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Sample records for eddy accumulation technique

  1. Methane fluxes above the Hainich forest by True Eddy Accumulation and Eddy Covariance

    NASA Astrophysics Data System (ADS)

    Siebicke, Lukas; Gentsch, Lydia; Knohl, Alexander

    2016-04-01

    Understanding the role of forests for the global methane cycle requires quantifying vegetation-atmosphere exchange of methane, however observations of turbulent methane fluxes remain scarce. Here we measured turbulent fluxes of methane (CH4) above a beech-dominated old-growth forest in the Hainich National Park, Germany, and validated three different measurement approaches: True Eddy Accumulation (TEA, closed-path laser spectroscopy), and eddy covariance (EC, open-path and closed-path laser spectroscopy, respectively). The Hainich flux tower is a long-term Fluxnet and ICOS site with turbulent fluxes and ecosystem observations spanning more than 15 years. The current study is likely the first application of True Eddy Accumulation (TEA) for the measurement of turbulent exchange of methane and one of the very few studies comparing open-path and closed-path eddy covariance (EC) setups side-by-side. We observed uptake of methane by the forest during the day (a methane sink with a maximum rate of 0.03 μmol m-2 s-1 at noon) and no or small fluxes of methane from the forest to the atmosphere at night (a methane source of typically less than 0.01 μmol m-2 s-1) based on continuous True Eddy Accumulation measurements in September 2015. First results comparing TEA to EC CO2 fluxes suggest that True Eddy Accumulation is a valid option for turbulent flux quantifications using slow response gas analysers (here CRDS laser spectroscopy, other potential techniques include mass spectroscopy). The TEA system was one order of magnitude more energy efficient compared to closed-path eddy covariance. The open-path eddy covariance setup required the least amount of user interaction but is often constrained by low signal-to-noise ratios obtained when measuring methane fluxes over forests. Closed-path eddy covariance showed good signal-to-noise ratios in the lab, however in the field it required significant amounts of user intervention in addition to a high power consumption. We conclude

  2. USE OF RELAXED EDDY ACCUMULATION TO MEASURE BIOSPHERE-ATMOSPHERE EXCHANGE OF ISOPRENE AND OTHER BIOLOGICAL TRACE GASES

    EPA Science Inventory

    The micrometeorological flux measurement technique known as relaxed eddy accumulation (REA) holds promise as a powerful new tool for ecologists. The more popular eddy covariance (eddy correlation) technique requires the use of sensors that can respond at fast rates (10 Hz), and t...

  3. Eddy current technique for predicting burst pressure

    DOEpatents

    Petri, Mark C.; Kupperman, David S.; Morman, James A.; Reifman, Jaques; Wei, Thomas Y. C.

    2003-01-01

    A signal processing technique which correlates eddy current inspection data from a tube having a critical tubing defect with a range of predicted burst pressures for the tube is provided. The method can directly correlate the raw eddy current inspection data representing the critical tubing defect with the range of burst pressures using a regression technique, preferably an artificial neural network. Alternatively, the technique deconvolves the raw eddy current inspection data into a set of undistorted signals, each of which represents a separate defect of the tube. The undistorted defect signal which represents the critical tubing defect is related to a range of burst pressures utilizing a regression technique.

  4. A True Eddy Accumulation - Eddy Covariance hybrid for measurements of turbulent trace gas fluxes

    NASA Astrophysics Data System (ADS)

    Siebicke, Lukas

    2016-04-01

    Eddy covariance (EC) is state-of-the-art in directly and continuously measuring turbulent fluxes of carbon dioxide and water vapor. However, low signal-to-noise ratios, high flow rates and missing or complex gas analyzers limit it's application to few scalars. True eddy accumulation, based on conditional sampling ideas by Desjardins in 1972, requires no fast response analyzers and is therefore potentially applicable to a wider range of scalars. Recently we showed possibly the first successful implementation of True Eddy Accumulation (TEA) measuring net ecosystem exchange of carbon dioxide of a grassland. However, most accumulation systems share the complexity of having to store discrete air samples in physical containers representing entire flux averaging intervals. The current study investigates merging principles of eddy accumulation and eddy covariance, which we here refer to as "true eddy accumulation in transient mode" (TEA-TM). This direct flux method TEA-TM combines true eddy accumulation with continuous sampling. The TEA-TM setup is simpler than discrete accumulation methods while avoiding the need for fast response gas analyzers and high flow rates required for EC. We implemented the proposed TEA-TM method and measured fluxes of carbon dioxide (CO2), methane (CH4) and water vapor (H2O) above a mixed beech forest at the Hainich Fluxnet and ICOS site, Germany, using a G2301 laser spectrometer (Picarro Inc., USA). We further simulated a TEA-TM sampling system using measured high frequency CO2 time series from an open-path gas analyzer. We operated TEA-TM side-by-side with open-, enclosed- and closed-path EC flux systems for CO2, H2O and CH4 (LI-7500, LI-7200, LI-6262, LI-7700, Licor, USA, and FGGA LGR, USA). First results show that TEA-TM CO2 fluxes were similar to EC fluxes. Remaining differences were similar to those between the three eddy covariance setups (open-, enclosed- and closed-path gas analyzers). Measured TEA-TM CO2 fluxes from our physical

  5. A Comparison of GHG Flux Measurements by Relaxed Eddy Accumulation and Eddy Covariance Methods Using FTIR and QCL Analyzers

    NASA Astrophysics Data System (ADS)

    Vermeulen, A. T.; Laborde, M.; Hensen, A.; van den Bulk, P.; Famulari, D.; Griffith, D. W.; Nemitz, E.

    2013-12-01

    In this presentation results obtained with a novel system for Relaxed Eddy Accumulation (REA) measurements using an Ecotech Spectronus FTIR analyzer (Griffth et al, 2012) will be compared to eddy covariance fluxes using an Aerodyne QCL and a Licor 6262 NDIR analyzer. The REA FTIR system can be easily combined with other standard (e.g. NDIR) analyzers suited for eddy covariance measurements to allow for scaling of the obtained up/down concentration differences with the directly measured fluxes. Furthermore the FTIR system allows for on-line simultaneous high precision concentration measurement of a large number of different gases and even isotope composition, next to the measurement of CO2, CH4 and N2O mixing ratios. The final design goal for the REA FTIR system is an attractive fully automated, low maintenance system for long-term monitoring of Greenhouse Gas fluxes at the hourly time scale and a spatial scale of about 1 km2. During a campaign of four weeks in June 2013 (in the framework of the InGOS EU project) at a grazed grassland site at Easter Bush, Scotland (UK), simultaneous surface flux measurements of N2O and additionally CO2 and CH4 have been performed using our systems and a number of setups from other groups.. Weather conditions during the campaign were excellent and after the application of fertilizer at the field and some rainfall the increased emission of N2O was detected clearly by all systems. Both the eddy covariance and REA methods performed well during the campaign and the measured fluxes compare satisfactorily. In general the resulting fluxes from the FTIR system are lower then the QCL based results. Reasons for these deviations will be discussed together with implications of the results for the design of future REA measurements using the FTIR system. Griffith, D.W.T., N.M. Deutscher, C.G.R. Caldow, G. Kettlewell, M. Riggenbach and S. Hammer, A Fourier transform infrared trace gas analyser for atmospheric applications. Atmospheric Measurement

  6. On eddy accumulation with limited conditional sampling to measure air-surface exchange

    SciTech Connect

    Wesely, M.L.; Hart, R.L.

    1994-01-01

    An analysis of turbulence data collected at a height of 12.3 m above grasslands was carried out to illustrate some of the limitations and possible improvements in methods to compute vertical fluxes of trace substances by the eddy accumulation technique with conditional sampling. The empirical coefficient used in the technique has a slight dependence on atmospheric stability, which can be minimized by using a threshold vertical velocity equal to approximately 0.75{sigma}{sub w}, below which chemical sampling is suspended. This protocol results in a smaller chemical sample but increases the differences in concentrations by approximately 70%. For effective conditional sampling when mass is being accumulated in a trap or reservoir, the time of sampling during updrafts versus downdrafts should be measured and used to adjust estimates of the mean concentrations.

  7. Disjunct eddy accumulation flux measurements of individual VOCs from an urban environment

    NASA Astrophysics Data System (ADS)

    Velasco, Erik; Pressley, Shelley; Grivicke, Rasa; Allwine, Eugene; Jobson, B. Tom; Westberg, Hal; Molina, Luisa T.; Lamb, Brian

    2010-05-01

    As part of the MILAGRO-2006 study a flux tower was deployed at urban Mexico City to measure turbulent fluxes of trace gases. Fluxes of individual volatile organic compounds (VOCs) were measured using a disjunct eddy accumulation (DEA) sampler with ionization detector/gas chromatography (GC-FID) analysis. The DEA method partitions the air into two reservoirs based on the magnitude and direction of the vertical wind speed. The VOCs concentrations in both reservoirs are analyzed and used to determine the fluxes with the vertical wind velocities. Although this method is not as precise as other micrometeorological techniques, such as the eddy covariance method, it provides the ability to directly measure the fluxes of an extended number of individual species using off-line sensors without relying on similarity scaling or empirical parameters. According to our knowledge these measurements constitute the first time that the DEA method was applied in an urban environment. A comparison of the DEA fluxes of selected aromatic and olefinic species measured in parallel by the more accurate eddy covariance and disjunct eddy covariance techniques coupled with fast-response analytical sensors evidenced a flux under-prediction by the DEA method. However, this under-prediction was consistent and constant for the species compared, allowing an analysis of the DEA fluxes in terms of relative magnitudes and ratios. It was found that fluxes of alkane species were the dominant VOCs fluxes, which is consistent with ambient concentration measurements and the local emissions inventory. Among the top 20 mean VOCs fluxes measured during daytime, 11 corresponded to alkanes, followed by 5 aromatics, 2 olefins, 1 alkyne and 1 oxygenated.

  8. Toward finding a universally applicable parameterization of the β factor for Relaxed Eddy Accumulation applications

    NASA Astrophysics Data System (ADS)

    Vogl, Teresa; Hrdina, Amy; Thomas, Christoph

    2016-04-01

    The traditional eddy covariance (EC) technique requires the use of fast responding sensors (≥ 10 Hz) that do not exist for many chemical species found in the atmosphere. In this case, the Relaxed Eddy Accumulation (REA) method offers a means to calculate fluxes of trace gases and other scalar quantities (Businger and Oncley, 1990) and was originally derived from the eddy accumulation method (EA) first proposed by Desjardins (1972). While REA lessens the requirements for sensors and sampling and thus offers practical appeal, it introduces a dependence of the computed flux from a proportionality factor β. The accuracy of the REA fluxes hinges upon the correct determination of β, which was found to vary between 0.40 and 0.63 (Milne et al., 1999, Ammann and Meixner, 2002, Ruppert et al., 2006). However, formulating a universally valid parameterization for β instead of empirical evaluation has remained a conundrum and has been a main limitation for REA. In this study we take a fresh look at the dependencies and mathematical models of β by analyzing eddy covariance (EC) data and REA simulations for two field experiments in drastically contrasting environments: an exclusively physically driven environment in the Dry Valleys of Antarctica, and a biologically active system in a grassland in Germany. The main objective is to work toward a model parameterization for β that can be applied over wide range of surface conditions and forcings without the need for empirical evaluation, which is not possible for most REA applications. Our study discusses two different models to define β: (i) based upon scalar-scalar similarity, in which a different scalar is measured with fast-response sensors as a proxy for the scalar of interest, here referred to as β0; and (ii) computed solely from the vertical wind statistics, assuming a linear relationship between the scalar of interest and the vertical wind speed, referred to as βw. Results are presented for the carbon

  9. Non-destructive techniques based on eddy current testing.

    PubMed

    García-Martín, Javier; Gómez-Gil, Jaime; Vázquez-Sánchez, Ernesto

    2011-01-01

    Non-destructive techniques are used widely in the metal industry in order to control the quality of materials. Eddy current testing is one of the most extensively used non-destructive techniques for inspecting electrically conductive materials at very high speeds that does not require any contact between the test piece and the sensor. This paper includes an overview of the fundamentals and main variables of eddy current testing. It also describes the state-of-the-art sensors and modern techniques such as multi-frequency and pulsed systems. Recent advances in complex models towards solving crack-sensor interaction, developments in instrumentation due to advances in electronic devices, and the evolution of data processing suggest that eddy current testing systems will be increasingly used in the future.

  10. Non-Destructive Techniques Based on Eddy Current Testing

    PubMed Central

    García-Martín, Javier; Gómez-Gil, Jaime; Vázquez-Sánchez, Ernesto

    2011-01-01

    Non-destructive techniques are used widely in the metal industry in order to control the quality of materials. Eddy current testing is one of the most extensively used non-destructive techniques for inspecting electrically conductive materials at very high speeds that does not require any contact between the test piece and the sensor. This paper includes an overview of the fundamentals and main variables of eddy current testing. It also describes the state-of-the-art sensors and modern techniques such as multi-frequency and pulsed systems. Recent advances in complex models towards solving crack-sensor interaction, developments in instrumentation due to advances in electronic devices, and the evolution of data processing suggest that eddy current testing systems will be increasingly used in the future. PMID:22163754

  11. Toward finding a universally applicable parameterization of the β factor for Relaxed Eddy Accumulation applications

    NASA Astrophysics Data System (ADS)

    Vogl, Teresa; Hrdina, Amy; Thomas, Christoph

    2016-04-01

    The traditional eddy covariance (EC) technique requires the use of fast responding sensors (≥ 10 Hz) that do not exist for many chemical species found in the atmosphere. In this case, the Relaxed Eddy Accumulation (REA) method offers a means to calculate fluxes of trace gases and other scalar quantities (Businger and Oncley, 1990) and was originally derived from the eddy accumulation method (EA) first proposed by Desjardins (1972). While REA lessens the requirements for sensors and sampling and thus offers practical appeal, it introduces a dependence of the computed flux from a proportionality factor β. The accuracy of the REA fluxes hinges upon the correct determination of β, which was found to vary between 0.40 and 0.63 (Milne et al., 1999, Ammann and Meixner, 2002, Ruppert et al., 2006). However, formulating a universally valid parameterization for β instead of empirical evaluation has remained a conundrum and has been a main limitation for REA. In this study we take a fresh look at the dependencies and mathematical models of β by analyzing eddy covariance (EC) data and REA simulations for two field experiments in drastically contrasting environments: an exclusively physically driven environment in the Dry Valleys of Antarctica, and a biologically active system in a grassland in Germany. The main objective is to work toward a model parameterization for β that can be applied over wide range of surface conditions and forcings without the need for empirical evaluation, which is not possible for most REA applications. Our study discusses two different models to define β: (i) based upon scalar-scalar similarity, in which a different scalar is measured with fast-response sensors as a proxy for the scalar of interest, here referred to as β0; and (ii) computed solely from the vertical wind statistics, assuming a linear relationship between the scalar of interest and the vertical wind speed, referred to as βw. Results are presented for the carbon

  12. Eddy Current Rail Inspection Using AC Bridge Techniques

    PubMed Central

    Liu, Ze; Koffman, Andrew D; Waltrip, Bryan C; Wang, Yicheng

    2013-01-01

    AC bridge techniques commonly used for precision impedance measurements have been adapted to develop an eddy current sensor for rail defect detection. By using two detection coils instead of just one as in a conventional sensor, we can balance out the large baseline signals corresponding to a normal rail. We have significantly enhanced the detection sensitivity of the eddy current method by detecting and demodulating the differential signal of the two coils induced by rail defects, using a digital lock-in amplifier algorithm. We have also explored compensating for the lift-off effect of the eddy current sensor due to vibrations by using the summing signal of the detection coils to measure the lift-off distance. The dominant component of the summing signal is a constant resulting from direct coupling from the excitation coil, which can be experimentally determined. The remainder of the summing signal, which decreases as the lift-off distance increases, is induced by the secondary eddy current. This dependence on the lift-off distance is used to calibrate the differential signal, allowing for a more accurate characterization of the defects. Simulated experiments on a sample rail have been performed using a computer controlled X-Y moving table with the X-axis mimicking the train’s motion and the Y-axis mimicking the train’s vibrational bumping. Experimental results demonstrate the effectiveness of the new detection method. PMID:26401427

  13. Technique for temperature compensation of eddy-current proximity probes

    NASA Technical Reports Server (NTRS)

    Masters, Robert M.

    1989-01-01

    Eddy-current proximity probes are used in turbomachinery evaluation testing and operation to measure distances, primarily vibration, deflection, or displacment of shafts, bearings and seals. Measurements of steady-state conditions made with standard eddy-current proximity probes are susceptible to error caused by temperature variations during normal operation of the component under investigation. Errors resulting from temperature effects for the specific probes used in this study were approximately 1.016 x 10 to the -3 mm/deg C over the temperature range of -252 to 100 C. This report examines temperature caused changes on the eddy-current proximity probe measurement system, establishes their origin, and discusses what may be done to minimize their effect on the output signal. In addition, recommendations are made for the installation and operation of the electronic components associated with an eddy-current proximity probe. Several techniques are described that provide active on-line error compensation for over 95 percent of the temperature effects.

  14. Eddy current techniques for super duplex stainless steel characterization

    NASA Astrophysics Data System (ADS)

    Camerini, C.; Sacramento, R.; Areiza, M. C.; Rocha, A.; Santos, R.; Rebello, J. M.; Pereira, G.

    2015-08-01

    Super duplex stainless steel (SDSS) is a two-phase material where the microstructure consists of grains of ferrite (δ) and austenite (γ). SDSS exhibit an attractive combination of properties, such as: strength, toughness and stress corrosion cracking resistance. Nevertheless, SDSS attain these properties after a controlled solution heat treatment, leading to a similar volumetric fraction of δ and γ. Any further heat treatment, welding operation for example, can change the balance of the original phases, or may also lead to precipitation of a deleterious phase, such as sigma (σ). For these situations, the material corrosion resistance is severely impaired. In the present study, several SDSS samples with low σ phase content and non-balanced microstructure were intentionally obtained by thermally treating SDSS specimens. Electromagnetic techniques, conventional Eddy Current Testing (ECT) and Saturated Low Frequency Eddy Current (SLOFEC), were employed to characterize the SDSS samples. The results showed that ECT and SLOFEC are reliable techniques to evaluate σ phase presence in SDSS and can provide an estimation of the δ content.

  15. A lee-side eddy and its influence on snow accumulation

    NASA Astrophysics Data System (ADS)

    Gerber, Franziska; Mott, Rebecca; Hoch, Sebastian W.; Lehning, Michael

    2016-04-01

    Knowledge of changes in seasonal mountain snow water resources is essential for e.g. hydropower companies. To successfully predict these changes a fundamental understanding of precipitation patterns and their changes in mountainous terrain is needed. Both, snow accumulation and ablation need to be investigated to make precise predictions of the amount of water stored in seasonal snow cover. Only if the processes governing snow accumulation and ablation are understood with sufficient quantitative accuracy, the evolution of snow water resources under a changing climate can be addressed. Additionally, knowledge of detailed snow accumulation patterns is essential to assess avalanche danger. In alpine terrain, snow accumulation is strongly dependent on the local wind field. Based on the concept of preferential deposition, reduced snow accumulation is expected on the upper windward slope of a mountain due to updrafts, while enhanced snow accumulation should occur through blocking at the windward foot or due to flow separation on the leeward side. However, the understanding of these processes is mainly based on numerical simulations, as they are hard to measure. A LiDAR (Light Detection And Ranging) campaign was conducted in October 2015 in the Dischma valley (Davos, CH) to investigate the local flow field in the lee of the Sattelhorn during a one-day snowfall event. The flow field was monitored using a plane position indicator (PPI) scan at 25/28° and a range height indicator (RHI) scan across the Sattelhorn. Additionally, snow height change measurements on the leeward side of the Sattelhorn were performed by terrestrial laser scanning (TLS). Analyses of the flow field in the framework of preferential deposition are in agreement with the concept of flow separation and preferred snow deposition on leeward slopes. A very persistent eddy that formed over the leeward slope of the Sattelhorn detached from the main flow became evident from the retrievals of the RHI scans. An

  16. Adaptation of a speciation sampling cartridge for measuring ammonia flux from cattle feedlots using relaxed eddy accumulation

    NASA Astrophysics Data System (ADS)

    Baum, K. A.; Ham, J. M.

    Improved measurements of ammonia losses from cattle feedlots are needed to quantify the national NH 3 emissions inventory and evaluate management techniques for reducing emissions. Speciation cartridges composed of glass honeycomb denuders and filter packs were adapted to measure gaseous NH 3 and aerosol NH 4+ fluxes using relaxed eddy accumulation (REA). Laboratory testing showed that a cartridge equipped with four honeycomb denuders had a total capture capacity of 1800 μg of NH 3. In the field, a pair of cartridges was deployed adjacent to a sonic anemometer and an open-path gas analyzer on a mobile tower. High-speed valves were attached to the inlets of the cartridges and controlled by a datalogger so that up- and down-moving eddies were independently sampled based on direction of the vertical wind speed and a user-defined deadband. Air flowed continuously through the cartridges even when not sampling by means of a recirculating air handling system. Eddy covariance measurement of CO 2 and H 2O, as measured by the sonic and open-path gas analyzer, were used to determine the relaxation factor needed to compute REA-based fluxes. The REA system was field tested at the Beef Research Unit at Kansas State University in the summer and fall of 2007. Daytime NH 3 emissions ranged between 68 and 127 μg m -2 s -1; fluxes tended to follow a diurnal pattern correlated with latent heat flux. Daily fluxes of NH 3 were between 2.5 and 4.7 g m -2 d -1 and on average represented 38% of fed nitrogen. Aerosol NH 4+ fluxes were negligible compared with NH 3 emissions. An REA system designed around the high-capacity speciation cartridges can be used to measure NH 3 fluxes from cattle feedlots and other strong sources. The system could be adapted to measure fluxes of other gases and aerosols.

  17. Characterization of Magnetron Sputtered Coatings by Pulsed Eddy Current Techniques

    SciTech Connect

    Mulligan, Chris; Lee Changqing; Danon, Yaron

    2005-04-09

    A method that uses induced pulsed eddy currents for characterization of thick magnetron sputtered Nb coatings on steel is presented in this paper. The objectives of this work are to develop a system for rapid quantitative nondestructive inspection of coatings as well as to determine the correlation between coating properties, such as density and purity, and eddy current measured resistivity of coatings. A two-probe differential system having higher sensitivity and less noise than a one-probe system with 2-D scanning ability was developed.

  18. A High Frequency Response Relaxed Eddy Accumulation Flux Measurement System for Sampling Short-Lived Biogenic Volatile Organic Compounds

    EPA Science Inventory

    A second-generation relaxed eddy accumulation system was built and tested with the capability to measure vertical biogenic volatile organic compound (VOC) fluxes at levels as low as 10 µg C m−2 hr−1. The system features a continuous, integrated gas-phase ozo...

  19. Eddy current signal deconvolution technique for the improvement of steam generator tubing burst pressure predictions.

    SciTech Connect

    Petri, M. C.; Wei, T. Y. C.; Kupperman, D. S.; Reifman, J.; Morman, J. A.

    2000-01-01

    Eddy current techniques are extremely sensitive to the presence of axial cracks in nuclear power plant steam generator tube walls, but they are equally sensitive to the presence of dents, fretting, support structures, corrosion products, and other artifacts. Eddy current signal interpretation is further complicated by cracking geometries more complex than a single axial crack. Although there has been limited success in classifying and sizing defects through artificial neural networks, the ability to predict tubing integrity has, so far, eluded modelers. In large part, this lack of success stems from an inability to distinguish crack signals from those arising from artifacts. We present here a new signal processing technique that deconvolves raw eddy current voltage signals into separate signal contributions from different sources, which allows signals associated with a dominant crack to be identified. The signal deconvolution technique, combined with artificial neural network modeling, significantly improves the prediction of tube burst pressure from bobbin-coil eddy current measurements of steam generator tubing.

  20. VOC flux measurements using a novel Relaxed Eddy Accumulation GC-FID system in urban Houston, Texas

    NASA Astrophysics Data System (ADS)

    Park, C.; Schade, G.; Boedeker, I.

    2008-12-01

    Houston experiences higher ozone production rates than most other major cities in the US, which is related to high anthropogenic VOC emissions from both area/mobile sources (car traffic) and a large number of petrochemical facilities. The EPA forecasts that Houston is likely to still violate the new 8-h NAAQS in 2020. To monitor neighborhood scale pollutant fluxes, we established a tall flux tower installation a few kilometers north of downtown Houston. We measure energy and trace gas fluxes, including VOCs from both anthropogenic and biogenic emission sources in the urban surface layer using eddy covariance and related techniques. Here, we describe a Relaxed Eddy Accumulation (REA) system combined with a dual-channel GC-FID used for VOC flux measurements, including first results. Ambient air is sampled at approximately 15 L min-1 through a 9.5 mm OD PFA line from 60 m above ground next to a sonic anemometer. Subsamples of this air stream are extracted through an ozone scrubber and pushed into two Teflon bag reservoirs, from which they are transferred to the GC pre-concentration units consisting of carbon-based adsorption traps encapsulated in heater blocks for thermal desorption. We discuss the performance of our system and selected measurement results from the 2008 spring and summer seasons in Houston. We present diurnal variations of the fluxes of the traffic tracers benzene, toluene, ethylbenzene, and xylenes (BTEX) during different study periods. Typical BTEX fluxes ranged from -0.36 to 3.10 mg m-2 h-1 for benzene, and -0.47 to 5.04 mg m-2 h-1 for toluene, and exhibited diurnal cycles with two dominant peaks related to rush-hour traffic. A footprint analysis overlaid onto a geographic information system (GIS) will be presented to reveal the dominant emission sources and patterns in the study area.

  1. Field comparison of an eddy accumulation and an aerodynamic-gradient system for measuring pesticide volatilization fluxes

    USGS Publications Warehouse

    Majewski, M.; Desjardina, R.; Rochette, P.; Pattey, E.; Selber, J.; Glotfelty, D.

    1993-01-01

    The field experiment reported here applied the relaxed eddy accumulation (REA) technique to the measurement of triallate (TA) and trifluralin (TF) volatilization from fallow soil. A critical analysis of the REA system used in this experiment is done, and the fluxes are compared to those obtained by the aerodynamic-gradient (AG) technique. The measured cumulative volatilization losses, corrected for the effective upwind source area (footprint), for the AG system were higher than with the REA system. The differences between the methods over the first 5 days of the experiment were 27 and 13% for TA and TF, respectively. A mass balance based on the amount of parent compounds volatilized from soil during the first 5 days of the experiment showed a 110 and 70% and a 79 and 61% accountability for triallate and trifluralin by the AG and REA methods, respectively. These results also show that the non-footprint-corrected AG flux values underestimated the volatilization flux by approximately 16%. The footprint correction model used in this experiment does not presently have the capability of accounting for changes in atmospheric stability. However, these values still provide an indication of the most likely upwind area affecting the evaporative flux estimations. The soil half-lives for triallate and trifluralin were 9.8 and 7.0 days, respectively. ?? 1992 American Chemical Society.

  2. Parametric Studies and Optimization of Eddy Current Techniques through Computer Modeling

    SciTech Connect

    Todorov, E. I.

    2007-03-21

    The paper demonstrates the use of computer models for parametric studies and optimization of surface and subsurface eddy current techniques. The study with high-frequency probe investigates the effect of eddy current frequency and probe shape on the detectability of flaws in the steel substrate. The low-frequency sliding probe study addresses the effect of conductivity between the fastener and the hole, frequency and coil separation distance on detectability of flaws in subsurface layers.

  3. Thickness Evaluation of Aluminium Plate Using Pulsed Eddy Current Technique

    NASA Astrophysics Data System (ADS)

    Singh, Gurpartap; Bapat, Harsh Madhukar; Singh, Bhanu Pratap; Bandyopadhyay, Manojit; Puri, Rakesh Kumar; Badodkar, Deepak Narayanrao

    2013-10-01

    This paper describes a pulsed eddy current (PEC) based non-destructive testing system used for detection of thickness variation in aluminium plate. A giant magneto-resistive sensor has been used instead of pick up coil for detecting resultant magnetic field. The PEC response signals obtained from 1 to 5 mm thickness change in aluminium plate were investigated. Two time domain features, namely peak value and time to peak, of PEC response were used for extracting information about thickness variation in aluminium plate. The variation of peak value and time to peak with thickness was compared. A program was developed to display the thickness variation of the tested sample.

  4. The eddy-current technique for nondestructive evaluation of generator retaining rings: Feasibility study: Interim report

    SciTech Connect

    Elmo, P.M.; Nottingham, L.D.

    1988-05-01

    An evaluation of the feasibility of using eddy current nondestructive inspection techniques to detect intergranular stress corrosion in generator rotor retaining rings was conducted by the EPRI NDE Center. Experiments were conducted using a bend-bar containing representative stress corrosion damage, a calibration block containing electrical discharge machined (EDM) notches, and four retired retaining rings containing EDM notches and stress corrosion damage. An eddy current transducer transport was designed and fabricated to interface with an existing computer-controlled, two-axis positioner and digital eddy current data acquisition system. Test results of experiments performed with this equipment on the retaining ring test-bed provided experimental validation of the eddy current method's feasibility as a retaining ring inspection method. Details are given of the system and its performance under laboratory and simulated service-inspection conditions. 9 refs., 47 figs.

  5. Determination of the terpene flux from orange species and Norway spruce by relaxed eddy accumulation

    NASA Astrophysics Data System (ADS)

    Christensen, C. S.; Hummelshøj, P.; Jensen, N. O.; Larsen, B.; Lohse, C.; Pilegaard, K.; Skov, H.

    Terpene fluxes from a Norway spruce ( Picea abies) forest and an orange orchard ( Citrus clementii and Citrus sinensis) were measured by relaxed eddy accumulation (REA) during summer 1997. α-pinene and β-pinene were the most abundant terpenes emitted from Norway spruce and constituted approximately 70% of the flux. A much lower flux was observed for myrcene, limonene and γ-terpinene and both α-terpinene and camphor were only occasionally detected. The average terpene flux was 107.6 ng m -2 s -1 which corresponds to 0.73 μg g(dw) -1 h -1 (30°C) when calculated relatively the weight of the dry biomass. The five terpenes which were detected in all samples at the orange orchard were limonene, sabinene, α-pinene, trans-ocimene and β-pinene with an average flux of 126.3 ng m -2 s -1. Cis-ocimene, linalool and myrcene were occasionally detected but no systematic upward or downward flux was observed. The results from a laboratory intercomparison made in Spain deviated by maximum 7%. The flux measured at the two sites exhibited a strong diurnal variation with maximum in the afternoon and minimum in the morning hours and evenings. The applied REA system is new in its design and the major advantage is that the air is sampled at a constant flow rate on the adsorbent tubes. This is realised by having two primary Teflon lines with a relatively large flow rate (6 l min -1). The air is then sampled from these two Teflon lines on two identical adsorbent tubes at a constant and much lower rate by using two precision pumps operated at approximately 60 ml min -1. The terpenes collected on the adsorbent tubes were significantly decomposed by ozone during sampling unless ozone scrubbers were applied.

  6. Continuous determination of land-atmosphere Hg0 exchange using a novel Relaxed Eddy Accumulation design

    NASA Astrophysics Data System (ADS)

    Osterwalder, Stefan; Fritsche, Johannes; Nilsson, Mats B.; Alewell, Christine; Bishop, Kevin

    2015-04-01

    The fate of anthropogenic emissions to the atmosphere is influenced by the exchange of elemental mercury (Hg0) with the earth surface. However, it remains challenging to quantify these exchanges which hold the key to a better understanding of mercury cycling at different scales, from the entire earth to specific environments. To better test hypotheses about land-atmosphere Hg interactions, we applied dynamic flux chambers (DFCs) for short term measurements and developed a novel Relaxed Eddy Accumulation (REA) design for continuous flux monitoring. Accurate determination of Hg0 fluxes has proven difficult due to the technical challenges presented by the small concentration differences (< 1 ng m-3) between updrafts and downdrafts. To address this we present a dual-intake, single analyzer REA system including a calibration module for periodic quality-control measurements with reference gases. To demonstrate the system performance, we present results from two contrasting environments: In February 2012 REA monitored a heterogeneous urban surface in the center of Basel, Switzerland where an average flux of 14 ng m-2 h-1 was detected with a distinct diurnal pattern. In May 2012, the REA monitored a boreal mire in northern Sweden with different turbulence regimes and Hg0 sink/source characteristics. During the snowmelt period in May 2012 the Hg0 flux averaged at 2 ng m-2 h-1. In order to better quantify inputs and outputs of Hg from boreal landscapes, we subsequently monitored the land-atmosphere exchange of Hg0 during a course of a year and compared the fluxes occasionally with DFC measurements. The amount of Hg0 volatilized from boreal mires was at a similar level as the annual export of Hg in stream water, identifying the mire as net source of Hg to neighboring environments. We believe that this dual-inlet, single detector approach is a significant innovation which can help realize the potential of REA for continuous, long-term determination of land-atmosphere Hg0

  7. A high-frequency response relaxed eddy accumulation flux measurement system for sampling short-lived biogenic volatile organic compounds

    NASA Astrophysics Data System (ADS)

    Arnts, Robert R.; Mowry, Fred L.; Hampton, Gary A.

    2013-05-01

    second-generation relaxed eddy accumulation system was built and tested with the capability to measure vertical biogenic volatile organic compound (VOC) fluxes at levels as low as 10 µg C m-2 hr-1. The system features a continuous, integrated gas-phase ozone removal procedure to allow for the measurement of highly reactive species such as β-caryophyllene and polar terpenoids such as linalool. A two-component internal standard continuously added to the accumulators was used to correct for switching-induced volumetric errors and as a check on VOC losses exceeding accumulator tube adsorption limits. In addition, the internal standards were used to demonstrate that accumulators quickly return to target flow rates at segregation valve switching frequencies up to at least 0.8 Hz. The system was able to measure daytime hourly fluxes of individual biogenic VOC including oxygenated terpenoids, monoterpenes, and sesquiterpenes.

  8. A dual-inlet, single detector relaxed eddy accumulation system for long-term measurement of mercury flux

    NASA Astrophysics Data System (ADS)

    Osterwalder, S.; Fritsche, J.; Alewell, C.; Schmutz, M.; Nilsson, M. B.; Jocher, G.; Sommar, J.; Rinne, J.; Bishop, K.

    2016-02-01

    The fate of anthropogenic emissions of mercury (Hg) to the atmosphere is influenced by the exchange of elemental Hg with the earth surface. This exchange holds the key to a better understanding of Hg cycling from local to global scales, which has been difficult to quantify. To advance research about land-atmosphere Hg interactions, we developed a dual-inlet, single detector relaxed eddy accumulation (REA) system. REA is an established technique for measuring turbulent fluxes of trace gases and aerosol particles in the atmospheric surface layer. Accurate determination of gaseous elemental mercury (GEM) fluxes has proven difficult due to technical challenges presented by extremely small concentration differences (typically < 0.5 ng m-3) between updrafts and downdrafts. We present an advanced REA design that uses two inlets and two pairs of gold cartridges for continuous monitoring of GEM fluxes. This setup reduces the major uncertainty created by the sequential sampling in many previous designs. Additionally, the instrument is equipped with a GEM reference gas generator that monitors drift and recovery rates. These innovations facilitate continuous, autonomous measurement of GEM flux. To demonstrate the system performance, we present results from field campaigns in two contrasting environments: an urban setting with a heterogeneous fetch and a boreal peatland during snowmelt. The observed average emission rates were 15 and 3 ng m-2 h-1, respectively. We believe that this dual-inlet, single detector approach is a significant improvement of the REA system for ultra-trace gases and can help to advance our understanding of long-term land-atmosphere GEM exchange.

  9. Detection and Sizing of Fatigue Cracks in Steel Welds with Advanced Eddy Current Techniques

    NASA Astrophysics Data System (ADS)

    Todorov, E. I.; Mohr, W. C.; Lozev, M. G.

    2008-02-01

    Butt-welded specimens were fatigued to produce cracks in the weld heat-affected zone. Advanced eddy current (AEC) techniques were used to detect and size the cracks through a coating. AEC results were compared with magnetic particle and phased-array ultrasonic techniques. Validation through destructive crack measurements was also conducted. Factors such as geometry, surface treatment, and crack tightness interfered with depth sizing. AEC inspection techniques have the potential of providing more accurate and complete sizing flaw data for manufacturing and in-service inspections.

  10. Studies of the eddy structure in the lower ionosphere by the API technique

    NASA Astrophysics Data System (ADS)

    Bakhmetieva, Nataliya V.; Grigoriev, Gennadii I.; Lapin, Victor G.

    2016-07-01

    We present a new application of the API technique to study of turbulent phenomena in the lower ionosphere. The main objective of these studies is experimental diagnostics of natural ordered eddy structures at the altitudes of the mesosphere and lower thermosphere, such as those that occur when internal gravity waves propagate in stratified flows in the atmospheric boundary layer. To this end, we considered the impact of eddy motions in the mesosphere and lower thermosphere on the relaxation time and the frequency of the signal scattered by periodic irregularities. Theoretical study of eddy structures base on experiments using SURA heating facility (56,14 N; 44,1 W). It is known, artificial periodic irregularities (APIs) are formed in the field of the powerful standing wave as a result of the interference of the incident wave and reflected from the ionosphere (Belikovich et al., Ionospheric Research by Means of Artificial Periodic Irregularities - 2002. Katlenburg-Lindau, Germany. Copernicus GmbH. 160 p.). The relaxation or decay of the periodic structure is specified by the ambipolar diffusion process. The atmospheric turbulence causes reduction of the amplitude and decay time of the API scattered signal in comparison with the diffusion time. We found a relation between the eddy period and the characteristic decay time of scattered signal, for which the synchronism of the waves scattered by a periodic structure is broken. Besides, it is shown, when the eddy structure moves by a horizontal wind exists at these heights, the frequency of the radio wave scattered by API structure will periodically increase and decrease compared with the frequency of the radiated diagnostic (probing) radio-wave. The work was supported by the Russian Science Foundation under grant No 14-12-00556.

  11. Application of Eddy Current Techniques for Orbiter Reinforced Carbon-Carbon Structural Health Monitoring

    NASA Technical Reports Server (NTRS)

    Wincheski, Buzz; Simpson, John

    2005-01-01

    The development and application of advanced nondestructive evaluation techniques for the Reinforced Carbon-Carbon (RCC) components of the Space Shuttle Orbiter Leading Edge Structural Subsystem (LESS) was identified as a crucial step toward returning the shuttle fleet to service. In order to help meet this requirement, eddy current techniques have been developed for application to RCC components. Eddy current technology has been found to be particularly useful for measuring the protective coating thickness over the reinforced carbon-carbon and for the identification of near surface cracking and voids in the RCC matrix. Testing has been performed on as manufactured and flown RCC components with both actual and fabricated defects representing impact and oxidation damage. Encouraging initial results have led to the development of two separate eddy current systems for in-situ RCC inspections in the orbiter processing facility. Each of these systems has undergone blind validation testing on a full scale leading edge panel, and recently transitioned to Kennedy Space Center to be applied as a part of a comprehensive RCC inspection strategy to be performed in the orbiter processing facility after each shuttle flight.

  12. Field comparison of disjunct and conventional eddy covariance techniques for trace gas flux measurements.

    PubMed

    Rinne, J; Douffet, T; Prigent, Y; Durand, P

    2008-04-01

    A field intercomparison experiment of the disjunct eddy covariance (DEC) and the conventional eddy covariance (EC) techniques was conducted over a grass field. The half-hourly water vapor fluxes measured by the DEC were within the estimated uncertainty from the fluxes measured by the EC. On the average there was a slight overestimation (<10%) of the fluxes measured by the DEC during the day and underestimation during the night as compared to the fluxes measured by the EC. As this bias does not appear in the simulated DEC measurements it is likely to be due to instrumental problems. The insensitivity of the quality of the fluxes measured by the DEC method to the deficiencies in the gas analysis shows the robustness of this new approach for measuring the surface-atmosphere exchange of trace gases.

  13. Pulsed remote field eddy current technique applied to non-magnetic flat conductive plates

    NASA Astrophysics Data System (ADS)

    Yang, Binfeng; Zhang, Hui; Zhang, Chao; Zhang, Zhanbin

    2013-12-01

    Non-magnetic metal plates are widely used in aviation and industrial applications. The detection of cracks in thick plate structures, such as multilayered structures of aircraft fuselage, has been challenging in nondestructive evaluation societies. The remote field eddy current (RFEC) technique has shown advantages of deep penetration and high sensitivity to deeply buried anomalies. However, the RFEC technique is mainly used to evaluate ferromagnetic tubes. There are many problems that should be fixed before the expansion and application of this technique for the inspection of non-magnetic conductive plates. In this article, the pulsed remote field eddy current (PRFEC) technique for the detection of defects in non-magnetic conducting plates was investigated. First, the principle of the PRFEC technique was analysed, followed by the analysis of the differences between the detection of defects in ferromagnetic and non-magnetic plain structures. Three different models of the PRFEC probe were simulated using ANSYS. The location of the transition zone, defect detection sensitivity and the ability to detect defects in thick plates using three probes were analysed and compared. The simulation results showed that the probe with a ferrite core had the highest detecting ability. The conclusions derived from the simulation study were also validated by conducting experiments.

  14. Thickness measurement of multi-layer conductive coatings using multifrequency eddy current techniques

    NASA Astrophysics Data System (ADS)

    Zhang, Dejun; Yu, Yating; Lai, Chao; Tian, Guiyun

    2016-07-01

    To ensure the key structural performance in high-temperature and high-stress environments, thermal barrier coatings (TBCs) are often adopted in engineering. The thickness of these multi-layer conductive coatings is an important quality indicator. In order to measure the thickness of multi-layer conductive coatings, a new measurement approach is presented using eddy current testing techniques, and then, an inversion algorithm is proposed and proved efficient and applicable, of which the maximum experimental relative error is within 10%. Therefore, the new approach can be effectively applied to thickness measurement of multi-layer conductive coatings such as TBCs.

  15. Long-term measurement of terpenoid flux above a Larix kaempferi forest using a relaxed eddy accumulation method

    NASA Astrophysics Data System (ADS)

    Mochizuki, Tomoki; Tani, Akira; Takahashi, Yoshiyuki; Saigusa, Nobuko; Ueyama, Masahito

    2014-02-01

    Terpenoids emitted from forests contribute to the formation of secondary organic aerosols and affect the carbon budgets of forest ecosystems. To investigate seasonal variation in terpenoid flux involved in the aerosol formation and carbon budget, we measured the terpenoid flux of a Larix kaempferi forest between May 2011 and May 2012 by using a relaxed eddy accumulation method. Isoprene was emitted from a fern plant species Dryopteris crassirhizoma on the forest floor and monoterpenes from the L. kaempferi. α-Pinene was the dominant compound, but seasonal variation of the monoterpene composition was observed. High isoprene and monoterpene fluxes were observed in July and August. The total monoterpene flux was dependent on temperature, but several unusual high positive fluxes were observed after rain fall events. We found a good correlation between total monoterpene flux and volumetric soil water content (r = 0.88), and used this correlation to estimate monoterpene flux after rain events and calculate annual terpenoid emissions. Annual carbon emission in the form of total monoterpenes plus isoprene was determined to be 0.93% of the net ecosystem exchange. If we do not consider the effect of rain fall, carbon emissions may be underestimated by about 50%. Our results suggest that moisture conditions in the forest soil is a key factor controlling the monoterpene emissions from the forest ecosystem.

  16. [Research progress on urban carbon fluxes based on eddy covariance technique].

    PubMed

    Liu, Min; Fu, Yu-Ling; Yang, Fang

    2014-02-01

    Land use change and fossil fuel consumption due to urbanization have made significant effect on global carbon cycle and climate change. Accurate estimating and understanding of the carbon budget and its characteristics are the premises for studying carbon cycle and its driving mechanisms in urban system. Based on the theory of eddy covariance (EC) technique, the characteristics atmospheric boundary layer and carbon cycle in urban area, this study systematically reviewed the principles of CO2 flux monitoring in urban system with EC technique, and then summarized the problems faced in urban CO2 flux monitoring and the method for data processing and further assessment. The main research processes on urban carbon fluxes with EC technique were also illustrated. The results showed that the urban surface was mostly acting as net carbon source. The CO2 exchange between urban surface and atmosphere showed obvious diurnal, weekly and seasonal variation resulted from the vehicle exhaust, domestic heating and vegetation respiration. However, there still exist great uncertainties in urban flux measurement and its explanation due to high spatial heterogeneity and complex distributions of carbon source/sink in urban environments. In the end, we suggested that further researches on EC technique and data assessment in complex urban area should be strengthened. It was also requisite to develop models of urban carbon cycle on the basis of the system principle, to investigate the influencing mechanism and variability of urban cycle at regional scale with spatial analysis technique. PMID:24830264

  17. [Research progress on urban carbon fluxes based on eddy covariance technique].

    PubMed

    Liu, Min; Fu, Yu-Ling; Yang, Fang

    2014-02-01

    Land use change and fossil fuel consumption due to urbanization have made significant effect on global carbon cycle and climate change. Accurate estimating and understanding of the carbon budget and its characteristics are the premises for studying carbon cycle and its driving mechanisms in urban system. Based on the theory of eddy covariance (EC) technique, the characteristics atmospheric boundary layer and carbon cycle in urban area, this study systematically reviewed the principles of CO2 flux monitoring in urban system with EC technique, and then summarized the problems faced in urban CO2 flux monitoring and the method for data processing and further assessment. The main research processes on urban carbon fluxes with EC technique were also illustrated. The results showed that the urban surface was mostly acting as net carbon source. The CO2 exchange between urban surface and atmosphere showed obvious diurnal, weekly and seasonal variation resulted from the vehicle exhaust, domestic heating and vegetation respiration. However, there still exist great uncertainties in urban flux measurement and its explanation due to high spatial heterogeneity and complex distributions of carbon source/sink in urban environments. In the end, we suggested that further researches on EC technique and data assessment in complex urban area should be strengthened. It was also requisite to develop models of urban carbon cycle on the basis of the system principle, to investigate the influencing mechanism and variability of urban cycle at regional scale with spatial analysis technique.

  18. Seagrass metabolism across a productivity gradient using the eddy covariance, Eulerian control volume, and biomass addition techniques

    NASA Astrophysics Data System (ADS)

    Long, Matthew H.; Berg, Peter; Falter, James L.

    2015-05-01

    The net ecosystem metabolism of the seagrass Thalassia testudinum was studied across a nutrient and productivity gradient in Florida Bay, Florida, using the Eulerian control volume, eddy covariance, and biomass addition techniques. In situ oxygen fluxes were determined by a triangular Eulerian control volume with sides 250 m long and by eddy covariance instrumentation at its center. The biomass addition technique evaluated the aboveground seagrass productivity through the net biomass added. The spatial and temporal resolutions, accuracies, and applicability of each method were compared. The eddy covariance technique better resolved the short-term flux rates and the productivity gradient across the bay, which was consistent with the long-term measurements from the biomass addition technique. The net primary production rates from the biomass addition technique, which were expected to show greater autotrophy due to the exclusion of sediment metabolism and belowground production, were 71, 53, and 30 mmol carbon m-2 d-1 at 3 sites across the bay. The net ecosystem metabolism was 35, 25, and 11 mmol oxygen m-2 d-1 from the eddy covariance technique and 10, -103, and 14 mmol oxygen m-2 d-1 from the Eulerian control volume across the same sites, respectively. The low-flow conditions in the shallow bays allowed for periodic stratification and long residence times within the Eulerian control volume that likely reduced its precision. Overall, the eddy covariance technique had the highest temporal resolution while producing accurate long-term flux rates that surpassed the capabilities of the biomass addition and Eulerian control volume techniques in these shallow coastal bays.

  19. Nuclear Technology. Course 32: Nondestructive Examination (NDE) Techniques II. Module 32-5, Fundamentals of Eddy Current Testing.

    ERIC Educational Resources Information Center

    Espy, John

    This fifth in a series of six modules for a course titled Nondestructive Examination (NDE) Techniques II describes the fundamental concepts applicable to eddy current testing in general. The module follows a typical format that includes the following sections: (1) introduction, (2) module prerequisites, (3) objectives, (4) notes to…

  20. Nuclear Technology. Course 32: Nondestructive Examination (NDE) Techniques II. Module 32-6, Operation of Eddy Current Test Equipment.

    ERIC Educational Resources Information Center

    Espy, John; Selleck, Ben

    This sixth in a series of six modules for a course titled Nondestructive Examination (NDE) Techniques II details eddy current examination of steam generator tubing. The module follows a typical format that includes the following sections: (1) introduction, (2) module prerequisites, (3) objectives, (4) notes to instructor/student, (5) subject…

  1. Four-year measurement of methane flux over a temperate forest with a relaxed eddy accumulation method

    NASA Astrophysics Data System (ADS)

    Sakabe, A.; Kosugi, Y.; Ueyama, M.; Hamotani, K.; Takahashi, K.; Iwata, H.; Itoh, M.

    2013-12-01

    Forests are generally assumed to be an atmospheric methane (CH4) sink (Le Mer and Roger, 2001). However, under Asian monsoon climate, forests are subject to wide spatiotemporal range in soil water status, where forest soils often became water-saturated condition heterogeneously. In such warm and humid conditions, forests may act as a CH4 source and/or sink with considerable spatiotemporal variations. Micrometeorological methods such as eddy covariance (EC) method continuously measure spatially-representative flux at a canopy scale without artificial disturbance. In this study, we measured CH4 fluxes over a temperate forest during four-year period using a CH4 analyzer based on tunable diode laser spectroscopy detection with a relaxed eddy accumulation (REA) method (Hamotani et al., 1996, 2001). We revealed the amplitude and seasonal variations of canopy-scale CH4 fluxes. The REA method is the attractive alternative to the EC method to measure trace-gas flux because it allows the use of analyzers with an optimal integration time. We also conducted continuous chamber measurements on forest floor to reveal spatial variations in soil CH4 fluxes and its controlling processes. The observations were made in an evergreen coniferous forest in central Japan. The site has a warm temperate monsoon climate with wet summer. Some wetlands were located in riparian zones along streams within the flux footprint area. For the REA method, the sonic anemometer (SAT-550, Kaijo) was mounted on top of the 29-m-tall tower and air was sampled from just below the sonic anemometer to reservoirs according to the direction of vertical wind velocity (w). After accumulating air for 30 minutes, the air in the reservoirs was pulled into a CO2/H2O gas analyzer (LI-840, Li-Cor) and a CH4 analyzer (FMA-200, Los Gatos Research). Before entering the analyzers, the sampled air was dried using a gas dryer (PD-50 T-48; Perma Pure Inc.). The REA flux is obtained from the difference in the mean concentrations

  2. Eddy Covariance Flux Measurements of Pollutant Gases in the Mexico City Urban Area: a Useful Technique to Evaluate Emissions inventories

    NASA Astrophysics Data System (ADS)

    Velasco, E.; Grivicke, R.; Pressley, S.; Allwine, G.; Jobson, T.; Westberg, H.; Lamb, B.; Ramos, R.; Molina, L.

    2007-12-01

    Direct measurements of emissions of pollutant gases that include all major and minor emissions sources in urban areas are a missing requirement to improve and evaluate emissions inventories. The quality of an urban emissions inventory relies on the accuracy of the information of anthropogenic activities, which in many cases is not available, in particular in urban areas of developing countries. As part of the MCMA-2003 field campaign, we demonstrated the feasibility of using eddy covariance (EC) techniques coupled with fast-response sensors to measure fluxes of volatile organic compounds (VOCs) and CO2 from a residential district of Mexico City. Those flux measurements demonstrated to be also a valuable tool to evaluate the emissions inventory used for air quality modeling. With the objective to confirm the representativeness of the 2003 flux measurements in terms of magnitude, composition and diurnal distribution, as well to evaluate the most recent emissions inventory, a second flux system was deployed in a different district of Mexico City during the 2006 MILAGRO field campaign. This system was located in a busy district surrounded by congested avenues close to the center of the city. In 2003 and 2006 fluxes of olefins and CO2 were measured by the EC technique using a Fast Isoprene Sensor calibrated with a propylene standard and an open path Infrared Gas Analyzer (IRGA), respectively. Fluxes of aromatic and oxygenated VOCs were analyzed by Proton Transfer Reaction-Mass Spectroscopy (PTR-MS) and the disjunct eddy covariance (DEC) technique. In 2006 the number of VOCs was extended using a disjunct eddy accumulation (DEA) system. This system collected whole air samples as function of the direction of the vertical wind component, and the samples were analyzed on site by gas chromatography / flame ionization detection (GC-FID). In both studies we found that the urban surface is a net source of CO2 and VOCs. The diurnal patterns were similar, but the 2006 fluxes

  3. Assessment of benthic flux of dissolved organic carbon in wetland and estuarine sediments using the eddy-correlation technique

    NASA Astrophysics Data System (ADS)

    Swett, M. P.; Amirbahman, A.; Boss, E.

    2009-12-01

    Wetland and estuarine sediments release significant amounts of dissolved organic carbon (DOC) due to high levels of microbial activity, particularly sulfate reduction. Changes in climate and hydrologic conditions have a potential to alter DOC release from these systems as well. This is a concern, as high levels of DOC can lead to mobilization of toxic metals and organics in natural waters. In addition, source waters high in DOC produce undesirable disinfection byproducts in water treatment. Various in situ methods, such as peepers and sediment core centrifugation, exist to quantify vertical benthic fluxes of DOC and other dissolved species from the sediment-water interface (SWI). These techniques, however, are intrusive and involve disturbance of the sediment environment. Eddy-correlation allows for real-time, non-intrusive, in situ flux measurement of important analytes, such as O2 and DOC. An Acoustic Doppler Velocimeter (ADV) is used to obtain three-dimensional fluid velocity measurements. The eddy-correlation technique employs the mathematical separation of fluid velocity into mean velocity and fluctuating velocity components, with the latter representing turbulent eddy velocity. DOC concentrations are measured using a colored dissolved organic matter (CDOM) fluorometer, and instantaneous vertical flux is determined from the correlated data. This study assesses DOC flux at three project sites: a beaver pond in the Lower Penobscot Watershed, Maine; a mudflat in Penobscot River, Maine; and a mudflat in Great Bay, New Hampshire. Eddy flux values are compared with results obtained using peepers and centrifugation, as well as vertical profiling.

  4. Nitrous oxide emissions from a commercial cornfield (Zea mays) measured using the eddy covariance technique

    NASA Astrophysics Data System (ADS)

    Huang, H.; Wang, J.; Hui, D.; Miller, D. R.; Bhattarai, S.; Dennis, S.; Smart, D.; Sammis, T.; Reddy, K. C.

    2014-12-01

    Increases in observed atmospheric concentrations of the long-lived greenhouse gas nitrous oxide (N2O) have been well documented. However, information on event-related instantaneous emissions during fertilizer applications is lacking. With the development of fast-response N2O analyzers, the eddy covariance (EC) technique can be used to gather instantaneous measurements of N2O concentrations to quantify the exchange of nitrogen between the soil and atmosphere. The objectives of this study were to evaluate the performance of a new EC system, to measure the N2O flux with the system, and finally to examine relationships of the N2O flux with soil temperature, soil moisture, precipitation, and fertilization events. An EC system was assembled with a sonic anemometer and a fast-response N2O analyzer (quantum cascade laser spectrometer) and applied in a cornfield in Nolensville, Tennessee during the 2012 corn growing season (4 April-8 August). Fertilizer amounts totaling 217 kg N ha-1 were applied to the experimental site. Results showed that this N2O EC system provided reliable N2O flux measurements. The cumulative emitted N2O amount for the entire growing season was 6.87 kg N2O-N ha-1. Seasonal fluxes were highly dependent on soil moisture rather than soil temperature. This study was one of the few experiments that continuously measured instantaneous, high-frequency N2O emissions in crop fields over a growing season of more than 100 days.

  5. Microplate Technique for Determining Accumulation of Metals by Algae

    PubMed Central

    Hassett, James M.; Jennett, J. Charles; Smith, James E.

    1981-01-01

    A microplate technique was developed to determine the conditions under which pure cultures of algae removed heavy metals from aqueous solutions. Variables investigated included algal species and strain, culture age (11 and 44 days), metal (mercury, lead, cadmium, and zinc), pH, effects of different buffer solutions, and time of exposure. Plastic, U-bottomed microtiter plates were used in conjunction with heavy metal radionuclides to determine concentration factors for metal-alga combinations. The technique developed was rapid, statistically reliable, and economical of materials and cells. Results (expressed as concentration factors) were in reasonably good agreement with literature values. All species of algae studied removed mercury from solution. Green algae proved better at accumulating cadmium than did blue-green algae. No alga studied removed zinc, perhaps because cells were maintained in the dark during the labeling period. Chlamydomonas sp. proved superior in ability to remove lead from solution. PMID:16345764

  6. Non destructive technique for cracks detection by an eddy current in differential mode for steel frames

    SciTech Connect

    Harzalla, S. Chabaat, M.; Belgacem, F. Bin Muhammad

    2014-12-10

    In this paper, a nondestructive technique is used as a tool to control cracks and microcracks in materials. A simulation by a numerical approach such as the finite element method is employed to detect cracks and eventually; to study their propagation using a crucial parameter such as the stress intensity factor. This approach has been used in the aircraft industry to control cracks. Besides, it makes it possible to highlight the defects of parts while preserving the integrity of the controlled products. On the other side, it is proven that the reliability of the control of defects gives convincing results for the improvement of the quality and the safety of the material. Eddy current testing (ECT) is a standard technique in industry for the detection of surface breaking flaws in magnetic materials such as steels. In this context, simulation tools can be used to improve the understanding of experimental signals, optimize the design of sensors or evaluate the performance of ECT procedures. CEA-LIST has developed for many years semi-analytical models embedded into the simulation platform CIVA dedicated to non-destructive testing. The developments presented herein address the case of flaws located inside a planar and magnetic medium. Simulation results are obtained through the application of the Volume Integral Method (VIM). When considering the ECT of a single flaw, a system of two differential equations is derived from Maxwell equations. The numerical resolution of the system is carried out using the classical Galerkin variant of the Method of Moments. Besides, a probe response is calculated by application of the Lorentz reciprocity theorem. Finally, the approach itself as well as comparisons between simulation results and measured data are presented.

  7. Development of Eddy Current Techniques for Detection of Deep Fatigue Cracks in Multi-Layer Airframe Components

    NASA Technical Reports Server (NTRS)

    Wincheski, Russell A.

    2008-01-01

    Thick, multi-layer aluminum structure has been widely used in aircraft design in critical wing splice areas. The multi-layer structure generally consists of three or four aluminum layers with different geometry and varying thickness, which are held together with fasteners. The detection of cracks under fasteners with ultrasonic techniques in subsurface layers away from the skin is impeded primarily by interlayer bonds and faying sealant condition. Further, assessment of such sealant condition is extremely challenging in terms of complexity of structure, limited access, and inspection cost. Although Eddy current techniques can be applied on in-service aircraft from the exterior of the skin without knowing sealant condition, the current eddy current techniques are not able to detect defects with wanted sensitivity. In this work a series of low frequency eddy current probes have been designed, fabricated and tested for this application. A probe design incorporating a shielded magnetic field sensor concentrically located in the interior of a drive coil has been employed to enable a localized deep diffusion of the electromagnetic field into the part under test. Due to the required low frequency inspections, probes have been testing using a variety of magnetic field sensors (pickup coil, giant magneto-resistive, anisotropic magneto-resistive, and spin-dependent tunneling). The probe designs as well as capabilities based upon a target inspection for sub-layer cracking in an airframe wing spar joint is presented.

  8. Development of Eddy Current Technique for the Detection of Stress Corrosion Cracking in Space Shuttle Primary Reaction Control Thrusters

    NASA Technical Reports Server (NTRS)

    Wincheski, Buzz; Simpson, John; Koshti, Ajay

    2006-01-01

    A recent identification of stress corrosion cracking in the Space Shuttle Primary Reaction Control System (PRCS) thrusters triggered an extensive nondestructive evaluation effort to develop techniques capable of identifying such damage on installed shuttle hardware. As a part of this effort, specially designed eddy current probes inserted into the acoustic cavity were explored for the detection of such flaws and for evaluation of the remaining material between the crack tip and acoustic cavity. The technique utilizes two orthogonal eddy current probes which are scanned under stepper motor control in the acoustic cavity to identify cracks hidden with as much as 0.060 remaining wall thickness to the cavity. As crack growth rates in this area have been determined to be very slow, such an inspection provides a large safety margin for continued operation of the critical shuttle hardware. Testing has been performed on thruster components with both actual and fabricated defects. This paper will review the design and performance of the developed eddy current inspection system. Detection of flaws as a function of remaining wall thickness will be presented along with the proposed system configuration for depot level or on-vehicle inspection capabilities.

  9. Development of Eddy Current Techniques for the Detection of Cracking in Space Shuttle Primary Reaction Control Thrusters

    NASA Technical Reports Server (NTRS)

    Wincheski, Buzz A.; Simpson, John W.; Koshti, Ajay

    2007-01-01

    A recent identification of cracking in the Space Shuttle Primary Reaction Control System (PRCS) thrusters triggered an extensive nondestructive evaluation effort to develop techniques capable of identifying such damage on installed shuttle hardware. As a part of this effort, specially designed eddy current probes inserted into the acoustic cavity were explored for the detection of such flaws and for evaluation of the remaining material between the crack tip and acoustic cavity. The technique utilizes two orthogonal eddy current probes which are scanned under stepper motor control in the acoustic cavity to identify cracks hidden with as much as 0.060 remaining wall thickness to the cavity. As crack growth rates in this area have been determined to be very slow, such an inspection provides a large safety margin for continued operation of the critical shuttle hardware. Testing has been performed on thruster components with both actual and fabricated defects. This paper will review the design and performance of the developed eddy current inspection system. Detection of flaws as a function of remaining wall thickness will be presented along with the proposed system configuration for depot level or on-vehicle inspection capabilities.

  10. Nitrous oxide emissions from a commercial cornfield (Zea mays) measured using the eddy-covariance technique

    NASA Astrophysics Data System (ADS)

    Huang, H.; Wang, J.; Hui, D.; Miller, D. R.; Bhattarai, S.; Dennis, S.; Smart, D.; Sammis, T.; Reddy, K. C.

    2014-08-01

    Increases in observed atmospheric concentrations of the long-lived greenhouse gas, nitrous oxide (N2O), have been well documented. However, information on event-related instantaneous emissions during fertilizer applications is lacking. With the development of fast-response N2O analyzers, the eddy covariance (EC) technique can be used to gather instantaneous measurements of N2O concentrations to quantify the exchange of nitrogen between the soil and atmosphere. The objectives of this study were to evaluate the performance of a new EC system, to measure the N2O flux with the system, and finally to examine relationships of the N2O flux with soil temperature, soil moisture, precipitation, and fertilization events. We assembled an EC system that included a sonic anemometer and a fast-response N2O analyzer (quantum cascade laser spectrometer) in a cornfield in Nolensville, Tennessee during the 2012 corn growing season (4 April-8 August). Fertilizer amounts totaling 217 kg N ha-1 were applied to the experimental site. The precision of the instrument was 0.066 ppbv for 10 Hz measurements. The seasonal mean detection limit of the N2O flux measurements was 2.10 ng N m-2 s-1. This EC system can be used to provide reliable N2O flux measurements. The cumulative emitted N2O for the entire growing season was 6.87 kg N2O-N ha-1. The 30 min average N2O emissions ranged from 0 to 11 100 μg N2O{-}N m-2 h-1 (mean = 257.5, standard deviation = 817.7). Average daytime emissions were much higher than night emissions (278.8 ± 865.8 vs. 100.0 ± 210.0 μg N2O-N m-2 h-1). Seasonal fluxes were highly dependent on soil moisture rather than soil temperature, although the diurnal flux was positively related to soil temperature. This study was one of the few experiments that continuously measured instantaneous, high-frequency N2O emissions in crop fields over a growing season of more than 100 days.

  11. New cyberinfrastructure for studying land-atmosphere interactions using eddy covariance techniques

    NASA Astrophysics Data System (ADS)

    Jaimes, A.; Salayandia, L.; Gallegos, I.; Gates, A. Q.; Tweedie, C.

    2010-12-01

    Eddy covariance (EC) methods are used to measure the exchanges of mass and energy across the atmospheric boundary layer. EC is the basis of several large national and international flux networks of micrometeorological tower sites (i.e. FLUXNET, AMERIFLUX), that provide continuous observations and measurements to understand and quantify the spatial and temporal variations in carbon storage in plants, soils, and the exchanges of carbon dioxide, water vapor, and energy, in major vegetation types across a range of disturbance historic and climatic conditions. A consistent quality assurance and quality control (QA/QC) procedure of micrometeorological data is essential for measurement networks such as these. Although, a QA/QC procedure is very much a site-specific activity, there are a variety of components available to implement Eddy covariance methods, as well as, limited documentation about best practices or standards, results in different approaches being adopted throughout data capturing sites. In some cases, this can lead to a limited or inefficient data reusability and knowledge transfer among related projects. The amount of data being collected is rapidly increasing, and the ability to evaluate proper instrument operation and data accuracy is critical to ensure the results are not bias due to factors such as, instrument malfunction, erroneous definition of optimal measurement ranges, calibration errors and differences, and environmental conditions that can affect data quality (i.e. wind directions are not from the footprint of interest, heavy precipitation, dust/snow storms, etc). This study presents findings from Cyberinfrastructure research conducted on a data stream from a newly established Eddy Covariance Tower, located on the Jornada basin Experimental Range (JER), Las Cruces, NM. Specifically, property characterization and specification was developed under a series of laboratory and field experiments. Our intent was to characterize thresholds and range

  12. Grafting: A Technique to Modify Ion Accumulation in Horticultural Crops

    PubMed Central

    Nawaz, Muhammad A.; Imtiaz, Muhammad; Kong, Qiusheng; Cheng, Fei; Ahmed, Waqar; Huang, Yuan; Bie, Zhilong

    2016-01-01

    Grafting is a centuries-old technique used in plants to obtain economic benefits. Grafting increases nutrient uptake and utilization efficiency in a number of plant species, including fruits, vegetables, and ornamentals. Selected rootstocks of the same species or close relatives are utilized in grafting. Rootstocks absorb more water and ions than self-rooted plants and transport these water and ions to the aboveground scion. Ion uptake is regulated by a complex communication mechanism between the scion and rootstock. Sugars, hormones, and miRNAs function as long-distance signaling molecules and regulate ion uptake and ion homeostasis by affecting the activity of ion transporters. This review summarizes available information on the effect of rootstock on nutrient uptake and utilization and the mechanisms involved. Information on specific nutrient-efficient rootstocks for different crops of commercial importance is also provided. Several other important approaches, such as interstocking (during double grafting), inarching, use of plant-growth-promoting rhizobacteria, use of arbuscular mycorrhizal fungi, use of plant growth substances (e.g., auxin and melatonin), and use of genetically engineered rootstocks and scions (transgrafting), are highlighted; these approaches can be combined with grafting to enhance nutrient uptake and utilization in commercially important plant species. Whether the rootstock and scion affect each other's soil microbiota and their effect on the nutrient absorption of rootstocks remain largely unknown. Similarly, the physiological and molecular bases of grafting, crease formation, and incompatibility are not fully identified and require investigation. Grafting in horticultural crops can help reveal the basic biology of grafting, the reasons for incompatibility, sensing, and signaling of nutrients, ion uptake and transport, and the mechanism of heavy metal accumulation and restriction in rootstocks. Ion transporter and miRNA-regulated nutrient

  13. Water Velocity as a Driver of Stream Metabolism: a Parallel Application of the Open Water and Eddy Correlation Techniques

    NASA Astrophysics Data System (ADS)

    Koopmans, D.; Berg, P.

    2013-12-01

    Inland waters respire or store a large portion of net terrestrial ecosystem production. As a result their metabolism is significant to the global carbon budget. The proximal drivers of aquatic respiration are organic matter availability, temperature, nutrients, and water velocity. Among these water velocity may be the least quantified. A partial explanation is that the footprint of the open water technique is typically hundreds of meters of river length, while the effect of a change in velocity may be specific to a local benthic environment, e.g., a riffle. With the eddy correlation technique oxygen flux is calculated from the turbulent fluctuation of vertical velocity and the oxygen concentration at a point in the water column. The footprint of the technique scales with the height of the point of measurement allowing an investigation of the in situ oxygen flux at the scale of a riffle. The combination of techniques, then, can be used to investigate the coupling of hydrodynamic conditions and benthic environments in driving aquatic ecosystem metabolism. This parallel approach was applied seasonally to examine the drivers of metabolism in a nutrient-rich, sand-bed coastal stream on the Eastern Shore of Virginia. An ecosystem-scale oxygen flux was calculated with the open water technique while pool-, run-, riffle-, and freshwater tidal-scale oxygen fluxes were calculated with the eddy correlation technique. At the ecosystem scale the stream bed functioned as an effective biocatalytic filter with an average annual net oxygen consumption of 300 mmol m^-2 d^-1. Prior to a stage-discharge shift water velocity explained 90% of the variance in ecosystem respiration (n = 63 days). After the stage-discharge shift water velocity explained 96 % of it (n = 40 days). Hyporheic exchange supported respiration in this system, contributing to its close correlation with water velocity. Among the physically similar benthic environments of the run, riffle, and freshwater tidal sites

  14. Combined investigation of Eddy current and ultrasonic techniques for composite materials NDE

    NASA Technical Reports Server (NTRS)

    Davis, C. W.; Nath, S.; Fulton, J. P.; Namkung, M.

    1993-01-01

    Advanced composites are not without trade-offs. Their increased designability brings an increase in the complexity of their internal geometry and, as a result, an increase in the number of failure modes associated with a defect. When two or more isotropic materials are combined in a composite, the isotropic material failure modes may also combine. In a laminate, matrix delamination, cracking and crazing, and voids and porosity, will often combine with fiber breakage, shattering, waviness, and separation to bring about ultimate structural failure. This combining of failure modes can result in defect boundaries of different sizes, corresponding to the failure of each structural component. This paper discusses a dual-technology NDE (Non Destructive Evaluation) (eddy current (EC) and ultrasonics (UT)) study of graphite/epoxy (gr/ep) laminate samples. Eddy current and ultrasonic raster (Cscan) imaging were used together to characterize the effects of mechanical impact damage, high temperature thermal damage and various types of inserts in gr/ep laminate samples of various stacking sequences.

  15. Nonlinear, non-stationary image processing technique for eddy current NDE

    NASA Astrophysics Data System (ADS)

    Yang, Guang; Dib, Gerges; Kim, Jaejoon; Zhang, Lu; Xin, Junjun; Udpa, Lalita

    2012-05-01

    Automatic analysis of eddy current (EC) data has facilitated the analysis of large volumes of data generated in the inspection of steam generator tubes in nuclear power plants. The traditional procedure for analysis of EC data includes data calibration, pre-processing, region of interest (ROI) detection, feature extraction and classification. Accurate ROI detection has been enhanced by pre-processing, which involves reducing noise and other undesirable components as well as enhancing defect indications in the raw measurement. This paper presents the Hilbert-Huang Transform (HHT) for feature extraction and support vector machine (SVM) for classification. The performance is shown to significantly better than the existing rule based classification approach used in industry.

  16. Frequency Optimization for Enhancement of Surface Defect Classification Using the Eddy Current Technique

    PubMed Central

    Fan, Mengbao; Wang, Qi; Cao, Binghua; Ye, Bo; Sunny, Ali Imam; Tian, Guiyun

    2016-01-01

    Eddy current testing is quite a popular non-contact and cost-effective method for nondestructive evaluation of product quality and structural integrity. Excitation frequency is one of the key performance factors for defect characterization. In the literature, there are many interesting papers dealing with wide spectral content and optimal frequency in terms of detection sensitivity. However, research activity on frequency optimization with respect to characterization performances is lacking. In this paper, an investigation into optimum excitation frequency has been conducted to enhance surface defect classification performance. The influences of excitation frequency for a group of defects were revealed in terms of detection sensitivity, contrast between defect features, and classification accuracy using kernel principal component analysis (KPCA) and a support vector machine (SVM). It is observed that probe signals are the most sensitive on the whole for a group of defects when excitation frequency is set near the frequency at which maximum probe signals are retrieved for the largest defect. After the use of KPCA, the margins between the defect features are optimum from the perspective of the SVM, which adopts optimal hyperplanes for structure risk minimization. As a result, the best classification accuracy is obtained. The main contribution is that the influences of excitation frequency on defect characterization are interpreted, and experiment-based procedures are proposed to determine the optimal excitation frequency for a group of defects rather than a single defect with respect to optimal characterization performances. PMID:27164112

  17. Evaluation of laser absorption spectroscopic techniques for eddy covariance flux measurements of ammonia.

    PubMed

    Whitehead, James D; Twigg, Marsailidh; Famulari, Daniela; Nemitz, Eiko; Sutton, Mark A; Gallagher, Martin W; Fowler, David

    2008-03-15

    An intercomparison was made between eddy covariance flux measurements of ammonia by a quantum cascade laser absorption spectrometer (QCLAS) and a lead-salt tunable diode laser absorption spectrometer (TDLAS). The measurements took place in September 2004 and again in April 2005 over a managed grassland site in Southern Scotland, U.K. These were also compared with a flux estimate derived from an "Ammonia Measurement by ANnular Denuder with online Analysis" (AMANDA), using the aerodynamic gradient method (AGM). The concentration and flux measurements from the QCLAS correlated well with those of the TDLAS and the AGM systems when emissions were high, following slurry application to the field. Both the QCLAS and TDLAS, however, underestimated the flux when compared with the AMANDA system, by 64%. A flux loss of 41% due to chemical reaction of ammonia in the QCLAS (and 37% in the TDLAS) sample tube walls was identified and characterized using laboratory tests but did not fully accountforthis difference. Recognizing these uncertainties, the agreement between the systems was nevertheless very close (R2 = 0.95 between the QCLAS and the TDLAS; R2 = 0.84 between the QCLAS and the AMANDA) demonstrating the suitability of the laser absorption methods for quantifying the temporal dynamics of ammonia fluxes.

  18. Frequency Optimization for Enhancement of Surface Defect Classification Using the Eddy Current Technique.

    PubMed

    Fan, Mengbao; Wang, Qi; Cao, Binghua; Ye, Bo; Sunny, Ali Imam; Tian, Guiyun

    2016-05-07

    Eddy current testing is quite a popular non-contact and cost-effective method for nondestructive evaluation of product quality and structural integrity. Excitation frequency is one of the key performance factors for defect characterization. In the literature, there are many interesting papers dealing with wide spectral content and optimal frequency in terms of detection sensitivity. However, research activity on frequency optimization with respect to characterization performances is lacking. In this paper, an investigation into optimum excitation frequency has been conducted to enhance surface defect classification performance. The influences of excitation frequency for a group of defects were revealed in terms of detection sensitivity, contrast between defect features, and classification accuracy using kernel principal component analysis (KPCA) and a support vector machine (SVM). It is observed that probe signals are the most sensitive on the whole for a group of defects when excitation frequency is set near the frequency at which maximum probe signals are retrieved for the largest defect. After the use of KPCA, the margins between the defect features are optimum from the perspective of the SVM, which adopts optimal hyperplanes for structure risk minimization. As a result, the best classification accuracy is obtained. The main contribution is that the influences of excitation frequency on defect characterization are interpreted, and experiment-based procedures are proposed to determine the optimal excitation frequency for a group of defects rather than a single defect with respect to optimal characterization performances.

  19. Frequency Optimization for Enhancement of Surface Defect Classification Using the Eddy Current Technique.

    PubMed

    Fan, Mengbao; Wang, Qi; Cao, Binghua; Ye, Bo; Sunny, Ali Imam; Tian, Guiyun

    2016-01-01

    Eddy current testing is quite a popular non-contact and cost-effective method for nondestructive evaluation of product quality and structural integrity. Excitation frequency is one of the key performance factors for defect characterization. In the literature, there are many interesting papers dealing with wide spectral content and optimal frequency in terms of detection sensitivity. However, research activity on frequency optimization with respect to characterization performances is lacking. In this paper, an investigation into optimum excitation frequency has been conducted to enhance surface defect classification performance. The influences of excitation frequency for a group of defects were revealed in terms of detection sensitivity, contrast between defect features, and classification accuracy using kernel principal component analysis (KPCA) and a support vector machine (SVM). It is observed that probe signals are the most sensitive on the whole for a group of defects when excitation frequency is set near the frequency at which maximum probe signals are retrieved for the largest defect. After the use of KPCA, the margins between the defect features are optimum from the perspective of the SVM, which adopts optimal hyperplanes for structure risk minimization. As a result, the best classification accuracy is obtained. The main contribution is that the influences of excitation frequency on defect characterization are interpreted, and experiment-based procedures are proposed to determine the optimal excitation frequency for a group of defects rather than a single defect with respect to optimal characterization performances. PMID:27164112

  20. A Model of Turbulence, Sediment Transport and Morphodynamics of Lateral Separation Zones in Canyon Rivers using Detached Eddy Simulation Technique

    NASA Astrophysics Data System (ADS)

    Alvarez, L. V.; Schmeeckle, M. W.; Grams, P. E.; Moreno, H. A.

    2015-12-01

    Lateral separation zones are featured by large-scale flow separation, secondary recirculation zones and free shear layers. In the Colorado River, lateral separation zones are the principal source of fine sediment for eddy sandbars. A parallelized, three-dimensional turbulence-resolving model is coupled with a continuum sediment transport model and tested in lateral separation zones located in two pools along the Colorado River in Marble Canyon. The model aims to study the flow and sediment dynamics of lateral separation zones, recognizing the important role that these processes play in the erosion, deposition and morphodynamics of eddy sandbars. The Detached Eddy Simulation (DES) technique is employed for fully resolved turbulence at larger scales than the Sub-Grid-Scale (SGS) while SGS turbulence is modeled using the Spalart-Allmaras one equation turbulence closure model. This DES-3D flow model is coupled to a sediment advection-diffusion formulation, wherein advection is provided by the DES velocity field minus particles settling velocity, and diffusion is provided by the SGS. The Smith and McLean suspended sediment boundary condition is used to calculate the upward and downward settling of sediment fluxes in the near-bed grid cells. Five groups of sediment sizes are employed and estimated using a mixing layer model. Each fraction of the grain size group is redistributed every time step. Thus, the model is able to predict the exposure and burial of bedrock by fine grain size sediment. The simulated results show a pattern of unsteady pulsations in the exchange of concentration of sediment and deposition fluxes between the primary zone and the main channel. This exchange occurs at the convergence and divergence zones. These pulsations are more accentuated at the convergence zone, but still evidenced at the divergence zone. Along the simulated river-reach, the concentration values increase in the constrictions and decrease in the main channel. At both rapids, net

  1. Chambers versus Relaxed Eddy Accumulation: an intercomparison study of two methods for short-term measurements of biogenic CO2 fluxes

    NASA Astrophysics Data System (ADS)

    Jasek, Alina; Zimnoch, Miroslaw; Gorczyca, Zbigniew; Chmura, Lukasz; Necki, Jaroslaw

    2014-05-01

    The presented work is a part of comprehensive study aimed at thorough characterization of carbon cycle in the urban environment of Krakow, southern Poland. In the framework of this study two independent methods were employed to quantify biogenic CO2 flux in the city: (i) closed chambers, and (ii) Relaxed Eddy Accumulation (REA). The results of a three-day intensive intercomparison campaign performed in July 2013 and utilizing both measurement methods are reported here. The chamber method is a widely used approach for measurements of gas exchange between the soil and the atmosphere. The system implemented in this study consisted of a single chamber operating in a closed-dynamic mode, combined with Vaisala CarboCAP infrared CO2 sensor in a mobile setup. An alternative flux measurement method, covering larger area is represented by REA, which is a modification of the eddy covariance method. It consists of a 3D anemometer (Gill Windmaster Pro) and the system collecting updraft and downdraft samples to 5-litre Tedlar bags. The CO2 mixing ratios in the collected samples are measured by Picarro G2101i analyzer. The setup consists of two sets of bags so that the sampling can be performed continuously with 15-min temporal resolution. A 48-hectares open meadow located close the city center was chosen as a test site for comparison of the two methods of CO2 flux measurements outlined above. In the middle of the meadow a 3-metre high tripod was installed with the anemometer and REA inlet system. For a period of 46 hours the system was measuring net CO2 flux from the surrounding area. A meteorological conditions and intensity of photosynthetically active radiation (PAR) were also recorded. In the same time, CO2 flux from several points around the REA inlet was measured with the chamber system, resulting in 93 values for both respiration and net CO2 flux. Chamber results show rather homogenous distribution of the soil CO2 flux (the mean value equal to 40.9 ± 2.2 mmol/m2h), with

  2. Turbulent fluxes by "Conditional Eddy Sampling"

    NASA Astrophysics Data System (ADS)

    Siebicke, Lukas

    2015-04-01

    for the field (one to two orders of magnitude lower compared to current closed-path laser based eddy covariance systems). Potential applications include fluxes of CO2, CH4, N2O, VOCs and other tracers. Finally we assess the flux accuracy of the Conditional Eddy Sampling (CES) approach as in our real implementation relative to alternative techniques including eddy covariance (EC) and relaxed eddy accumulation (REA). We further quantify various sources of instrument and method specific measurement errors. This comparison uses real measurements of 20 Hz turbulent time series of 3D wind velocity, sonic temperature and CO2 mixing ratio over a mixed decidious forest at the 'ICOS' flux tower site 'Hainich', Germany. Results from a simulation using real wind and CO2 timeseries from the Hainich site from 30 April to 3 November 2014 and real instrument performance suggest that the maximum flux estimates error (50% and 75% error quantiles) from Conditional Eddy Sampling (CES) relative to the true flux is 1.3% and 10%, respectively for monthly net fluxes, 1.6% and 7%, respectively for daily net fluxes and 8% and 35%, respectively for 30-minute CO2 flux estimates. Those results from CES are promising and outperform our REA estimates by about a factor of 50 assuming REA with constant b value. Results include flux time series from the EC, CES and REA approaches from 30-min to annual resolution.

  3. Accumulated damage process of thermal sprayed coating under rolling contact by acoustic emission technique

    NASA Astrophysics Data System (ADS)

    Xu, Jia; Zhou, Zhen-yu; Piao, Zhong-yu

    2016-09-01

    The accumulated damage process of rolling contact fatigue (RCF) of plasma-sprayed coatings was investigated. The influences of surface roughness, loading condition, and stress cycle frequency on the accumulated damage status of the coatings were discussed. A ball-ondisc machine was employed to conduct RCF experiments. Acoustic emission (AE) technique was introduced to monitor the RCF process of the coatings. AE signal characteristics were investigated to reveal the accumulated damage process. Result showed that the polished coating would resist the asperity contact and remit accumulated damage. The RCF lifetime would then extend. Heavy load would aggravate the accumulated damage status and induce surface fracture. Wear became the main failure mode that reduced the RCF lifetime. Frequent stress cycle would aggravate the accumulated damage status and induce interface fracture. Fatigue then became the main failure mode that also reduced the RCF lifetime.

  4. Accumulated damage process of thermal sprayed coating under rolling contact by acoustic emission technique

    NASA Astrophysics Data System (ADS)

    Xu, Jia; Zhou, Zhen-yu; Piao, Zhong-yu

    2016-07-01

    The accumulated damage process of rolling contact fatigue (RCF) of plasma-sprayed coatings was investigated. The influences of surface roughness, loading condition, and stress cycle frequency on the accumulated damage status of the coatings were discussed. A ball-ondisc machine was employed to conduct RCF experiments. Acoustic emission (AE) technique was introduced to monitor the RCF process of the coatings. AE signal characteristics were investigated to reveal the accumulated damage process. Result showed that the polished coating would resist the asperity contact and remit accumulated damage. The RCF lifetime would then extend. Heavy load would aggravate the accumulated damage status and induce surface fracture. Wear became the main failure mode that reduced the RCF lifetime. Frequent stress cycle would aggravate the accumulated damage status and induce interface fracture. Fatigue then became the main failure mode that also reduced the RCF lifetime.

  5. Component greenhouse gas fluxes and radiative balance from two deltaic marshes in Louisiana: Pairing chamber techniques and eddy covariance

    NASA Astrophysics Data System (ADS)

    Krauss, Ken W.; Holm, Guerry O.; Perez, Brian C.; McWhorter, David E.; Cormier, Nicole; Moss, Rebecca F.; Johnson, Darren J.; Neubauer, Scott C.; Raynie, Richard C.

    2016-06-01

    Coastal marshes take up atmospheric CO2 while emitting CO2, CH4, and N2O. This ability to sequester carbon (C) is much greater for wetlands on a per area basis than from most ecosystems, facilitating scientific, political, and economic interest in their value as greenhouse gas sinks. However, the greenhouse gas balance of Gulf of Mexico wetlands is particularly understudied. We describe the net ecosystem exchange (NEEc) of CO2 and CH4 using eddy covariance (EC) in comparison with fluxes of CO2, CH4, and N2O using chambers from brackish and freshwater marshes in Louisiana, USA. From EC, we found that 182 g C m-2 yr-1 was lost through NEEc from the brackish marsh. Of this, 11 g C m-2 yr-1 resulted from net CH4 emissions and the remaining 171 g C m-2 yr-1 resulted from net CO2 emissions. In contrast, -290 g C m2 yr-1 was taken up through NEEc by the freshwater marsh, with 47 g C m-2 yr-1 emitted as CH4 and -337 g C m-2 yr-1 taken up as CO2. From chambers, we discovered that neither site had large fluxes of N2O. Sustained-flux greenhouse gas accounting metrics indicated that both marshes had a positive (warming) radiative balance, with the brackish marsh having a substantially greater warming effect than the freshwater marsh. That net respiratory emissions of CO2 and CH4 as estimated through chamber techniques were 2-4 times different from emissions estimated through EC requires additional understanding of the artifacts created by different spatial and temporal sampling footprints between techniques.

  6. Development of Quality Assessment Techniques for Large Eddy Simulation of Propulsion and Power Systems in Complex Geometries

    SciTech Connect

    Lacaze, Guilhem; Oefelein, Joseph

    2015-03-01

    Large-eddy-simulation (LES) is quickly becoming a method of choice for studying complex thermo-physics in a wide range of propulsion and power systems. It provides a means to study coupled turbulent combustion and flow processes in parameter spaces that are unattainable using direct-numerical-simulation (DNS), with a degree of fidelity that can be far more accurate than conventional engineering methods such as the Reynolds-averaged Navier-Stokes (RANS) approx- imation. However, development of predictive LES is complicated by the complex interdependence of different type of errors coming from numerical methods, algorithms, models and boundary con- ditions. On the other hand, control of accuracy has become a critical aspect in the development of predictive LES for design. The objective of this project is to create a framework of metrics aimed at quantifying the quality and accuracy of state-of-the-art LES in a manner that addresses the myriad of competing interdependencies. In a typical simulation cycle, only 20% of the computational time is actually usable. The rest is spent in case preparation, assessment, and validation, because of the lack of guidelines. This work increases confidence in the accuracy of a given solution while min- imizing the time obtaining the solution. The approach facilitates control of the tradeoffs between cost, accuracy, and uncertainties as a function of fidelity and methods employed. The analysis is coupled with advanced Uncertainty Quantification techniques employed to estimate confidence in model predictions and calibrate model's parameters. This work has provided positive conse- quences on the accuracy of the results delivered by LES and will soon have a broad impact on research supported both by the DOE and elsewhere.

  7. Application of Self Nulling Eddy Current Probe Technique to the Detection of Fatigue Crack Initiation and Control of Test Procedures

    NASA Technical Reports Server (NTRS)

    Namkung, M.; Nath, S.; Wincheski, B.; Fulton, J. P.

    1994-01-01

    A major part of fracture mechanics is concerned with studying the initiation and propagation of fatigue cracks. This typically requires constant monitoring of crack growth during fatigue cycles and the knowledge of the precise location of the crack tip at any given time. One technique currently available for measuring fatigue crack length is the Potential Drop method. The method, however, may be inaccurate if the direction of crack growth deviates considerably from what was assumed initially or the curvature of the crack becomes significant. Another popular approach is to optically view the crack using a high magnification microscope, but this entails a person constantly monitoring it. The present proposed technique uses an automated scheme, in order to eliminate the need for a person to constantly monitor the experiment. Another technique under development elsewhere is to digitize an optical image of the test specimen surface and then apply a pattern recognition algorithm to locate the crack tip. A previous publication showed that the self nulling eddy current probe successfully tracked a simulated crack in an aluminum sample. This was the impetus to develop an online real time crack monitoring system. An automated system has been developed which includes a two axis scanner mounted on the tensile testing machine, the probe and its instrumentation and a personal computer (PC) to communicate and control all the parameters. The system software controls the testing parameters as well as monitoring the fatigue crack as it propagates. This paper will discuss the experimental setup in detail and demonstrate its capabilities. A three dimensional finite element model is utilized to model the magnetic field distribution due to the probe and how the probe voltage changes as it scans the crack. Experimental data of the probe for different samples under zero load, static load and high cycle fatigue load will be discussed. The final section summarizes the major accomplishments

  8. Component greenhouse gas fluxes and radiative balance from two deltaic marshes in Louisiana: Pairing chamber techniques and eddy covariance

    USGS Publications Warehouse

    Krauss, Ken W.; Holm, Guerry O.; Perez, Brian C.; McWhorter, David E.; Cormier, Nicole; Moss, Rebecca; Johnson, Darren; Neubauer, Scott C; Raynie, Richard C

    2016-01-01

    Coastal marshes take up atmospheric CO2 while emitting CO2, CH4, and N2O. This ability to sequester carbon (C) is much greater for wetlands on a per-area basis than from most ecosystems, facilitating scientific, political, and economic interest in their value as greenhouse gas sinks. However, the greenhouse gas balance of Gulf of Mexico wetlands is particularly understudied. We describe the net ecosystem exchange (NEEc) of CO2 and CH4 using eddy covariance (EC) in comparison with fluxes of CO2, CH4, and N2O using chambers from brackish and freshwater marshes in Louisiana, USA. From EC, we found that 182 g C m-2 y-1 was lost through NEEc from the brackish marsh. Of this, 11 g C m-2 y-1 resulted from net CH4 emissions and the remaining 171 g C m-2 y-1 resulted from net CO2 emissions. In contrast, -290 g C m2 y-1 was taken up through NEEc by the freshwater marsh, with 47 g C m-2 y-1 emitted as CH4 and -337 g C m-2 y-1 taken up as CO2. From chambers, we discovered that neither site had large fluxes of N2O. Sustained-flux greenhouse gas accounting metrics indicated that both marshes had a positive (warming) radiative balance, with the brackish marsh having a substantially greater warming effect than the freshwater marsh. That net respiratory emissions of CO2 and CH4 as estimated through chamber techniques were 2-4 times different from emissions estimated through EC requires additional understanding of the artifacts created by different spatial and temporal sampling footprints between techniques.

  9. Study of eddy current probes

    NASA Technical Reports Server (NTRS)

    Workman, Gary L.; Wang, Morgan

    1992-01-01

    The recognition of materials properties still presents a number of problems for nondestructive testing in aerospace systems. This project attempts to utilize current capabilities in eddy current instrumentation, artificial intelligence, and robotics in order to provide insight into defining geometrical aspects of flaws in composite materials which are capable of being evaluated using eddy current inspection techniques.

  10. Application of Relaxed Eddy Accumulation (REA) method to estimate CO2 and CH4 surface fluxes in the city of Krakow, southern Poland.

    NASA Astrophysics Data System (ADS)

    Zimnoch, Miroslaw; Gorczyca, Zbigniew; Pieniazek, Katarzyna; Jasek, Alina; Chmura, Lukasz; Rozanski, Kazimierz

    2013-04-01

    There is a growing interest in the recent years in studies aimed at quantifying carbon cycling in urban centres. Worldwide migration of human population from rural to urban areas and corresponding growth of extensive urban agglomerations and megacities leads to intensification of anthropogenic emissions of carbon and strong disruption of natural carbon cycle on these areas. Therefore, a deeper understanding of the carbon "metabolism" of such regions is required. Apart of better quantification of surface carbon fluxes, also a thorough understanding of the functioning of biosphere under strong anthropogenic influence is needed. Nowadays, covariance methods are widely applied for studying gas exchange between the atmosphere and the Earth's surface. Relaxed Eddy Accumulation method (REA), combined with the CO2 and CH4 CRDS analyser allows simultaneous measurements of surface fluxes of carbon dioxide and methane within the chosen footprint of the detection system, thus making possible thorough characterisation of the overall exchange of those gases between the atmosphere and the urban surface across diverse spatial and temporal scales. Here we present preliminary results of the study aimed at quantifying surface fluxes of CO2 and CH4 in Krakow, southern Poland. The REA system for CO2 and CH4 flux measurements has been installed on top of a 20m high tower mounted on the roof of the faculty building, close to the city centre of Krakow. The sensors were installed ca 42 m above the local ground. Gill Windmaster-Pro sonic anemometer was coupled with self-made system, designed by the Poznan University of Life Sciences, Poland, for collecting air samples in two pairs of 10-liter Tedlar bags, and with Picarro G2101-i CRDS analyser. The air was collected in 30-min intervals. The CO2 and CH4 mixing ratios in these cumulative downdraft and updraft air samples were determined by the CRDS analyser after each sampling interval. Based on the measured mixing ratios difference and the

  11. Geohydrology and evapotranspiration at Franklin Lake playa, Inyo County, California; with a section on estimating evapotranspiration using the energy-budget eddy-correlation technique

    USGS Publications Warehouse

    Czarnecki, John B.; Stannard, David I.

    1997-01-01

    Franklin Lake playa is one of the principal discharge areas of the ground-water-flow system associated with Yucca Mountain, Nevada, the potential site of a high-level nuclear-waste repository. By using the energy-budget eddy-correlation technique, measurements made between June 1983 and April 1984 to estimate evapotranspiration were found to range from 0.1 centimeter per day during winter months to about 0.3 centimeter per day during summer months; the annual average was 0.16 centimeter per day. These estimates were compared with evapotranspiration estimates calculated from six other methods.

  12. Characterisation of Phosphate Accumulating Organisms and Techniques for Polyphosphate Detection: A Review

    PubMed Central

    Tarayre, Cédric; Nguyen, Huu-Thanh; Brognaux, Alison; Delepierre, Anissa; De Clercq, Lies; Charlier, Raphaëlle; Michels, Evi; Meers, Erik; Delvigne, Frank

    2016-01-01

    Phosphate minerals have long been used for the production of phosphorus-based chemicals used in many economic sectors. However, these resources are not renewable and the natural phosphate stocks are decreasing. In this context, the research of new phosphate sources has become necessary. Many types of wastes contain non-negligible phosphate concentrations, such as wastewater. In wastewater treatment plants, phosphorus is eliminated by physicochemical and/or biological techniques. In this latter case, a specific microbiota, phosphate accumulating organisms (PAOs), accumulates phosphate as polyphosphate. This molecule can be considered as an alternative phosphate source, and is directly extracted from wastewater generated by human activities. This review focuses on the techniques which can be applied to enrich and try to isolate these PAOs, and to detect the presence of polyphosphate in microbial cells. PMID:27258275

  13. Characterisation of Phosphate Accumulating Organisms and Techniques for Polyphosphate Detection: A Review.

    PubMed

    Tarayre, Cédric; Nguyen, Huu-Thanh; Brognaux, Alison; Delepierre, Anissa; De Clercq, Lies; Charlier, Raphaëlle; Michels, Evi; Meers, Erik; Delvigne, Frank

    2016-01-01

    Phosphate minerals have long been used for the production of phosphorus-based chemicals used in many economic sectors. However, these resources are not renewable and the natural phosphate stocks are decreasing. In this context, the research of new phosphate sources has become necessary. Many types of wastes contain non-negligible phosphate concentrations, such as wastewater. In wastewater treatment plants, phosphorus is eliminated by physicochemical and/or biological techniques. In this latter case, a specific microbiota, phosphate accumulating organisms (PAOs), accumulates phosphate as polyphosphate. This molecule can be considered as an alternative phosphate source, and is directly extracted from wastewater generated by human activities. This review focuses on the techniques which can be applied to enrich and try to isolate these PAOs, and to detect the presence of polyphosphate in microbial cells. PMID:27258275

  14. Characterisation of Phosphate Accumulating Organisms and Techniques for Polyphosphate Detection: A Review.

    PubMed

    Tarayre, Cédric; Nguyen, Huu-Thanh; Brognaux, Alison; Delepierre, Anissa; De Clercq, Lies; Charlier, Raphaëlle; Michels, Evi; Meers, Erik; Delvigne, Frank

    2016-01-01

    Phosphate minerals have long been used for the production of phosphorus-based chemicals used in many economic sectors. However, these resources are not renewable and the natural phosphate stocks are decreasing. In this context, the research of new phosphate sources has become necessary. Many types of wastes contain non-negligible phosphate concentrations, such as wastewater. In wastewater treatment plants, phosphorus is eliminated by physicochemical and/or biological techniques. In this latter case, a specific microbiota, phosphate accumulating organisms (PAOs), accumulates phosphate as polyphosphate. This molecule can be considered as an alternative phosphate source, and is directly extracted from wastewater generated by human activities. This review focuses on the techniques which can be applied to enrich and try to isolate these PAOs, and to detect the presence of polyphosphate in microbial cells.

  15. Evaluation of the Advanced-Canopy-Atmosphere-Surface Algorithm (ACASA Model) Using Eddy Covariance Technique Over Sparse Canopy

    NASA Astrophysics Data System (ADS)

    Marras, S.; Spano, D.; Sirca, C.; Duce, P.; Snyder, R.; Pyles, R. D.; Paw U, K. T.

    2008-12-01

    Land surface models are usually used to quantify energy and mass fluxes between terrestrial ecosystems and atmosphere on micro- and regional scales. One of the most elaborate land surface models for flux modelling is the Advanced Canopy-Atmosphere-Soil Algorithm (ACASA) model, which provides micro-scale as well as regional-scale fluxes when imbedded in a meso-scale meteorological model (e.g., MM5 or WRF). The model predicts vegetation conditions and changes with time due to plant responses to environment variables. In particular, fluxes and profiles of heat, water vapor, carbon and momentum within and above canopy are estimated using third-order equations. It also estimates turbulent profiles of velocity, temperature, humidity within and above canopy, and CO2 fluxes are estimated using a combination of Ball-Berry and Farquhar equations. The ACASA model is also able to include the effects of water stress on stomata, transpiration and CO2 assimilation. ACASA model is unique because it separates canopy domain into twenty atmospheric layers (ten layers within the canopy and ten layers above the canopy), and the soil is partitioned into fifteen layers of variable thickness. The model was mainly used over dense canopies in the past, so the aim of this work was to test the ACASA model over a sparse canopy as Mediterranean maquis. Vegetation is composed by sclerophyllous species of shrubs that are always green, with leathery leaves, small height, with a moderately sparse canopy, and that are tolerant at water stress condition. Eddy Covariance (EC) technique was used to collect continuous data for more than 3 years period. Field measurements were taken in a natural maquis site located near Alghero, Sardinia, Italy and they were used to parameterize and validate the model. The input values were selected by running the model several times varying the one parameter per time. A second step in the parameterization process was the simultaneously variation of some parameters

  16. Energy budget measurements using eddy correlation and Bowen ratio techniques at the Kinosheo Lake tower site during the Northern Wetlands Study

    NASA Technical Reports Server (NTRS)

    Den Hartog, G.; Neumann, H. H.; King, K. M.; Chipanshi, A. C.

    1994-01-01

    Fluxes of heat and water vapor were measured on a 20-m tower at Kinosheo Lake in the Hudson Bay lowlands using eddy correlation and Bowen ratio energy balance techniques. The study period was June 25 to July 28, 1990. Measurements were made over a peat bog consisting of a mixture of sphagnum moss and lichen hummocks and black pools. About 200 m west of the tower were several shallow ponds. The hummocks had a dry, insulating surface and were underlain by an ice layer near 50 cm depth until mid-July. At the beginning of the period the black pools were covered with water, and although the free water gradually disappeared over the study period, they remained saturated to the end of July. The depth of peat near the tower was about 3 m. Despite the ice layer under the hummocks, their daytime surface temperatures were high, near 35 C, and after the middle of July, above 40 C. Inspection of temperature, precipitation, and radiation data showed that the midsummer period of 1990 was warmer, drier, and sunnier than usual at Moosonee and so by influence at Lake Kinosheo. When all the data were combined to yield average diurnal energy balance components, the eddy correlation fluxes accounted for 90% of the available energy. Latent heat flux averaged 46% of the total available energy and the sensible heat flux averaged 34%. Daytime Bowen ratios were near 1 for the experimental period, suggesting that the bog behaved more like a dryland than a wetland. Eddy correlation measurements of sensible heat and latent heat flux were less than those measured using the Bowen ratio energy balance technique, the average ratios being 0.81 and 0.86 respectively. These differences were possibly due to the difficulty in measuring energy balance components of net radiation and ground heat flux over the mosaic surface.

  17. On the estimate of the transpiration in Mediterranean heterogeneous ecosystems with the coupled use of eddy covariance and sap flow techniques.

    NASA Astrophysics Data System (ADS)

    Corona, Roberto; Curreli, Matteo; Montaldo, Nicola; Oren, Ram

    2013-04-01

    Mediterranean ecosystems are commonly heterogeneous savanna-like ecosystems, with contrasting plant functional types (PFT) competing for the water use. Mediterranean regions suffer water scarcity due to the dry climate conditions. In semi-arid regions evapotranspiration (ET) is the leading loss term of the root-zone water budget with a yearly magnitude that may be roughly equal to the precipitation. Despite the attention these ecosystems are receiving, a general lack of knowledge persists about the estimate of ET and the relationship between ET and the plant survival strategies for the different PFTs under water stress. During the dry summers these water-limited heterogeneous ecosystems are mainly characterized by a simple dual PFT-landscapes with strong-resistant woody vegetation and bare soil since grass died. In these conditions due to the low signal of the land surface fluxes captured by the sonic anemometer and gas analyzer the widely used eddy covariance may fail and its ET estimate is not robust enough. In these conditions the use of the sap flow technique may have a key role, because theoretically it provides a direct estimate of the woody vegetation transpiration. Through the coupled use of the sap flow sensor observations, a 2D foot print model of the eddy covariance tower and high resolution satellite images for the estimate of the foot print land cover map, the eddy covariance measurements can be correctly interpreted, and ET components (bare soil evaporation and woody vegetation transpiration) can be separated. The case study is at the Orroli site in Sardinia (Italy). The site landscape is a mixture of Mediterranean patchy vegetation types: trees, including wild olives and cork oaks, different shrubs and herbaceous species. An extensive field campaign started in 2004. Land-surface fluxes and CO2 fluxes are estimated by an eddy covariance technique based micrometeorological tower. Soil moisture profiles were also continuously estimated using water

  18. A comparison of methane emission measurements using Eddy Covariance and manual and automated chamber-based techniques in Tibetan Plateau alpine wetland.

    PubMed

    Yu, Lingfei; Wang, Hao; Wang, Guangshuai; Song, Weimin; Huang, Yao; Li, Sheng-Gong; Liang, Naishen; Tang, Yanhong; He, Jin-Sheng

    2013-10-01

    Comparing of different CH4 flux measurement techniques allows for the independent evaluation of the performance and reliability of those techniques. We compared three approaches, the traditional discrete Manual Static Chamber (MSC), Continuous Automated Chamber (CAC) and Eddy Covariance (EC) methods of measuring the CH4 fluxes in an alpine wetland. We found a good agreement among the three methods in the seasonal CH4 flux patterns, but the diurnal patterns from both the CAC and EC methods differed. While the diurnal CH4 flux variation from the CAC method was positively correlated with the soil temperature, the diurnal variation from the EC method was closely correlated with the solar radiation and net CO2 fluxes during the daytime but was correlated with the soil temperature at nighttime. The MSC method showed 25.3% and 7.6% greater CH4 fluxes than the CAC and EC methods when measured between 09:00 h and 12:00 h, respectively.

  19. Methane fluxes measured by eddy covariance and static chamber techniques at a temperate forest in central ontario, Canada

    NASA Astrophysics Data System (ADS)

    Wang, J. M.; Murphy, J. G.; Geddes, J. A.; Winsborough, C. L.; Basiliko, N.; Thomas, S. C.

    2012-12-01

    Methane flux measurements were carried out at a temperate forest (Haliburton Forest and Wildlife Reserve) in central Ontario (45°17´11´´ N, 78°32´19´´ W) from June-October, 2011. Continuous measurements were made by an off-axis integrated cavity output spectrometer Fast Greenhouse Gas Analyzer (FGGA) from Los Gatos Research Inc. that measures methane (CH4) at 10 Hz sampling rates. Fluxes were calculated from the gas measurements in conjunction with wind data collected by a 3-D sonic anemometer using the eddy covariance (EC) method. Observed methane fluxes showed net uptake of CH4 over the measurement period with an average uptake flux (± standard deviation of the mean) of -2.7 ± 0.13 nmol m-2 s-1. Methane fluxes showed a seasonal progression with average rates of uptake increasing from June through September and remaining high in October. This pattern was consistent with a decreasing trend in soil moisture content at the monthly time scale. On the diurnal timescale, there was evidence of increased uptake during the day, when the mid-canopy wind speed was at a maximum. These patterns suggest that substrate supply of CH4 and oxygen to methanotrophs, and in certain cases hypoxic soil conditions supporting methanogenesis in low-slope areas, drive the observed variability in fluxes. A network of soil static chambers used at the tower site showed close agreement with the eddy covariance flux measurements. This suggests that soil-level microbial processes, and not abiological leaf-level CH4 production, drive overall CH4 dynamics in temperate forest ecosystems such as Haliburton Forest.

  20. Semidiurnal and seasonal variations in methane (CH4) emissions from a subtropical hydroelectric reservoir (Nam Theun 2 Reservoir) measured by eddy covariance technique

    NASA Astrophysics Data System (ADS)

    Deshmukh, Chandrashekhar; Serça, Dominique; Tardif, Raphael; Demarty, Maud; Descloux, Stéphane; Chanudet, Vincent; Guédant, Pierre; Guérin, Frédéric

    2013-04-01

    Hydroelectric reservoirs have globally been identified as a significant source of methane (CH4) to the atmosphere, especially in the tropics. Assessing these emissions and their variations at small and large time scale represent important scientific challenges. In this context, the objectives of this work are (i) to compare different methodologies used to assess CH4 emissions. (ii) to determine the temporal variations in these emissions at different scales i.e. from daily to seasonal, and link these variations to environmental controlling factors. Measurements of CH4 emissions were made in a recently impounded (May 2008) subtropical hydroelectric reservoir, Nam Theun 2 (NT2), in Lao PDR, Asia. The sampling strategy included three different types of flux measurement techniques: floating chambers (FC), submerged funnels (SF), and the eddy covariance technique (EC). Flux measurements were carried out during four field campaigns conducted between May 2009 and June 2011. Eddy covariance system, composed by a 3D sonic anemometer coupled with a DLT-100 fast methane analyzer (Los Gatos Inc®), was deployed on a mast erected in a large surface of open water. Diffusive and bubbling fluxes were measured using respectively the FC and the SF techniques within the footprint of the EC station. Results from the four field campaigns show individual EC fluxes (30min) varying over 4 orders of magnitude (from 0.01 to 102 mmol.m-2.day-1). Individual diffusive fluxes measured by floating chambers ranged between 0.2 and 3.2 mmol.m-2.day-1. Bubbling fluxes were found to be highly sporadic, with individual daily flux values varying from 0 to 102 mmol.m-2.day-1. For all field campaigns, EC fluxes were very consistent with the sum of the two terms measured independently (diffusive fluxes + bubbling fluxes = EC fluxes), indicating that the eddy covariance system picked-up both diffusive and bubbling emissions from the reservoir, which is a very new and encouraging result for further studies

  1. Non-contact online thickness measurement system for metal films based on eddy current sensing with distance tracking technique.

    PubMed

    Li, Wei; Wang, Hongbo; Feng, Zhihua

    2016-04-01

    This paper proposes an online, non-contact metal film thickness measurement system based on eddy current sensing. The slope of the lift-off curve (LOC) is used for characterizing target thickness. Theoretical derivation was conducted to prove that the slope is independent of the lift-off variation. In practice, the measurement has some immunity to the lift-off, but not perfect. The slope of LOC is still affected at some extent by the lift-off. Hence, a height tracking system was also proposed, which could stabilize the distance between the sensor and the target and significantly reduce the lift-off effect. The height tracking system contains a specially designed probe, which could vibrate rapidly to obtain a fast measurement speed, and its height can be adjusted up and down continuously to stabilize the lift-off. The sensor coil in the thickness measurement system was also used as the height sensor in the height tracking system. Several experiments were conducted to test the system performances under static and dynamic conditions. This measurement system demonstrated significant advantages, such as simple and clear conversion between the slope of LOC and target thickness, high resolution and stability, and minimized effect of lift-off variation.

  2. Non-contact online thickness measurement system for metal films based on eddy current sensing with distance tracking technique

    NASA Astrophysics Data System (ADS)

    Li, Wei; Wang, Hongbo; Feng, Zhihua

    2016-04-01

    This paper proposes an online, non-contact metal film thickness measurement system based on eddy current sensing. The slope of the lift-off curve (LOC) is used for characterizing target thickness. Theoretical derivation was conducted to prove that the slope is independent of the lift-off variation. In practice, the measurement has some immunity to the lift-off, but not perfect. The slope of LOC is still affected at some extent by the lift-off. Hence, a height tracking system was also proposed, which could stabilize the distance between the sensor and the target and significantly reduce the lift-off effect. The height tracking system contains a specially designed probe, which could vibrate rapidly to obtain a fast measurement speed, and its height can be adjusted up and down continuously to stabilize the lift-off. The sensor coil in the thickness measurement system was also used as the height sensor in the height tracking system. Several experiments were conducted to test the system performances under static and dynamic conditions. This measurement system demonstrated significant advantages, such as simple and clear conversion between the slope of LOC and target thickness, high resolution and stability, and minimized effect of lift-off variation.

  3. Non-contact online thickness measurement system for metal films based on eddy current sensing with distance tracking technique.

    PubMed

    Li, Wei; Wang, Hongbo; Feng, Zhihua

    2016-04-01

    This paper proposes an online, non-contact metal film thickness measurement system based on eddy current sensing. The slope of the lift-off curve (LOC) is used for characterizing target thickness. Theoretical derivation was conducted to prove that the slope is independent of the lift-off variation. In practice, the measurement has some immunity to the lift-off, but not perfect. The slope of LOC is still affected at some extent by the lift-off. Hence, a height tracking system was also proposed, which could stabilize the distance between the sensor and the target and significantly reduce the lift-off effect. The height tracking system contains a specially designed probe, which could vibrate rapidly to obtain a fast measurement speed, and its height can be adjusted up and down continuously to stabilize the lift-off. The sensor coil in the thickness measurement system was also used as the height sensor in the height tracking system. Several experiments were conducted to test the system performances under static and dynamic conditions. This measurement system demonstrated significant advantages, such as simple and clear conversion between the slope of LOC and target thickness, high resolution and stability, and minimized effect of lift-off variation. PMID:27131700

  4. Comparison between eddy covariance and automatic chamber techniques for measuring net ecosystem exchange of carbon dioxide in cotton and wheat fields

    NASA Astrophysics Data System (ADS)

    Wang, K.; Liu, C.; Zheng, X.; Pihlatie, M.; Li, B.; Haapanala, S.; Vesala, T.; Liu, H.; Wang, Y.; Liu, G.; Hu, F.

    2013-11-01

    Static and transparent automatic chamber (AC) technique is a necessary choice for measuring net ecosystem exchange (NEE) of carbon dioxide (CO2) in circumstances where eddy covariance (EC) technique is not applicable. However, a comparison of the two techniques for measurements on croplands has seldom been undertaken. We carried out NEE observations in a cotton field (for one year) and a winter wheat field (for one cropping season) using both AC and EC techniques, to (a) compare the NEE fluxes measured using each technique, and (b) test the NEE measurement performance of an automatic chamber system (AMEG), which was designed for simultaneous flux measurements of multiple gases. The half-hourly NEE fluxes measured with the two techniques were in approximate agreement, with the AC fluxes being 0.78 (cotton) and 1.06 (wheat) times the size of the EC fluxes. When integrated to daily timescale, the fluxes of the two techniques were in better agreement, showing an average ratio of 0.94 and 1.00 for the cotton and wheat, respectively. During the periods with comparable field conditions and normal performance of both instruments, the cumulative NEE fluxes revealed small differences between the two techniques (-9.0% ~ 7%, with a mean of 0.1%). The measurements resulted in an annual cumulative NEE of -40 g C m-2 yr-1 (EC) and -42 g C m-2 yr-1 (AC) in the cotton field, and a seasonal cumulative NEE of -251 g C m-2 (EC) and -205 g C m-2 (AC) in the wheat field. Our results indicate that, for cropland populated by short plants, the AMEG system and the data processing procedures applied in this study are able to provide NEE estimates comparable to those from EC measurements.

  5. Transient eddies in the MACDA Mars reanalysis

    NASA Astrophysics Data System (ADS)

    Mooring, Todd A.; Wilson, R. John

    2015-10-01

    We present a survey of the transient eddy activity in the Mars Analysis Correction Data Assimilation (MACDA) reanalysis. The spatial structure and propagation characteristics of the eddies are emphasized. Band-pass-filtered variance and covariance fields are found to be zonally modulated, indicating a longitude dependence of the typical amplitudes of Martian transient eddies. Considerable repeatability of the eddy field spatial structures is found across Mars years, including a roughly wave number 3 pattern of low-level eddy meridional temperature transport (v'T'¯) in the northern hemisphere that is evident before and after winter solstice and a possible tendency for northern hemisphere eddy kinetic energy maxima to be located above low-lying areas. Southern hemisphere eddy fields tend to feature two local maxima, one roughly south of Tharsis and the other associated with Hellas. Eddies are weakened near winter solstice in both hemispheres and were generally weakened in the northern hemisphere during the 2001 (Mars year 25) global dust storm, albeit with little change in spatial patterns. Because the transient eddies propagate in space, we also used a teleconnection map-based technique to estimate their phase velocities. Eddy propagation at the surface is found to follow topography, a phenomenon less evident at higher altitude. Possible physical mechanisms underlying the documented eddy phenomena are discussed.

  6. Nonperiodic eddy pulsations

    USGS Publications Warehouse

    Rubin, David M.; McDonald, Richard R.

    1995-01-01

    Recirculating flow in lateral separation eddies is typically weaker than main stem flow and provides an effective environment for trapping sediment. Observations of recirculating flow and sedimentary structures demonstrate that eddies pulsate in size and in flow velocity even when main stem flow is steady. Time series measurements of flow velocity and location of the reattachment point indicate that these pulsations are nonperiodic. Nonperiodic flow in the lee of a channel margin constriction is grossly different from the periodic flow in the lee of a cylinder that is isolated in a flow. Our experiments demonstrate that placing a flow-parallel plate adjacent to a cylinder is sufficient to cause the leeside flow to change from a periodic sequence of vortices to a nonperiodically pulsating lateral separation eddy, even if flow conditions are otherwise unchanged. Two processes cause the leeside flow to become nonperiodic when the plate is added. First, vortices that are shed from the cylinder deform and become irregular as they impact the plate or interfere with remnants of other vortices near the reattachment point. Second, these deformed vortices and other flow structures are recirculated in the lateral separation eddy, thereby influencing the future state (pressure and momentum distribution) of the recirculating flow. The vortex deformation process was confirmed experimentally by documenting spatial differences in leeside flow; vortex shedding that is evident near the separation point is undetectable near the reattachment point. Nonlinear forecasting techniques were used in an attempt to distinguish among several possible kinds of nonperiodic flows. The computational techniques were unable to demonstrate that any of the nonperiodic flows result from low-dimensional nonlinear processes.

  7. Inexpensive Eddy-Current Standard

    NASA Technical Reports Server (NTRS)

    Berry, Robert F., Jr.

    1985-01-01

    Radial crack replicas serve as evaluation standards. Technique entails intimately joining two pieces of appropriate aluminum alloy stock and centering drilled hole through and along interface. Bore surface of hole presents two vertical stock interface lines 180 degrees apart. These lines serve as radial crack defect replicas during eddy-current technique setup and verification.

  8. Easy sperm processing technique allowing exclusive accumulation and later usage of DNA-strandbreak-free spermatozoa.

    PubMed

    Ebner, T; Shebl, O; Moser, M; Mayer, R B; Arzt, W; Tews, G

    2011-01-01

    Sperm DNA fragmentation is increased in poor-quality semen samples and correlates with failed fertilization, impaired preimplantation development and reduced pregnancy outcome. Common sperm preparation techniques may reduce the percentage of strandbreak-positive spermatozoa, but, to date, there is no reliable approach to exclusively accumulate strandbreak-free spermatozoa. To analyse the efficiency of special sperm selection chambers (Zech-selectors made of glass or polyethylene) in terms of strandbreak reduction, 39 subfertile men were recruited and three probes (native, density gradient and Zech-selector) were used to check for strand breaks using the sperm chromatin dispersion test. The mean percentage of affected spermatozoa in the ejaculate was 15.8 ± 7.8% (range 5.0–42.1%). Density gradient did not significantly improve the quality of spermatozoa selected(14.2 ± 7.0%). However, glass chambers completely removed 90% spermatozoa showing strand breaks and polyethylene chambers removed 76%. Both types of Zech-selectors were equivalent in their efficiency, significantly reduced DNA damage (P < 0.001) and,with respect to this, performed better than density gradient centrifugation (P < 0.001). As far as is known, this is the first report ona sperm preparation technique concentrating spermatozoa unaffected in terms of DNA damage. The special chambers most probably select for sperm motility and/or maturity.

  9. A Low Power Digital Accumulation Technique for Digital-Domain CMOS TDI Image Sensor.

    PubMed

    Yu, Changwei; Nie, Kaiming; Xu, Jiangtao; Gao, Jing

    2016-01-01

    In this paper, an accumulation technique suitable for digital domain CMOS time delay integration (TDI) image sensors is proposed to reduce power consumption without degrading the rate of imaging. In terms of the slight variations of quantization codes among different pixel exposures towards the same object, the pixel array is divided into two groups: one is for coarse quantization of high bits only, and the other one is for fine quantization of low bits. Then, the complete quantization codes are composed of both results from the coarse-and-fine quantization. The equivalent operation comparably reduces the total required bit numbers of the quantization. In the 0.18 µm CMOS process, two versions of 16-stage digital domain CMOS TDI image sensor chains based on a 10-bit successive approximate register (SAR) analog-to-digital converter (ADC), with and without the proposed technique, are designed. The simulation results show that the average power consumption of slices of the two versions are 6 . 47 × 10 - 8 J/line and 7 . 4 × 10 - 8 J/line, respectively. Meanwhile, the linearity of the two versions are 99.74% and 99.99%, respectively. PMID:27669256

  10. A comparison of methane emission measurements using Eddy Covariance and manual and automated chamber-based techniques in Tibetan Plateau alpine wetland.

    PubMed

    Yu, Lingfei; Wang, Hao; Wang, Guangshuai; Song, Weimin; Huang, Yao; Li, Sheng-Gong; Liang, Naishen; Tang, Yanhong; He, Jin-Sheng

    2013-10-01

    Comparing of different CH4 flux measurement techniques allows for the independent evaluation of the performance and reliability of those techniques. We compared three approaches, the traditional discrete Manual Static Chamber (MSC), Continuous Automated Chamber (CAC) and Eddy Covariance (EC) methods of measuring the CH4 fluxes in an alpine wetland. We found a good agreement among the three methods in the seasonal CH4 flux patterns, but the diurnal patterns from both the CAC and EC methods differed. While the diurnal CH4 flux variation from the CAC method was positively correlated with the soil temperature, the diurnal variation from the EC method was closely correlated with the solar radiation and net CO2 fluxes during the daytime but was correlated with the soil temperature at nighttime. The MSC method showed 25.3% and 7.6% greater CH4 fluxes than the CAC and EC methods when measured between 09:00 h and 12:00 h, respectively. PMID:23838484

  11. Semidiurnal and seasonal variations in methane emissions from a sub-tropical hydroelectric reservoir (Nam Theun 2, Laos) measured by eddy covariance technique

    NASA Astrophysics Data System (ADS)

    Deshmukh, C.; Serca, D.; Guerin, F.; Meyerfeld, Y.; Descloux, S.; Chanudet, V.; Pighini, S.; Godon, A.; Guedant, P.

    2012-12-01

    The quantification of sources and sinks of greenhouse gases (GHG) have become an important scientific issue. Hydroelectric reservoirs have been identified as considerable methane (CH4) sources to the atmosphere, especially in the tropics. Assessing these emissions and their variations on small and large time scale represent important challenges in our understanding of water-atmosphere exchange. In this context, objectives of this study are (i) to quantify the CH4 emissions, (ii) to determine the variations in the emissions on daily and seasonal time scale, and link these variations to environmental driving forces (iii) to compare different methodologies to assess CH4 emissions. Measurements of CH4 emissions were made in a recently impounded (in 2009) subtropical hydroelectric reservoir, Nam Theun 2 (NT2), in Lao PDR, Asia. The sampling strategy included three different types of flux measurement techniques: floating chambers, submerged funnels, and a micrometeorological station allowing for flux determination based on the eddy covariance technique (EC). We carried out flux measurements during four intensive field campaigns conducted in between May 2009 and June 2011. Eddy covariance system, composed by a 3D sonic anemometer coupled with a cavity ring-down spectroscopy (CRDS) analyzer, was deployed on the mast in a large surface of open water corresponding to an homogeneous ecosystem (floodplain). Diffusive and bubbling fluxes were measured using respectively floating chambers and submerged funnel techniques around the mast. Our results from the all four field campaigns show that individual 30-min EC fluxes varied by 4 order of magnitude (from 0.01 to 102 mmol.m-2.day-1). Average EC fluxes of individual campaigns varied inversely with water depth, from 5±3.5 to 28±16 mmol.m-2.day-1 for respectively from 10.5 to 2 m of water depths. Diffusive fluxes measured by floating chambers ranged between 0.2 and 3.2 mmol.m-2.day-1. Bubbling fluxes were found to be highly

  12. Comparison between eddy covariance and automatic chamber techniques for measuring net ecosystem exchange of carbon dioxide in cotton and wheat fields

    NASA Astrophysics Data System (ADS)

    Wang, K.; Liu, C.; Zheng, X.; Pihlatie, M.; Li, B.; Haapanala, S.; Vesala, T.; Liu, H.; Wang, Y.; Liu, G.; Hu, F.

    2013-05-01

    Static and transparent automatic chamber (AC) technique is a~necessary choice for measuring net ecosystem exchange (NEE) of carbon dioxide (CO2) in circumstances where eddy covariance (EC) technique is not applicable. However, a comparison of the two techniques for measurements on croplands has seldom been undertaken. We carried out NEE observations in a cotton field (for one year) and a winter wheat field (for one cropping season) using both AC and EC techniques, to (a) compare the NEE fluxes measured using each technique, and (b) test the NEE measurement performance of an automatic chamber system (AMEG), which was designed for simultaneous flux measurements of multiple gases. The half-hourly NEE fluxes measured with the two techniques were in approximate agreement, with the AC fluxes being 0.78 (cotton) and 1.06 (wheat) times those of the EC. When integrated to daily timescale, the fluxes of the two techniques were in better agreement, showing an average ratio of 0.94 and 1.00 for the cotton and wheat, respectively. During the periods with comparable field conditions and normal performance of both instruments, the cumulative NEE fluxes revealed small differences between the two techniques (-9.0 ~ 6.7%, with a mean of 0.1%). The measurements resulted in annual cumulative NEE of -40 g C m-2 yr-1 (EC) and -42 g C m-2 yr-1 (AC) in the cotton field and seasonal cumulative NEE of -251 g C m-2 (EC) and -205 g C m-2 (AC) in the wheat field. Our results indicate that, for cropland populated by short plants, the AMEG system and the data processing procedures applied in this study are able to provide NEE estimates comparable to those from EC measurements, although either technique may lead to an overestimation of the loss rate (or underestimation of the gain rate) of the soil organic carbon stock of an ecosystem, in particular with calcareous soils exposed to increasing atmospheric acid deposition.

  13. Thin film eddy current impulse deicer

    NASA Technical Reports Server (NTRS)

    Smith, Samuel O.; Zieve, Peter B.

    1990-01-01

    Two new styles of electrical impulse deicers has been developed and tested in NASA's Icing Research Tunnel. With the Eddy Current Repulsion Deicing Boot (EDB), a thin and flexible spiral coil is encapsulated between two thicknesses of elastomer. The coil, made by an industrial printed circuit board manufacturer, is bonded to the aluminum aircraft leading edge. A capacitor bank is discharged through the coil. Induced eddy currents repel the coil from the aluminum aircraft structure and shed accumulated ice. A second configuration, the Eddy Current Repulsion Deicing-Strip (EDS) uses an outer metal erosion strip fastened over the coil. Opposite flowing eddy currents repel the strip and create the impulse deicing force. The outer strip serves as a surface for the collection and shedding of ice and does not require any structural properties. The EDS is suitable for composite aircraft structures. Both systems successfully dispelled over 95 percent of the accumulated ice from airfoils over the range of the FAA icing envelope.

  14. Comparison of Ecosystem Water-use Efficiency Among Douglas fir Forest, Aspen Forest and Grassland Using Eddy Covariance and Carbon Isotope Techniques

    NASA Astrophysics Data System (ADS)

    Flanagan, L. B.; Ponton, S.; Alstad, K. P.; Johnson, B. G.; Morgenstern, K.; Kljun, N.; Black, T. A.; Barr, A. G.

    2005-12-01

    Comparisons were made among Douglas fir forest, aspen (broad leaf deciduous) forest and wheatgrass (C3) grassland for ecosystem-level water-use efficiency. Water-use efficiency (WUE) was defined as the ratio of photosynthetic CO2 assimilation rate and evapo-transpiration (ET) rate. The ET data measured by eddy covariance were screened so that they overwhelmingly represented transpiration. The three sites used in this comparison spanned a range of vegetation (plant functional) types and environmental conditions within western Canada. When compared in the relative order Douglas fir (located on Vancouver Island, B.C), aspen (northern Saskatchewan), grassland (southern Alberta), the sites demonstrated a progressive decline in precipitation and a general increase in maximum air temperature and atmospheric saturation deficit (D) during the mid-summer. The average WUE at the grassland site was 2.6 mmol mol-1, which was much lower than the average values observed for the two other sites (aspen: 5.4, Douglas fir: 8.1). The differences in WUE among sites were primarily due to variation in ET. The highest maximum ET rates were approximately 5, 3.2 and 2.7 mm day-1 for the grassland, aspen and Douglas fir sites, respectively. There was a strong negative correlation between WUE and D for all sites. We also made seasonal measurements of the carbon isotope ratio of ecosystem respired CO2 (δR) in order to test for the expected correlation between shifts in environmental conditions and changes to the ecosystem-integrated ratio of leaf intercellular to ambient CO2 concentration (ci/ca). There was a consistent increase in δR values in the grassland, aspen forest and Douglas fir forest associated with a seasonal reduction in soil moisture. Comparisons were made between WUE measured using eddy covariance with that calculated based on atmospheric saturation deficit and δR measurements. There was excellent agreement between WUE values calculated using the two techniques. Our

  15. Assessment of the soil water balance by the combination of cosmic ray neutron sensing and eddy covariance technique in an irrigated citrus orchard (Marrakesh, Morocco)

    NASA Astrophysics Data System (ADS)

    Mroos, Katja; Baroni, Gabriele; Er-Raki, Salah; Francke, Till; Khabba, Said; Jarlan, Lionel; Hanich, Lahoucine; Oswald, Sascha E.

    2014-05-01

    Irrigation water requirement plays a crucial role in many agricultural areas and especially in arid and semi-arid landscapes. Improvements in the water management and the performance of the irrigation systems require a correct evaluation of the hydrological processes involved. However, some difficulties can arise due to the heterogeneity of the soil-plant system and of the irrigation scheme. To overcome these limitations, in this study, the soil water balance is analyzed by the combination of the Eddy Covariance technique (EC) and Cosmic Ray neutron Sensing (CRS). EC provides the measurement of the actual evapotranspiration over the area as it was presented in many field conditions. Moreover CRS showed to be a valuable approach to measure the root zone soil moisture integrated in a footprint of ~30 ha. In this way, the combination of the two methodologies should provide a better analysis of the soil water balance at field scale, as opposed to point observations, e.g. by TDR, evaporimeter and fluxmeter. Then, this could increase the capability to assess the irrigation efficiency and the agricultural water management. The study is conducted in a citrus orchard situated in a semi-arid region, 30 km southwest of Marrakesh (Morocco). The site is flat and planted with trees of same age growing in parallel rows with drip irrigation lines and application of fertilizer and pesticides. The original soil seems modified on the surface by the agricultural use, creating differences between trees, rows and lines. In addition, the drip irrigation creates also a spatial variability of the water flux distribution in the field, making this site an interesting area to test the methodology. Particular attention is given to the adaptation of the standard soil sampling campaign used for the calibration of the CRS and the introduction of a weighing function. Data were collected from June to December 2013, which corresponds to the high plant transpiration. Despite the intention of the

  16. Eddy current scanning at Fermilab

    SciTech Connect

    Boffo, C.; Bauer, P.; Foley, M.; Brinkmann, A.; Ozelis, J.; /Jefferson Lab

    2005-07-01

    In the framework of SRF cavity development, Fermilab is creating the infrastructure needed for the characterization of the material used in the cavity fabrication. An important step in the characterization of ''as received'' niobium sheets is the eddy current scanning. Eddy current scanning is a non-destructive technique first adopted and further developed by DESY with the purpose of checking the cavity material for sub-surface defects and inclusions. Fermilab has received and further upgraded a commercial eddy current scanner previously used for the SNS project. The upgrading process included developing new filtering software. This scanner is now used daily to scan the niobium sheets for the Fermilab third harmonic and transverse deflecting cavities. This paper gives a status report on the scanning results obtained so far, including a discussion of the typology of signals being detected. We also report on the efforts to calibrate this scanner, a work conducted in collaboration with DESY.

  17. A new approach of weighted integration technique based on accumulated images using dynamic PET and H2(15)O

    SciTech Connect

    Yokoi, T.; Kanno, I.; Iida, H.; Miura, S.; Uemura, K. )

    1991-05-01

    We developed a new technique of weighted integration for the measurement of local cerebral blood flow (LCBF) and the blood-tissue partition coefficient (p) using dynamic positron emission tomography (PET) and H2(15)O. The weighted integration in the new technique is carried out on the equation of the first time integration of the Kety-Schmidt differential equation. Practically, serially accumulated images with sequentially prolonged accumulation times are weighted by two arbitrary functions. The weighting functions do not have to be differentiated because of the exclusion of the differential term in the starting equation. Consequently, the method does not require data at the end of the scan. The technique was applied to H2(15)O dynamic PET performed on four normal subjects, and was verified to provide a better signal-to-noise ratio than the previously developed integrated projection (IP) technique. Computer simulations were carried out to investigate the effects of statistical noise, tissue heterogeneity, and time delay and dispersion in arterial input function. The simulation showed that the new technique provided about a 1.4 times lower statistical error in both LCBF and p at 50 ml 100 g-1 min-1 compared to the IP technique, and it should be noted that the new technique was less sensitive to the shape of the weighting functions. The new technique provides a new strategy with respect to the statistical error for estimation of LCBF and p.

  18. An Approach to Minimizing Artifacts Caused by Cross-Sensitivity in the Determination of Air-Sea CO2 Flux Using the Eddy-Covariance Technique

    NASA Astrophysics Data System (ADS)

    Duan, Ziqiang; Gao, Huiwang; Gao, Zengxiang; Wang, Renlei; Xue, Yuhuan; Yao, Xiaohong

    2013-07-01

    The air-sea CO2 flux was measured from a research vessel in the North Yellow Sea in October 2007 using an open-path eddy-covariance technique. In 11 out of 64 samples, the normalized spectra of scalars (C}2, water vapour, and temperature) showed similarities. However, in the remaining samples, the normalized CO2 spectra were observed to be greater than those of water vapour and temperature at low frequencies. In this paper, the noise due to cross-sensitivity was identified through a combination of intercomparisons among the normalized spectra of three scalars and additional analyses. Upon examination, the cross-sensitivity noise appeared to be mainly present at frequencies {<}0.8 Hz. Our analysis also suggested that the high-frequency fluctuations of CO2 concentration (frequency {>}0.8 Hz) was probably less affected by the cross-sensitivity. To circumvent the cross-sensitivity issue, the cospectrum in the high-frequency range 0.8-1.5 Hz, instead of the whole range, was used to estimate the CO2 flux by taking the contribution of the high frequency to the CO2 flux to be the same as the contribution to the water vapour flux. The estimated air-sea CO2 flux in the North Yellow Sea was -0.039 ± 0.048 mg m^{-2} s^{-1}, a value comparable to the estimates using the inertial dissipation method and Edson's method (Edson et al., J Geophys Res 116:C00F10, 2011).

  19. Anisotropic eddy viscosity models

    NASA Technical Reports Server (NTRS)

    Carati, D.; Cabot, W.

    1996-01-01

    A general discussion on the structure of the eddy viscosity tensor in anisotropic flows is presented. The systematic use of tensor symmetries and flow symmetries is shown to reduce drastically the number of independent parameters needed to describe the rank 4 eddy viscosity tensor. The possibility of using Onsager symmetries for simplifying further the eddy viscosity is discussed explicitly for the axisymmetric geometry.

  20. Large Eddy Simulation of a Turbulent Jet

    NASA Technical Reports Server (NTRS)

    Webb, A. T.; Mansour, Nagi N.

    2001-01-01

    Here we present the results of a Large Eddy Simulation of a non-buoyant jet issuing from a circular orifice in a wall, and developing in neutral surroundings. The effects of the subgrid scales on the large eddies have been modeled with the dynamic large eddy simulation model applied to the fully 3D domain in spherical coordinates. The simulation captures the unsteady motions of the large-scales within the jet as well as the laminar motions in the entrainment region surrounding the jet. The computed time-averaged statistics (mean velocity, concentration, and turbulence parameters) compare well with laboratory data without invoking an empirical entrainment coefficient as employed by line integral models. The use of the large eddy simulation technique allows examination of unsteady and inhomogeneous features such as the evolution of eddies and the details of the entrainment process.

  1. Unified Ultrasonic/Eddy-Current Data Acquisition

    NASA Technical Reports Server (NTRS)

    Chern, E. James; Butler, David W.

    1993-01-01

    Imaging station for detecting cracks and flaws in solid materials developed combining both ultrasonic C-scan and eddy-current imaging. Incorporation of both techniques into one system eliminates duplication of computers and of mechanical scanners; unifies acquisition, processing, and storage of data; reduces setup time for repetitious ultrasonic and eddy-current scans; and increases efficiency of system. Same mechanical scanner used to maneuver either ultrasonic or eddy-current probe over specimen and acquire point-by-point data. For ultrasonic scanning, probe linked to ultrasonic pulser/receiver circuit card, while, for eddy-current imaging, probe linked to impedance-analyzer circuit card. Both ultrasonic and eddy-current imaging subsystems share same desktop-computer controller, containing dedicated plug-in circuit boards for each.

  2. OSL and TL techniques combined in a beryllium oxide detector to evaluate simultaneously accumulated and single doses.

    PubMed

    Malthez, Anna L M C; Freitas, Marcelo B; Yoshimura, Elisabeth M; Umisedo, Nancy K; Button, Vera L S N

    2016-04-01

    Optically stimulated luminescence (OSL) and thermoluminescence (TL) are similar techniques widely used in radiation dosimetry. The main difference between these techniques is the stimulus to induce luminescence emission: TL technique uses thermal stimulation, whereas OSL uses optical stimulation. One of the main intrinsic characteristics of the OSL technique is the possibility of reading several times the dosimetric materials with a negligible loss of signal. In the case of BeO, recent studies have shown that TL stimulation up to 250°C does not affect its OSL signal. Taking the advantages of dosimetric characteristics of BeO combined with both techniques, in this study, we demonstrated the possibility of measuring accumulated and single doses in the same BeO-based detector in order to use it to improve individual monitoring of radiation workers exposed to X-ray or gamma-ray fields. Single doses were measured using TL technique by heating the detector up to 250°C, whereas accumulated doses were estimated using OSL technique in the same detector in a relatively short time of optical stimulation. The detectors were exposed to two energies: 28keV X-rays and 1.25MeV Co-60 gamma rays. The doses estimated by OSL and TL of BeO (Thermalox 995) were compared with those obtained with LiF (TLD-100) and recorded with a calibrated ionization chamber. The results indicate that combined OSL and TL signals of BeO detectors can provide additional information of accumulated dose, with additional exploration of the advantages of both techniques, such as speed in readouts with OSL, and double-check the doses using TL and OSL intensities from BeO. PMID:26784853

  3. Southern Ocean eddy phenomenology

    NASA Astrophysics Data System (ADS)

    Frenger, I.; Münnich, M.; Gruber, N.; Knutti, R.

    2015-11-01

    Mesoscale eddies are ubiquitous features in the Southern Ocean, yet their phenomenology is not well quantified. To tackle this task, we use satellite observations of sea level anomalies and sea surface temperature (SST) as well as in situ temperature and salinity measurements from profiling floats. Over the period 1997-2010, we identified over a million mesoscale eddy instances and were able to track about 105 of them over 1 month or more. The Antarctic Circumpolar Current (ACC), the boundary current systems, and the regions where they interact are hot spots of eddy presence, representing also the birth places and graveyards of most eddies. These hot spots contrast strongly to areas shallower than about 2000 m, where mesoscale eddies are essentially absent, likely due to topographical steering. Anticyclones tend to dominate the southern subtropical gyres, and cyclones the northern flank of the ACC. Major causes of regional polarity dominance are larger formation numbers and lifespans, with a contribution of differential propagation pathways of long-lived eddies. Areas of dominance of one polarity are generally congruent with the same polarity being longer-lived, bigger, of larger amplitude, and more intense. Eddies extend down to at least 2000 m. In the ACC, eddies show near surface temperature and salinity maxima, whereas eddies in the subtropical areas generally have deeper anomaly maxima, presumably inherited from their origin in the boundary currents. The temperature and salinity signatures of the average eddy suggest that their tracer anomalies are a result of both trapping in the eddy core and stirring.

  4. Application of optically stimulated luminescence technique to evaluate simultaneously accumulated and single doses with the same dosimeter

    NASA Astrophysics Data System (ADS)

    Malthez, Anna Luiza M. C.; Freitas, Marcelo B.; Yoshimura, Elisabeth M.; Button, Vera L. S. N.

    2014-02-01

    Optically stimulated luminescence dosimeters (OSLD) can be read several times with a negligible loss (degradation) of signal. In this work, we explore this OSL property to estimate simultaneously the accumulated and single doses using a unique Al2O3 dosimeter, irradiated repeated times along over 4 months. This was done through several irradiations of OSLD (Landauer Luxel Dots) with two energies (28 keV X-rays and 1.25 MeV Co-60 gamma rays) and several doses distributed over time. Thermoluminescent dosimeters (TLD) were used as a reference to compare the estimated doses obtained with OSLD. For each irradiation, and both energies, a calibration curve was evaluated with OSLD and TLD to estimate the dose values. The OSL readouts were made with a MicroStar (Landauer) OSL reader. To estimate background (BG) over time, a set of OSLD and TLD (Bycron TLD100) was not irradiated and BG was monitored at each readout section. After irradiations, the OSL and TL signals were converted to dose and values were compared. As a set of OSLD suffered no bleaching after the readouts, it was possible to estimate simultaneously the accumulated and single doses with a unique OSLD. Each single dose was estimated through the subtraction of successive accumulated doses determined for each single OSLD. We concluded that the single doses determined by OSL and TL techniques were compatible, and that the accumulated dose, obtained with OSL technique was comparable to the sum of single doses determined with TLD. We can conclude that using OSL technique and Al2O3 dosimeters it is possible to estimate simultaneously accumulated and single doses with the same dosimeter irradiated with low or high energy photons.

  5. Eddy current inspection of graphite fiber components

    NASA Technical Reports Server (NTRS)

    Workman, G. L.; Bryson, C. C.

    1990-01-01

    The recognition of defects in materials properties still presents a number of problems for nondestructive testing in aerospace systems. This project attempts to utilize current capabilities in eddy current instrumentation, artificial intelligence, and robotics in order to provide insight into defining geometrical aspects of flaws in composite materials which are capable of being evaluated using eddy current inspection techniques. The unique capabilities of E-probes and horseshoe probes for inspecting probes for inspecting graphite fiber materials were evaluated and appear to hold great promise once the technology development matures. The initial results are described of modeling eddy current interactions with certain flaws in graphite fiber samples.

  6. Seasonal Dynamics of N2O and CO2 Emissions from a Corn Production System measured with the Eddy covariance and Chamber techniques

    NASA Astrophysics Data System (ADS)

    Iwuozo, S. A.; Hui, D.; Dennis, S.

    2013-12-01

    Agricultural Practices play a major role in the global fluxes of the greenhouse gases carbon dioxide, nitrous oxide, and methane. The use of fertilizer in Corn production has generated concerns about its contribution to global climate change. Thus, farmers and others concerned have become interested in more efficient fertilization management practice and reduced greenhouse gas emissions. To understand best management practices, in the 2012 and 2013 corn growing seasons, field experiments was conducted at Tennessee State University Agricultural Research and Demonstration Center in Nashville, TN. The study examines the seasonal variations of (N2O) and (CO2) emissions from soil as a function of six treatment that include inorganic nitrogen fertilizer, chicken litter and biochar application. The combinations were: regular URAN 32-0-0 liquid fertilizer (2 times) no till, regular URAN 32-0-0 liquid fertilizer (2 times) conventional till, multiple URAN applications (4 times) no till, Denitrification inhibitor with regular URAN application in no till, chicken litter with regular URAN application no till and URAN application with biochar in no tilled plots. Each treatment was replicated 6 times. N2O and CO2 emissions were measured using a closed chamber method after rainfall event(s), fertilizer applications or every two weeks whichever was shorter. Corresponding soil NH4+-N and NO3--N, soil temperature and moisture were also measured during gas sampling. Plant physiological and growth parameters were measured as appropriate and meteorological records were kept. N2O flux was also continuously measured in a commercial corn field using the eddy covariance (EC) technique fitted with a fast response N2O analyzer to check the N2O emissions at the large scale and compare it to the chamber method. Results obtained with the EC technique were comparable with the chamber methods. Preliminary data indicate that N2O and CO2 fluxes were significantly influenced by the agricultural

  7. Electrochemical Evaluation of Lead Base Composite Anodes Fabricated by Accumulative Roll Bonding Technique

    NASA Astrophysics Data System (ADS)

    Karbasi, Maryam; Keshavarz Alamdari, Eskandar

    2015-04-01

    Accumulative roll bonding is used for the first time in lead systems to fabricate advanced lead base composite anodes. For this purpose, Ag as the most common and effective additive, Co as the best metallic immiscible substitution for Ag, and MnO2 as the ceramic and electrocatalytic agent have been used as additives to produce anodes. The accumulative roll bonding processed sheets have been fabricated under determined conditions. The electrochemical properties of the prepared samples are investigated by Electrochemical Impedance Spectroscopy, Cyclic Voltammetry, Polarization tests, electrowinning tests, and Scanning Electron Microscopy. The results indicate that the ARB-processed composite lead sheets can be perfectly used as novel developed anodes. The advantages include 5.51 times increase of current density, in the Pb-pct0.5Ag 9-pass sample compared to pure lead anode, decreased charge transfer resistance from 56.31 (Ω cm2) in pure lead anode to 17.5 (Ω cm2) in the Pb-pct2MnO2 8-pass sample (72 pct lower), and decreased oxygen evolution potential from 1.95 (V/SHE) in pure lead anode to 1.77 (V/SHE) in the Pb-pct2MnO2 8-pass sample (0.18 (V/SHE) lower). Electrowinning tests results reveal Pb-2 pctMnO2 8-pass showed best anodic performance withsignificant lower compared corrosion rate (75 pct), product and electrolyte contamination, slime formation, energy consumption and higher Zn deposit and energy conservation (to 294 kWh/t-Zn). Finest Zn deposit morphology (effective reduced grain size corresponding to smoothness and compaction) has been supplied by Pb-2 pctMnO2 8-pass sample resulted from enhanced growth rate of Zn in lack of Pb contaminations that could act as suitable nucleation sites.

  8. Automated eddy current analysis of materials

    NASA Technical Reports Server (NTRS)

    Workman, Gary L.

    1991-01-01

    The use of eddy current techniques for characterizing flaws in graphite-based filament-wound cylindrical structures is described. A major emphasis was also placed upon incorporating artificial intelligence techniques into the signal analysis portion of the inspection process. Developing an eddy current scanning system using a commercial robot for inspecting graphite structures (and others) was a goal in the overall concept and is essential for the final implementation for the expert systems interpretation. Manual scans, as performed in the preliminary work here, do not provide sufficiently reproducible eddy current signatures to be easily built into a real time expert system. The expert systems approach to eddy current signal analysis requires that a suitable knowledge base exist in which correct decisions as to the nature of a flaw can be performed. A robotic workcell using eddy current transducers for the inspection of carbon filament materials with improved sensitivity was developed. Improved coupling efficiencies achieved with the E-probes and horseshoe probes are exceptional for graphite fibers. The eddy current supervisory system and expert system was partially developed on a MacIvory system. Continued utilization of finite element models for predetermining eddy current signals was shown to be useful in this work, both for understanding how electromagnetic fields interact with graphite fibers, and also for use in determining how to develop the knowledge base. Sufficient data was taken to indicate that the E-probe and the horseshoe probe can be useful eddy current transducers for inspecting graphite fiber components. The lacking component at this time is a large enough probe to have sensitivity in both the far and near field of a thick graphite epoxy component.

  9. Stationary mesoscale eddies, upgradient eddy fluxes, and the anisotropy of eddy diffusivity

    NASA Astrophysics Data System (ADS)

    Lu, Jianhua; Wang, Fuchang; Liu, Hailong; Lin, Pengfei

    2016-01-01

    The mesoscale eddies of which parameterization is needed in coarse-resolution ocean models include not only the transient eddies akin to baroclinic instability but also the stationary eddies associated with topography. By applying a modified Lorenz-type decomposition to the eddy-permitting Southern Ocean State Estimate, we show that the stationary mesoscale eddies contribute a significant part to the total eddy kinetic energy, eddy enstrophy, and the total eddy-induced isopycnal thickness and potential vorticity fluxes. We find that beneath middepth (about 1000 m) the upgradient eddy fluxes, or so-called "negative" eddy diffusivities, are mainly attributed to the stationary mesoscale eddies, whereas the remaining transient eddy diffusivity is positive, for which the Gent and McWilliams (1990) parameterization scheme applies well. A quantitative method of measuring the anisotropy of eddy diffusivity is presented. The effect of stationary mesoscale eddies is one of major sources responsible for the anisotropy of eddy diffusivity. We suggest that an independent parameterization scheme for stationary mesoscale eddies may be needed for coarse-resolution ocean models, although the transient eddies remain the predominant part of mesoscale eddies in the oceans.

  10. Nonlinear optimisation techniques for accelerator performance improvement on-line: recent trials and experiment for the CERN antiproton accumulator

    NASA Astrophysics Data System (ADS)

    Chohan, Vinod

    1986-06-01

    The use of function minimisation techniques for optimum design according to given performance criteria is well-known. Given a well-defined criterion and a means of evaluating it precisely, the problem reduces to choosing the best optimisation procedure to suit the problem. Direct search techniques which do not generally rely on the computation of derivatives of the error function are ideal for on-line improvement of the global accelerator performance since the error function is not known analytically, e.g. the number of antiprotons stored in the antiproton accumulator ring on a pulse-to-pulse basis as a function of all the antiproton production and stochastic cooling system parameters. The user-friendliness of the NODAL interpreter at the man-machine interaction level, its capability to easily control and manipulate equipment as well as its capability to synchronise with respect to time events on a cycle-to-cycle basis makes it suitable for an on-line accelerator performance optimisation type of application. A modular procedure, based on the Simplex technique [1] has been implemented recently which allows function minimisation depending on the error function definition module. This enables an easy manipulation of variables and synchronization with machine events. For the antiproton accumulator (AA), while the circulating beam current transformer lacks the resolution to measure the exact number of antiprotons stored on a pulse-to-pulse basis, there are a large number of electrons produced in the production process [2] and a signal emanating from these can be adapted to provide the performance criterion and appropriate parameters used as function variables in the optimisation process. First trials based on optimisation of injection of antiprotons in the AA look promising, but further work is necessary in the direct definition of the error functions.

  11. The eddy cannon

    NASA Astrophysics Data System (ADS)

    Pichevin, Thierry; Nof, Doron

    1996-09-01

    A new nonlinear mechanism for the generation of "Meddies" by a cape is proposed. The essence of the new process is that the flow-force associated with any steady current that curves back on itself around a cape cannot be balanced without generating and shedding eddies. The process is modeled as follows. A westward flowing density current advances along a zonal wall and turns eastward after reaching the edge of the wall (i.e. the Cape of St Vincent). Integration of the steady (and inviscid) momentum equation along the wall gives the long-shore flow-force and shows that, no matter what the details of the turning process are, such a scenario is impossible. It corresponds to an unbalanced flow-force and, therefore, cannot exist. Namely, in an analogy to a rocket, the zonal longshore current forces the entire system to the west. A flow field that can compensate for such a force is westward drifting eddies that push the system to the east. In a similar fashion to the backward push associated with a firing cannon, the westward moving eddies (bullets) balance the integrated momentum of the flow around the cape. Nonlinear solutions are constructed analytically using an approach that enables one to compute the eddies' size and generation frequency without solving for the incredibly complicated details of the generation process itself. The method takes advantage of the fact that, after each eddy is generated, the system returns to its original structure. It is based on the integration of the momentum equation (for periodic flows) over a control volume and a perturbation expansion in ɛ, the ratio between the eddies' westward drift and the parent current speed. It is found that, because of the relatively small size of the Mediterranean eddies, β is not a sufficiently strong mechanism to remove the eddies (from the Cape of St Vincent) at the observed frequency. It is, therefore, concluded that westward advection must also take place. Specifically, it is found that an advection

  12. On "spurious" eddies

    SciTech Connect

    Drikakis, D.; Margolin, L. G.; Smolarkiewicz, P. K.

    2001-01-01

    Recently several papers have appeared in the CFD literature, proposing an idealized instability problem as a benchmark for discriminating among numerical algorithms for two-dimensional Navier-Stokes flows. The problem is a double shear layer simulated at coarse resolution and with a prescribed interface perturbation. A variety of second-order accurate schemes have been tested, with all results falling into one of two solution patterns - one pattern with two eddies and the other with three eddies. In the literature, there is no fast-and-firm rule to predict the results of any particular algorithm. However it is asserted that the two-eddy solution is correct. Our own research has led to two conclusions. First, the appearance of the third eddy is tied up with small details of the truncation error; we illustrate this point by prescribing small changes that lead to reversal of the appearance/disappearance of the third eddy in several schemes. Second, we discuss the realizability of the two solutions and suggest that the three-eddy solution is the more physical. Overall, we conclude that this problem is a poor choice of benchmark to discriminate among numerical algorithms.

  13. Revolving Eddy-Current Probe Detects Cracks Near Rivets

    NASA Technical Reports Server (NTRS)

    Namkung, Min; Wincheski, Buzz; Fulton, James P.; Nath, Shridhar; Simpson, John

    1995-01-01

    Scanning eddy-current probe in circular pattern increases sensitivity with which probe indicates fatigue cracks and other defects in metal surfaces in vicinity of rivets. Technique devised to facilitate inspection of riveted joints in aircraft. Eddy-current probe in question described in "Electro-magnetic Flaw Detector Is Easier To Use" (LAR-15046).

  14. Transient eddy current flow metering

    NASA Astrophysics Data System (ADS)

    Forbriger, J.; Stefani, F.

    2015-10-01

    Measuring local velocities or entire flow rates in liquid metals or semiconductor melts is a notorious problem in many industrial applications, including metal casting and silicon crystal growth. We present a new variant of an old technique which relies on the continuous tracking of a flow-advected transient eddy current that is induced by a pulsed external magnetic field. This calibration-free method is validated by applying it to the velocity of a spinning disk made of aluminum. First tests at a rig with a flow of liquid GaInSn are also presented.

  15. Automated eddy current analysis of materials

    NASA Technical Reports Server (NTRS)

    Workman, Gary L.

    1990-01-01

    This research effort focused on the use of eddy current techniques for characterizing flaws in graphite-based filament-wound cylindrical structures. A major emphasis was on incorporating artificial intelligence techniques into the signal analysis portion of the inspection process. Developing an eddy current scanning system using a commercial robot for inspecting graphite structures (and others) has been a goal in the overall concept and is essential for the final implementation for expert system interpretation. Manual scans, as performed in the preliminary work here, do not provide sufficiently reproducible eddy current signatures to be easily built into a real time expert system. The expert systems approach to eddy current signal analysis requires that a suitable knowledge base exist in which correct decisions as to the nature of the flaw can be performed. In eddy current or any other expert systems used to analyze signals in real time in a production environment, it is important to simplify computational procedures as much as possible. For that reason, we have chosen to use the measured resistance and reactance values for the preliminary aspects of this work. A simple computation, such as phase angle of the signal, is certainly within the real time processing capability of the computer system. In the work described here, there is a balance between physical measurements and finite element calculations of those measurements. The goal is to evolve into the most cost effective procedures for maintaining the correctness of the knowledge base.

  16. Mesoscale eddies are oases for higher trophic marine life.

    PubMed

    Godø, Olav R; Samuelsen, Annette; Macaulay, Gavin J; Patel, Ruben; Hjøllo, Solfrid Sætre; Horne, John; Kaartvedt, Stein; Johannessen, Johnny A

    2012-01-01

    Mesoscale eddies stimulate biological production in the ocean, but knowledge of energy transfers to higher trophic levels within eddies remains fragmented and not quantified. Increasing the knowledge base is constrained by the inability of traditional sampling methods to adequately sample biological processes at the spatio-temporal scales at which they occur. By combining satellite and acoustic observations over spatial scales of 10 s of km horizontally and 100 s of m vertically, supported by hydrographical and biological sampling we show that anticyclonic eddies shape distribution and density of marine life from the surface to bathyal depths. Fish feed along density structures of eddies, demonstrating that eddies catalyze energy transfer across trophic levels. Eddies create attractive pelagic habitats, analogous to oases in the desert, for higher trophic level aquatic organisms through enhanced 3-D motion that accumulates and redistributes biomass, contributing to overall bioproduction in the ocean. Integrating multidisciplinary observation methodologies promoted a new understanding of biophysical interaction in mesoscale eddies. Our findings emphasize the impact of eddies on the patchiness of biomass in the sea and demonstrate that they provide rich feeding habitat for higher trophic marine life.

  17. Mesoscale Eddies Are Oases for Higher Trophic Marine Life

    PubMed Central

    Godø, Olav R.; Samuelsen, Annette; Macaulay, Gavin J.; Patel, Ruben; Hjøllo, Solfrid Sætre; Horne, John; Kaartvedt, Stein; Johannessen, Johnny A.

    2012-01-01

    Mesoscale eddies stimulate biological production in the ocean, but knowledge of energy transfers to higher trophic levels within eddies remains fragmented and not quantified. Increasing the knowledge base is constrained by the inability of traditional sampling methods to adequately sample biological processes at the spatio-temporal scales at which they occur. By combining satellite and acoustic observations over spatial scales of 10 s of km horizontally and 100 s of m vertically, supported by hydrographical and biological sampling we show that anticyclonic eddies shape distribution and density of marine life from the surface to bathyal depths. Fish feed along density structures of eddies, demonstrating that eddies catalyze energy transfer across trophic levels. Eddies create attractive pelagic habitats, analogous to oases in the desert, for higher trophic level aquatic organisms through enhanced 3-D motion that accumulates and redistributes biomass, contributing to overall bioproduction in the ocean. Integrating multidisciplinary observation methodologies promoted a new understanding of biophysical interaction in mesoscale eddies. Our findings emphasize the impact of eddies on the patchiness of biomass in the sea and demonstrate that they provide rich feeding habitat for higher trophic marine life. PMID:22272294

  18. Localized Eddy Current Compensation Using Quantitative Field Mapping

    NASA Astrophysics Data System (ADS)

    Terpstra, M.; Andersen, P. M.; Gruetter, R.

    1998-03-01

    Eddy current effects induced by switched gradients in proximal conducting structures are traditionally reduced by applying preemphasis currents whose amplitudes and decay characteristics must be set to offset the eddy current fields. We present an expeditious, localized, and quantitative method for mapping and adjusting the parameters for eddy current compensation. Mapping is based on analysis of projections as used in the fast automatic shimming technique by mapping along projections (FASTMAP). Adjustment methods are demonstrated in high-field horizontal bore systems. The proposed localized eddy current mapping technique may also be used for localized measurements in situations where asymmetric conducting structures may cause nonlinear eddy current fields, such as in interventional MRI and open magnet designs.

  19. Homogeneous and inhomogeneous eddies

    SciTech Connect

    Pavia, E.G.

    1994-12-31

    This work deals with mesoscale warm oceanic eddies; i.e., self-contained bodies of water which transport heat, among other things, for several months and for several hundreds of kilometers. This heat transport is believed to play an important role in the atmospheric and oceanic conditions of the region where it is being transported. Here the author examines the difference in evolution between eddies modeled as blobs of homogeneous water and eddies in which density varies in the horizontal. Preliminary results suggest that instability is enhanced by inhomogeneities, which would imply that traditional modeling studies, based on homogeneous vortices have underestimated the rate of heat-release from oceanic eddies to the surroundings. The approach is modeling in the simplest form; i.e., one single active layer. Although previous studies have shown the drastic effect on stability brought by two or more dynamically-relevant homogeneous layers, the author believes the single-layer eddy-model has not been investigated thoroughly.

  20. Eddy current heating in magnetic refrigerators

    NASA Technical Reports Server (NTRS)

    Kittel, Peter

    1990-01-01

    Eddy current heating can be a significant source of parasitic heating in low temperature magnetic refrigerators. To study this problem a technique to approximate the heating due to eddy currents has been developed. A formula is presented for estimating the heating within a variety of shapes commonly found in magnetic refrigerators. These shapes include circular, square, and rectangular rods; cylindrical and split cylindrical shells; wire loops; and 'coil foil. One set of components evaluated are different types of thermal radiation shields. This comparison shows that a simple split shield is almost as effective (only 23 percent more heating) as using a shield, with the same axial thermal conductivity, made of 'coil foil'.

  1. Eddy Correlation Flux Measurement System (ECOR) Handbook

    SciTech Connect

    Cook, DR

    2011-01-31

    The eddy correlation (ECOR) flux measurement system provides in situ, half-hour measurements of the surface turbulent fluxes of momentum, sensible heat, latent heat, and carbon dioxide (CO2) (and methane at one Southern Great Plains extended facility (SGP EF) and the North Slope of Alaska Central Facility (NSA CF). The fluxes are obtained with the eddy covariance technique, which involves correlation of the vertical wind component with the horizontal wind component, the air temperature, the water vapor density, and the CO2 concentration.

  2. Comparative analysis of matter and energy fluxes determined by Bowen Ratio and Eddy Covariance techniques at a crop site in eastern Germany

    NASA Astrophysics Data System (ADS)

    Brust, K.; Hehn, M.; Bernhofer, C.

    2012-04-01

    The measurement of atmospheric fluxes is an important means to evaluate ecosystem exchanges. In 2009 and 2010, fluxes and gradients of heat, water vapour, and CO2 over winter barley and rapeseed were measured simultaneously at the Klingenberg cropland site in Germany. A Bowen Ratio (BR) system was employed alongside to an existing Eddy Covariance (EC) tower. The BR system is required to account for the longer response time of the chemiluminescence analysers measuring other trace gases, e.g. NOx. To test and evaluate the application of the NOx measurement setup, the two independent systems (BR/EC) are compared with respect to energy and CO2 fluxes. We show a regression and differences analysis, diurnal cycles of the obtained fluxes, and interpret their coherence to the growth stage of the crops. The regression analysis depicts that differences between the systems are largest for latent heat LE (BR detects apparently higher LE due to the forced closure of energy balance), whereby the matter fluxes of CO2 show fairly little differences. Both measurement systems are able to capture the fluctuations of fluxes adequately well. Additionally, a multiple linear regression revealed that differences between the obtained fluxes are not induced by atmospheric conditions. The results of the differences analysis for sensible and latent heat point out that the observed differences of fluxes between both systems are mainly due to deviations in the mean, while differences in variability and timing/shape are of smaller importance. The differences of CO2 fluxes between both measurement systems are particularly caused by deviations in timing and shape, which can be explained with the linear cross-correlation coefficient (R2=0.8). From the good results of the comparison of matter fluxes (CO2) we conclude that the use of the Bowen Ratio method is applicable to other matter fluxes (like NOx).

  3. The Tundra is a Net Source of CO2 Measured by Autochambers and Eddy Covariance Techniques During Five Years in a Site With Permafrost Thawing.

    NASA Astrophysics Data System (ADS)

    Celis, G.; Mauritz, M.; Bracho, R. G.; Salmon, V. G.; Webb, E.; Hutchings, J. A.; Natali, S.; Crummer, K. G.; Schuur, E.; Schaedel, C.

    2015-12-01

    Current and future warming of high latitude tundra ecosystems will play an important role in climate change through feedbacks to the global carbon (C) cycle. Long-term observational and experimental studies are pivotal for detecting and understanding changes in the coming decades. Yet studies of the C feedbacks from observational studies and manipulative experiments made on tundra plant communities often have significantly different conclusions with regards to impacts of warming on the ecosystem. Comparing results from these two study types, however, often involves integrating CO2 flux measurements that were collected on different spatial scales using a variety of methods. The process of data assimilation for landscape level analysis is often complicated by the fact that many projects only utilize one method for measuring CO2 fluxes at a given site. This study compares five years of C dynamics in a moist acidic tundra from control plots in a manipulative warming experiment (CiPEHR - plot-scale) and landscape-level natural permafrost thaw gradient (Gradient - Eddy covariance) observations all within a 1km distance from each other. We found net ecosystem exchange (NEE) to be an annual net source of carbon using both methods (Gradient 12.3 - 125.6 g CO2-C m-2 and CiPEHR warming manipulation 80.2 - 175.8 g CO2-C m-2). The differences between sites were biggest in the first three years of observation, and can be explained by lower growing season gross primary production (GPP - first three years) from the manipulation (CiPEHR), and lower ecosystem respiration (Reco) from CiPEHR in the first year only. Suppressed GPP and Reco could be from the impact of experimental setup (chamber soil collars - root damage), which lowered the plant community's capacity to fix C, but recovered within three years. This warrants caution of making generalization of short-term experiments in the tundra and more research is needed evaluating coupling of belowground and aboveground C dynamics.

  4. Eddy current damper

    NASA Technical Reports Server (NTRS)

    Ellis, R. C.; Fink, R. A.; Rich, R. W.

    1989-01-01

    A high torque capacity eddy current damper used as a rate limiting device for a large solar array deployment mechanism is discussed. The eddy current damper eliminates the problems associated with the outgassing or leaking of damping fluids. It also provides performance advantages such as damping torque rates, which are truly linear with respect to input speed, continuous 360 degree operation in both directions of rotation, wide operating temperature range, and the capability of convenient adjustment of damping rates by the user without disassembly or special tools.

  5. Effects of Eddy Viscosity on Time Correlations in Large Eddy Simulation

    NASA Technical Reports Server (NTRS)

    He, Guowei; Rubinstein, R.; Wang, Lian-Ping; Bushnell, Dennis M. (Technical Monitor)

    2001-01-01

    Subgrid-scale (SGS) models for large. eddy simulation (LES) have generally been evaluated by their ability to predict single-time statistics of turbulent flows such as kinetic energy and Reynolds stresses. Recent application- of large eddy simulation to the evaluation of sound sources in turbulent flows, a problem in which time, correlations determine the frequency distribution of acoustic radiation, suggest that subgrid models should also be evaluated by their ability to predict time correlations in turbulent flows. This paper compares the two-point, two-time Eulerian velocity correlation evaluated from direct numerical simulation (DNS) with that evaluated from LES, using a spectral eddy viscosity, for isotropic homogeneous turbulence. It is found that the LES fields are too coherent, in the sense that their time correlations decay more slowly than the corresponding time. correlations in the DNS fields. This observation is confirmed by theoretical estimates of time correlations using the Taylor expansion technique. Tile reason for the slower decay is that the eddy viscosity does not include the random backscatter, which decorrelates fluid motion at large scales. An effective eddy viscosity associated with time correlations is formulated, to which the eddy viscosity associated with energy transfer is a leading order approximation.

  6. Pulsed eddy current testing. [nondestructive tests of the external tank

    NASA Technical Reports Server (NTRS)

    Workman, G. L.

    1980-01-01

    Since a large number of the procedures used for inspecting the external tank are concerned with determining flaws in welds, there is a need to develop an inspection technique, which can be automated, to determine flaws in welds and structures with complex geometries. Techniques whereby an eddy current is generated in a metallic material and the changes in the circuit parameters due to material differences are observed, were chosen as one possible approach. Pulsed eddy current and its relationship to multifrequency techniques is discussed as well as some preliminary results obtained from observing pulsed waveforms with apparatus and algorithms currently in use for ultrasonic testing of welds. It can be shown the pulsed eddy current techniques can provide similar results, can eliminate some of the noncritical parameters affecting the eddy current signals, and can facilitate in the detection of critical parameter such as flaws, subsurface voids, and corrosion.

  7. Eddy Covariance Flux Measurements of Urban Aerosols During the MILAGRO Mexico City Field Campaign

    NASA Astrophysics Data System (ADS)

    Grivicke, R.; Pressley, S.; Jimenez, J.; Nemitz, E.; Alexander, L.; Velasco, E.; Allwine, E.; Jobson, T.; Westberg, H.; Ramos, R.; Molina, L.; Lamb, B.

    2007-12-01

    Expansive urban development in the fast growing number of megacities around the world raises concerns regarding the pollution levels in such sites. The Mexico City MILAGRO 2006 (Megacity Initiative: Local and Global Research Observations) field campaign was a worldwide initiative aiming to understand sources, chemical nature and evolution of pollution in one of the largest urban developments. As part of the MILAGRO campaign, urban fluxes of aerosols and related trace gases were measured near the centre of Mexico City at 42 m above street level. Aerosol concentrations (1 min. averages) and aerosol fluxes (10 Hz, selected ion monitoring) were measured with an Aerodyne quadrupole aerosol mass spectrometer operated in an alternating 30 minute mode of ambient concentrations and fluxes. The fluxes were derived using eddy covariance calculations. The aerosol flux data were supported by additional flux measurements of CO2 and a number of gas phase VOC species using a combination of techniques, including Proton Transfer Reaction Mass Spectrometry using a disjunct eddy covariance technique and GC-FID analysis of samples from a disjunct eddy accumulation sampler. Preliminary results of aerosol concentrations and flux measurements indicate that the urban landscape is a significant source of organic aerosols.

  8. Don Eddy; "Jewelry."

    ERIC Educational Resources Information Center

    Schaefer, Claire

    1989-01-01

    Presents a lesson that introduces students in grades K-three to sources of design inspiration in contemporary urban settings. Using Don Eddy's painting of a jewelry store window display, asks students to describe and analyze the interplay of shape, pattern, and color. Suggests studio activities, including an activity in which students build a…

  9. Eddies off Tasmania

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This true-color satellite image shows a large phytoplankton bloom, several hundred square kilometers in size, in the Indian Ocean off the west coast of Tasmania. In this scene, the rich concentration of microscopic marine plants gives the water a lighter, more turquoise appearance which helps to highlight the current patterns there. Notice the eddies, or vortices in the water, that can be seen in several places. It is possible that these eddies were formed by converging ocean currents flowing around Tasmania, or by fresh river runoff from the island, or both. Often, eddies in the sea serve as a means for stirring the water, thus providing nutrients that help support phytoplankton blooms, which in turn provide nutrition for other organisms. Effectively, these eddies help feed the sea (click to read an article on this topic). This image was acquired November 7, 2000, by the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) flying aboard the Orbview-2 satellite. Tasmania is located off Australia's southeastern coast. Image courtesy SeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE

  10. Influence of mesoscale anticyclonic eddies on zooplankton distribution south of the western Aleutian Islands during summer

    NASA Astrophysics Data System (ADS)

    Saito, R.; Yamaguchi, A.; Yasuda, I.; Ueno, H.; Ishiyama, H.; Imai, I.

    2013-12-01

    Mesoscale anticyclonic eddies have been observed south of the Aleutian Islands located between the Bering Sea and the subarctic Pacific. Eddies farther east, in the Gulf of Alaska, are known to transport coastal water and coastal zooplankton to offshore open ocean. The impacts of mesoscale anticyclonic eddies formed south of the western Aleutian Islands (Aleutian eddies) on the zooplankton community are not fully understood. In the present study, we describe zooplankton population structures within an Aleutian eddy and outside the eddy during July 2010. Our field study was conducted at seven stations along 51°15‧N from 171°21‧E to 174°38‧E (western line) and at four stations along 50°40‧N from 176°24‧E to 178°44‧E (eastern line) on 7-8 July 2010. At each station, environmental data (temperature, salinity and fluorescence were measured by CTD/XCTD. Zooplankton samples were collected by vertical tow of 150 m depth to the surface using 100 μm mesh size plankton net. Based on the sea level anomaly (SLA), the western line crossed an anticyclonic eddy but the eastern line did not cross the eddy (Fig. 1). This Aleutian eddy was formed south of Attu Island (52°54‧N, 172°54‧E) in mid-February 2010, and it moved southeastward in the next five months. The SLA near the eddy center, representing the strength of the eddy, continuously increased, and the area oscillated at one to two month periods overlain on a general increase from ~7,000 to ~18,000 km2. Large oceanic copepods, Neocalanus cristatus, Eucalanus bungii and Metridia pacifica were more abundant inside the eddy than the outside. Inside the eddy, the life stage distribution of N. cristatus was advanced than that outside, and Neocalanus spp. had accumulated more lipids. These conditions probably reflect the greater primary production in the eddy, production enhanced by nutrients advected into the eddy. Since the Aleutian eddy was formed in offshore waters and/or eddy-eddy interaction occurred

  11. Recent peat accumulation rates in minerotrophic peatlands of the Bay James region, Eastern Canada, inferred by 210Pb and 137Cs radiometric techniques.

    PubMed

    Ali, Adam A; Ghaleb, Bassam; Garneau, Michelle; Asnong, Hans; Loisel, Julie

    2008-10-01

    (210)Pb and (137)Cs dating techniques are used to characterise recent peat accumulation rates of two minerotrophic peatlands located in the La Grande Rivière hydrological watershed, in the James Bay region (Canada). Several cores were collected during the summer 2005 in different parts of the two selected peatlands. These minerotrophic patterned peatlands are presently affected by erosion processes, expressed by progressive mechanical destruction of their pools borders. This erosion process is related to a water table rise induced by a regional increase of humidity since the last century. The main objective of the present paper is to (1) evaluate if (210)Pb and (137)Cs dating techniques can be applied to build accurate chronologies in these environments and (2) detect changes in the peat accumulation rates in regard to this amplification of humidity. In both sites, unsupported (210)Pb shows an exponential decreasing according to the depth. Chronologies inferred from (210)Pb allow to reconstruct peat accumulation rates since ca. 1855 AD. The (137)Cs data displayed evident mobility and diffusion, preventing the establishment of any sustained chronology based on these measurements. In the two sites, peat accumulation rates inferred from (210)Pb chronologies fluctuate between 0.005 and 0.038 g cm(-2) yr(-1). As a result, the rise of the water table during the last decade has not yet affected peat accumulation rates.

  12. Investigations of eddy coherence in jet flows

    NASA Technical Reports Server (NTRS)

    Yule, A. J.

    1980-01-01

    In turbulent shear flow the term coherent structures refers to eddies which are both spatially coherent, i.e., large eddies, aand also temporally coherent, i.e., they retain their identities for times which are long compared with their time scales in fixed point measurements. In transitional flows, the existence of such structures is evident from flow visualizations. In many other flows, such structures are not so evident. The reasons for the existence of these two classes of flows are discussed and attention is focused upon the more difficult flows, where coherent structures are not so evident. Techniques by which the existence (or nonexistence) of such structures in these flows can be established from point measurements, are also discussed. A major problem is shown to be the need to discriminate between real losses in eddy coherence and apparent losses in coherence introduced by phase scrambling effects which 'smear' multipoint correlations. The analysis of multiprobe time dependent data in cold and reacting round turbulent jets is described and it is shown how evidence of strong eddy coherence can be extracted from data.

  13. Eddy current pulsed phase thermography and feature extraction

    NASA Astrophysics Data System (ADS)

    He, Yunze; Tian, GuiYun; Pan, Mengchun; Chen, Dixiang

    2013-08-01

    This letter proposed an eddy current pulsed phase thermography technique combing eddy current excitation, infrared imaging, and phase analysis. One steel sample is selected as the material under test to avoid the influence of skin depth, which provides subsurface defects with different depths. The experimental results show that this proposed method can eliminate non-uniform heating and improve defect detectability. Several features are extracted from differential phase spectra and the preliminary linear relationships are built to measure these subsurface defects' depth.

  14. Potential of a New Technique for Remote Sensing of Hydrocarbon Accumulations and Blind Uranium Deposits: Buried Lif Thermoluminescence Dosimeters

    NASA Technical Reports Server (NTRS)

    Siegel, F. R.; Vaz, J. E.; Lindholm, R. C.

    1982-01-01

    Buried thermoluminescence dosimeters may be useful in remote sensing of petroleum and natural gas accumulations and blind uranium deposits. They act as integrating detectors that smooth out the effects of environmental variations that affect other measuring systems and result in irregularities and poor repeatability in measurements made during gas and radiometric surveys.

  15. Eddy current correction in volume-localized MR spectroscopy

    NASA Technical Reports Server (NTRS)

    Lin, C.; Wendt, R. E. 3rd; Evans, H. J.; Rowe, R. M.; Hedrick, T. D.; LeBlanc, A. D.

    1994-01-01

    The quality of volume-localized magnetic resonance spectroscopy is affected by eddy currents caused by gradient switching. Eddy currents can be reduced with improved gradient systems; however, it has been suggested that the distortion due to eddy currents can be compensated for during postprocessing with a single-frequency reference signal. The authors propose modifying current techniques for acquiring the single-frequency reference signal by using relaxation weighting to reduce interference from components that cannot be eliminated by digital filtering alone. Additional sequences with T1 or T2 weighting for reference signal acquisition are shown to have the same eddy current characteristics as the original signal without relaxation weighting. The authors also studied a new eddy current correction method that does not require a single-frequency reference signal. This method uses two free induction decays (FIDs) collected from the same volume with two sequences with opposite gradients. Phase errors caused by eddy currents are opposite in these two FIDs and can be canceled completely by combining the FIDs. These methods were tested in a phantom. Eddy current distortions were corrected, allowing quantitative measurement of structures such as the -CH = CH- component, which is otherwise undetectable.

  16. Accumulate repeat accumulate codes

    NASA Technical Reports Server (NTRS)

    Abbasfar, Aliazam; Divsalar, Dariush; Yao, Kung

    2004-01-01

    In this paper we propose an innovative channel coding scheme called 'Accumulate Repeat Accumulate codes' (ARA). This class of codes can be viewed as serial turbo-like codes, or as a subclass of Low Density Parity Check (LDPC) codes, thus belief propagation can be used for iterative decoding of ARA codes on a graph. The structure of encoder for this class can be viewed as precoded Repeat Accumulate (RA) code or as precoded Irregular Repeat Accumulate (IRA) code, where simply an accumulator is chosen as a precoder. Thus ARA codes have simple, and very fast encoder structure when they representing LDPC codes. Based on density evolution for LDPC codes through some examples for ARA codes, we show that for maximum variable node degree 5 a minimum bit SNR as low as 0.08 dB from channel capacity for rate 1/2 can be achieved as the block size goes to infinity. Thus based on fixed low maximum variable node degree, its threshold outperforms not only the RA and IRA codes but also the best known LDPC codes with the dame maximum node degree. Furthermore by puncturing the accumulators any desired high rate codes close to code rate 1 can be obtained with thresholds that stay close to the channel capacity thresholds uniformly. Iterative decoding simulation results are provided. The ARA codes also have projected graph or protograph representation that allows for high speed decoder implementation.

  17. Are Eddy Covariance series stationary?

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Spectral analysis via a discrete Fourier transform is used often to examine eddy covariance series for cycles (eddies) of interest. Generally the analysis is performed on hourly or half-hourly data sets collected at 10 or 20 Hz. Each original series is often assumed to be stationary. Also automated ...

  18. Remote field eddy current-crack and defect detection

    SciTech Connect

    Lord, W.

    1989-03-16

    No single nondestructive evaluation (NDE) technique is currently capable of detecting and characterizing all the defect types that can occur in gas pipeline. Conventional in-line inspection tools for example, have not shown significant sensitivity to intergranular stress corrosion cracking. For this reason considerable research and development work is still needed in order to provide the in-line inspection tools whose results are essential for structural integrity evaluations. The remote field eddy current method shows more promise than conventional eddy current methods, in gas pipeline inspection, due to the increased sensitivity to inner and outer pipe wall inhomogeneities. Even though the fundamental physical principles governing the conventional eddy current method and the remote field eddy current method is one and the same (that of electromagnetic induction), the differences in operating frequencies in the two methods result in field patterns that have different characteristic properties, such as extremely small skin depths associated with conventional eddy currents testing and the phenomena of potential valley'' and phase knot'' associated with remote field eddy current technique. 20 refs., 26 figs.

  19. Chemical speciation of arsenic-accumulating mineral in a sedimentary iron deposit by synchrotron radiation multiple X-ray analytical techniques.

    PubMed

    Endo, Satoshi; Terada, Yasuko; Kato, Yasuhiro; Nakai, Izumi

    2008-10-01

    The comprehensive characterization of As(V)-bearing iron minerals from the Gunma iron deposit, which were probably formed by biomineralization, was carried out by utilizing multiple synchrotron radiation (SR)-based analytical techniques at BL37XU at SPring-8. SR microbeam X-ray fluorescence (SR-mu-XRF) imaging showed a high level of arsenic accumulation in the iron ore as dots of ca. 20 microm. Based on SEM observations and SR X-ray powder diffraction (SR-XRD) analysis, it was found that arsenic is selectively accumulated in strengite (FePO4 x 2H2O) with a concentric morphology, which may be produced by a biologically induced process. Furthermore, the X-ray absorption fine structure (XAFS) analysis showed that arsenic in strengite exists in the arsenate (AsO4(3-)) form and is coordinated by four oxygen atoms at 1.68 angstroms. The results suggest that strengite accumulates arsenic by isomorphous substitution of AsO4(3-) for PO4(3-) to form a partial solid-solution of strengite and scorodite (FeAsO4 x 2H2O). The specific correlation between the distribution of As and biominerals indicates that microorganisms seems to play an important role in the mineralization of strengite in combination with an arsenic-accumulating process.

  20. Eddy current detection of pitting corrosion around fastener holes

    NASA Astrophysics Data System (ADS)

    Heida, J. H.; Thart, W. G. J.

    1995-01-01

    An evaluation of the eddy current technique for the detection and depth assessment of corrosion around fastener holes in F-16 lower wing skins is described. The corrosion type in this structure is pitting corrosion at the countersink edge of the fastener holes. Due to a corrosion clean-up limit of only 1.5 - 2.5 percent, a maximum thickness reduction in the range of 0.08 - 0.32 mm is allowed (depending on local skin thickness). This specifies the needed sensitivity for in-service corrosion inspection. In the evaluation use was made of specimens cut out of the F-16 lower wing skin structure. In total twelve specimens were exposed to an accelerated corrosion test (EXCO-test). Eddy current inspection of the specimens with installed fasteners was performed with a standard eddy scope and four different eddy current probes. After the eddy current inspection cross-sections of the twelve-specimens were made to determine the extent of pitting corrosion at the countersink edges. After evaluation of the inspection results the following conclusions can be drawn: for in-service detection of countersink edge corrosion standard visual inspection is the preferred technique regarding the simplicity, sensitivity and reliability of inspection; and for the purpose of depth assessment the eddy current technique is capable of detecting countersink edge corrosion with a depth from about 0.1 mm. Due to the corrosion clean-up limit of only 1.5 - 2.5 percent (0.08 - 0.32 mm), however, the eddy current technique is considered not applicable for in-service depth assessment of countersink edge corrosion in F-16 lower wing skins.

  1. Characteristic eddy decomposition of turbulence in a channel

    NASA Technical Reports Server (NTRS)

    Moin, Parviz; Moser, Robert D.

    1991-01-01

    The proper orthogonal decomposition technique (Lumley's decomposition) is applied to the turbulent flow in a channel to extract coherent structures by decomposing the velocity field into characteristic eddies with random coefficients. In the homogeneous spatial directions, a generaliztion of the shot-noise expansion is used to determine the characteristic eddies. In this expansion, the Fourier coefficients of the characteristic eddy cannot be obtained from the second-order statistics. Three different techniques are used to determine the phases of these coefficients. They are based on: (1) the bispectrum, (2) a spatial compactness requirement, and (3) a functional continuity argument. Results from these three techniques are found to be similar in most respects. The implications of these techniques and the shot-noise expansion are discussed. The dominant eddy is found to contribute as much as 76 percent to the turbulent kinetic energy. In both 2D and 3D, the characteristic eddies consist of an ejection region straddled by streamwise vortices that leave the wall in the very short streamwise distance of about 100 wall units.

  2. Turbulent eddy diffusivity and mean eddy lifetimes measured in spray combustion

    NASA Technical Reports Server (NTRS)

    Driscoll, J. F.; Pelaccio, D. G.

    1980-01-01

    A quantitative description of the eddy structure that occurs in turbulent combustion processes can be obtained by the use of laser velocimetry, as shown in this work. The mean eddy length scales, eddy lifetimes, and turbulent diffusivity have been determined in a spray combustion flame for the first time. Velocity data was obtained at various locations within the flame, and standard correlation techniques were modified and then applied to reduce the data. In order to assess how the spray burns, the measured eddy lifetimes were compared with the relevant reaction times and drop lifetimes. Conditions that are conducive to group combustion of the droplets, rather than individual droplet combustion, were found to exist in the upstream region of the spray. Local measurements of the hydrocarbon concentration also support the conclusion that the majority of droplets undergo group combustion. However, the data indicate that some of the larger drops can survive the initial burning region and form a dilute spray downstream where conditions favor individual droplet combustion.

  3. A comparison of winter mercury accumulation at forested and no-canopy sites measured with different snow sampling techniques

    USGS Publications Warehouse

    Nelson, S.J.; Johnson, K.B.; Weathers, K.C.; Loftin, C.S.; Fernandez, I.J.; Kahl, J.S.; Krabbenhoft, D.P.

    2008-01-01

    Atmospheric mercury (Hg) is delivered to ecosystems via rain, snow, cloud/fog, and dry deposition. The importance of snow, especially snow that has passed through the forest canopy (throughfall), in delivering Hg to terrestrial ecosystems has received little attention in the literature. The snowpack is a dynamic system that links atmospheric deposition and ecosystem cycling through deposition and emission of deposited Hg. To examine the magnitude of Hg delivery via snowfall, and to illuminate processes affecting Hg flux to catchments during winter (cold season), Hg in snow in no-canopy areas and under forest canopies measured with four collection methods were compared: (1) Hg in wet precipitation as measured by the Mercury Deposition Network (MDN) for the site in Acadia National Park, Maine, USA, (2) event throughfall (collected after snowfall cessation for accumulations of >8 cm), (3) season-long throughfall collected using the same apparatus for event sampling but deployed for the entire cold season, and (4) snowpack sampling. Estimates (mean ?? SE) of Hg deposition using these methods during the 91-day cold season in 2004-2005 at conifer sites showed that season-long throughfall Hg flux (1.80 ??g/m2) < snowpack Hg (2.38 ?? 0.68 ??g/m2) < event throughfall flux (5.63 ?? 0.38 ??g/m2). Mercury deposition at the MDN site (0.91 ??g/m2) was similar to that measured at other no-canopy sites in the area using the other methods, but was 3.4 times less than was measured under conifer canopies using the event sampling regime. This indicates that snow accumulated under the forest canopy received Hg from the overstory or exhibited less re-emission of Hg deposited in snow relative to open areas. The soil surface of field-scale plots were sprayed with a natural rain water sample that contained an Hg tracer (202Hg) just prior to the first snowfall to explore whether some snowpack Hg might be explained from soil emissions. The appearance of the 202Hg tracer in the snowpack (0

  4. Method and apparatus for correcting eddy current signal voltage for temperature effects

    DOEpatents

    Kustra, Thomas A.; Caffarel, Alfred J.

    1990-01-01

    An apparatus and method for measuring physical characteristics of an electrically conductive material by the use of eddy-current techniques and compensating measurement errors caused by changes in temperature includes a switching arrangement connected between primary and reference coils of an eddy-current probe which allows the probe to be selectively connected between an eddy current output oscilloscope and a digital ohm-meter for measuring the resistances of the primary and reference coils substantially at the time of eddy current measurement. In this way, changes in resistance due to temperature effects can be completely taken into account in determining the true error in the eddy current measurement. The true error can consequently be converted into an equivalent eddy current measurement correction.

  5. Windmill driven eddy current heater

    SciTech Connect

    Birgel, W. J.; Hajec, C. S.

    1983-12-20

    A windmill electric heater converts wind energy to heat energy. A windmill drives a rotor of an eddy current heater. Magnetic fields are provided at an air gap between the rotor and a stator of the eddy current heater. Rotation of the rotor with respect to the stator causes eddy currents, and therefore heat, to be generated in the rotor. The heat generated in the rotor is drawn off for beneficial use such as in heating a house or other building. Excitation of the magnetic fields (and therefore the amount of heat generated) is controlled as a function of sensed parameters such as wind velocity, ambient temperature of the surroundings to be heated and temperature of the eddy current heater.

  6. Eddy-Current Reference Standard

    NASA Technical Reports Server (NTRS)

    Ambrose, H. H., Jr.

    1985-01-01

    Magnetic properties of metallic reference standards duplicated and stabilized for eddy-current coil measurements over long times. Concept uses precisely machined notched samples of known annealed materials as reference standards.

  7. Lagrangian analysis of formation, structure, evolution and splitting of anticyclonic Kuril eddies

    NASA Astrophysics Data System (ADS)

    Prants, S. V.; Lobanov, V. B.; Budyansky, M. V.; Uleysky, M. Yu.

    2016-03-01

    We studied in detail a mesoscale anticylonic eddy that has been sampled in the R/V Professor Gagarinskiy cruise (June-July 2012) in the area east of the Kuril Islands in the northwestern subarctic Pacific. Lagrangian approach was applied to study formation, structure and evolution of this feature called the eddy A and of its parent eddy B using a simulation with synthetic tracers advected by the AVISO velocity field. We used different Lagrangian methods and techniques to identify those eddies and their boundaries, to know their structure and to document their deformation, metamorphoses and splitting. It has been found that the eddy A was born as a result of splitting of the eddy B with the core water to be borrowed from the eddy B which, in turn, was influenced by the Okhotsk Sea water flowing into the ocean through the Kuril straits. The periphery of the eddy A was formed mainly by East Kamchatka Current water in the process of its winding onto the eddy A core by portions. All these processes have been documented in detail with the help of drift and tracking Lagrangian maps computed forward and backward in time with a large number of synthetic tracers distributed over the studied area. We have found a Lagrangian structure of those eddies and the ways how they have gained and released water. Simulated and measured locations of the center of the eddy A and its boundary have been be estimated to coincide with the accuracy of ≈ 7-10 and ≈ 15-20 km, respectively. Our simulations were validated in part by tracks of available surface drifters and Argo floats. We presented CTD hydrographic observations of the Kuril eddy A from the surface to deep waters and compared observed and simulated results in order to establish origin and properties of water masses constituting that eddy.

  8. Electrical Resistance as a NDE Technique to Monitor Processing and Damage Accumulation in SiC/SiC Composites

    NASA Technical Reports Server (NTRS)

    Smith, Craig; Morscher, Gregory N.; Xia, Zhenhai

    2008-01-01

    Ceramic matrix composites are suitable for high temperature structural applications such as turbine airfoils and hypersonic thermal protection systems. The employment of these materials in such applications is limited by the ability to process components reliable and to accurately monitor and predict damage evolution that leads to failure under stressed-oxidation conditions. Current nondestructive methods such as ultrasound, x-ray, and thermal imaging are limited in their ability to quantify small scale, transverse, in-plane, matrix cracks developed over long-time creep and fatigue conditions. Electrical resistance of SiC/SiC composites is one technique that shows special promise towards this end. Since both the matrix and the fibers are conductive, changes in matrix or fiber properties should relate to changes in electrical conductivity along the length of a specimen or part. Initial efforts to quantify the electrical resistance of different fiber and different matrix SiC/SiC composites will be presented. Also, the effect of matrix cracking on electrical resistivity for several composite systems will be presented. The implications towards electrical resistance as a technique applied to composite processing, damage detection, and life-modeling will be discussed.

  9. NONDESTRUCTIVE EDDY CURRENT TESTING

    DOEpatents

    Renken, C.J. Jr.

    1961-05-23

    An eddy current testing device is described for measuring metal continuity independent of probe-to-sample spacing. An inductance would test probe is made a leg of a variable impedance bridge and the bridge is balanced with the probe away from the sample. An a-c signal is applied across the input terminals of the bridge circuit. As the probe is brought into proximity with the metal sample, the resulting impedance change in the probe gives an output signal from the bridge whose phase angle is proportional to the sample continuity and amplitude is proportional to the probe-tosample spacing. The output signal from the bridge is applied to a compensating network where, responsive to amplitude changes from the bridge output signal, a constant phased voltage output is maintained when the sample is continuous regardless of probe-to-sample spacing. A phase meter calibrated to read changes in resistivity of the metal sample measures the phase shift between the output of the compensating network and the original a-c signal applied to the bridge.

  10. Eddy current pulsed thermography for fatigue evaluation of gear

    NASA Astrophysics Data System (ADS)

    Tian, Gui Yun; Yin, Aijun; Gao, Bin; Zhang, Jishan; Shaw, Brian

    2014-02-01

    The pulsed eddy current (PEC) technique generates responses over a wide range of frequencies, containing more spectral coverage than traditional eddy current inspection. Eddy current pulsed thermography (ECPT), a newly developed non-destructive testing (NDT) technique, has advantages such as rapid inspection of a large area within a short time, high spatial resolution, high sensitivity and stand-off measurement distance. This paper investigates ECPT for the evaluation of gear fatigue tests. The paper proposes a statistical method based on single channel blind source separation to extract details of gear fatigue. The discussion of transient thermal distribution and patterns of fatigue contact surfaces as well as the non-contact surfaces have been reported. In addition, the measurement for gears with different cycles of fatigue tests by ECPTand the comparison results between ECPT with magnetic Barkhausen noise (MBN) have been evaluated. The comparison shows the competitive capability of ECPT in fatigue evaluation.

  11. Wind-driven freshwater buildup and release in the Beaufort Gyre constrained by mesoscale eddies

    NASA Astrophysics Data System (ADS)

    Manucharyan, Georgy E.; Spall, Michael A.

    2016-01-01

    Recently, the Beaufort Gyre has accumulated over 20,000 km3 of freshwater in response to strong anticyclonic atmospheric winds that have prevailed over the gyre for almost two decades. Here we explore key physical processes affecting the accumulation and release of freshwater within an idealized eddy-resolving model of the Beaufort Gyre. We demonstrate that a realistic halocline can be achieved when its deepening tendency due to Ekman pumping is counteracted by the cumulative action of mesoscale eddies. Based on this balance, we derive analytical scalings for the depth of the halocline and its spin-up time scale and emphasize their explicit dependence on eddy dynamics. Our study further suggests that the Beaufort Gyre is currently in a state of high sensitivity to atmospheric winds. However, an intensification of surface stress would inevitably lead to a saturation of the freshwater content—a constraint inherently set by the intricacies of the mesoscale eddy dynamics.

  12. Eddy Diffusivities for Sensible Heat, Ozone and Momentum from Eddy Correlation and Gradient Measurements.

    NASA Astrophysics Data System (ADS)

    Zeller, Karl Frederick

    Micrometeorological field measurements of the fluxes and the gradients of momentum, sensible heat and ozone are presented and discussed. The eddy-correlation measurement technique was used to obtain the flux data at the heights of three and eight meters. A method to accurately measure mass (ozone) gradients from surface -layer based meteorological towers was developed and used. Both flux and gradient measurements are used for the determination of eddy diffusivities. Exploratory analyses were made with the data to investigate similarity relationships between the eddy diffusivities of momentum K_{ rm m}, sensible heat K_ {rm h}, and mass K_ {rm c}, where ozone was used as the mass tracer. Eddy-diffusivity ratios were computed using dimensionless -gradient ratios classified from the data and from regression models. These ratios were classified by atmospheric stability determined at the geometric mean of the measurement heights. The assumption of similarity between the eddy diffusivities of ozone and sensible heat, K_ {rm c} = K_{ rm h}, based on scalar turbulent transfer theory, was verified for unstable atmospheric conditions. The results for eddy diffusivities of sensible heat and ozone for stable atmospheric conditions however, show that diffusivities of sensible heat are 50% greater than diffusivities of ozone. Chemical reaction of ozone, and/or the need for flux-measurement corrections, decrease the resulting values for ozone diffusivities during stable periods. Established eddy-diffusivity ratios for water vapor and momentum are valid for ozone and momentum under stable-atmospheric conditions over smooth-terrain but not under unstable conditions for flow disturbed by irregular terrain. The relationships between the eddy diffusivities of momentum and the eddy diffusivities of ozone, as well as those between momentum and sensible heat are controlled by free-convection conditions, K_{ rm m} < K_ {rm c} and K_{ rm m} < K_ {rm h}; these results are inconclusive for

  13. Remote field eddy current detection of stress-corrosion cracks

    SciTech Connect

    Nestleroth, J.B.

    1990-02-01

    The feasibility of detecting stress-corrosion cracks (SSC) using the Remote Field Eddy Current (RFEC) technique was demonstrated. The RFEC technique interrogates the entire thickness of the pipe and is applicable for in-line inspection. If it can be shown that the RFEC technique is effective in detecting SSC, then the technique is an ideal method for detecting the defects of interest. A defect detection model is proposed for explaining the mechanism for crack detection. For axially oriented, closed cracks, such as SCC, the conventional defect detection model proved to be too simplistic and not applicable. Therefore, a new detection mode that examines the flow of circumferential eddy currents was developed based on experimental results. This model, though not rigorous, provides a general understanding of the applicability of the RFEC technique for finding SSC. The data from the cracks and various artificial defects is presented in three formats: isometric projections, pseudocolor images and line-of-sight data. Though only two cracks were found, the experimental results correlate well with the circumferential eddy current theory. A theoretical analysis of the effects of motion on the output signal of the receiver is presented. This analysis indicates that inspection speed of simple implementations may be limited to a few miles per hour. Remote field eddy current inspection has excellent potential for inspection of gas transmission lines for detecting stress corrosion cracks that should be further developed.

  14. Giant Magnetoresistance Sensors: A Review on Structures and Non-Destructive Eddy Current Testing Applications.

    PubMed

    Rifai, Damhuji; Abdalla, Ahmed N; Ali, Kharudin; Razali, Ramdan

    2016-02-26

    Non-destructive eddy current testing (ECT) is widely used to examine structural defects in ferromagnetic pipe in the oil and gas industry. Implementation of giant magnetoresistance (GMR) sensors as magnetic field sensors to detect the changes of magnetic field continuity have increased the sensitivity of eddy current techniques in detecting the material defect profile. However, not many researchers have described in detail the structure and issues of GMR sensors and their application in eddy current techniques for nondestructive testing. This paper will describe the implementation of GMR sensors in non-destructive testing eddy current testing. The first part of this paper will describe the structure and principles of GMR sensors. The second part outlines the principles and types of eddy current testing probe that have been studied and developed by previous researchers. The influence of various parameters on the GMR measurement and a factor affecting in eddy current testing will be described in detail in the third part of this paper. Finally, this paper will discuss the limitations of coil probe and compensation techniques that researchers have applied in eddy current testing probes. A comprehensive review of previous studies on the application of GMR sensors in non-destructive eddy current testing also be given at the end of this paper.

  15. Giant Magnetoresistance Sensors: A Review on Structures and Non-Destructive Eddy Current Testing Applications

    PubMed Central

    Rifai, Damhuji; Abdalla, Ahmed N.; Ali, Kharudin; Razali, Ramdan

    2016-01-01

    Non-destructive eddy current testing (ECT) is widely used to examine structural defects in ferromagnetic pipe in the oil and gas industry. Implementation of giant magnetoresistance (GMR) sensors as magnetic field sensors to detect the changes of magnetic field continuity have increased the sensitivity of eddy current techniques in detecting the material defect profile. However, not many researchers have described in detail the structure and issues of GMR sensors and their application in eddy current techniques for nondestructive testing. This paper will describe the implementation of GMR sensors in non-destructive testing eddy current testing. The first part of this paper will describe the structure and principles of GMR sensors. The second part outlines the principles and types of eddy current testing probe that have been studied and developed by previous researchers. The influence of various parameters on the GMR measurement and a factor affecting in eddy current testing will be described in detail in the third part of this paper. Finally, this paper will discuss the limitations of coil probe and compensation techniques that researchers have applied in eddy current testing probes. A comprehensive review of previous studies on the application of GMR sensors in non-destructive eddy current testing also be given at the end of this paper. PMID:26927123

  16. Giant Magnetoresistance Sensors: A Review on Structures and Non-Destructive Eddy Current Testing Applications.

    PubMed

    Rifai, Damhuji; Abdalla, Ahmed N; Ali, Kharudin; Razali, Ramdan

    2016-01-01

    Non-destructive eddy current testing (ECT) is widely used to examine structural defects in ferromagnetic pipe in the oil and gas industry. Implementation of giant magnetoresistance (GMR) sensors as magnetic field sensors to detect the changes of magnetic field continuity have increased the sensitivity of eddy current techniques in detecting the material defect profile. However, not many researchers have described in detail the structure and issues of GMR sensors and their application in eddy current techniques for nondestructive testing. This paper will describe the implementation of GMR sensors in non-destructive testing eddy current testing. The first part of this paper will describe the structure and principles of GMR sensors. The second part outlines the principles and types of eddy current testing probe that have been studied and developed by previous researchers. The influence of various parameters on the GMR measurement and a factor affecting in eddy current testing will be described in detail in the third part of this paper. Finally, this paper will discuss the limitations of coil probe and compensation techniques that researchers have applied in eddy current testing probes. A comprehensive review of previous studies on the application of GMR sensors in non-destructive eddy current testing also be given at the end of this paper. PMID:26927123

  17. A new eddy-covariance method using empirical mode decomposition

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We introduce a new eddy-covariance method that uses a spectral decomposition algorithm called empirical mode decomposition. The technique is able to calculate contributions to near-surface fluxes from different periodic components. Unlike traditional Fourier methods, this method allows for non-ortho...

  18. Accumulate-Repeat-Accumulate-Accumulate-Codes

    NASA Technical Reports Server (NTRS)

    Divsalar, Dariush; Dolinar, Sam; Thorpe, Jeremy

    2004-01-01

    Inspired by recently proposed Accumulate-Repeat-Accumulate (ARA) codes [15], in this paper we propose a channel coding scheme called Accumulate-Repeat-Accumulate-Accumulate (ARAA) codes. These codes can be seen as serial turbo-like codes or as a subclass of Low Density Parity Check (LDPC) codes, and they have a projected graph or protograph representation; this allows for a high-speed iterative decoder implementation using belief propagation. An ARAA code can be viewed as a precoded Repeat-and-Accumulate (RA) code with puncturing in concatenation with another accumulator, where simply an accumulator is chosen as the precoder; thus ARAA codes have a very fast encoder structure. Using density evolution on their associated protographs, we find examples of rate-lJ2 ARAA codes with maximum variable node degree 4 for which a minimum bit-SNR as low as 0.21 dB from the channel capacity limit can be achieved as the block size goes to infinity. Such a low threshold cannot be achieved by RA or Irregular RA (IRA) or unstructured irregular LDPC codes with the same constraint on the maximum variable node degree. Furthermore by puncturing the accumulators we can construct families of higher rate ARAA codes with thresholds that stay close to their respective channel capacity thresholds uniformly. Iterative decoding simulation results show comparable performance with the best-known LDPC codes but with very low error floor even at moderate block sizes.

  19. Large-Eddy Simulation of Flow Through an Array of Cubes with Local Grid Refinement

    NASA Astrophysics Data System (ADS)

    Goodfriend, Elijah; Katopodes Chow, Fotini; Vanella, Marcos; Balaras, Elias

    2016-05-01

    High resolution simulations of the transport of urban contaminants are important for disaster response and city planning. Large-eddy simulation (LES) and mesh refinement can each be used to decrease the computational cost of modelling, but combining these techniques can result in additional errors at grid-refinement interfaces. Here, we study the effect of the turbulence closure on the accuracy of LES results, for grids with mesh refinement, in a test case of flow through a periodic array of cubes. It is found that a mixed-model turbulence closure, using both an eddy viscosity and a scale similarity component, reduces energy accumulation at grid-refinement interfaces when used with explicit filtering of the advection term. The mixed model must be used with explicit filtering to control high wavenumber errors generated by the non-linear scale-similarity model. The results demonstrate that the turbulence closure mitigates errors associated with using LES on block-structured grids for urban-flow simulations.

  20. Ultrastructure of blood and lymphatic vascular networks in three-dimensional cultured tissues fabricated by extracellular matrix nanofilm-based cell accumulation technique.

    PubMed

    Asano, Yoshiya; Nishiguchi, Akihiro; Matsusaki, Michiya; Okano, Daisuke; Saito, Erina; Akashi, Mitsuru; Shimoda, Hiroshi

    2014-06-01

    Cell accumulation technique is an extracellular matrix (ECM) nanofilm-based tissue-constructing method that enables formation of multilayered hybrid culture tissues. In this method, ECM-nanofilm is constructed using layer-by-layer assembly of fibronectin and gelatin on culture cells. The ECM-nanofilm promotes cell-to-cell interaction; then the three-dimensional (3D) multilayered tissue can be constructed with morphological change of the cells mimicking living tissues. By using this method, we have successfully produced tubular networks of human umbilical venous endothelial cells (HUVECs) and human dermal lymphatic endothelial cells (HDLECs) in 3D multilayered normal human dermal fibroblasts (NHDFs). This study demonstrated morphological characteristics of the vascular networks in the engineered tissues by using light and electron microscopy. In light microscopy, HUVECs and HDLECs formed luminal structures such as native blood and lymphatic capillaries, respectively. Electron microscopy showed distinct ultrastructural aspects of the vasculature of HUVECs or HDLECs with intermediated NHDFs and abundant ECM. The vasculature constructed by HUVECs exhibited structures similar to native blood capillaries, involving overlapping endothelial connections with adherens junctions, abundant vesicles in the endothelial cells and basement membrane-like structure. The detection of laminin around HUVEC-constructed vessels supported the presence of perivascular basal lamina. The vasculature constructed by HDLECs showed some ultrastructural characteristics similar to those of native lymphatic capillaries such as irregular vascular shape, loose adhesive connection and gap formation between endothelial cells. In conclusion, our novel vascular network models fabricated by the cell accumulation technique provide highly organized blood and lymphatic capillary networks mimicking the vasculatures in vivo.

  1. Eddy correlation measurements of submarine groundwater discharge

    USGS Publications Warehouse

    Crusius, J.; Berg, P.; Koopmans, D.J.; Erban, L.

    2008-01-01

    This paper presents a new, non-invasive means of quantifying groundwater discharge into marine waters using an eddy correlation approach. The method takes advantage of the fact that, in virtually all aquatic environments, the dominant mode of vertical transport near the sediment-water interface is turbulent mixing. The technique thus relies on measuring simultaneously the fluctuating vertical velocity using an acoustic Doppler velocimeter and the fluctuating salinity and/or temperature using rapid-response conductivity and/or temperature sensors. The measurements are typically done at a height of 5-15??cm above the sediment surface, at a frequency of 16 to 64??Hz, and for a period of 15 to 60??min. If the groundwater salinity and/or temperature differ from that of the water column, the groundwater specific discharge (cm d- 1) can be quantified from either a heat or salt balance. Groundwater discharge was estimated with this new approach in Salt Pond, a small estuary on Cape Cod (MA, USA). Estimates agreed well with previous estimates of discharge measured using seepage meters and 222Rn as a tracer. The eddy correlation technique has several desirable characteristics: 1) discharge is quantified under in-situ hydrodynamic conditions; 2) salinity and temperature can serve as two semi-independent tracers of discharge; 3) discharge can be quantified at high temporal resolution, and 4) long-term records of discharge may be possible, due to the low power requirements of the instrumentation. ?? 2007 Elsevier B.V. All rights reserved.

  2. Development of eddy current microscopy for high resolution electrical conductivity imaging using atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Nalladega, V.; Sathish, S.; Jata, K. V.; Blodgett, M. P.

    2008-07-01

    We present a high resolution electrical conductivity imaging technique based on the principles of eddy current and atomic force microscopy (AFM). An electromagnetic coil is used to generate eddy currents in an electrically conducting material. The eddy currents generated in the conducting sample are detected and measured with a magnetic tip attached to a flexible cantilever of an AFM. The eddy current generation and its interaction with the magnetic tip cantilever are theoretically modeled using monopole approximation. The model is used to estimate the eddy current force between the magnetic tip and the electrically conducting sample. The theoretical model is also used to choose a magnetic tip-cantilever system with appropriate magnetic field and spring constant to facilitate the design of a high resolution electrical conductivity imaging system. The force between the tip and the sample due to eddy currents is measured as a function of the separation distance and compared to the model in a single crystal copper. Images of electrical conductivity variations in a polycrystalline dual phase titanium alloy (Ti-6Al-4V) sample are obtained by scanning the magnetic tip-cantilever held at a standoff distance from the sample surface. The contrast in the image is explained based on the electrical conductivity and eddy current force between the magnetic tip and the sample. The spatial resolution of the eddy current imaging system is determined by imaging carbon nanofibers in a polymer matrix. The advantages, limitations, and applications of the technique are discussed.

  3. Accumulate-Repeat-Accumulate-Accumulate Codes

    NASA Technical Reports Server (NTRS)

    Divsalar, Dariush; Dolinar, Samuel; Thorpe, Jeremy

    2007-01-01

    Accumulate-repeat-accumulate-accumulate (ARAA) codes have been proposed, inspired by the recently proposed accumulate-repeat-accumulate (ARA) codes. These are error-correcting codes suitable for use in a variety of wireless data-communication systems that include noisy channels. ARAA codes can be regarded as serial turbolike codes or as a subclass of low-density parity-check (LDPC) codes, and, like ARA codes they have projected graph or protograph representations; these characteristics make it possible to design high-speed iterative decoders that utilize belief-propagation algorithms. The objective in proposing ARAA codes as a subclass of ARA codes was to enhance the error-floor performance of ARA codes while maintaining simple encoding structures and low maximum variable node degree.

  4. Physical interpretation and separation of eddy current pulsed thermography

    NASA Astrophysics Data System (ADS)

    Yin, Aijun; Gao, Bin; Yun Tian, Gui; Woo, W. L.; Li, Kongjing

    2013-02-01

    Eddy current pulsed thermography (ECPT) applies induction heating and a thermal camera for non-destructive testing and evaluation (NDT&E). Because of the variation in resultant surface heat distribution, the physical mechanism that corresponds to the general behavior of ECPT can be divided into an accumulation of Joule heating via eddy current and heat diffusion. However, throughout the literature, the heating mechanisms of ECPT are not given in detail in the above two thermal phenomena and they are difficult to be separated. Nevertheless, once these two physical parameters are separated, they can be directly used to detect anomalies and predict the variation in material properties such as electrical conductivity, magnetic permeability and microstructure. This paper reports physical interpretation of these two physical phenomena that can be found in different time responses given the ECPT image sequences. Based on the phenomenon and their behaviors, the paper proposes a statistical method based on single channel blind source separation to decompose the two physical phenomena using different stages of eddy current and thermal propagation from the ECPT images. Links between mathematical models and physical models have been discussed and verified. This fundamental understanding of transient eddy current distribution and heating propagation can be applied to the development of feature extraction and pattern recognition for the quantitative analysis of ECPT measurement images and defect characterization.

  5. Eddy current array probe for corrosion mapping on ageing aircraft

    NASA Astrophysics Data System (ADS)

    Leclerc, Rémi; Samson, Rock

    2000-05-01

    The life of an airplane in the civil and military fleet is expanding by many years. The corrosion on aircraft is becoming a serious problem. The corrosion can also lead to the development of "multi-site damage" (MSD) and catastrophic failure. The need for a fast and reliable nondestructive technique for the detection of corrosion is a prime concern. A simple eddy current or ultrasonic probe can be very time consuming in the inspection because of the small area covered by the probe. The use of an eddy current array probe can cut the time use for an inspection or increase the surface scanned. Because it is an eddy current technology, the surface preparation is minimal compared to other techniques like ultrasound. It is also possible to detect defects beyond the first layer in a multiple layer panel. A flexible probe was employed to demonstrate the capacities of an eddy current array probe. This flexible probe can also match the profile of the structure to inspect limiting the lift-off. The C-scan technique is used in the display to see all the data on the same screen. The interpretation is also simplified.

  6. Dynamic Model of Mesoscale Eddies

    NASA Astrophysics Data System (ADS)

    Dubovikov, Mikhail S.

    2003-04-01

    Oceanic mesoscale eddies which are analogs of well known synoptic eddies (cyclones and anticyclones), are studied on the basis of the turbulence model originated by Dubovikov (Dubovikov, M.S., "Dynamical model of turbulent eddies", Int. J. Mod. Phys.B7, 4631-4645 (1993).) and further developed by Canuto and Dubovikov (Canuto, V.M. and Dubovikov, M.S., "A dynamical model for turbulence: I. General formalism", Phys. Fluids8, 571-586 (1996a) (CD96a); Canuto, V.M. and Dubovikov, M.S., "A dynamical model for turbulence: II. Sheardriven flows", Phys. Fluids8, 587-598 (1996b) (CD96b); Canuto, V.M., Dubovikov, M.S., Cheng, Y. and Dienstfrey, A., "A dynamical model for turbulence: III. Numerical results", Phys. Fluids8, 599-613 (1996c)(CD96c); Canuto, V.M., Dubovikov, M.S. and Dienstfrey, A., "A dynamical model for turbulence: IV. Buoyancy-driven flows", Phys. Fluids9, 2118-2131 (1997a) (CD97a); Canuto, V.M. and Dubovikov, M.S., "A dynamical model for turbulence: V. The effect of rotation", Phys. Fluids9, 2132-2140 (1997b) (CD97b); Canuto, V.M., Dubovikov, M.S. and Wielaard, D.J., "A dynamical model for turbulence: VI. Two dimensional turbulence", Phys. Fluids9, 2141-2147 (1997c) (CD97c); Canuto, V.M. and Dubovikov, M.S., "Physical regimes and dimensional structure of rotating turbulence", Phys. Rev. Lett. 78, 666-669 (1997d) (CD97d); Canuto, V.M., Dubovikov, M.S. and Dienstfrey, A., "Turbulent convection in a spectral model", Phys. Rev. Lett. 78, 662-665 (1997e) (CD97e); Canuto, V.M. and Dubovikov, M.S., "A new approach to turbulence", Int. J. Mod. Phys.12, 3121-3152 (1997f) (CD97f); Canuto, V.M. and Dubovikov, M.S., "Two scaling regimes for rotating Raleigh-Benard convection", Phys. Rev. Letters78, 281-284, (1998) (CD98); Canuto, V.M. and Dubovikov, M.S., "A dynamical model for turbulence: VII. The five invariants for shear driven flows", Phys. Fluids11, 659-664 (1999a) (CD99a); Canuto, V.M., Dubovikov, M.S. and Yu, G., "A dynamical model for turbulence: VIII. IR and UV

  7. Use of eddy current mixes to solve a weld examination application

    SciTech Connect

    Ward, R.C.; LaBoissonniere, A.

    1995-12-31

    The augmentation of typical nondestructive (i.e., ultrasound) weld inspection techniques by the use of eddy current tools may significantly enhance the quality and reliability of weld inspections. One recent example is the development of an eddy current technique for use in the examination of BWR core shroud welds, where multi-frequency mixes are used to eliminate signals coming from the weld material so that the examination of the heat affected zone is enhanced. An analysis tool most commonly associated with ultrasound examinations, the C-Scan based on gated information, may be implemented with eddy current data to enhance analysis.

  8. Biogeochemical characteristics of a long-lived anticyclonic eddy in the eastern South Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Cornejo D'Ottone, Marcela; Bravo, Luis; Ramos, Marcel; Pizarro, Oscar; Karstensen, Johannes; Gallegos, Mauricio; Correa-Ramirez, Marco; Silva, Nelson; Farias, Laura; Karp-Boss, Lee

    2016-05-01

    Mesoscale eddies are important, frequent, and persistent features of the circulation in the eastern South Pacific (ESP) Ocean, transporting physical, chemical and biological properties from the productive shelves to the open ocean. Some of these eddies exhibit subsurface hypoxic or suboxic conditions and may serve as important hotspots for nitrogen loss, but little is known about oxygen consumption rates and nitrogen transformation processes associated with these eddies. In the austral fall of 2011, during the Tara Oceans expedition, an intrathermocline, anticyclonic, mesoscale eddy with a suboxic (< 2 µmol kg-1 of O2), subsurface layer (200-400 m) was detected ˜ 900 km off the Chilean shore (30° S, 81° W). The core of the eddy's suboxic layer had a temperature-salinity signature characteristic of Equatorial Subsurface Water (ESSW) that at this latitude is normally restricted to an area near the coast. Measurements of nitrogen species within the eddy revealed undersaturation (below 44 %) of nitrous oxide (N2O) and nitrite accumulation (> 0.5 µM), suggesting that active denitrification occurred in this water mass. Using satellite altimetry, we were able to track the eddy back to its region of formation on the coast of central Chile (36.1° S, 74.6° W). Field studies conducted in Chilean shelf waters close to the time of eddy formation provided estimates of initial O2 and N2O concentrations of the ESSW source water in the eddy. By the time of its offshore sighting, concentrations of both O2 and N2O in the subsurface oxygen minimum zone (OMZ) of the eddy were lower than concentrations in surrounding water and "source water" on the shelf, indicating that these chemical species were consumed as the eddy moved offshore. Estimates of apparent oxygen utilization rates at the OMZ of the eddy ranged from 0.29 to 44 nmol L-1 d-1 and the rate of N2O consumption was 3.92 nmol L-1 d-1. These results show that mesoscale eddies affect open-ocean biogeochemistry in the ESP

  9. Expert system for analyzing eddy current measurements

    DOEpatents

    Levy, Arthur J.; Oppenlander, Jane E.; Brudnoy, David M.; Englund, James M.; Loomis, Kent C.

    1994-01-01

    A method and apparatus (called DODGER) analyzes eddy current data for heat exchanger tubes or any other metallic object. DODGER uses an expert system to analyze eddy current data by reasoning with uncertainty and pattern recognition. The expert system permits DODGER to analyze eddy current data intelligently, and obviate operator uncertainty by analyzing the data in a uniform and consistent manner.

  10. Eddy current thickness measurement apparatus

    DOEpatents

    Rosen, Gary J.; Sinclair, Frank; Soskov, Alexander; Buff, James S.

    2015-06-16

    A sheet of a material is disposed in a melt of the material. The sheet is formed using a cooling plate in one instance. An exciting coil and sensing coil are positioned downstream of the cooling plate. The exciting coil and sensing coil use eddy currents to determine a thickness of the solid sheet on top of the melt.

  11. From Phenomena to Objects: Segmentation of Fuzzy Objects and its Application to Oceanic Eddies

    NASA Astrophysics Data System (ADS)

    Wu, Qingling

    A challenging image analysis problem that has received limited attention to date is the isolation of fuzzy objects---i.e. those with inherently indeterminate boundaries---from continuous field data. This dissertation seeks to bridge the gap between, on the one hand, the recognized need for Object-Based Image Analysis of fuzzy remotely sensed features, and on the other, the optimization of existing image segmentation techniques for the extraction of more discretely bounded features. Using mesoscale oceanic eddies as a case study of a fuzzy object class evident in Sea Surface Height Anomaly (SSHA) imagery, the dissertation demonstrates firstly, that the widely used region-growing and watershed segmentation techniques can be optimized and made comparable in the absence of ground truth data using the principle of parsimony. However, they both have significant shortcomings, with the region growing procedure creating contour polygons that do not follow the shape of eddies while the watershed technique frequently subdivides eddies or groups together separate eddy objects. Secondly, it was determined that these problems can be remedied by using a novel Non-Euclidian Voronoi (NEV) tessellation technique. NEV is effective in isolating the extrema associated with eddies in SSHA data while using a non-Euclidian cost-distance based procedure (based on cumulative gradients in ocean height) to define the boundaries between fuzzy objects. Using this procedure as the first stage in isolating candidate eddy objects, a novel "region-shrinking" multicriteria eddy identification algorithm was developed that includes consideration of shape and vorticity. Eddies identified by this region-shrinking technique compare favorably with those identified by existing techniques, while simplifying and improving existing automated eddy detection algorithms. However, it also tends to find a larger number of eddies as a result of its ability to separate what other techniques identify as connected

  12. Deep, cross-equatorial eddies

    NASA Astrophysics Data System (ADS)

    Borisov, Sergey; Nof, Doron

    The question of how deep ocean eddies can cross the equator is addressed with the aid of analytical and numerical models. We focus on the possibility that deep ocean (lens-like) eddies can cross the equator via deep cross equatorial channels on the ocean floor. We first examine the behavior of solid balls (i.e., free particles) in a meridional parabolic channel on a plane. Such balls are subject to similar topographical forcing and inertial forces that a lens is subject to, except that pressure forces and friction are absent. We examine both single isolated balls and a "cloud" of (noninteractive) balls. In general, the balls' trajectories have a chaotic character; a fraction of the cloud crosses the equator and ends up in the northern hemisphere, and a fraction is left behind. More realistic numerical experiments (with a fully nonlinear reduced-gravity isopycnic model of the Bleck and Boudra type) show similar behavior. In all cases the equator acts as an "eddy smasher" in the sense that it breaks the lens into at least two parts, one crosses the equator and ends up in the northern hemisphere, and the other is left behind. Here, however, the system is not chaotic. Despite the obvious differences between clouds of balls and eddies, there is a remarkable similarity between the percentage of balls that penetrate into the opposite hemisphere and the percentage of eddies' mass that ends up in the other hemisphere. This suggests that the geometry of the channel and the presence of the equator determine how the fluid will be partitioned among the two hemispheres.

  13. Pulsed eddy current thickness measurements of transuranic waste containers

    SciTech Connect

    O`Brien, T.K.; Kunerth, D.C.

    1995-12-31

    Thickness measurements on fifty five gallon waste drums for drum integrity purposes have been traditionally performed at the INEL using ultrasonic testing methods. Ultrasonic methods provide high resolution repeatable thickness measurements in a timely manner, however, the major drawback of using ultrasonic techniques is coupling to the drum. Areas with severe exterior corrosion, debonded paper labels or any other obstacle in the acoustic path will have to be omitted from the ultrasonic scan. We have developed a pulsed eddy current scanning system that can take thickness measurements on fifty five gallon carbon steel drums with wall thicknesses up to 65 mils. This type of measurement is not susceptible to the problems mentioned above. Eddy current measurements in the past have excluded ferromagnetic materials such as carbon steel because of the difficulty in penetrating the material and in compensating for changes in permeability from material to material. New developments in data acquisition electronics as well as advances in personal computers have made a pulsed eddy current system practical and inexpensive. Certain aspects of the pulsed eddy current technique as well as the operation of such a system and features such as real time pass/fail thresholds for overpacking identification and full scan data archiving for future evaluation will be discussed.

  14. A new technique for unbiased external ion accumulation in a quadrupole two-dimensional ion trap for electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry.

    PubMed

    Belov, M E; Nikolaev, E N; Alving, K; Smith, R D

    2001-01-01

    External ion accumulation in a two-dimensional (2D) multipole trap has been shown to increase the sensitivity, dynamic range and duty cycle of a Fourier transform ion cyclotron resonance (FTICR) mass spectrometer. However, it is important that trapped ions be detected without significant bias at longer accumulation times in the external 2D multipole trap. With increasing ion accumulation time pronounced m/z discrimination was observed when trapping ions in an accumulation quadrupole. In this work we show that superimposing lower rf-amplitude dipolar excitation over the main rf-field in the accumulation quadrupole results in disruption of the m/z discrimination and can potentially be used to achieve unbiased external ion accumulation with FTICR.

  15. electromagnetics, eddy current, computer codes

    2002-03-12

    TORO Version 4 is designed for finite element analysis of steady, transient and time-harmonic, multi-dimensional, quasi-static problems in electromagnetics. The code allows simulation of electrostatic fields, steady current flows, magnetostatics and eddy current problems in plane or axisymmetric, two-dimensional geometries. TORO is easily coupled to heat conduction and solid mechanics codes to allow multi-physics simulations to be performed.

  16. Large eddy simulation applications in gas turbines.

    PubMed

    Menzies, Kevin

    2009-07-28

    The gas turbine presents significant challenges to any computational fluid dynamics techniques. The combination of a wide range of flow phenomena with complex geometry is difficult to model in the context of Reynolds-averaged Navier-Stokes (RANS) solvers. We review the potential for large eddy simulation (LES) in modelling the flow in the different components of the gas turbine during a practical engineering design cycle. We show that while LES has demonstrated considerable promise for reliable prediction of many flows in the engine that are difficult for RANS it is not a panacea and considerable application challenges remain. However, for many flows, especially those dominated by shear layer mixing such as in combustion chambers and exhausts, LES has demonstrated a clear superiority over RANS for moderately complex geometries although at significantly higher cost which will remain an issue in making the calculations relevant within the design cycle. PMID:19531505

  17. Development of an ultralow frequency eddy current instrument for the detection and sizing of stress corrosion cracks

    SciTech Connect

    Hayford, D.T.

    1988-01-01

    This book describes an investigation of the potential to use remote field eddy currents at low frequencies that would permit penetration of pipeline steels and use this technique to detect stress corrosion cracking on coated pipelines without requiring coating to be removed. The report describes development of a prototype eddy current instrument.

  18. Eddy Covariance Measurements of the Sea-Spray Aerosol Flu

    NASA Astrophysics Data System (ADS)

    Brooks, I. M.; Norris, S. J.; Yelland, M. J.; Pascal, R. W.; Prytherch, J.

    2015-12-01

    Historically, almost all estimates of the sea-spray aerosol source flux have been inferred through various indirect methods. Direct estimates via eddy covariance have been attempted by only a handful of studies, most of which measured only the total number flux, or achieved rather coarse size segregation. Applying eddy covariance to the measurement of sea-spray fluxes is challenging: most instrumentation must be located in a laboratory space requiring long sample lines to an inlet collocated with a sonic anemometer; however, larger particles are easily lost to the walls of the sample line. Marine particle concentrations are generally low, requiring a high sample volume to achieve adequate statistics. The highly hygroscopic nature of sea salt means particles change size rapidly with fluctuations in relative humidity; this introduces an apparent bias in flux measurements if particles are sized at ambient humidity. The Compact Lightweight Aerosol Spectrometer Probe (CLASP) was developed specifically to make high rate measurements of aerosol size distributions for use in eddy covariance measurements, and the instrument and data processing and analysis techniques have been refined over the course of several projects. Here we will review some of the issues and limitations related to making eddy covariance measurements of the sea spray source flux over the open ocean, summarise some key results from the last decade, and present new results from a 3-year long ship-based measurement campaign as part of the WAGES project. Finally we will consider requirements for future progress.

  19. Efficacy of distortion correction on diffusion imaging: comparison of FSL eddy and eddy_correct using 30 and 60 directions diffusion encoding.

    PubMed

    Yamada, Haruyasu; Abe, Osamu; Shizukuishi, Takashi; Kikuta, Junko; Shinozaki, Takahiro; Dezawa, Ko; Nagano, Akira; Matsuda, Masayuki; Haradome, Hiroki; Imamura, Yoshiki

    2014-01-01

    Diffusion imaging is a unique noninvasive tool to detect brain white matter trajectory and integrity in vivo. However, this technique suffers from spatial distortion and signal pileup or dropout originating from local susceptibility gradients and eddy currents. Although there are several methods to mitigate these problems, most techniques can be applicable either to susceptibility or eddy-current induced distortion alone with a few exceptions. The present study compared the correction efficiency of FSL tools, "eddy_correct" and the combination of "eddy" and "topup" in terms of diffusion-derived fractional anisotropy (FA). The brain diffusion images were acquired from 10 healthy subjects using 30 and 60 directions encoding schemes based on the electrostatic repulsive forces. For the 30 directions encoding, 2 sets of diffusion images were acquired with the same parameters, except for the phase-encode blips which had opposing polarities along the anteroposterior direction. For the 60 directions encoding, non-diffusion-weighted and diffusion-weighted images were obtained with forward phase-encoding blips and non-diffusion-weighted images with the same parameter, except for the phase-encode blips, which had opposing polarities. FA images without and with distortion correction were compared in a voxel-wise manner with tract-based spatial statistics. We showed that images corrected with eddy and topup possessed higher FA values than images uncorrected and corrected with eddy_correct with trilinear (FSL default setting) or spline interpolation in most white matter skeletons, using both encoding schemes. Furthermore, the 60 directions encoding scheme was superior as measured by increased FA values to the 30 directions encoding scheme, despite comparable acquisition time. This study supports the combination of eddy and topup as a superior correction tool in diffusion imaging rather than the eddy_correct tool, especially with trilinear interpolation, using 60 directions

  20. Transient Eddies in the UCLA GCM

    NASA Technical Reports Server (NTRS)

    White, G. H.

    1985-01-01

    The simulation of transient eddies in the nine level UCLA general circulation model (GCM) was examined and compared to observations, with emphasis on the Northern Hemisphere winter. Qualitatively, the UCLA GCM reproduces many features of the observed circulation and the relationship between the time mean flow and transient eddies; however, the magnitudes of transient eddies in the UCLA GCM, particularly at frequencies lower than those associated with baroclinic instability, appear to be much less than those observed. The pattern of low level transient eddy heat fluxes were similar to observations and acted to dissipate the low level seasonal mean temperature field. The simulated transient eddy kinetic energy at 300 mb is given for eddies of all time scales shorter than a season.

  1. EDDY CURRENT INVERSION AND ESTIMATION METRICS FOR EVALUATING THERMAL BARRIER COATINGS

    SciTech Connect

    Sabbagh, Harold A.; Murphy, R. Kim; Sabbagh, Elias H.; Knopp, Jeremy S.; Aldrin, John C.; Nyenhuis, John

    2010-02-22

    In this paper, sophisticated eddy-current techniques incorporating model-based inverse methods were successfully demonstrated to measure the thickness and remaining-life of high-temperature coatings. To further assure the performance of these inverse methods, several estimation metrics including Fisher Information, Cramer-Rao Lower Bound (CRLB), covariance, and singular value decomposition (SVD) are introduced. The connections and utility of these metrics are illustrated in the design of eddy current methods for estimating layer thickness, conductivity and probe liftoff.

  2. Evaluation and Improvement of Eddy Current Position Sensors in Magnetically Suspended Flywheel Systems

    NASA Technical Reports Server (NTRS)

    Dever, Timothy P.; Palazzolo, Alan B.; Thomas, Erwin M., III; Jansen, Ralph H.; McLallin, Kerry (Technical Monitor); Soeder, James (Technical Monitor)

    2001-01-01

    Eddy current position sensor performance is evaluated for use in a high-speed flywheel development system. The flywheel utilizes a five axis active magnetic bearing system. The eddy current sensors are used for position feedback for the bearing controller. Measured characteristics include sensitivity to multiple target materials and susceptibility to noise from the magnetic bearings and from sensor-to-sensor crosstalk. Improvements in axial sensor configuration and techniques for noise reduction are described.

  3. Observations of Three Dimensional Surfzone Eddies

    NASA Astrophysics Data System (ADS)

    Arnold, J. L.; Henderson, S. M.; Solovitz, S.

    2012-12-01

    We present measurements of the vertical structure of surfzone eddies (frequencies 0.0005-0.01 Hz). From 16 Oct to 07 Nov 2011, an array of 12 Acoustic Doppler Profilers (ADPs) measured velocity profiles in 0-6 m water depth on a natural beach near Duck, North Carolina. We will analyze and describe vertical variations in eddy velocity. Vertical variability of eddy magnitude will be presented, as well as coherence and phase between near-surface and near-bed velocities. We aim to shed light on the causes and consequences of vertical eddy variability, which has recently been recognized in observations, but is not yet well understood.

  4. Eddy current system for inspection of train hollow axles

    SciTech Connect

    Chady, Tomasz; Psuj, Grzegorz; Sikora, Ryszard; Kowalczyk, Jacek; Spychalski, Ireneusz

    2014-02-18

    The structural integrity of wheelsets used in rolling stock is of great importance to the safety. In this paper, electromagnetic system with an eddy current transducer suitable for the inspection of hollow axles have been presented. The transducer was developed to detect surface braking defects having depth not smaller than 0.5 mm. Ultrasound technique can be utilized to inspect the whole axle, but it is not sufficiently sensitive to shallow defects located close to the surface. Therefore, the electromagnetic technique is proposed to detect surface breaking cracks that cannot be detected by ultrasonic technique.

  5. Instantaneous Wavelet Energetic Transfers between Atmospheric Blocking and Local Eddies.

    NASA Astrophysics Data System (ADS)

    Fournier, Aimé

    2005-07-01

    A new wavelet energetics technique, based on best-shift orthonormal wavelet analysis (OWA) of an instantaneous synoptic map, is constructed for diagnosing nonlinear kinetic energy (KE) transfers in five observed blocking cases. At least 90% of the longitudinal variance of time and latitude band mean 50-kPa geopotential is reconstructed by only two wavelets using best shift. This superior efficiency to the standard OWAs persists for time-evolving structures. The cases comprise two categories, respectively dominated by zonal-wavenumber sets {1} and {1, 2}. Further OWA of instantaneous residual nonblocking structures, combined with new “nearness” criteria, yields three more orthogonal components, representing smaller-scale eddies near the block (upstream and downstream) and distant structures. This decomposition fulfills a vision expressed to the author by Saltzman. Such a decomposition is not obtainable by simple Fourier analysis.Eddy patterns apparent in the components' contours suggest inferring geostrophic energetic interactions, but the component Rossby numbers may be too large to support the inference. However, a new result enabled by this method is the instantaneous attribution of blocking strain-field effects to particular energetically interactive eddies, consistent with Shutts' hypothesis. Such attribution was only possible before in simplified models or in a time-average sense. In four of five blocks, the upstream eddies feed KE to the block, which in turn, in three of four cases, transmits KE to the downstream eddies. The small case size precludes statistically significant conclusions. The appendixes link low-order blocking structure and dynamics to some wavelet design principles and propose a new interaction diagnosis, similar to E-vector analysis, but instantaneous.

  6. Eddy Correlation Flux Measurement System Handbook

    SciTech Connect

    Cook, D. R.

    2016-01-01

    The eddy correlation (ECOR) flux measurement system provides in situ, half-hour measurements of the surface turbulent fluxes of momentum, sensible heat, latent heat, and carbon dioxide (CO2) (and methane at one Southern Great Plains extended facility (SGP EF) and the North Slope of Alaska Central Facility (NSA CF). The fluxes are obtained with the eddy covariance technique, which involves correlation of the vertical wind component with the horizontal wind component, the air temperature, the water vapor density, and the CO2 concentration. The instruments used are: • a fast-response, three-dimensional (3D) wind sensor (sonic anemometer) to obtain the orthogonal wind components and the speed of sound (SOS) (used to derive the air temperature) • an open-path infrared gas analyzer (IRGA) to obtain the water vapor density and the CO2 concentration, and • an open-path infrared gas analyzer (IRGA) to obtain methane density and methane flux at one SGP EF and at the NSA CF. The ECOR systems are deployed at the locations where other methods for surface flux measurements (e.g., energy balance Bowen ratio [EBBR] systems) are difficult to employ, primarily at the north edge of a field of crops. A Surface Energy Balance System (SEBS) has been installed collocated with each deployed ECOR system in SGP, NSA, Tropical Western Pacific (TWP), ARM Mobile Facility 1 (AMF1), and ARM Mobile Facility 2 (AMF2). The surface energy balance system consists of upwelling and downwelling solar and infrared radiometers within one net radiometer, a wetness sensor, and soil measurements. The SEBS measurements allow the comparison of ECOR sensible and latent heat fluxes with the energy balance determined from the SEBS and provide information on wetting of the sensors for data quality purposes. The SEBS at one SGP and one NSA site also support upwelling and downwelling PAR measurements to qualify those two locations as Ameriflux sites.

  7. Improved Imaging With Laser-Induced Eddy Currents

    NASA Technical Reports Server (NTRS)

    Chern, Engmin J.

    1993-01-01

    System tests specimen of material nondestructively by laser-induced eddy-current imaging improved by changing method of processing of eddy-current signal. Changes in impedance of eddy-current coil measured in absolute instead of relative units.

  8. Toward large eddy simulation of turbulent flow over an airfoil

    NASA Technical Reports Server (NTRS)

    Choi, Haecheon

    1993-01-01

    The flow field over an airfoil contains several distinct flow characteristics, e.g. laminar, transitional, turbulent boundary layer flow, flow separation, unstable free shear layers, and a wake. This diversity of flow regimes taxes the presently available Reynolds averaged turbulence models. Such models are generally tuned to predict a particular flow regime, and adjustments are necessary for the prediction of a different flow regime. Similar difficulties are likely to emerge when the large eddy simulation technique is applied with the widely used Smagorinsky model. This model has not been successful in correctly representing different turbulent flow fields with a single universal constant and has an incorrect near-wall behavior. Germano et al. (1991) and Ghosal, Lund & Moin have developed a new subgrid-scale model, the dynamic model, which is very promising in alleviating many of the persistent inadequacies of the Smagorinsky model: the model coefficient is computed dynamically as the calculation progresses rather than input a priori. The model has been remarkably successful in prediction of several turbulent and transitional flows. We plan to simulate turbulent flow over a '2D' airfoil using the large eddy simulation technique. Our primary objective is to assess the performance of the newly developed dynamic subgrid-scale model for computation of complex flows about aircraft components and to compare the results with those obtained using the Reynolds average approach and experiments. The present computation represents the first application of large eddy simulation to a flow of aeronautical interest and a key demonstration of the capabilities of the large eddy simulation technique.

  9. Biogeochemical characteristics of a long-lived anticyclonic eddy in the eastern South Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Cornejo, M.; Bravo, L.; Ramos, M.; Pizarro, O.; Karstensen, J.; Gallegos, M.; Correa-Ramirez, M.; Silva, N.; Farias, L.; Karp-Boss, L.

    2015-09-01

    Eastern boundary upwelling systems are characterized by high productivity that often leads to subsurface hypoxia on the shelf. Mesoscale eddies are important, frequent, and persistent features of circulation in these regions, transporting physical, chemical and biological properties from shelves to the open ocean. In austral fall of 2011, during the Tara Oceans expedition, a subsurface layer (200-400 m) in which the concentration of oxygen was very low (< 2 μmol kg-1 of O2) was observed in the eastern South Pacific, ~ 900 km offshore (30° S, 81° W). Satellite altimetry combined with CTD observations associated the local oxygen anomaly with an intrathermocline, anticyclonic, mesoscale eddy with a diameter of about 150 km. The eddy contained Equatorial Subsurface Water (ESSW) that at this latitude is normally restricted near the coast. Undersaturation (44 %) of nitrous oxide (N2O) and nitrite accumulation (> 0.5 μM) gave evidence for denitrification in this water mass. Based on satellite altimetry, we tracked the eddy back to its region of formation on the coast of central Chile (36.1° S, 74.6° W). We estimate that the eddy formed in April 2010. Field studies conducted on the Chilean shelf in June 2010 provided approximate information on initial O2 and N2O concentrations of "source water" in the region at the time of eddy formation. Concentrations of both O2 and N2O in the oxygen minimum zone (OMZ) of the offshore eddy were lower than its surroundings or "source water" on the shelf, suggesting that these chemical species were consumed as the eddy moved offshore. Estimates of apparent oxygen utilization rates at the OMZ of the eddy ranged from 0.29 to 44 nmol L-1 d-1 and the rate of N2O consumption was 3.92 nmol L-1 d-1. Our results show that mesoscale eddies in the ESP not only transport physical properties of the ESSW from the coast to the ocean interior, but also export and transform biogeochemical properties, creating suboxic environments in the oligotrophic

  10. Eddy-Current Inspection of Ball Bearings

    NASA Technical Reports Server (NTRS)

    Bankston, B.

    1985-01-01

    Custom eddy-current probe locates surface anomalies. Low friction air cushion within cone allows ball to roll easily. Eddy current probe reliably detects surface and near-surface cracks, voids, and material anomalies in bearing balls or other spherical objects. Defects in ball surface detected by probe displayed on CRT and recorded on strip-chart recorder.

  11. Observed deep energetic eddies by seamount wake

    NASA Astrophysics Data System (ADS)

    Chen, Gengxin; Wang, Dongxiao; Dong, Changming; Zu, Tingting; Xue, Huijie; Shu, Yeqiang; Chu, Xiaoqing; Qi, Yiquan; Chen, Hui

    2015-11-01

    Despite numerous surface eddies are observed in the ocean, deep eddies (a type of eddies which have no footprints at the sea surface) are much less reported in the literature due to the scarcity of their observation. In this letter, from recently collected current and temperature data by mooring arrays, a deep energetic and baroclinic eddy is detected in the northwestern South China Sea (SCS) with its intensity, size, polarity and structure being characterized. It remarkably deepens isotherm at deep layers by the amplitude of ~120 m and induces a maximal velocity amplitude about 0.18 m/s, which is far larger than the median velocity (0.02 m/s). The deep eddy is generated in a wake when a steering flow in the upper layer passes a seamount, induced by a surface cyclonic eddy. More observations suggest that the deep eddy should not be an episode in the area. Deep eddies significantly increase the velocity intensity and enhance the mixing in the deep ocean, also have potential implication for deep-sea sediments transport.

  12. Observed deep energetic eddies by seamount wake

    PubMed Central

    Chen, Gengxin; Wang, Dongxiao; Dong, Changming; Zu, Tingting; Xue, Huijie; Shu, Yeqiang; Chu, Xiaoqing; Qi, Yiquan; Chen, Hui

    2015-01-01

    Despite numerous surface eddies are observed in the ocean, deep eddies (a type of eddies which have no footprints at the sea surface) are much less reported in the literature due to the scarcity of their observation. In this letter, from recently collected current and temperature data by mooring arrays, a deep energetic and baroclinic eddy is detected in the northwestern South China Sea (SCS) with its intensity, size, polarity and structure being characterized. It remarkably deepens isotherm at deep layers by the amplitude of ~120 m and induces a maximal velocity amplitude about 0.18 m/s, which is far larger than the median velocity (0.02 m/s). The deep eddy is generated in a wake when a steering flow in the upper layer passes a seamount, induced by a surface cyclonic eddy. More observations suggest that the deep eddy should not be an episode in the area. Deep eddies significantly increase the velocity intensity and enhance the mixing in the deep ocean, also have potential implication for deep-sea sediments transport. PMID:26617343

  13. Observed deep energetic eddies by seamount wake.

    PubMed

    Chen, Gengxin; Wang, Dongxiao; Dong, Changming; Zu, Tingting; Xue, Huijie; Shu, Yeqiang; Chu, Xiaoqing; Qi, Yiquan; Chen, Hui

    2015-01-01

    Despite numerous surface eddies are observed in the ocean, deep eddies (a type of eddies which have no footprints at the sea surface) are much less reported in the literature due to the scarcity of their observation. In this letter, from recently collected current and temperature data by mooring arrays, a deep energetic and baroclinic eddy is detected in the northwestern South China Sea (SCS) with its intensity, size, polarity and structure being characterized. It remarkably deepens isotherm at deep layers by the amplitude of ~120 m and induces a maximal velocity amplitude about 0.18 m/s, which is far larger than the median velocity (0.02 m/s). The deep eddy is generated in a wake when a steering flow in the upper layer passes a seamount, induced by a surface cyclonic eddy. More observations suggest that the deep eddy should not be an episode in the area. Deep eddies significantly increase the velocity intensity and enhance the mixing in the deep ocean, also have potential implication for deep-sea sediments transport.

  14. Exploring Eddy-Covariance Measurements Using a Spatial Approach: The Eddy Matrix

    NASA Astrophysics Data System (ADS)

    Engelmann, Christian; Bernhofer, Christian

    2016-10-01

    Taylor's frozen turbulence hypothesis states that "standard" eddy-covariance measurements of fluxes at a fixed location can replace a spatial ensemble of instantaneous values at multiple locations. For testing this hypothesis, a unique turbulence measurement set-up was used for two measurement campaigns over desert (Namibia) and grassland (Germany) in 2012. This "Eddy Matrix" combined nine ultrasonic anemometer-thermometers and 17 thermocouples in a 10 m × 10 m regular grid with 2.5-m grid distance. The instantaneous buoyancy flux derived from the spatial eddy covariance of the Eddy Matrix was highly variable in time (from -0.3 to 1 m K s^{-1}). However, the 10-min average reflected 83 % of the reference eddy-covariance flux with a good correlation. By introducing a combined eddy-covariance method (the spatial eddy covariance plus the additional flux of the temporal eddy covariance of the spatial mean values), the mean flux increases by 9 % relative to the eddy-covariance reference. Considering the typical underestimation of fluxes by the standard eddy-covariance method, this is seen as an improvement. Within the limits of the Eddy Matrix, Taylor's hypothesis is supported by the results.

  15. Wind changes above warm Agulhas Current eddies

    NASA Astrophysics Data System (ADS)

    Rouault, M.; Verley, P.; Backeberg, B.

    2016-04-01

    Sea surface temperature (SST) estimated from the Advanced Microwave Scanning Radiometer E onboard the Aqua satellite and altimetry-derived sea level anomalies are used south of the Agulhas Current to identify warm-core mesoscale eddies presenting a distinct SST perturbation greater than to 1 °C to the surrounding ocean. The analysis of twice daily instantaneous charts of equivalent stability-neutral wind speed estimates from the SeaWinds scatterometer onboard the QuikScat satellite collocated with SST for six identified eddies shows stronger wind speed above the warm eddies than the surrounding water in all wind directions, if averaged over the lifespan of the eddies, as was found in previous studies. However, only half of the cases showed higher wind speeds above the eddies at the instantaneous scale; 20 % of cases had incomplete data due to partial global coverage by the scatterometer for one path. For cases where the wind is stronger above warm eddies, there is no relationship between the increase in surface wind speed and the SST perturbation, but we do find a linear relationship between the decrease in wind speed from the centre to the border of the eddy downstream and the SST perturbation. SST perturbations range from 1 to 6 °C for a mean eddy SST of 15.9 °C and mean SST perturbation of 2.65 °C. The diameter of the eddies range from 100 to 250 km. Mean background wind speed is about 12 m s-1 (mostly southwesterly to northwesterly) and ranging mainly from 4 to 16 m s-1. The mean wind increase is about 15 %, which corresponds to 1.8 m s-1. A wind speed increase of 4 to 7 m s-1 above warm eddies is not uncommon. Cases where the wind did not increase above the eddies or did not decrease downstream had higher wind speeds and occurred during a cold front associated with intense cyclonic low-pressure systems, suggesting certain synoptic conditions need to be met to allow for the development of wind speed anomalies over warm-core ocean eddies. In many cases

  16. Intense submesoscale upwelling in anticyclonic eddies

    NASA Astrophysics Data System (ADS)

    Brannigan, L.

    2016-04-01

    Observations from around the global ocean show that enhanced biological activity can be found in anticyclonic eddies. This may mean that upwelling of nutrient-rich water occurs within the eddy, but such upwelling is not captured by models that resolve mesoscale processes. High-resolution simulations presented here show intense submesoscale upwelling from the thermocline to the mixed layer in anticyclonic eddies. The properties of the upwelling are consistent with a process known as symmetric instability. A simple limiting nutrient experiment shows that this upwelling can drive much higher biological activity in anticyclonic eddies when there is a high nutrient concentration in the thermocline. An estimate for the magnitude of upwelling associated with symmetric instability in anticyclonic eddies in the Sargasso Sea shows that it may be of comparable magnitude to other processes, though further work is required to understand the full implications for basin-scale nutrient budgets.

  17. Orientation of eddy fluxes in geostrophic turbulence.

    PubMed

    Nadiga, B T

    2008-07-28

    Given its importance in parametrizing eddies, we consider the orientation of eddy flux of potential vorticity (PV) in geostrophic turbulence. We take two different points of view, a classical ensemble- or time-average point of view and a second scale decomposition point of view. A net alignment of the eddy flux of PV with the appropriate mean gradient or the large-scale gradient of PV is required. However, we find this alignment to be very weak. A key finding of our study is that in the scale decomposition approach, there is a strong correlation between the eddy flux and a nonlinear combination of resolved gradients. This strong correlation is absent in the classical decomposition. This finding points to a new model to parametrize the effects of eddies in global ocean circulation.

  18. The nature and consequences of oceanic eddies

    NASA Astrophysics Data System (ADS)

    McWilliams, James C.

    Mesoscale eddies are everywhere in the ocean. They provide important material and dynamical fluxes for the equilibrium balances of the general circulation and climate. Eddy effects are necessary ingredients for oceanic general circulation models, whether parameterized or, as is increasingly done, explicitly resolved in the simulations. The primary characteristics of eddies are summarized in this paper, and the principal roles of eddies in the dynamics of large-scale circulation are described. Those eddy roles are the following: maintenance of boundary and equatorial currents; lateral and vertical buoyancy fluxes, isopycnal form stress, and available potential energy conversion; Reynolds stress, kinetic energy conversion, and current rectification; material dispersion and mixing; energy cascades and dissipation routes; Lagrangian mean advection; surface-layer density restratification; ventilation and subduction; stratification control; frontogenesis; topographic form stress; biological pumping and quenching; and generation of intrinsic climate variability.

  19. Eddy current analysis in fusion devices

    SciTech Connect

    Turner, L.R.

    1988-06-01

    In magnetic fusion devices, particularly tokamaks and reversed field pinch (RFP) experiments, time-varying magnetic fields are in intimate contact with electrically conducting components of the device. Induced currents, fields, forces, and torques result. This note reviews the analysis of eddy current effects in the following systems: Interaction of a tokamak plasma with the eddy currents in the first wall, blanket, and shield (FWBS) systems; Eddy currents in a complex but two-dimensional vacuum vessel, as in TFTR, JET, and JT-60; Eddy currents in the FWBS system of a tokamak reactor, such as NET, FER, or ITER; and Eddy currents in a RFP shell. The cited studies are chosen to be illustrative, rather than exhaustive. 42 refs.

  20. Linkages between controlled floods, eddy sandbar dynamics, and riparian vegetation along the Colorado River in Marble Canyon, Arizona

    NASA Astrophysics Data System (ADS)

    Mueller, E. R.; Grams, P. E.; Hazel, J. E., Jr.; Schmeeckle, M. W.

    2015-12-01

    Controlled floods are released from Glen Canyon Dam to build and maintain eddy sandbars along the Colorado River in Grand Canyon National Park. Long-term monitoring shows that the topographic response to controlled floods varies considerably between eddies, likely reflecting different geometric configurations and flow hydraulics. Differences in eddy sandbar response also reflect the degree of vegetation establishment since the 1980s when reservoir spills more than double the magnitude of controlled floods cleared most sandbars of vegetation. Here we explore the geomorphology of sandbar responses in the context of controlled floods, debris fan-eddy geometry, and riparian vegetation establishment. In Marble Canyon, the proportion of eddy area stabilized by vegetation is negatively correlated with water surface slope and the rate of stage change with discharge. Less vegetated sites are more dynamic; they tend to build open sandbars during controlled floods and show greater topographic variability in the eddy compared to the main channel. In contrast, deposition of open sandbars is limited where vegetation establishment has decreased channel width, altering the pattern of eddy recirculation and sediment redistribution. In these locations, deposition during controlled floods is more akin to floodplain sedimentation, and the elevation of vegetated bar surfaces increases with successive floods. Changes in sand storage in the main channel are greater than storage change in the eddy at these lower gradient sites, and controlled floods tend to evacuate sand that has accumulated on the bed. The degree to which vegetation has stabilized sandbar surfaces may thus provide a proxy for different hydraulic conditions and a better canyon-wide assessment of controlled flood response. Our results apply primarily to large eddies in Marble Canyon, and ongoing flow modeling and vegetation composition mapping will allow further assessment of eddy sandbar-riparian vegetation interactions

  1. Consequences of Advanced Glycation End Products Accumulation in Chronic Kidney Disease and Clinical Usefulness of Their Assessment Using a Non-invasive Technique - Skin Autofluorescence.

    PubMed

    Oleniuc, Mihaela; Secara, Irina; Onofriescu, Mihai; Hogas, Simona; Voroneanu, Luminita; Siriopol, Dimitrie; Covic, Adrian

    2011-10-01

    Accelerated formation and accumulation of advanced glycation end-products occur under circumstances of increased supply of substrates such as hyperglycaemic or oxidative stress and in age-related and chronic diseases like diabetes mellitus, chronic renal failure, neurodegenerative diseases, osteoarthritis and also non-diabetic atherosclerosis and chronic heart failure. Advanced glycation end-products accumulation occurs especially on long-lived proteins such as collagen in the skin and in vascular basement membranes leading to vascular damage. Adequate renal clearance capacity is an important factor in the effective removal of advanced glycation end-products. The Autofluorescence Reader was developed as a marker, representative for tissue advanced glycation end-products accumulation, easily applicable in a clinical setting, initially for predicting diabetes related complications. Studies have already shown a relationship between skin autofluorescence and diabetes complications, as well as its predictive value for total and cardiovascular mortality in type 2 diabetes. Moreover skin autofluorescence was demonstrated to be superior to Haemoglobin A1c and other conventional risk factors. Advanced glycation end-products have been proposed as a novel factor involved in the development and progression of chronic heart failure. Assessment of advanced glycation end-products accumulation in end-stage renal disease and undergoing renal replacement therapies patients has become of great importance. Cardiovascular and connective tissue disorders are very common in patients with end-stage renal disease, and the accumulation of advanced glycation end-products is significantly increased in these patients. Mortality is markedly increased in patients with decreased kidney function, particularly in patients with end-stage renal disease. Skin advanced glycation end-products levels are strong predictors of survival in haemodialysis patients independent of other established risk factors

  2. A turnkey data logger program for field-scale energy flux density measurements using eddy covariance and surface renewal

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Micrometeorological methods and ecosystem-scale energy and mass flux density measurements have become increasingly important in soil, agricultural, and environmental sciences. For many scientists without formal training in atmospheric science, these techniques are relatively inaccessible. Eddy cov...

  3. Accumulation of airborne trace elements in mosses, lichens and synthetic materials exposed at urban monitoring stations: towards a harmonisation of the moss-bag technique.

    PubMed

    Giordano, S; Adamo, P; Spagnuolo, V; Tretiach, M; Bargagli, R

    2013-01-01

    Mosses, lichens and cellulose filters were exposed for 17 weeks at four urban monitoring stations in Naples (S Italy) to assess the accumulation of airborne Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Mg, Mn, Mo, Ni, Pb, Ti, V, and Zn. In each site, the element accumulation was significantly higher in the moss Hypnum cupressiforme than in the lichen Pseudevernia furfuracea. Acid washed mosses accumulated the highest amount of trace elements, but the differences in element concentrations among the moss samples exposed after water washing and different devitalisation treatments (acid washing, oven drying and water boiling) and between the lichen samples exposed with and without the nylon bag were not statistically significant. The cellulose filters showed the lowest accumulation capability. The reciprocal ordination of sites and exposed materials showed an increasing contamination gradient (especially for Pb, Cu and Zn) from the background site to the trafficked city streets; this pattern was undetectable from PM(10) data recorded by the automatic monitoring devices operating in the four exposure sites. The element profile in exposed materials did not change substantially throughout the urban area and particles of polluted urban soils seem the main source of airborne metals in Naples. Through a comprehensive evaluation of the results from this and previous studies, a protocol is suggested for the moss-bag monitoring of trace element deposition in urban environments.

  4. Accumulate Repeat Accumulate Coded Modulation

    NASA Technical Reports Server (NTRS)

    Abbasfar, Aliazam; Divsalar, Dariush; Yao, Kung

    2004-01-01

    In this paper we propose an innovative coded modulation scheme called 'Accumulate Repeat Accumulate Coded Modulation' (ARA coded modulation). This class of codes can be viewed as serial turbo-like codes, or as a subclass of Low Density Parity Check (LDPC) codes that are combined with high level modulation. Thus at the decoder belief propagation can be used for iterative decoding of ARA coded modulation on a graph, provided a demapper transforms the received in-phase and quadrature samples to reliability of the bits.

  5. Conformable eddy current array delivery

    NASA Astrophysics Data System (ADS)

    Summan, Rahul; Pierce, Gareth; Macleod, Charles; Mineo, Carmelo; Riise, Jonathan; Morozov, Maxim; Dobie, Gordon; Bolton, Gary; Raude, Angélique; Dalpé, Colombe; Braumann, Johannes

    2016-02-01

    The external surface of stainless steel containers used for the interim storage of nuclear material may be subject to Atmospherically Induced Stress Corrosion Cracking (AISCC). The inspection of such containers poses a significant challenge due to the large quantities involved; therefore, automating the inspection process is of considerable interest. This paper reports upon a proof-of-concept project concerning the automated NDT of a set of test containers containing artificially generated AISCCs. An Eddy current array probe with a conformable padded surface from Eddyfi was used as the NDT sensor and end effector on a KUKA KR5 arc HW robot. A kinematically valid cylindrical raster scan path was designed using the KUKA|PRC path planning software. Custom software was then written to interface measurement acquisition from the Eddyfi hardware with the motion control of the robot. Preliminary results and analysis are presented from scanning two canisters.

  6. Rotating concave eddy current probe

    DOEpatents

    Roach, Dennis P.; Walkington, Phil; Rackow, Kirk A.; Hohman, Ed

    2008-04-01

    A rotating concave eddy current probe for detecting fatigue cracks hidden from view underneath the head of a raised head fastener, such as a buttonhead-type rivet, used to join together structural skins, such as aluminum aircraft skins. The probe has a recessed concave dimple in its bottom surface that closely conforms to the shape of the raised head. The concave dimple holds the probe in good alignment on top of the rivet while the probe is rotated around the rivet's centerline. One or more magnetic coils are rigidly embedded within the probe's cylindrical body, which is made of a non-conducting material. This design overcomes the inspection impediment associated with widely varying conductivity in fastened joints.

  7. A High Performance Sample Delivery System for Closed-Path Eddy Covariance Measurements

    NASA Astrophysics Data System (ADS)

    Nottrott, Anders; Leggett, Graham; Alstad, Karrin; Wahl, Edward

    2016-04-01

    The Picarro G2311-f Cavity Ring-Down Spectrometer (CRDS) measures CO2, CH4 and water vapor at high frequency with parts-per-billion (ppb) sensitivity for eddy covariance, gradient, eddy accumulation measurements. In flux mode, the analyzer measures the concentration of all three species at 10 Hz with a cavity gas exchange time of 5 Hz. We developed an enhanced pneumatic sample delivery system for drawing air from the atmosphere into the cavity. The new sample delivery system maintains a 5 Hz gas exchange time, and allows for longer sample intake lines to be configured in tall tower applications (> 250 ft line at sea level). We quantified the system performance in terms of vacuum pump head room and 10-90% concentration step response for several intake line lengths at various elevations. Sample eddy covariance data are shown from an alfalfa field in Northern California, USA.

  8. Eddy Covariance Method: Overview of General Guidelines and Conventional Workflow

    NASA Astrophysics Data System (ADS)

    Burba, G. G.; Anderson, D. J.; Amen, J. L.

    2007-12-01

    Atmospheric flux measurements are widely used to estimate water, heat, carbon dioxide and trace gas exchange between the ecosystem and the atmosphere. The Eddy Covariance method is one of the most direct, defensible ways to measure and calculate turbulent fluxes within the atmospheric boundary layer. However, the method is mathematically complex, and requires significant care to set up and process data. These reasons may be why the method is currently used predominantly by micrometeorologists. Modern instruments and software can potentially expand the use of this method beyond micrometeorology and prove valuable for plant physiology, hydrology, biology, ecology, entomology, and other non-micrometeorological areas of research. The main challenge of the method for a non-expert is the complexity of system design, implementation, and processing of the large volume of data. In the past several years, efforts of the flux networks (e.g., FluxNet, Ameriflux, CarboEurope, Fluxnet-Canada, Asiaflux, etc.) have led to noticeable progress in unification of the terminology and general standardization of processing steps. The methodology itself, however, is difficult to unify, because various experimental sites and different purposes of studies dictate different treatments, and site-, measurement- and purpose-specific approaches. Here we present an overview of theory and typical workflow of the Eddy Covariance method in a format specifically designed to (i) familiarize a non-expert with general principles, requirements, applications, and processing steps of the conventional Eddy Covariance technique, (ii) to assist in further understanding the method through more advanced references such as textbooks, network guidelines and journal papers, (iii) to help technicians, students and new researchers in the field deployment of the Eddy Covariance method, and (iv) to assist in its use beyond micrometeorology. The overview is based, to a large degree, on the frequently asked questions

  9. Multifrequency eddy-current inspection of seam weld in steel sheath

    SciTech Connect

    Smith, J.H.; Dodd, C.V.; Chitwood, L.D.

    1985-04-01

    Multifrequency eddy-current techniques were used to perform a continuous on-line inspection of the seam weld in the steel jacket for a superconducting cable. The inspection was required to detect both surface and internal weld flaws in the presence of a large, highly conductive central conductor. Raw eddy-current data were recorded on magnetic tape, and test properties such as discontinuity size and weld penetration were determined by mathematically fitting these data to coefficients developed with representative standards. A sophisticated computer-controlled scanning technique was applied, and a unique scanning device was developed to provide full coverage of the weld and heat-affected zone. The techniques used to develop this multifrequency eddy-current examination are described in this report along with the test equipment, test procedures, and computer programs.

  10. Consequences of Advanced Glycation End Products Accumulation in Chronic Kidney Disease and Clinical Usefulness of Their Assessment Using a Non-invasive Technique - Skin Autofluorescence.

    PubMed

    Oleniuc, Mihaela; Secara, Irina; Onofriescu, Mihai; Hogas, Simona; Voroneanu, Luminita; Siriopol, Dimitrie; Covic, Adrian

    2011-10-01

    Accelerated formation and accumulation of advanced glycation end-products occur under circumstances of increased supply of substrates such as hyperglycaemic or oxidative stress and in age-related and chronic diseases like diabetes mellitus, chronic renal failure, neurodegenerative diseases, osteoarthritis and also non-diabetic atherosclerosis and chronic heart failure. Advanced glycation end-products accumulation occurs especially on long-lived proteins such as collagen in the skin and in vascular basement membranes leading to vascular damage. Adequate renal clearance capacity is an important factor in the effective removal of advanced glycation end-products. The Autofluorescence Reader was developed as a marker, representative for tissue advanced glycation end-products accumulation, easily applicable in a clinical setting, initially for predicting diabetes related complications. Studies have already shown a relationship between skin autofluorescence and diabetes complications, as well as its predictive value for total and cardiovascular mortality in type 2 diabetes. Moreover skin autofluorescence was demonstrated to be superior to Haemoglobin A1c and other conventional risk factors. Advanced glycation end-products have been proposed as a novel factor involved in the development and progression of chronic heart failure. Assessment of advanced glycation end-products accumulation in end-stage renal disease and undergoing renal replacement therapies patients has become of great importance. Cardiovascular and connective tissue disorders are very common in patients with end-stage renal disease, and the accumulation of advanced glycation end-products is significantly increased in these patients. Mortality is markedly increased in patients with decreased kidney function, particularly in patients with end-stage renal disease. Skin advanced glycation end-products levels are strong predictors of survival in haemodialysis patients independent of other established risk factors

  11. Poleward migration of eddy driven jets

    NASA Astrophysics Data System (ADS)

    Chemke, Rei; Kaspi, Yohai

    2014-05-01

    There are observational evidence for a poleward migration of temporal anomalies of zonal winds in the upper troposphere. We show that such poleward migration can be due to poleward migration of eddy-driven jets; In fact, any eddy driven baroclinic jet should propagate poleward over time due to the variation of baroclinicity across the jet due to the sphericity of the planet. We demonstrate this using a high resolution idealized GCM where we examine the eddy driven jets over a wide range of rotation rates (up to 24 times the rotation rate of Earth). Unlike Earth-like rotation rates, where the eddy driven jet and the subtropical jet usually merge, at higher rotation rates the eddy driven jets are clearly separated from the subtropical jet and migrate poleward, while the subtropical jets remain in a constant latitude over time. The poleward drift is caused because measures of baroclinicity, such as Eady growth rate and supercriticality have a poleward bias due to the variation of the Coriolis parameter across the jet. This results in a poleward biased eddy momentum flux convergence relative to the mean jet, which overtime deflects the jet poleward. This is demonstrated systematically over the series of numerical simulations we present. As the rotation rate increases, and more (narrower) jets emerge the migration rate becomes smaller due to less eddy momentum flux convergence over the narrower baroclinic zones. This mechanism is consistent with eddy life cycle studies, which show the effects of sphericity on eddy propagation. In addition, we suggest scaling for the meridional scale of the jets and their spacing as function of the planetary rotation rate and latitude.

  12. Accumulation and Translocation of Essential and Nonessential Elements by Tomato Plants (Solanum lycopersicum) Cultivated in Open-Air Plots under Organic or Conventional Farming Techniques.

    PubMed

    Liñero, Olaia; Cidad, Maite; Carrero, Jose Antonio; Nguyen, Christophe; de Diego, Alberto

    2015-11-01

    A 5-month experiment was performed to study the accumulation of several inorganic elements in tomato plants cultivated using organic or synthetic fertilizer. Plants were harvested in triplicate at six sampling dates during their life cycle. Statistical and chemometric analysis of data indicated the sequestration of toxic elements and of Na, Zn, Fe, and Co in roots, while the rest of the elements, including Cd, were mainly translocated to aboveground organs. A general decreasing trend in element concentrations with time was observed for most of them. A negative correlation between some element concentrations and ripening stage of fruits was identified. Conventionally grown plants seemed to accumulate more Cd and Tl in their tissues, while organic ones were richer in some nutrients. However, there was no clear effect of the fertilizer used (organic vs synthetic) on the elemental composition of fruits.

  13. Accumulation and Translocation of Essential and Nonessential Elements by Tomato Plants (Solanum lycopersicum) Cultivated in Open-Air Plots under Organic or Conventional Farming Techniques.

    PubMed

    Liñero, Olaia; Cidad, Maite; Carrero, Jose Antonio; Nguyen, Christophe; de Diego, Alberto

    2015-11-01

    A 5-month experiment was performed to study the accumulation of several inorganic elements in tomato plants cultivated using organic or synthetic fertilizer. Plants were harvested in triplicate at six sampling dates during their life cycle. Statistical and chemometric analysis of data indicated the sequestration of toxic elements and of Na, Zn, Fe, and Co in roots, while the rest of the elements, including Cd, were mainly translocated to aboveground organs. A general decreasing trend in element concentrations with time was observed for most of them. A negative correlation between some element concentrations and ripening stage of fruits was identified. Conventionally grown plants seemed to accumulate more Cd and Tl in their tissues, while organic ones were richer in some nutrients. However, there was no clear effect of the fertilizer used (organic vs synthetic) on the elemental composition of fruits. PMID:26457684

  14. Subsurface Defect Detection in Metals with Pulsed Eddy Current

    SciTech Connect

    Plotnikov, Yuri A.; Bantz, Walter J.

    2005-04-09

    The eddy current (EC) method is traditionally used for open surface crack detection in metallic components. Subsurface voids in bulk metals can also be detected by the eddy current devices. Taking into consideration the skin effect in conductive materials, a lower frequency of electromagnetic excitation is used for a deeper penetration. A set of special specimens was designed and fabricated to investigate sensitivity to subsurface voids. Typically, flat bottom holes (FBHs) are used for subsurface defect simulation. This approach is not very representative of real defects for eddy current inspection because the FBH depth extends to the bottom of the specimen. Two-layer specimens with finite depth FBHs were fabricated and scanned with conventional EC of variable frequency. Sensitivity and spatial resolution of EC diminish with flaw depth. The pulsed EC approach was applied for flaw detection at variable distance under the surface. The transient response from multi-layer model was derived and compared to experiments. The multi-frequency nature of pulsed excitation provides effective coverage of a thick layer of material in one pass. Challenging aspects of subsurface flaw detection and visualization using the EC technique are discussed.

  15. Eddy Current Testing, RQA/M1-5330.17.

    ERIC Educational Resources Information Center

    National Aeronautics and Space Administration, Huntsville, AL. George C. Marshall Space Flight Center.

    As one in the series of classroom training handbooks, prepared by the U.S. space program, instructional material is presented in this volume concerning familiarization and orientation on eddy current testing. The subject is presented under the following headings: Introduction, Eddy Current Principles, Eddy Current Equipment, Eddy Current Methods,…

  16. Seasonal variability in global eddy diffusion and the effect on neutral density

    NASA Astrophysics Data System (ADS)

    Pilinski, M. D.; Crowley, G.

    2015-04-01

    We describe a method for making single-satellite estimates of the seasonal variability in global-average eddy diffusion coefficients. Eddy diffusion values as a function of time were estimated from residuals of neutral density measurements made by the Challenging Minisatellite Payload (CHAMP) and simulations made using the thermosphere-ionosphere-mesosphere electrodynamics global circulation model (TIME-GCM). The eddy diffusion coefficient results are quantitatively consistent with previous estimates based on satellite drag observations and are qualitatively consistent with other measurement methods such as sodium lidar observations and eddy diffusivity models. Eddy diffusion coefficient values estimated between January 2004 and January 2008 were then used to generate new TIME-GCM results. Based on these results, the root-mean-square sum for the TIME-GCM model is reduced by an average of 5% when compared to density data from a variety of satellites, indicating that the fidelity of global density modeling can be improved by using data from a single satellite like CHAMP. This approach also demonstrates that eddy diffusion could be estimated in near real-time from satellite observations and used to drive a global circulation model like TIME-GCM. Although the use of global values improves modeled neutral densities, there are limitations to this method, which are discussed, including that the latitude dependence of the seasonal neutral-density signal is not completely captured by a global variation of eddy diffusion coefficients. This demonstrates the need for a latitude-dependent specification of eddy diffusion which is also consistent with diffusion observations made by other techniques.

  17. Seasonal Variability in Global Eddy Diffusion and the Effect on Thermospheric Neutral Density

    NASA Astrophysics Data System (ADS)

    Pilinski, M.; Crowley, G.

    2014-12-01

    We describe a method for making single-satellite estimates of the seasonal variability in global-average eddy diffusion coefficients. Eddy diffusion values as a function of time between January 2004 and January 2008 were estimated from residuals of neutral density measurements made by the CHallenging Minisatellite Payload (CHAMP) and simulations made using the Thermosphere Ionosphere Mesosphere Electrodynamics - Global Circulation Model (TIME-GCM). The eddy diffusion coefficient results are quantitatively consistent with previous estimates based on satellite drag observations and are qualitatively consistent with other measurement methods such as sodium lidar observations and eddy-diffusivity models. The eddy diffusion coefficient values estimated between January 2004 and January 2008 were then used to generate new TIME-GCM results. Based on these results, the RMS difference between the TIME-GCM model and density data from a variety of satellites is reduced by an average of 5%. This result, indicates that global thermospheric density modeling can be improved by using data from a single satellite like CHAMP. This approach also demonstrates how eddy diffusion could be estimated in near real-time from satellite observations and used to drive a global circulation model like TIME-GCM. Although the use of global values improves modeled neutral densities, there are some limitations of this method, which are discussed, including that the latitude-dependence of the seasonal neutral-density signal is not completely captured by a global variation of eddy diffusion coefficients. This demonstrates the need for a latitude-dependent specification of eddy diffusion consistent with diffusion observations made by other techniques.

  18. Eddy Current Flexible Probes for Complex Geometries

    NASA Astrophysics Data System (ADS)

    Gilles-Pascaud, C.; Decitre, J. M.; Vacher, F.; Fermon, C.; Pannetier, M.; Cattiaux, G.

    2006-03-01

    The inspection of materials used in aerospace, nuclear or transport industry is a critical issue for the safety of components exposed to stress or/and corrosion. The industry claims for faster, more sensitive, and more flexible techniques. Technologies based on Eddy Current (EC) flexible array probe and magnetic sensor with high sensitivity such as giant magneto-resistance (GMR) could be a good solution to detect surface-breaking flaws in complex shaped surfaces. The CEA has recently developed, with support from the French Institute for Radiological Protection and Nuclear Safety (IRSN), a flexible array probe based on micro-coils etched on Kapton. The probe's performances have been assessed for the inspection of reactor residual heat removal pipes, and for aeronautical applications within the framework of the European project VERDICT. The experimental results confirm the very good detection of narrow cracks on plane and curve shaped surfaces. This paper also describes the recent progresses concerning the application of GMR sensors to EC testing, and the results obtained for the detection of small surface breaking flaws.

  19. Production and destruction of eddy kinetic energy in forced submesoscale eddy-resolving simulations

    NASA Astrophysics Data System (ADS)

    Mukherjee, Sonaljit; Ramachandran, Sanjiv; Tandon, Amit; Mahadevan, Amala

    2016-09-01

    We study the production and dissipation of the eddy kinetic energy (EKE) in a submesoscale eddy field forced with downfront winds using the Process Study Ocean Model (PSOM) with a horizontal grid resolution of 0.5 km. We simulate an idealized 100 m deep mixed-layer front initially in geostrophic balance with a jet in a domain that permits eddies within a range of O(1 km-100 km). The vertical eddy viscosities and the dissipation are parameterized using four different subgrid vertical mixing parameterizations: the k - ɛ , the KPP, and two different constant eddy viscosity and diffusivity profiles with a magnitude of O(10-2m2s-1) in the mixed layer. Our study shows that strong vertical eddy viscosities near the surface reduce the parameterized dissipation, whereas strong vertical eddy diffusivities reduce the lateral buoyancy gradients and consequently the rate of restratification by mixed-layer instabilities (MLI). Our simulations show that near the surface, the spatial variability of the dissipation along the periphery of the eddies depends on the relative alignment of the ageostrophic and geostrophic shear. Analysis of the resolved EKE budgets in the frontal region from the simulations show important similarities between the vertical structure of the EKE budget produced by the k - ɛ and KPP parameterizations, and earlier LES studies. Such an agreement is absent in the simulations using constant eddy-viscosity parameterizations.

  20. Large-eddy Advection in Evapotranspiration Estimates from an Array of Eddy Covariance Towers

    NASA Astrophysics Data System (ADS)

    Lin, X.; Evett, S. R.; Gowda, P. H.; Colaizzi, P. D.; Aiken, R.

    2014-12-01

    Evapotranspiration was continuously measured by an array of eddy covariance systems and large weighting lysimeter in a sorghum in Bushland, Texas in 2014. The advective divergence from both horizontal and vertical directions were measured through profile measurements above canopy. All storage terms were integrated from the depth of soil heat flux plate to the height of eddy covariance measurement. Therefore, a comparison between the eddy covariance system and large weighing lysimeter was conducted on hourly and daily basis. The results for the discrepancy between eddy covariance towers and the lysimeter will be discussed in terms of advection and storage contributions in time domain and frequency domain.

  1. Heat accumulator

    SciTech Connect

    Bracht, A.

    1981-09-29

    A heat accumulator comprises a thermally-insulated reservoir full of paraffin wax mixture or other flowable or meltable heat storage mass, heat-exchangers immersed in the mass, a heat-trap connected to one of the heat-exchangers, and a heat user connected to the other heat-exchanger. Pumps circulate fluids through the heat-trap and the heat-using means and the respective heat-exchangers, and a stirrer agitates and circulates the mass, and the pumps and the stirrer and electric motors driving these devices are all immersed in the mass.

  2. Process Specification for Eddy Current Inspection

    NASA Technical Reports Server (NTRS)

    Koshti, Ajay

    2011-01-01

    This process specification establishes the minimum requirements for eddy current inspection of flat surfaces, fastener holes, threaded fasteners and seamless and welded tubular products made from nonmagnetic alloys such as aluminum and stainless steel.

  3. Comparison of Current and Historical Rates of Ecosystem Carbon Accumulation in a Northern Alberta Peatland

    NASA Astrophysics Data System (ADS)

    Syed, K. H.; Flanagan, L. B.; Carlson, P. J.; Glenn, A. J.; Ponton, S.

    2005-12-01

    As part of Fluxnet-Canada, we have been investigating the environmental controls on net ecosystem carbon dioxide exchange using the eddy covariance technique in a moderately rich (treed) fen in northern Alberta, Canada. In addition, integrated CO2 fluxes were compared to carbon stock measurements and rates of peat accumulation. The total ecosystem carbon stock was 52,669 g C m-2 with the vast majority (52,129) accumulated in peat over a 2 meter depth. The basal age for the peat was 2210 ± 50 years before present. The above-ground carbon stock in the two tree species was 226 g C m-2. The oldest Picea mariana trees were aged at 135 years, and they showed a rapid increase in basal area increment starting about 65 years ago that peaked at rates of 2 cm2 yr-1 about 40 years ago. The Larix laricina trees became established approximately 45 years ago and currently have a basal area increment of 3 to 4 cm2 yr-1, much higher than the current rates (0.5 cm2 yr-1) observed for Picea mariana. The rates of peat accumulation were determined on 210Pb-dated cores. Over the last 70 years the peat gained an average of 113 ± 12 g C m-2 yr-1. This was similar to net ecosystem production measured by eddy covariance (95 and 210 g C m-2 yr-1) over the last two years. Variation in annual net ecosystem production was associated with shifts in weather and growing season length. Current and recent historical rates of carbon accumulation were quite consistent despite significant variation in tree species growth and successional changes in this peatland over the last 70 years.

  4. Dynamics and impacts of eddy-driven air-sea interaction in a regional air-sea coupled model for the US West Coast

    NASA Astrophysics Data System (ADS)

    Seo, H.; Miller, A. J.; Norris, J. R.

    2015-12-01

    The US West Coast coastal oceans feature energetic mesoscale eddies. The associated sea surface temperature (SST) and surface current modify the wind stress, leading to significant dynamic feedback on to the air-sea coupled system. Dynamics of the interaction and impacts on the regional coastal climate are however not well understood; this is an important research question for regional modeling studies for the coastal climate. A high-resolution (7km) SCOAR regional air-sea coupled climate model is used to investigate this question by implementing a novel model coupling technique that separates spatial scale of air-sea interaction. It allows the large-scale coupling effect to be preserved while suppressing the eddy-driven coupling via interactive spatial smoothing of SST and surface current. When the eddy-induced surface current is allowed to modify the wind stress, the eddy kinetic energy (EKE) is reduced by 42%, and this is primarily due to enhanced surface eddy drag. In contrast, the eddy-induced SST-wind coupling has little impact on the EKE. Eddies also modify the Ekman pumping; the resultant Ekman pumping velocity due to surface current attenuates the amplitude of eddies while the SST-induced Ekman pumping affects the propagation of eddies. Rectified change in time-mean SST is determined by the altered offshore temperature advection by the mean and eddy currents, but the magnitude of the mean SST change is greater with the eddy-induced current effect. The subsequent influence on the downstream winter rainfall variability on the US West Coast is stronger with the eddy-induced SST effect because of the proximity of SST anomalies to the coasts. The strong dynamical response in the coastal climate system to the eddy-driven air-sea interaction suggests that the fine-scale air-sea coupling should be better represented in the regional climate modeling studies for the coastal environments and the marine weather.

  5. Improved eddy-current inspection for steam generator tubing

    SciTech Connect

    Dodd, C.V.; Pate, J.R.

    1990-01-01

    Oak Ridge National Laboratory has been engaged in the research and development of eddy-current tests for a wide range of different problems. Recent advances have been made on our multiple-property techniques. This technique generates a set of coefficients that correlate the readings from an eddy-current instrument to the properties of the test that produce the readings. While this technique will work with reflection probes, pancake probes, or bobbin probes, we have concentrated on the latter since this type of test is the most widely used in the commercial inspection of steam generators. The test properties varied include tube supports, tube sheets, copper deposits, magnetite deposits, denting, wastage, pitting, cracking and IGA. While our multiple-property technique has given good results for several years, recent advances in personal computers have considerably improved the results. Fits have been run for the differential bobbin probe that have included over 95,000 different sets of property values and their corresponding readings. Multiple-property fits of these readings have given defect size fits with root-mean-square errors under 5% of the wall thickness for ASME Section XI standards. Although the actual measurement of the defect depths is not that good (without corrections), the signal-to-noise ratio is very good, even at copper and magnetite interfaces. Different types of function fits have been tested for the various types of probes and defects, and optimum functions have been determined for each. 3 refs., 8 figs., 1 tab.

  6. Eddy currents in a conducting sphere

    NASA Technical Reports Server (NTRS)

    Bergman, John; Hestenes, David

    1986-01-01

    This report analyzes the eddy current induced in a solid conducting sphere by a sinusoidal current in a circular loop. Analytical expressions for the eddy currents are derived as a power series in the vectorial displacement of the center of the sphere from the axis of the loop. These are used for first order calculations of the power dissipated in the sphere and the force and torque exerted on the sphere by the electromagnetic field of the loop.

  7. Eddy viscosity measurements in a rectangular jet

    NASA Technical Reports Server (NTRS)

    Swan, David H.; Morrison, Gerald L.

    1988-01-01

    The flow field of a rectangular jet with a 2:1 aspect ratio was studied at a Reynolds number of 100,000 (Mach number 0.09) using three-dimensional laser Doppler velocimetry (LDV). Velocity gradients, Reynolds stress tensor components, and scalar eddy viscosities are presented for the major and minor axis planes of the jet. The eddy viscosity model was found to be applicable only in the direction of maximum mean velocity gradient.

  8. Noise Reduction by Signal Accumulation

    ERIC Educational Resources Information Center

    Kraftmakher, Yaakov

    2006-01-01

    The aim of this paper is to show how the noise reduction by signal accumulation can be accomplished with a data acquisition system. This topic can be used for student projects. In many cases, the noise reduction is an unavoidable part of experimentation. Several techniques are known for this purpose, and among them the signal accumulation is the…

  9. Mesoscale eddies transport deep-sea sediments

    PubMed Central

    Zhang, Yanwei; Liu, Zhifei; Zhao, Yulong; Wang, Wenguang; Li, Jianru; Xu, Jingping

    2014-01-01

    Mesoscale eddies, which contribute to long-distance water mass transport and biogeochemical budget in the upper ocean, have recently been taken into assessment of the deep-sea hydrodynamic variability. However, how such eddies influence sediment movement in the deepwater environment has not been explored. Here for the first time we observed deep-sea sediment transport processes driven by mesoscale eddies in the northern South China Sea via a full-water column mooring system located at 2100 m water depth. Two southwestward propagating, deep-reaching anticyclonic eddies passed by the study site during January to March 2012 and November 2012 to January 2013, respectively. Our multiple moored instruments recorded simultaneous or lagging enhancement of suspended sediment concentration with full-water column velocity and temperature anomalies. We interpret these suspended sediments to have been trapped and transported from the southwest of Taiwan by the mesoscale eddies. The net near-bottom southwestward sediment transport by the two events is estimated up to one million tons. Our study highlights the significance of surface-generated mesoscale eddies on the deepwater sedimentary dynamic process. PMID:25089558

  10. Eddies off the Queen Charlotte Islands

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The bright red, green, and turquoise patches to the west of British Columbia's Queen Charlotte Islands and Alaska's Alexander Archipelago highlight the presence of biological activity in the ocean. These colors indicate high concentrations of chlorophyll, the primary pigment found in phytoplankton. Notice that there are a number of eddies visible in the Pacific Ocean in this pseudo-color scene. The eddies are formed by strong outflow currents from rivers along North America's west coast that are rich in nutrients from the springtime snowmelt running off the mountains. This nutrient-rich water helps stimulate the phytoplankton blooms within the eddies. (For more details, read Tracking Eddies that Feed the Sea.) To the west of the eddies in the water, another type of eddy-this one in the atmosphere-forms the clouds into the counterclockwise spiral characteristic of a low pressure system in the Northern Hemisphere. (Click on the image above to see it at full resolution; or click to see the scene in true-color.) The snow-covered mountains of British Columbia are visible in the upper righthand corner of the image. This scene was constructed using SeaWiFS data collected on June 13, 2002. SeaWiFS image courtesy the SeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE

  11. Mesoscale eddies transport deep-sea sediments.

    PubMed

    Zhang, Yanwei; Liu, Zhifei; Zhao, Yulong; Wang, Wenguang; Li, Jianru; Xu, Jingping

    2014-01-01

    Mesoscale eddies, which contribute to long-distance water mass transport and biogeochemical budget in the upper ocean, have recently been taken into assessment of the deep-sea hydrodynamic variability. However, how such eddies influence sediment movement in the deepwater environment has not been explored. Here for the first time we observed deep-sea sediment transport processes driven by mesoscale eddies in the northern South China Sea via a full-water column mooring system located at 2100 m water depth. Two southwestward propagating, deep-reaching anticyclonic eddies passed by the study site during January to March 2012 and November 2012 to January 2013, respectively. Our multiple moored instruments recorded simultaneous or lagging enhancement of suspended sediment concentration with full-water column velocity and temperature anomalies. We interpret these suspended sediments to have been trapped and transported from the southwest of Taiwan by the mesoscale eddies. The net near-bottom southwestward sediment transport by the two events is estimated up to one million tons. Our study highlights the significance of surface-generated mesoscale eddies on the deepwater sedimentary dynamic process.

  12. Evidence of various mechanisms of Cd sequestration in the hyperaccumulator Arabidopsis halleri, the non-accumulator Arabidopsis lyrata, and their progenies by combined synchrotron-based techniques.

    PubMed

    Isaure, Marie-Pierre; Huguet, Stéphanie; Meyer, Claire-Lise; Castillo-Michel, Hiram; Testemale, Denis; Vantelon, Delphine; Saumitou-Laprade, Pierre; Verbruggen, Nathalie; Sarret, Géraldine

    2015-06-01

    Arabidopsis halleri is a model plant for Zn and Cd hyperaccumulation. The objective of this study was to determine the relationship between the chemical forms of Cd, its distribution in leaves, and Cd accumulation and tolerance. An interspecific cross was carried out between A. halleri and the non-tolerant and non-hyperaccumulating relative A. lyrata providing progenies segregating for Cd tolerance and accumulation. Cd speciation and distribution were investigated using X-ray absorption spectroscopy and microfocused X-ray fluorescence. In A. lyrata and non-tolerant progenies, Cd was coordinated by S atoms only or with a small contribution of O groups. Interestingly, the proportion of O ligands increased in A. halleri and tolerant progenies, and they were predominant in most of them, while S ligands were still present. Therefore, the binding of Cd with O ligands was associated with Cd tolerance. In A. halleri, Cd was mainly located in the xylem, phloem, and mesophyll tissue, suggesting a reallocation process for Cd within the plant. The distribution of the metal at the cell level was further discussed. In A. lyrata, the vascular bundles were also Cd enriched, but the epidermis was richer in Cd as compared with the mesophyll. Cd was identified in trichomes of both species. This work demonstrated that both Cd speciation and localization were related to the tolerance character of the plant. PMID:25873676

  13. Large-eddy simulation of the turbulent flow in the downstream region of a backward-facing step

    NASA Astrophysics Data System (ADS)

    Silveira Neto, A.; Grand, D.; Metais, O.; Lesieur, M.

    1991-05-01

    A numerical simulation of a complex turbulent shear flow using large-eddy simulation techniques is carried out. The filtered Navier-Stokes equations are solved with a finite-volume method. The subgrid model is a local adaptation to the physical space of isotropic spectral eddy-viscosity models. The statistics of the mean field are in good agreement with the experimental data available, corresponding to a low step. Calculations in a high-step case show that the eddy structure of the flow presents striking analogies with the plane shear layers, with large billows shed behind the step, and longitudinal hairpin vortices strained between these billows.

  14. Non-Destructive Evaluation of Thermal Spray Coating Interface Quality By Eddy Current Method

    SciTech Connect

    B. Mi; G. Zhao; R. Bayles

    2006-08-10

    Thermal spray coating is usually applied through directing molten or softened particles at very high velocities onto a substrate. An eddy current non-destructive inspection technique is presented here for thermal spray coating interface quality characterization. Several high-velocity-oxy-fuel (HVOF) coated steel plates were produced with various surface preparation conditions or spray process parameters. A quad-frequency eddy current probe was used to manually scan over the coating surface to evaluate the bonding quality. Experimental results show that different surface preparation conditions and varied process parameters can be successfully differentiated by the impedance value observed from the eddy current probe. The measurement is fairly robust and consistent. This non-contact, nondestructive, easy-to-use technique has the potential for evaluating the coating quality immediately after its application so that any defects can be corrected immediately.

  15. Nondestructive Evaluation of Thermal Spray Coating Interface Quality by Eddy Current Method

    NASA Astrophysics Data System (ADS)

    Mi, Bao; Zhao, Xiaoliang (George); Bayles, Robert

    2007-03-01

    Thermal spray coating is usually applied through directing molten or softened particles at very high velocities onto a substrate. An eddy current non-destructive inspection technique is presented here for thermal spray coating interface quality characterization. Several high-velocity-oxy-fuel (HVOF) coated steel plates were produced with various surface preparation conditions or spray process parameters. A quad-frequency eddy current probe was used to manually scan over the coating surface to evaluate the bonding quality. Experimental results show that different surface preparation conditions and varied process parameters can be successfully differentiated by the impedance value observed from the eddy current probe. The measurement is fairly robust and consistent. This non-contact, nondestructive, easy-to-use technique has the potential for evaluating the coating quality immediately after its application so that any defects can be corrected immediately.

  16. Fatty acid profiles of phyllosoma larvae of western rock lobster (Panulirus cygnus) in cyclonic and anticyclonic eddies of the Leeuwin Current off Western Australia

    NASA Astrophysics Data System (ADS)

    Wang, M.; O'Rorke, R.; Waite, A. M.; Beckley, L. E.; Thompson, P.; Jeffs, A. G.

    2014-03-01

    The recent dramatic decline in settlement in the population of the spiny lobster, Panulirus cygnus, may be due to changes in the oceanographic processes that operate offshore of Western Australia. It has been suggested that this decline could be related to poor nutritional condition of the post-larvae, especially lipid which is accumulated in large quantities during the preceding extensive pelagic larval stage. The current study focused on investigations into the lipid content and fatty acid (FA) profiles of lobster phyllosoma larvae from three mid to late stages of larval development (stages VI, VII, VIII) sampled from two cyclonic and two anticyclonic eddies of the Leeuwin Current off Western Australia. The results showed significant accumulation of lipid and energy storage FAs with larval development regardless of location of capture, however, larvae from cyclonic eddies had more lipid and FAs associated with energy storage than larvae from anticyclonic eddies. FA food chain markers from the larvae indicated significant differences in the food webs operating in the two types of eddy, with a higher level of FA markers for production from flagellates and a lower level from copepod grazing in cyclonic versus anticyclonic eddies. The results indicate that the microbial food web operating in cyclonic eddies provides better feeding conditions for lobster larvae despite anticyclonic eddies being generally more productive and containing greater abundances of zooplankton as potential prey for lobster larvae. Gelatinous zooplankton, such as siphonophores, may play an important role in cyclonic eddies by accumulating dispersed microbial nutrients and making them available as larger prey for phyllosoma. The markedly superior nutritional condition of lobster larvae feeding in the microbial food web found in cyclonic eddies, could greatly influence their subsequent settlement and recruitment to the coastal fishery.

  17. Eddy flux and leaf-level measurements of biogenic VOC emissions from mopane woodland of Botswana

    NASA Astrophysics Data System (ADS)

    Greenberg, J. P.; Guenther, A.; Harley, P.; Otter, L.; Veenendaal, E. M.; Hewitt, C. N.; James, A. E.; Owen, S. M.

    2003-07-01

    Biogenic volatile organic compound (BVOC) emissions were measured in a mopane woodland near Maun, Botswana in January-February 2001 as part of SAFARI 2000. This landscape is comprised of more than 95% of one woody plant species, Colophospermum mopane (Caesalpinaceae). Mopane woodlands extend over a broad area of southern Africa. A leaf cuvette technique was used to determine the emission capacities of the major vegetation and the temperature and light dependence of the emissions. In addition, relaxed eddy accumulation (REA) measurements of BVOC fluxes were made on a flux tower, where net CO2 emissions were also measured simultaneously. Large light-dependent emissions of terpenes (mostly α-pinene and D-limonene) were observed from the mopane woodland. The diurnal BVOC emissions were integrated and compared with the CO2 flux. Monoterpene flux exceeded 3000 μg C m-2 h-1 during the daytime period, comparable to isoprene fluxes and much higher than terpene fluxes measured in most areas. The terpene flux constituted approximately 25% of the diurnal net carbon exchange (CO2) during the experimental period. Other BVOC emissions may also contribute to the carbon exchange.

  18. Solving time-dependent two-dimensional eddy current problems

    NASA Technical Reports Server (NTRS)

    Lee, Min Eig; Hariharan, S. I.; Ida, Nathan

    1990-01-01

    Transient eddy current calculations are presented for an EM wave-scattering and field-penetrating case in which a two-dimensional transverse magnetic field is incident on a good (i.e., not perfect) and infinitely long conductor. The problem thus posed is of initial boundary-value interface type, where the boundary of the conductor constitutes the interface. A potential function is used for time-domain modeling of the situation, and finite difference-time domain techniques are used to march the potential function explicitly in time. Attention is given to the case of LF radiation conditions.

  19. Investigating electrical resonance in eddy-current array probes

    NASA Astrophysics Data System (ADS)

    Hughes, R.; Fan, Y.; Dixon, S.

    2016-02-01

    The sensitivity enhancing effects of eddy-current testing at frequencies close to electrical resonance are explored. Var-ied techniques exploiting the phenomenon, dubbed near electrical resonance signal enhancement (NERSE), were experimentally investigated to evaluate its potential exploitation for other interesting applications in aerospace materials, in particular its potential for boosting the sensitivity of standard ECT measurements. Methods for setting and controlling the typically unstable resonant frequencies of such systems are discussed. This research is funded by the EPSRC, via the Research Centre for Non-Destructive Evaluation RCNDE, and Rolls-Royce plc.

  20. Non-Destructive Evaluation of Thermal Spray Coating Interface Quality by Eddy Current Method

    SciTech Connect

    B.Mi; X. Zhao; R. Bayles

    2006-05-26

    Thermal spray coating is usually applied through directing molten or softened particles at very high velocities onto a substrate. An eddy current non-destructive inspection technique is presented here for thermal spray coating interface quality characterization. Several high-velocity-oxy-fuel (HVOF) coated steel plates were produced with different surface preparation conditions before applying the coating, e.g., grit-blasted surface, wire-brush cleaned surface, and a dirty surface. A quad-frequency eddy current probe was used to manually scan over the coating surface to evaluate the bonding quality. Experimental results show that the three surface preparation conditions can be successfully differentiated by looking into the impedance difference observed from the eddy current probe. The measurement is fairly robust and consistent. More specimens are also prepared with variations of process parameters, such as spray angle, stand-off distance, and application of corrosion protective sealant, etc. They are blindly tested to evaluate the reliability of the eddy current system. Quantitative relations between the coating bond strength and the eddy current response are also established with the support of destructive testing. This non-contact, non-destructive, easy to use technique has the potential for evaluating the coating quality immediately after its application so that any defects can be corrected immediately.

  1. Remote field eddy current detection of stress-corrosion cracks. Final report

    SciTech Connect

    Nestleroth, J.B.

    1990-02-01

    The feasibility of detecting stress-corrosion cracks (SSC) using the Remote Field Eddy Current (RFEC) technique was demonstrated. The RFEC technique interrogates the entire thickness of the pipe and is applicable for in-line inspection. If it can be shown that the RFEC technique is effective in detecting SSC, then the technique is an ideal method for detecting the defects of interest. A defect detection model is proposed for explaining the mechanism for crack detection. For axially oriented, closed cracks, such as SCC, the conventional defect detection model proved to be too simplistic and not applicable. Therefore, a new detection mode that examines the flow of circumferential eddy currents was developed based on experimental results. This model, though not rigorous, provides a general understanding of the applicability of the RFEC technique for finding SSC. The data from the cracks and various artificial defects is presented in three formats: isometric projections, pseudocolor images and line-of-sight data. Though only two cracks were found, the experimental results correlate well with the circumferential eddy current theory. A theoretical analysis of the effects of motion on the output signal of the receiver is presented. This analysis indicates that inspection speed of simple implementations may be limited to a few miles per hour. Remote field eddy current inspection has excellent potential for inspection of gas transmission lines for detecting stress corrosion cracks that should be further developed.

  2. Anticyclonic eddies are more productive than cyclonic eddies in subtropical gyres because of winter mixing

    PubMed Central

    Hardman-Mountford, Nick J.; Greenwood, Jim; Richardson, Anthony J.; Feng, Ming; Matear, Richard J.

    2016-01-01

    Mesoscale eddies are ubiquitous features of ocean circulation that modulate the supply of nutrients to the upper sunlit ocean, influencing the rates of carbon fixation and export. The popular eddy-pumping paradigm implies that nutrient fluxes are enhanced in cyclonic eddies because of upwelling inside the eddy, leading to higher phytoplankton production. We show that this view does not hold for a substantial portion of eddies within oceanic subtropical gyres, the largest ecosystems in the ocean. Using space-based measurements and a global biogeochemical model, we demonstrate that during winter when subtropical eddies are most productive, there is increased chlorophyll in anticyclones compared with cyclones in all subtropical gyres (by 3.6 to 16.7% for the five basins). The model suggests that this is a consequence of the modulation of winter mixing by eddies. These results establish a new paradigm for anticyclonic eddies in subtropical gyres and could have important implications for the biological carbon pump and the global carbon cycle. PMID:27386549

  3. Anticyclonic eddies are more productive than cyclonic eddies in subtropical gyres because of winter mixing.

    PubMed

    Dufois, François; Hardman-Mountford, Nick J; Greenwood, Jim; Richardson, Anthony J; Feng, Ming; Matear, Richard J

    2016-05-01

    Mesoscale eddies are ubiquitous features of ocean circulation that modulate the supply of nutrients to the upper sunlit ocean, influencing the rates of carbon fixation and export. The popular eddy-pumping paradigm implies that nutrient fluxes are enhanced in cyclonic eddies because of upwelling inside the eddy, leading to higher phytoplankton production. We show that this view does not hold for a substantial portion of eddies within oceanic subtropical gyres, the largest ecosystems in the ocean. Using space-based measurements and a global biogeochemical model, we demonstrate that during winter when subtropical eddies are most productive, there is increased chlorophyll in anticyclones compared with cyclones in all subtropical gyres (by 3.6 to 16.7% for the five basins). The model suggests that this is a consequence of the modulation of winter mixing by eddies. These results establish a new paradigm for anticyclonic eddies in subtropical gyres and could have important implications for the biological carbon pump and the global carbon cycle. PMID:27386549

  4. Influence of fishing technique on organochlorine pesticide accumulation in fish and its possible human health risk in the Republic of Bénin.

    PubMed

    Yehouenou A Pazou, Elisabeth; Azehoun, Judicaël P; Ahoyo, Theodora; Aléodjrodo, Patrick Edorh; van Straalen, Nico M; van Gestel, Cornelis A M

    2013-09-01

    In Bénin different techniques are used for large-scale commercial fishing, Acadjas (enclosures constructed in the river) and Whédos (holes made in the river banks). This study aimed at assessing the extent of contamination related to these fishing techniques. Fish contained residues of DDT and its metabolites, α-endosulfan, dieldrin, aldrin, endrin and lindane. Pesticide levels were similar in fish from Acadjas and Whédos, except for higher α-endosulfan levels in fish from the Whédos. Comparing pesticide intake levels through fish consumption with tolerable daily intake levels showed that in all cases risk for human health is low.

  5. A daily global mesoscale ocean eddy dataset from satellite altimetry.

    PubMed

    Faghmous, James H; Frenger, Ivy; Yao, Yuanshun; Warmka, Robert; Lindell, Aron; Kumar, Vipin

    2015-01-01

    Mesoscale ocean eddies are ubiquitous coherent rotating structures of water with radial scales on the order of 100 kilometers. Eddies play a key role in the transport and mixing of momentum and tracers across the World Ocean. We present a global daily mesoscale ocean eddy dataset that contains ~45 million mesoscale features and 3.3 million eddy trajectories that persist at least two days as identified in the AVISO dataset over a period of 1993-2014. This dataset, along with the open-source eddy identification software, extract eddies with any parameters (minimum size, lifetime, etc.), to study global eddy properties and dynamics, and to empirically estimate the impact eddies have on mass or heat transport. Furthermore, our open-source software may be used to identify mesoscale features in model simulations and compare them to observed features. Finally, this dataset can be used to study the interaction between mesoscale ocean eddies and other components of the Earth System.

  6. The statistical behaviour of attached eddies

    NASA Astrophysics Data System (ADS)

    Woodcock, J. D.; Marusic, I.

    2015-01-01

    Townsend's attached eddy hypothesis forms the basis of an established model of the logarithmic layer in wall-bounded turbulent flows in which this inertially dominated region is characterised by a hierarchy of geometrically self-similar eddying motions that scale with their distance to the wall. The hypothesis has gained considerable support from high Reynolds number measurements of the second-order moments of the fluctuating velocities. Recently, Meneveau and Marusic ["Generalized logarithmic law for high-order moments in turbulent boundary layers," J. Fluid Mech. 719, R1 (2013)] presented experimental evidence that all even-ordered moments of the streamwise velocity will exhibit a logarithmic dependence on the distance from the wall. They demonstrated that this was consistent with the attached eddy hypothesis, so long as the velocity distribution is assumed to be Gaussian (which allows the use of the central limit theorem). In this paper, we derive this result from the attached eddy model without assuming a Gaussian velocity distribution, and find that such logarithmic behaviours are valid in the large Reynolds number limit. We also revisit the physical and mathematical basis of the attached eddy hypothesis, in order to increase rigour and minimise the assumptions required to apply the hypothesis. To this end, we have extended the proof of Campbell's theorem to apply to the velocity field corresponding to a forest of variously sized eddies that are randomly placed on the wall. This enables us to derive all moments of the velocity in the logarithmic region, including cross-correlations between different components of the velocity. By contrast, previous studies of the attached eddy hypothesis have considered only the mean velocity and its second order moments. From this, we obtain qualitatively correct skewnesses and flatnesses for the spanwise and wall-normal fluctuations. The issue of the Reynolds number dependence of von Kármán's constant is also addressed.

  7. Design and development of scanning eddy current force microscopy for characterization of electrical, magnetic and ferroelectric properties with nanometer resolution

    NASA Astrophysics Data System (ADS)

    Nalladega, Vijayaraghava

    This dissertation describes the design and development of a new high-resolution electrical conductivity imaging technique combining the basic principles of eddy currents and atomic force microscopy (AFM). An electromagnetic coil is used to generate eddy currents in an electrically conducting material. The eddy currents induced in the sample are detected and measured with a magnetic tip attached to the AFM cantilever. The interaction of eddy currents with the magnetic tip-cantilever is theoretically modeled. The model is then used to estimate the eddy current forces generated in a typical metallic material placed in induced current field. The magnitude of the eddy current force is directly proportional to the electrical conductivity of the sample. The theoretical eddy current forces are used to design a magnetic tip-cantilever system with appropriate magnetic field and spring constant to facilitate the development of a high-resolution, high sensitivity electrical conductivity imaging technique. The technique is used to experimentally measure eddy current forces in metals of different conductivities and compared with theoretical and finite element models. The experimental results show that the technique is capable of measuring pN range eddy current forces. The experimental eddy current forces are used to determine the electrical resistivity of a thin copper wire and the experimental value agrees with the bulk resistivity of copper reported in literature. The imaging capabilities of the new technique are demonstrated by imaging the electrical conductivity variations in a composite sample and a dual-phase titanium alloy in lift mode AFM. The results indicate that this technique can be used to detect very small variations in electrical conductivity. The spatial resolution of the technique is determined to be about 25 nm by imaging carbon nanofibers reinforced in polymer matrix. Since AFM is extensively used to characterize nanomaterials, the newly developed technique is

  8. Eddies in the Red Sea: A statistical and dynamical study

    NASA Astrophysics Data System (ADS)

    Zhan, Peng; Subramanian, Aneesh C.; Yao, Fengchao; Hoteit, Ibrahim

    2014-06-01

    Sea level anomaly (SLA) data spanning 1992-2012 were analyzed to study the statistical properties of eddies in the Red Sea. An algorithm that identifies winding angles was employed to detect 4998 eddies propagating along 938 unique eddy tracks. Statistics suggest that eddies are generated across the entire Red Sea but that they are prevalent in certain regions. A high number of eddies is found in the central basin between 18°N and 24°N. More than 87% of the detected eddies have a radius ranging from 50 to 135 km. Both the intensity and relative vorticity scale of these eddies decrease as the eddy radii increase. The averaged eddy lifespan is approximately 6 weeks. AEs and cyclonic eddies (CEs) have different deformation features, and those with stronger intensities are less deformed and more circular. Analysis of long-lived eddies suggests that they are likely to appear in the central basin with AEs tending to move northward. In addition, their eddy kinetic energy (EKE) increases gradually throughout their lifespans. The annual cycles of CEs and AEs differ, although both exhibit significant seasonal cycles of intensity with the winter and summer peaks appearing in February and August, respectively. The seasonal cycle of EKE is negatively correlated with stratification but positively correlated with vertical shear of horizontal velocity and eddy growth rate, suggesting that the generation of baroclinic instability is responsible for the activities of eddies in the Red Sea.

  9. Temporal Large-Eddy Simulation

    NASA Technical Reports Server (NTRS)

    Pruett, C. D.; Thomas, B. C.

    2004-01-01

    In 1999, Stolz and Adams unveiled a subgrid-scale model for LES based upon approximately inverting (defiltering) the spatial grid-filter operator and termed .the approximate deconvolution model (ADM). Subsequently, the utility and accuracy of the ADM were demonstrated in a posteriori analyses of flows as diverse as incompressible plane-channel flow and supersonic compression-ramp flow. In a prelude to the current paper, a parameterized temporal ADM (TADM) was developed and demonstrated in both a priori and a posteriori analyses for forced, viscous Burger's flow. The development of a time-filtered variant of the ADM was motivated-primarily by the desire for a unifying theoretical and computational context to encompass direct numerical simulation (DNS), large-eddy simulation (LES), and Reynolds averaged Navier-Stokes simulation (RANS). The resultant methodology was termed temporal LES (TLES). To permit exploration of the parameter space, however, previous analyses of the TADM were restricted to Burger's flow, and it has remained to demonstrate the TADM and TLES methodology for three-dimensional flow. For several reasons, plane-channel flow presents an ideal test case for the TADM. Among these reasons, channel flow is anisotropic, yet it lends itself to highly efficient and accurate spectral numerical methods. Moreover, channel-flow has been investigated extensively by DNS, and a highly accurate data base of Moser et.al. exists. In the present paper, we develop a fully anisotropic TADM model and demonstrate its utility in simulating incompressible plane-channel flow at nominal values of Re(sub tau) = 180 and Re(sub tau) = 590 by the TLES method. The TADM model is shown to perform nearly as well as the ADM at equivalent resolution, thereby establishing TLES as a viable alternative to LES. Moreover, as the current model is suboptimal is some respects, there is considerable room to improve TLES.

  10. Carbon dioxide emissions in fallow periods of a corn-soybean rotation: eddy-covariance versus chamber methods

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Carbon dioxide (CO2) fluxes at terrestrial surface are typically quantified using eddy-covariance (EC) or chamber (Ch) techniques; however, long-term comparisons of the two techniques are not available. This study was conducted to assess the agreement between EC and Ch techniques when measuring CO2 ...

  11. Role of mesoscale eddies in transport of Fukushima-derived cesium isotopes in the ocean

    NASA Astrophysics Data System (ADS)

    Budyansky, M. V.; Goryachev, V. A.; Kaplunenko, D. D.; Lobanov, V. B.; Prants, S. V.; Sergeev, A. F.; Shlyk, N. V.; Uleysky, M. Yu.

    2015-02-01

    We present the results of in situ measurements of 134Cs and 137Cs released from the Fukushima Nuclear Power Plant (FNPP) collected at surface and different depths in the western North Pacific in June and July 2012. It was found that 15 month after the incident concentrations of radiocesium in the Japan and Okhotsk seas were at background or slightly increased level, while they had increased values in the subarctic front area east of Japan. The highest concentrations of 134Cs and 137Cs up to 13.5±0.9 and 22.7±1.5 Bq m-3 have been found to exceed ten times the background levels before the accident. Maximal content of radiocesium was observed within subsurface and intermediate water layers inside the cores of anticyclonic eddies (100-500 m). Even slightly increased content of radiocesium was found at some eddies at depth of 1000 m. It is expected that convergence and subduction of surface water inside eddies are main mechanisms of downward transport of radionuclides. In situ observations are compared with the results of simulated advection of these radioisotopes by the AVISO altimetric velocity field. Different Lagrangian diagnostics are used to reconstruct the history and origin of synthetic tracers imitating measured seawater samples collected in each of those eddies. The results of observations are consistent with the simulated results. It is shown that the tracers, simulating water samples with increased radioactivity to be measured in the cruise, really visited the areas with presumably high level of contamination. Fast water advection between anticyclonic eddies and convergence of surface water inside eddies makes them responsible for spreading, accumulation and downward transport of cesium rich water to the intermediate depth in the frontal zone.

  12. Wind-Driven Freshwater Buildup in the Beaufort Gyre is Inevitably Constrained by Mesoscale Eddies.

    NASA Astrophysics Data System (ADS)

    Manucharyan, G. E.; Spall, M. A.

    2015-12-01

    Recently the Beaufort Gyre has accumulated over 20,000km3 of freshwater. This accumulation has been partially attributed to strong anticyclonic atmospheric winds that are prevailing over the gyre for almost two decades. However, mechanisms that can counteract the tendency of the anticyclonic wind stress to deepen the halocline are not well understood. Here, we explore the key physical processes affecting the wind-driven accumulation of freshwater within an idealized high resolution model of the Beaufort Gyre. We demonstrate that an equilibrated halocline (with bulk properties consistent with observations) is achieved when the mesoscale eddy field becomes strong enough to counteract the Ekman pumping. We derive analytical scalings for the depth of the haloclione and its spin-up time scale uncovering the physics behind their strong relation to the eddy dynamics. Our study further suggests that the Beaufort Gyre halocline and its freshwater content are currently in a state of high sensitivity to atmospheric winds. Nonetheless, a significant intensification of surface wind stress would lead to a near saturation of the gyre's freshwater content at about 35m -- a constraint inherently set by the intricacies of the mesoscale eddy dynamics.

  13. Characterization and correction of system delays and eddy currents for MR imaging with ultrashort echo-time and time-varying gradients.

    PubMed

    Atkinson, Ian C; Lu, Aiming; Thulborn, Keith R

    2009-08-01

    Reconstruction of high-quality MR images requires precise knowledge of the dynamic gradient magnetic fields used to perform spatial encoding. System delays and eddy currents can perturb the gradient fields in both time and space and significantly degrade the image quality for acquisitions with an ultrashort echo time or with rapidly varying readout gradient waveforms. A technique for simultaneously characterizing and correcting the system delay and linear- and zero-order eddy currents of an MR system is proposed. A single set of calibration scans were used to compute a set of system constants that describe the effects of system delays and eddy currents to enable accurate reconstruction of data collected before uncorrected eddy currents have decayed. The ability of the proposed technique to reproducibly characterize small fixed delays (<50 micros) and short-time constant (<1 ms) eddy currents is demonstrated.

  14. An eddy tracking algorithm based on dynamical systems theory

    NASA Astrophysics Data System (ADS)

    Conti, Daniel; Orfila, Alejandro; Mason, Evan; Sayol, Juan Manuel; Simarro, Gonzalo; Balle, Salvador

    2016-11-01

    This work introduces a new method for ocean eddy detection that applies concepts from stationary dynamical systems theory. The method is composed of three steps: first, the centers of eddies are obtained from fixed points and their linear stability analysis; second, the size of the eddies is estimated from the vorticity between the eddy center and its neighboring fixed points, and, third, a tracking algorithm connects the different time frames. The tracking algorithm has been designed to avoid mismatching connections between eddies at different frames. Eddies are detected for the period between 1992 and 2012 using geostrophic velocities derived from AVISO altimetry and a new database is provided for the global ocean.

  15. A Study of the Extratropical Baroclinic Eddy Activity during Arctic Spring Onset

    NASA Astrophysics Data System (ADS)

    He, J.; Black, R. X.

    2013-12-01

    During spring, the Arctic atmospheric circulation experiences a dramatic transition, which is dominated by a shift from the winter pattern to the summer pattern in the middle and upper tropospheric circulation and a rapid surface warming north of 75N. We apply a new technique to identify the spring onset in terms of local rapid increase in the surface air temperature for 32 years from 1979 to 2010. The spring onset date exhibits strong interannual variability but no significant trend. While the whole Arctic region warms rapidly during spring onset, a critical region to the north of Siberia experiences the most dramatic warming. A composite synoptic analysis reveals a preferred circulation pattern with an anti-cyclonic circumpolar cell over the Arctic and a cyclonic cell over the east Eurasian continent, resulting in the transport of warm air into the critical warming region. A heat budget analysis shows that the warming is due to the combined effect of the large-scale circulation, baroclinic eddies, adiabatic and diabatic contributions. The baroclinic eddies play a fundamental role in this process: During the spring onset, a persistent weakening of eddy activity is observed in the North Atlantic storm track region while a packet of locally enhanced eddy activity is observed to propagate through the downstream region. As a consequence, anomalously high baroclinic eddy activity propagates eastward and, after spring onset, the eddy activity is enhanced within the north Siberian region, providing an enhanced northward heat transport into the critical region to sustain the rapid warming. To understand the detailed influence of this eddy activity, analyses of individual cyclone and anti-cyclone events will be investigated in individual case studies of spring onset to isolate different classes of spring onset events.

  16. A simple osmium post-fixation paraffin-embedment technique to identify lipid accumulation in fish liver using medaka (Oryziaslatipes) eggs and eleutheroembryos as lipid rich models.

    PubMed

    Mondon, J A; Howitt, J; Tosiano, M; Kwok, K W H; Hinton, D E

    2011-01-01

    Hepatic lipidosis is a non-specific biomarker of effect from pollution exposure in fish. Fatty liver is often misdiagnosed or overlooked in histological assessments due to the decreasing application of specific fat procedures and stains. For example, ethanol dehydration in standard paraffin processing removes lipids, leaving vacuoles of which the precise nature is unknown. Lipids can be identified using osmium post-fixation in semi-thin resin sections or transmission electron microscopy. However, both are expensive and technically demanding procedures, often not available for routine environmental risk assessment and monitoring programs. The current emphasis to reduce and refine animal toxicity testing, requires refinement of the suite of histopathological techniques currently available to maximize information gained from using fish for toxicity testing and as bio-indicators of environmental quality. This investigation has successfully modified an osmium post-fixation technique to conserve lipids in paraffin-embedded tissues using medaka (Oryzias latipes) eleutheroembryos and eggs (embryos) as lipid rich models.

  17. Large eddy simulations of compressible turbulent flows

    NASA Technical Reports Server (NTRS)

    Porter-Locklear, Freda

    1995-01-01

    An evaluation of existing models for Large Eddy Simulations (LES) of incompressible turbulent flows has been completed. LES is a computation in which the large, energy-carrying structures to momentum and energy transfer is computed exactly, and only the effect of the smallest scales of turbulence is modeled. That is, the large eddies are computed and the smaller eddies are modeled. The dynamics of the largest eddies are believed to account for most of sound generation and transport properties in a turbulent flow. LES analysis is based on an observation that pressure, velocity, temperature, and other variables are the sum of their large-scale and small-scale parts. For instance, u(i) (velocity) can be written as the sum of bar-u(i) and u(i)-prime, where bar-u(i) is the large-scale and u(i)-prime is the subgrid-scale (SGS). The governing equations for large eddies in compressible flows are obtained after filtering the continuity, momentum, and energy equations, and recasting in terms of Favre averages. The filtering operation maintains only large scales. The effects of the small-scales are present in the governing equations through the SGS stress tensor tau(ij) and SGS heat flux q(i). The mathematical formulation of the Favre-averaged equations of motion for LES is complete.

  18. Vertical eddy heat fluxes from model simulations

    NASA Technical Reports Server (NTRS)

    Stone, Peter H.; Yao, Mao-Sung

    1991-01-01

    Vertical eddy fluxes of heat are calculated from simulations with a variety of climate models, ranging from three-dimensional GCMs to a one-dimensional radiative-convective model. The models' total eddy flux in the lower troposphere is found to agree well with Hantel's analysis from observations, but in the mid and upper troposphere the models' values are systematically 30 percent to 50 percent smaller than Hantel's. The models nevertheless give very good results for the global temperature profile, and the reason for the discrepancy is unclear. The model results show that the manner in which the vertical eddy flux is carried is very sensitive to the parameterization of moist convection. When a moist adiabatic adjustment scheme with a critical value for the relative humidity of 100 percent is used, the vertical transports by large-scale eddies and small-scale convection on a global basis are equal: but when a penetrative convection scheme is used, the large-scale flux on a global basis is only about one-fifth to one-fourth the small-scale flux. Comparison of the model results with observations indicates that the results with the latter scheme are more realistic. However, even in this case, in mid and high latitudes the large and small-scale vertical eddy fluxes of heat are comparable in magnitude above the planetary boundary layer.

  19. Stratospheric eddy diffusion coefficients from tracer data

    NASA Technical Reports Server (NTRS)

    Massie, S. T.; Hunten, D. M.

    1981-01-01

    Global distributions of nitrous oxide, methane, ozone, and carbon 14 are used to estimate four sets of stratospheric eddy diffusion coefficients. A photochemical equilibrium model calculates O(3P), O(1D), H, HO2, OH, H2O2, NO, and NO2 densities, as a function of altitude, latitude, and time. The calculated O(1D), OH, and observed Cl densities are used to obtain the eddy profiles associated with the methane and nitrous oxide distributions, for altitudes between 10 and 40 km. Application of a constant flux condition to the seasonally averaged ozone data yields eddy values below 20 km. Time-dependent carbon 14 calculations produce eddy coefficients between 13 and 27 km. A composite profile is obtained by comparing the four sets of coefficients. Further, carbon 14 computations are used to test these profiles as well as those recommended in reports issued by the National Academy of Sciences in 1976 and 1979. The composite eddy profile produces the best agreement.

  20. Eddy Current, Magnetic Particle and Hardness Testing, Aviation Quality Control (Advanced): 9227.04.

    ERIC Educational Resources Information Center

    Dade County Public Schools, Miami, FL.

    This unit of instruction includes the principles of eddy current, magnetic particle and hardness testing; standards used for analyzing test results; techniques of operating equipment; interpretation of indications; advantages and limitations of these methods of testing; care and calibration of equipment; and safety and work precautions. Motion…

  1. Eddy Current Assessment of the Cold Rolled Deformation Behavior of AISI 321 Stainless Steel

    NASA Astrophysics Data System (ADS)

    Liu, Kunpeng; Zhao, Zihua; Zhang, Zheng

    2012-08-01

    Applicability of the eddy current (EC) technique in assessing martensite phase transformation during cold reduction in AISI 321 stainless steel was investigated. An empirical model based on measured EC parameters was developed for predicting the volume fraction of strain-induced martensite. Good agreement was found between the model-predicted and the experimental data.

  2. Procedure for Automated Eddy Current Crack Detection in Thin Titanium Plates

    NASA Technical Reports Server (NTRS)

    Wincheski, Russell A.

    2012-01-01

    This procedure provides the detailed instructions for conducting Eddy Current (EC) inspections of thin (5-30 mils) titanium membranes with thickness and material properties typical of the development of Ultra-Lightweight diaphragm Tanks Technology (ULTT). The inspection focuses on the detection of part-through, surface breaking fatigue cracks with depths between approximately 0.002" and 0.007" and aspect ratios (a/c) of 0.2-1.0 using an automated eddy current scanning and image processing technique.

  3. Ultrasonic and eddy current characterization of impact damage in graphite/epoxy rocket motor cases

    NASA Astrophysics Data System (ADS)

    Degtyar, Andrei D.; Pearson, Lee H.

    2000-05-01

    Impact damage sustained during the manufacturing, storage and transportation of rocket motors could lead to a catastrophic motor failure during launch. It is important to detect and characterize such damage. This paper considers the complementary use of ultrasonic and eddy current techniques for impact damage quantification. Tests have been conducted on graphite/epoxy panels of one laminate configuration representative of composite rocket motor cases. The panels were impacted with different energies under solid and edge support conditions. The damaged panels were inspected with ultrasound and eddy current in a scanning mode. Damage extent and type (delaminations, matrix cracking, and fiber breakage) were correlated with nondestructive measurements.

  4. Eddy analysis in the Eastern China Sea using altimetry data

    NASA Astrophysics Data System (ADS)

    Qin, Dandi; Wang, Jianhong; Liu, Yu; Dong, Changming

    2015-12-01

    Statistical characteristics of mesoscale eddies in the Eastern China Sea (ECS) are analyzed using altimetry sea surface height anomaly (SSHA) data from 1993 to 2010. A velocity geometry-based automated eddy detection scheme is employed to detect eddies from the SSHA data to generate an eddy data set. About 1,096 eddies (one lifetime of eddies is counted as one eddy) with a lifetime longer than or equal to 4 weeks are identified in this region. The average lifetime and radius of eddies are 7 weeks and 55 km, respectively, and there is no significant difference between cyclonic eddies (CEs) and anticyclonic eddies (AEs) in this respect. Eddies' lifetimes are generally longer in deep water than in shallow water. Most eddies propagate northeastward along the Kuroshio (advected by the Kuroshio), with more CEs generated on its western side and AEs on its eastern side. The variation of the Kuroshio transport is one of the major mechanisms for eddy genesis, however the generation of AEs on the eastern side of the Kuroshio (to the open ocean) is also subject to other factors, such as the wind stress curl due to the presence of the Ryukyu Islands and the disturbance from the open ocean.

  5. Solitonlike solutions in loop current eddies

    NASA Technical Reports Server (NTRS)

    Nakamoto, Shoichiro

    1989-01-01

    The application of the nonlinear quasi-geostrophic equations to an isolated eddy in the western continental slope region in the Gulf of Mexico is examined for a two-layer ocean model with bottom topography. In the linear limit, solutions are topographic nondispersive waves. Form-preserving solutions, or solitons, have been found. The solution is shown to be a limiting form for a nonlinear dispersive system propagating northward along the topographic waveguide in the western continental slope region in the Gulf of Mexico. Using satellite-tracked drifter data, a linear relationship is found between the amplitude of the deduced stream function of the eddy and its observed translational velocity over the continental slope, which supports the hypothesis that some mesoscale eddies interacting with the continental slope behave as solitons.

  6. Combination of Fluorescence In Situ Hybridization with Staining Techniques for Cell Viability and Accumulation of PHA and polyP in Microorganisms in Complex Microbial Systems

    NASA Astrophysics Data System (ADS)

    Nielsen, Jeppe Lund; Kragelund, Caroline; Nielsen, Per Halkjær

    Fluorescence in situ hybridization (FISH) can be combined with a number of staining techniques to reveal the relationships between the microorganisms and their function in complex microbial systems with a single-cell resolution. In this chapter, we have focused on staining methods for intracellular storage compounds (polyhydroxyalkanoates, polyphosphate) and a measure for cell viability, reduction of the tetrazolium-based redox stain CTC. These protocols are optimized for the study of microorganisms in waste-water treatment (activated sludge and biofilms), but they may also be used with minor modifications in many other ecosystems.

  7. Estimation of rainfall interception in grassland using eddy flux measurements

    NASA Astrophysics Data System (ADS)

    Maruyama, A.; Miyazawa, Y.; Inoue, A.

    2014-12-01

    Rainfall interception plays an important role in the water cycle in natural ecosystems. Interception by the forest canopies have been widely observed or estimated over various ecosystems, such as tropical rainforest, evergreen forest and deciduous forest. However interception by the short canopies, e.g. shrubby plant, grassland and crop, has been rarely observed since it has been difficult to obtain reliable precipitation measurements under the canopy. In this study, we estimated monthly and annual rainfall interception in grassland using evapotranspiration data of eddy flux measurements. Experiments were conducted in grassland (Italian ryegrass) from 2010 to 2012 growing season in Kumamoto, Japan. Evapotranspiration (latent heat flux) were observed throughout the year based on the eddy covariance technique. A three dimensional sonic anemometer and an open path CO2/H2O analyzer were used to calculate 30 min flux. Other meteorological factors, such as air temperature, humidity and solar radiation, were also observed. Rainfall interception was estimated as follows. 1) Using evapotranspiration data during dry period, environmental response of surface conductance (gc) was inversely calculated based on the big-leaf model. 2) Evapotranspiration without interception during precipitation period was estimated using above model and environmental response of gc. 3) Assuming that evaporation of intercepted rainfall is equal to the difference in evapotranspiration between above estimation and actual measurements, rainfall interception was estimated over experimental period. The account of rainfall interception in grassland using this technique will be presented at the meeting.

  8. Anticyclonic eddy energy and pathways in the Algerian basin (1993-2007)

    NASA Astrophysics Data System (ADS)

    Pessini, Federica; Perilli, Angelo; Olita, Antonio

    2016-04-01

    use in the study area. This automated method allowed the investigation of mesoscale eddy variability using several years (1993-2007) of satellite altimetry observations. To verify the reliability of the technique, we compared the eddy pathways derived from the application of the modified Penven method with independent observations. Preliminary results suggest that AEs, moving anticlockwise within the sub-basin, complete as many as two or three laps, depending on their lifetime, following the Algerian Gyre path. We suppose that AEs acquire kinetic energy from the Algerian current, occasionally in sufficient magnitude to cause their detachment. This phenomenon mainly takes place near the Sardinian Channel. Eddies formed on the thermal front, called Frontal Anticyclonic Eddies (FAEs), remain localized in the northern part of the sub-basin and have lower energy and shorter life than AEs. They usually don't interact with AEs. Basic statistics on eddy trajectories and energy characteristics allow the evaluation of these mesoscale structures' relevance of on (sub-) basin circulation.

  9. An advanced synthetic eddy method for the computation of aerofoil-turbulence interaction noise

    NASA Astrophysics Data System (ADS)

    Kim, Jae Wook; Haeri, Sina

    2015-04-01

    This paper presents an advanced method to synthetically generate flow turbulence via an inflow boundary condition particularly designed for three-dimensional aeroacoustic simulations. The proposed method is virtually free of spurious noise that might arise from the synthetic turbulence, which enables a direct calculation of propagated sound waves from the source mechanism. The present work stemmed from one of the latest outcomes of synthetic eddy method (SEM) derived from a well-defined vector potential function creating a divergence-free velocity field with correct convection speeds of eddies, which in theory suppresses pressure fluctuations. In this paper, a substantial extension of the SEM is introduced and systematically optimised to create a realistic turbulence field based on von Kármán velocity spectra. The optimised SEM is then combined with a well-established sponge-layer technique to quietly inject the turbulent eddies into the domain from the upstream boundary, which results in a sufficiently clean acoustic field. Major advantages in the present approach are: a) that genuinely three-dimensional turbulence is generated; b) that various ways of parametrisation can be created to control/characterise the randomly distributed eddies; and, c) that its numerical implementation is efficient as the size of domain section through which the turbulent eddies should be passing can be adjusted and minimised. The performance and reliability of the proposed SEM are demonstrated by a three-dimensional simulation of aerofoil-turbulence interaction noise.

  10. Evaluation and field validation of Eddy-Current array probes for steam generator tube inspection

    SciTech Connect

    Dodd, C.V.; Pate, J.R.

    1996-07-01

    The objective of the Improved Eddy-Current ISI for Steam Generator Tubing program is to upgrade and validate eddy-current inspections, including probes, instrumentation, and data processing techniques for inservice inspection of new, used, and repaired steam generator tubes; to improve defect detection, classification, and characterization as affected by diameter and thickness variations, denting, probe wobble, tube sheet, tube supports, copper and sludge deposits, even when defect types and other variables occur in combination; to transfer this advanced technology to NRC`s mobile NDE laboratory and staff. This report describes the design of specialized high-speed 16-coil eddy-current array probes. Both pancake and reflection coils are considered. Test results from inspections using the probes in working steam generators are given. Computer programs developed for probe calculations are also supplied.

  11. Development and Application of Wide Bandwidth Magneto-Resistive Sensor Based Eddy Current Probe

    NASA Technical Reports Server (NTRS)

    Wincheski, Russell A.; Simpson, John

    2010-01-01

    The integration of magneto-resistive sensors into eddy current probes can significantly expand the capabilities of conventional eddy current nondestructive evaluation techniques. The room temperature solid-state sensors have typical bandwidths in the megahertz range and resolutions of tens of microgauss. The low frequency sensitivity of magneto-resistive sensors has been capitalized upon in previous research to fabricate very low frequency eddy current sensors for deep flaw detection in multilayer conductors. In this work a modified probe design is presented to expand the capabilities of the device. The new probe design incorporates a dual induction source enabling operation from low frequency deep flaw detection to high frequency high resolution near surface material characterization. Applications of the probe for the detection of localized near surface conductivity anomalies are presented. Finite element modeling of the probe is shown to be in good agreement with experimental measurements.

  12. Classification of eddy current signals using fuzzy logic and neural networks

    NASA Astrophysics Data System (ADS)

    Ewald, Hartmut; Stieper, Michael

    1996-11-01

    The nondestructive eddy current methods are commonly used for automated defect inspection to detect cracks in materials which are used in cars, power and aircraft industries. The eddy current signal from a infinitely long crack can be classified with the help of the fuzzy logic and the neural network techniques. A rule based fuzzy logic classification guarantees better results than fuzzy-cluster- means algorithm, because the classification results can be increased in this case step by step. By using the neural network for the classification of the crack signals it is very important to have a good 'learning pattern.' The advantage of time-delay networks in this application is the fact that the network can 'learn' the eddy-current time signal; a signal preprocessing is not necessary.

  13. Casimir Interaction from Magnetically Coupled Eddy Currents

    SciTech Connect

    Intravaia, Francesco; Henkel, Carsten

    2009-09-25

    We study the quantum and thermal fluctuations of eddy (Foucault) currents in thick metallic plates. A Casimir interaction between two plates arises from the coupling via quasistatic magnetic fields. As a function of distance, the relevant eddy current modes cross over from a quantum to a thermal regime. These modes alone reproduce previously discussed thermal anomalies of the electromagnetic Casimir interaction between good conductors. In particular, they provide a physical picture for the Casimir entropy whose nonzero value at zero temperature arises from a correlated, glassy state.

  14. Visualization and analysis of eddies in a global ocean simulation

    SciTech Connect

    Williams, Sean J; Hecht, Matthew W; Petersen, Mark; Strelitz, Richard; Maltrud, Mathew E; Ahrens, James P; Hlawitschka, Mario; Hamann, Bernd

    2010-10-15

    Eddies at a scale of approximately one hundred kilometers have been shown to be surprisingly important to understanding large-scale transport of heat and nutrients in the ocean. Due to difficulties in observing the ocean directly, the behavior of eddies below the surface is not very well understood. To fill this gap, we employ a high-resolution simulation of the ocean developed at Los Alamos National Laboratory. Using large-scale parallel visualization and analysis tools, we produce three-dimensional images of ocean eddies, and also generate a census of eddy distribution and shape averaged over multiple simulation time steps, resulting in a world map of eddy characteristics. As expected from observational studies, our census reveals a higher concentration of eddies at the mid-latitudes than the equator. Our analysis further shows that mid-latitude eddies are thicker, within a range of 1000-2000m, while equatorial eddies are less than 100m thick.

  15. Application of finite element models to eddy current probe design for aircraft inspection

    NASA Astrophysics Data System (ADS)

    Sharma, Sarit

    Eddy current nondestructive testing (NDT) methods are used extensively in the inspection of aircraft structures. Improvements and innovations in probe design are constantly required for detection of flaws in complex multilayer aircraft structures. This thesis investigates alternate designs of eddy current probes for addressing some of these problems. An important aspect of probe design is the capability to simulate probe performance. Numerical computation and visualization of the electromagnetic fields can provide valuable insight into the design of new probes. Finite element methods have been used in this dissertation to numerically compute the electromagnetic fields associated with the probe coils, and the eddy current probe signals. A major contribution of this thesis is development of techniques to reduce the computer resource requirement in the finite element modeling: of the eddy current phenomenon. The first flaw detection problem is addressed by focusing the flux of the probe using active compensation techniques. A novel eddy current probe using a combination of coils is proposed and studied using: the 3D model simulation. The probe consists of two current carrying concentric coils to detect flaws closer to the sample edges. Detection of defects in second and third layer of samples has been demonstrated using: the remote field eddy current (RFEC) method. In the RFEC method the pickup coils are located in the far field region which leads to a large volume to be modeled numerically with large number of elements. A method involving partitioning the volume in the 3D finite element model is demonstrated for the RFEC detection of defects. Magneto-optic/eddy current imaging (MOI) techniques have shown considerable promise in the detection of corrosion in the second layer. MOI is a nondestructive testing method currently in use in aircraft frame inspection and it involves optically sensing the magnetic field induced by the eddy currents in the test sample. A

  16. On physical interpretation of two dimensional time-correlations regarding time delay velocities and eddy shaping

    SciTech Connect

    Fedorczak, N.; Manz, P.; Thakur, S. C.; Xu, M.; Tynan, G. R.; Xu, G. S.; Liu, S. C.

    2012-12-15

    Time delay estimation (TDE) techniques are frequently used to estimate the flow velocity from fluctuating measurements. Tilted structures carried by the flow lead to misinterpretation of the time delays in terms of velocity direction and amplitude. It affects TDE measurements from probes, and is also intrinsically important for beam emission spectroscopy and gas puff imaging measurements. Local eddy shapes estimated from 2D fluctuating field are necessary to gain a more accurate flow estimate from TDE, as illustrated by Langmuir probe array measurements. A least square regression approach is proposed to estimate both flow field and shaping parameters. The technique is applied to a test case built from numerical simulation of interchange fluctuations. The local eddy shape does not only provide corrections for the velocity field but also quantitative information about the statistical interaction mechanisms between local eddies and E Multiplication-Sign B flow shear. The technique is then tested on gaz puff imaging data collected at the edge of EAST tokamak plasmas. It is shown that poloidal asymmetries of the fluctuation fields-velocity and eddy shape-are consistent at least qualitatively with a ballooning type of turbulence immersed in a radially sheared equilibrium flow.

  17. Ultra High Precision Laser Monitor for Oxygen Eddy Flux Measurements

    NASA Astrophysics Data System (ADS)

    Zahniser, M. S.; Nelson, D. D.; Roscioli, J. R.; Herndon, S. C.; McManus, J. B.; Jervis, D.

    2015-12-01

    Atmospheric oxygen provides one of the most powerful tracers to study the carbon cycle through its close interaction with carbon dioxide. Keeling and co-workers demonstrated this at the global scale by using small variations in atmospheric oxygen content to disentangle oceanic and terrestrial carbon sinks. It would be very exciting to apply similar ideas at the ecosystem level to improve our understanding of biosphere-atmosphere exchange and our ability to predict the response of the biosphere and atmosphere to climate change. The eddy covariance technique is perhaps the most effective approach available to quantify the exchange of gases between these spheres. Therefore, eddy covariance flux measurements of oxygen would be extremely valuable. However, this requires a fast response (0.1 seconds), high relative precision (0.001% or 10 per meg) oxygen sensor. We report recent progress in developing such a sensor using a high resolution visible laser to probe the oxygen A-band electronic transition. This sensor will enable oxygen flux measurements using eddy covariance. In addition, we will incorporate a second laser in this instrument to simultaneously determine the fluxes of oxygen, carbon dioxide and water vapor within the same sampling cell. This will provide a direct, real time measurement of the ratio of the flux of oxygen to that of carbon dioxide. This ratio is expected to vary on short time scales and small spatial scales due to the differing stoichiometry of processes producing and consuming carbon dioxide. Thus measuring the variations in the ratio of oxygen and carbon dioxide fluxes will provide mechanistic information to improve our understanding of the crucial exchange of carbon between the atmosphere and biosphere.

  18. Ultra High Precision Laser Monitor for Oxygen Eddy Flux Measurements

    NASA Astrophysics Data System (ADS)

    Nelson, David; Herndon, Scott; McManus, Barry; Roscioli, Rob; Jervis, Dylan; Zahniser, Mark

    2016-04-01

    Atmospheric oxygen provides one of the most powerful tracers to study the carbon cycle through its close interaction with carbon dioxide. Keeling and co-workers demonstrated this at the global scale by using small variations in atmospheric oxygen content to disentangle oceanic and terrestrial carbon sinks. It would be very exciting to apply similar ideas at the ecosystem level to improve our understanding of biosphere-atmosphere exchange and our ability to predict the response of the biosphere and atmosphere to climate change. The eddy covariance technique is perhaps the most effective approach available to quantify the exchange of gases between these spheres. Therefore, eddy covariance flux measurements of oxygen would be extremely valuable. However, this requires a fast response (0.1 seconds), high relative precision (0.001% or 10 per meg) oxygen sensor. We report recent progress in developing such a sensor using a high resolution visible laser to probe the oxygen A-band electronic transition. We have demonstrated precision of 1 ppmv or 5 per meg for a 100 second measurement duration. This sensor will enable oxygen flux measurements using eddy covariance. In addition, we will incorporate a second laser in this instrument to simultaneously determine the fluxes of oxygen, carbon dioxide and water vapor within the same sampling cell. This will provide a direct, real time measurement of the ratio of the flux of oxygen to that of carbon dioxide. This ratio is expected to vary on short time scales and small spatial scales due to the differing stoichiometry of processes producing and consuming carbon dioxide. Thus measuring the variations in the ratio of oxygen and carbon dioxide fluxes will provide mechanistic information to improve our understanding of the crucial exchange of carbon between the atmosphere and biosphere.

  19. Combined FTIR-micrometeorological techniques for long term measurements of greenhouse gas fluxes from agriculture

    NASA Astrophysics Data System (ADS)

    Petersen, A. K.; Griffith, D.; Harvey, M.; Naylor, T.; Smith, M.

    2009-04-01

    The exchange of trace gases between the biosphere and the atmosphere affects the atmospheric concentrations of gases such as methane, carbon dioxide, nitrous oxide, carbon monoxide, ammonia, volatile organic compounds, nitrogen dioxide and others. The quantification of the exchange between a biogenic system and the atmosphere is necessary for the evaluation of the impact of these interactions. This is of special interest for agricultural systems which can be sources or sinks of trace gases, and the measurement of the fluxes is necessary when evaluating both the environmental impact of agricultural activities and the impact of atmospheric pollution on agricultural production and sustainability. With the exception of CO2, micrometeorological measurements of the fluxes of greenhouse gases from agricultural activities are still mostly possible only in campaign mode due to the complexity and logistical requirements of the existing measurement techniques. This limitation precludes studies of fluxes which run for longer periods, for example over full seasonal or growing cycles for both animal- and crop-based agriculture. We have developed an instrument system for long-term flux measurements through a combination of micrometeorological flux measurement techniques such as Relaxed Eddy Accumulation (REA) and Flux-Gradient (FG) with the high precision multi-species detection capabilities of FTIR spectroscopy. The combined technique is capable of simultaneous flux measurements of N2O, CH4 and CO2 at paddock to regional scales continuously, over longer terms (months, seasonal cycles, years). The system was tested on a 3 weeks field campaign in NSW, Australia on a flat, homogeneous circular grass paddock with grazing cattle. The flux of the atmospheric trace gas CO2 was measured with three different micrometeorological techniques: Relaxed Eddy Accumulation, Flux-Gradient, and Eddy Correlation. Simultaneously, fluxes of CH4 and N2O were measured by REA and FG technique.

  20. Gulf Stream eddies - Recent observations in the western Sargasso Sea.

    NASA Technical Reports Server (NTRS)

    Richardson, P. L.; Knauss, J. A.; Strong, A. E.

    1973-01-01

    A cyclonic Gulf Stream eddy was observed in the western Sargasso Sea by satellite infrared measurements and later confirmed by ship measurements. Fourteen months of observations indicate that the eddy moved southwestward at an average rate of 1 mile per day. The evidence suggests that the eddy was absorbed by the Gulf Stream off Florida.

  1. The influence of eddy currents on magnetic actuator performance

    NASA Technical Reports Server (NTRS)

    Zmood, R. B.; Anand, D. K.; Kirk, J. A.

    1987-01-01

    The present investigation of the effects of eddy currents on EM actuators' transient performance notes that a transfer function representation encompassing a first-order model of the eddy current influence can be useful in control system analysis. The method can be extended to represent the higher-order effects of eddy currents for actuators that cannot be represented by semiinfinite planes.

  2. Eddy-Current Inspection Of Graphite-Fiber Composites

    NASA Technical Reports Server (NTRS)

    Workman, G. L.; Bryson, C. C.

    1993-01-01

    NASA technical memorandum describes initial research on, and proposed development of, automated system for nondestructive eddy-current inspection of parts made of graphite-fiber/epoxy-matrix composite materials. Sensors in system E-shaped or U-shaped eddy-current probes like those described in "Eddy-Current Probes For Inspecting Graphite-Fiber Composites" (MFS-26129).

  3. An expert system for analyzing eddy current measurements

    SciTech Connect

    Levy, A.J.; Oppenlander, J.E.; Brudnoy, D.M.; Englund, J.M.; Loomis, K.C.

    1991-12-31

    A method and apparatus (called DODGER) analyzes eddy current data for heat exchanger tubes or any other metallic object. DODGER uses an expert system to analyze eddy current data by reasoning with uncertainty and pattern recognition. The expert system permits, DODGER to analyze eddy current data intelligently, an obviate operator uncertainty by analyzing the data in a uniform and consistent manner.

  4. Comparison of characteristics of hydrographic structures in Aleutian eddies

    NASA Astrophysics Data System (ADS)

    Saito, R.; Yasuda, I.; Komatsu, K.; Ishiyama, H.; Ueno, H.; Onishi, H.; Setou, T.; Shimizu, M.

    2014-12-01

    Mesoscale anticylonic eddies formed in the Alaskan Stream region south of the Aleutian Islands between the 180° meridian and about 170°E are called Aleutian eddies. Many of these eddies propagate in the southwestward direction, and often reach western subarctic gyre. The objective of present study is to compare hydrographic structures of three Aleutian eddies with distinctive propagation paths and evaluate potential impacts of physical environment along the paths on those eddies. We observed three eddies during the summers of 2010 and 2012, in which two of the eddies (A and C) were observed west of 172°E and one (B) east of 172°E. In each eddy, a subsurface cold dichothermal water (3.0-4.0°C) was observed to be located above a subsurface warm mesothermal water (4.0-4.5°C), and the two waters were separated by 26.5-26.6σθ isopycnals. The minimum temperature in the dichothermal water at ~26.4σθ was lower in the eddies A and C (2.8-2.9°C) than in the eddy B (3.2°C). This difference could be ascribed to eddy history of wintertime cooling and influence of warm Alaskan Stream. The Aleutian eddies were originated from the Alaskan Stream, and propagated westward after isolation from the Alaskan Stream. Winter cooling could make the dichothermal water cooler for eddies which were isolated for longer time. This is the case for the eddy A. The particle tracking experiments using the 1/10° eddy resolving ocean model called FRA-ROMS (Fisheries Research Agency of Japan) demonstrated that the water within the eddy was mostly originated from cold water around the propagation path in the early spring, suggesting continuous cooling of dichothermal water after the winter-time cooling. The eddy B stayed near the Alaskan Stream which could provide warm water to the eddy, to make less cold dichothermal water. The particle tacking experiments using FRA-ROMS confirmed that the water in the eddy was mainly originated from warm Alaskan Stream in the early spring, suggesting

  5. The turbulent cascade of individual eddies

    NASA Astrophysics Data System (ADS)

    Huertas-Cerdeira, Cecilia; Lozano-Durán, Adrián; Jiménez, Javier

    2014-11-01

    The merging and splitting processes of Reynolds-stress carrying structures in the inertial range of scales are studied through their time-resolved evolution in channels at Reλ = 100 - 200 . Mergers and splits coexist during the whole life of the structures, and are responsible for a substantial part of their growth and decay. Each interaction involves two or more eddies and results in little overall volume loss or gain. Most of them involve a small eddy that merges with, or splits from, a significantly larger one. Accordingly, if merge and split indexes are respectively defined as the maximum number of times that a structure has merged from its birth or will split until its death, the mean eddy volume grows linearly with both indexes, suggesting an accretion process rather than a hierarchical fragmentation. However, a non-negligible number of interactions involve eddies of similar scale, with a second probability peak of the volume of the smaller parent or child at 0.3 times that of the resulting or preceding structure. Funded by the Multiflow project of the ERC.

  6. Eddy current sensing of intermetallic composite consolidation

    NASA Technical Reports Server (NTRS)

    Dharmasena, Kumar P.; Wadley, Haydn N. G.

    1991-01-01

    A finite element method is used to explore the feasibility and optimization of a probe-type eddy current sensor for determining the thickness of plate specimens during a hot isostatic pressing cycle. The dependence of the sensor's impedance upon sample-sensor separation in the high frequency limit is calculated, and factors that maximize sensitivity to the final stages of densification are identified.

  7. Large-Eddy Simulation and Multigrid Methods

    SciTech Connect

    Falgout,R D; Naegle,S; Wittum,G

    2001-06-18

    A method to simulate turbulent flows with Large-Eddy Simulation on unstructured grids is presented. Two kinds of dynamic models are used to model the unresolved scales of motion and are compared with each other on different grids. Thereby the behavior of the models is shown and additionally the feature of adaptive grid refinement is investigated. Furthermore the parallelization aspect is addressed.

  8. Understanding positive feedback between PNA and synoptic eddies by eddy structure decomposition method

    NASA Astrophysics Data System (ADS)

    Zhou, Fang; Ren, Hong-Li; Xu, Xiao-Feng; Zhou, You

    2016-08-01

    In the upper troposphere during winter, positive synoptic eddy (SE) feedback plays an indispensible role in maintaining the Pacific-North American (PNA) pattern that dominates climate variability on inter-annual timescales over the North Pacific and downstream regions. This study shows that the eddy forcing, induced by eddy-vorticity (EV) fluxes, is not only in-phase with, but also downstream to the PNA pattern in terms of its northeast Pacific lobe. We employ the eddy structure decomposition method to understand such an observed PNA-SEs feedback, and propose a kinematic mechanism that can depict dynamical processes associated with the eddy structure change and its induced positive eddy feedback relative to the PNA flow pattern. With this method, the winter-mean PNA-related SE structures are separated into climatological (basic) and anomalous SE structures, and these two parts can be used to represent the changes in SE structure in a statistical sense and then to calculate the EV fluxes in order to further elucidate the feedback mechanism. It is demonstrated that, on one hand, the winter-mean PNA flow tends to systematically deform the structures of SEs and induce anomalous EV fluxes, and these winter-mean EV fluxes primarily converge into the PNA cyclonic center, which, in return enhances the PNA flow. On the other hand, the PNA-related northeast Pacific flow is featured by a stronger zonal wind shear in the east than the west, which can induce larger zonal-slanting eddy structure change and then stronger meridional EV fluxes that converge to form downstream feedback. This kinematic mechanism may help to deeply understand the dynamical eddy feedback between the low-frequency PNA flow and high-frequency SEs.

  9. Obituary: John Allen Eddy (1931-2009)

    NASA Astrophysics Data System (ADS)

    Gingerich, Owen

    2011-12-01

    Jack Eddy, who was born 25 March 1931 in Pawnee City in southeastern Nebraska, died after a long battle with cancer in Tucson, Arizona, on 10 June 2009. Best known for his work on the long-term instability of the sun, described in a landmark paper in Science titled "The Maunder Minimum," he also deserves recognition as one of the triumvirate who founded the Historical Astronomy Division of the AAS. His father ran a cooperative farm store where Jack worked as a teenager; his parents were of modest means and there were concerns whether he could afford college, but one of the state senators, also from Pawnee City, nominated him for the U.S. Naval Academy. A course in celestial navigation gave him a love of the sky. After graduation in 1953, he served four years on aircraft carriers in the Pacific during the Korean War and then as a navigator and operations officer on a destroyer in the Persian Gulf. In 1957, he left the Navy and entered graduate school at the University of Colorado in Boulder, where in 1962 he received a Ph.D. in astro-geophysics. His thesis, supervised by Gordon Newkirk, dealt with light scattering in the upper atmosphere, based on data from stratospheric balloon flights. He then worked as teacher and researcher at the High Altitude Observatory in Boulder. Always adventuresome and willing to explore new frontiers, on his own time Eddy examined an Amerindian stone circle in the Big Horn mountains of Wyoming, a so-called medicine wheel, concluding that there were alignments with both the solstitial sun and Aldebaran. His conjectures became a cover story on Science magazine in June of 1974. In 1971 Jack privately reproduced for his friends a small collection of his own hilarious cartoons titled "Job Opportunities for Out-of-work Astronomers," with an abstract beginning, "Contrary to popular belief, a PhD in Astronomy/Astrophysics need not be a drawback in locating work in this decade." For example, under merchandising, a used car salesman advertises

  10. Large eddy simulation of mechanical mixing in anaerobic digesters.

    PubMed

    Wu, Binxin

    2012-03-01

    A comprehensive study of anaerobic digestion requires an advanced turbulence model technique to accurately predict mixing flow patterns because the digestion process that involves mass transfer between anaerobes and their substrates is primarily dependent on detailed information about the fine structure of turbulence in the digesters. This study presents a large eddy simulation (LES) of mechanical agitation of non-Newtonian fluids in anaerobic digesters, in which the sliding mesh method is used to characterize the impeller rotation. The three subgrid scale (SGS) models investigated are: (i) Smagorinsky-Lilly model, (ii) wall-adapting local eddy-viscosity model, and (iii) kinetic energy transport (KET) model. The simulation results show that the three SGS models produce very similar flow fields. A comparison of the simulated and measured axial velocities indicates that the LES profile shapes are in general agreement with the experimental data but they differ markedly in velocity magnitudes. A check of impeller power and flow numbers demonstrates that all the SGS models give excellent predictions, with the KET model performing the best. Moreover, the performance of six Reynolds-averaged Navier-Stokes turbulence models are assessed and compared with the LES results. PMID:22038563

  11. Coupled circuit numerical analysis of eddy currents in an open MRI system.

    PubMed

    Akram, Md Shahadat Hossain; Terada, Yasuhiko; Keiichiro, Ishi; Kose, Katsumi

    2014-08-01

    We performed a new coupled circuit numerical simulation of eddy currents in an open compact magnetic resonance imaging (MRI) system. Following the coupled circuit approach, the conducting structures were divided into subdomains along the length (or width) and the thickness, and by implementing coupled circuit concepts we have simulated transient responses of eddy currents for subdomains in different locations. We implemented the Eigen matrix technique to solve the network of coupled differential equations to speed up our simulation program. On the other hand, to compute the coupling relations between the biplanar gradient coil and any other conducting structure, we implemented the solid angle form of Ampere's law. We have also calculated the solid angle for three dimensions to compute inductive couplings in any subdomain of the conducting structures. Details of the temporal and spatial distribution of the eddy currents were then implemented in the secondary magnetic field calculation by the Biot-Savart law. In a desktop computer (Programming platform: Wolfram Mathematica 8.0®, Processor: Intel(R) Core(TM)2 Duo E7500 @ 2.93GHz; OS: Windows 7 Professional; Memory (RAM): 4.00GB), it took less than 3min to simulate the entire calculation of eddy currents and fields, and approximately 6min for X-gradient coil. The results are given in the time-space domain for both the direct and the cross-terms of the eddy current magnetic fields generated by the Z-gradient coil. We have also conducted free induction decay (FID) experiments of eddy fields using a nuclear magnetic resonance (NMR) probe to verify our simulation results. The simulation results were found to be in good agreement with the experimental results. In this study we have also conducted simulations for transient and spatial responses of secondary magnetic field induced by X-gradient coil. Our approach is fast and has much less computational complexity than the conventional electromagnetic numerical simulation

  12. Coupled circuit numerical analysis of eddy currents in an open MRI system

    NASA Astrophysics Data System (ADS)

    Akram, Md. Shahadat Hossain; Terada, Yasuhiko; Keiichiro, Ishi; Kose, Katsumi

    2014-08-01

    We performed a new coupled circuit numerical simulation of eddy currents in an open compact magnetic resonance imaging (MRI) system. Following the coupled circuit approach, the conducting structures were divided into subdomains along the length (or width) and the thickness, and by implementing coupled circuit concepts we have simulated transient responses of eddy currents for subdomains in different locations. We implemented the Eigen matrix technique to solve the network of coupled differential equations to speed up our simulation program. On the other hand, to compute the coupling relations between the biplanar gradient coil and any other conducting structure, we implemented the solid angle form of Ampere’s law. We have also calculated the solid angle for three dimensions to compute inductive couplings in any subdomain of the conducting structures. Details of the temporal and spatial distribution of the eddy currents were then implemented in the secondary magnetic field calculation by the Biot-Savart law. In a desktop computer (Programming platform: Wolfram Mathematica 8.0®, Processor: Intel(R) Core(TM)2 Duo E7500 @ 2.93 GHz; OS: Windows 7 Professional; Memory (RAM): 4.00 GB), it took less than 3 min to simulate the entire calculation of eddy currents and fields, and approximately 6 min for X-gradient coil. The results are given in the time-space domain for both the direct and the cross-terms of the eddy current magnetic fields generated by the Z-gradient coil. We have also conducted free induction decay (FID) experiments of eddy fields using a nuclear magnetic resonance (NMR) probe to verify our simulation results. The simulation results were found to be in good agreement with the experimental results. In this study we have also conducted simulations for transient and spatial responses of secondary magnetic field induced by X-gradient coil. Our approach is fast and has much less computational complexity than the conventional electromagnetic numerical

  13. Coupled circuit numerical analysis of eddy currents in an open MRI system.

    PubMed

    Akram, Md Shahadat Hossain; Terada, Yasuhiko; Keiichiro, Ishi; Kose, Katsumi

    2014-08-01

    We performed a new coupled circuit numerical simulation of eddy currents in an open compact magnetic resonance imaging (MRI) system. Following the coupled circuit approach, the conducting structures were divided into subdomains along the length (or width) and the thickness, and by implementing coupled circuit concepts we have simulated transient responses of eddy currents for subdomains in different locations. We implemented the Eigen matrix technique to solve the network of coupled differential equations to speed up our simulation program. On the other hand, to compute the coupling relations between the biplanar gradient coil and any other conducting structure, we implemented the solid angle form of Ampere's law. We have also calculated the solid angle for three dimensions to compute inductive couplings in any subdomain of the conducting structures. Details of the temporal and spatial distribution of the eddy currents were then implemented in the secondary magnetic field calculation by the Biot-Savart law. In a desktop computer (Programming platform: Wolfram Mathematica 8.0®, Processor: Intel(R) Core(TM)2 Duo E7500 @ 2.93GHz; OS: Windows 7 Professional; Memory (RAM): 4.00GB), it took less than 3min to simulate the entire calculation of eddy currents and fields, and approximately 6min for X-gradient coil. The results are given in the time-space domain for both the direct and the cross-terms of the eddy current magnetic fields generated by the Z-gradient coil. We have also conducted free induction decay (FID) experiments of eddy fields using a nuclear magnetic resonance (NMR) probe to verify our simulation results. The simulation results were found to be in good agreement with the experimental results. In this study we have also conducted simulations for transient and spatial responses of secondary magnetic field induced by X-gradient coil. Our approach is fast and has much less computational complexity than the conventional electromagnetic numerical simulation

  14. Projected changes to Tasman Sea eddies in a future climate

    NASA Astrophysics Data System (ADS)

    Oliver, Eric C. J.; O'Kane, Terence J.; Holbrook, Neil J.

    2015-11-01

    The Tasman Sea is a hot spot of ocean warming, that is linked to the increased poleward influence of the East Australian Current (EAC) over recent decades. Specifically, the EAC produces mesoscale eddies which have significant impacts on the physical, chemical, and biological properties of the Tasman Sea. To effectively consider and explain potential eddy changes in the next 50 years, we use high-resolution dynamically downscaled climate change simulations to characterize the projected future marine climate and mesoscale eddies in the Tasman Sea through the 2060s. We assess changes in the marine climate and the eddy field using bulk statistics and by detecting and tracking individual eddies. We find that the eddy kinetic energy is projected to increase along southeast Australia. In addition, we find that eddies in the projected future climate are composed of a higher proportion of anticyclonic eddies in this region and that these eddies are longer lived and more stable. This amounts to nearly a doubling of eddy-related southward temperature transport in the upper 200 m of the Tasman Sea. These changes are concurrent with increases in baroclinic and barotropic instabilities focused around the EAC separation point. This poleward transport and increase in eddy activity would be expected to also increase the frequency of sudden warming events, including ocean temperature extremes, with potential impacts on marine fisheries, aquaculture, and biodiversity off Tasmania's east coast, through direct warming or competition/predation from invasive migrating species.

  15. Biogeochemical properties of eddies in the California Current System

    NASA Astrophysics Data System (ADS)

    Chenillat, Fanny; Franks, Peter J. S.; Combes, Vincent

    2016-06-01

    The California Current System (CCS) has intense mesoscale activity that modulates and exports biological production from the coastal upwelling system. To characterize and quantify the ability of mesoscale eddies to affect the local and regional planktonic ecosystem of the CCS, we analyzed a 10 year-long physical-biological model simulation, using eddy detection and tracking to isolate the dynamics of cyclonic and anticyclonic eddies. As they propagate westward across the shelf, cyclonic eddies efficiently transport coastal planktonic organisms and maintain locally elevated production for up to 1 year (800 km offshore). Anticyclonic eddies, on the other hand, have a limited impact on local production over their ~6 month lifetime as they propagate 400 km offshore. At any given time ~8% of the model domain was covered by eddy cores. Though the eddies cover a small area, they explain ~50 and 20% of the transport of nitrate and plankton, respectively.

  16. Do East Australian Current anticyclonic eddies leave the Tasman Sea?

    NASA Astrophysics Data System (ADS)

    Pilo, Gabriela S.; Oke, Peter R.; Rykova, Tatiana; Coleman, Richard; Ridgway, Ken

    2015-12-01

    Using satellite altimetry and high-resolution model output we analyze the pathway of large, long-lived anticyclonic eddies that originate near the East Australian Current (EAC) separation point. We show that 25-30% of these eddies propagate southward, around Tasmania, leave the Tasman Sea, and decay in the Great Australian Bight. This pathway has not been previously documented owing to poor satellite sampling off eastern Tasmania. As eddies propagate southward, they often "stall" for several months at near-constant latitude. Along the pathway eddies become increasingly barotropic. Eddy intensity is primarily influenced by merging with other eddies and a gradual decay otherwise. Surface temperature anomaly associated with anticyclonic eddies changes as they propagate, while surface salinity anomaly tends to remain relatively unchanged as they propagate.

  17. Net ecosystem production: A comprehensive measure of net carbon accumulation by ecosystems

    USGS Publications Warehouse

    Randerson, J.T.; Chapin, F. S.; Harden, J.W.; Neff, J.C.; Harmon, M.E.

    2002-01-01

    The conceptual framework used by ecologists and biogeochemists must allow for accurate and clearly defined comparisons of carbon fluxes made with disparate techniques across a spectrum of temporal and spatial scales. Consistent with usage over the past four decades, we define "net ecosystem production" (NEP) as the net carbon accumulation by ecosystems. Past use of this term has been ambiguous, because it has been used conceptually as a measure of carbon accumulation by ecosystems, but it has often been calculated considering only the balance between gross primary production (GPP) and ecosystem respiration. This calculation ignores other carbon fluxes from ecosystems (e.g., leaching of dissolved carbon and losses associated with disturbance). To avoid conceptual ambiguities, we argue that NEP be defined, as in the past, as the net carbon accumulation by ecosystems and that it explicitly incorporate all the carbon fluxes from an ecosystem, including autotrophic respiration, heterotrophic respiration, losses associated with disturbance, dissolved and particulate carbon losses, volatile organic compound emissions, and lateral transfers among ecosystems. Net biome productivity (NBP), which has been proposed to account for carbon loss during episodic disturbance, is equivalent to NEP at regional or global scales. The multi-scale conceptual framework we describe provides continuity between flux measurements made at the scale of soil profiles and chambers, forest inventories, eddy covariance towers, aircraft, and inversions of remote atmospheric flask samples, allowing a direct comparison of NEP estimates made at all temporal and spatial scales.

  18. Sand deposition in shoreline eddies along five Wild and Scenic Rivers, Idaho

    USGS Publications Warehouse

    Andrews, E.D.; Vincent, K.R.

    2007-01-01

    depositions, which represent more than 40% of all material deposited over the Lochsa River 21.9 km eddy, occurred in the years with the seven largest instantaneous annual peak floods. Beach area and volume for most beaches, however, are less variable year-to-year than the variation in annual deposition would indicate. Accumulative 10-year weighed deposition rate was computed to estimate the effective variability of beach deposition. Although less variable than the annual deposition, the cumulative 10-year deposition calculated for the longest hydrologic records, 71 years, existing on the Idaho Wild and Scenic Rivers varied by more than an order of magnitude from less than 20 cm to more than 220 cm.

  19. Influence of mesoscale eddies on the distribution of nitrous oxide in the eastern tropical South Pacific

    NASA Astrophysics Data System (ADS)

    Arévalo-Martínez, Damian L.; Kock, Annette; Löscher, Carolin R.; Schmitz, Ruth A.; Stramma, Lothar; Bange, Hermann W.

    2016-02-01

    Recent observations in the eastern tropical South Pacific (ETSP) have shown the key role of meso- and submesoscale processes (e.g. eddies) in shaping its hydrographic and biogeochemical properties. Off Peru, elevated primary production from coastal upwelling in combination with sluggish ventilation of subsurface waters fuels a prominent oxygen minimum zone (OMZ). Given that nitrous oxide (N2O) production-consumption processes in the water column are sensitive to oxygen (O2) concentrations, the ETSP is a region of particular interest to investigate its source-sink dynamics. To date, no detailed surveys linking mesoscale processes and N2O distributions as well as their relevance to nitrogen (N) cycling are available. In this study, we present the first measurements of N2O across three mesoscale eddies (two mode water or anticyclonic and one cyclonic) which were identified, tracked, and sampled during two surveys carried out in the ETSP in November-December 2012. A two-peak structure was observed for N2O, wherein the two maxima coincide with the upper and lower boundaries of the OMZ, indicating active nitrification and partial denitrification. This was further supported by the abundances of the key gene for nitrification, ammonium monooxygenase (amoA), and the gene marker for N2O production during denitrification, nitrite reductase (nirS). Conversely, we found strong N2O depletion in the core of the OMZ (O2 < 5 µmol L-1) to be consistent with nitrite (NO2-) accumulation and low levels of nitrate (NO3-), thus suggesting active denitrification. N2O depletion within the OMZ's core was substantially higher in the centre of mode water eddies, supporting the view that eddy activity enhances N-loss processes off Peru, in particular near the shelf break where nutrient-rich, productive waters from upwelling are trapped before being transported offshore. Analysis of eddies during their propagation towards the open ocean showed that, in general, "ageing" of mesoscale eddies

  20. Influence of mesoscale eddies on the distribution of nitrous oxide in the eastern tropical South Pacific

    NASA Astrophysics Data System (ADS)

    Arévalo-Martínez, D. L.; Kock, A.; Löscher, C. R.; Schmitz, R. A.; Stramma, L.; Bange, H. W.

    2015-06-01

    Recent observations in the eastern tropical South Pacific (ETSP) demonstrated the key role of meso- and submesoscale processes (e.g. eddies) in shaping its hydrographic and biogeochemical properties. Off Peru, elevated primary production from coastal upwelling in combination with sluggish ventilation of subsurface waters fuels a prominent oxygen minimum zone (OMZ). Given that nitrous oxide (N2O) production/consumption processes on the water column are sensitive to oxygen (O2) concentrations, the ETSP is a region of particular interest to investigate its source-sink dynamics. To date, no detailed surveys linking mesoscale processes and N2O distributions as well as their relevance to nitrogen (N) cycling are available. In this study, we present the first measurements of N2O across three mesoscale eddies (two mode water or anticyclonic and one cyclonic) which were identified, tracked and sampled during two surveys carried out in the ETSP in November-December 2012. A "two peak" structure was observed for N2O, wherein the two maxima coincide with the upper and lower boundaries of the OMZ, indicating active nitrification and partial denitrification. This was further supported by the abundances of the key gene for nitrification amoA and the gene marker for N2O production during denitrification, nirS. Conversely, we found strong N2O depletion in the core of the OMZ (O2 < 5 μmol L-1) to be consistent with nitrite (NO2-) accumulation and low levels of nitrate (NO3-), thus suggesting active denitrification. N2O depletion within the OMZ's core was substantially higher in the center of mode water eddies, supporting the view that eddy activity enhances N-loss processes off Peru, in particular near the shelf break where nutrient-rich, productive waters from upwelling are trapped before being transported offshore. Analysis of eddies during their propagation towards the open ocean showed that, in general, "aging" of mesoscale eddies tends to decrease N2O concentrations through the

  1. Towards a consistent eddy-covariance processing: an intercomparison of EddyPro and TK3

    NASA Astrophysics Data System (ADS)

    Fratini, G.; Mauder, M.

    2014-07-01

    A comparison of two popular eddy-covariance software packages is presented, namely, EddyPro and TK3. Two approximately 1-month long test data sets were processed, representing typical instrumental setups (i.e., CSAT3/LI-7500 above grassland and Solent R3/LI-6262 above a forest). The resulting fluxes and quality flags were compared. Achieving a satisfying agreement and understanding residual discrepancies required several iterations and interventions of different nature, spanning from simple software reconfiguration to actual code manipulations. In this paper, we document our comparison exercise and show that the two software packages can provide utterly satisfying agreement when properly configured. Our main aim, however, is to stress the complexity of performing a rigorous comparison of eddy-covariance software. We show that discriminating actual discrepancies in the results from inconsistencies in the software configuration requires deep knowledge of both software packages and of the eddy-covariance method. In some instances, it may be even beyond the possibility of the investigator who does not have access to and full knowledge of the source code. Being the developers of EddyPro and TK3, we could discuss the comparison at all levels of details and this proved necessary to achieve a full understanding. As a result, we suggest that researchers are more likely to get comparable results when using EddyPro (v5.1.1) and TK3 (v3.11) - at least with the setting presented in this paper - than they are when using any other pair of EC software which did not undergo a similar cross-validation. As a further consequence, we also suggest that, to the aim of assuring consistency and comparability of centralized flux databases, and for a confident use of eddy fluxes in synthesis studies on the regional, continental and global scale, researchers only rely on software that have been extensively validated in documented intercomparisons.

  2. Effects of eddy initial conditions on nonlinear forcing of planetary scale waves by amplifying baroclinic eddies

    NASA Technical Reports Server (NTRS)

    Young, Richard E.

    1986-01-01

    The previous study of Young and Villere concerning growth of planetary scale waves forced by wave-wave interactions of amplifying intermediate scale baroclinic eddies is extended to investigate effects of different eddy initial conditions. A global, spectral, primitive equation model is used for the calculations. For every set of eddy initial conditions considered, growth rates of planetary modes are considerably greater than growth rates computed from linear instability theory for a fixed zonally independent basic state. However, values of growth rates ranged over a factor of 3 depending on the particular set of eddy initial conditions used. Nonlinear forcing of planetary modes via wave-wave coupling becomes more important than baroclinic growth on the basic state at small values of the intermediate-scale modal amplitudes. The relative importance of direct transfer of kinetic energy from intermediate scales of motion to a planetary mode, compared to baroclinic conversion of available potential energy to kinetic energy within that planetary mode, depends on the individual case. In all cases, however, the transfer of either kinetic or available potential energy to the planetary modes was accomplished principally by wave-wave transfer from intermediate scale eddies, rather than from the zonally averaged state. The zonal wavenumber 2 planetary mode was prominent in all solutions, even in those for which eddy initial conditions were such that a different planetary mode was selectively forced at the start. General characteristics of the structural evolution of the planetary wave components of total heat and momentum flux, and modal structures themselves, were relatively insensitive to variations in eddy initial conditions, even though quantitative details varied from case to case.

  3. Oceanic mass transport by mesoscale eddies.

    PubMed

    Zhang, Zhengguang; Wang, Wei; Qiu, Bo

    2014-07-18

    Oceanic transports of heat, salt, fresh water, dissolved CO2, and other tracers regulate global climate change and the distribution of natural marine resources. The time-mean ocean circulation transports fluid as a conveyor belt, but fluid parcels can also be trapped and transported discretely by migrating mesoscale eddies. By combining available satellite altimetry and Argo profiling float data, we showed that the eddy-induced zonal mass transport can reach a total meridionally integrated value of up to 30 to 40 sverdrups (Sv) (1 Sv = 10(6) cubic meters per second), and it occurs mainly in subtropical regions, where the background flows are weak. This transport is comparable in magnitude to that of the large-scale wind- and thermohaline-driven circulation. PMID:25035491

  4. Oceanic mass transport by mesoscale eddies.

    PubMed

    Zhang, Zhengguang; Wang, Wei; Qiu, Bo

    2014-07-18

    Oceanic transports of heat, salt, fresh water, dissolved CO2, and other tracers regulate global climate change and the distribution of natural marine resources. The time-mean ocean circulation transports fluid as a conveyor belt, but fluid parcels can also be trapped and transported discretely by migrating mesoscale eddies. By combining available satellite altimetry and Argo profiling float data, we showed that the eddy-induced zonal mass transport can reach a total meridionally integrated value of up to 30 to 40 sverdrups (Sv) (1 Sv = 10(6) cubic meters per second), and it occurs mainly in subtropical regions, where the background flows are weak. This transport is comparable in magnitude to that of the large-scale wind- and thermohaline-driven circulation.

  5. Contoured Surface Eddy Current Inspection System

    DOEpatents

    Batzinger, Thomas James; Fulton, James Paul; Rose, Curtis Wayne; Perocchi, Lee Cranford

    2003-04-08

    Eddy current inspection of a contoured surface of a workpiece is performed by forming a backing piece of flexible, resiliently yieldable material with a contoured exterior surface conforming in shape to the workpiece contoured surface. The backing piece is preferably cast in place so as to conform to the workpiece contoured surface. A flexible eddy current array probe is attached to the contoured exterior surface of the backing piece such that the probe faces the contoured surface of the workpiece to be inspected when the backing piece is disposed adjacent to the workpiece. The backing piece is then expanded volumetrically by inserting at least one shim into a slot in the backing piece to provide sufficient contact pressure between the probe and the workpiece contoured surface to enable the inspection of the workpiece contoured surface to be performed.

  6. Eddy current signal comparison for tube identification

    SciTech Connect

    Glass, S. W. E-mail: Ratko.Vojvodic@areva.com; Vojvodic, R. E-mail: Ratko.Vojvodic@areva.com

    2015-03-31

    Inspection of nuclear power plant steam generator tubes is required to justify continued safe plant operation. The steam generators consist of thousands of tubes with nominal diameters of 15 to 22mm, approximately 1mm wall thickness, and 20 to 30m in length. The tubes are inspected by passing an eddy current probe through the tubes from tube end to tube end. It is critical to know exactly which tube identification (row and column) is associated with each tube's data. This is controlled by a precision manipulator that provides the tube ID to the eddy current system. Historically there have been some instances where the manipulator incorrectly reported the tube ID. This can have serious consequences including lack of inspection of a tube, or if a pluggable indication is detected, the tube is likely to be mis-plugged thereby risking a primary to secondary leak.

  7. Eddy current signal comparison for tube identification

    NASA Astrophysics Data System (ADS)

    Glass, S. W.; Vojvodic, R.

    2015-03-01

    Inspection of nuclear power plant steam generator tubes is required to justify continued safe plant operation. The steam generators consist of thousands of tubes with nominal diameters of 15 to 22mm, approximately 1mm wall thickness, and 20 to 30m in length. The tubes are inspected by passing an eddy current probe through the tubes from tube end to tube end. It is critical to know exactly which tube identification (row and column) is associated with each tube's data. This is controlled by a precision manipulator that provides the tube ID to the eddy current system. Historically there have been some instances where the manipulator incorrectly reported the tube ID. This can have serious consequences including lack of inspection of a tube, or if a pluggable indication is detected, the tube is likely to be mis-plugged thereby risking a primary to secondary leak.

  8. Eddy-Current Detection Of Cracks In Reinforced Carbon/Carbon

    NASA Technical Reports Server (NTRS)

    Christensen, Scott V.; Koshti, Ajay M.

    1995-01-01

    Investigations of failures of components made of reinforced carbon/carbon show eddy-current flaw-detection techniques applicable to these components. Investigation focused on space shuttle parts, but applicable to other parts made of carbon/carbon materials. Techniques reveal cracks, too small to be detected visually, in carbon/carbon matrix substrates and in silicon carbide coates on substrates. Also reveals delaminations in carbon/carbon matrices. Used to characterize extents and locations of discontinuities in substrates in situations in which ultrasonic techniques and destructive techniques not practical.

  9. INNOVATIVE EDDY CURRENT PROBE FOR MICRO DEFECTS

    SciTech Connect

    Santos, Telmo G.; Vilaca, Pedro; Quintino, Luisa; Santos, Jorge dos; Rosado, Luis

    2010-02-22

    This paper reports the development of an innovative eddy current (EC) probe, and its application to micro-defects on the root of the Friction Stir Welding (FSW). The new EC probe presents innovative concept issues, allowing 3D induced current in the material, and a lift-off independence. Validation experiments were performed on aluminium alloys processed by FSW. The results clearly show that the new EC probe is able to detect and sizing surface defects about 60 microns depth.

  10. Loop current eddy shedding estimated using Geosat altimeter data

    NASA Technical Reports Server (NTRS)

    Jacobs, Gregg A.; Leben, Robert R.

    1990-01-01

    A method for extracting periodic signals from altimeter data is applied in the Gulf of Mexico using data from the first two years of the Geosat Exact Repeat Mission. The least squares fitting of selected frequencies of sine and cosine functions to the time series of sea surface height at each point of the Geosat ground track is used to estimate the dominant frequency in the gulf for this time period. Optimal interpolation of the sine and cosine coefficients at the dominant frequency to a uniformly spaced grid allows reconstruction of the time series in the gulf and shows eddies shedding from the Loop Current with a period of approximately 10.5 months, consistent with shedding periods determined from numerical models and analysis of satellite infrared data. This technique is a novel method for investigation of periodic signals in Geosat altimetry and is not severely affected by the data outages present in the time series.

  11. Eddy current inspection of weld defects in tubing

    NASA Technical Reports Server (NTRS)

    Katragadda, G.; Lord, W.

    1992-01-01

    An approach using differential probes for the inspection of weld defects in tubing is studied. Finite element analysis is used to model the weld regions and defects. Impedance plane signals are predicted for different weld defect types and compared wherever possible with signals from actual welds in tubing. Results show that detection and sizing of defects in tubing is possible using differential eddy current techniques. The phase angle of the impedance plane trajectory gives a good indication of the sizing of the crack. Data on the type of defect can be obtained from the shape of the impedance plane trajectory and the phase. Depending on the skin depth, detection of outer wall, inner wall, and subsurface defects is possible.

  12. Large Eddy Simulation of Cryogenic Injection Processes at Supercritical Pressure

    NASA Technical Reports Server (NTRS)

    Oefelein, Joseph C.; Garcia, Roberto (Technical Monitor)

    2002-01-01

    This paper highlights results from the first of a series of hierarchical simulations aimed at assessing the modeling requirements for application of the large eddy simulation technique to cryogenic injection and combustion processes in liquid rocket engines. The focus is on liquid-oxygen-hydrogen coaxial injectors at a condition where the liquid-oxygen is injected at a subcritical temperature into a supercritical environment. For this situation a diffusion dominated mode of combustion occurs in the presence of exceedingly large thermophysical property gradients. Though continuous, these gradients approach the behavior of a contact discontinuity. Significant real gas effects and transport anomalies coexist locally in colder regions of the flow, with ideal gas and transport characteristics occurring within the flame zone. The current focal point is on the interfacial region between the liquid-oxygen core and the coaxial hydrogen jet where the flame anchors itself.

  13. Large-eddy simulation of turbulence in steam generators

    SciTech Connect

    Bagwell, T.G.; Hassan, Y.A. ); Steininger D.A. )

    1989-11-01

    A major problem associated with steam generators is excessive tube vibration caused by turbulent-flow buffeting and fluid-elastic excitation. Vibration can lead to tube rupture or wear, necessitating tube plugging and reducing the availability of the steam generator. The fluid/structure interaction phenomenon that causes fluid-elastic tube excitation is unknown at present. The current investigation defines the spectral characteristics of turbulent flow entering the Westinghouse D4 steam generator tube bundles using the large-eddy simulation (LES) technique. Due to the recent availability of supercomputers, LES is being considered as a possible engineering design analysis tool. The information from this study will provide input for defining the temporally fluctuating forces on steam generator tube banks. The GUST code was used to analyze the water box of a Westinghouse model D4 steam generator.

  14. Development of eddy current probes based on magnetoresistive sensors arrays

    NASA Astrophysics Data System (ADS)

    Sergeeva-Chollet, N.; Decitre, J.-M.; Fermon, C.; Pelkner, M.; Reimund, V.; Kreutzbruck, M.

    2014-02-01

    Eddy Current Technique is a powerful method for detection of surface notches and of buried flaws during inspection of metallic parts. Recent EC array probes have demonstrated a fast and efficient control of large surfaces. Nevertheless, when the size of flaws decreases or the defect is rather deep, traditional winding coil probes turn out to be useless. Magnetoresistive sensors present the advantages of flat frequency response and micron size. These sensors are hence very attractive for the detection of buried defects that require low frequencies because of skin depth effect. An optimization of the probe with magnetoresistive sensors as receivers has been made by simulations using CIVA software and finite elements methods with OPERA. EC probes for buried flaw detection have been designed. Experimental results have been compared with simulations.

  15. Interface Exchange as an Indicator for Eddy Heat Transport

    SciTech Connect

    Petersen, Mark R.; Williams, Sean J.; Hecht, Matthew W.; Maltrud, Mathew E.; Hamann, Bernd; Patchett, John M.; Ahrens, James P.

    2012-06-12

    The ocean contains many large-scale, long-lived vortices, called mesoscale eddies, that are believed to have a role in the transport and redistribution of salt, heat, and nutrients throughout the ocean. Determining this role, however, has proven to be a challenge, since the mechanics of eddies are only partly understood; a standard definition for these ocean eddies does not exist and, therefore, scientifically meaningful, robust methods for eddy extraction, characterization, tracking and visualization remain a challenge. In order to shed light on the nature and potential roles of eddies, we have combined our previous research on eddy identification and tracking, and have used those approaches as the basis for analysis-driven computational experiments on the nature of eddies. Based on the resulting visualizations of eddy behavior, we have devised a new metric to characterize the transfer of water into and out of eddies across their boundary, and have developed visualization methods for this new metric to provide clues about the role eddies play in the global ocean and, potentially, climate change.

  16. Eddy current inspection tool. [Patent application

    DOEpatents

    Petrini, R.R.; Van Lue, D.F.

    1980-10-29

    A miniaturized inspection tool, for testing and inspection of metal objects in locations with difficult accessibility, which comprises eddy current sensing equipment with a probe coil, and associated coaxial coil cable, oil energizing means, and circuit means responsive to impedance changes in the coil as effected by induced eddy currents in a test object to produce a data output signal proportional to such changes. The coil and cable are slideably received in the utility channel of the flexible insertion tube of a fiberoptic scope. The scope is provided with light transmitting and receiving fiberoptics for viewing through the flexible tube, and articulation means for articulating the distal end of the tube and permitting close control of coil placement relative to a test object. The eddy current sensing equipment includes a tone generator for generating audible signals responsive to the data output signal. In one selected mode of operation, the tone generator responsive to the output signal above a selected level generates a constant single frequency tone for signalling detection of a discontinuity and, in a second selected mode, generates a tone whose frequency is proportional to the difference between the output signal and a predetermined selected threshold level.

  17. Large Eddy Simulation of Vertical Axis Wind Turbine Wakes

    NASA Astrophysics Data System (ADS)

    Shamsoddin, Sina; Porté-Agel, Fernando

    2014-05-01

    In this study, large-eddy simulation (LES) is combined with a turbine model to investigate the wake behind a vertical-axis wind turbine (VAWT) in a three dimensional turbulent flow. Two methods are used to model the subgrid-scale (SGS) stresses: (a) the Smagorinsky model, and (b) the modulated gradient model. To parameterize the effects of the VAWT on the flow, two VAWT models are developed: (a) the actuator surface model (ASM), in which the time-averaged turbine-induced forces are distributed on a surface swept by the turbine blades, i.e. the actuator surface, and (b) the actuator line model (ALM), in which the instantaneous blade forces are only spatially distributed on lines representing the blades, i.e. the actuator lines. This is the first time that LES is applied and validated for simulation of VAWT wakes by using either the ASM or the ALM techniques. In both models, blade-element theory is used to calculate the lift and drag forces on the blades. The results are compared with flow measurements in the wake of a model straight-bladed VAWT, carried out in the Institute de Méchanique et Statistique de la Turbulence (IMST) water channel. Different combinations of SGS models with VAWT models are studied and a fairly good overall agreement between simulation results and measurement data is observed. In general, the ALM is found to better capture the unsteady-periodic nature of the wake and shows a better agreement with the experimental data compared with the ASM. The modulated gradient model is also found to be a more reliable SGS stress modeling technique, compared with the Smagorinsky model, and it yields reasonable predictions of the mean flow and turbulence characteristics of a VAWT wake using its theoretically-determined model coefficient. Keywords: Vertical-axis wind turbines (VAWTs); VAWT wake; Large-eddy simulation; Actuator surface model; Actuator line model; Smagorinsky model; Modulated gradient model

  18. Eddy Covariance Method for CO2 Emission Measurements: CCS Applications, Principles, Instrumentation and Software

    NASA Astrophysics Data System (ADS)

    Burba, George; Madsen, Rod; Feese, Kristin

    2013-04-01

    The Eddy Covariance method is a micrometeorological technique for direct high-speed measurements of the transport of gases, heat, and momentum between the earth's surface and the atmosphere. Gas fluxes, emission and exchange rates are carefully characterized from single-point in-situ measurements using permanent or mobile towers, or moving platforms such as automobiles, helicopters, airplanes, etc. Since the early 1990s, this technique has been widely used by micrometeorologists across the globe for quantifying CO2 emission rates from various natural, urban and agricultural ecosystems [1,2], including areas of agricultural carbon sequestration. Presently, over 600 eddy covariance stations are in operation in over 120 countries. In the last 3-5 years, advancements in instrumentation and software have reached the point when they can be effectively used outside the area of micrometeorology, and can prove valuable for geological carbon capture and sequestration, landfill emission measurements, high-precision agriculture and other non-micrometeorological industrial and regulatory applications. In the field of geological carbon capture and sequestration, the magnitude of CO2 seepage fluxes depends on a variety of factors. Emerging projects utilize eddy covariance measurement to monitor large areas where CO2 may escape from the subsurface, to detect and quantify CO2 leakage, and to assure the efficiency of CO2 geological storage [3,4,5,6,7,8]. Although Eddy Covariance is one of the most direct and defensible ways to measure and calculate turbulent fluxes, the method is mathematically complex, and requires careful setup, execution and data processing tailor-fit to a specific site and a project. With this in mind, step-by-step instructions were created to introduce a novice to the conventional Eddy Covariance technique [9], and to assist in further understanding the method through more advanced references such as graduate-level textbooks, flux networks guidelines, journals

  19. Measuring evapotranspiration: comparison of eddy covariance, scintillometers and enclosed chambers

    NASA Astrophysics Data System (ADS)

    Yee, Mei Sun; Beringer, Jason; Pauwels, Valentijn R. N.; Daly, Edoardo; Walker, Jeffrey P.; Rüdiger, Christoph

    2014-05-01

    Evapotranspiration (ET) is the combination of evaporation from the soil surface and transpiration from plants. It is an important component of the hydrological cycle, particularly in arid and semi-arid areas where most of the precipitation is returned to the atmosphere via ET. It also drives the land-surface energy balance, largely affecting soil temperature and the heat exchange between the land and atmosphere. Therefore, the ability to quantify ET is important for accurate climate and weather predictions, as well as improving the management of water resources. Various methods for measuring ET are available, including gas chambers, lysimeters, Bowen-ratio energy balance stations, eddy-covariance systems, scintillometers, and space-borne sensors. These methods differ in spatial scales (from leaf to basin scale), time scales (seconds to days), principles (water-balance, mass-transfer, eddy-correlation, energy balance) and have their own strengths and limitations. For instance, point scale measurements, such as those obtained using lysimeters, assume that the sample is representative of a larger area, whereas measurements at a basin scale assume that the spatial average of all the other components in the water or energy balance equations can be measured accurately. The purpose of this study is to compare different techniques to measure ET across their respective scales and to identify causes of discrepancies between measurements. The final aim is to identify a technique or a combination of techniques to be used for verification of remote sensing evapotranspiration products. The study area is located in the Yanco Study Area (34.561°S, 35.170°S, 145.826°E, 146.439°E), situated within the western plains of the Murrumbidgee River catchment, in New South Wales, Australia. This area has been extensively monitored and a series of field experiments have been performed in the past to contribute to the pre- and post-launch algorithm development of earth observing

  20. Harmonics suppression of vacuum chamber eddy current induced fields with application to the Superconducting Super Collider (SSC) Low Energy Booster (LEB) Magnets

    SciTech Connect

    Schlueter, R.D.; Halbach, K.

    1991-12-04

    This memo presents the formulation of an expression for eddy currents induced in a thin-walled conductor due to a time-dependent electromagnet field excitation. Then follows an analytical development for prediction of vacuum chamber eddy current induced field harmonics in iron-core electromagnets. A passive technique for harmonics suppression is presented with specific application to the design of the Superconducting Super Collider (SSC) Low Energy B (LEB) Magnets.

  1. Harmonics suppression of vacuum chamber eddy current-induced fields with application to the Superconducting Super Collider Low Energy Booster Magnets

    SciTech Connect

    Schlueter, R.; Halbach, K.

    1992-01-01

    This report presents the formulation of an expression for eddy currents induced in a thin-walled conductor due to a time-dependent electromagnet field excitation. Then follows an analytical development for prediction of vacuum chamber eddy current-induced field harmonics in iron-core electromagnets. A passive technique for harmonics suppression is presented with specific application to the design of the Superconducting Super Collider Low Energy Booster Magnets.

  2. The dynamics of the turbopause. [variability of eddy diffusion

    NASA Technical Reports Server (NTRS)

    Roper, R. G.

    1974-01-01

    The investigation reported shows the variability of eddy diffusion at the turbopause on diurnal, seasonal, and solar cycle time scales, and also on latitude. Realistic vertical eddy diffusion profiles for the lower thermosphere are presented. The results of the studies illustrate the importance of global winds in the dynamics of the lower thermosphere. Difficulties regarding the direct measurement of eddy diffusivity in the lower thermosphere are discussed.

  3. Ocean eddies generated by seamounts in the north pacific.

    PubMed

    Royer, T C

    1978-03-10

    Small-scale (diameters of about 37 kilometers) fluctuations in dynamic topography north of Hawaii along 158 degrees W are well correlated with upstream seamounts. The fluctuations are subsurface but are manifested as baroclinic eddies at the sea surface. These eddies are confirmed by direct observations and supported by theoretical considerations. The eddies cause small-scale variability in the currents and hydrographic structures in this area, and they should be considered in any sampling programs of the region.

  4. A new gauge-invariant method for diagnosing eddy diffusivities

    NASA Astrophysics Data System (ADS)

    Mak, J.; Maddison, J. R.; Marshall, D. P.

    2016-08-01

    Coarse resolution numerical ocean models must typically include a parameterisation for mesoscale turbulence. A common recipe for such parameterisations is to invoke mixing of some tracer quantity, such as potential vorticity or buoyancy. However, it is well known that eddy fluxes include large rotational components which necessarily do not lead to any mixing; eddy diffusivities diagnosed from unfiltered fluxes are thus contaminated by the presence of these rotational components. Here a new methodology is applied whereby eddy diffusivities are diagnosed directly from the eddy force function. The eddy force function depends only upon flux divergences, is independent of any rotational flux components, and is inherently non-local and smooth. A one-shot inversion procedure is applied, minimising the mis-match between parameterised force functions and force functions derived from eddy resolving calculations. This enables diffusivities associated with the eddy potential vorticity and Gent-McWilliams coefficients associated with eddy buoyancy fluxes to be diagnosed. This methodology is applied to multi-layer quasi-geostrophic ocean gyre simulations. It is found that: (i) a strictly down-gradient scheme for mixing potential vorticity and quasi-geostrophic buoyancy has limited success in reducing the mis-match compared to one with no sign constraint on the eddy diffusivity or Gent--McWilliams coefficient, with prevalent negative signals around the time-mean jet; (ii) the diagnostic is successful away from the jet region and wind-forced top layer; (iii) the locations of closed mean stream lines correlate with signals of positive eddy potential vorticity diffusivity; (iv) there is indication that the magnitude of the eddy potential vorticity diffusivity correlates well with the eddy energy. Implications for parameterisation are discussed in light of these diagnostic results.

  5. Application of large eddy interaction model to a mixing layer

    NASA Technical Reports Server (NTRS)

    Murthy, S. N. B.

    1989-01-01

    The large eddy interaction model (LEIM) is a statistical model of turbulence based on the interaction of selected eddies with the mean flow and all of the eddies in a turbulent shear flow. It can be utilized as the starting point for obtaining physical structures in the flow. The possible application of the LEIM to a mixing layer formed between two parallel, incompressible flows with a small temperature difference is developed by invoking a detailed similarity between the spectra of velocity and temperature.

  6. Unsupervised Classification of Surface Defects in Wire Rod Production Obtained by Eddy Current Sensors

    PubMed Central

    Saludes-Rodil, Sergio; Baeyens, Enrique; Rodríguez-Juan, Carlos P.

    2015-01-01

    An unsupervised approach to classify surface defects in wire rod manufacturing is developed in this paper. The defects are extracted from an eddy current signal and classified using a clustering technique that uses the dynamic time warping distance as the dissimilarity measure. The new approach has been successfully tested using industrial data. It is shown that it outperforms other classification alternatives, such as the modified Fourier descriptors. PMID:25938201

  7. Unsupervised classification of surface defects in wire rod production obtained by eddy current sensors.

    PubMed

    Saludes-Rodil, Sergio; Baeyens, Enrique; Rodríguez-Juan, Carlos P

    2015-01-01

    An unsupervised approach to classify surface defects in wire rod manufacturing is developed in this paper. The defects are extracted from an eddy current signal and classified using a clustering technique that uses the dynamic time warping distance as the dissimilarity measure. The new approach has been successfully tested using industrial data. It is shown that it outperforms other classification alternatives, such as the modified Fourier descriptors. PMID:25938201

  8. Film cooling from inclined cylindrical holes using large eddy simulations

    NASA Astrophysics Data System (ADS)

    Peet, Yulia V.

    2006-12-01

    The goal of the present study is to investigate numerically the physics of the flow, which occurs during the film cooling from inclined cylindrical holes, Film cooling is a technique used in gas turbine industry to reduce heat fluxes to the turbine blade surface. Large Eddy Simulation (LES) is performed modeling a realistic film cooling configuration, which consists of a large stagnation-type reservoir, feeding an array of discrete cooling holes (film holes) flowing into a flat plate turbulent boundary layer. Special computational methodology is developed for this problem, involving coupled simulations using multiple computational codes. A fully compressible LES code is used in the area above the flat plate, while a low Mach number LES code is employed in the plenum and film holes. The motivation for using different codes comes from the essential difference in the nature of the flow in these different regions. Flowfield is analyzed inside the plenum, film hole and a crossflow region. Flow inside the plenum is stagnating, except for the region close to the exit, where it accelerates rapidly to turn into the hole. The sharp radius of turning at the trailing edge of the plenum pipe connection causes the flow to separate from the downstream wall of the film hole. After coolant injection occurs, a complex flowfield is formed consisting of coherent vortical structures responsible for bringing hot crossflow fluid in contact with the walls of either the film hole or the blade, thus reducing cooling protection. Mean velocity and turbulent statistics are compared to experimental measurements, yielding good agreement for the mean flowfield and satisfactory agreement for the turbulence quantities. LES results are used to assess the applicability of basic assumptions of conventional eddy viscosity turbulence models used with Reynolds-averaged (RANS) approach, namely the isotropy of an eddy viscosity and thermal diffusivity. It is shown here that these assumptions do not hold

  9. Eddy Current System for Material Inspection and Flaw Visualization

    NASA Technical Reports Server (NTRS)

    Bachnak, R.; King, S.; Maeger, W.; Nguyen, T.

    2007-01-01

    Eddy current methods have been successfully used in a variety of non-destructive evaluation applications including detection of cracks, measurements of material thickness, determining metal thinning due to corrosion, measurements of coating thickness, determining electrical conductivity, identification of materials, and detection of corrosion in heat exchanger tubes. This paper describes the development of an eddy current prototype that combines positional and eddy-current data to produce a C-scan of tested material. The preliminary system consists of an eddy current probe, a position tracking mechanism, and basic data visualization capability. Initial test results of the prototype are presented in this paper.

  10. Characterizing the eddy field in the Arctic Ocean halocline

    NASA Astrophysics Data System (ADS)

    Zhao, Mengnan; Timmermans, Mary-Louise; Cole, Sylvia; Krishfield, Richard; Proshutinsky, Andrey; Toole, John

    2014-12-01

    Ice-Tethered Profilers (ITP), deployed in the Arctic Ocean between 2004 and 2013, have provided detailed temperature and salinity measurements of an assortment of halocline eddies. A total of 127 mesoscale eddies have been detected, 95% of which were anticyclones, the majority of which had anomalously cold cores. These cold-core anticyclonic eddies were observed in the Beaufort Gyre region (Canadian water eddies) and the vicinity of the Transpolar Drift Stream (Eurasian water eddies). An Arctic-wide calculation of the first baroclinic Rossby deformation radius Rd has been made using ITP data coupled with climatology; Rd ˜ 13 km in the Canadian water and ˜8 km in the Eurasian water. The observed eddies are found to have scales comparable to Rd. Halocline eddies are in cyclogeostrophic balance and can be described by a Rankine vortex with maximum azimuthal speeds between 0.05 and 0.4 m/s. The relationship between radius and thickness for the eddies is consistent with adjustment to the ambient stratification. Eddies may be divided into four groups, each characterized by distinct core depths and core temperature and salinity properties, suggesting multiple source regions and enabling speculation of varying formation mechanisms.

  11. A daily global mesoscale ocean eddy dataset from satellite altimetry

    PubMed Central

    Faghmous, James H.; Frenger, Ivy; Yao, Yuanshun; Warmka, Robert; Lindell, Aron; Kumar, Vipin

    2015-01-01

    Mesoscale ocean eddies are ubiquitous coherent rotating structures of water with radial scales on the order of 100 kilometers. Eddies play a key role in the transport and mixing of momentum and tracers across the World Ocean. We present a global daily mesoscale ocean eddy dataset that contains ~45 million mesoscale features and 3.3 million eddy trajectories that persist at least two days as identified in the AVISO dataset over a period of 1993–2014. This dataset, along with the open-source eddy identification software, extract eddies with any parameters (minimum size, lifetime, etc.), to study global eddy properties and dynamics, and to empirically estimate the impact eddies have on mass or heat transport. Furthermore, our open-source software may be used to identify mesoscale features in model simulations and compare them to observed features. Finally, this dataset can be used to study the interaction between mesoscale ocean eddies and other components of the Earth System. PMID:26097744

  12. Eddies in the southwestern East/Japan Sea

    NASA Astrophysics Data System (ADS)

    Lee, Dong-Kyu; Niiler, Peter

    2010-10-01

    Closed loop mesoscale eddies were identified and tracked in the Ulleung Basin of the southwestern Japan/East Sea (JES) using the winding-angle (WA) methodology, for mapping the absolute geostrophic currents into surface streamlines of flow. The geostrophic velocity used here was the sum of the Archiving, Validation and Interpretation of Satellite Oceanographic data (AVISO), time variable velocity and the 1992-2007 mean geostrophic velocity. Local sampling bias was removed using the drifter observations. This WA methodology of deriving the Lagrangian path lines that drifters followed over a 7-day period was validated by individual drifter tracks and it demonstrated closed looping eddy motions. The WA method demonstrated that less than 6% of the closed streamlines appeared when drifters did not show a closed loop in their vicinity, compared to 30% of the excess detection rate by the Okubo-Weiss method of locating closed loop structures. Three groups of eddies were identified: (1) Coastal Cold and Warm Eddies, which appeared in the area between the coast of southern Korea and the East Korean Warm Current (EKWC), when a southward coastal current was present, (2) Frontal Cold and Warm Eddies, which were formed in the region of the seaward extension of the meandering EKWC, north of Ulleung Island and (3) Ulleung Warm Eddies (UWE) and Dok Cold Eddies (DCE), which appeared during meanders of the EKWC, in the Ulleung Basin. No seasonal concentration for eddy generation and eddy population was found. The average radius of eddies was about 38-60 km. These were born, moved in an erratic pattern and then died in the vicinity where the EKWC separated from the coast and formed a large meander. The time-mean large meander formed meridionally concentrated bands of positive and negative relative vorticity. The cyclonic (cold) eddies tend to reside within the band of positive time-mean relative vorticity, and the anticyclonic (warm) eddies reside within the bands of negative relative

  13. Determination of dry deposition of ozone: Comparison of different measuring techniques

    NASA Technical Reports Server (NTRS)

    Colbeck, I.; Simmons, A.

    1994-01-01

    Five methods were used to investigate the deposition of ozone. The measurements of the eddy diffusivity of heat using the Bowen ratio technique were slightly higher than but closely matched the measurements made for the momentum eddy diffusivity, measured simultaneously, using the profile technique. Similar flux values were obtained by the profile and eddy correlation method. Deposition velocities determined using the box method were higher than those calculated using an open top chamber.

  14. Eddy-driven sediment transport in the Argentine Basin: Is the height of the Zapiola Rise hydrodynamically controlled?

    NASA Astrophysics Data System (ADS)

    Weijer, Wilbert; Maltrud, Mathew E.; Homoky, William B.; Polzin, Kurt L.; Maas, Leo R. M.

    2015-03-01

    In this study, we address the question whether eddy-driven transports in the Argentine Basin can be held responsible for enhanced sediment accumulation over the Zapiola Rise, hence accounting for the existence and growth of this sediment drift. To address this question, we perform a 6 year simulation with a strongly eddying ocean model. We release two passive tracers, with settling velocities that are consistent with silt and clay size particles. Our experiments show contrasting behavior between the silt fraction and the lighter clay. Due to its larger settling velocity, the silt fraction reaches a quasisteady state within a few years, with abyssal sedimentation rates that match net input. In contrast, clay settles only slowly, and its distribution is heavily stratified, being transported mainly along isopycnals. Yet, both size classes display a significant and persistent concentration minimum over the Zapiola Rise. We show that the Zapiola Anticyclone, a strong eddy-driven vortex that circulates around the Zapiola Rise, is a barrier to sediment transport, and hence prevents significant accumulation of sediments on the Rise. We conclude that sediment transport by the turbulent circulation in the Argentine Basin alone cannot account for the preferred sediment accumulation over the Rise. We speculate that resuspension is a critical process in the formation and maintenance of the Zapiola Rise.

  15. Pattern formation at the ocean surface: The distribution of Sargassum and the role of the eddy field

    NASA Astrophysics Data System (ADS)

    Zhong, Y.; Bracco, A.; Villareal, T.

    2010-12-01

    Positively buoyant organisms such as the macroalgae Sargassum and the cyanobacteria Trichodesmiumm often form surface accumulations visible in satellite imagery. Here we discuss the accumulation of floating material in the ocean in presence of meso- and submesoscales activity. Using high resolution simulations of the ocean mesoscale in both idealized and realistic domains (specifically in a 3D box where coherent eddies are forced by small-scale winds, and in the western Gulf of Mexico, where extensive concentrations of floating Sargassum have been recorded in satellite images) we show that the distribution of tracers at ocean surface departs rapidly from the one observed few tens of meters below it. Such distribution does not resemble what observed for passive tracers in quasigeostrophic turbulence. The strong divergence and convergence zones generated at the surface by the eddy field are responsible for the creation of ‘lines’ where the floating material accumulates. Floating particles are expelled from the core of the eddies, and concentrate in convergence regions of size and strength comparable to the ones observed through the satellite images. In light of those results, Sargassum and/or Trichodesmium may provide a useful proxy to track convergence/divergence processes at the ocean surface.

  16. Eddy-covariance methane flux measurements over a European beech forest

    NASA Astrophysics Data System (ADS)

    Gentsch, Lydia; Siebicke, Lukas; Knohl, Alexander

    2015-04-01

    The role of forests in global methane (CH4) turnover is currently not well constrained, partially because of the lack of spatially integrative forest-scale measurements of CH4 fluxes. Soil chamber measurements imply that temperate forests generally act as CH4 sinks. Upscaling of chamber observations to the forest scale is however problematic, if the upscaling is not constrained by concurrent 'top-down' measurements, such as of the eddy-covariance type, which provide sufficient integration of spatial variations and of further potential CH4 flux components within forest ecosystems. Ongoing development of laser absorption-based optical instruments, resulting in enhanced measurement stability, precision and sampling speed, has recently improved the prospects for meaningful eddy-covariance measurements at sites with presumably low CH4 fluxes, hence prone to reach the flux detection limit. At present, we are launching eddy-covariance CH4 measurements at a long-running ICOS flux tower site (Hainich National Park, Germany), located in a semi natural, unmanaged, beech dominated forest. Eddy-covariance measurements will be conducted with a laser spectrometer for parallel CH4, H2Ov and CO2 measurements (FGGA, Los Gatos Research, USA). Independent observations of the CO2 flux by the FGGA and a standard Infrared Gas Analyser (LI-7200, LI-COR, USA) will allow to evaluate data quality of measured CH4 fluxes. Here, we want to present first results with a focus on uncertainties of the calculated CH4 fluxes with regard to instrument precision, data processing and site conditions. In future, we plan to compare eddy-covariance flux estimates to side-by-side turbulent flux observations from a novel eddy accumulation system. Furthermore, soil CH4 fluxes will be measured with four automated chambers situated within the tower footprint. Based on a previous soil chamber study at the same site, we expect the Hainich forest site to act as a CH4 sink. However, we hypothesize that our

  17. Inter-comparison of stratospheric mean-meridional circulation and eddy mixing among six reanalysis datasets

    NASA Astrophysics Data System (ADS)

    Miyazaki, K.; Iwasaki, T.; Kawatani, Y.; Kobayashi, C.; Sugawara, S.; Hegglin, M.

    2015-10-01

    The stratospheric mean-meridional circulation (MMC) and eddy mixing are compared among six meteorological reanalysis datasets: NCEP-NCAR, NCEP-CFSR, ERA-40, ERA-Interim, JRA-25, and JRA-55 for the period 1979-2012. The reanalysis datasets produced using advanced systems (i.e., NCEP-CFSR, ERA-Interim, and JRA-55) generally reveal a weaker MMC and stronger eddy mixing in the Northern Hemisphere (NH) compared with those produced using older systems (i.e., NCEP/NCAR, ERA-40, and JRA-25). In the NH lower stratosphere, the stronger eddy mixing is attributed to stronger planetary-scale mixing in the new datasets, whereas small-scale mixing is weaker in the new datasets. Conventional data assimilation techniques introduce analysis increments without maintaining physical balance, which may have caused an overly strong MMC and spurious small-scale eddies in the old datasets. At the NH mid-latitudes, only ERA-Interim reveals a weakening MMC trend in the deep branch of the Brewer-Dobson Circulation (BDC). The relative importance of the eddy mixing compared with the mean transport in the subtropical lower stratosphere is considered to be important in controlling mean Age-of-Air (AoA) variations above, which showed increasing trends in ERA-Interim and JRA-55; this together with the weakened MMC in the deep branch may imply an increasing AoA trend in the NH middle stratosphere in ERA-Interim. Overall, discrepancies between the different variables and trends therein as derived from the different reanalyses are still relatively large, suggesting that more investments into these products are needed in order to obtain a consolidated picture of observed changes in the BDC and the mechanisms that drive them.

  18. Toward a Mexican eddy covariance network for carbon cycle science

    NASA Astrophysics Data System (ADS)

    Vargas, Rodrigo; Yépez, Enrico A.

    2011-09-01

    First Annual MexFlux Principal Investigators Meeting; Hermosillo, Sonora, Mexico, 4-8 May 2011; The carbon cycle science community has organized a global network, called FLUXNET, to measure the exchange of energy, water, and carbon dioxide (CO2) between the ecosystems and the atmosphere using the eddy covariance technique. This network has provided unprecedented information for carbon cycle science and global climate change but is mostly represented by study sites in the United States and Europe. Thus, there is an important gap in measurements and understanding of ecosystem dynamics in other regions of the world that are seeing a rapid change in land use. Researchers met under the sponsorship of Red Temática de Ecosistemas and Consejo Nacional de Ciencia y Tecnologia (CONACYT) to discuss strategies to establish a Mexican eddy covariance network (MexFlux) by identifying researchers, study sites, and scientific goals. During the meeting, attendees noted that 10 study sites have been established in Mexico with more than 30 combined years of information. Study sites span from new sites installed during 2011 to others with 9 to 6 years of measurements. Sites with the longest span measurements are located in Baja California Sur (established by Walter Oechel in 2002) and Sonora (established by Christopher Watts in 2005); both are semiarid ecosystems. MexFlux sites represent a variety of ecosystem types, including Mediterranean and sarcocaulescent shrublands in Baja California; oak woodland, subtropical shrubland, tropical dry forest, and a grassland in Sonora; tropical dry forests in Jalisco and Yucatan; a managed grassland in San Luis Potosi; and a managed pine forest in Hidalgo. Sites are maintained with an individual researcher's funds from Mexican government agencies (e.g., CONACYT) and international collaborations, but no coordinated funding exists for a long-term program.

  19. Compact, intrathermocline eddies in the Sargasso Sea

    SciTech Connect

    Dugan, J.P.; Mied, R.P.; Mignerey, P.C.; Schuetz, A.F.

    1982-01-20

    We report observations of isolated lenses of constant-temperature water embedded in the permanent thermocline in the Sargasso Sea. These features are observed to have vertical extents of < or approx. =220 m horizontal dimensions of < or approx. =65 km, and residence depths near 700 m. A dynamic model is constructed which permits balance among the pressure gradient. Coriolis, and cyclostrophic forces and maintains the lens against gravitational collapse. A results that anticyclonic rim velocities approaches 20 cm s/sup -1/ are permitted and that these eddies have finite radii of the order of 50 km, at which their thicknesses fall to zero.

  20. Obituary: John Allen Eddy (1931-2009)

    NASA Astrophysics Data System (ADS)

    Gingerich, Owen

    2011-12-01

    Jack Eddy, who was born 25 March 1931 in Pawnee City in southeastern Nebraska, died after a long battle with cancer in Tucson, Arizona, on 10 June 2009. Best known for his work on the long-term instability of the sun, described in a landmark paper in Science titled "The Maunder Minimum," he also deserves recognition as one of the triumvirate who founded the Historical Astronomy Division of the AAS. His father ran a cooperative farm store where Jack worked as a teenager; his parents were of modest means and there were concerns whether he could afford college, but one of the state senators, also from Pawnee City, nominated him for the U.S. Naval Academy. A course in celestial navigation gave him a love of the sky. After graduation in 1953, he served four years on aircraft carriers in the Pacific during the Korean War and then as a navigator and operations officer on a destroyer in the Persian Gulf. In 1957, he left the Navy and entered graduate school at the University of Colorado in Boulder, where in 1962 he received a Ph.D. in astro-geophysics. His thesis, supervised by Gordon Newkirk, dealt with light scattering in the upper atmosphere, based on data from stratospheric balloon flights. He then worked as teacher and researcher at the High Altitude Observatory in Boulder. Always adventuresome and willing to explore new frontiers, on his own time Eddy examined an Amerindian stone circle in the Big Horn mountains of Wyoming, a so-called medicine wheel, concluding that there were alignments with both the solstitial sun and Aldebaran. His conjectures became a cover story on Science magazine in June of 1974. In 1971 Jack privately reproduced for his friends a small collection of his own hilarious cartoons titled "Job Opportunities for Out-of-work Astronomers," with an abstract beginning, "Contrary to popular belief, a PhD in Astronomy/Astrophysics need not be a drawback in locating work in this decade." For example, under merchandising, a used car salesman advertises

  1. Variable-Force Eddy-Current Damper

    NASA Technical Reports Server (NTRS)

    Cunningham, R. E.

    1986-01-01

    Variable damping achieved without problems of containing viscous fluids. Eddy-current damping obtained by moving copper or aluminum conductors through magnetic fields. Position of magnet carrier determines amount of field engagement and, therefore, amount of damping. Three advantages of concept: Magnitudes of stiffness and damping continously varied from maximum to zero without bringing rotor or shaft to stop; used in rotating machines not having viscous fluids available such as lubricating oils; produces sizable damping forces in machines that pump liquid hydrogen at - 246 degrees C and liquid oxygen at - 183 degrees C and are compact in size.

  2. Eddy-Current Monitoring Of Composite Layups

    NASA Technical Reports Server (NTRS)

    Fox, Robert L.; Buckley, John D.

    1993-01-01

    Eddy-current-probe apparatus used to determine predominant orientations of fibers in fiber/matrix composite materials. Apparatus nondestructive, noninvasive means for monitoring composite prepregs and layups during fabrication to ensure predictable and repeatable mechanical properties of finished composite panels. Consists essentially of electromagnet coil wrapped around horseshoe-shaped powdered-iron or ferrite ore. Optionally, capacitor included in series or parallel with coil to form resonant circuit. Impedance monitor excites radio-frequency current in coil and measures impedance of probe circuit. Affected by whatever material placed near ends of core, where material intercepts alternating magnetic field excited in core by current in coil.

  3. Eddy current X-Y scanner system

    NASA Technical Reports Server (NTRS)

    Kurtz, G. W.

    1983-01-01

    The Nondestructive Evaluation Branch of the Materials and Processes Laboratory became aware of a need for a miniature, portable X-Y scanner capable of performing eddy current or other nondestructive testing scanning operations such as ultrasonic, or small areas of flat plate. The technical description and operational theory of the X-Y scanner system designed and built to fulfill this need are covered. The scanner was given limited testing and performs according to its design intent, which is to scan flat plate areas of approximately 412 sq cm (64 sq in) during each complete cycle of scanning.

  4. Inverse source problems for eddy current equations

    NASA Astrophysics Data System (ADS)

    Alonso Rodríguez, Ana; Camaño, Jessika; Valli, Alberto

    2012-01-01

    We study the inverse source problem for the eddy current approximation of Maxwell equations. As for the full system of Maxwell equations, we show that a volume current source cannot be uniquely identified by knowledge of the tangential components of the electromagnetic fields on the boundary, and we characterize the space of non-radiating sources. On the other hand, we prove that the inverse source problem has a unique solution if the source is supported on the boundary of a subdomain or if it is the sum of a finite number of dipoles. We address the applicability of this result for the localization of brain activity from electroencephalography and magnetoencephalography measurements.

  5. Large eddy simulation in the ocean

    NASA Astrophysics Data System (ADS)

    Scotti, Alberto

    2010-12-01

    Large eddy simulation (LES) is a relative newcomer to oceanography. In this review, both applications of traditional LES to oceanic flows and new oceanic LES still in an early stage of development are discussed. The survey covers LES applied to boundary layer flows, traditionally an area where LES has provided considerable insight into the physics of the flow, as well as more innovative applications, where new SGS closure schemes need to be developed. The merging of LES with large-scale models is also briefly reviewed.

  6. Electromagnetic Enhancement of Pulsed Eddy Current Signals

    NASA Astrophysics Data System (ADS)

    Mandache, Catalin V.; Vivier Lefebvre, J. H.

    2007-03-01

    The sensitivity of pulsed eddy current (PEC) testing is increased when a layer of magnetic material is placed on the far side of the conductive test piece. This procedure ensures preservation of the lift-off point of intersection (LOI) feature, otherwise non-existent for the PEC inspections of magnetic materials. The presented method could find applications in non-destructive inspections for corrosion thinning, thickness measurement of conductive coatings over ferrous substrates, and integrity of thermally insulated pipes. Laboratory-obtained examples are given to support the method applicability.

  7. Eddy current measurement of tube element spacing

    DOEpatents

    Latham, Wayne Meredith; Hancock, Jimmy Wade; Grut, Jayne Marie

    1998-01-01

    A method of electromagnetically measuring the distance between adjacent tube elements in a heat exchanger. A cylindrical, high magnetic permeability ferrite slug is placed in the tube adjacent the spacing to be measured. A bobbin or annular coil type probe operated in the absolute mode is inserted into a second tube adjacent the spacing to be measured. From prior calibrations on the response of the eddy current coil, the signals from the coil, when sensing the presence of the ferrite slug, are used to determine the spacing between the tubes.

  8. Energy budgets on the interactions between the mean and eddy flows during a persistent heavy rainfall event over the Yangtze River valley in summer 2010

    NASA Astrophysics Data System (ADS)

    Fu, Shenming; Wang, Huijie; Sun, Jianhua; Zhang, Yuanchun

    2016-06-01

    In this study, a persistent heavy rainfall event (PHRE) that lasted for around 9 days (from 0000 UTC 17 to 0000 UTC 26 June 2010) and caused accumulated precipitation above 600 mm over the Yangtze River valley, was reasonably reproduced by the advanced research WRF model. Based on the simulation, a set of energy budget equations that divided the real meteorological field into the mean and eddy flows were calculated so as to understand the interactions between the precipitation-related eddy flows and their background circulations (BCs). The results indicated that the precipitation-related eddy flows interacted with their BCs intensely during the PHRE. At different layers, the energy cycles showed distinct characteristics. In the upper troposphere, downscaled energy cascade processes appeared, which favored the maintenance of upper-level eddy flows; whereas, a baroclinic energy conversion, which reduced the upper-level jet, also occurred. In the middle troposphere, significant upscaled energy cascade processes, which reflect the eddy flows' reactionary effects on their BCs, appeared. These effects cannot be ignored with respect to the BCs' evolution, and the reactionary effects were stronger in the dynamical field than in the thermodynamical field. In the lower troposphere, a long-lived quasi-stationary lower-level shear line was the direct trigger for the PHRE. The corresponding eddy flows were sustained mainly through the baroclinic energy conversion associated with convection activities. Alongside this, the downscaled energy cascade processes of kinetic energy, which reflect the direct influences of BCs on the precipitation-related eddy flows, were also favorable. A downscaled energy cascade of exergy also appeared in the lower troposphere, which favored the precipitation-related eddy flow indirectly via the baroclinic energy conversion.

  9. Solids Accumulation Scouting Studies

    SciTech Connect

    Duignan, M. R.; Steeper, T. J.; Steimke, J. L.

    2012-09-26

    The objective of Solids Accumulation activities was to perform scaled testing to understand the behavior of remaining solids in a Double Shell Tank (DST), specifically AW-105, at Hanford during multiple fill, mix, and transfer operations. It is important to know if fissionable materials can concentrate when waste is transferred from staging tanks prior to feeding waste treatment plants. Specifically, there is a concern that large, dense particles containing plutonium could accumulate in poorly mixed regions of a blend tank heel for tanks that employ mixing jet pumps. At the request of the DOE Hanford Tank Operations Contractor, Washington River Protection Solutions, the Engineering Development Laboratory of the Savannah River National Laboratory performed a scouting study in a 1/22-scale model of a waste staging tank to investigate this concern and to develop measurement techniques that could be applied in a more extensive study at a larger scale. Simulated waste tank solids: Gibbsite, Zirconia, Sand, and Stainless Steel, with stainless steel particles representing the heavier particles, e.g., plutonium, and supernatant were charged to the test tank and rotating liquid jets were used to mix most of the solids while the simulant was pumped out. Subsequently, the volume and shape of the mounds of residual solids and the spatial concentration profiles for the surrogate for heavier particles were measured. Several techniques were developed and equipment designed to accomplish the measurements needed and they included: 1. Magnetic particle separator to remove simulant stainless steel solids. A device was designed and built to capture these solids, which represent the heavier solids during a waste transfer from a staging tank. 2. Photographic equipment to determine the volume of the solids mounds. The mounds were photographed as they were exposed at different tank waste levels to develop a composite of topographical areas. 3. Laser rangefinders to determine the volume of

  10. Eddy current pulsed phase thermography considering volumetric induction heating for delamination evaluation in carbon fiber reinforced polymers

    NASA Astrophysics Data System (ADS)

    Yang, Ruizhen; He, Yunze

    2015-06-01

    Anisotropy and inhomogeneity of carbon fiber reinforced polymers (CFRPs) result in that many traditional non-destructive inspection techniques are inapplicable on the delamination evaluation. This letter introduces eddy current pulsed phase thermography (ECPPT) for CFRPs evaluation considering volumetric induction heating due to small electrical conductivity, abnormal thermal wave propagation, and Fourier analysis. The proposed methods were verified through experimental studies under transmission and reflection modes. Using ECPPT, the influence of the non-uniform heating effect and carbon fiber structures can be suppressed, and then delamination detectability can be improved dramatically over eddy current pulsed thermography.

  11. Modeling Mesoscale Eddies in the North Atlantic Ocean

    NASA Technical Reports Server (NTRS)

    Chao, Yi

    1999-01-01

    Ocean modeling plays an important role in understanding the current climatic conditions and predicting the future climate change. Modeling the ocean at eddy-permitting and/or eddy resolving resolutions (1/3 degree or higher) has a two-fold objective. One part is to represent the ocean as realistically as possible, because mesoscale eddies have an impact on the large-scale circulation. The second objective is to learn how to represent effects of mesoscale eddies without explicitly resolving them. This is particularly important for climate models which cannot be run at eddy-resolving resolutions because of the computational constraints. At JPL, a 1/6 degree latitude by 1/6 degree longitude with 37 vertical levels Atlantic Ocean model has been developed. The model is based on the Parallel Ocean Program (POP) developed at Los Alamos National Laboratory (LANL). Using the 256-processor Cray T3D, we have conducted a 40-year integration of this Atlantic eddy-resolving ocean model. A regional analysis demonstrate that many observed features associated with the Caribbean Sea eddies can be realistically simulated by this model. Analysis of this Atlantic eddy-resolving ocean model further suggests that these Caribbean Sea eddies are connected with eddies formed outside the Caribbean Sea at the confluence of the North Brazil Current (NBC) and the North Equatorial Countercurrent. The diagram of the model simulated surface current shows that the Caribbean eddies ultimately originate in the NBC retroflection region, traveling more than a year from the North Brazil coast through the Lesser Antilles into the Caribbean Sea and eventually into the Gulf of Mexico. Additional information is contained in the original.

  12. Bio-optical footprints created by mesoscale eddies in the Sargasso Sea

    NASA Astrophysics Data System (ADS)

    Siegel, D. A.; Peterson, P.; McGillicuddy, D. J., Jr.; Maritorena, S.; Nelson, N. B.

    2011-07-01

    We investigate the bio-optical footprints made by mesoscale eddies in the Sargasso Sea and the processes that create them through an eddy-centric approach. Many (>10,000) eddies are identified and followed in time using satellite altimetry observations and the spatial ocean color patterns surrounding each eddy are assessed. We find through a sequence of statistical hypothesis tests that not one but several mechanisms (i.e., eddy pumping, eddy advection and eddy-Ekman pumping) are responsible for the spatial-temporal ocean color patterns following individual eddies. Both eddy pumping and the eddy-Ekman pumping mechanisms alter subsurface nutrient distributions thereby driving biogeochemical cycles, while the eddy advection mechanism to first order stirs existing horizontal gradients in bio-optical properties. This work illustrates both the promise and some of the limitations of satellite observations for assessing the biogeochemical impacts of mesoscale eddies.

  13. Towards a consistent eddy-covariance processing: an intercomparison of EddyPro and TK3

    NASA Astrophysics Data System (ADS)

    Fratini, G.; Mauder, M.

    2014-03-01

    A comparison of two popular eddy-covariance (EC) software packages is presented, namely EddyPro and TK3. Two about one-month long test datasets were processed, representing typical instrumental setups, i.e. CSAT3/LI-7500 above grassland and Solent R3/LI-6262 above a forest. The resulting fluxes and quality flags were compared. Achieving a satisfying agreement and understanding residual discrepancies required several iterations and interventions of different nature, spanning from simple software reconfiguration to actual code manipulations. In this paper, we document our comparison exercise and show that the two software packages can provide utterly satisfying agreement when properly configured. Our main aim, however, is to stress the complexity of performing a rigorous comparison of EC software. We show that discriminating actual discrepancies in the results from inconsistencies in the software configuration requires deep knowledge of both software packages and of the eddy-covariance method itself. In some instances, it may be even beyond the possibility of the investigator who does not control the source code. Being the developers of EddyPro and TK3, we could discuss the comparison at all levels of details and this proved necessary to achieve a full understanding. As a further consequence, we also suggest that, to the aim of assuring consistency and comparability of centralized flux databases, and for a confident use of eddy fluxes in synthesis studies on the regional, continental and global scale, researchers rely on established software, notably those that have been extensively validated in documented intercomparisons.

  14. Magnetoresistive Flux Focusing Eddy Current Flaw Detection

    NASA Technical Reports Server (NTRS)

    Wincheski, Russell A. (Inventor); Namkung, Min (Inventor); Simpson, John W. (Inventor)

    2005-01-01

    A giant magnetoresistive flux focusing eddy current device effectively detects deep flaws in thick multilayer conductive materials. The probe uses an excitation coil to induce eddy currents in conducting material perpendicularly oriented to the coil s longitudinal axis. A giant magnetoresistive (GMR) sensor, surrounded by the excitation coil, is used to detect generated fields. Between the excitation coil and GMR sensor is a highly permeable flux focusing lens which magnetically separates the GMR sensor and excitation coil and produces high flux density at the outer edge of the GMR sensor. The use of feedback inside the flux focusing lens enables complete cancellation of the leakage fields at the GMR sensor location and biasing of the GMR sensor to a location of high magnetic field sensitivity. In an alternate embodiment, a permanent magnet is positioned adjacent to the GMR sensor to accomplish the biasing. Experimental results have demonstrated identification of flaws up to 1 cm deep in aluminum alloy structures. To detect deep flaws about circular fasteners or inhomogeneities in thick multi-layer conductive materials, the device is mounted in a hand-held rotating probe assembly that is connected to a computer for system control, data acquisition, processing and storage.

  15. Magnetoresistive flux focusing eddy current flaw detection

    NASA Technical Reports Server (NTRS)

    Wincheski, Russell A. (Inventor); Namkung, Min (Inventor); Simpson, John W. (Inventor)

    2005-01-01

    A giant magnetoresistive flux focusing eddy current device effectively detects deep flaws in thick multilayer conductive materials. The probe uses an excitation coil to induce eddy currents in conducting material perpendicularly oriented to the coil's longitudinal axis. A giant magnetoresistive (GMR) sensor, surrounded by the excitation coil, is used to detect generated fields. Between the excitation coil and GMR sensor is a highly permeable flux focusing lens which magnetically separates the GMR sensor and excitation coil and produces high flux density at the outer edge of the GMR sensor. The use of feedback inside the flux focusing lens enables complete cancellation of the leakage fields at the GMR sensor location and biasing of the GMR sensor to a location of high magnetic field sensitivity. In an alternate embodiment, a permanent magnet is positioned adjacent to the GMR sensor to accomplish the biasing. Experimental results have demonstrated identification of flaws up to 1 cm deep in aluminum alloy structures. To detect deep flaws about circular fasteners or inhomogeneities in thick multilayer conductive materials, the device is mounted in a hand-held rotating probe assembly that is connected to a computer for system control, data acquisition, processing and storage.

  16. Structural state testing using eddy current inversion

    NASA Astrophysics Data System (ADS)

    Dolgov, N. Y.; Chernov, L. A.

    2000-05-01

    The inverse eddy current problem can be described as the task of reconstructing an unknown distribution of electrical conductivity from eddy-current probe voltage measurements recorded as function of excitation frequency. Conductivity variation may be a result of surface processing with substances like hydrogen and carbon or surface heating. We developed mathematical reasons and supporting software for inverse conductivity profiling. Inverse problem was solved for layered plane and cylindrical conductors. Because the inverse problem is nonlinear, we propose using an iterative algorithm which can be formalized as the minimization of an error functional related to the difference between the probe voltages theoretically predicted by the direct problem solving and the measured probe voltages. Numerical results were obtained for some models of conductivity distribution. It was shown that inverse problem can be solved exactly in case of correct measurements. Good estimation of the true conductivity distribution takes place also for measurement noise about 2 percent but in the case of 5 percent error, results are worse.

  17. Eddy Current System and Method for Crack Detection

    NASA Technical Reports Server (NTRS)

    Wincheski, Russell A. (Inventor); Simpson, John W. (Inventor)

    2012-01-01

    An eddy current system and method enables detection of sub-surface damage in a cylindrical object. The invention incorporates a dual frequency, orthogonally wound eddy current probe mounted on a stepper motor-controlled scanning system. The system is designed to inspect for outer surface damage from the interior of the cylindrical object.

  18. Eddies around Guam, an island in the Mariana Islands group

    NASA Astrophysics Data System (ADS)

    Wolanski, E.; Richmond, R. H.; Davis, G.; Deleersnijder, E.; Leben, R. R.

    2003-06-01

    Near-surface currents around Guam, a 35 km long, slab-shaped island in the Mariana Islands group, were estimated from current meters, satellite-derived surface topography, and a numerical model. A dominant northwestward-flowing North Equatorial Current prevailed from June to December 2000, with speeds typically 0.1-0.2 m s -1, generating unsteady eddies in the lee of Guam. A number of transient eddies off the tips of the island were apparent, the smallest eddies were at the scale of local topographic features such as headlands and embayments, while other eddies were island size. In addition to eddies off the tips of the island, a large (200 km in diameter) cyclonic oceanic eddy was advected eastward past Guam during the last 2 weeks of August 2000. Centered on Guam for a few days, this eddy formed elsewhere and impinged on the island generating anticlockwise currents around the island of up to 0.5 m s -1. It is suggested that these eddies are sufficiently energetic to return fish and coral eggs and larvae to their natal reefs in Guam, thereby enabling self-seeding of coral reefs in Guam. The numerical model also predicts that large (up to 30 m amplitude) island-generated internal waves may occur around Guam; however, no observations are presently available to support this prediction.

  19. Anisotropy of eddy variability in the global ocean

    NASA Astrophysics Data System (ADS)

    Stewart, K. D.; Spence, P.; Waterman, S.; Sommer, J. Le; Molines, J.-M.; Lilly, J. M.; England, M. H.

    2015-11-01

    The anisotropy of eddy variability in the global ocean is examined in geostrophic surface velocities derived from satellite observations and in the horizontal velocities of a 1/12° global ocean model. Eddy anisotropy is of oceanographic interest as it is through anisotropic velocity fluctuations that the eddy and mean-flow fields interact dynamically. This study is timely because improved observational estimates of eddy anisotropy will soon be available with Surface Water and Ocean Topography (SWOT) altimetry data. We find there to be good agreement between the characteristics and distributions of eddy anisotropy from the present satellite observations and model ocean surface. In the model, eddy anisotropy is found to have significant vertical structure and is largest close to the ocean bottom, where the anisotropy aligns with the underlying isobaths. The highly anisotropic bottom signal is almost entirely contained in the barotropic variability. Upper-ocean variability is predominantly baroclinic and the alignment is less sensitive to the underlying bathymetry. These findings offer guidance for introducing a parameterization of eddy feedbacks, based on the eddy kinetic energy and underlying bathymetry, to operate on the barotropic flow and better account for the effects of barotropic Reynolds stresses unresolved in coarse-resolution ocean models.

  20. Eddy Currents: Levitation, Metal Detectors, and Induction Heating

    ERIC Educational Resources Information Center

    Wouch, G.; Lord, A. E., Jr.

    1978-01-01

    A simple and accessible calculation is given of the effects of eddy currents for a sphere in the field of a single circular loop of alternating current. These calculations should help toward the inclusion of eddy current effects in upper undergraduate physics courses. (BB)

  1. Eddy development and motion in the Caribbean Sea

    NASA Astrophysics Data System (ADS)

    Andrade, Carlos A.; Barton, Eric D.

    2000-11-01

    Eddy motion in the Caribbean Sea is described on the basis of sea level anomalies deduced from ERS-1 altimetry data corrected with TOPEX/Poseidon data during the 15 months of the Exact Repeat Mission (October 1992 to December 1993). Both cyclones and anticyclones were observed in the satellite data as anomalies originating in the Venezuelan Basin or entering the Caribbean through the Antillean passages, mainly the St. Lucia Channel, Anegada Passage, and north of Trinidad. The diameter of the eddies ranged from a few tens of kilometers to 700 km. Advection speeds were typically 20-30 cm s-1 and the eddies were energetic (kinetic energy > 0.6 m2 s-2). Their lifetime of 3-4 months was determined, in general, by their interaction with topography. Most eddy activity was eroded and disappeared at the Central American Rise area, although a few eddies crossed into the Cayman Sea through the Chibcha Channel. Some eddies also entered the Cayman Sea from outside the Caribbean through the Windward Passage. The Panama-Colombia Gyre was evident only during the tropical rainy season. A large cyclonic eddy was formed there during the period of maximum precipitation, when strong meridional salinity and wind speed gradients occurred. Eddy production in the central Caribbean appears to be associated with the interaction of the meandering Caribbean Current and the strong wind curl.

  2. The Energetics of Transient Eddies in the Martian Northern Hemisphere

    NASA Astrophysics Data System (ADS)

    Battalio, Joseph Michael; Szunyogh, Istvan; Lemmon, Mark T.

    2016-10-01

    The energetics of northern hemisphere transient waves in the Mars Analysis Correction Data Assimilation is analyzed. Three periods between the fall and spring equinoxes (Ls=200°-230°, 255°-285°, and 330°-360°) during three Mars Years are selected to exemplify the fall, winter, and spring wave activity. Fall and spring eddy energetics is similar with some inter-annual and inter-seasonal variability, but winter eddy kinetic energy and its transport are strongly reduced in intensity as a result of the solsticial pause in eddy activity. Barotropic energy conversion acts as a sink of eddy kinetic energy throughout the northern hemisphere eddy period with little reduction in amplitude during the solsticial pause. Baroclinic energy conversion acts as a source in fall and spring but disappears during the winter period as a result of the stabilized vertical shear profile of the westerly jet around winter solstice.

  3. Biogeochemical Properties of Eddies in the California Current System

    NASA Astrophysics Data System (ADS)

    Chenillat, Fanny; Franks, Peter J. S.; Combes, Vincent

    2016-04-01

    The California Current System (CCS) is a coastal upwelling system characterized by intense mesoscale activity. This mesoscale activity plays a critical role in modulating biological production and exporting coastal biogeochemical materials offshore. To characterize and quantify the ability of mesoscale eddies to affect local and regional planktonic ecosystems in the CCS, we analyzed a 10-year-long physical-biological model simulation - with 5km horizontal resolution - using eddy detection and tracking to isolate the dynamics in cyclonic and anticyclonic eddies. At any given time, ~8% of the model domain was covered by eddies, and this small area belies ~50% of the cross-shelf biological transport. As they propagate westward across the shelf, cyclonic eddies efficiently transport coastal planktonic organisms, and maintain locally elevated production, Anticyclones, on the other hand, have a limited impact on local production.

  4. Movements of foraging king penguins through marine mesoscale eddies

    PubMed Central

    Cotté, Cédric; Park, Young-Hyang; Guinet, Christophe; Bost, Charles-André

    2007-01-01

    Despite increasing evidence that marine predators associate with mesoscale eddies, how these marine features influence foraging movements is still unclear. This study investigates the relationship of at-sea movements of king penguins to mesoscale eddies using oceanographic remote sensing and movement data from 43 individual trips over 4 years. Simultaneous satellite measurements provided information on gradients of sea surface temperature and currents associated with eddies determined from altimetry. Penguins tended to swim rapidly with currents as they travelled towards foraging zones. Swimming speed indicative of foraging occurred within mesoscale fronts and strong currents associated with eddies at the Polar Front. These results demonstrate the importance of mesoscale eddies in directing foraging efforts to allow predators to rapidly get to rich areas where high concentrations of prey are likely to be encountered. When returning to the colony to relieve the incubating partner or to feed the chick, the birds followed a direct and rapid path, seemingly ignoring currents. PMID:17669726

  5. Eddy correlation fluxes of trace gases using a tandem mass spectrometer

    NASA Astrophysics Data System (ADS)

    Shaw, William J.; Spicer, Chester W.; Kenny, Donald V.

    This paper describes a field evaluation of a tandem mass spectrometer (TAGA) for use in measuring turbulence fluxes of trace gases. Measurements were made over a two-day period in a fallow farm field west of Columbus, OH. The results show that for weakly adsorbing species such as acetone, the effective time constant for the TAGA is <0.1 s, and the device can be used for eddy correlation flux measurements with little need for corrections. The effective time constant is longer for adsorbing species, such as ammonia, but spectral corrections can permit flux estimates for these species as well. This paper presents the first reported measurements of fluxes of acetone, formic acid, and ammonia using the eddy correlation technique.

  6. Large eddy simulation of mixing between hot and cold sodium flows - comparison with experiments

    SciTech Connect

    Simoneau, J.P.; Noe, H.; Menant, B.

    1995-09-01

    The large eddy simulation is becoming a potential powerful tool for the calculation of turbulent flows. In nuclear liquid metal cooled fast reactors, the knowledge of the turbulence characteristics is of great interest for the prediction and the analysis of thermal stripping phenomena. The objective of this paper is to give a contribution in the evaluation of the large eddy simulation technique is an individual case. The problem chosen is the case of the mixing between hot and cold sodium flows. The computations are compared with available sodium tests. This study shows acceptable qualitative results but the simple model used is not able to predict the turbulence characteristics. More complex models including larger domains around the fluctuating zone and fluctuating boundary conditions could be necessary. Validation works are continuing.

  7. On the interactions between planetary geostrophy and mesoscale eddies

    NASA Astrophysics Data System (ADS)

    Grooms, Ian; Julien, Keith; Fox-Kemper, Baylor

    2011-04-01

    Multiscale asymptotics are used to derive three systems of equations connecting the planetary geostrophic (PG) equations for gyre-scale flow to a quasigeostrophic (QG) equation set for mesoscale eddies. Pedlosky (1984), following similar analysis, found eddy buoyancy fluxes to have only a small effect on the large-scale flow; however, numerical simulations disagree. While the impact of eddies is relatively small in most regions, in keeping with Pedlosky's result, eddies have a significant effect on the mean flow in the vicinity of strong, narrow currents. First, the multiple-scales analysis of Pedlosky is reviewed and amplified. Novel results of this analysis include new multiple-scales models connecting large-scale PG equations to sets of QG eddy equations. However, only introducing anisotropic scaling of the large-scale coordinates allows us to derive a model with strong two-way coupling between the QG eddies and the PG mean flow. This finding reconciles the analysis with simulations, viz. that strong two-way coupling is observed in the vicinity of anisotropic features of the mean flow like boundary currents and jets. The relevant coupling terms are shown to be eddy buoyancy fluxes. Using the Gent-McWilliams parameterization to approximate these fluxes allows solution of the PG equations with closed tracer fluxes in a closed domain, which is not possible without mesoscale eddy (or other small-scale) effects. The boundary layer width is comparable to an eddy mixing length when the typical eddy velocity is taken to be the long Rossby wave phase speed, which is the same result found by Fox-Kemper and Ferrari (2009) in a reduced gravity layer.

  8. Correcting eddy-covariance flux underestimates over a grassland.

    SciTech Connect

    Twine, T. E.; Kustas, W. P.; Norman, J. M.; Cook, D. R.; Houser, P. R.; Meyers, T. P.; Prueger, J. H.; Starks, P. J.; Wesely, M. L.; Environmental Research; Univ. of Wisconsin at Madison; DOE; National Aeronautics and Space Administration; National Oceanic and Atmospheric Administrationoratory

    2000-06-08

    Independent measurements of the major energy balance flux components are not often consistent with the principle of conservation of energy. This is referred to as a lack of closure of the surface energy balance. Most results in the literature have shown the sum of sensible and latent heat fluxes measured by eddy covariance to be less than the difference between net radiation and soil heat fluxes. This under-measurement of sensible and latent heat fluxes by eddy-covariance instruments has occurred in numerous field experiments and among many different manufacturers of instruments. Four eddy-covariance systems consisting of the same models of instruments were set up side-by-side during the Southern Great Plains 1997 Hydrology Experiment and all systems under-measured fluxes by similar amounts. One of these eddy-covariance systems was collocated with three other types of eddy-covariance systems at different sites; all of these systems under-measured the sensible and latent-heat fluxes. The net radiometers and soil heat flux plates used in conjunction with the eddy-covariance systems were calibrated independently and measurements of net radiation and soil heat flux showed little scatter for various sites. The 10% absolute uncertainty in available energy measurements was considerably smaller than the systematic closure problem in the surface energy budget, which varied from 10 to 30%. When available-energy measurement errors are known and modest, eddy-covariance measurements of sensible and latent heat fluxes should be adjusted for closure. Although the preferred method of energy balance closure is to maintain the Bowen-ratio, the method for obtaining closure appears to be less important than assuring that eddy-covariance measurements are consistent with conservation of energy. Based on numerous measurements over a sorghum canopy, carbon dioxide fluxes, which are measured by eddy covariance, are underestimated by the same factor as eddy covariance evaporation

  9. Eddy pump dredging: Does it produce water quality impacts?

    SciTech Connect

    Creek, K.D.; Sagraves, T.H.

    1995-12-31

    During a prototype demonstration at Pacific Gas and Electric Company`s (PG&E`s) Cresta Reservoir, the feasibility of a new dredging technique was tested for its reported ability to produce only minimal water quality impacts. The technique, developed by PBMK Consultants and Engineers, uses the EDDY Pump, a patented submerged slurry pump system with a higher solids-to-liquid ratio and lower re-suspension of sediment than achieved by conventional suction dredging. Turbidity and total suspended solids concentrations of water samples collected adjacent to and downstream of the pump head were similar to those of samples collected adjacent to and upstream of the pump head. Dissolved oxygen downstream of the pump head remained near saturation. The dredged sediment was pumped 600 m upstream of the pump head and discharged back to the surface of Cresta Reservoir. Increases in turbidity and total suspended solids downstream of the discharge site were minor. Throughout the demonstration, turbidity levels and total suspended solids concentrations remained well below allowable levels set by the California Regional Water Quality Control Board - no more than a 25 NTU turbidity increase over ambient background nor more than 80 mg/I total suspended solids, absolute.

  10. Improved eddy-current inspection for steam generator tubing

    SciTech Connect

    Dodd, C.V.; Pate, J.R.; Allen, J.D. Jr.; Allen , Knoxville, TN )

    1989-01-01

    Computer programs have been written to allow the analysis of different types of eddy-current probes and their performance under different steam generator test conditions. The probe types include the differential bobbin probe, the absolute bobbin probe, the pancake probe and the reflection probe. The generator test conditions include tube supports, copper deposits, magnetite deposits, denting, wastage, pitting, cracking and IGA. These studies are based mostly on computed values, with the limited number of test specimens available used to verify the computed results. The instrument readings were computed for a complete matrix of the different test conditions, and then the test conditions determined as a function of the readings by a least-squares technique. A comparison was made of the errors in fit and instrument drift for the different probe types. The computations of the change in instrument reading due to the defects have led to an inversion'' technique in which the defect properties can be computed from the instrument readings. This has been done both experimentally and analytically for each of these probe types. 3 refs., 13 figs., 1 tab.

  11. Large eddy simulation of a pumped- storage reservoir

    NASA Astrophysics Data System (ADS)

    Launay, Marina; Leite Ribeiro, Marcelo; Roman, Federico; Armenio, Vincenzo

    2016-04-01

    The last decades have seen an increasing number of pumped-storage hydropower projects all over the world. Pumped-storage schemes move water between two reservoirs located at different elevations to store energy and to generate electricity following the electricity demand. Thus the reservoirs can be subject to important water level variations occurring at the daily scale. These new cycles leads to changes in the hydraulic behaviour of the reservoirs. Sediment dynamics and sediment budgets are modified, sometimes inducing problems of erosion and deposition within the reservoirs. With the development of computer performances, the use of numerical techniques has become popular for the study of environmental processes. Among numerical techniques, Large Eddy Simulation (LES) has arisen as an alternative tool for problems characterized by complex physics and geometries. This work uses the LES-COAST Code, a LES model under development in the framework of the Seditrans Project, for the simulation of an Upper Alpine Reservoir of a pumped-storage scheme. Simulations consider the filling (pump mode) and emptying (turbine mode) of the reservoir. The hydraulic results give a better understanding of the processes occurring within the reservoir. They are considered for an assessment of the sediment transport processes and of their consequences.

  12. The prospect of using large eddy and detached eddy simulations in engineering design, and the research required to get there

    PubMed Central

    Larsson, Johan; Wang, Qiqi

    2014-01-01

    In this paper, we try to look into the future to envision how large eddy and detached eddy simulations will be used in the engineering design process about 20–30 years from now. Some key challenges specific to the engineering design process are identified, and some of the critical outstanding problems and promising research directions are discussed. PMID:25024421

  13. Investigation of a miRNA-Induced Gene Silencing Technique in Petunia Reveals Alterations in miR173 Precursor Processing and the Accumulation of Secondary siRNAs from Endogenous Genes

    PubMed Central

    Han, Yao; Zhang, Bin; Qin, Xiaoting; Li, Mingyang; Guo, Yulong

    2015-01-01

    MIGS (miRNA-induced gene silencing) is a straightforward and efficient gene silencing technique in Arabidopsis. It works by exploiting miR173 to trigger the production of phasiRNAs (phased small interfering RNAs). MIGS can be used in plant species other than Arabidopsis by co-expression of miR173 and target gene fragments fused to an upstream miR173 target site. However, the efficiency and technical mechanisms have not been thoroughly investigated in other plants. In this work, two vectors, pMIGS-chs and pMIGS-pds, were constructed and transformed into petunia plants. The transgenic plants showed CHS (chalcone synthase) and PDS (phytoene desaturase) gene-silencing phenotypes respectively, indicating that MIGS functions in petunia. MIGS-chs plants were used to investigate the mechanisms of this technique in petunia. Results of 5′- RACE showed that the miR173 target site was cleaved at the expected position and that endogenous CHS genes were cut at multiple positions. Small RNA deep sequencing analysis showed that the processing of Arabidopsis miR173 precursors in MIGS-chs transgenic petunia plants did not occur in exactly the same way as in Arabidopsis, suggesting differences in the machinery of miRNA processing between plant species. Small RNAs in-phase with the miR173 cleavage register were produced immediately downstream from the cleavage site and out-of-phase small RNAs were accumulated at relatively high levels from processing cycle 5 onwards. Secondary siRNAs were generated from multiple sites of endogenous CHS-A and CHS-J genes, indicating that miR173 cleavage induced siRNAs have the same ability to initiate siRNA transitivity as the siRNAs functioning in co-suppression and hpRNA silencing. On account of the simplicity of vector construction and the transitive amplification of signals from endogenous transcripts, MIGS is a good alternative gene silencing method for plants, especially for silencing a cluster of homologous genes with redundant functions. PMID

  14. Investigation of a miRNA-Induced Gene Silencing Technique in Petunia Reveals Alterations in miR173 Precursor Processing and the Accumulation of Secondary siRNAs from Endogenous Genes.

    PubMed

    Han, Yao; Zhang, Bin; Qin, Xiaoting; Li, Mingyang; Guo, Yulong

    2015-01-01

    MIGS (miRNA-induced gene silencing) is a straightforward and efficient gene silencing technique in Arabidopsis. It works by exploiting miR173 to trigger the production of phasiRNAs (phased small interfering RNAs). MIGS can be used in plant species other than Arabidopsis by co-expression of miR173 and target gene fragments fused to an upstream miR173 target site. However, the efficiency and technical mechanisms have not been thoroughly investigated in other plants. In this work, two vectors, pMIGS-chs and pMIGS-pds, were constructed and transformed into petunia plants. The transgenic plants showed CHS (chalcone synthase) and PDS (phytoene desaturase) gene-silencing phenotypes respectively, indicating that MIGS functions in petunia. MIGS-chs plants were used to investigate the mechanisms of this technique in petunia. Results of 5'- RACE showed that the miR173 target site was cleaved at the expected position and that endogenous CHS genes were cut at multiple positions. Small RNA deep sequencing analysis showed that the processing of Arabidopsis miR173 precursors in MIGS-chs transgenic petunia plants did not occur in exactly the same way as in Arabidopsis, suggesting differences in the machinery of miRNA processing between plant species. Small RNAs in-phase with the miR173 cleavage register were produced immediately downstream from the cleavage site and out-of-phase small RNAs were accumulated at relatively high levels from processing cycle 5 onwards. Secondary siRNAs were generated from multiple sites of endogenous CHS-A and CHS-J genes, indicating that miR173 cleavage induced siRNAs have the same ability to initiate siRNA transitivity as the siRNAs functioning in co-suppression and hpRNA silencing. On account of the simplicity of vector construction and the transitive amplification of signals from endogenous transcripts, MIGS is a good alternative gene silencing method for plants, especially for silencing a cluster of homologous genes with redundant functions.

  15. Investigation of a miRNA-Induced Gene Silencing Technique in Petunia Reveals Alterations in miR173 Precursor Processing and the Accumulation of Secondary siRNAs from Endogenous Genes.

    PubMed

    Han, Yao; Zhang, Bin; Qin, Xiaoting; Li, Mingyang; Guo, Yulong

    2015-01-01

    MIGS (miRNA-induced gene silencing) is a straightforward and efficient gene silencing technique in Arabidopsis. It works by exploiting miR173 to trigger the production of phasiRNAs (phased small interfering RNAs). MIGS can be used in plant species other than Arabidopsis by co-expression of miR173 and target gene fragments fused to an upstream miR173 target site. However, the efficiency and technical mechanisms have not been thoroughly investigated in other plants. In this work, two vectors, pMIGS-chs and pMIGS-pds, were constructed and transformed into petunia plants. The transgenic plants showed CHS (chalcone synthase) and PDS (phytoene desaturase) gene-silencing phenotypes respectively, indicating that MIGS functions in petunia. MIGS-chs plants were used to investigate the mechanisms of this technique in petunia. Results of 5'- RACE showed that the miR173 target site was cleaved at the expected position and that endogenous CHS genes were cut at multiple positions. Small RNA deep sequencing analysis showed that the processing of Arabidopsis miR173 precursors in MIGS-chs transgenic petunia plants did not occur in exactly the same way as in Arabidopsis, suggesting differences in the machinery of miRNA processing between plant species. Small RNAs in-phase with the miR173 cleavage register were produced immediately downstream from the cleavage site and out-of-phase small RNAs were accumulated at relatively high levels from processing cycle 5 onwards. Secondary siRNAs were generated from multiple sites of endogenous CHS-A and CHS-J genes, indicating that miR173 cleavage induced siRNAs have the same ability to initiate siRNA transitivity as the siRNAs functioning in co-suppression and hpRNA silencing. On account of the simplicity of vector construction and the transitive amplification of signals from endogenous transcripts, MIGS is a good alternative gene silencing method for plants, especially for silencing a cluster of homologous genes with redundant functions. PMID

  16. Effect of reactions in small eddies on biomass gasification with eddy dissipation concept - Sub-grid scale reaction model.

    PubMed

    Chen, Juhui; Yin, Weijie; Wang, Shuai; Meng, Cheng; Li, Jiuru; Qin, Bai; Yu, Guangbin

    2016-07-01

    Large-eddy simulation (LES) approach is used for gas turbulence, and eddy dissipation concept (EDC)-sub-grid scale (SGS) reaction model is employed for reactions in small eddies. The simulated gas molar fractions are in better agreement with experimental data with EDC-SGS reaction model. The effect of reactions in small eddies on biomass gasification is emphatically analyzed with EDC-SGS reaction model. The distributions of the SGS reaction rates which represent the reactions in small eddies with particles concentration and temperature are analyzed. The distributions of SGS reaction rates have the similar trend with those of total reactions rates and the values account for about 15% of the total reactions rates. The heterogeneous reaction rates with EDC-SGS reaction model are also improved during the biomass gasification process in bubbling fluidized bed.

  17. Effect of reactions in small eddies on biomass gasification with eddy dissipation concept - Sub-grid scale reaction model.

    PubMed

    Chen, Juhui; Yin, Weijie; Wang, Shuai; Meng, Cheng; Li, Jiuru; Qin, Bai; Yu, Guangbin

    2016-07-01

    Large-eddy simulation (LES) approach is used for gas turbulence, and eddy dissipation concept (EDC)-sub-grid scale (SGS) reaction model is employed for reactions in small eddies. The simulated gas molar fractions are in better agreement with experimental data with EDC-SGS reaction model. The effect of reactions in small eddies on biomass gasification is emphatically analyzed with EDC-SGS reaction model. The distributions of the SGS reaction rates which represent the reactions in small eddies with particles concentration and temperature are analyzed. The distributions of SGS reaction rates have the similar trend with those of total reactions rates and the values account for about 15% of the total reactions rates. The heterogeneous reaction rates with EDC-SGS reaction model are also improved during the biomass gasification process in bubbling fluidized bed. PMID:27010338

  18. Pulsed eddy current inspection of CF-188 inner wing spar

    NASA Astrophysics Data System (ADS)

    Horan, Peter Francis

    Royal Canadian Air Force (RCAF) CF-188 Hornet aircraft engineering authorities have stated a requirement for a Non-Destructive Evaluation (NDE) technique to detect Stress Corrosion Cracking (SCC) in the inner wing spars without fastener or composite wing skin removal. Current radiographic inspections involve significant aircraft downtime, and Pulsed Eddy Current (PEC) inspection is proposed as a solution. The aluminum inner wing spars of CF-188 Hornet aircraft may undergo stress corrosion cracking (SCC) along the spar between the fasteners that secure carbon-fiber/ epoxy composite skin to the wing. Inspection of the spar through the wing skin is required to avoid wing disassembly. The thickness of the wing skin varies between 8 and 20 mm (0.3 to 0.8 inch) and fasteners may be either titanium or ferrous. PEC generated by a probe centered over a fastener, demonstrates capability of detecting simulated cracks within spars with the wing skin present. Comparison of signals from separate sensors, mounted to either side of the excitation coil, is used to detect differences in induced eddy current fields, which arise in the presence of cracks. To overcome variability in PEC signal response due to variation in 1) skin thickness, 2) fastener material and size, and 3) centering over fasteners, a large calibration data set is acquired. Multi-dimensional scores from a Modified Principal Components Analysis (PCA) of the data are reduced to one dimension (1D) using a Discriminant Analysis method. Under inspection conditions, calibrated PCA scores combined with discriminant analysis permit rapid real time go/no-go PEC detection of cracks in CF-188 inner wing spar. Probe designs using both pickup coils and Giant Magnetoresistive (GMR) sensors were tested on samples with the same ferrous and titanium fasteners found on the CF-188. Flaws were correctly detected at lift-offs of up to 21mm utilizing a variety of insulating skin materials simulating the carbon-fibre reinforced polymer

  19. Statistical Ensemble of Large Eddy Simulations

    NASA Technical Reports Server (NTRS)

    Carati, Daniele; Rogers, Michael M.; Wray, Alan A.; Mansour, Nagi N. (Technical Monitor)

    2001-01-01

    A statistical ensemble of large eddy simulations (LES) is run simultaneously for the same flow. The information provided by the different large scale velocity fields is used to propose an ensemble averaged version of the dynamic model. This produces local model parameters that only depend on the statistical properties of the flow. An important property of the ensemble averaged dynamic procedure is that it does not require any spatial averaging and can thus be used in fully inhomogeneous flows. Also, the ensemble of LES's provides statistics of the large scale velocity that can be used for building new models for the subgrid-scale stress tensor. The ensemble averaged dynamic procedure has been implemented with various models for three flows: decaying isotropic turbulence, forced isotropic turbulence, and the time developing plane wake. It is found that the results are almost independent of the number of LES's in the statistical ensemble provided that the ensemble contains at least 16 realizations.

  20. Eddy current losses in passive magnetic bearings

    NASA Astrophysics Data System (ADS)

    Bouty, Olivier

    2002-12-01

    Passive magnetic bearings built with permanent magnets, such as NdFeB (neodynium-iron-boron) or SmCo (samarium-cobalt), are very reliable systems when used for industrial applications such as centrifuges or flywheels, as they do not require any electromagnetic coil supply. Nevertheless, during the rotational motion, gyroscopic effects (like precession) or inhomogeneous magnetization can lead to power losses created by eddy currents flowing over the magnetic materials. This article provides a theoretical description and quantification of these phenomena by means of Ampere's laws. For this purpose, the magnets are assumed to be ring-shaped and axially magnetized. Virtual surface and volume current densities are applied to the calculation of the time-dependent electric field, and consequently to the power loss. Numerical applications are presented for a typical bearing configuration.

  1. Autonomic Closure for Large Eddy Simulation

    NASA Astrophysics Data System (ADS)

    King, Ryan; Hamlington, Peter; Dahm, Werner J. A.

    2015-11-01

    A new autonomic subgrid-scale closure has been developed for large eddy simulation (LES). The approach poses a supervised learning problem that captures nonlinear, nonlocal, and nonequilibrium turbulence effects without specifying a predefined turbulence model. By solving a regularized optimization problem on test filter scale quantities, the autonomic approach identifies a nonparametric function that represents the best local relation between subgrid stresses and resolved state variables. The optimized function is then applied at the grid scale to determine unknown LES subgrid stresses by invoking scale similarity in the inertial range. A priori tests of the autonomic approach on homogeneous isotropic turbulence show that the new approach is amenable to powerful optimization and machine learning methods and is successful for a wide range of filter scales in the inertial range. In these a priori tests, the autonomic closure substantially improves upon the dynamic Smagorinsky model in capturing the instantaneous, statistical, and energy transfer properties of the subgrid stress field.

  2. Eddy current losses in ferromagnetic laminations

    SciTech Connect

    Serpico, C.; Visone, C.; Mayergoyz, I. D.; Basso, V.; Miano, G.

    2000-05-01

    It is demonstrated through the comparison of analytical, numerical, and experimental results that the existence of excess eddy current losses can be explained by the peculiar nature of the nonlinear diffusion of electromagnetic fields in magnetically nonlinear laminations. The essence of this peculiar nature is that nonlinear diffusion occurs as inward progress of almost rectangular profiles of magnetic flux density of variable height. Approximating actual profiles of magnetic flux density by rectangular ones, the problem of nonlinear diffusion can be treated analytically by using a simple model. The accuracy and the limit of applicability of the rectangular profile model are discussed by comparing its predictions with finite elements numerical solutions of nonlinear diffusion equation as well as with experimental results. (c) 2000 American Institute of Physics.

  3. Neural nets and eddy-current testing

    SciTech Connect

    Allen, J.D. Jr.; Dodd, C.V.; Pate, J.R.; Schell, F.M.

    1990-01-01

    Artificial neural networks of a novel type have been trained and tested on a variety of eddy-current flaw signals commonly occurring in nuclear reactor steam generators with the ultimate goal of emulating, at least crudely, the vision and reasoning capabilities of the human analyst. The network methodology itself was that of Allen and Schell developed originally for studies of such biologically relevant neural properties as cognitive complementarity and concept formation. Because they are so important to the results obtained, we discuss the general characteristics of the approach in the Preamble. In Section I we describe the relevant aspects of the neural network configuration presently in use and in Section II the method by which the artificial neural systems have been trained. Finally, we discuss results of the training process for systems explored.

  4. Large eddy simulations in 2030 and beyond

    PubMed Central

    Piomelli, U

    2014-01-01

    Since its introduction, in the early 1970s, large eddy simulations (LES) have advanced considerably, and their application is transitioning from the academic environment to industry. Several landmark developments can be identified over the past 40 years, such as the wall-resolved simulations of wall-bounded flows, the development of advanced models for the unresolved scales that adapt to the local flow conditions and the hybridization of LES with the solution of the Reynolds-averaged Navier–Stokes equations. Thanks to these advancements, LES is now in widespread use in the academic community and is an option available in most commercial flow-solvers. This paper will try to predict what algorithmic and modelling advancements are needed to make it even more robust and inexpensive, and which areas show the most promise. PMID:25024415

  5. Large eddy simulation of cavitating flows

    NASA Astrophysics Data System (ADS)

    Gnanaskandan, Aswin; Mahesh, Krishnan

    2014-11-01

    Large eddy simulation on unstructured grids is used to study hydrodynamic cavitation. The multiphase medium is represented using a homogeneous equilibrium model that assumes thermal equilibrium between the liquid and the vapor phase. Surface tension effects are ignored and the governing equations are the compressible Navier Stokes equations for the liquid/vapor mixture along with a transport equation for the vapor mass fraction. A characteristic-based filtering scheme is developed to handle shocks and material discontinuities in non-ideal gases and mixtures. A TVD filter is applied as a corrector step in a predictor-corrector approach with the predictor scheme being non-dissipative and symmetric. The method is validated for canonical one dimensional flows and leading edge cavitation over a hydrofoil, and applied to study sheet to cloud cavitation over a wedge. This work is supported by the Office of Naval Research.

  6. Material condition assessment with eddy current sensors

    NASA Technical Reports Server (NTRS)

    Goldfine, Neil J. (Inventor); Washabaugh, Andrew P. (Inventor); Sheiretov, Yanko K. (Inventor); Schlicker, Darrell E. (Inventor); Lyons, Robert J. (Inventor); Windoloski, Mark D. (Inventor); Craven, Christopher A. (Inventor); Tsukernik, Vladimir B. (Inventor); Grundy, David C. (Inventor)

    2010-01-01

    Eddy current sensors and sensor arrays are used for process quality and material condition assessment of conducting materials. In an embodiment, changes in spatially registered high resolution images taken before and after cold work processing reflect the quality of the process, such as intensity and coverage. These images also permit the suppression or removal of local outlier variations. Anisotropy in a material property, such as magnetic permeability or electrical conductivity, can be intentionally introduced and used to assess material condition resulting from an operation, such as a cold work or heat treatment. The anisotropy is determined by sensors that provide directional property measurements. The sensor directionality arises from constructs that use a linear conducting drive segment to impose the magnetic field in a test material. Maintaining the orientation of this drive segment, and associated sense elements, relative to a material edge provides enhanced sensitivity for crack detection at edges.

  7. Eddy-current-damped microelectromechanical switch

    DOEpatents

    Christenson, Todd R.; Polosky, Marc A.

    2009-12-15

    A microelectromechanical (MEM) device is disclosed that includes a shuttle suspended for movement above a substrate. A plurality of permanent magnets in the shuttle of the MEM device interact with a metal plate which forms the substrate or a metal portion thereof to provide an eddy-current damping of the shuttle, thereby making the shuttle responsive to changes in acceleration or velocity of the MEM device. Alternately, the permanent magnets can be located in the substrate, and the metal portion can form the shuttle. An electrical switch closure in the MEM device can occur in response to a predetermined acceleration-time event. The MEM device, which can be fabricated either by micromachining or LIGA, can be used for sensing an acceleration or deceleration event (e.g. in automotive applications such as airbag deployment or seat belt retraction).

  8. Eddy-current-damped microelectromechanical switch

    DOEpatents

    Christenson, Todd R.; Polosky, Marc A.

    2007-10-30

    A microelectromechanical (MEM) device is disclosed that includes a shuttle suspended for movement above a substrate. A plurality of permanent magnets in the shuttle of the MEM device interact with a metal plate which forms the substrate or a metal portion thereof to provide an eddy-current damping of the shuttle, thereby making the shuttle responsive to changes in acceleration or velocity of the MEM device. Alternately, the permanent magnets can be located in the substrate, and the metal portion can form the shuttle. An electrical switch closure in the MEM device can occur in response to a predetermined acceleration-time event. The MEM device, which can be fabricated either by micromachining or LIGA, can be used for sensing an acceleration or deceleration event (e.g. in automotive applications such as airbag deployment or seat belt retraction).

  9. An eddy closure for potential vorticity

    SciTech Connect

    Ringler, Todd D

    2009-01-01

    The Gent-McWilliams (GM) parameterization is extended to include a direct influence in the momentum equation. The extension is carried out in two stages; an analysis of the inviscid system is followed by an analysis of the viscous system. In the inviscid analysis the momentum equation is modified such that potential vorticity is conserved along particle trajectories following a transport velocity that includes the Bolus velocity in a manner exactly analogous to the continuity and tracer equations. In addition (and in contrast to traditional GM closures), the new formulation of the inviscid momentum equation results in a conservative exchange between potential and kinetic forms of energy. The inviscid form of the eddy closure conserves total energy to within an error proportional to the time derivative of the Bolus velocity. The hypothesis that the viscous term in the momentum equation should give rise to potential vorticity being diffused along isopycnals in a manner analogous to other tracers is examined in detail. While the form of the momentum closure that follows from a strict adherence to this hypothesis is not immediately interpretable within the constructs of traditional momentum closures, three approximations to this hypothesis results in a form of dissipation that is consistent with traditional Laplacian diffusion. The first two approximations are that relative vorticity, not potential vorticity, is diffused along isopyncals and that the flow is in approximate geostrophic balance. An additional approximation to the Jacobian term is required when the dissipation coefficient varies in space. More importantly, the critique of this hypothesis results in the conclusion that the viscosity parameter in the momentum equation should be identical to the tradition GM closure parameter {Kappa}. Overall, we deem the viscous form of the eddy closure for potential vorticity as a viable closure for use in ocean circulation models.

  10. Corrosion Detection in Airframes Using a New Flux-Focusing Eddy Current Probe

    NASA Technical Reports Server (NTRS)

    Fulton, James P.; Wincheski, Buzz; Nath, Shridhar; Namkung, Min

    1994-01-01

    panels which may contain air gaps between the layers. Since the probe utilized eddy currents its corrosion detection capabilities are similar to convectional eddy current techniques, but the new probe is much easier to use.

  11. Modelling cyclonic eddies in the Delagoa Bight region

    NASA Astrophysics Data System (ADS)

    Cossa, O.; Pous, S.; Penven, P.; Capet, X.; Reason, C. J. C.

    2016-05-01

    The objective of this study is to document and shed light on the circulation around the Delagoa Bight region in the southern Mozambique Channel using a realistic modelling approach. A simulation including mesoscale forcings at the boundaries of our regional configuration succeeds in reproducing the general circulation in the region as well as the existence of a semi-permanent cyclonic eddy, whose existence is attested by in situ measurements in the Bight. Characterised by a persistent local minimum in SSH located around 26°S-34°E, this cyclonic eddy termed herein the Delagoa Bight lee eddy occurs about 25% of the time with no clear seasonal preference. Poleward moving cyclones, mostly generated further north, occur another 25% of the time in the Bight area. A tracking method applied to eddies generated in Delagoa Bight using model outputs as well as AVISO data confirms the model realism and provides additional statistics. The diameter of the eddy core varies between 61 and 147 km and the average life time exceeds 20 days. Additional model analyses reveal the systematic presence of negative vorticity in the Bight that can organise and form a Delagoa Bight lee eddy depending on the intensity of an intermittent southward flow along the shore and the spatial distribution of surrounding mesoscale features. In addition, the model solution shows other cyclonic eddies generated near Inhambane and eventually travelling through the Bight. Their generation and pathways appears to be linked with large Mozambique Channel rings.

  12. Dynamics of Eddies in the Southeastern Tropical Indian Ocean

    NASA Astrophysics Data System (ADS)

    Hanifah, F.; Ningsih, N. S.; Sofian, I.

    2016-08-01

    A holistic study was done on eddies in the Southeastern Tropical Indian Ocean (SETIO) using the HYbrid Coordinate Ocean Model (HYCOM) for 64 years (from 1950 to 2013). The results from the model were verified against the current and the Sea Surface Height Anomaly (SSHA) from Ocean Surface Current Analyses - Real time (OSCAR) and Archiving, Validation and Interpretation of Satellite Oceanographic Data (AVISO) respectively. The verification showed that the model simulates the condition in the area of study relatively well. We discovered that the local wind was not the only factor that contributed to the formation of eddies in the area. The difference in South Java Current (SJC) flow compared to the Indonesian Throughflow (ITF) and South Equatorial Current (SEC) flow as well as the difference in the relative velocity between the currents in the area led us to suspect that shear velocity may be responsible for the formation of eddies. The results from our model corroborated our prediction about shear velocity. Therefore, we attempted to explain the appearance of eddies in the SETIO based on the concept of shear velocity. By observing and documenting the occurrences of eddies in the area, we found that there are 8 cyclonic and 7 anticyclonic eddies in the SETIO. The distribution and frequency of the appearance of eddies varies, depending on the season.

  13. A novel eddy current damper: theory and experiment

    NASA Astrophysics Data System (ADS)

    Ebrahimi, Babak; Khamesee, Mir Behrad; Golnaraghi, Farid

    2009-04-01

    A novel eddy current damper is developed and its damping characteristics are studied analytically and experimentally. The proposed eddy current damper consists of a conductor as an outer tube, and an array of axially magnetized ring-shaped permanent magnets separated by iron pole pieces as a mover. The relative movement of the magnets and the conductor causes the conductor to undergo motional eddy currents. Since the eddy currents produce a repulsive force that is proportional to the velocity of the conductor, the moving magnet and the conductor behave as a viscous damper. The eddy current generation causes the vibration to dissipate through the Joule heating generated in the conductor part. An accurate, analytical model of the system is obtained by applying electromagnetic theory to estimate the damping properties of the proposed eddy current damper. A prototype eddy current damper is fabricated, and experiments are carried out to verify the accuracy of the theoretical model. The experimental test bed consists of a one-degree-of-freedom vibration isolation system and is used for the frequency and transient time response analysis of the system. The eddy current damper model has a 0.1 m s-2 (4.8%) RMS error in the estimation of the mass acceleration. A damping coefficient as high as 53 Ns m-1 is achievable with the fabricated prototype. This novel eddy current damper is an oil-free, inexpensive damper that is applicable in various vibration isolation systems such as precision machinery, micro-mechanical suspension systems and structure vibration isolation.

  14. Carbon dynamics within cyclonic eddies: insights from a biomarker study.

    PubMed

    Alonso-González, Iván J; Arístegui, Javier; Lee, Cindy; Sanchez-Vidal, Anna; Calafat, Antoni; Fabrés, Joan; Sangrá, Pablo; Mason, Evan

    2013-01-01

    It is generally assumed that episodic nutrient pulses by cyclonic eddies into surface waters support a significant fraction of the primary production in subtropical low-nutrient environments in the northern hemisphere. However, contradictory results related to the influence of eddies on particulate organic carbon (POC) export have been reported. As a step toward understanding the complex mechanisms that control export of material within eddies, we present here results from a sediment trap mooring deployed within the path of cyclonic eddies generated near the Canary Islands over a 1.5-year period. We find that, during summer and autumn (when surface stratification is stronger, eddies are more intense, and a relative enrichment in CaCO3 forming organisms occurs), POC export to the deep ocean was 2-4 times higher than observed for the rest of the year. On the contrary, during winter and spring (when mixing is strongest and the seasonal phytoplankton bloom occurs), no significant enhancement of POC export associated with eddies was observed. Our biomarker results suggest that a large fraction of the material exported from surface waters during the late-winter bloom is either recycled in the mesopelagic zone or bypassed by migrant zooplankton to the deep scattering layer, where it would disaggregate to smaller particles or be excreted as dissolved organic carbon. Cyclonic eddies, however, would enhance carbon export below 1000 m depth during the summer stratification period, when eddies are more intense and frequent, highlighting the important role of eddies and their different biological communities on the regional carbon cycle.

  15. Eddy current measurement system evaluation for corrosion depth determination on cast aluminum aircraft structure

    NASA Astrophysics Data System (ADS)

    Singh, Surendra; Greving, Dan; Kinney, Andy; Vensel, Fred; Ohm, Jim; Peeler, Mike

    2013-01-01

    An eddy current (EC) technique was developed to determine the corrosion depth on a bare flange face of a cast aluminum A356-T6 aircraft engine structure. The EC response and the corrosion depths determined through metallurgical cross sections were used to develop an empirical relation between EC response and depth. The EC technique and depth determination are used to inspect the engine structures during overhaul to determine if they are fit for continued service. An accurate and reliable Non-Destructive Inspection is required to ensure that structures returned to service are safe for continued operation. NDE system reliability demonstrations of the eddy current technique are traditionally reported in terms of Probability of Detection (POD) data using MIL-HDBK-1823A. However, the calculation of POD data is based on a simple linear predictive model that is valid only if certain criteria are met. These are: 1) NDE system response is measurable (i.e. continuous data), 2) Flaw size is known and measurable (i.e. continuous data), 3) relationship between the NDE system response and flaw size is linear (or linear on a log scale), 4) variation in measured responseresponse around a predicted response for a given flaw size is normally distributed, 5) the variation around the predicted response is constant (i.e. variation does not change with flaw size), and 6) inherent variability in the NDE system is known and fully understood. In this work, a Measurement System Evaluation (MSE) of the Eddy Current System was used to address some of these concerns. This work was completed on two aircraft structures having varying corrosion depths. The data were acquired in a random manner at fifty regions of interests (ROIs). Three operators participated in this study, and each operator measured Eddy Current response three times in each ROI. In total, there were four hundred and fifty data points collected. Following this, the two structures were sectioned for measuring corrosion depth. The

  16. Eddy-Current Inspection Of Tab Seals On Beverage Cans

    NASA Technical Reports Server (NTRS)

    Bar-Cohen, Yoseph

    1994-01-01

    Eddy-current inspection system monitors tab seals on beverage cans. Device inspects all cans at usual production rate of 1,500 to 2,000 cans per minute. Automated inspection of all units replaces visual inspection by microscope aided by mass spectrometry. System detects defects in real time. Sealed cans on conveyor pass near one of two coils in differential eddy-current probe. Other coil in differential eddy-current probe positioned near stationary reference can on which tab seal is known to be of acceptable quality. Signal of certain magnitude at output of probe indicates defective can, automatically ejected from conveyor.

  17. Forest Ecosystem respiration estimated from eddy covariance and chamber measurements under high turbulence and substantial tree mortality from bark beetles

    USGS Publications Warehouse

    Speckman, Heather N.; Frank, John M.; Bradford, John B.; Miles, Brianna L.; Massman, William J.; Parton, William J.; Ryan, Michael G.

    2015-01-01

    Eddy covariance nighttime fluxes are uncertain due to potential measurement biases. Many studies report eddy covariance nighttime flux lower than flux from extrapolated chamber measurements, despite corrections for low turbulence. We compared eddy covariance and chamber estimates of ecosystem respiration at the GLEES Ameriflux site over seven growing seasons under high turbulence (summer night mean friction velocity (u*) = 0.7 m s−1), during which bark beetles killed or infested 85% of the aboveground respiring biomass. Chamber-based estimates of ecosystem respiration during the growth season, developed from foliage, wood and soil CO2 efflux measurements, declined 35% after 85% of the forest basal area had been killed or impaired by bark beetles (from 7.1 ±0.22 μmol m−2 s−1 in 2005 to 4.6 ±0.16 μmol m−2 s−1 in 2011). Soil efflux remained at ~3.3 μmol m−2 s−1 throughout the mortality, while the loss of live wood and foliage and their respiration drove the decline of the chamber estimate. Eddy covariance estimates of fluxes at night remained constant over the same period, ~3.0 μmol m−2 s−1 for both 2005 (intact forest) and 2011 (85% basal area killed or impaired). Eddy covariance fluxes were lower than chamber estimates of ecosystem respiration (60% lower in 2005, and 32% in 2011), but the mean night estimates from the two techniques were correlated within a year (r2 from 0.18-0.60). The difference between the two techniques was not the result of inadequate turbulence, because the results were robust to a u* filter of > 0.7 m s−1. The decline in the average seasonal difference between the two techniques was strongly correlated with overstory leaf area (r2=0.92). The discrepancy between methods of respiration estimation should be resolved to have confidence in ecosystem carbon flux estimates.

  18. Forest ecosystem respiration estimated from eddy covariance and chamber measurements under high turbulence and substantial tree mortality from bark beetles.

    PubMed

    Speckman, Heather N; Frank, John M; Bradford, John B; Miles, Brianna L; Massman, William J; Parton, William J; Ryan, Michael G

    2015-02-01

    Eddy covariance nighttime fluxes are uncertain due to potential measurement biases. Many studies report eddy covariance nighttime flux lower than flux from extrapolated chamber measurements, despite corrections for low turbulence. We compared eddy covariance and chamber estimates of ecosystem respiration at the GLEES Ameriflux site over seven growing seasons under high turbulence [summer night mean friction velocity (u*) = 0.7 m s(-1)], during which bark beetles killed or infested 85% of the aboveground respiring biomass. Chamber-based estimates of ecosystem respiration during the growth season, developed from foliage, wood, and soil CO2 efflux measurements, declined 35% after 85% of the forest basal area had been killed or impaired by bark beetles (from 7.1 ± 0.22 μmol m(-2) s(-1) in 2005 to 4.6 ± 0.16 μmol m(-2) s(-1) in 2011). Soil efflux remained at ~3.3 μmol m(-2) s(-1) throughout the mortality, while the loss of live wood and foliage and their respiration drove the decline of the chamber estimate. Eddy covariance estimates of fluxes at night remained constant over the same period, ~3.0 μmol m(-2) s(-1) for both 2005 (intact forest) and 2011 (85% basal area killed or impaired). Eddy covariance fluxes were lower than chamber estimates of ecosystem respiration (60% lower in 2005, and 32% in 2011), but the mean night estimates from the two techniques were correlated within a year (r(2) from 0.18 to 0.60). The difference between the two techniques was not the result of inadequate turbulence, because the results were robust to a u* filter of >0.7 m s(-1). The decline in the average seasonal difference between the two techniques was strongly correlated with overstory leaf area (r(2) = 0.92). The discrepancy between methods of respiration estimation should be resolved to have confidence in ecosystem carbon flux estimates.

  19. Conductivity Profile Determination by Eddy Current for Shot Peened Superalloy Surfaces Toward Residual Stress Assessment

    SciTech Connect

    Shen, Y.; Lo, C. C. H.; Frishman, A. M.; Lee, C.; Nakagawa, N.

    2007-03-21

    This paper describes an eddy current model-based method for inverting near-surface conductivity deviation profiles of surface treated materials from swept-high frequency eddy current (SHFEC) data. This work forms part of our current research directed towards the development of an electromagnetic nondestructive technique for assessing residual stress of shot-peened superalloy components. The inversion procedure is based on the use of a parameterized function to describe the near-surface conductivity as a function of depth for a shot-peened surface, and the laterally uniform multi-layer theory of Cheng, Dodd and Deeds to calculate the resulting coil impedance deviations. The convergence of the inversion procedure has been tested against synthesized eddy current data. As a demonstration, the conductivity deviation profiles of a series of Inconel 718 specimens, shot peened at various Almen intensities, have been obtained by inversion. Several consistency tests were conducted to examine the reliability of the inverted conductivity profiles. The results show that conductivity deviation profiles can be reliably determined from SHFEC data within the accuracy of the current measurement system.

  20. Ecological implications of eddy retention in the open ocean: a Lagrangian approach

    NASA Astrophysics Data System (ADS)

    d'Ovidio, Francesco; De Monte, Silvia; Della Penna, Alice; Cotté, Cedric; Guinet, Christophe

    2013-06-01

    The repartition of tracers in the ocean’s upper layer on the scale of a few tens of kilometres is largely determined by the horizontal transport induced by surface currents. Here we consider surface currents detected from satellite altimetry (Jason and Envisat missions) and we study how surface waters may be trapped by mesoscale eddies through a semi-Lagrangian diagnostic which combines the Lyapunov approach with Eulerian techniques. Such a diagnostic identifies the regions of the ocean’s upper layer with different retention times that appear to influence the behaviour of a tagged marine predator (an elephant seal) along a foraging trip. The comparison between predator trajectory and eddy retention time suggests that water trapping by mesoscale eddies, derived from satellite altimetry, may be an important factor for monitoring hotspots of trophic interactions in the open ocean. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Lyapunov analysis: from dynamical systems theory to applications’.

  1. REMOTE FIELD EDDY CURRENT INSPECTION OF UNPIGGABLE PIPELINES

    SciTech Connect

    Albert Teitsma

    2004-03-01

    The Remote Field Eddy Current (RFEC) technique is ideal for inspecting unpiggable pipelines because all its components can be made much smaller than the diameter of the pipe to be inspected. We reviewed the technique, and used demonstrations from prior work by others in presentations on the technique and how we plan to develop it. Coils were wound; a jig for pulling the coils through the pipe was manufactured; defects were machined in one six-inch diameter, ten-foot long pipe; and the equipment was assembled. After completing first crude pullout test to show that RFEC inspection would work, we repeated the experiment with a proper jig and got excellent results. The test showed the expected behavior, with the direct field dominating the signal to about two pipe diameters from the drive coil, and the remote field dominating for greater separations between the drive coil and the sensing coils. Response of RFEC to a typical defect was measured, as was the sensitivity to defect size. Before manufacturing defects in the pipe, we measured the effect of defect separation and concluded that defects separated by 18 inches or 1/3rd of the pipe diameter did not interfere with each other. We manufactured a set of 13 defects, and measured the RFEC signals. We found a background variation that was eventually attributed to permeability variations in the seamless pipe. We scanned all thirteen defects and got satisfactory results. The two smallest defects did not show a signal, but these were much too small to be reported in a pipeline inspection. We acquired a ten-foot seam welded pipe that has much less background variation. We are measuring the sensitivity of RFEC signals to mechanical variations between the exciter and sensing coils.

  2. Nesting large-eddy simulations within mesoscale simulations for wind energy applications

    SciTech Connect

    Lundquist, J K; Mirocha, J D; Chow, F K; Kosovic, B; Lundquist, K A

    2008-09-08

    With increasing demand for more accurate atmospheric simulations for wind turbine micrositing, for operational wind power forecasting, and for more reliable turbine design, simulations of atmospheric flow with resolution of tens of meters or higher are required. These time-dependent large-eddy simulations (LES), which resolve individual atmospheric eddies on length scales smaller than turbine blades and account for complex terrain, are possible with a range of commercial and open-source software, including the Weather Research and Forecasting (WRF) model. In addition to 'local' sources of turbulence within an LES domain, changing weather conditions outside the domain can also affect flow, suggesting that a mesoscale model provide boundary conditions to the large-eddy simulations. Nesting a large-eddy simulation within a mesoscale model requires nuanced representations of turbulence. Our group has improved the Weather and Research Forecasting model's (WRF) LES capability by implementing the Nonlinear Backscatter and Anisotropy (NBA) subfilter stress model following Kosovic (1997) and an explicit filtering and reconstruction technique to compute the Resolvable Subfilter-Scale (RSFS) stresses (following Chow et al, 2005). We have also implemented an immersed boundary method (IBM) in WRF to accommodate complex terrain. These new models improve WRF's LES capabilities over complex terrain and in stable atmospheric conditions. We demonstrate approaches to nesting LES within a mesoscale simulation for farms of wind turbines in hilly regions. Results are sensitive to the nesting method, indicating that care must be taken to provide appropriate boundary conditions, and to allow adequate spin-up of turbulence in the LES domain.

  3. Oxygen utilization and downward carbon flux in an oxygen-depleted eddy in the eastern tropical North Atlantic

    NASA Astrophysics Data System (ADS)

    Fiedler, Björn; Grundle, Damian S.; Schütte, Florian; Karstensen, Johannes; Löscher, Carolin R.; Hauss, Helena; Wagner, Hannes; Loginova, Alexandra; Kiko, Rainer; Silva, Péricles; Tanhua, Toste; Körtzinger, Arne

    2016-10-01

    The occurrence of mesoscale eddies that develop suboxic environments at shallow depth (about 40-100 m) has recently been reported for the eastern tropical North Atlantic (ETNA). Their hydrographic structure suggests that the water mass inside the eddy is well isolated from ambient waters supporting the development of severe near-surface oxygen deficits. So far, hydrographic and biogeochemical characterization of these eddies was limited to a few autonomous surveys, with the use of moorings, underwater gliders and profiling floats. In this study we present results from the first dedicated biogeochemical survey of one of these eddies conducted in March 2014 near the Cape Verde Ocean Observatory (CVOO). During the survey the eddy core showed oxygen concentrations as low as 5 µmol kg-1 with a pH of around 7.6 at approximately 100 m depth. Correspondingly, the aragonite saturation level dropped to 1 at the same depth, thereby creating unfavorable conditions for calcifying organisms. To our knowledge, such enhanced acidity within near-surface waters has never been reported before for the open Atlantic Ocean. Vertical distributions of particulate organic matter and dissolved organic matter (POM and DOM), generally showed elevated concentrations in the surface mixed layer (0-70 m), with DOM also accumulating beneath the oxygen minimum. With the use of reference data from the upwelling region where these eddies are formed, the oxygen utilization rate was calculated by determining oxygen consumption through the remineralization of organic matter. Inside the core, we found these rates were almost 1 order of magnitude higher (apparent oxygen utilization rate (aOUR); 0.26 µmol kg-1 day-1) than typical values for the open North Atlantic. Computed downward fluxes for particulate organic carbon (POC), were around 0.19 to 0.23 g C m-2 day-1 at 100 m depth, clearly exceeding fluxes typical for an oligotrophic open-ocean setting. The observations support the view that the oxygen

  4. Large-eddy simulations of a fully appended submarine model

    NASA Astrophysics Data System (ADS)

    Posa, Antonio; Balaras, Elias

    2013-11-01

    In the present study we report large-eddy simulations (LES) the flow around an idealized submarine geometry (DARPA SUBOFF) at a Reynolds number -based on the model length and free stream velocity- equal to 1.2 million. A finite-difference formulation on a cylindrical coordinate grid of 2.8 billion nodes is utilized, and boundary conditions on the submarine model are imposed using an immersed-boundary technique. The boundary layers are ``tripped'' near the leading edge to mimic the conditions in experiments reported in the literature. Our computations resolve the detailed dynamics of the turbulent boundary layers on the suboff body as well as their interaction with the large scale vortices generated at the sail and fin junctions. The time-averaged velocity profiles in the intermediate wake reach self-similarity, except for the region affected by the wake of the sail. The comparison with the exponential law from the experimental study in the literature is satisfactory. It is also confirmed that the flow coming from the fins causes a deviation from the self-similar profile, which is more evident than in the experiments. Details on the turbulent boundary layer on the surface of the body will be provided, showing a good qualitative agreement with the results in the literature. Supported by ONR Grant N000141110455, monitored by Dr. Ki-Han Kim.

  5. Eddy Current Inspection of Components with Complex Geometries

    NASA Astrophysics Data System (ADS)

    Plotnikov, Yuri; Wang, Changting; McKnight, William; Suh, Ui

    2008-02-01

    Eddy current (EC) technique is a common inspection method for the detection of open surface cracks and subsurface anomalies. While manual EC inspection is quite reliable on parts with flat (or large curvature) surfaces and parts with consistent subsurface geometry, EC inspection of parts having more complicated surface and subsurface profiles has to rely on automated scan/data collection and post-processing. Examples of the structures with complex geometries are aircraft engine rotating parts and multi-layer aircraft structures (lap joints). Data collection for such structures, in most cases, can be performed by using multiple scans of a single sensor EC probe with multi-frequency excitation. To improve productivity of the inspection, arrays of EC sensors are applied during inspection for surface flaws. In this work, the flexible ECAP (EC array probe) with sensitivity to the cracks of variable orientations is presented. To resolve the complex subsurface geometry of the aircraft skin, pulsed excitation is employed. This makes for a faster data collection and full post-processing capabilities. Conversion to multi-frequency (multi-layer) image analysis is done after data collection is completed. The subsurface flaws present in a particular layer of a riveted lap joint become evident from several EC images, which cannot be accomplished by manual inspection.

  6. Eddy Permitting Simulations of Biogeochemical Cycles in the Global Ocean

    NASA Astrophysics Data System (ADS)

    Sumata, H.; Hashioka, T.; Suzuki, T.; Yamanaka, Y.

    2008-12-01

    A 3D ecosystem-biogeochemical model simulation for the global domain is performed in order to investigate variability of oceanic ecosystem on time scales of years to decades. The model has a horizontal resolution of 1/4 times 1/6 degrees and 51 vertical levels, covering the entire domain of the world ocean. The ecosystem- biogeochemical part of the model is based on NEMURO (North Pacific Ecosystem Model Used for Regional Oceanography), and is coupled with CCSR Ocean Component Model (COCO) version 4.3 by an offline technique. The physical part of the model is driven by the inter-annual forcing by common ocean-ice reference experiments (CORE) data from 1958 to 2004, and reasonably simulates inter-annual to decadal variabilities of ocean conditions related to biogeochemical cycles. These properties of the physical model with its eddying filed enable us to reproduce the realistic distributions of nutrients and plankton productions. Comparisons with historical station data show that the model also reasonably simulates the observed variabilities of ecosystem on time scales of years to decades. In particular, the model captures the transitions of biogeochemical cycles associated with regime shifts.

  7. Large eddy simulation for aerodynamics: status and perspectives.

    PubMed

    Sagaut, Pierre; Deck, Sébastien

    2009-07-28

    The present paper provides an up-to-date survey of the use of large eddy simulation (LES) and sequels for engineering applications related to aerodynamics. Most recent landmark achievements are presented. Two categories of problem may be distinguished whether the location of separation is triggered by the geometry or not. In the first case, LES can be considered as a mature technique and recent hybrid Reynolds-averaged Navier-Stokes (RANS)-LES methods do not allow for a significant increase in terms of geometrical complexity and/or Reynolds number with respect to classical LES. When attached boundary layers have a significant impact on the global flow dynamics, the use of hybrid RANS-LES remains the principal strategy to reduce computational cost compared to LES. Another striking observation is that the level of validation is most of the time restricted to time-averaged global quantities, a detailed analysis of the flow unsteadiness being missing. Therefore, a clear need for detailed validation in the near future is identified. To this end, new issues, such as uncertainty and error quantification and modelling, will be of major importance. First results dealing with uncertainty modelling in unsteady turbulent flow simulation are presented.

  8. Ergodicity test of the eddy correlation method

    NASA Astrophysics Data System (ADS)

    Chen, J.; Hu, Y.; Yu, Y.; Lü, S.

    2014-07-01

    The turbulent flux observation in the near-surface layer is a scientific issue which researchers in the fields of atmospheric science, ecology, geography science, etc. are commonly interested in. For eddy correlation measurement in the atmospheric surface layer, the ergodicity of turbulence is a basic assumption of the Monin-Obukhov (M-O) similarity theory, which is confined to steady turbulent flow and homogenous surface; this conflicts with turbulent flow under the conditions of complex terrain and unsteady, long observational period, which the study of modern turbulent flux tends to focus on. In this paper, two sets of data from the Nagqu Station of Plateau Climate and Environment (NaPlaCE) and the cooperative atmosphere-surface exchange study 1999 (CASE99) were used to analyze and verify the ergodicity of turbulence measured by the eddy covariance system. Through verification by observational data, the vortex of atmospheric turbulence, which is smaller than the scale of the atmospheric boundary layer (i.e., its spatial scale is less than 1000 m and temporal scale is shorter than 10 min) can effectively meet the conditions of the average ergodic theorem, and belong to a wide sense stationary random processes. Meanwhile, the vortex, of which the spatial scale is larger than the scale of the boundary layer, cannot meet the conditions of the average ergodic theorem, and thus it involves non-ergodic stationary random processes. Therefore, if the finite time average is used to substitute for the ensemble average to calculate the average random variable of the atmospheric turbulence, then the stationary random process of the vortex, of which spatial scale was less than 1000 m and thus below the scale of the boundary layer, was possibly captured. However, the non-ergodic random process of the vortex, of which the spatial scale was larger than that of the boundary layer, could not be completely captured. Consequently, when the finite time average was used to substitute

  9. Development of a Turbulence-Resolving, Three-dimensional, Free Water Surface Numerical Model for Recirculation Eddies in Grand Canyon

    NASA Astrophysics Data System (ADS)

    Akahori, R.; Schmeeckle, M. W.

    2005-12-01

    In the Colorado River in Grand Canyon, sand bars, which are built in recirculation areas downstream of channel expansions are valuable resources, particularly as natural habitat for endangered native fish and recreation sites for recreation. Since the closure of Glen Canyon Dam in 1963, there has been a reduction in the size of recirculation eddy bars. Simulated floods in the Colorado after tributary flood sediment input from the Paria River are being investigated as a method of rebuilding recirculation eddy beaches. Time-averaged, two-dimensional (and quasi- three-dimensional) numerical models have been employed to predict deposition during these beach/habit-building test flows. However, behind channel expansion areas, flows are strongly three-dimensional and the cross-channel flow is driven primarily by upwelling boils along the eddy fence that are neither stationary in time or space. Furthermore, these strong vertical motions along the eddy fence preclude use of the hydrostatic assumption. In this study, a non-hydrostatic three-dimensional numerical model is presented in order to calculate flow velocity in channels having rapid channel expansions. This model employs the Large Eddy Simulation (LES) turbulence modeling technique. LES uses spatial filtering to separate flows into gird scale and sub-gird scale rather than time averaging, thus it directly calculates large-scale turbulent motions. Also, this model employs a moving grid system and the Body Fitted Coordinate (BFC) system. These grid and coordinate systems allow the model to calculate time-dependent free water surface levels induced by large-scale turbulent motions. The model_fs calculation results are compared to existing experimental results of an open channel flow expansion in a laboratory flume. The comparison shows that the model succeeds to reproduce several key features of the flow, such as the temporally- and vertically-averaged horizontal recirculation eddy structure, and the time-averaged cross

  10. Eddy covariance measurements of net C exchange in the CAM bioenergy crop, Agave tequiliana

    NASA Astrophysics Data System (ADS)

    Owen, Nick A.; Choncubhair, Órlaith Ní; Males, Jamie; del Real Laborde, José Ignacio; Rubio-Cortés, Ramón; Griffiths, Howard; Lanigan, Gary

    2016-04-01

    Bioenergy crop cultivation may focus more on low grade and marginal lands in order to avoid competition with food production for land and water resources. However, in many regions, this would require improvements in plant water-use efficiency that are beyond the physiological capacity of most C3 and C4 bioenergy crop candidates. Crassulacean acid metabolism (CAM) plants, such as Agave tequiliana, can combine high above-ground productivity with as little as 20% of the water demand of C3 and C4 crops. This is achieved through temporal separation of carboxylase activities, with stomata opening at night to allow gas exchange and minimise transpirational losses. Previous studies have employed 'bottom-up' methodologies to investigate carbon (C) accumulation and productivity in Agave, by scaling leaf-level gas exchange and titratable acidity (TA) with leaf area index or maximum productivity. We used the eddy covariance (EC) technique to quantify ecosystem-scale gas exchange over an Agave plantation in Mexico ('top-down' approach). Measurements were made over 252 days, including the transition from wet to dry periods. Results were cross-validated against diel changes in titratable acidity, leaf-unfurling rates, energy exchange fluxes and reported biomass yields. Net ecosystem exchange of CO2 displayed a CAM rhythm that alternated from a net C sink at night to a net C source during the day and partitioned canopy fluxes (gross C assimilation, FA,EC) showed a characteristic four-phase CO2 exchange pattern. The projected ecosystem C balance indicated that the site was a net sink of -333 ± 24 g C m-2 y-1, comprising cumulative soil respiration of 692 ± 7 g C m-2 y-1 and FA,EC of -1025 ± 25 g C m-2 y-1. EC-estimated biomass yield was 20.1 Mg ha-1 y-1. Average integrated daily FA,EC was -234 ± 5 mmol CO2 m-2 d-1 and persisted almost unchanged after 70 days of drought conditions. Our results suggest that the carbon acquisition strategy of drought avoidance employed by Agave

  11. Eddy covariance measurements of net C exchange in the CAM bioenergy crop, Agave tequiliana

    NASA Astrophysics Data System (ADS)

    Owen, Nick A.; Choncubhair, Órlaith Ní; Males, Jamie; del Real Laborde, José Ignacio; Rubio-Cortés, Ramón; Griffiths, Howard; Lanigan, Gary

    2016-04-01

    Bioenergy crop cultivation may focus more on low grade and marginal lands in order to avoid competition with food production for land and water resources. However, in many regions, this would require improvements in plant water-use efficiency that are beyond the physiological capacity of most C3 and C4 bioenergy crop candidates. Crassulacean acid metabolism (CAM) plants, such as Agave tequiliana, can combine high above-ground productivity with as little as 20% of the water demand of C3 and C4 crops. This is achieved through temporal separation of carboxylase activities, with stomata opening at night to allow gas exchange and minimise transpirational losses. Previous studies have employed 'bottom-up' methodologies to investigate carbon (C) accumulation and productivity in Agave, by scaling leaf-level gas exchange and titratable acidity (TA) with leaf area index or maximum productivity. We used the eddy covariance (EC) technique to quantify ecosystem-scale gas exchange over an Agave plantation in Mexico ('top-down' approach). Measurements were made over 252 days, including the transition from wet to dry periods. Results were cross-validated against diel changes in titratable acidity, leaf-unfurling rates, energy exchange fluxes and reported biomass yields. Net ecosystem exchange of CO2 displayed a CAM rhythm that alternated from a net C sink at night to a net C source during the day and partitioned canopy fluxes (gross C assimilation, FA,EC) showed a characteristic four-phase CO2 exchange pattern. The projected ecosystem C balance indicated that the site was a net sink of -333 ± 24 g C m‑2 y‑1, comprising cumulative soil respiration of 692 ± 7 g C m‑2 y‑1 and FA,EC of -1025 ± 25 g C m‑2 y‑1. EC-estimated biomass yield was 20.1 Mg ha‑1 y‑1. Average integrated daily FA,EC was -234 ± 5 mmol CO2 m‑2 d‑1 and persisted almost unchanged after 70 days of drought conditions. Our results suggest that the carbon acquisition strategy of drought avoidance

  12. Electronic flaw simulator for eddy current probe calibration

    NASA Technical Reports Server (NTRS)

    Almasy, L. J.; Cowfer, C. D.

    1970-01-01

    Electronic flaw simulator cycled into the eddy current system eliminates errors in probe calibration. A discrimination level reference established in the probe permits recognition of those flaws in materials with an equivalent volume equal to or greater than the reference.

  13. Foam-machining tool with eddy-current transducer

    NASA Technical Reports Server (NTRS)

    Copper, W. P.

    1975-01-01

    Three-cutter machining system for foam-covered tanks incorporates eddy-current sensor. Sensor feeds signal to numerical controller which programs rotational and vertical axes of sensor travel, enabling cutterhead to profile around tank protrusions.

  14. Eddy-Current Probes For Inspecting Graphite-Fiber Composites

    NASA Technical Reports Server (NTRS)

    Workman, Gary L.; Wang, Morgan

    1992-01-01

    Eddy-current probes with E-shaped and U-shaped magnetic cores developed to detect flaws in graphite-fiber/epoxy and other composites. Magnetic fields more concentrated, yielding better coupling with specimens.

  15. Eddy sensors for small diameter stainless steel tubes.

    SciTech Connect

    Skinner, Jack L.; Morales, Alfredo Martin; Grant, J. Brian; Korellis, Henry James; LaFord, Marianne Elizabeth; Van Blarigan, Benjamin; Andersen, Lisa E.

    2011-08-01

    The goal of this project was to develop non-destructive, minimally disruptive eddy sensors to inspect small diameter stainless steel metal tubes. Modifications to Sandia's Emphasis/EIGER code allowed for the modeling of eddy current bobbin sensors near or around 1/8-inch outer diameter stainless steel tubing. Modeling results indicated that an eddy sensor based on a single axial coil could effectively detect changes in the inner diameter of a stainless steel tubing. Based on the modeling results, sensor coils capable of detecting small changes in the inner diameter of a stainless steel tube were designed, built and tested. The observed sensor response agreed with the results of the modeling and with eddy sensor theory. A separate limited distribution SAND report is being issued demonstrating the application of this sensor.

  16. Simulation of frontal eddies on the East Florida Shelf

    NASA Astrophysics Data System (ADS)

    Fiechter, Jerome; Mooers, Christopher N. K.

    2003-11-01

    Frontal eddies are typical features on the cyclonic side of the Florida Current (FC) along the East Florida Shelf (EFS), producing characteristic ``shingle'' patterns in sea surface temperature. Intensive observations and idealized numerical analyses have described such eddies over the past three decades. Here, simulations from a high-resolution (2 to 10 km), curvilinear coastal ocean circulation model demonstrate their structure and evolution with realistic bottom topography and FC over an extended domain including the Straits of Florida and the entire EFS. Simulations agree with observations in estimating translation speed, recurrence period, strength, characteristic length-scales, and overall circulation patterns. In addition, the simulations demonstrate the interactions between the frontal eddies and the meander crests and bottom topography as they translate along the EFS. Overall, a first level of model validation has been established that will facilitate consideration of the forecast problem for frontal eddies associated with the FC on the EFS.

  17. Field experiences with multifrequency-multiparameter eddy-current technology

    NASA Astrophysics Data System (ADS)

    Brown, S.

    1982-03-01

    A multifrequency/multiparameter eddy current system was assembled for the inservice inspection of pressurized water reactor steam generator tubing. Five steam generators were inspected for a total data base of approximately 11,000 tubes. Based on a comparison with conventional single frequency inspection methods, multifrequency/multiparameter eddy current technology offers significant improvements. Multifrequency eddy current, with its multiple frequency coil excitation, can offer benefits in reducing in containment data acquisition time by the performance of parallel tube tests; in addition the resulting broad spectrum data base is useful for the analysis of complex or nonunique signals which can arise during a steam generator inspection. Multiparameter eddy current offers an approach for the real time suppression of extraneous variables such as support plates/tube sheet, ID noise and denting. With appropriate mixing/basis frequency combinations, tube degradation in the presence of the extraneous variables can be more reliably detected and characterized.

  18. Large eddy simulations of laminar separation bubble

    NASA Astrophysics Data System (ADS)

    Cadieux, Francois

    The flow over blades and airfoils at moderate angles of attack and Reynolds numbers ranging from ten thousand to a few hundred thousands undergoes separation due to the adverse pressure gradient generated by surface curvature. In many cases, the separated shear layer then transitions to turbulence and reattaches, closing off a recirculation region -- the laminar separation bubble. To avoid body-fitted mesh generation problems and numerical issues, an equivalent problem for flow over a flat plate is formulated by imposing boundary conditions that lead to a pressure distribution and Reynolds number that are similar to those on airfoils. Spalart & Strelet (2000) tested a number of Reynolds-averaged Navier-Stokes (RANS) turbulence models for a laminar separation bubble flow over a flat plate. Although results with the Spalart-Allmaras turbulence model were encouraging, none of the turbulence models tested reliably recovered time-averaged direct numerical simulation (DNS) results. The purpose of this work is to assess whether large eddy simulation (LES) can more accurately and reliably recover DNS results using drastically reduced resolution -- on the order of 1% of DNS resolution which is commonly achievable for LES of turbulent channel flows. LES of a laminar separation bubble flow over a flat plate are performed using a compressible sixth-order finite-difference code and two incompressible pseudo-spectral Navier-Stokes solvers at resolutions corresponding to approximately 3% and 1% of the chosen DNS benchmark by Spalart & Strelet (2000). The finite-difference solver is found to be dissipative due to the use of a stability-enhancing filter. Its numerical dissipation is quantified and found to be comparable to the average eddy viscosity of the dynamic Smagorinsky model, making it difficult to separate the effects of filtering versus those of explicit subgrid-scale modeling. The negligible numerical dissipation of the pseudo-spectral solvers allows an unambiguous

  19. Transient-spatial pattern mining of eddy current pulsed thermography using wavelet transform

    NASA Astrophysics Data System (ADS)

    Yang, Hailong; Gao, Bin; Tian, Guiyun; Ren, Wenwei; Woo, Wai Lok

    2014-07-01

    Eddy current pulsed thermography(ECPT) is an emerging Non-destructive testing and evaluation(NDT & E) technique, which uses hybrid eddy current and thermography NDT & E techniques that enhances the detectability from their compensation. Currently, this technique is limited by the manual selection of proper contrast frames and the issue of improving the efficiency of defect detection of complex structure samples remains a challenge. In order to select a specific frame from transient thermal image sequences to maximize the contrast of thermal variation and defect pattern from complex structure samples, an energy driven approach to compute the coefficient energy of wavelet transform is proposed which has the potential of automatically selecting both optimal transient frame and spatial scale for defect detection using ECPT. According to analysis of the variation of different frequency component and the comparison study of the detection performance of different scale and wavelets, the frame at the end of heating phase is automatically selected as an optimal transient frame for defect detection. In addition, the detection capabilities of the complex structure samples can be enhanced through proper spatial scale and wavelet selection. The proposed method has successfully been applied to low speed impact damage detection of carbon fibre reinforced polymer(CFRP) composite as well as providing the guidance to improve the detectability of ECPT technique.

  20. Mesoscale Eddy Parameterization in an Idealized Primitive Equations Model

    NASA Astrophysics Data System (ADS)

    Anstey, J.; Zanna, L.

    2014-12-01

    Large-scale ocean currents such as the Gulf Stream and Kuroshio Extension are strongly influenced by mesoscale eddies, which have spatial scales of order 10-100 km. The effects of these eddies are poorly represented in many state-of-the-art ocean general circulation models (GCMs) due to the inadequate spatial resolution of these models. In this study we examine the response of the large-scale ocean circulation to the rectified effects of eddy forcing - i.e., the role played by surface-intensified mesoscale eddies in sustaining and modulating an eastward jet that separates from an intense western boundary current (WBC). For this purpose a primitive equations ocean model (the MITgcm) in an idealized wind-forced double-gyre configuration is integrated at eddy-resolving resolution to reach a forced-dissipative equilibrium state that captures the essential dynamics of WBC-extension jets. The rectified eddy forcing is diagnosed as a stochastic function of the large-scale state, this being characterized by the manner in which potential vorticity (PV) contours become deformed. Specifically, a stochastic function based on the Laplacian of the material rate of change of PV is examined in order to compare the primitive equations results with those of a quasi-geostrophic model in which this function has shown some utility as a parameterization of eddy effects (Porta Mana and Zanna, 2014). The key question is whether an eddy parameterization based on quasi-geostrophic scaling is able to carry over to a system in which this scaling is not imposed (i.e. the primitive equations), in which unbalanced motions occur.

  1. Eddy-Current Measurement Of Turning Or Curvature

    NASA Technical Reports Server (NTRS)

    Chern, Engmin J.

    1993-01-01

    Rotatable conductive plate covers sensing coil to varying degree. Curvature of pipe at remote or otherwise inaccessible location inside pipe measured using relatively simple angular-displacement eddy-current probe. Crawler and sensor assemblies move along inside of pipe on wheels. Conductive plate pivots to follow curvature of pipe, partly covering one of eddy-current coils to degree depending on local curvature on pipe.

  2. Formation and Development of Transient Eddies within an MJO

    NASA Astrophysics Data System (ADS)

    Yasunaga, K.

    2012-12-01

    Temporal variations in tropical convection occur on various scales ranging from hours to seasons and beyond. The Madden-Julian oscillation (MJO; Madden and Julian 1971, 1972) is one of the most prominent phenomena regulating the tropical convection. Now, many features of the MJO are well described. However, several fundamental issues still remain unexplained. For example, scale-interaction between the MJO and non-MJO perturbations is one of the main issues on the MJO. The present paper, therefore, explores whether perturbations within an MJO have dominant time and horizontal scales or not. A field observational campaign called CINDY/DYNAMO was conducted over the central equatorial Indian Ocean in October-December 2011. During the campaign, large-scale-organized convection associated with an MJO broke out, and formation and development of transient eddies were prominent during the MJO active phase over the Indian Ocean. Eddies have a zonal scale of 2000-3000 km and time scale of 8-10 days. Following the shift of the convective active area associated with an MJO, the eddy packet moves to the east, although each eddy slowly propagates to the west. In order to examine the robustness, we also conducted the wavelet-analysis of multi-year reanalysis datasets (JCDAS), and it is turned out that the eddy formation and development are significant features of an MJO. Moreover, results from the composite analysis suggest that the eddy plays an significant role in the advection of the dry-air behind an MJO.

  3. Large eddy simulation of trailing edge noise

    NASA Astrophysics Data System (ADS)

    Keller, Jacob; Nitzkorski, Zane; Mahesh, Krishnan

    2015-11-01

    Noise generation is an important engineering constraint to many marine vehicles. A significant portion of the noise comes from propellers and rotors, specifically due to flow interactions at the trailing edge. Large eddy simulation is used to investigate the noise produced by a turbulent 45 degree beveled trailing edge and a NACA 0012 airfoil. A porous surface Ffowcs-Williams and Hawkings acoustic analogy is combined with a dynamic endcapping method to compute the sound. This methodology allows for the impact of incident flow noise versus the total noise to be assessed. LES results for the 45 degree beveled trailing edge are compared to experiment at M = 0 . 1 and Rec = 1 . 9 e 6 . The effect of boundary layer thickness on sound production is investigated by computing using both the experimental boundary layer thickness and a thinner boundary layer. Direct numerical simulation results of the NACA 0012 are compared to available data at M = 0 . 4 and Rec = 5 . 0 e 4 for both the hydrodynamic field and the acoustic field. Sound intensities and directivities are investigated and compared. Finally, some of the physical mechanisms of far-field noise generation, common to the two configurations, are discussed. Supported by Office of Naval research.

  4. Elemental sulfur in Eddy County, New Mexico

    USGS Publications Warehouse

    Hinds, Jim S.; Cunningham, Richard R.

    1970-01-01

    Sulfur has been reported in Eddy County, N. Mex., in rocks ranging from Silurian to Holocene in age at depths of 0-15,020 feet. Targets of present exploration are Permian formations in the Delaware Basin and northwest shelf areas at depths of less than 4,000 feet. Most of the reported sulfur occurrences in the shelf area are in the 'Abo' (as used by some subsurface geologists), Yeso, and San Andres Formations and the Artesia Group. Sulfur deposition in the dense dolomites of the 'Abo,' Yeso, and San Andres Formations is attributed to the reduction of ionic sulfate by hydrogen sulfide in formation waters in zones of preexisting porosity and permeability. A similar origin accounts for most of the sulfur deposits in the formations of the Artesia Group, but some of the sulfur in these formations may have originated in place through the alteration of anhydrite to carbonate and sulfur by the metabolic processes of bacteria in the presence of hydrocarbons. Exploration in the Delaware Basin area is directed primarily toward the Castile Formation. Sulfur deposits in the Castile Formation are found in irregular masses of cavernous brecciated secondary carbonate rock enveloped by impermeable anhydrite. The carbonate masses, or 'castiles,' probably originated as collapse features resulting from subsurface solution and upward stopping. Formation of carbonate rock and sulfur in the castiles is attributed to the reduction of brecciated anhydrite by bacteria and hydrocarbons in the same process ascribed to the formation of carbonate and sulfur in the caprocks of salt domes.

  5. Large eddy simulation of turbulent cavitating flows

    NASA Astrophysics Data System (ADS)

    Gnanaskandan, A.; Mahesh, K.

    2015-12-01

    Large Eddy Simulation is employed to study two turbulent cavitating flows: over a cylinder and a wedge. A homogeneous mixture model is used to treat the mixture of water and water vapor as a compressible fluid. The governing equations are solved using a novel predictor- corrector method. The subgrid terms are modeled using the Dynamic Smagorinsky model. Cavitating flow over a cylinder at Reynolds number (Re) = 3900 and cavitation number (σ) = 1.0 is simulated and the wake characteristics are compared to the single phase results at the same Reynolds number. It is observed that cavitation suppresses turbulence in the near wake and delays three dimensional breakdown of the vortices. Next, cavitating flow over a wedge at Re = 200, 000 and σ = 2.0 is presented. The mean void fraction profiles obtained are compared to experiment and good agreement is obtained. Cavity auto-oscillation is observed, where the sheet cavity breaks up into a cloud cavity periodically. The results suggest LES as an attractive approach for predicting turbulent cavitating flows.

  6. Advanced Eddy current NDE steam generator tubing.

    SciTech Connect

    Bakhtiari, S.

    1999-03-29

    As part of a multifaceted project on steam generator integrity funded by the U.S. Nuclear Regulatory Commission, Argonne National Laboratory is carrying out research on the reliability of nondestructive evaluation (NDE). A particular area of interest is the impact of advanced eddy current (EC) NDE technology. This paper presents an overview of work that supports this effort in the areas of numerical electromagnetic (EM) modeling, data analysis, signal processing, and visualization of EC inspection results. Finite-element modeling has been utilized to study conventional and emerging EC probe designs. This research is aimed at determining probe responses to flaw morphologies of current interest. Application of signal processing and automated data analysis algorithms has also been addressed. Efforts have focused on assessment of frequency and spatial domain filters and implementation of more effective data analysis and display methods. Data analysis studies have dealt with implementation of linear and nonlinear multivariate models to relate EC inspection parameters to steam generator tubing defect size and structural integrity. Various signal enhancement and visualization schemes are also being evaluated and will serve as integral parts of computer-aided data analysis algorithms. Results from this research will ultimately be substantiated through testing on laboratory-grown and in-service-degraded tubes.

  7. Large-eddy simulations with wall models

    NASA Technical Reports Server (NTRS)

    Cabot, W.

    1995-01-01

    The near-wall viscous and buffer regions of wall-bounded flows generally require a large expenditure of computational resources to be resolved adequately, even in large-eddy simulation (LES). Often as much as 50% of the grid points in a computational domain are devoted to these regions. The dense grids that this implies also generally require small time steps for numerical stability and/or accuracy. It is commonly assumed that the inner wall layers are near equilibrium, so that the standard logarithmic law can be applied as the boundary condition for the wall stress well away from the wall, for example, in the logarithmic region, obviating the need to expend large amounts of grid points and computational time in this region. This approach is commonly employed in LES of planetary boundary layers, and it has also been used for some simple engineering flows. In order to calculate accurately a wall-bounded flow with coarse wall resolution, one requires the wall stress as a boundary condition. The goal of this work is to determine the extent to which equilibrium and boundary layer assumptions are valid in the near-wall regions, to develop models for the inner layer based on such assumptions, and to test these modeling ideas in some relatively simple flows with different pressure gradients, such as channel flow and flow over a backward-facing step. Ultimately, models that perform adequately in these situations will be applied to more complex flow configurations, such as an airfoil.

  8. A Semi-parametric Multivariate Gap-filling Model for Eddy Covariance Latent Heat Flux

    NASA Astrophysics Data System (ADS)

    Li, M.; Chen, Y.

    2010-12-01

    Quantitative descriptions of latent heat fluxes are important to study the water and energy exchanges between terrestrial ecosystems and the atmosphere. The eddy covariance approaches have been recognized as the most reliable technique for measuring surface fluxes over time scales ranging from hours to years. However, unfavorable micrometeorological conditions, instrument failures, and applicable measurement limitations may cause inevitable flux gaps in time series data. Development and application of suitable gap-filling techniques are crucial to estimate long term fluxes. In this study, a semi-parametric multivariate gap-filling model was developed to fill latent heat flux gaps for eddy covariance measurements. Our approach combines the advantages of a multivariate statistical analysis (principal component analysis, PCA) and a nonlinear interpolation technique (K-nearest-neighbors, KNN). The PCA method was first used to resolve the multicollinearity relationships among various hydrometeorological factors, such as radiation, soil moisture deficit, LAI, and wind speed. The KNN method was then applied as a nonlinear interpolation tool to estimate the flux gaps as the weighted sum latent heat fluxes with the K-nearest distances in the PCs’ domain. Two years, 2008 and 2009, of eddy covariance and hydrometeorological data from a subtropical mixed evergreen forest (the Lien-Hua-Chih Site) were collected to calibrate and validate the proposed approach with artificial gaps after standard QC/QA procedures. The optimal K values and weighting factors were determined by the maximum likelihood test. The results of gap-filled latent heat fluxes conclude that developed model successful preserving energy balances of daily, monthly, and yearly time scales. Annual amounts of evapotranspiration from this study forest were 747 mm and 708 mm for 2008 and 2009, respectively. Nocturnal evapotranspiration was estimated with filled gaps and results are comparable with other studies

  9. The development of an ultralow frequency eddy current instrument for the detection and sizing of stress corrosion cracks: Final report

    SciTech Connect

    Hayford, D.T.

    1988-05-04

    Eddy current testing has received only limited application to ferrous materials because the high permeability of the material in combination with the normally high frequency of the eddy current instrument results in a very small depth of penetration of the eddy currents into the material. The objectives of this research program were threefold. The first goal was to develop an eddy current instrument with frequencies low enough to penetrate pipeline steel. The second was to use the new instrument to develop techniques for locating stress-corrosion cracks (SCC) on coated pipelines without requiring the removal of the coating. Our last goal was to develop methods of characterizing SCC, i.e., determining the lengths and depths of the defects. We accomplished two out of these three goals; we were able to build the instrument and use it to detect SCC in pipelines. Simple defect characterization algorithms (measuring defect length and depth) have been more difficult to develop. At present we can estimate the depth of ''long'' defects (relative to the coil diameter) but have problems with shorter ones. 24 figs.

  10. Test for fine defects beneath precision surface using novel magneto-optic/pulsed eddy current NDT technology

    NASA Astrophysics Data System (ADS)

    Zhou, Mu-cheng; Wang, Ya-ping

    2006-02-01

    A Magneto-Optic (MO) system is being utilized in aerospace industry for the detection of surface defects. To extend the capability of the instrument to detect and quantify sub-surface defect, we present a new Magneto-Optic (MO)/Pulsed Eddy Current (PEC) imaging system which, supported by laser, is being used for testing fine defects beneath precision surface of mental materials. The technique is based on the combination of pulsed eddy current excitation and magneto-optic sensing and imaging. In the experimental set-up, the induction of eddy currents is conventionally performed by pulsed current excitation coil over the object surface. The magnetic field induced by the pulsed eddy currents is detected by using Faraday effect. For this target, a laser beam passes through a special crystal, Faraday rotation glass (FRG), which has its easy axis of magnetization in the direction of normal magnetic fields and memory effect, integrated in the excitation coil. The polarization direction of laser beam is rotated in crystal depending on local magnetic field. The area distribution of rotation angle caused by fine defects beneath precision surface is transformed into "light" or "dark" picture using an optical set-up, which consists of a conventional microscope, a lighting, a polarimeter, and a CCD sensor. In the paper, the basic principle, configuration of the test equipment and image processing are described, and an original experimental results of fine artificial defects beneath precision surface of mental materials is presented.

  11. Impact of eddy-wind interaction on eddy demographics and phytoplankton community structure in a model of the North Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Anderson, Laurence A.; McGillicuddy, Dennis J.; Maltrud, Mathew E.; Lima, Ivan D.; Doney, Scott C.

    2011-09-01

    Two eddy-resolving (0.1°) physical-biological simulations of the North Atlantic Ocean are compared, one with the surface momentum flux computed only from wind velocities and the other using the difference between air and ocean velocity vectors. This difference in forcing has a significant impact on the intensities and relative number of different types of mesoscale eddies in the Sargasso Sea. Eddy/wind interaction significantly reduces eddy intensities and increases the number of mode-water eddies and "thinnies" relative to regular cyclones and anticyclones; it also modifies upward isopycnal displacements at the base of the euphotic zone, increasing them in the centers of mode water eddies and at the edges of cyclones, and decreasing them in the centers of cyclones. These physical changes increase phytoplankton growth rates and biomass in mode-water eddies, bringing the biological simulation into better agreement with field data. These results indicate the importance of including the eddy/wind interaction in simulations of the physics and biology of eddies in the subtropical North Atlantic. However, eddy intensities in the simulation with eddy/wind interaction are lower than observed, which suggests a decrease in horizontal viscosity or an increase in horizontal grid resolution will be necessary to regain the observed level of eddy activity.

  12. Research on defects inspection of solder balls based on eddy current pulsed thermography.

    PubMed

    Zhou, Xiuyun; Zhou, Jinlong; Tian, Guiyun; Wang, Yizhe

    2015-10-13

    In order to solve tiny defect detection for solder balls in high-density flip-chip, this paper proposed feasibility study on the effect of detectability as well as classification based on eddy current pulsed thermography (ECPT). Specifically, numerical analysis of 3D finite element inductive heat model is generated to investigate disturbance on the temperature field for different kind of defects such as cracks, voids, etc. The temperature variation between defective and non-defective solder balls is monitored for defects identification and classification. Finally, experimental study is carried on the diameter 1mm tiny solder balls by using ECPT and verify the efficacy of the technique.

  13. Large Eddy Simulations of Kelvin Helmholtz instabilities at high Reynolds number stratified flows

    NASA Astrophysics Data System (ADS)

    Brown, Dana; Goodman, Lou; Raessi, Mehdi

    2015-11-01

    Simulations of Kelvin Helmholtz Instabilities (KHI) at high Reynolds numbers are performed using the Large Eddy Simulation technique. Reynolds numbers up to 100,000 are achieved using our model. The resulting data set is used to examine the effect of Reynolds number on various statistics, including dissipation flux coefficient, turbulent kinetic energy budget, and Thorpe length scale. It is shown that KHI are qualitatively different at high Re, up to and including the onset of vortex pairing and billow collapse and quantitatively different afterward. The effect of Richardson number is also examined. The results are discussed as they apply to ocean experiments.

  14. Research on defects inspection of solder balls based on eddy current pulsed thermography.

    PubMed

    Zhou, Xiuyun; Zhou, Jinlong; Tian, Guiyun; Wang, Yizhe

    2015-01-01

    In order to solve tiny defect detection for solder balls in high-density flip-chip, this paper proposed feasibility study on the effect of detectability as well as classification based on eddy current pulsed thermography (ECPT). Specifically, numerical analysis of 3D finite element inductive heat model is generated to investigate disturbance on the temperature field for different kind of defects such as cracks, voids, etc. The temperature variation between defective and non-defective solder balls is monitored for defects identification and classification. Finally, experimental study is carried on the diameter 1mm tiny solder balls by using ECPT and verify the efficacy of the technique. PMID:26473871

  15. Eddy diffusion coefficients and the variance of the atmosphere 30-60 km

    NASA Technical Reports Server (NTRS)

    Nastrom, G. D.; Belmont, A. D.; Brown, D. E.

    1980-01-01

    The results of numerical models or of new observational programs are checked by comparing them with past observations. In view of the differing analysis techniques or differing data samples, the eddy diffusivities presented here agree remarkably well with past estimates. However, in the application of K-values to two-dimensional models, the actual magnitude of the diffusivities is no more important than their spatial patterns, i.e., their gradients with height and latitude. It should thus be noted that the present patterns are often much different from those of past results.

  16. EDDY CURRENT SYSTEM FOR DETECTION OF CRACKING BENEATH BRAIDING IN CORRUGATED METAL HOSE

    SciTech Connect

    Wincheski, Buzz; Simpson, John; Hall, George

    2009-03-03

    In this paper an eddy current system for the detection of partially-through-the-thickness cracks in corrugated metal hose is presented. Design criteria based upon the geometry and conductivity of the part are developed and applied to the fabrication of a prototype inspection system. Experimental data are used to highlight the capabilities of the system and an image processing technique is presented to improve flaw detection capabilities. A case study for detection of cracking damage in a space shuttle radiator retract flex hoses is also presented.

  17. Eddy Current System for Detection of Cracking Beneath Braiding in Corrugated Metal Hose

    NASA Technical Reports Server (NTRS)

    Wincheski, Buzz; Simpson, John; Hall, George

    2008-01-01

    In this paper an eddy current system for the detection of partially-through-the-thickness cracks in corrugated metal hose is presented. Design criteria based upon the geometry and conductivity of the part are developed and applied to the fabrication of a prototype inspection system. Experimental data are used to highlight the capabilities of the system and an image processing technique is presented to improve flaw detection capabilities. A case study for detection of cracking damage in a space shuttle radiator retract flex hoses is also presented.

  18. Research on Defects Inspection of Solder Balls Based on Eddy Current Pulsed Thermography

    PubMed Central

    Zhou, Xiuyun; Zhou, Jinlong; Tian, Guiyun; Wang, Yizhe

    2015-01-01

    In order to solve tiny defect detection for solder balls in high-density flip-chip, this paper proposed feasibility study on the effect of detectability as well as classification based on eddy current pulsed thermography (ECPT). Specifically, numerical analysis of 3D finite element inductive heat model is generated to investigate disturbance on the temperature field for different kind of defects such as cracks, voids, etc. The temperature variation between defective and non-defective solder balls is monitored for defects identification and classification. Finally, experimental study is carried on the diameter 1mm tiny solder balls by using ECPT and verify the efficacy of the technique. PMID:26473871

  19. Characterization of coatings on magnetic metal using the swept-frequency eddy current method

    NASA Astrophysics Data System (ADS)

    Tai, Cheng-Chi

    2000-08-01

    A measurement technique using the swept-frequency eddy current (SFEC) method for determining the thickness, conductivity, and permeability of metallic coatings on metal substrates for the case when either coating, substrate, or both are magnetic was developed. This technique involved using the empirically determined permeability of the metals as input to the model calculation. This technique is demonstrated for nickel layers (25-200 μm) over copper substrates, copper layers (25-200 μm) over nickel substrates, and zinc layers (50-400 μm) over steel substrates. The electrical impedance was measured for air-core coils in the presence and absence of the layer using a 4194A Hewlett-Packard impedance analyzer. An analytic closed-form solution for calculating the impedance of a cylindrical air-core probe over a layered metallic half-space is presented. The determination of coating thickness and conductivity and permeability of the metals is based on the comparison of the data taken with air-core coils and theoretical calculation that using the closed-form solution developed. Most of the cases studied show experiment and theory agreeing fairly well, within 10%, with no adjustable parameters. The physical phenomena of eddy currents interaction with the coated magnetic metals are also discussed.

  20. The wineglass effect shapes particle export to the deep ocean in mesoscale eddies

    NASA Astrophysics Data System (ADS)

    Waite, Anya M.; Stemmann, Lars; Guidi, Lionel; Calil, Paulo H. R.; Hogg, Andrew Mc C.; Feng, Ming; Thompson, Peter A.; Picheral, Marc; Gorsky, Gaby

    2016-09-01

    Mesoscale eddies in the ocean strongly impact the distribution of planktonic particles, mediating carbon fluxes over ~1/3 of the world ocean. However, mechanisms controlling particle transport through eddies are complex and challenging to measure in situ. Here we show the subsurface distribution of eddy particles funneled into a wineglass shape down to 1000 m, leading to a sevenfold increase of vertical carbon flux in the eddy center versus the eddy flanks, the "wineglass effect". We show that the slope of the wineglass (R) is the ratio of particle sinking velocity to the radially inward velocity, such that R represents a tool to predict radial particle movement (here 0.05 m s-1). A simple model of eddy spindown predicts such an ageostrophic flow concentrating particles in the eddy center. We explore how size-specific particle flux toward the eddy center impacts eddies' biogeochemistry and export fluxes.

  1. Formation of Ice Eddies in Mountain Valleys of East Antarctica

    NASA Astrophysics Data System (ADS)

    Meyer, C. R.; Creyts, T. T.; Rice, J. R.

    2014-12-01

    Observations show complex structures deep in ice sheets. Folds and accretion ice have been reported for both Greenland and Antarctica. Mismatched stratigraphy in the nearby GRIP and GISP2 cores in Greenland as well as overturning in the NEEM ice core suggest variable behavior within the ice sheet. Furthermore, ice penetrating radar data taken across both ice sheets shows folding at scales up to half the ice thickness. Because individual strata can be traced through the folds, it is clear that ice flow dynamics play an important role. Here we consider the possible formation of recirculation eddies in subglacial mountain valleys. Modeling the ice as a creeping homogeneous power-law shear-thinning viscous fluid, recirculation eddies are shown to form in valleys when the angle of the wall is steep enough that fluid inside the valley cannot return to the main flow. This is analogous to Moffatt eddies for a Newtonian viscous fluid. Using a no-slip boundary condition at the valley wall, ice can recirculate in these valleys indefinitely. We examine eddies in the basal ice using theory and simulations based on topography of the Gamburtsev Subglacial Mountains in central East Antarctica. The Gamburtsevs are a large mountain range (~750km×250km) with steep relief typical of an alpine glacier system. Analytic results point to a necessary critical angle, and for a power-law shear-thinning fluid such as ice, these eddies occur at lower angles than in a Newtonian viscous fluid. We further develop metrics for determining valleys that are likely to contain eddies based on flow velocity and the total relief of the valley. Our simulations show that in some valleys eddies of order one hundred meters form. We then compare our simulations to radar observations to show potential for near-bed stratigraphic disturbances.

  2. Dry-air Transport by Transient Eddies within an MJO

    NASA Astrophysics Data System (ADS)

    Yasunaga, K.

    2013-12-01

    In order to improve our understanding of an MJO onset over the Indian Ocean, a field observational campaign called CINDY/DYNAMO was conducted over the central equatorial Indian Ocean in October-December 2011. During the campaign, large-scale-organized convection associated with an MJO broke out, and formation and development of transient eddies were prominent in the mid-level (around 550 hPa or melting level) during the MJO active phase over the Indian Ocean. Eddies have a zonal scale of 2000-3000 km and time scale of 8-10 days. Following the shift of the convective active area associated with an MJO, the eddy packet moves to the east, although each eddy slowly propagates to the west. Associated with the development of the eddy, dry air is transported from the higher latitude into the equator in the mid-level. Vertical transport of water vapor moistens the mid troposphere during almost the entire period of CINDY/DYNAMO campaign. However, the drying associated with the eddy exceeds the moistening by the vertical motion, when the eddy is reinforced within an MJO convection envelope, and suppresses the convection around the equator. As a result, convectively-active regions move to the east or higher latitudes. Time-latitude cross section of water vapor mixing ratios in the mid-level (600-500hPa) over the Indian Ocean (70E-90E) during CINDY/DYNAMO campaign. The data source is ERA-Interim. The areas exceeding 5 g/kg are shaded. Time-latitude cross section of water vapor changes due to the horizontal advection by rotational winds in the mid-level (600-500hPa) over the Indian Ocean (70E-90E) during CINDY/DYNAMO campaign. The data source is ERA-Interim. The areas falling below -5E-6 g/kg are shaded.

  3. Large Eddy Simulation of Powered Fontan Hemodynamics

    PubMed Central

    Delorme, Y.; Anupindi, K.; Kerlo, A.E.; Shetty, D.; Rodefeld, M.; Chen, J.; Frankel, S.

    2012-01-01

    Children born with univentricular heart disease typically must undergo three open heart surgeries within the first 2–3 years of life to eventually establish the Fontan circulation. In that case the single working ventricle pumps oxygenated blood to the body and blood returns to the lungs flowing passively through the Total Cavopulmonary Connection (TCPC) rather than being actively pumped by a subpulmonary ventricle. The TCPC is a direct surgical connection between the superior and inferior vena cava and the left and right pulmonary arteries. We have postulated that a mechanical pump inserted into this circulation providing a 3–5 mmHg pressure augmentation will reestablish bi-ventricular physiology serving as a bridge-to-recovery, bridge-to-transplant or destination therapy as a “biventricular Fontan” circulation. The Viscous Impeller Pump (VIP) has been proposed by our group as such an assist device. It is situated in the center of the 4-way TCPC intersection and spins pulling blood from the vena cavae and pushing it into the pulmonary arteries. We hypothesized that Large Eddy Simulation (LES) using high-order numerical methods are needed to capture unsteady powered and unpowered Fontan hemodynamics. Inclusion of a mechanical pump into the CFD further complicates matters due to the need to account for rotating machinery. In this study, we focus on predictions from an in-house high-order LES code (WenoHemo™) for unpowered and VIP-powered idealized TCPC hemodynamics with quantitative comparisons to Stereoscopic Particle Imaging Velocimetry (SPIV) measurements. Results are presented for both instantaneous flow structures and statistical data. Simulations show good qualitative and quantitative agreement with measured data. PMID:23177085

  4. Recurrence Analysis of Eddy Covariance Fluxes

    NASA Astrophysics Data System (ADS)

    Lange, Holger; Flach, Milan; Foken, Thomas; Hauhs, Michael

    2015-04-01

    The eddy covariance (EC) method is one key method to quantify fluxes in biogeochemical cycles in general, and carbon and energy transport across the vegetation-atmosphere boundary layer in particular. EC data from the worldwide net of flux towers (Fluxnet) have also been used to validate biogeochemical models. The high resolution data are usually obtained at 20 Hz sampling rate but are affected by missing values and other restrictions. In this contribution, we investigate the nonlinear dynamics of EC fluxes using Recurrence Analysis (RA). High resolution data from the site DE-Bay (Waldstein-Weidenbrunnen) and fluxes calculated at half-hourly resolution from eight locations (part of the La Thuile dataset) provide a set of very long time series to analyze. After careful quality assessment and Fluxnet standard gapfilling pretreatment, we calculate properties and indicators of the recurrent structure based both on Recurrence Plots as well as Recurrence Networks. Time series of RA measures obtained from windows moving along the time axis are presented. Their interpretation is guided by three different questions: (1) Is RA able to discern periods where the (atmospheric) conditions are particularly suitable to obtain reliable EC fluxes? (2) Is RA capable to detect dynamical transitions (different behavior) beyond those obvious from visual inspection? (3) Does RA contribute to an understanding of the nonlinear synchronization between EC fluxes and atmospheric parameters, which is crucial for both improving carbon flux models as well for reliable interpolation of gaps? (4) Is RA able to recommend an optimal time resolution for measuring EC data and for analyzing EC fluxes? (5) Is it possible to detect non-trivial periodicities with a global RA? We will demonstrate that the answers to all five questions is affirmative, and that RA provides insights into EC dynamics not easily obtained otherwise.

  5. Rare earth magnets resisting eddy currents

    SciTech Connect

    Pan, W.; Li, W.; Cui, L.Y.; Li, X.M.; Guo, Z.H.

    1999-09-01

    Magnets with high electrical resistance were prepared by electrically isolating Sm{sub 2}Co{sub 17} and Nd{sub 2}Fe{sub 14}B powder particles. It is done by a polymer mixture consisting of epoxy polyester-insulant (EPI), polyvinylbutyral (PVB), epoxy resin (ER) and silane coupling (SC). The properties of interest for anisotropic Sm{sub 2}Co{sub 17} and isotropic Nd{sub 2}Fe{sub 14}B magnets respectively are {rho} = 1 x 10{sup 5} {Omega} {minus}cm{sup 2}/m, Br = 6.8 kGs, {sub 1}H{sub c} = 10.0 kOe, (BH){sub max} = 9.2 MGOe in 5% EPI, 4%PVB, 2%ER, 1%SC and {rho} = 9.4 x 10{sup 4} {Omega} {minus}cm{sup 2}/m, Br = 4.5kG, {sub i}H{sub c} = 9.5 kOe, (BH){sub max} = 4.3 MGOe in 4%EPI, 3%PVB, 2% ER, 1%SC. The insulated magnets exhibit far better magnetic stability than those of sintered and bonded magnets after magnetizing in radio frequency. The insulated Sm{sub 2}Co{sub 17} magnet has the best performance in resisting eddy current. In 500 kHz frequency, 830 Oe magnetizing-field and in one minute, the irreversible loss of recoil remanence is 1.47% and 22.2% respectively for insulated Sm{sub 2}Co{sub 17} and Nd{sub 2}Fe{sub 14}B magnets.

  6. Intrathermocline eddies in the Southern Indian Ocean

    NASA Astrophysics Data System (ADS)

    Nauw, J. J.; van Aken, H. M.; Lutjeharms, J. R. E.; de Ruijter, W. P. M.

    2006-03-01

    In 2001, two relatively saline intrathermocline eddies (ITEs) were observed southeast of Madagascar at 200 m depth. They are characterized by a subsurface salinity maximum of over 35.8 at potential temperatures between 18° and 22°C. The oxygen concentrations within the high salinity cores are slightly elevated compared with those of the surrounding water. Their horizontal extent is about 180 km, several times the Rossby deformation radius, while their thickness is about 150 m. The observed circulation around the ITEs is anticyclonic and maximum velocities of 20 to 30 cm/s are observed at 200 m depth. In these cores the potential density anomaly (25.0 < γ < 25.9 kg/m3) has a relatively low vertical gradient and therefore a low planetary potential vorticity. The hydrographic properties of these ITEs are distinctly different from those of the surrounding thermocline water, and especially from the much fresher water mass in the East Madagascar Current. Strong evidence has been found that the distant formation area of the water mass in the ITEs is the subtropical Southern Indian Ocean east of 90°E and south of 25°S, where Subtropical Underwater (STUW) is formed with similar characteristics. Similar high-salinity cores as the ITEs are also found in the thermocline around 200 m depth along an almost zonal section between Madagascar and 100°E. Differences between the hydrographic properties of these cores and the ITEs near Madagascar may partly be explained by interannual variations in the temperature and salinity of the surface mixed layer water in the possible formation area.

  7. Analysis of Massively Separated Flows of Aircraft Using Detached Eddy Simulation

    NASA Astrophysics Data System (ADS)

    Morton, Scott

    2002-08-01

    An important class of turbulent flows of aerodynamic interest are those characterized by massive separation, e.g., the flow around an aircraft at high angle of attack. Numerical simulation is an important tool for analysis, though traditional models used in the solution of the Reynolds-averaged Navier-Stokes (RANS) equations appear unable to accurately account for the time-dependent and three-dimensional motions governing flows with massive separation. Large-eddy simulation (LES) is able to resolve these unsteady three-dimensional motions, yet is cost prohibitive for high Reynolds number wall-bounded flows due to the need to resolve the small scale motions in the boundary layer. Spalart et. al. proposed a hybrid technique, Detached-Eddy Simulation (DES), which takes advantage of the often adequate performance of RANS turbulence models in the "thin," typically attached regions of the flow. In the separated regions of the flow the technique becomes a Large Eddy Simulation, directly resolving the time-dependent and unsteady features that dominate regions of massive separation. The current work applies DES to a 70 degree sweep delta wing at 27 degrees angle of attack, a geometrically simple yet challenging flowfield that exhibits the unsteady three-dimensional massively separated phenomena of vortex breakdown. After detailed examination of this basic flowfield, the method is demonstrated on three full aircraft of interest characterized by massive separation, the F-16 at 45 degrees angle of attack, the F-15 at 65 degree angle of attack (with comparison to flight test), and the C-130 in a parachute drop condition at near stall speed with cargo doors open.

  8. Large-eddy simulation of heavy particle dispersion in wall-bounded turbulent flows

    SciTech Connect

    Salvetti, M.V.

    2015-03-10

    Capabilities and accuracy issues in Lagrangian tracking of heavy particles in velocity fields obtained from large-eddy simulations (LES) of wall-bounded turbulent flows are reviewed. In particular, it is shown that, if no subgrid scale (SGS) model is added to the particle motion equations, particle preferential concentration and near-wall accumulation are significantly underestimated. Results obtained with SGS modeling for the particle motion equations based on approximate deconvolution are briefly recalled. Then, the error purely due to filtering in particle tracking in LES flow fields is singled out and analyzed. The statistical properties of filtering errors are characterized in turbulent channel flow both from an Eulerian and a Lagrangian viewpoint. Implications for stochastic SGS modeling in particle motion equations are briefly outlined.

  9. Analysis of Eddy Current Capabilities for the Detection of Outer Diameter Stress Corrosion Cracking in Small Bore Metallic Structures

    NASA Technical Reports Server (NTRS)

    Wincheski, Buzz; Williams, Phillip; Simpson, John

    2007-01-01

    The use of eddy current techniques for the detection of outer diameter damage in tubing and many complex aerospace structures often requires the use of an inner diameter probe due to a lack of access to the outside of the part. In small bore structures the probe size and orientation are constrained by the inner diameter of the part, complicating the optimization of the inspection technique. Detection of flaws through a significant remaining wall thickness becomes limited not only by the standard depth of penetration, but also geometrical aspects of the probe. Recently, an orthogonal eddy current probe was developed for detection of such flaws in Space Shuttle Primary Reaction Control System (PRCS) Thrusters. In this case, the detection of deeply buried stress corrosion cracking by an inner diameter eddy current probe was sought. Probe optimization was performed based upon the limiting spatial dimensions, flaw orientation, and required detection sensitivity. Analysis of the probe/flaw interaction was performed through the use of finite and boundary element modeling techniques. Experimental data for the flaw detection capabilities, including a probability of detection study, will be presented along with the simulation data. The results of this work have led to the successful deployment of an inspection system for the detection of stress corrosion cracking in Space Shuttle Primary Reaction Control System (PRCS) Thrusters.

  10. Pulsed eddy current and ultrasonic data fusion applied to stress measurement

    NASA Astrophysics Data System (ADS)

    Habibalahi, A.; Safizadeh, M. S.

    2014-05-01

    Stress measurement and its variation are key problems in the operating performance of materials. Stress can affect the material properties and the life of components. There are several destructive and nondestructive techniques that are used to measure stress. However, no single nondestructive testing (NDT) technique or method is satisfactory to fully assess stress. This paper presents an NDT data fusion method to improve stress measurement. An aluminum alloy 2024 specimen subjected to stress simulation is nondestructively inspected using pulsed eddy current and ultrasonic techniques. Following these nondestructive examinations, the information gathered from these two NDT methods has been fused using a suitable fuzzy combination operator. The results obtained with these processes are presented in this paper and their efficiency is discussed. It is shown that the fusion of NDT data with a suitable fuzzy operator can be adequate to improve the reliability of stress measurements.

  11. Nondestructive inspection assessment of eddy current and electrochemical analysis to separate inconel and stainless steel alloys

    SciTech Connect

    Moore, D.G.; Sorensen, N.R.

    1998-02-01

    This report presents a nondestructive inspection assessment of eddy current and electrochemical analysis to separate inconel alloys from stainless steel alloys as well as an evaluation of cleaning techniques to remove a thermal oxide layer on aircraft exhaust components. The results of this assessment are presented in terms of how effective each technique classifies a known exhaust material. Results indicate that either inspection technique can separate inconel and stainless steel alloys. Based on the experiments conducted, the electrochemical spot test is the optimum for use by airframe and powerplant mechanics. A spot test procedure is proposed for incorporation into the Federal Aviation Administration Advisory Circular 65-9A Airframe & Powerplant Mechanic - General Handbook. 3 refs., 70 figs., 7 tabs.

  12. Non-Contact EDDY Current Hole Eccentricity and Diameter Measurement

    NASA Technical Reports Server (NTRS)

    Chern, E. James

    1998-01-01

    Precision holes are among the most critical features of a mechanical component. Deviations from permissible tolerances can impede operation and result in unexpected failure. We have developed an automated non-contact eddy current hole diameter and eccentricity measuring system. The operating principle is based on the eddy current lift-off effect, which is the coil impedance as a function of the distance between the coil and the test object. An absolute eddy current probe rotates in the hole. The impedance of each angular position is acquired and input to the computer for integration and analysis. The eccentricity of the hole is the profile of the impedance as a function of angular position as compared to a straight line, an ideal hole. The diameter of the hole is the sum of the diameter of the probe and twice the distance-calibrated impedance. An eddy current image is generated by integrating angular scans for a plurality of depths between the top and bottom to display the eccentricity profile. This system can also detect and image defects in the hole. The method for non-contact eddy current hole diameter and eccentricity measurement has been granted a patent by the U.S. Patent and Trademark Office.

  13. Recent freshening of the East Australian Current and its eddies

    NASA Astrophysics Data System (ADS)

    Rykova, Tatiana; Oke, Peter R.

    2015-11-01

    The East Australian Current (EAC) has a relatively weak mean flow and an energetic eddy field that dominates the circulation. The properties of the mean flow have been studied in detail, but the changes in the eddy field have received little attention. We analyze Argo temperature and salinity profiles for 2005-2012 to construct a picture of the time-mean and time-varying properties of EAC eddies. We find that eddies and the surrounding waters of the western Tasman Sea are freshening at a rate of 0.017-0.025 practical salinity unit/yr over the top 100 m, with no significant temperature change. Consistent with the observations, fields from an eddy-resolving ocean model show freshening, with no temperature trend. Moreover, the model results indicate that observed changes are significant in the context of the variability over the last 20 years and may be part of a multiyear (perhaps decadal) cycle. We attribute the freshening of the region to increased precipitation off Eastern Australia.

  14. Coastal Kelvin waves and dynamics of Gulf of Aden eddies

    NASA Astrophysics Data System (ADS)

    Valsala, Vinu K.; Rao, Rokkam R.

    2016-10-01

    The Gulf of Aden (GA) is a small semi-enclosed oceanic region between the Red Sea and the western Arabian Sea. The GA is characterised with westward propagating cyclonic and anti-cyclonic eddies throughout the year. The genesis and propagation of these eddies into the GA have been the focus of several studies which concluded that oceanic instabilities (both barotropic and baroclinic) as well as the Rossby waves from the Arabian Sea are the responsible mechanisms for the presence and maintenance of these eddies. Using a high-resolution ( 11 km) reduced gravity hydrodynamic layered model with controlled lateral boundary conditions at the three sides of the GA here we show yet another factor, the coastally propagating Kelvin waves along the coastal Arabia (coasts of Oman and Yemen), is also critically important in setting up a favourable condition for the oceanic instabilities and sustenance of meso-scale eddies in the GA. These Kelvin waves at both seasonal and intra-seasonal time scales are found play an important role in the timing and amplitudes of eddies observed in the GA.

  15. The Death of Two Eddies, Against the Shelf

    NASA Astrophysics Data System (ADS)

    Zavala-Trujillo, B.; Badan, A.; Rivas, D.; Ochoa, J.; Sheinbaum, J.; Candela, J.

    2007-05-01

    A set of five moorings deployed in front of the coast of Tamaulipas, western Gulf of Mexico, provided fourteen months (from August 2004 to November 2005) of surface to bottom observations of currents and temperature that document the processes associated with the collision and dissipation of two warm mesoscale eddies with the continental slope. Two Loop Current eddies (Titanic and Ulysses) were identified reaching the study area during the observation period. On September 2004, the two southernmost 2000-m moorings show that temperature and salinity increases throughout the entire water column, related to eddy Titanic; similarily; on April 2005, eddy Ulysses caused a strong increase of temperature in the 3500-m mooring. The velocity field suggests three different régimes: a coastal region, the continental slope currents, and the abyssal circulation. Over the slope, three different layers can be identified: a surface layer (above 500 m depth), influenced by eddies and transients, a deep layer (under de 1900 m) with a persistent southerly current and a transition layer (from 500 to 1900 m) that separates them. The variance ellipses at ~ 700 m at the 3500-m mooring have no a predominant orientation of the mayor axis. At the northernmost 2000-m mooring, the axis of maximum variation is oriented with the bathymetry, but at the southernmost 2000-m mooring it is perpendicular to the coast. The spectral characteristics of the measurements are also discussed.

  16. Effects of Drake Passage on a strongly eddying global ocean

    NASA Astrophysics Data System (ADS)

    Viebahn, Jan P.; Heydt, Anna S.; Le Bars, Dewi; Dijkstra, Henk A.

    2016-05-01

    The climate impact of ocean gateway openings during the Eocene-Oligocene transition is still under debate. Previous model studies employed grid resolutions at which the impact of mesoscale eddies has to be parameterized. We present results of a state-of-the-art eddy-resolving global ocean model with a closed Drake Passage and compare with results of the same model at noneddying resolution. An analysis of the pathways of heat by decomposing the meridional heat transport into eddy, horizontal, and overturning circulation components indicates that the model behavior on the large scale is qualitatively similar at both resolutions. Closing Drake Passage induces (i) sea surface warming around Antarctica due to equatorward expansion of the subpolar gyres, (ii) the collapse of the overturning circulation related to North Atlantic Deep Water formation leading to surface cooling in the North Atlantic, and (iii) significant equatorward eddy heat transport near Antarctica. However, quantitative details significantly depend on the chosen resolution. The warming around Antarctica is substantially larger for the noneddying configuration (˜5.5°C) than for the eddying configuration (˜2.5°C). This is a consequence of the subpolar mean flow which partitions differently into gyres and circumpolar current at different resolutions. We conclude that for a deciphering of the different mechanisms active in Eocene-Oligocene climate change detailed analyses of the pathways of heat in the different climate subsystems are crucial in order to clearly identify the physical processes actually at work.

  17. Regional Scaling of Airborne Eddy Covariance Flux Observation

    NASA Astrophysics Data System (ADS)

    Sachs, T.; Serafimovich, A.; Metzger, S.; Kohnert, K.; Hartmann, J.

    2014-12-01

    The earth's surface is tightly coupled to the global climate system by the vertical exchange of energy and matter. Thus, to better understand and potentially predict changes to our climate system, it is critical to quantify the surface-atmosphere exchange of heat, water vapor, and greenhouse gases on climate-relevant spatial and temporal scales. Currently, most flux observations consist of ground-based, continuous but local measurements. These provide a good basis for temporal integration, but may not be representative of the larger regional context. This is particularly true for the Arctic, where site selection is additionally bound by logistical constraints, among others. Airborne measurements can overcome this limitation by covering distances of hundreds of kilometers over time periods of a few hours. The Airborne Measurements of Methane Fluxes (AIRMETH) campaigns are designed to quantitatively and spatially explicitly address this issue: The research aircraft POLAR 5 is used to acquire thousands of kilometers of eddy-covariance flux data. During the AIRMETH-2012 and AIRMETH-2013 campaigns we measured the turbulent exchange of energy, methane, and (in 2013) carbon dioxide over the North Slope of Alaska, USA, and the Mackenzie Delta, Canada. Here, we present the potential of environmental response functions (ERFs) for quantitatively linking flux observations to meteorological and biophysical drivers in the flux footprints. We use wavelet transforms of the original high-frequency data to improve spatial discretization of the flux observations. This also enables the quantification of continuous and biophysically relevant land cover properties in the flux footprint of each observation. A machine learning technique is then employed to extract and quantify the functional relationships between flux observations and the meteorological and biophysical drivers. The resulting ERFs are used to extrapolate fluxes over spatio-temporally explicit grids of the study area. The

  18. A normal stress subgrid-scale eddy viscosity model in large eddy simulation

    NASA Technical Reports Server (NTRS)

    Horiuti, K.; Mansour, N. N.; Kim, John J.

    1993-01-01

    The Smagorinsky subgrid-scale eddy viscosity model (SGS-EVM) is commonly used in large eddy simulations (LES) to represent the effects of the unresolved scales on the resolved scales. This model is known to be limited because its constant must be optimized in different flows, and it must be modified with a damping function to account for near-wall effects. The recent dynamic model is designed to overcome these limitations but is compositionally intensive as compared to the traditional SGS-EVM. In a recent study using direct numerical simulation data, Horiuti has shown that these drawbacks are due mainly to the use of an improper velocity scale in the SGS-EVM. He also proposed the use of the subgrid-scale normal stress as a new velocity scale that was inspired by a high-order anisotropic representation model. The testing of Horiuti, however, was conducted using DNS data from a low Reynolds number channel flow simulation. It was felt that further testing at higher Reynolds numbers and also using different flows (other than wall-bounded shear flows) were necessary steps needed to establish the validity of the new model. This is the primary motivation of the present study. The objective is to test the new model using DNS databases of high Reynolds number channel and fully developed turbulent mixing layer flows. The use of both channel (wall-bounded) and mixing layer flows is important for the development of accurate LES models because these two flows encompass many characteristic features of complex turbulent flows.

  19. Linear eddy mixing based tabulation and artificial neural networks for large eddy simulations of turbulent flames

    SciTech Connect

    Sen, Baris Ali; Menon, Suresh

    2010-01-15

    A large eddy simulation (LES) sub-grid model is developed based on the artificial neural network (ANN) approach to calculate the species instantaneous reaction rates for multi-step, multi-species chemical kinetics mechanisms. The proposed methodology depends on training the ANNs off-line on a thermo-chemical database representative of the actual composition and turbulence (but not the actual geometrical problem) of interest, and later using them to replace the stiff ODE solver (direct integration (DI)) to calculate the reaction rates in the sub-grid. The thermo-chemical database is tabulated with respect to the thermodynamic state vector without any reduction in the number of state variables. The thermo-chemistry is evolved by stand-alone linear eddy mixing (LEM) model simulations under both premixed and non-premixed conditions, where the unsteady interaction of turbulence with chemical kinetics is included as a part of the training database. The proposed methodology is tested in LES and in stand-alone LEM studies of three distinct test cases with different reduced mechanisms and conditions. LES of premixed flame-turbulence-vortex interaction provides direct comparison of the proposed ANN method against DI and ANNs trained on thermo-chemical database created using another type of tabulation method. It is shown that the ANN trained on the LEM database can capture the correct flame physics with accuracy comparable to DI, which cannot be achieved by ANN trained on a laminar premix flame database. A priori evaluation of the ANN generality within and outside its training domain is carried out using stand-alone LEM simulations as well. Results in general are satisfactory, and it is shown that the ANN provides considerable amount of memory saving and speed-up with reasonable and reliable accuracy. The speed-up is strongly affected by the stiffness of the reduced mechanism used for the computations, whereas the memory saving is considerable regardless. (author)

  20. Plankton dynamics in a cyclonic eddy in the Southern California Current System

    NASA Astrophysics Data System (ADS)

    Chenillat, Fanny; Franks, Peter J. S.; Rivière, Pascal; Capet, Xavier; Grima, Nicolas; Blanke, Bruno

    2015-08-01

    The California Current System is an eastern boundary upwelling system (EBUS) with high biological production along the coast. Oligotrophic offshore waters create cross-shore gradients of biological and physical properties, which are affected by intense mesoscale eddy activity. The influence of eddies on ecosystem dynamics in EBUS is still in debate. To elucidate the mechanisms that influence the dynamics of ecosystems trapped in eddies, and the relative contribution of horizontal and vertical advection in determining local production, we analyze a particular cyclonic eddy using Lagrangian particle-tracking analyses of numerical Eulerian. The eddy formed in a coastal upwelling system; coastal waters trapped in the eddy enabled it to leave the upwelling region with high concentrations of plankton and nutrients. The ecosystem was initially driven mainly by recycling of biological material. As the eddy moved offshore, production in its core was enhanced compared to eddy exterior waters through Ekman pumping of nitrate from below the euphotic zone; this Ekman pumping was particularly effective due to the shallow nitracline in the eddy compared to eddy exterior waters. Both eddy trapping and Ekman pumping helped to isolate and maintain the ecosystem productivity in the eddy core. This study shows the importance of cyclonic eddies for biological production in EBUS: they contribute both to the redistribution of the coastal upwelling ecosystem and are local regions of enhanced new production. Together, these processes impact cross-shore gradients of important biological properties.

  1. Event Detection and Visualization of Ocean Eddies based on SSH and Velocity Field

    NASA Astrophysics Data System (ADS)

    Matsuoka, Daisuke; Araki, Fumiaki; Inoue, Yumi; Sasaki, Hideharu

    2016-04-01

    Numerical studies of ocean eddies have been progressed using high-resolution ocean general circulation models. In order to understand ocean eddies from simulation results with large amount of information volume, it is necessary to visualize not only distribution of eddies of each time step, but also events or phenomena of eddies. However, previous methods cannot precisely detect eddies, especially, during the events such as eddies' amalgamation, bifurcation. In the present study, we propose a new approach of eddy's detection, tracking and event visualization based on sea surface height (SSH) and velocity field. The proposed method detects eddies region as well as streams and currents region, and classifies detected eddies into several types. By tracking the time-varying change of classified eddies, it is possible to detect not only eddies event such as amalgamation and bifurcation but also the interaction between eddy and ocean current. As a result of visualizing detected eddies and events, we succeeded in creating the movie which enables us to intuitively understand the region of interest.

  2. Neurodegeneration with Brain Iron Accumulation

    MedlinePlus

    ... Diversity Find People About NINDS NINDS Neurodegeneration with Brain Iron Accumulation Information Page Synonym(s): Hallervorden-Spatz Disease, ... done? Clinical Trials Organizations What is Neurodegeneration with Brain Iron Accumulation? Neurodegeneration with brain iron accumulation (NBIA) ...

  3. Surface-atmosphere decoupling limits accumulation at Summit, Greenland.

    PubMed

    Berkelhammer, Max; Noone, David C; Steen-Larsen, Hans Christian; Bailey, Adriana; Cox, Christopher J; O'Neill, Michael S; Schneider, David; Steffen, Konrad; White, James W C

    2016-04-01

    Despite rapid melting in the coastal regions of the Greenland Ice Sheet, a significant area (~40%) of the ice sheet rarely experiences surface melting. In these regions, the controls on annual accumulation are poorly constrained owing to surface conditions (for example, surface clouds, blowing snow, and surface inversions), which render moisture flux estimates from myriad approaches (that is, eddy covariance, remote sensing, and direct observations) highly uncertain. Accumulation is partially determined by the temperature dependence of saturation vapor pressure, which influences the maximum humidity of air parcels reaching the ice sheet interior. However, independent proxies for surface temperature and accumulation from ice cores show that the response of accumulation to temperature is variable and not generally consistent with a purely thermodynamic control. Using three years of stable water vapor isotope profiles from a high altitude site on the Greenland Ice Sheet, we show that as the boundary layer becomes increasingly stable, a decoupling between the ice sheet and atmosphere occurs. The limited interaction between the ice sheet surface and free tropospheric air reduces the capacity for surface condensation to achieve the rate set by the humidity of the air parcels reaching interior Greenland. The isolation of the surface also acts to recycle sublimated moisture by recondensing it onto fog particles, which returns the moisture back to the surface through gravitational settling. The observations highlight a unique mechanism by which ice sheet mass is conserved, which has implications for understanding both past and future changes in accumulation rate and the isotopic signal in ice cores from Greenland.

  4. Mesoscale eddies in the South China Sea: Mean properties, spatiotemporal variability, and impact on thermohaline structure

    NASA Astrophysics Data System (ADS)

    Chen, Gengxin; Hou, Yijun; Chu, Xiaoqing

    2011-06-01

    We investigated mean properties and the spatiotemporal variability of eddies in the South China Sea (SCS) by analyzing more than 7000 eddies corresponding to 827 eddy tracks, identified using the winding angle method and 17 years of satellite altimetry data. Eddies are mainly generated in a northeast-southwest direction and southwest of Luzon Strait. There is no significant difference between the numbers of two types of eddies (anticyclonic and cyclonic) in most regions. The mean radius and lifetime of eddies are 132 km and 8.8 weeks, respectively, both depending on where the eddies are formed. Anticyclonic and cyclonic eddies tend to deform during their lifetimes in different ways. Furthermore, eddy propagation and evolution characteristics are examined. In the northern SCS, eddies mainly propagate southwestward along the continental slope with velocities of 5.0-9.0 cm s-1, while in the central SCS, eddies tend to move with slight divergence but still in a quasi-westward direction with velocities of 2.0-6.4 cm s-1. Eddy propagation in the western basin to the east of Vietnam is quite random, with no uniform propagate direction. Investigation of 38 long-lived eddies shows that eddies have a swift growing phase during the first 12 weeks and then a slow decaying phase that affects the eddy radii and eddy energy densities. Nevertheless, vorticity has less variability. In addition, the effect of eddies on the thermocline and halocline is analyzed using 763 Argo temperature profile data. Cyclonic eddies drive the thermocline shallower and thinner and significantly strengthen the thermocline intensity, whereas anticyclonic eddies cause the thermocline to deepen and thicken and weaken the thermocline intensity to a certain degree. The halocline impacted by cyclonic eddies is also shallower and thinner than that impacted by anticyclonic eddies. Finally, eddy temporal variations are examined at seasonal and interannual scales. Eddy activity is sensitive to the wind stress

  5. Exact temporal eddy current compensation in magnetic resonance imaging systems.

    PubMed

    Morich, M A; Lampman, D A; Dannels, W R; Goldie, F D

    1988-01-01

    A step-response method has been developed to extract the properties (amplitudes and decay time constants) of intrinsic-eddy-current-sourced magnetic fields generated in whole-body magnetic resonance imaging systems when pulsed field gradients are applied. Exact compensation for the eddy-current effect is achieved through a polynomial rooting procedure and matrix inversion once the 2 N properties of the N-term decay process are known. The output of the inversion procedure yields the required characteristics of the filter for spectrum magnitude and phase equalization. The method is described for the general case along with experimental results for one-, two-, and three-term inversions. The method's usefulness is demonstrated for the usually difficult case of long-term (200-1000-ms) eddy-current compensation. Field-gradient spectral flatness measurements over 30 mHz-100 Hz are given to validate the method.

  6. Baroclinic adjustment. [parameterization of eddy flux effects on atmospheric temperature

    NASA Technical Reports Server (NTRS)

    Stone, P. H.

    1978-01-01

    A detailed comparison is presented of the actual shear in the atmosphere with the critical shear given by the two-layer model of Phillips (1954), in which there is a critical temperature gradient separating stable conditions from baroclinically unstable ones. A very simple parameterization of the effect of eddy fluxes on atmospheric temperature is suggested, where the parameterization includes beta effects. The parameterization is illustrated by applying it in a one-dimensional heat-balance climate model. Enhancement of the eddy flux in a continuous atmosphere under supercritical conditions is stressed. This enhancement leads to a negative feedback between the meridional eddy flux of heat and the meridional temperature gradient. The feedback restricts gradients to values near the critical value, a process referred to as baroclinic adjustment. This should facilitate the development of simple climate models involving feedbacks associated with both the meridional vertical temperature structure.

  7. Global interior eddy available potential energy diagnosed from Argo floats

    NASA Astrophysics Data System (ADS)

    Roullet, Guillaume; Capet, Xavier; Maze, Guillaume

    2014-03-01

    By combining all Argo profiles for the period 2002 to present, a cumulative density function is constructed on a 3-D grid of the global ocean. This function quantifies the statistics of isopycnals: time-averaged density, root-mean square of isopycnal displacement, and eddy available potential energy (EAPE). EAPE is the analogue of the eddy kinetic energy, but for the potential energy reservoir. Because it is essentially tied to the spatial structure and magnitude of mesoscale activity, EAPE is an important quantity that should be useful to evaluate eddy resolving/permitting model turbulence and circulation. Among other striking features are the turbulent behavior of Pacific and southern Atlantic Tsuchiya jets and subsurface EAPE maxima in some parts of the ocean, particularly in the Southern Ocean.

  8. Strong eddy compensation for the Gulf Stream heat transport

    NASA Astrophysics Data System (ADS)

    Saenko, Oleg A.

    2015-12-01

    Using a high-resolution ocean model forced with high-resolution atmospheric fields, a 5 year mean heat budget of the upper ocean in the Gulf Stream (GS) region is analyzed. The heat brought to the region with the mean flows along the GS path is 2-3 times larger than the heat loss to the atmosphere, with the difference being balanced by a strong cooling effect due to lateral eddy heat fluxes. However, over a broad area off the Grand Banks, the eddies warm the uppermost ocean layers, partly compensating for the loss of heat to the atmosphere. The upward eddy heat flux, which brings heat from the deeper ocean to the upper layers, is 30-80% of the surface heat loss.

  9. Large-Eddy Simulation of Wind-Plant Aerodynamics: Preprint

    SciTech Connect

    Churchfield, M. J.; Lee, S.; Moriarty, P. J.; Martinez, L. A.; Leonardi, S.; Vijayakumar, G.; Brasseur, J. G.

    2012-01-01

    In this work, we present results of a large-eddy simulation of the 48 multi-megawatt turbines composing the Lillgrund wind plant. Turbulent inflow wind is created by performing an atmospheric boundary layer precursor simulation and turbines are modeled using a rotating, variable-speed actuator line representation. The motivation for this work is that few others have done wind plant large-eddy simulations with a substantial number of turbines, and the methods for carrying out the simulations are varied. We wish to draw upon the strengths of the existing simulations and our growing atmospheric large-eddy simulation capability to create a sound methodology for performing this type of simulation. We have used the OpenFOAM CFD toolbox to create our solver.

  10. Eddies reduce denitrification and compress habitats in the Arabian Sea

    NASA Astrophysics Data System (ADS)

    Lachkar, Zouhair; Smith, Shafer; Lévy, Marina; Pauluis, Olivier

    2016-09-01

    The combination of high biological production and weak oceanic ventilation in regions, such as the northern Indian Ocean and the eastern Pacific and Atlantic, cause large-scale oxygen minimum zones (OMZs) that profoundly affect marine habitats and alter key biogeochemical cycles. Here we investigate the effects of eddies on the Arabian Sea OMZ—the world's thickest—using a suite of regional model simulations with increasing horizontal resolution. We find that isopycnal eddy transport of oxygen to the OMZ region limits the extent of suboxia so reducing denitrification, increasing the supply of nitrate to the surface, and thereby enhancing biological production. That same enhanced production generates more organic matter in the water column, amplifying oxygen consumption below the euphotic zone, thus increasing the extent of hypoxia. Eddy-driven ventilation likely plays a similar role in other low-oxygen regions and thus may be crucial in shaping marine habitats and modulating the large-scale marine nitrogen cycle.

  11. Large eddy interactions in a turbulent channel flow

    NASA Technical Reports Server (NTRS)

    Hong, S. K.

    1985-01-01

    The dynamic processes of large eddies in a turbulent channel flow have been examined by utilizing an orthogonal expansion of the velocity fluctuation, known in the literature as the Proper Orthogonal Decomposition Theorem. The mathematical form of these functions is unknown in contrast to the Fourier analysis. Attention is focused on the nonlinear, turbulence-turbulence interaction process in the dynamical equation for large eddies (the first term in the expansion). The nonlinear interactions of the components of the first mode are treated exactly, but influences of higher modes are modeled. This requires adjustment of both the skewness and the effective Reynolds number so that the energy equilibrium of the large eddies is ensured when the mean velocity distribution is assumed known for experiments. Computational results show that the first mode contributes significantly to turbulent intensities and possesses a structural and statistical character similar to that of the entire flow.

  12. Using eddy covariance to estimate air-sea gas transfer velocity for oxygen

    NASA Astrophysics Data System (ADS)

    Andersson, Andreas; Rutgersson, Anna; Sahlée, Erik

    2016-07-01

    Air-sea gas transfer velocity for O2 is calculated using directly measured fluxes with the eddy covariance technique. It is a direct method and is frequently used to determine fluxes of heat, humidity, and CO2, but has not previously been used to estimate transfer velocities for O2, using atmospheric eddy covariance data. The measured O2 fluxes are upward directed, in agreement with the measured air-sea gradient of the O2 concentration, and opposite to the direction of the simultaneously measured CO2 fluxes. The transfer velocities estimated from measurements are compared with prominent wind speed parameterizations of the transfer velocity for CO2 and O2, previously established from various measurement techniques. Our result indicates stronger wind speed dependence for the transfer velocity of O2 compared to CO2 starting at intermediate wind speeds. This stronger wind speed dependence appears to coincide with the onset of whitecap formation in the flux footprint and the strong curvature of a cubic wind-dependent function for the transfer velocity provides the best fit to the data. Additional data using the measured O2 flux and an indirect method (based on the Photosynthetic Quotient) to estimate oxygen concentration in water, support the stronger wind dependence for the transfer velocity of O2 compared to CO2.

  13. Using eddy covariance to estimate air–sea gas transfer velocity for oxygen

    NASA Astrophysics Data System (ADS)

    Andersson, Andreas; Rutgersson, Anna; Sahlée, Erik

    2016-07-01

    Air-sea gas transfer velocity for O2 is calculated using directly measured fluxes with the eddy covariance technique. It is a direct method and is frequently used to determine fluxes of heat, humidity, and CO2, but has not previously been used to estimate transfer velocities for O2, using atmospheric eddy covariance data. The measured O2 fluxes are upward directed, in agreement with the measured air-sea gradient of the O2 concentration, and opposite to the direction of the simultaneously measured CO2 fluxes. The transfer velocities estimated from measurements are compared with prominent wind speed parameterizations of the transfer velocity for CO2 and O2, previously established from various measurement techniques. Our result indicates stronger wind speed dependence for the transfer velocity of O2 compared to CO2 starting at intermediate wind speeds. This stronger wind speed dependence appears to coincide with the onset of whitecap formation in the flux footprint and the strong curvature of a cubic wind-dependent function for the transfer velocity provides the best fit to the data. Additional data using the measured O2 flux and an indirect method (based on the Photosynthetic Quotient) to estimate oxygen concentration in water, support the stronger wind dependence for the transfer velocity of O2 compared to CO2.

  14. Eddy correlation measurements of NO, NO{sub 2}, and O{sub 3} fluxes

    SciTech Connect

    Gao, W.; Wesely, M.L.; Cook, D.R.; martin, T.J.

    1996-06-01

    The micrometeorological technique of eddy correlation was used to measure the vertical fluxes of NO, NO{sub 2}, and ozone in rural North Carolian during spring 1995 as part of the Natural emission of Oxidant precurssors-Validation of techniques and Assessment (NOVA) field experiment. Net flux densities were measured at heights 5 and 10 m above an agricultural field with short corn plants and large amount of exposed bare soil between the rows. Large upward eddy fluxes of NO{sub 2} were seen, and strong NO emissions from the soil were measured by collaborators using environmental enclosures on the soil surface. Data indicate that about 50% of the nitrogen emitted from the soil as NO was converted into NO{sub 2} at 5 m. Rest of the emitted nitrogen may remain as NO flux and be returned back to the vegetation and soil by deposition. Divergence of the NO{sub 2} and O{sub 3} fluxes were detected between 5 and 10 m. This is consistent with likely net NO{sub 2} and O{sub 3} destruction rates. The data will be used to help develop parameterizations of the flux of nitrogen oxides into the lower troposphere.

  15. Plastids and Carotenoid Accumulation.

    PubMed

    Li, Li; Yuan, Hui; Zeng, Yunliu; Xu, Qiang

    2016-01-01

    Plastids are ubiquitously present in plants and are the organelles for carotenoid biosynthesis and storage. Based on their morphology and function, plastids are classified into various types, i.e. proplastids, etioplasts, chloroplasts, amyloplasts, and chromoplasts. All plastids, except proplastids, can synthesize carotenoids. However, plastid types have a profound effect on carotenoid accumulation and stability. In this chapter, we discuss carotenoid biosynthesis and regulation in various plastids with a focus on carotenoids in chromoplasts. Plastid transition related to carotenoid biosynthesis and the different capacity of various plastids to sequester carotenoids and the associated effect on carotenoid stability are described in light of carotenoid accumulation in plants. PMID:27485226

  16. Plastids and Carotenoid Accumulation.

    PubMed

    Li, Li; Yuan, Hui; Zeng, Yunliu; Xu, Qiang

    2016-01-01

    Plastids are ubiquitously present in plants and are the organelles for carotenoid biosynthesis and storage. Based on their morphology and function, plastids are classified into various types, i.e. proplastids, etioplasts, chloroplasts, amyloplasts, and chromoplasts. All plastids, except proplastids, can synthesize carotenoids. However, plastid types have a profound effect on carotenoid accumulation and stability. In this chapter, we discuss carotenoid biosynthesis and regulation in various plastids with a focus on carotenoids in chromoplasts. Plastid transition related to carotenoid biosynthesis and the different capacity of various plastids to sequester carotenoids and the associated effect on carotenoid stability are described in light of carotenoid accumulation in plants.

  17. The Effect of Mesoscale Eddies On Oceanic Stratification

    NASA Astrophysics Data System (ADS)

    Vallis, G. K.; Henning, C. C.

    Understanding the structure of the subtropical thermocline is an important, indeed classical, problem in dynamical oceanography. Many models have fallen into two camps -- diffusive theories, following Robinson and Stommel, and advective theo- ries, following Welander. More recently it has been shown that, at least in the absence of mesoscale eddies, the subtropical thermocline consists of an advective upper part (a 'ventilated thermocline'), with a diffusive base -- that is, the lower part of the main thermocline is an internal boundary layer. The thermocline in the Southern Ocean is a rather different beast, because the lack of meridional boundaries means that the gyre circulation is largely absent and such classical theories do not directly apply. Further- more, it has been suggested that the dynamics of the Southern Ocean might greatly influence the thermocline worldwide. However, these theories are not complete. Among the most egregious omissions is that of the potential effect of mesoscale eddies, and here we explore that problem. We integrate to equilibrium a wind- and buoyancy-driven eddy-resolving primitive- equations ocean model, both in an idealized basin and in a circumpolar channel. We find that mesoscale eddies do have a significant quantitative affect on the structure of the thermocline. In the subtropics, the signature of the two-thermocline model (an advective upper thermocline and a diffusive base) remains, even in the presence of vigorous eddying activity, whereas in the circumpolar channel the eddies appear to be a dominant process determining the stratification. We discuss the dynamics and thermodynamics of these flows, and present some simple theoretical ideas to partially explain some of our results.

  18. Improved Climate Simulations through a Stochastic Parameterization of Ocean Eddies

    NASA Astrophysics Data System (ADS)

    Williams, Paul; Howe, Nicola; Gregory, Jonathan; Smith, Robin; Joshi, Manoj

    2016-04-01

    In climate simulations, the impacts of the sub-grid scales on the resolved scales are conventionally represented using deterministic closure schemes, which assume that the impacts are uniquely determined by the resolved scales. Stochastic parameterization relaxes this assumption, by sampling the sub-grid variability in a computationally inexpensive manner. This presentation shows that the simulated climatological state of the ocean is improved in many respects by implementing a simple stochastic parameterization of ocean eddies into a coupled atmosphere-ocean general circulation model. Simulations from a high-resolution, eddy-permitting ocean model are used to calculate the eddy statistics needed to inject realistic stochastic noise into a low-resolution, non-eddy-permitting version of the same model. A suite of four stochastic experiments is then run to test the sensitivity of the simulated climate to the noise definition, by varying the noise amplitude and decorrelation time within reasonable limits. The addition of zero-mean noise to the ocean temperature tendency is found to have a non-zero effect on the mean climate. Specifically, in terms of the ocean temperature and salinity fields both at the surface and at depth, the noise reduces many of the biases in the low-resolution model and causes it to more closely resemble the high-resolution model. The variability of the strength of the global ocean thermohaline circulation is also improved. It is concluded that stochastic ocean perturbations can yield reductions in climate model error that are comparable to those obtained by refining the resolution, but without the increased computational cost. Therefore, stochastic parameterizations of ocean eddies have the potential to significantly improve climate simulations. Reference PD Williams, NJ Howe, JM Gregory, RS Smith, and MM Joshi (2016) Improved Climate Simulations through a Stochastic Parameterization of Ocean Eddies. Journal of Climate, under revision.

  19. Large Eddy Simulation of Cirrus Clouds

    NASA Technical Reports Server (NTRS)

    Wu, Ting; Cotton, William R.

    1999-01-01

    The Regional Atmospheric Modeling System (RAMS) with mesoscale interactive nested-grids and a Large-Eddy Simulation (LES) version of RAMS, coupled to two-moment microphysics and a new two-stream radiative code were used to investigate the dynamic, microphysical, and radiative aspects of the November 26, 1991 cirrus event. Wu (1998) describes the results of that research in full detail and is enclosed as Appendix 1. The mesoscale nested grid simulation successfully reproduced the large scale circulation as compared to the Mesoscale Analysis and Prediction System's (MAPS) analyses and other observations. Three cloud bands which match nicely to the three cloud lines identified in an observational study (Mace et al., 1995) are predicted on Grid #2 of the nested grids, even though the mesoscale simulation predicts a larger west-east cloud width than what was observed. Large-eddy simulations (LES) were performed to study the dynamical, microphysical, and radiative processes in the 26 November 1991 FIRE 11 cirrus event. The LES model is based on the RAMS version 3b developed at Colorado State University. It includes a new radiation scheme developed by Harrington (1997) and a new subgrid scale model developed by Kosovic (1996). The LES model simulated a single cloud layer for Case 1 and a two-layer cloud structure for Case 2. The simulations demonstrated that latent heat release can play a significant role in the formation and development of cirrus clouds. For the thin cirrus in Case 1, the latent heat release was insufficient for the cirrus clouds to become positively buoyant. However, in some special cases such as Case 2, positively buoyant cells can be embedded within the cirrus layers. These cells were so active that the rising updraft induced its own pressure perturbations that affected the cloud evolution. Vertical profiles of the total radiative and latent heating rates indicated that for well developed, deep, and active cirrus clouds, radiative cooling and latent

  20. Low frequency eddy current benchmark study for model validation

    SciTech Connect

    Mooers, R. D.; Boehnlein, T. R.; Cherry, M. R.; Knopp, J. S.; Aldrin, J. C.; Sabbagh, H. A.

    2011-06-23

    This paper presents results of an eddy current model validation study. Precise measurements were made using an impedance analyzer to investigate changes in impedance due to Electrical Discharge Machining (EDM) notches in aluminum plates. Each plate contained one EDM notch at an angle of 0, 10, 20, or 30 degrees from the normal of the plate surface. Measurements were made with the eddy current probe both scanning parallel and perpendicular to the notch length. The experimental response from the vertical and oblique notches will be reported and compared to results from different numerical simulation codes.

  1. Eddy current NDE performance demonstrations using simulation tools

    SciTech Connect

    Maurice, L.; Costan, V.; Guillot, E.; Thomas, P.

    2013-01-25

    To carry out performance demonstrations of the Eddy-Current NDE processes applied on French nuclear power plants, EDF studies the possibility of using simulation tools as an alternative to measurements on steam generator tube mocks-up. This paper focuses on the strategy led by EDF to assess and use code{sub C}armel3D and Civa, on the case of Eddy-Current NDE on wears problem which may appear in the U-shape region of steam generator tubes due to the rubbing of anti-vibration bars.

  2. Enhanced Eddy-Current Detection Of Weld Flaws

    NASA Technical Reports Server (NTRS)

    Van Wyk, Lisa M.; Willenberg, James D.

    1992-01-01

    Mixing of impedances measured at different frequencies reduces noise and helps reveal flaws. In new method, one excites eddy-current probe simultaneously at two different frequencies; usually, one of which integral multiple of other. Resistive and reactive components of impedance of eddy-current probe measured at two frequencies, mixed in computer, and displayed in real time on video terminal of computer. Mixing of measurements obtained at two different frequencies often "cleans up" displayed signal in situations in which band-pass filtering alone cannot: mixing removes most noise, and displayed signal resolves flaws well.

  3. PHREATOPHYTE WATER USE ESTIMATED BY EDDY-CORRELATION METHODS.

    USGS Publications Warehouse

    Weaver, H.L.; Weeks, E.P.; Campbell, G.S.; Stannard, D.I.; Tanner, B.D.

    1986-01-01

    Water-use was estimated for three phreatophyte communities: a saltcedar community and an alkali-Sacaton grass community in New Mexico, and a greasewood rabbit-brush-saltgrass community in Colorado. These water-use estimates were calculated from eddy-correlation measurements using three different analyses, since the direct eddy-correlation measurements did not satisfy a surface energy balance. The analysis that seems to be most accurate indicated the saltcedar community used from 58 to 87 cm (23 to 34 in. ) of water each year. The other two communities used about two-thirds this quantity.

  4. Vessel eddy current measurement for the National Spherical Torus Experiment

    SciTech Connect

    Gates, D.A.; Menard, J.E.; Marsala, R.J.

    2004-12-01

    A simple analog circuit that measures the National Spherical Torus Experiment (NSTX) axisymmetric eddy current distribution has been designed and constructed. It is based on simple circuit model of the NSTX vacuum vessel that was calibrated using a special axisymmetric eddy current code which was written so that accuracy was maintained in the vicinity of the current filaments [J. Menard, J. Fusion Tech. (to be published)]. The measurement and the model have been benchmarked against data from numerous vacuum shots and they are in excellent agreement. This is an important measurement that helps give more accurate equilibrium reconstructions.

  5. Eddy current NDE performance demonstrations using simulation tools

    NASA Astrophysics Data System (ADS)

    Maurice, L.; Costan, V.; Guillot, E.; Thomas, P.

    2013-01-01

    To carry out performance demonstrations of the Eddy-Current NDE processes applied on French nuclear power plants, EDF studies the possibility of using simulation tools as an alternative to measurements on steam generator tube mocks-up. This paper focuses on the strategy led by EDF to assess and use code_Carmel3D and Civa, on the case of Eddy-Current NDE on wears problem which may appear in the U-shape region of steam generator tubes due to the rubbing of anti-vibration bars.

  6. Low Frequency Eddy Current Benchmark Study for Model Validation

    NASA Astrophysics Data System (ADS)

    Mooers, R. D.; Cherry, M. R.; Knopp, J. S.; Aldrin, J. C.; Sabbagh, H. A.; Boehnlein, T. R.

    2011-06-01

    This paper presents results of an eddy current model validation study. Precise measurements were made using an impedance analyzer to investigate changes in impedance due to Electrical Discharge Machining (EDM) notches in aluminum plates. Each plate contained one EDM notch at an angle of 0, 10, 20, or 30 degrees from the normal of the plate surface. Measurements were made with the eddy current probe both scanning parallel and perpendicular to the notch length. The experimental response from the vertical and oblique notches will be reported and compared to results from different numerical simulation codes.

  7. Large Eddy Simulations and Turbulence Modeling for Film Cooling

    NASA Technical Reports Server (NTRS)

    Acharya, Sumanta

    1999-01-01

    The objective of the research is to perform Direct Numerical Simulations (DNS) and Large Eddy Simulations (LES) for film cooling process, and to evaluate and improve advanced forms of the two equation turbulence models for turbine blade surface flow analysis. The DNS/LES were used to resolve the large eddies within the flow field near the coolant jet location. The work involved code development and applications of the codes developed to the film cooling problems. Five different codes were developed and utilized to perform this research. This report presented a summary of the development of the codes and their applications to analyze the turbulence properties at locations near coolant injection holes.

  8. Eddy current step heating thermography for quantitatively evaluation

    NASA Astrophysics Data System (ADS)

    He, Yunze; Pan, Mengchun; Chen, Dixiang; Tian, GuiYun; Zhang, Hong

    2013-11-01

    This Letter proposed eddy current step heating thermography (ECSHT) combing eddy current excitation with SHT. It has been verified through numerical and experimental studies that the temperature-time1/2 curve can be used to detect the subsurface defects. Separation time was defined and extracted from temperature responses as characteristic feature. Experiment studies with mild steel sample were conducted, and the experimental results showed that two features representing separation time can be used to measure the defect's depth based on their linear relationships.

  9. Chimpanzee accumulative stone throwing.

    PubMed

    Kühl, Hjalmar S; Kalan, Ammie K; Arandjelovic, Mimi; Aubert, Floris; D'Auvergne, Lucy; Goedmakers, Annemarie; Jones, Sorrel; Kehoe, Laura; Regnaut, Sebastien; Tickle, Alexander; Ton, Els; van Schijndel, Joost; Abwe, Ekwoge E; Angedakin, Samuel; Agbor, Anthony; Ayimisin, Emmanuel Ayuk; Bailey, Emma; Bessone, Mattia; Bonnet, Matthieu; Brazolla, Gregory; Buh, Valentine Ebua; Chancellor, Rebecca; Cipoletta, Chloe; Cohen, Heather; Corogenes, Katherine; Coupland, Charlotte; Curran, Bryan; Deschner, Tobias; Dierks, Karsten; Dieguez, Paula; Dilambaka, Emmanuel; Diotoh, Orume; Dowd, Dervla; Dunn, Andrew; Eshuis, Henk; Fernandez, Rumen; Ginath, Yisa; Hart, John; Hedwig, Daniela; Ter Heegde, Martijn; Hicks, Thurston Cleveland; Imong, Inaoyom; Jeffery, Kathryn J; Junker, Jessica; Kadam, Parag; Kambi, Mohamed; Kienast, Ivonne; Kujirakwinja, Deo; Langergraber, Kevin; Lapeyre, Vincent; Lapuente, Juan; Lee, Kevin; Leinert, Vera; Meier, Amelia; Maretti, Giovanna; Marrocoli, Sergio; Mbi, Tanyi Julius; Mihindou, Vianet; Moebius, Yasmin; Morgan, David; Morgan, Bethan; Mulindahabi, Felix; Murai, Mizuki; Niyigabae, Protais; Normand, Emma; Ntare, Nicolas; Ormsby, Lucy Jayne; Piel, Alex; Pruetz, Jill; Rundus, Aaron; Sanz, Crickette; Sommer, Volker; Stewart, Fiona; Tagg, Nikki; Vanleeuwe, Hilde; Vergnes, Virginie; Willie, Jacob; Wittig, Roman M; Zuberbuehler, Klaus; Boesch, Christophe

    2016-01-01

    The study of the archaeological remains of fossil hominins must rely on reconstructions to elucidate the behaviour that may have resulted in particular stone tools and their accumulation. Comparatively, stone tool use among living primates has illuminated behaviours that are also amenable to archaeological examination, permitting direct observations of the behaviour leading to artefacts and their assemblages to be incorporated. Here, we describe newly discovered stone tool-use behaviour and stone accumulation sites in wild chimpanzees reminiscent of human cairns. In addition to data from 17 mid- to long-term chimpanzee research sites, we sampled a further 34 Pan troglodytes communities. We found four populations in West Africa where chimpanzees habitually bang and throw rocks against trees, or toss them into tree cavities, resulting in conspicuous stone accumulations at these sites. This represents the first record of repeated observations of individual chimpanzees exhibiting stone tool use for a purpose other than extractive foraging at what appear to be targeted trees. The ritualized behavioural display and collection of artefacts at particular locations observed in chimpanzee accumulative stone throwing may have implications for the inferences that can be drawn from archaeological stone assemblages and the origins of ritual sites.

  10. Chimpanzee accumulative stone throwing

    PubMed Central

    Kühl, Hjalmar S.; Kalan, Ammie K.; Arandjelovic, Mimi; Aubert, Floris; D’Auvergne, Lucy; Goedmakers, Annemarie; Jones, Sorrel; Kehoe, Laura; Regnaut, Sebastien; Tickle, Alexander; Ton, Els; van Schijndel, Joost; Abwe, Ekwoge E.; Angedakin, Samuel; Agbor, Anthony; Ayimisin, Emmanuel Ayuk; Bailey, Emma; Bessone, Mattia; Bonnet, Matthieu; Brazolla, Gregory; Buh, Valentine Ebua; Chancellor, Rebecca; Cipoletta, Chloe; Cohen, Heather; Corogenes, Katherine; Coupland, Charlotte; Curran, Bryan; Deschner, Tobias; Dierks, Karsten; Dieguez, Paula; Dilambaka, Emmanuel; Diotoh, Orume; Dowd, Dervla; Dunn, Andrew; Eshuis, Henk; Fernandez, Rumen; Ginath, Yisa; Hart, John; Hedwig, Daniela; Ter Heegde, Martijn; Hicks, Thurston Cleveland; Imong, Inaoyom; Jeffery, Kathryn J.; Junker, Jessica; Kadam, Parag; Kambi, Mohamed; Kienast, Ivonne; Kujirakwinja, Deo; Langergraber, Kevin; Lapeyre, Vincent; Lapuente, Juan; Lee, Kevin; Leinert, Vera; Meier, Amelia; Maretti, Giovanna; Marrocoli, Sergio; Mbi, Tanyi Julius; Mihindou, Vianet; Moebius, Yasmin; Morgan, David; Morgan, Bethan; Mulindahabi, Felix; Murai, Mizuki; Niyigabae, Protais; Normand, Emma; Ntare, Nicolas; Ormsby, Lucy Jayne; Piel, Alex; Pruetz, Jill; Rundus, Aaron; Sanz, Crickette; Sommer, Volker; Stewart, Fiona; Tagg, Nikki; Vanleeuwe, Hilde; Vergnes, Virginie; Willie, Jacob; Wittig, Roman M.; Zuberbuehler, Klaus; Boesch, Christophe

    2016-01-01

    The study of the archaeological remains of fossil hominins must rely on reconstructions to elucidate the behaviour that may have resulted in particular stone tools and their accumulation. Comparatively, stone tool use among living primates has illuminated behaviours that are also amenable to archaeological examination, permitting direct observations of the behaviour leading to artefacts and their assemblages to be incorporated. Here, we describe newly discovered stone tool-use behaviour and stone accumulation sites in wild chimpanzees reminiscent of human cairns. In addition to data from 17 mid- to long-term chimpanzee research sites, we sampled a further 34 Pan troglodytes communities. We found four populations in West Africa where chimpanzees habitually bang and throw rocks against trees, or toss them into tree cavities, resulting in conspicuous stone accumulations at these sites. This represents the first record of repeated observations of individual chimpanzees exhibiting stone tool use for a purpose other than extractive foraging at what appear to be targeted trees. The ritualized behavioural display and collection of artefacts at particular locations observed in chimpanzee accumulative stone throwing may have implications for the inferences that can be drawn from archaeological stone assemblages and the origins of ritual sites. PMID:26923684

  11. Chimpanzee accumulative stone throwing.

    PubMed

    Kühl, Hjalmar S; Kalan, Ammie K; Arandjelovic, Mimi; Aubert, Floris; D'Auvergne, Lucy; Goedmakers, Annemarie; Jones, Sorrel; Kehoe, Laura; Regnaut, Sebastien; Tickle, Alexander; Ton, Els; van Schijndel, Joost; Abwe, Ekwoge E; Angedakin, Samuel; Agbor, Anthony; Ayimisin, Emmanuel Ayuk; Bailey, Emma; Bessone, Mattia; Bonnet, Matthieu; Brazolla, Gregory; Buh, Valentine Ebua; Chancellor, Rebecca; Cipoletta, Chloe; Cohen, Heather; Corogenes, Katherine; Coupland, Charlotte; Curran, Bryan; Deschner, Tobias; Dierks, Karsten; Dieguez, Paula; Dilambaka, Emmanuel; Diotoh, Orume; Dowd, Dervla; Dunn, Andrew; Eshuis, Henk; Fernandez, Rumen; Ginath, Yisa; Hart, John; Hedwig, Daniela; Ter Heegde, Martijn; Hicks, Thurston Cleveland; Imong, Inaoyom; Jeffery, Kathryn J; Junker, Jessica; Kadam, Parag; Kambi, Mohamed; Kienast, Ivonne; Kujirakwinja, Deo; Langergraber, Kevin; Lapeyre, Vincent; Lapuente, Juan; Lee, Kevin; Leinert, Vera; Meier, Amelia; Maretti, Giovanna; Marrocoli, Sergio; Mbi, Tanyi Julius; Mihindou, Vianet; Moebius, Yasmin; Morgan, David; Morgan, Bethan; Mulindahabi, Felix; Murai, Mizuki; Niyigabae, Protais; Normand, Emma; Ntare, Nicolas; Ormsby, Lucy Jayne; Piel, Alex; Pruetz, Jill; Rundus, Aaron; Sanz, Crickette; Sommer, Volker; Stewart, Fiona; Tagg, Nikki; Vanleeuwe, Hilde; Vergnes, Virginie; Willie, Jacob; Wittig, Roman M; Zuberbuehler, Klaus; Boesch, Christophe

    2016-01-01

    The study of the archaeological remains of fossil hominins must rely on reconstructions to elucidate the behaviour that may have resulted in particular stone tools and their accumulation. Comparatively, stone tool use among living primates has illuminated behaviours that are also amenable to archaeological examination, permitting direct observations of the behaviour leading to artefacts and their assemblages to be incorporated. Here, we describe newly discovered stone tool-use behaviour and stone accumulation sites in wild chimpanzees reminiscent of human cairns. In addition to data from 17 mid- to long-term chimpanzee research sites, we sampled a further 34 Pan troglodytes communities. We found four populations in West Africa where chimpanzees habitually bang and throw rocks against trees, or toss them into tree cavities, resulting in conspicuous stone accumulations at these sites. This represents the first record of repeated observations of individual chimpanzees exhibiting stone tool use for a purpose other than extractive foraging at what appear to be targeted trees. The ritualized behavioural display and collection of artefacts at particular locations observed in chimpanzee accumulative stone throwing may have implications for the inferences that can be drawn from archaeological stone assemblages and the origins of ritual sites. PMID:26923684

  12. Scanning tone burst eddy-current thermography (S-TBET) for NDT of carbon fiber reinforced plastic (CFRP) components

    SciTech Connect

    Libin, M. N.; Maxfield, B. W.; Balasubramanian, Krishnan

    2014-02-18

    Tone Burst Eddy Current technique uses eddy current to apply transient heating inside a component and uses a conventional IR camera for visualization of the response to the transient heating. This technique has been earliest demonstrated for metallic components made of AL, Steel, Stainless Steel, etc., and for detection of cracks, corrosion and adhesive dis-bonds. Although, not nearly as conducting as metals, the Carbon Fibre Reinforced Plastic (CFRP) material absorbs measurable electromagnetic radiation in the frequency range above 10 kHz. When the surface temperature is observed on the surface that is being heated (defined as the surface just beneath and slightly to one side of the heating coil), the surface temperature increases with increasing frequency because the internal heating increases with frequency. A 2-D anisotropic transient Eddy current heating and thermal conduction model has been developed that provides a reasonable description of the processes described above. The inherent anisotropy of CFRP laminates is included in this model by calculating the heating due to three superimposed, tightly coupled isotropic layers having a specified ply-layup. The experimental apparatus consists of an induction heating coil and an IR camera with low NETD and high frame rates. The coil is moved over the sample using a stepper motor controlled manipulator. The IR data recording is synchronized with the motion control to provide a movie of the surface temperature over time. Several components were evaluated for detection of impact damage, location of stiffeners, etc. on CFRP components.

  13. Scanning tone burst eddy-current thermography (S-TBET) for NDT of carbon fiber reinforced plastic (CFRP) components

    NASA Astrophysics Data System (ADS)

    Libin, M. N.; Maxfield, B. W.; Balasubramanian, Krishnan

    2014-02-01

    Tone Burst Eddy Current technique uses eddy current to apply transient heating inside a component and uses a conventional IR camera for visualization of the response to the transient heating. This technique has been earliest demonstrated for metallic components made of AL, Steel, Stainless Steel, etc., and for detection of cracks, corrosion and adhesive dis-bonds. Although, not nearly as conducting as metals, the Carbon Fibre Reinforced Plastic (CFRP) material absorbs measurable electromagnetic radiation in the frequency range above 10 kHz. When the surface temperature is observed on the surface that is being heated (defined as the surface just beneath and slightly to one side of the heating coil), the surface temperature increases with increasing frequency because the internal heating increases with frequency. A 2-D anisotropic transient Eddy current heating and thermal conduction model has been developed that provides a reasonable description of the processes described above. The inherent anisotropy of CFRP laminates is included in this model by calculating the heating due to three superimposed, tightly coupled isotropic layers having a specified ply-layup. The experimental apparatus consists of an induction heating coil and an IR camera with low NETD and high frame rates. The coil is moved over the sample using a stepper motor controlled manipulator. The IR data recording is synchronized with the motion control to provide a movie of the surface temperature over time. Several components were evaluated for detection of impact damage, location of stiffeners, etc. on CFRP components.

  14. Segmentation and Tracking of Anticyclonic Eddies during a Submarine Volcanic Eruption Using Ocean Colour Imagery

    PubMed Central

    Marcello, Javier; Eugenio, Francisco; Estrada-Allis, Sheila; Sangrà, Pablo

    2015-01-01

    The eruptive phase of a submarine volcano located 2 km away from the southern coast of El Hierro Island started on October 2011. This extraordinary event provoked a dramatic perturbation of the water column. In order to understand and quantify the environmental impacts caused, a regular multidisciplinary monitoring was carried out using remote sensing sensors. In this context, we performed the systematic processing of every MODIS and MERIS and selected high resolution Worldview-2 imagery to provide information on the concentration of a number of biological, physical and chemical parameters. On the other hand, the eruption provided an exceptional source of tracer that allowed the study a variety of oceanographic structures. Specifically, the Canary Islands belong to a very active zone of long-lived eddies. Such structures are usually monitored using sea level anomaly fields. However these products have coarse spatial resolution and they are not suitable to perform submesoscale studies. Thanks to the volcanic tracer, detailed studies were undertaken with ocean colour imagery allowing, using the diffuse attenuation coefficient, to monitor the process of filamentation and axisymmetrization predicted by theoretical studies and numerical modelling. In our work, a novel 2-step segmentation methodology has been developed. The approach incorporates different segmentation algorithms and region growing techniques. In particular, the first step obtains an initial eddy segmentation using thresholding or clustering methods and, next, the fine detail is achieved by the iterative identification of the points to grow and the subsequent application of watershed or thresholding strategies. The methodology has demonstrated an excellent performance and robustness and it has proven to properly capture the eddy and its filaments. PMID:25875193

  15. Segmentation and tracking of anticyclonic eddies during a submarine volcanic eruption using ocean colour imagery.

    PubMed

    Marcello, Javier; Eugenio, Francisco; Estrada-Allis, Sheila; Sangrà, Pablo

    2015-01-01

    The eruptive phase of a submarine volcano located 2 km away from the southern coast of El Hierro Island started on October 2011. This extraordinary event provoked a dramatic perturbation of the water column. In order to understand and quantify the environmental impacts caused, a regular multidisciplinary monitoring was carried out using remote sensing sensors. In this context, we performed the systematic processing of every MODIS and MERIS and selected high resolution Worldview-2 imagery to provide information on the concentration of a number of biological, physical and chemical parameters. On the other hand, the eruption provided an exceptional source of tracer that allowed the study a variety of oceanographic structures. Specifically, the Canary Islands belong to a very active zone of long-lived eddies. Such structures are usually monitored using sea level anomaly fields. However these products have coarse spatial resolution and they are not suitable to perform submesoscale studies. Thanks to the volcanic tracer, detailed studies were undertaken with ocean colour imagery allowing, using the diffuse attenuation coefficient, to monitor the process of filamentation and axisymmetrization predicted by theoretical studies and numerical modelling. In our work, a novel 2-step segmentation methodology has been developed. The approach incorporates different segmentation algorithms and region growing techniques. In particular, the first step obtains an initial eddy segmentation using thresholding or clustering methods and, next, the fine detail is achieved by the iterative identification of the points to grow and the subsequent application of watershed or thresholding strategies. The methodology has demonstrated an excellent performance and robustness and it has proven to properly capture the eddy and its filaments. PMID:25875193

  16. Eddy surface properties and propagation at Southern Hemisphere western boundary current systems

    NASA Astrophysics Data System (ADS)

    Pilo, G. S.; Mata, M. M.; Azevedo, J. L. L.

    2015-08-01

    Oceanic eddies exist throughout the world oceans, but are more energetic when associated with western boundary currents (WBC) systems. In these regions, eddies play an important role in mixing and energy exchange. Therefore, it is important to quantify and qualify eddies associated with these systems. This is particularly true for the Southern Hemisphere WBC system where only few eddy censuses have been performed to date. In these systems, important aspects of the local eddy population are still unknown, like their spatial distribution and propagation patterns. Moreover, the understanding of these patterns helps to establish monitoring programs and to gain insight in how eddies would affect local mixing. Here, we use a global eddy data set to qualify eddies based on their surface characteristics in the Agulhas Current (AC), the Brazil Current (BC) and the East Australian Current (EAC) systems. The analyses reveal that eddy propagation within each system is highly forced by the local mean flow and bathymetry. Large values of eddy amplitude and temporal variability are associated with the BC and EAC retroflections, while small values occur in the centre of the Argentine Basin and in the Tasman Sea. In the AC system, eddy polarity dictates the propagation distance. BC system eddies do not propagate beyond the Argentine Basin, and are advected by the local ocean circulation. EAC system eddies from both polarities cross south of Tasmania but only the anticyclonic ones reach the Great Australian Bight. For all three WBC systems, both cyclonic and anticyclonic eddies present a geographical segregation according to radius size and amplitude. Regions of high eddy kinetic energy are associated with the eddies' mean amplitudes, and not with their densities.

  17. Study of Near-Surface Models in Large-Eddy Simulations of a Neutrally Stratified Atmospheric Boundary Layer

    NASA Technical Reports Server (NTRS)

    Senocak, I.; Ackerman, A. S.; Kirkpatrick, M. P.; Stevens, D. E.; Mansour, N. N.

    2004-01-01

    Large-eddy simulation (LES) is a widely used technique in armospheric modeling research. In LES, large, unsteady, three dimensional structures are resolved and small structures that are not resolved on the computational grid are modeled. A filtering operation is applied to distinguish between resolved and unresolved scales. We present two near-surface models that have found use in atmospheric modeling. We also suggest a simpler eddy viscosity model that adopts Prandtl's mixing length model (Prandtl 1925) in the vicinity of the surface and blends with the dynamic Smagotinsky model (Germano et al, 1991) away from the surface. We evaluate the performance of these surface models by simulating a neutraly stratified atmospheric boundary layer.

  18. MATERIALS AND TECHNIQUES FOR THE LANGUAGE LABORATORY.

    ERIC Educational Resources Information Center

    NAJAM, EDWARD W.

    THE PROCEEDINGS OF THE SECOND ANNUAL INDIANA-PURDUE LANGUAGE LABORATORY CONFERENCE ARE ORGANIZED, AFTER INTRODUCTORY STATEMENTS BY NAJAM AND LARSEN ON CONTEMPORARY TRENDS IN LANGUAGE INSTRUCTION, UNDER THREE GENERAL HEADINGS PLUS APPENDIXES. IN THE FIRST SECTION DEVOTED TO MATERIALS AND TECHNIQUES ARE ARTICLES BY HYER, GARIMALDI, EDDY, AND SMITH…

  19. Nondestructive Testing Eddy Current Basic Principles RQA/M1-5330.12 (V-I).

    ERIC Educational Resources Information Center

    National Aeronautics and Space Administration, Huntsville, AL. George C. Marshall Space Flight Center.

    As one in the series of programmed instruction handbooks, prepared by the U.S. space program, home study material is presented in this volume concerning familiarization and orientation on basic eddy current principles. The subject is presented under the following headings: Basic Eddy Current Concepts, Eddy Current Generation and Distribution,…

  20. A 3D Model for Eddy Current Inspection in Aeronautics: Application to Riveted Structures

    NASA Astrophysics Data System (ADS)

    Paillard, S.; Pichenot, G.; Lambert, M.; Voillaume, H.; Dominguez, N.

    2007-03-01

    Eddy current technique is currently an operational tool used for fastener inspection which is an important issue for the maintenance of aircraft structures. The industry calls for faster, more sensitive and reliable NDT techniques for the detection and characterization of potential flaws nearby rivet. In order to reduce the development time and to optimize the design and the performances assessment of an inspection procedure, the CEA and EADS have started a collaborative work aiming at extending the modeling features of the CIVA non destructive simulation plat-form in order to handle the configuration of a layered planar structure with a rivet and an embedded flaw nearby. Therefore, an approach based on the Volume Integral Method using the Green dyadic formalism which greatly increases computation efficiency has been developed. The first step, modeling the rivet without flaw as a hole in a multi-stratified structure, has been reached and validated in several configurations with experimental data.