainable by any other existing trace element surface analysis. Improvements in sensitivity are required for the application of HIBS to contamination control in the microelectronics industry. Tools with sensitivity approaching 10{sup 8} atoms/cm{sup 2} are expected to be essential for enabling advanced IC production by the year 2000. During the project the authors developed a new analysis chamber with channeling goniometer and a prototype time-of-flight detector with a demonstrated sensitivity of {approximately} 5 {times} 10{sup 8} atoms/cm{sup 2} for Au on Si and {approximately} 5 {times} 10{sup 10} for Fe, and sufficient mass resolution to separate contributions from Fe and Cu.

  15. Towards a Metric to Estimate Atomic Number from Backscattered Photons

    SciTech Connect

    Walston, S; Dietrich, D; Wurtz, R

    2009-08-17

    An ability to determine the atomic number of a material in a cargo container would be helpful in interdicting smuggled nuclear materials. This paper examines two processes by which high energy photons interact with matter; Compton scattering and pair production. The ratio of the number of photons which originate from the annihilation of positrons resulting from pair production and the number of photons coming from Compton scattering gives a good indication of atomic number. At large angles relative to an incident beam - i.e. backscattered, there is good separation in energy between Compton scattered photons and photons from positron annihilations. This ratio can then be cleanly determined in order to estimate atomic number.

  16. Studies of sidescatter and backscatter from pre-ionized plasmas

    NASA Astrophysics Data System (ADS)

    Herbst, M. J.; Clayton, C. E.; Peebles, W. A.; Chen, F. F.

    1980-07-01

    Stimulated Brillouin scattering at 180 deg and sidescatter at 90 deg are observed when CO2 laser light is incident on an arc-preionized, underdense plasma target. Scattering occurs in short spikes, sometimes early in the pulse, sometimes delayed by as much as 700 nsec. This time behavior depends critically on the state of preionization and is explained by the evolution of a laser-driven ionization wave. Using ruby laser interferometry, it is possible to infer the sources of backscatter and sidescatter within this disturbance. In addition, by using a smooth input pulse, it is found that the spikiness of Brillouin scatter is not due solely to mode beating in the input beam.

  17. Implementing Transmission Electron Backscatter Diffraction for Atom Probe Tomography.

    PubMed

    Rice, Katherine P; Chen, Yimeng; Prosa, Ty J; Larson, David J

    2016-06-01

    There are advantages to performing transmission electron backscattering diffraction (tEBSD) in conjunction with focused ion beam-based specimen preparation for atom probe tomography (APT). Although tEBSD allows users to identify the position and character of grain boundaries, which can then be combined with APT to provide full chemical and orientation characterization of grain boundaries, tEBSD can also provide imaging information that improves the APT specimen preparation process by insuring proper placement of the targeted grain boundary within an APT specimen. In this report we discuss sample tilt angles, ion beam milling energies, and other considerations to optimize Kikuchi diffraction pattern quality for the APT specimen geometry. Coordinated specimen preparation and analysis of a grain boundary in a Ni-based Inconel 600 alloy is used to illustrate the approach revealing a 50° misorientation and trace element segregation to the grain boundary.

  18. Backscatter absorption gas imaging systems and light sources therefore

    DOEpatents

    Kulp, Thomas Jan; Kliner, Dahv A. V.; Sommers, Ricky; Goers, Uta-Barbara; Armstrong, Karla M.

    2006-12-19

    The location of gases that are not visible to the unaided human eye can be determined using tuned light sources that spectroscopically probe the gases and cameras that can provide images corresponding to the absorption of the gases. The present invention is a light source for a backscatter absorption gas imaging (BAGI) system, and a light source incorporating the light source, that can be used to remotely detect and produce images of "invisible" gases. The inventive light source has a light producing element, an optical amplifier, and an optical parametric oscillator to generate wavelength tunable light in the IR. By using a multi-mode light source and an amplifier that operates using 915 nm pump sources, the power consumption of the light source is reduced to a level that can be operated by batteries for long periods of time. In addition, the light source is tunable over the absorption bands of many hydrocarbons, making it useful for detecting hazardous gases.

  19. Exploratory study on microanalysis of thin films by backscattering techniques

    NASA Technical Reports Server (NTRS)

    Mayer, J. W.; Nicolet, M. A.

    1975-01-01

    Solid phase epitaxial growth of Si layers was studied by backscattering spectrometry for controllable electrical characteristics. Samples were fabricated by vacuum deposition on a thin layer of Sb before deposition of the amorphous Si layer. Analysis of the resulting SPEG layer showed that Sb was present in the SPEG layer of Si. The characteristic of the SPEG layer against the Si substrate was rectifying. A scanning microprobe picture of a cleaved sample established the presence of a depletion region more than 1 micron below the surface. Hall effect data indicated that the SPEG layer was n-type, with average free carrier concentration of about 10 to the 19th power cm/3 and average electron mobility of about 40 sq cm/Vs. SPEG with Pd silicide or Ni silicide transport layers showed fast initial transient growth regimes with slower growth in the steady state regimes.

  20. Control of light backscattering in blood during intravenous laser irradiation

    NASA Astrophysics Data System (ADS)

    Melnik, Ivan S.; Popov, V. D.; Rusina, Tatyana V.; Dets, Sergiy M.

    1997-02-01

    One of the most important problems in modern laser medicine is the determination of system response on laser treatment. Reaction of living system is significant during many kinds of laser procedures like surgery, therapy and biostimulation. Our study was aimed to optimize laser exposure using feed-back fiber system for intravenous laser irradiation of blood (ILIB). This system consisted of helium-neon laser (633 nm, 5 mW) with coupled fiber unit, photodetector and PC interface. Photodetector signals produced due to light backscattering were storaged and processed during all blood irradiation procedure. Significant time-dependent variations were observed within 9-15 min after beginning of treatment procedure and were correlated with number of trials, stage and character of disease. The designed feed-back system allows us to register a human blood response on laser irradiation to achieve better cure effect.

  1. Quantitation of Membrane-Ligand Interactions Using Backscattering Interferometry

    PubMed Central

    Baksh, Michael M.; Kussrow, Amanda K.; Mileni, Mauro; Finn, M.G.; Bornhop, Darryl J.

    2011-01-01

    Though membrane-associated proteins are ubiquitous within all living organisms and represent the majority of drug targets, a general method for direct, label-free measurement of ligand binding to native membranes has not been reported. Here we show backscattering interferometry (BSI) to be a viable technique for quantifying ligand-receptor binding affinities in a variety of membrane environments. By detecting minute changes in the refractive index of a solution, BSI allows binding interactions of proteins with their ligands to be measured at picomolar concentrations. Equilibrium binding constants in the micromolar to picomolar range were obtained for small- and large-molecule interactions in both synthetic- and cell-derived membranes without the use of labels or supporting substrates. The simple and low-cost hardware, high sensitivity, and label-free nature of BSI should make it readily applicable to the study of many membrane-associated proteins of biochemical and pharmacological interest. PMID:21399645

  2. Pulsed laser linescanner for a backscatter absorption gas imaging system

    DOEpatents

    Kulp, Thomas J.; Reichardt, Thomas A.; Schmitt, Randal L.; Bambha, Ray P.

    2004-02-10

    An active (laser-illuminated) imaging system is described that is suitable for use in backscatter absorption gas imaging (BAGI). A BAGI imager operates by imaging a scene as it is illuminated with radiation that is absorbed by the gas to be detected. Gases become "visible" in the image when they attenuate the illumination creating a shadow in the image. This disclosure describes a BAGI imager that operates in a linescanned manner using a high repetition rate pulsed laser as its illumination source. The format of this system allows differential imaging, in which the scene is illuminated with light at least 2 wavelengths--one or more absorbed by the gas and one or more not absorbed. The system is designed to accomplish imaging in a manner that is insensitive to motion of the camera, so that it can be held in the hand of an operator or operated from a moving vehicle.

  3. Microwave backscattering and emission model for grass canopies

    NASA Technical Reports Server (NTRS)

    Saatchi, Sasan S.; Lang, Roger H.; Levine, David M.

    1991-01-01

    A two-layer model is developed that treats the grass canopy as a collection of randomly oriented elliptical dielectric discs over a layer of thatch with underlying soil surface. The distorted Born approximation in conjunction with the Peake formulation is used to calculate the backscattering coefficient and the emissivity from the canopy. Two particular features of this model which are unique for grass canopies are the variation of the canopy structure and the presence of the thatch layer. The basic parameters in the model such as the size and orientation of grass blades, dielectric constant of soil and vegetation, and thickness and water content of the thatch layer have been obtained from ground truth data. To interpret the available experimental observations of grasslands, numerical results from both passive and active models at L-band (1.4 GHz) are generated and various scattering and emission properties of the grass canopies are discussed.

  4. Ocean Raman Scattering in Satellite Backscatter UV Measurements

    NASA Technical Reports Server (NTRS)

    Vasilkov, Alexander P.; Joiner, Joanna; Gleason, James; Bhartia, Pawan; Bhartia, P. K. (Technical Monitor)

    2002-01-01

    Ocean Raman scattering significantly contributes to the filling-in of solar Fraunhofer lines measured by satellite backscatter ultraviolet (buy) instruments in the cloudless atmosphere over clear ocean waters. A model accounting for this effect in buy measurements is developed and compared with observations from the Global Ozone Monitoring Experiment (GONE). The model extends existing models for ocean Raman scattering to the UV spectral range. Ocean Raman scattering radiance is propagated through the atmosphere using a concept of the Lambert equivalent reflectively and an accurate radiative transfer model for Rayleigh scattering. The model and observations can be used to evaluate laboratory measurements of pure water absorption in the UV. The good agreement between model and observations suggests that buy instruments may be useful for estimating chlorophyll content.

  5. Unusual Radar Backscatter along the Northern Rim of Imbrium Basin

    NASA Technical Reports Server (NTRS)

    Thompson, Thomas W.; Campbell, Bruce A.; Ghent, Rebecca R.; Hawke, B. Ray; Leverington, David W.

    2006-01-01

    A viewgraph presentation of the unusual radar backscatter properties along the Northern Rim of Imbrium Basin is shown. The contents include: 1) Visual and Infrared Observations of Moon; 2) Radar Observations of Moon; 3) Lunar Orbiter Photographs Geologic Setting; 4) 70-cm Radar Data; 5) .70-cm Radar Dark Halo Craters; 6) 3.8-cm Radar Data; 7) 7.5-m Radar Data; 8) 70cm, 3.8 cm and 7.5-m Radar Data; 9) Optical and Infrared Data; 10) Plato Rilles; 11) Isopachs of Crater Ejecta; 12) Plato-like Craters; 13) Observation Summary; 14) Interpretation Matrix; 15) Dark Halo Diameters vs. Crater Size; and 16) Radar Geologic Column.

  6. Recent developments in two fundamental aspects of electron backscatter diffraction

    NASA Astrophysics Data System (ADS)

    Mingard, K. P.; Day, A. P.; Quested, P. N.

    2014-03-01

    Two very different aspects of electron backscatter diffraction (EBSD) are considered in this paper. Firstly, the use of the technique for the measurement of grain size is discussed with particular reference to the development of international standards to help ensure reproducible and repeatable measurements. In particular the lessons learnt for both calibration of the complete SEM-EBSD system and in choice of the correct data acquisition and processing parameters from an international round robin are summarized. Secondly, extending the capability of EBSD through development of new detectors is discussed. New shadow casting methods provide a means to achieve better accuracy in definition of sample-pattern geometry, while increased detail can be obtained by larger cameras and ultimately direct electron detection.

  7. Application of Electron Backscatter Diffraction to Phase Identification

    SciTech Connect

    El-Dasher, B S; Deal, A

    2008-07-16

    The identification of crystalline phases in solids requires knowledge of two microstructural properties: crystallographic structure and chemical composition. Traditionally, this has been accomplished using X-ray diffraction techniques where the measured crystallographic information, in combination with separate chemical composition measurements for specimens of unknown pedigrees, is used to deduce the unknown phases. With the latest microstructural analysis tools for scanning electron microscopes, both the crystallography and composition can be determined in a single analysis utilizing electron backscatter diffraction and energy dispersive spectroscopy, respectively. In this chapter, we discuss the approach required to perform these experiments, elucidate the benefits and limitations of this technique, and detail via case studies how composition, crystallography, and diffraction contrast can be used as phase discriminators.

  8. Snow backscatter in the 1-8 GHz region

    NASA Technical Reports Server (NTRS)

    Ulaby, F. T.

    1976-01-01

    The 1-8 GHz microwave active spectrometer system was used to measure the backscatter response of snow covered ground. The scattering coefficient was measured for all linear polarization combinations at angles of incidence between nadir and 70 deg. Ground truth data consisted of soil moisture, soil temperature profile, snow depth, snow temperature profile, and snow water equivalent. The radar sensitivity to snow water equivalent increased in magnitude with increasing frequency and was almost angle independent for angles of incidence higher than 30 deg, particularly at the higher frequencies. In the 50 deg to 70 deg angular range and in the 6 to 8 GHz frequency range, the sensitivity was typically between -0.4 dB/.1 g/sq cm and -0.5 dB/,1 g/sq cm, and the associated linear correlation coefficient had a magnitude of about 0.8.

  9. A C-band backscatter model for lake ice in Alaska

    NASA Technical Reports Server (NTRS)

    Wakabayashi, H.; Weeks, W. F.; Jeffries, M. O.

    1993-01-01

    ERS-1 SAR imagery of lake ice growing on shallow tundra lakes in northern Alaska shows interesting radar backscatter variations. Based on the analysis of ice cores from these lakes, a multi-layer backscatter model comprised of the following elements has been developed: (1) specular air-ice; ice-water and ice-frozen soil boundaries; (2) an ice layer of variable thickness; (3) ice sub-layers with air inclusions of variable density, size and shape including spheres, prolate spheroids, and cylinders of finite length. Preliminary model results confirm that backscatter is a sensitive function of greater reflectivity than from an ice-frozen soil interface. The model has also been tested using bubble data derived from ice cores in April 1992. The modelled backscatter is compared with backscatter derived from ERS-1 SAR images obtained at the same time as the fieldwork.

  10. Relating multifrequency radar backscattering to forest biomass: Modeling and AIRSAR measurement

    NASA Technical Reports Server (NTRS)

    Sun, Guo-Qing; Ranson, K. Jon

    1992-01-01

    During the last several years, significant efforts in microwave remote sensing were devoted to relating forest parameters to radar backscattering coefficients. These and other studies showed that in most cases, the longer wavelength (i.e. P band) and cross-polarization (HV) backscattering had higher sensitivity and better correlation to forest biomass. This research examines this relationship in a northern forest area through both backscatter modeling and synthetic aperture radar (SAR) data analysis. The field measurements were used to estimate stand biomass from forest weight tables. The backscatter model described by Sun et al. was modified to simulate the backscattering coefficients with respect to stand biomass. The average number of trees per square meter or radar resolution cell, and the average tree height or diameter breast height (dbh) in the forest stand are the driving parameters of the model. The rest of the soil surface, orientation, and size distributions of leaves and branches, remain unchanged in the simulations.

  11. Plasmon-resonant gold nanorods as low backscattering albedo contrast agents for optical coherence tomography.

    PubMed

    Oldenburg, Amy L; Hansen, Matthew N; Zweifel, Daniel A; Wei, Alexander; Boppart, Stephen A

    2006-07-24

    Plasmon-resonant gold nanorods are demonstrated as low backscattering albedo contrast agents for optical coherence tomography (OCT). We define the backscattering albedo, a', as the ratio of the backscattering to extinction coefficient. Contrast agents which modify a' within the host tissue phantoms are detected with greater sensitivity by the differential OCT measurement of both a' and extinction. Optimum sensitivity is achieved by maximizing the difference between contrast agents and tissue, |a'(ca) - a'(tiss)|. Low backscattering albedo gold nanorods (14x 44 nm; lambda(max) = 780 nm) within a high backscattering albedo tissue phantom with an uncertainty in concentration of 20% (randomized 2+/-0.4% intralipid) were readily detected at 82 ppm (by weight) in a regime where extinction alone could not discriminate nanorods. The estimated threshold of detection was 30 ppm.

  12. Acoustically Induced Vibration of Structures: Reverberant Vs. Direct Acoustic Testing

    NASA Technical Reports Server (NTRS)

    Kolaini, Ali R.; O'Connell, Michael R.; Tsoi, Wan B.

    2009-01-01

    Large reverberant chambers have been used for several decades in the aerospace industry to test larger structures such as solar arrays and reflectors to qualify and to detect faults in the design and fabrication of spacecraft and satellites. In the past decade some companies have begun using direct near field acoustic testing, employing speakers, for qualifying larger structures. A limited test data set obtained from recent acoustic tests of the same hardware exposed to both direct and reverberant acoustic field testing has indicated some differences in the resulting structural responses. In reverberant acoustic testing, higher vibration responses were observed at lower frequencies when compared with the direct acoustic testing. In the case of direct near field acoustic testing higher vibration responses appeared to occur at higher frequencies as well. In reverberant chamber testing and direct acoustic testing, standing acoustic modes of the reverberant chamber or the speakers and spacecraft parallel surfaces can strongly couple with the fundamental structural modes of the test hardware. In this paper data from recent acoustic testing of flight hardware, that yielded evidence of acoustic standing wave coupling with structural responses, are discussed in some detail. Convincing evidence of the acoustic standing wave/structural coupling phenomenon will be discussed, citing observations from acoustic testing of a simple aluminum plate. The implications of such acoustic coupling to testing of sensitive flight hardware will be discussed. The results discussed in this paper reveal issues with over or under testing of flight hardware that could pose unanticipated structural and flight qualification issues. Therefore, it is of paramount importance to understand the structural modal coupling with standing acoustic waves that has been observed in both methods of acoustic testing. This study will assist the community to choose an appropriate testing method and test setup in

  13. Feasibility of using backscattered muons for archeological imaging

    NASA Astrophysics Data System (ADS)

    Bonal, N.; Preston, L. A.

    2013-12-01

    Use of nondestructive methods to accurately locate and characterize underground objects such as rooms and tools found at archeological sites is ideal to preserve these historic sites. High-energy cosmic ray muons are very sensitive to density variation and have been used to image volcanoes and archeological sites such as the Egyptian and Mayan pyramids. Muons are subatomic particles produced in the upper atmosphere that penetrate the earth's crust up to few kilometers. Their absorption rate depends on the density of the materials through which they pass. Measurements of muon flux rate at differing directions provide density variations of the materials between the muon source (cosmic rays and neutrino interactions) and the detector, much like a CAT scan. Currently, muon tomography can resolve features to the sub-meter scale making it useful for this type of work. However, the muon detector must be placed below the target of interest. For imaging volcanoes, the upper portion is imaged when the detector is placed on the earth's surface at the volcano's base. For sites of interest beneath the ground surface, the muon detector would need to be placed below the site in a tunnel or borehole. Placing the detector underground can be costly and may disturb the historical site. We will assess the feasibility of imaging the subsurface using upward traveling muons, to eliminate the current constraint of positioning the detector below the target. This work consists of three parts 1) determine the backscattered flux rate from theory, 2) distinguish backscattered from forward scattered muons at the detector, and 3) validate the theoretical results with field experimentation. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  14. Backscattering and Nonparaxiality Arrest Collapse of Damped Nonlinear Waves

    NASA Technical Reports Server (NTRS)

    Fibich, G.; Ilan, B.; Tsynkov, S.

    2002-01-01

    The critical nonlinear Schrodinger equation (NLS) models the propagation of intense laser light in Kerr media. This equation is derived from the more comprehensive nonlinear Helmholtz equation (NLH) by employing the paraxial approximation and neglecting the backscattered waves. It is known that if the input power of the laser beam (i.e., L(sub 2) norm of the initial solution) is sufficiently high, then the NLS model predicts that the beam will self-focus to a point (i.e.. collapse) at a finite propagation distance. Mathematically, this behavior corresponds to the formation of a singularity in the solution of the NLS. A key question which has been open for many years is whether the solution to the NLH, i.e., the 'parent' equation, may nonetheless exist and remain regular everywhere, in particular for those initial conditions (input powers) that lead to blowup in the NLS. In the current study, we address this question by introducing linear damping into both models and subsequently comparing the numerical solutions of the damped NLH (boundary-value problem) with the corresponding solutions of the damped NLS (initial-value problem). Linear damping is introduced in much the same way as done when analyzing the classical constant-coefficient Helmholtz equation using the limiting absorption principle. Numerically, we have found that it provides a very efficient tool for controlling the solutions of both the NLH and NHS. In particular, we have been able to identify initial conditions for which the NLS solution does become singular. whereas the NLH solution still remains regular everywhere. We believe that our finding of a larger domain of existence for the NLH than that for the NLS is accounted for by precisely those mechanisms, that have been neglected when deriving the NLS from the NLH, i.e., nonparaxiality and backscattering.

  15. Modeling low-coherence enhanced backscattering using Monte Carlo simulation.

    PubMed

    Subramanian, Hariharan; Pradhan, Prabhakar; Kim, Young L; Liu, Yang; Li, Xu; Backman, Vadim

    2006-08-20

    Constructive interference between coherent waves traveling time-reversed paths in a random medium gives rise to the enhancement of light scattering observed in directions close to backscattering. This phenomenon is known as enhanced backscattering (EBS). According to diffusion theory, the angular width of an EBS cone is proportional to the ratio of the wavelength of light lambda to the transport mean-free-path length l(s)* of a random medium. In biological media a large l(s)* approximately 0.5-2 mm > lambda results in an extremely small (approximately 0.001 degrees ) angular width of the EBS cone, making the experimental observation of such narrow peaks difficult. Recently, the feasibility of observing EBS under low spatial coherence illumination (spatial coherence length Lsc < l(s)*) was demonstrated. Low spatial coherence behaves as a spatial filter rejecting longer path lengths and thus resulting in an increase of more than 100 times in the angular width of low coherence EBS (LEBS) cones. However, a conventional diffusion approximation-based model of EBS has not been able to explain such a dramatic increase in LEBS width. We present a photon random walk model of LEBS by using Monte Carlo simulation to elucidate the mechanism accounting for the unprecedented broadening of the LEBS peaks. Typically, the exit angles of the scattered photons are not considered in modeling EBS in the diffusion regime. We show that small exit angles are highly sensitive to low-order scattering, which is crucial for accurate modeling of LEBS. Our results show that the predictions of the model are in excellent agreement with the experimental data.

  16. Acoustic bubble removal method

    NASA Technical Reports Server (NTRS)

    Trinh, E. H.; Elleman, D. D.; Wang, T. G. (Inventor)

    1983-01-01

    A method is described for removing bubbles from a liquid bath such as a bath of molten glass to be used for optical elements. Larger bubbles are first removed by applying acoustic energy resonant to a bath dimension to drive the larger bubbles toward a pressure well where the bubbles can coalesce and then be more easily removed. Thereafter, submillimeter bubbles are removed by applying acoustic energy of frequencies resonant to the small bubbles to oscillate them and thereby stir liquid immediately about the bubbles to facilitate their breakup and absorption into the liquid.

  17. Broadband Acoustic Hyperbolic Metamaterial.

    PubMed

    Shen, Chen; Xie, Yangbo; Sui, Ni; Wang, Wenqi; Cummer, Steven A; Jing, Yun

    2015-12-18

    In this Letter, we report on the design and experimental characterization of a broadband acoustic hyperbolic metamaterial. The proposed metamaterial consists of multiple arrays of clamped thin plates facing the y direction and is shown to yield opposite signs of effective density in the x and y directions below a certain cutoff frequency, therefore, yielding a hyperbolic dispersion. Partial focusing and subwavelength imaging are experimentally demonstrated at frequencies between 1.0 and 2.5 kHz. The proposed metamaterial could open up new possibilities for acoustic wave manipulation and may find usage in medical imaging and nondestructive testing.

  18. Acoustic emission intrusion detector

    DOEpatents

    Carver, Donald W.; Whittaker, Jerry W.

    1980-01-01

    An intrusion detector is provided for detecting a forcible entry into a secured structure while minimizing false alarms. The detector uses a piezoelectric crystal transducer to sense acoustic emissions. The transducer output is amplified by a selectable gain amplifier to control the sensitivity. The rectified output of the amplifier is applied to a Schmitt trigger circuit having a preselected threshold level to provide amplitude discrimination. Timing circuitry is provided which is activated by successive pulses from the Schmitt trigger which lie within a selected time frame for frequency discrimination. Detected signals having proper amplitude and frequency trigger an alarm within the first complete cycle time of a detected acoustical disturbance signal.

  19. Electromechanical acoustic liner

    NASA Technical Reports Server (NTRS)

    Sheplak, Mark (Inventor); Cattafesta, III, Louis N. (Inventor); Nishida, Toshikazu (Inventor); Horowitz, Stephen Brian (Inventor)

    2007-01-01

    A multi-resonator-based system responsive to acoustic waves includes at least two resonators, each including a bottom plate, side walls secured to the bottom plate, and a top plate disposed on top of the side walls. The top plate includes an orifice so that a portion of an incident acoustical wave compresses gas in the resonators. The bottom plate or the side walls include at least one compliant portion. A reciprocal electromechanical transducer coupled to the compliant portion of each of the resonators forms a first and second transducer/compliant composite. An electrical network is disposed between the reciprocal electromechanical transducer of the first and second resonator.

  20. Broadband Acoustic Clutter

    DTIC Science & Technology

    2010-09-30

    fluidized mud, which has sound speeds at (or sometimes below) the sound speed of the water column, here 1512 m/s. Interestingly, there is a sound speed...data. 3 specular 25m Figure 1. The map shows the AUV track (red line) overlaid on multibeam bathymetry. Mean water depth is about 165m...Preston, and D.A. Abraham, Long-range acoustic scattering from a shallow- water mud volcano cluster J. Acoust. Soc. Am., 122, 1946-1958, 2007. [3

  1. Acoustic tooth cleaner

    NASA Technical Reports Server (NTRS)

    Heyman, J. S. (Inventor)

    1982-01-01

    An acoustic oral hygiene unit is described that uses acoustic energy to oscillate mild abrasive particles in a water suspension which is then directed in a low pressure stream onto the teeth. The oscillating abrasives scrub the teeth clean removing food particles, plaque, calculous, and other foreign material from tooth surfaces, interproximal areas, and tooth-gingiva interface more effectively than any previous technique. The relatively low power output and the basic design makes the invention safe and convenient for everyday use in the home without special training. This invention replaces all former means of home dental prophylaxis, and requires no augmentation to fulfill all requirements for daily oral hygienic care.

  2. Post Treatment of Acoustic Neuroma

    MedlinePlus

    Home What is an AN What is an Acoustic Neuroma? Identifying an AN Symptoms Acoustic Neuroma Keywords Educational Video Pre-Treatment Treatment Options Summary Treatment Options Watch and Wait Radiation Microsurgery Acoustic Neuroma Decision Tree Questions for Your Physician Questions ...

  3. The B AB AR detector

    NASA Astrophysics Data System (ADS)

    Aubert, B.; Bazan, A.; Boucham, A.; Boutigny, D.; De Bonis, I.; Favier, J.; Gaillard, J.-M.; Jeremie, A.; Karyotakis, Y.; Le Flour, T.; Lees, J. P.; Lieunard, S.; Petitpas, P.; Robbe, P.; Tisserand, V.; Zachariadou, K.; Palano, A.; Chen, G. P.; Chen, J. C.; Qi, N. D.; Rong, G.; Wang, P.; Zhu, Y. S.; Eigen, G.; Reinertsen, P. L.; Stugu, B.; Abbott, B.; Abrams, G. S.; Amerman, L.; Borgland, A. W.; Breon, A. B.; Brown, D. N.; Button-Shafer, J.; Clark, A. R.; Dardin, S.; Day, C.; Dow, S. F.; Fan, Q.; Gaponenko, I.; Gill, M. S.; Goozen, F. R.; Gowdy, S. J.; Gritsan, A.; Groysman, Y.; Hernikl, C.; Jacobsen, R. G.; Jared, R. C.; Kadel, R. W.; Kadyk, J.; Karcher, A.; Kerth, L. T.; Kipnis, I.; Kluth, S.; Kral, J. F.; Lafever, R.; LeClerc, C.; Levi, M. E.; Lewis, S. A.; Lionberger, C.; Liu, T.; Long, M.; Luo, L.; Lynch, G.; Luft, P.; Mandelli, E.; Marino, M.; Marks, K.; Matuk, C.; Meyer, A. B.; Minor, R.; Mokhtarani, A.; Momayezi, M.; Nyman, M.; Oddone, P. J.; Ohnemus, J.; Oshatz, D.; Patton, S.; Pedrali-Noy, M.; Perazzo, A.; Peters, C.; Pope, W.; Pripstein, M.; Quarrie, D. R.; Rasson, J. E.; Roe, N. A.; Romosan, A.; Ronan, M. T.; Shelkov, V. G.; Stone, R.; Strother, P. D.; Telnov, A. V.; von der Lippe, H.; Weber, T. F.; Wenzel, W. A.; Zizka, G.; Bright-Thomas, P. G.; Hawkes, C. M.; Kirk, A.; Knowles, D. J.; O'Neale, S. W.; Watson, A. T.; Watson, N. K.; Deppermann, T.; Koch, H.; Krug, J.; Kunze, M.; Lewandowski, B.; Peters, K.; Schmuecker, H.; Steinke, M.; Andress, J. C.; Barlow, N. R.; Bhimji, W.; Chevalier, N.; Clark, P. J.; Cottingham, W. N.; De Groot, N.; Dyce, N.; Foster, B.; Mass, A.; McFall, J. D.; Wallom, D.; Wilson, F. F.; Abe, K.; Hearty, C.; McKenna, J. A.; Thiessen, D.; Camanzi, B.; Harrison, T. J.; McKemey, A. K.; Tinslay, J.; Antohin, E. I.; Blinov, V. E.; Bukin, A. D.; Bukin, D. A.; Buzykaev, A. R.; Dubrovin, M. S.; Golubev, V. B.; Ivanchenko, V. N.; Kolachev, G. M.; Korol, A. A.; Kravchenko, E. A.; Mikhailov, S. F.; Onuchin, A. P.; Salnikov, A. A.; Serednyakov, S. I.; Skovpen, Yu. I.; Telnov, V. I.; Yushkov, A. N.; Booth, J.; Lankford, A. J.; Mandelkern, M.; Pier, S.; Stoker, D. P.; Zioulas, G.; Ahsan, A.; Arisaka, K.; Buchanan, C.; Chun, S.; Faccini, R.; MacFarlane, D. B.; Prell, S. A.; Rahatlou, Sh.; Raven, G.; Sharma, V.; Burke, S.; Callahan, D.; Campagnari, C.; Dahmes, B.; Hale, D.; Hart, P. A.; Kuznetsova, N.; Kyre, S.; Levy, S. L.; Long, O.; Lu, A.; May, J.; Richman, J. D.; Verkerke, W.; Witherell, M.; Yellin, S.; Beringer, J.; DeWitt, J.; Dorfan, D. E.; Eisner, A. M.; Frey, A.; Grillo, A. A.; Grothe, M.; Heusch, C. A.; Johnson, R. P.; Kroeger, W.; Lockman, W. S.; Pulliam, T.; Rowe, W.; Sadrozinski, H.; Schalk, T.; Schmitz, R. E.; Schumm, B. A.; Seiden, A.; Spencer, E. N.; Turri, M.; Walkowiak, W.; Wilder, M.; Williams, D. C.; Chen, E.; Dubois-Felsmann, G. P.; Dvoretskii, A.; Hanson, J. E.; Hitlin, D. G.; Kolomensky, Yu. G.; Metzler, S.; Oyang, J.; Porter, F. C.; Ryd, A.; Samuel, A.; Weaver, M.; Yang, S.; Zhu, R. Y.; Devmal, S.; Geld, T. L.; Jayatilleke, S.; Jayatilleke, S. M.; Mancinelli, G.; Meadows, B. T.; Sokoloff, M. D.; Bloom, P.; Broomer, B.; Erdos, E.; Fahey, S.; Ford, W. T.; Gaede, F.; van Hoek, W. C.; Johnson, D. R.; Michael, A. K.; Nauenberg, U.; Olivas, A.; Park, H.; Rankin, P.; Roy, J.; Sen, S.; Smith, J. G.; Wagner, D. L.; Blouw, J.; Harton, J. L.; Krishnamurthy, M.; Soffer, A.; Toki, W. H.; Warner, D. W.; Wilson, R. J.; Zhang, J.; Brandt, T.; Brose, J.; Dahlinger, G.; Dickopp, M.; Dubitzky, R. S.; Eckstein, P.; Futterschneider, H.; Kocian, M. L.; Krause, R.; Müller-Pfefferkorn, R.; Schubert, K. R.; Schwierz, R.; Spaan, B.; Wilden, L.; Behr, L.; Bernard, D.; Bonneaud, G. R.; Brochard, F.; Cohen-Tanugi, J.; Ferrag, S.; Fouque, G.; Gastaldi, F.; Matricon, P.; Mora de Freitas, P.; Renard, C.; Roussot, E.; T'Jampens, S.; Thiebaux, C.; Vasileiadis, G.; Verderi, M.; Anjomshoaa, A.; Bernet, R.; Di Lodovico, F.; Muheim, F.; Playfer, S.; Swain, J. E.; Falbo, M.; Bozzi, C.; Dittongo, S.; Folegani, M.; Piemontese, L.; Ramusino, A. C.; Treadwell, E.; Anulli, F.; Baldini-Ferroli, R.; Calcaterra, A.; de Sangro, R.; Falciai, D.; Finocchiaro, G.; Patteri, P.; Peruzzi, I. M.; Piccolo, M.; Xie, Y.; Zallo, A.; Bagnasco, S.; Buzzo, A.; Contri, R.; Crosetti, G.; Fabbricatore, P.; Farinon, S.; Lo Vetere, M.; Macri, M.; Minutoli, S.; Monge, M. R.; Musenich, R.; Pallavicini, M.; Parodi, R.; Passaggio, S.; Pastore, F. C.; Patrignani, C.; Pia, M. G.; Priano, C.; Robutti, E.; Santroni, A.; Bartoldus, R.; Dignan, T.; Hamilton, R.; Mallik, U.; Cochran, J.; Crawley, H. B.; Fischer, P. A.; Lamsa, J.; McKay, R.; Meyer, W. T.; Rosenberg, E. I.; Albert, J. N.; Beigbeder, C.; Benkebil, M.; Breton, D.; Cizeron, R.; Du, S.; Grosdidier, G.; Hast, C.; Höcker, A.; Lacker, H. M.; LePeltier, V.; Lutz, A. M.; Plaszczynski, S.; Schune, M. H.; Trincaz-Duvoid, S.; Truong, K.; Valassi, A.; Wormser, G.; Alford, O.; Behne, D.; Bionta, R. M.; Bowman, J.; Brigljević, V.; Brooks, A.; Dacosta, V. A.; Fackler, O.; Fujino, D.; Harper, M.; Lange, D. J.; Mugge, M.; O'Connor, T. G.; Olson, H.; Ott, L.; Parker, E.; Pedrotti, B.; Roeben, M.; Shi, X.; van Bibber, K.; Wenaus, T. J.; Wright, D. M.; Wuest, C. R.; Yamamoto, B.; Carroll, M.; Cooke, P.; Fry, J. R.; Gabathuler, E.; Gamet, R.; George, M.; Kay, M.; McMahon, S.; Muir, A.; Payne, D. J.; Sloane, R. J.; Sutcliffe, P.; Touramanis, C.; Aspinwall, M. L.; Bowerman, D. A.; Dauncey, P. D.; Eschrich, I.; Gunawardane, N. J. W.; Martin, R.; Nash, J. A.; Price, D. R.; Sanders, P.; Smith, D.; Azzopardi, D. E.; Back, J. J.; Dixon, P.; Harrison, P. F.; Newman-Coburn, D.; Potter, R. J. L.; Shorthouse, H. W.; Williams, M. I.; Vidal, P. B.; Cowan, G.; George, S.; Green, M. G.; Kurup, A.; Marker, C. E.; McGrath, P.; McMahon, T. R.; Salvatore, F.; Scott, I.; Vaitsas, G.; Brown, D.; Davis, C. L.; Li, Y.; Pavlovich, J.; Allison, J.; Barlow, R. J.; Boyd, J. T.; Fullwood, J.; Jackson, F.; Khan, A.; Lafferty, G. D.; Savvas, N.; Simopoulos, E. T.; Thompson, R. J.; Weatherall, J. H.; Bard, R.; Dallapiccola, C.; Farbin, A.; Jawahery, A.; Lillard, V.; Olsen, J.; Roberts, D. A.; Schieck, J. R.; Blaylock, G.; Flood, K. T.; Hertzbach, S. S.; Kofler, R.; Lin, C. S.; Willocq, S.; Wittlin, J.; Brau, B.; Cowan, R.; Taylor, F.; Yamamoto, R. K.; Britton, D. I.; Fernholz, R.; Houde, M.; Milek, M.; Patel, P. M.; Trischuk, J.; Lanni, F.; Palombo, F.; Bauer, J. M.; Booke, M.; Cremaldi, L.; Kroeger, R.; Reep, M.; Reidy, J.; Sanders, D. A.; Summers, D. J.; Arguin, J. F.; Beaulieu, M.; Martin, J. P.; Nief, J. Y.; Seitz, R.; Taras, P.; Woch, A.; Zacek, V.; Nicholson, H.; Sutton, C. S.; Cartaro, C.; Cavallo, N.; De Nardo, G.; Fabozzi, F.; Gatto, C.; Lista, L.; Piccolo, D.; Sciacca, C.; Cason, N. M.; LoSecco, J. M.; Alsmiller, J. R. G.; Gabriel, T. A.; Handler, T.; Heck, J.; Iwasaki, M.; Sinev, N. B.; Caracciolo, R.; Colecchia, F.; Dal Corso, F.; Galeazzi, F.; Marzolla, M.; Michelon, G.; Morandin, M.; Posocco, M.; Rotondo, M.; Santi, S.; Simonetto, F.; Stroili, R.; Torassa, E.; Voci, C.; Bailly, P.; Benayoun, M.; Briand, H.; Chauveau, J.; David, P.; De la Vaissière, C.; Del Buono, L.; Genat, J.-F.; Hamon, O.; Leruste, Ph.; Le Diberder, F.; Lebbolo, H.; Lory, J.; Martin, L.; Martinez-Vidal, F.; Roos, L.; Stark, J.; Versillé, S.; Zhang, B.; Manfredi, P. F.; Ratti, L.; Re, V.; Speziali, V.; Frank, E. D.; Gladney, L.; Guo, Q. H.; Panetta, J. H.; Angelini, C.; Batignani, G.; Bettarini, S.; Bondioli, M.; Bosi, F.; Carpinelli, M.; Forti, F.; Gaddi, A.; Gagliardi, D.; Giorgi, M. A.; Lusiani, A.; Mammini, P.; Morganti, M.; Morsani, F.; Neri, N.; Profeti, A.; Paoloni, E.; Raffaelli, F.; Rama, M.; Rizzo, G.; Sandrelli, F.; Simi, G.; Triggiani, G.; Haire, M.; Judd, D.; Paick, K.; Turnbull, L.; Wagoner, D. E.; Albert, J.; Bula, C.; Kelsey, M. H.; Lu, C.; McDonald, K. T.; Miftakov, V.; Sands, B.; Schaffner, S. F.; Smith, A. J. S.; Tumanov, A.; Varnes, E. W.; Bronzini, F.; Buccheri, A.; Bulfon, C.; Cavoto, G.; del Re, D.; Ferrarotto, F.; Ferroni, F.; Fratini, K.; Lamanna, E.; Leonardi, E.; Mazzoni, M. A.; Morganti, S.; Piredda, G.; Safai Tehrani, F.; Serra, M.; Voena, C.; Waldi, R.; Jacques, P. F.; Kalelkar, M.; Plano, R. J.; Adye, T.; Claxton, B.; Dowdell, J.; Egede, U.; Franek, B.; Galagedera, S.; Geddes, N. I.; Gopal, G. P.; Kay, J.; Lidbury, J.; Madani, S.; Metcalfe, S.; Metcalfe, S.; Markey, G.; Olley, P.; Watt, M.; Xella, S. M.; Aleksan, R.; Besson, P.; Bourgeois, P.; Convert, P.; De Domenico, G.; de Lesquen, A.; Emery, S.; Gaidot, A.; Ganzhur, S. F.; Georgette, Z.; Gosset, L.; Graffin, P.; Hamel de Monchenault, G.; Hervé, S.; Karolak, M.; Kozanecki, W.; Langer, M.; London, G. W.; Marques, V.; Mayer, B.; Micout, P.; Mols, J. P.; Mouly, J. P.; Penichot, Y.; Rolquin, J.; Serfass, B.; Toussaint, J. C.; Usseglio, M.; Vasseur, G.; Yeche, C.; Zito, M.; Copty, N.; Purohit, M. V.; Yumiceva, F. X.; Adam, I.; Adesanya, A.; Anthony, P. L.; Aston, D.; Bartelt, J.; Becla, J.; Bell, R.; Bloom, E.; Boeheim, C. T.; Boyarski, A. M.; Boyce, R. F.; Briggs, D.; Bulos, F.; Burgess, W.; Byers, B.; Calderini, G.; Chestnut, R.; Claus, R.; Convery, M. R.; Coombes, R.; Cottrell, L.; Coupal, D. P.; Coward, D. H.; Craddock, W. W.; DeBarger, S.; DeStaebler, H.; Dorfan, J.; Doser, M.; Dunwoodie, W.; Dusatko, J. E.; Ecklund, S.; Fieguth, T. H.; Freytag, D. R.; Glanzman, T.; Godfrey, G. L.; Haller, G.; Hanushevsky, A.; Harris, J.; Hasan, A.; Hee, C.; Himel, T.; Huffer, M. E.; Hung, T.; Innes, W. R.; Jessop, C. P.; Kawahara, H.; Keller, L.; King, M. E.; Klaisner, L.; Krebs, H. J.; Langenegger, U.; Langeveld, W.; Leith, D. W. G. S.; Louie, S. K.; Luitz, S.; Luth, V.; Lynch, H. L.; McDonald, J.; Manzin, G.; Marsiske, H.; Mattison, T.; McCulloch, M.; McDougald, M.; McShurley, D.; Menke, S.; Messner, R.; Metcalfe, S.; Morii, M.; Mount, R.; Muller, D. R.; Nelson, D.; Nordby, M.; O'Grady, C. P.; Olavson, L.; Olsen, J.; O'Neill, F. G.; Oxoby, G.; Paolucci, P.; Pavel, T.; Perl, J.; Pertsova, M.; Petrak, S.; Putallaz, G.; Raines, P. E.; Ratcliff, B. N.; Reif, R.; Robertson, S. H.; Rochester, L. S.; Roodman, A.; Russel, J. J.; Sapozhnikov, L.; Saxton, O. H.; Schietinger, T.; Schindler, R. H.; Schwiening, J.; Sciolla, G.; Seeman, J. T.; Serbo, V. V.; Shapiro, S.; Skarpass, K., Sr.; Snyder, A.; Soderstrom, E.; Soha, A.; Spanier, S. M.; Stahl, A.; Stiles, P.; Su, D.; Sullivan, M. K.; Talby, M.; Tanaka, H. A.; Va'vra, J.; Wagner, S. R.; Wang, R.; Weber, T.; Weinstein, A. J. R.; White, J. L.; Wienands, U.; Wisniewski, W. J.; Young, C. C.; Yu, N.; Burchat, P. R.; Cheng, C. H.; Kirkby, D.; Meyer, T. I.; Roat, C.; Henderson, R.; Khan, N.; Berridge, S.; Bugg, W.; Cohn, H.; Hart, E.; Weidemann, A. W.; Benninger, T.; Izen, J. M.; Kitayama, I.; Lou, X. C.; Turcotte, M.; Bianchi, F.; Bona, M.; Daudo, F.; Di Girolamo, B.; Gamba, D.; Grosso, P.; Smol, A.; Trapani, P. P.; Zanin, D.; Bosisio, L.; Della Ricca, G.; Lanceri, L.; Pompili, A.; Poropat, P.; Prest, M.; Rashevskaia, I.; Vallazza, E.; Vuagnin, G.; Panvini, R. S.; Brown, C.; De Silva, A.; Kowalewski, R.; Pitman, D.; Roney, J. M.; Band, H. R.; Charles, E.; Dasu, S.; Elmer, P.; Johnson, J. R.; Nielsen, J.; Orejudos, W.; Pan, Y.; Prepost, R.; Scott, I. J.; Walsh, J.; Wu, S. L.; Yu, Z.; Zobernig, H.; Moore, T. B.; Neal, H.

    2002-02-01

    B AB AR, the detector for the SLAC PEP-II asymmetric e +e - B Factory operating at the ϒ(4 S) resonance, was designed to allow comprehensive studies of CP-violation in B-meson decays. Charged particle tracks are measured in a multi-layer silicon vertex tracker surrounded by a cylindrical wire drift chamber. Electromagnetic showers from electrons and photons are detected in an array of CsI crystals located just inside the solenoidal coil of a superconducting magnet. Muons and neutral hadrons are identified by arrays of resistive plate chambers inserted into gaps in the steel flux return of the magnet. Charged hadrons are identified by d E/d x measurements in the tracking detectors and by a ring-imaging Cherenkov detector surrounding the drift chamber. The trigger, data acquisition and data-monitoring systems, VME- and network-based, are controlled by custom-designed online software. Details of the layout and performance of the detector components and their associated electronics and software are presented.

  4. Ab initio phonon limited transport

    NASA Astrophysics Data System (ADS)

    Verstraete, Matthieu

    We revisit the thermoelectric (TE) transport properties of two champion materials, PbTe and SnSe, using fully first principles methods. In both cases the performance of the material is due to subtle combinations of structural effects, scattering, and phase space reduction. In PbTe anharmonic effects are completely opposite to the predicted quasiharmonic evolution of phonon frequencies and to frequently (and incorrectly) cited extrapolations of experiments. This stabilizes the material at high T, but also tends to enhance its thermal conductivity, in a non linear manner, above 600 Kelvin. This explains why PbTe is in practice limited to room temperature applications. SnSe has recently been shown to be the most efficient TE material in bulk form. This is mainly due to a strongly enhanced carrier concentration and electrical conductivity, after going through a phase transition from 600 to 800 K. We calculate the transport coefficients as well as the defect concentrations ab initio, showing excellent agreement with experiment, and elucidating the origin of the double phase transition as well as the new charge carriers. AH Romero, EKU Gross, MJ Verstraete, and O Hellman PRB 91, 214310 (2015) O. Hellman, IA Abrikosov, and SI Simak, PRB 84 180301 (2011)

  5. Fundamentals of Acoustics. Psychoacoustics and Hearing. Acoustical Measurements

    NASA Technical Reports Server (NTRS)

    Begault, Durand R.; Ahumada, Al (Technical Monitor)

    1997-01-01

    These are 3 chapters that will appear in a book titled "Building Acoustical Design", edited by Charles Salter. They are designed to introduce the reader to fundamental concepts of acoustics, particularly as they relate to the built environment. "Fundamentals of Acoustics" reviews basic concepts of sound waveform frequency, pressure, and phase. "Psychoacoustics and Hearing" discusses the human interpretation sound pressure as loudness, particularly as a function of frequency. "Acoustic Measurements" gives a simple overview of the time and frequency weightings for sound pressure measurements that are used in acoustical work.

  6. Is dust acoustic wave a new plasma acoustic mode?

    NASA Astrophysics Data System (ADS)

    Dwivedi, C. B.

    1997-09-01

    In this Brief Communication, the claim of the novelty of the dust acoustic wave in a dusty plasma within the constant dust charge model is questioned. Conceptual lacunas behind the claim have been highlighted and appropriate physical arguments have been forwarded against the claim. It is demonstrated that the so-called dust acoustic wave could better be termed as a general acoustic fluctuation response with a dominant characteristic feature of the acoustic-like mode (ALM) fluctuation response reported by Dwivedi et al. [J. Plasma Phys. 41, 219 (1989)]. It is suggested that both correct and more usable nomenclature of the ALM should be the so-called acoustic mode.

  7. Acoustic subwavelength imaging of subsurface objects with acoustic resonant metalens

    SciTech Connect

    Cheng, Ying; Liu, XiaoJun; Zhou, Chen; Wei, Qi; Wu, DaJian

    2013-11-25

    Early research into acoustic metamaterials has shown the possibility of achieving subwavelength near-field acoustic imaging. However, a major restriction of acoustic metamaterials is that the imaging objects must be placed in close vicinity of the devices. Here, we present an approach for acoustic imaging of subsurface objects far below the diffraction limit. An acoustic metalens made of holey-structured metamaterials is used to magnify evanescent waves, which can rebuild an image at the central plane. Without changing the physical structure of the metalens, our proposed approach can image objects located at certain distances from the input surface, which provides subsurface signatures of the objects with subwavelength spatial resolution.

  8. Rainfall and River Currents Retrieved from Microwave Backscatter

    USGS Publications Warehouse

    Plant, W.J.; Keller, W.C.; Hayes, K.; Nystuen, J.; Spicer, K.

    2003-01-01

    The use of CW microwave sensors in yielding information on both river surface velocities and rain rates was discussed. Eight CW microwave sensors were installed at Cowlitz river in Western Washington State in the US. The sensors measured the river surface velocity via Doppler shifts at eight locations across the river. Comparison of the surface velocities derived from the sensors mounted on the bridge with those measured by current meters and acoustic sensors demonstrated good agreement.

  9. Overview of hydro-acoustic current-measurement applications by the U.S. geological survey in Indiana

    USGS Publications Warehouse

    Morlock, Scott E.; Stewart, James A.

    1999-01-01

    The U.S. Geological Survey (USGS) maintains a network of 170 streamflow-gaging stations in Indiana to collect data from which continuous records of river discharges are produced. Traditionally, the discharge record from a station is produced by recording river stage and making periodic discharge measurements through a range of stage, then developing a relation between stage and discharge. Techniques that promise to increase data collection accuracy and efficiency include the use of hydro-acoustic instrumentation to measure river velocities. The velocity measurements are used to compute river discharge. In-situ applications of hydro-acoustic instruments by the USGS in Indiana include acoustic velocity meters (AVM's) at six streamflow-gaging stations and newly developed Doppler velocity meters (DVM's) at two stations. AVM's use reciprocal travel times of acoustic signals to measure average water velocities along acoustic paths, whereas DVM's use the Doppler shift of backscattered acoustic signals to compute water velocities. In addition to the in-situ applications, three acoustic Doppler current profilers (ADCP's) are used to make river-discharge measurements from moving boats at streamflow-gaging stations in Indiana. The USGS has designed and is testing an innovative unmanned platform from which to make ADCP discharge measurements.

  10. Effects of Mg II and Ca II ionization on ab-initio solar chromosphere models

    NASA Technical Reports Server (NTRS)

    Rammacher, W.; Cuntz, M.

    1991-01-01

    Acoustically heated solar chromosphere models are computed considering radiation damping by (non-LTE) emission from H(-) and by Mg II and Ca II emission lines. The radiative transfer equations for the Mg II k and Ca II K emission lines are solved using the core-saturation method with complete redistribution. The Mg II k and Ca II K cooling rates are compared with the VAL model C. Several substantial improvements over the work of Ulmschneider et al. (1987) are included. It is found that the rapid temperature rises caused by the ionization of Mg II are not formed in the middle chromosphere, but occur at larger atmospheric heights. These models represent the temperature structure of the 'real' solar chromosphere much better. This result is a major precondition for the study of ab-initio models for solar flux tubes based on MHD wave propagation and also for ab-initio models for the solar transition layer.

  11. Erythema ab igne: evolving technology, evolving presentation.

    PubMed

    Kesty, Katarina; Feldman, Steven R

    2014-11-15

    We present a case of a 49-year-old woman with erythema ab igne on her posterior thighs owing to 2-4 hours per day of seat heater use in her car. Erythema ab igne is caused by prolonged exposure to a heat source. It used to be caused mainly by wood stoves used to heat homes. Erythema ab igne is now more often related to other heat sources, including heating pads, laptop computers, and car seat heaters, as in our case. As technology changes, so does the presentation of skin conditions that are related to technology.

  12. Acoustics- Version 1.0

    SciTech Connect

    2012-09-13

    This package contains modules that model acoustic sensors and acoustic sources (hearable) in Umbra. It is typically used to represent hearing in characters within Umbra. Typically, the acoustic sensors detect acoustic sources at a given point; however, it also contains the capability to detect bullet cracks by detecting the sound along the bullet path that is closest to the sensor. A memory module, acoustic memory, represents remembered sounds within a given character. Over time, the sounds are removed, as a character forgets what it has heard.

  13. Acoustic visualizations using surface mapping.

    PubMed

    Siltanen, Samuel; Robinson, Philip W; Saarelma, Jukka; Pätynen, Jukka; Tervo, Sakari; Savioja, Lauri; Lokki, Tapio

    2014-06-01

    Sound visualizations have been an integral part of room acoustics studies for more than a century. As acoustic measurement techniques and knowledge of hearing evolve, acousticians need more intuitive ways to represent increasingly complex data. Microphone array processing now allows accurate measurement of spatio-temporal acoustic properties. However, the multidimensional data can be a challenge to display coherently. This letter details a method of mapping visual representations of acoustic reflections from a receiver position to the surfaces from which the reflections originated. The resulting animations are presented as a spatial acoustic analysis tool.

  14. Intelligent Engine Systems: Acoustics

    NASA Technical Reports Server (NTRS)

    Wojno, John; Martens, Steve; Simpson, Benjamin

    2008-01-01

    An extensive study of new fan exhaust nozzle technologies was performed. Three new uniform chevron nozzles were designed, based on extensive CFD analysis. Two new azimuthally varying variants were defined. All five were tested, along with two existing nozzles, on a representative model-scale, medium BPR exhaust nozzle. Substantial acoustic benefits were obtained from the uniform chevron nozzle designs, the best benefit being provided by an existing design. However, one of the azimuthally varying nozzle designs exhibited even better performance than any of the uniform chevron nozzles. In addition to the fan chevron nozzles, a new technology was demonstrated, using devices that enhance mixing when applied to an exhaust nozzle. The acoustic benefits from these devices applied to medium BPR nozzles were similar, and in some cases superior to, those obtained from conventional uniform chevron nozzles. However, none of the low noise technologies provided equivalent acoustic benefits on a model-scale high BPR exhaust nozzle, similar to current large commercial applications. New technologies must be identified to improve the acoustics of state-of-the-art high BPR jet engines.

  15. Concert hall acoustics

    NASA Astrophysics Data System (ADS)

    Schroeder, Manfred

    2004-05-01

    I will review some work at Bell Laboratories on artificial reverberation and concert hall acoustics including Philharmonic Hall (Lincoln Center for the Performing Arts, New York). I will also touch on sound diffusion by number-theoretic surfaces and the measurement of reverberation time using the music as played in the hall as a ``test'' signal.

  16. Acoustics in Schools.

    ERIC Educational Resources Information Center

    Singer, Miriam J.

    This paper explores the issues associated with poor acoustics within schools. Additionally, it suggests remedies for existing buildings and those under renovation, as well as concerns for new construction. The paper discusses the effects of unwanted noise on students in terms of physiological, motivational, and cognitive influences. Issues are…

  17. Micro acoustic spectrum analyzer

    DOEpatents

    Schubert, W. Kent; Butler, Michael A.; Adkins, Douglas R.; Anderson, Larry F.

    2004-11-23

    A micro acoustic spectrum analyzer for determining the frequency components of a fluctuating sound signal comprises a microphone to pick up the fluctuating sound signal and produce an alternating current electrical signal; at least one microfabricated resonator, each resonator having a different resonant frequency, that vibrate in response to the alternating current electrical signal; and at least one detector to detect the vibration of the microfabricated resonators. The micro acoustic spectrum analyzer can further comprise a mixer to mix a reference signal with the alternating current electrical signal from the microphone to shift the frequency spectrum to a frequency range that is a better matched to the resonant frequencies of the microfabricated resonators. The micro acoustic spectrum analyzer can be designed specifically for portability, size, cost, accuracy, speed, power requirements, and use in a harsh environment. The micro acoustic spectrum analyzer is particularly suited for applications where size, accessibility, and power requirements are limited, such as the monitoring of industrial equipment and processes, detection of security intrusions, or evaluation of military threats.

  18. Detecting Contaminant Particles Acoustically

    NASA Technical Reports Server (NTRS)

    Wyett, L. M.

    1986-01-01

    Apparatus "listens" for particles in interior of complex turbomachinery. Contact microphones are attached at several points on pump housing. Acoustic transducer also attached to housing to excite entire pump with sound. Frequency of sound is slowly raised until pump resonates. Microphones detect noise of loose particles scraping against pump parts. Such as machining chips in turbopumps or other machinery without disassembly.

  19. Indigenous Acoustic Detection.

    DTIC Science & Technology

    1982-01-26

    considerable distances, and they act as good sensors of human presence. Though singing insects are ubiquitous in warm areas, even in the desert ( Nevo and...methodology. DTIC. CD-58-PL. Lloyd, J. E. 1981. Personnel communication. Nevo , E. and S. A. Blondheim. 1972. Acoustic isolation in the speciation of

  20. Temporal variability of zooplankton biomass from ADCP backscatter time series data at the Bermuda Testbed Mooring site

    NASA Astrophysics Data System (ADS)

    Jiang, Songnian; Dickey, Tommy D.; Steinberg, Deborah K.; Madin, Laurence P.

    2007-04-01

    Temporal variability of acoustically estimated zooplankton biomass at the Bermuda Testbed Mooring (BTM) site in the Sargasso Sea (at 31°43'N, 64°10'W) is described for time scales from less than an hour to the seasonal cycle primarily using data obtained between August 1996 and November 2000, and from May 10 to November 13, 2003. Concurrent high frequency BTM observations of meteorological, physical, and bio-optical variables are used to interpret processes contributing to the zooplankton variability. Zooplankton biomass estimates are derived from regressions of backscatter intensity data measured with an upward looking 153-kHz acoustic Doppler current profiler (ADCP) and zooplankton net tow data collected near the BTM site as part of the Bermuda Atlantic Time-series Study (BATS). Our data show clear event-scale variations. Peaks are associated with annual spring blooms involving mixed layer shoaling and in some cases passages of mesoscale eddy features. Biomass peaks are often coincident with maxima seen in BTM chlorophyll fluorescence measurements (inferred phytoplankton biomass). Some storm events do not appear to manifest in significant perturbations of zooplankton distributions; however, Hurricane Fabian (2003) greatly impacted these distributions. Estimates of zooplankton biomass and relative vertical velocity show the vertical structure of daily migration patterns. Seasonal variations in migration patterns are also evident, with diel changes in zooplankton biomass most pronounced in spring and least pronounced in winter. In summary, our high temporal resolution time series of estimated zooplankton biomass in the open ocean provide information on scales inaccessible through conventional monthly ship-based sampling. These data have implications for upper ocean ecology and the vertical transport of carbon and nitrogen through the diel migration of zooplankton.