Science.gov

Sample records for air gap flux

  1. Direct control of air gap flux in permanent magnet machines

    DOEpatents

    Hsu, John S.

    2000-01-01

    A method and apparatus for field weakening in PM machines uses field weakening coils (35, 44, 45, 71, 72) to produce flux in one or more stators (34, 49, 63, 64), including a flux which counters flux normally produced in air gaps between the stator(s) (34, 49, 63, 64) and the rotor (20, 21, 41, 61) which carries the PM poles. Several modes of operation are introduced depending on the magnitude and polarity of current in the field weakening coils (35, 44, 45, 71, 72). The invention is particularly useful for, but not limited to, the electric vehicle drives and PM generators.

  2. Detection of air-gap eccentricity and broken-rotor bar conditions in a squirrel-cage induction motor using the radial flux sensor

    SciTech Connect

    Hwang, Don-Ha; Woo, Byung-Chul; Sun, Jong-Ho; Kang, Dong-Sik; Han, Sang-Bo; Kim, Byung-Kuk; Cho, Youn-Hyun

    2008-04-01

    A new method for detecting eccentricity and broken rotor bar conditions in a squirrel-cage induction motor is proposed. Air-gap flux variation analysis is done using search coils, which are inserted at stator slots. Using this method, the leakage flux in radial direction can be directly detected. Using finite element method, the air-gap flux variation is accurately modeled and analyzed. From the results of the simulation, a motor under normal condition shows maximum magnetic flux density of 1.3 T. On the other hand, the eccentric air-gap condition displays about 1.1 T at 60 deg. and 1.6 T at 240 deg. A difference of flux density is 0.5 T in the abnormal condition, whereas no difference is detected in the normal motor. In the broken rotor bar conditions, the flux densities at 65 deg. and 155 deg. are about 0.4 T and 0.8 T, respectively. These simulation results are coincided with those of experiment. Consequently, the measurement of the magnetic flux at air gap is one of effective ways to discriminate the faulted conditions of the eccentricity and broken rotor bars.

  3. Detection of air-gap eccentricity and broken-rotor bar conditions in a squirrel-cage induction motor using the radial flux sensor

    NASA Astrophysics Data System (ADS)

    Hwang, Don-Ha; Han, Sang-Bo; Woo, Byung-Chul; Sun, Jong-Ho; Kang, Dong-Sik; Kim, Byung-Kuk; Cho, Youn-Hyun

    2008-04-01

    A new method for detecting eccentricity and broken rotor bar conditions in a squirrel-cage induction motor is proposed. Air-gap flux variation analysis is done using search coils, which are inserted at stator slots. Using this method, the leakage flux in radial direction can be directly detected. Using finite element method, the air-gap flux variation is accurately modeled and analyzed. From the results of the simulation, a motor under normal condition shows maximum magnetic flux density of 1.3T. On the other hand, the eccentric air-gap condition displays about 1.1T at 60° and 1.6T at 240°. A difference of flux density is 0.5T in the abnormal condition, whereas no difference is detected in the normal motor. In the broken rotor bar conditions, the flux densities at 65° and 155° are about 0.4 T and 0.8T, respectively. These simulation results are coincided with those of experiment. Consequently, the measurement of the magnetic flux at air gap is one of effective ways to discriminate the faulted conditions of the eccentricity and broken rotor bars.

  4. Air-gap heterostructures

    SciTech Connect

    Heyn, Ch.; Schmidt, M.; Schwaiger, S.; Stemmann, A.; Mendach, S.; Hansen, W.

    2011-01-17

    We demonstrate the fabrication of thin GaAs layers which quasi hover above the underlying GaAs substrate. The hovering layers have a perfect epitaxial relationship to the substrate crystal lattice and are connected to the substrate surface only by lattice matched nanopillars of low density. These air-gap heterostructures are created by combining in situ molecular beam epitaxy compatible self-assembled droplet-etching and ex situ selective wet-chemical etching.

  5. [Spatiotempaoral distribution patterns of photosynthetic photon flux density, air temperature, and relative air humidity in forest gap of Pinus koraiensis-dominated broadleaved mixed forest in Xi-ao Xing' an Mountains].

    PubMed

    Li, Meng; Duan, Wen-biao; Chen, Li-xin

    2009-12-01

    A continuous measurement of photosynthetic photon flux density (PPFD), air temperature, and relative air humidity was made in the forest gap in primary Pinus koraiensis-dominated broadleaved mixed forest in Xiao Xing' an Mountains to compare the spatiotemporal distribution patterns of the parameters. The diurnal maximum PPFD in the forest gap appeared between 11:00 and 13:00 on sunny and overcast days. On sunny days, the maximum PPFD during various time periods did not locate in fixed locations, the diurnal maximum PPFD occurred in the canopy edge of northern part of the gap; while on overcast days, it always occurred in the center of the gap. The mean monthly PPFD in the gap was the highest in June and the lowest in September, with the largest range observed in July. The maximum air temperature happened between 9:00 and 15:00 on sunny days, between 15:00 and 19:00 on overcast days, the locations were 8 m in the southern part of gap center both on sunny and overcast days. From 5:00 to 9:00, the air temperature at measured positions in the gap was higher on overcast days than on sunny days; but from 9:00 to 19:00, it was opposite. The mean monthly air temperature was the highest in June, and the lowest in September. The maximum relative humidity appeared between 5:00 and 9:00 on sunny and overcast days, and occurred in the canopy border of western part of the gap, with the relative air humidity on overcast days being always higher than that on sunny days. The mean monthly relative humidity was the highest in July, and the lowest in June. The heterogeneity of PPFD was higher on sunny days than on overcast days, but the heterogeneities of air temperature and relative humidity were not obvious. The maximum PPFD, air temperature, and relative humidity were not located in the same positions among different months during growing season. For mean monthly PPFD and air temperature, their variation gradient was higher in and around the center of gap; while for mean monthly

  6. 30 CFR 56.6603 - Air gap.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Air gap. 56.6603 Section 56.6603 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND... § 56.6603 Air gap. At least a 15-foot air gap shall be provided between the blasting circuit and...

  7. 30 CFR 56.6603 - Air gap.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Air gap. 56.6603 Section 56.6603 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND... § 56.6603 Air gap. At least a 15-foot air gap shall be provided between the blasting circuit and...

  8. 30 CFR 57.6603 - Air gap.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Air gap. 57.6603 Section 57.6603 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND...-Surface and Underground § 57.6603 Air gap. At least a 15-foot air gap shall be provided between...

  9. Permanent-magnet-less machine having an enclosed air gap

    DOEpatents

    Hsu, John S.

    2013-03-05

    A permanent magnet-less, brushless synchronous system includes a stator that generates a magnetic rotating field when sourced by an alternating current. An uncluttered rotor disposed within the magnetic rotating field is spaced apart from the stator to form an air gap relative to an axis of rotation. A stationary excitation core spaced apart from the uncluttered rotor by an axial air gap and a radial air gap substantially encloses the stationary excitation core. Some permanent magnet-less, brushless synchronous systems include stator core gaps to reduce axial flux flow. Some permanent magnet-less, brushless synchronous systems include an uncluttered rotor coupled to outer laminations. The quadrature-axis inductance may be increased in some synchronous systems. Some synchronous systems convert energy such as mechanical energy into electrical energy (e.g., a generator); other synchronous systems may convert any form of energy into mechanical energy (e.g., a motor).

  10. Permanent-magnet-less machine having an enclosed air gap

    DOEpatents

    Hsu, John S.

    2012-02-07

    A permanent magnet-less, brushless synchronous system includes a stator that generates a magnetic rotating field when sourced by an alternating current. An uncluttered rotor disposed within the magnetic rotating field is spaced apart from the stator to form an air gap relative to an axis of rotation. A stationary excitation core spaced apart from the uncluttered rotor by an axial air gap and a radial air gap substantially encloses the stationary excitation core. Some permanent magnet-less, brushless synchronous systems include stator core gaps to reduce axial flux flow. Some permanent magnet-less, brushless synchronous systems include an uncluttered rotor coupled to outer laminations. The quadrature-axis inductance may be increased in some synchronous systems. Some synchronous systems convert energy such as mechanical energy into electrical energy (e.g., a generator); other synchronous systems may convert any form of energy into mechanical energy (e.g., a motor).

  11. Engine piston having an insulating air gap

    DOEpatents

    Jarrett, Mark Wayne; Hunold,Brent Michael

    2010-02-02

    A piston for an internal combustion engine has an upper crown with a top and a bottom surface, and a lower crown with a top and a bottom surface. The upper crown and the lower crown are fixedly attached to each other using welds, with the bottom surface of the upper crown and the top surface of the lower crown forming a mating surface. The piston also has at least one centrally located air gap formed on the mating surface. The air gap is sealed to prevent substantial airflow into or out of the air gap.

  12. Theoretical and experimental studies on air gap membrane distillation

    NASA Astrophysics Data System (ADS)

    Liu, G. L.; Zhu, C.; Cheung, C. S.; Leung, C. W.

    Air gap membrane distillation (AGMD) is an innovative membrane separation technique for pure water extraction from aqueous solutions. In this study, both theoretical and experimental investigations are carried out on AGMD of different aqueous solutions, namely, tap water, salted water, dyed solutions, acid solutions, and alkali solutions. A simple mechanistic model of heat and mass transfer associated with AGMD is developed. Simple relationships of permeate flux, total heating or cooling load and thermal efficiency of AGMD with respect to the membrane distillation temperature difference are obtained. Effects of solution concentration and the width of the air gap in AGMD are analyzed. In the experimental study, the experiments were conducted using 1m PTFE membrane with a membrane distillation temperature difference up to 55∘C. The AGMD system yields a permeate flux of pure water of up to 28kg/m2h. Direct comparison of the experimental results with the proposed modeling predictions shows a fairly good match.

  13. Spatial Scale Gaps of Turbulent Heat Fluxes in Arctic Tundra

    NASA Astrophysics Data System (ADS)

    Fochesatto, G. J.; Gruber, M. A.; Cristóbal-Rosselló, J.; Edgar, C.; Kane, D. L.

    2013-12-01

    Large-area averaged turbulent fluxes of scalars (heat and carbon) play an important role in climate and ecosystem models by resolving the scale-gap closure defining top-down and bottom-up scaling schemes. Large Aperture Scintillometer (LAS) measurement of the refractive index structure function (CN2) allows for indirect retrieval of area-averaged (>km2) atmospheric boundary layer sensible heat fluxes. In this work we report observations of LAS in Arctic tundra at Imnavait Creek Basin. LAS-derived fluxes are compared to more localized measurements of heat fluxes obtained by an eddy-covariance (EC) system distributed across the basin. This article discusses the divergence observed in the temporal series of LAS-fluxes in comparison to spatially distributed measurements of EC-fluxes. The comparison stresses the role of the Arctic ABL structure, terrain-flow characteristics and radiative fluxes in the overall spatial representation of fluxes.

  14. 30 CFR 56.6603 - Air gap.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Air gap. 56.6603 Section 56.6603 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-SURFACE METAL AND NONMETAL MINES Explosives Extraneous...

  15. 30 CFR 56.6603 - Air gap.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Air gap. 56.6603 Section 56.6603 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-SURFACE METAL AND NONMETAL MINES Explosives Extraneous...

  16. 30 CFR 56.6603 - Air gap.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Air gap. 56.6603 Section 56.6603 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-SURFACE METAL AND NONMETAL MINES Explosives Extraneous...

  17. 30 CFR 57.6603 - Air gap.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Air gap. 57.6603 Section 57.6603 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND NONMETAL MINES Explosives Extraneous...

  18. 30 CFR 57.6603 - Air gap.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Air gap. 57.6603 Section 57.6603 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND NONMETAL MINES Explosives Extraneous...

  19. 30 CFR 57.6603 - Air gap.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Air gap. 57.6603 Section 57.6603 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND NONMETAL MINES Explosives Extraneous...

  20. 30 CFR 57.6603 - Air gap.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Air gap. 57.6603 Section 57.6603 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND NONMETAL MINES Explosives Extraneous...

  1. Impact of flux gap upon dynamic resistance of a rotating HTS flux pump

    NASA Astrophysics Data System (ADS)

    Jiang, Zhenan; Bumby, Chris W.; Badcock, Rodney A.; Sung, Hae-Jin; Long, Nicholas J.; Amemiya, Naoyuki

    2015-11-01

    HTS flux pumps enable superconducting currents to be directly injected into a magnet coil without the requirement for thermally inefficient current leads. Here, we present results from an experimental mechanically rotating HTS flux pump employing a coated-conductor stator and operated at 77 K. We show the effect of varying the size of the flux gap between the rotor magnets and coated conductor stator from 1 to 7.5 mm. This leads to a corresponding change in the peak applied perpendicular magnetic field at the stator from approximately 350 to 50 mT. We observe that our experimental device ceases to maintain a measurable output at flux gaps above 7.5 mm, which we attribute to the presence of screening currents in the stator wire. We show that our mechanically rotating flux pump is well described by a simple circuit model which enables the output performance to be described using two simple parameters, the open-circuit voltage V oc and the internal resistance, R d. Both of these parameters are found to be directly proportional to magnet-crossing frequency and decrease with increasing flux gap. We show that the trend in R d can be understood by considering the dynamic resistance experienced at the stator due to the oscillating amplitude of the applied rotor field. We adopt a literature model for the dynamic resistance within our coated-conductor stator and show that this gives good agreement with the experimentally measured internal resistance of our flux pump.

  2. Tunable optofluidic dye laser with integrated air-gap etalon

    NASA Astrophysics Data System (ADS)

    Song, Wuzhou; Vasdekis, Andreas E.; Psaltis, Demetri

    2010-11-01

    In this work we demonstrate an integrated air-gap etalon that enables single wavelength operation and tuning ability for optofluidic dye laser. The integrated elastomeric air-gap etalon is controlled by air pressure. The chip was fabricated with polydimethylsiloxane (PDMS) via replica molding. It comprises a liquid waveguide and micro-scale air-gap mirrors providing the feedback. The lasing wavelength is chosen by the interference between two parallel PDMS-air interfaces inside the internal tunable air-gap etalon, of which pneumatic tuning can be realized by inflating the air-gap etalon with compressed air. This dye laser exhibits a pumping threshold of 1.6 μJ/pulse, a lasing linewidth of 3 nm and a tuning range of 14 nm.

  3. Air Gap Effects in LX-17

    SciTech Connect

    Souers, P C; Ault, S; Avara, R; Bahl, K L; Boat, R; Cunningham, B; Gidding, D; Janzen, J; Kuklo, D; Lee, R; Lauderbach, L; Weingart, W C; Wu, B; Winer, K

    2005-09-26

    Three experiments done over twenty years on gaps in LX-17 are reported. For the detonation front moving parallel to the gaps, jets of gas products were seen coming from the gaps at velocities greater than the detonation velocity. A case can be made that the jet velocity increased with gap thickness but the data is scattered. For the detonation front moving transverse to the gap, time delays were seen. The delays roughly increase with gap width, going from 0-70 ns at 'zero gap' to around 300 ns at 0.5-1 mm gap. Larger gaps of up to 6 mm width almost certainly stopped the detonation, but this was not proved. Real-time resolution of the parallel jets and determination of the actual re-detonation or failure in the transverse case needs to be done in future experiments.

  4. Transmission properties of frequency selective structures with air gaps

    NASA Astrophysics Data System (ADS)

    Meng, Zhi-Jun; Wang, Li-Feng; Lü, Ming-Yun; Wu, Zhe

    2010-12-01

    The transmission properties of compound frequency selective structures with dielectric slab and air gaps were investigated by computation and experimentation. Mechanism analyses were also carried out. Results show that the air gaps have a distinct influence on the transmission properties. Resonant frequency of the structure would increase rapidly when the air gap appears. After the gap gets larger to a specific value, generally 1/5 wavelength corresponding to the resonant frequency, the transmission properties would change periodically with the gap thickness. The change of transmission properties in one period has a close relationship with the dielectric thickness. These results provide a new method for designing a bandpass radome of large incidence angle and low loss with the concept of stealth shield radome.

  5. Eddy Covariance Measurements Over a Maize Field: The Contribution of Minor Flux Terms to the Energy Balance Gap

    NASA Astrophysics Data System (ADS)

    Smidt, J.; Ingwersen, J.; Streck, T.

    2015-12-01

    The lack of energy balance closure is a long-standing problem in eddy covariance (EC) measurements. The energy balance equation is defined as Rn - G = H + λE, where Rn is net radiation, G is the ground heat flux, H is the sensible heat flux and λE is the latent heat flux. In most cases of energy imbalance, either Rn is overestimated or the ground heat and turbulent fluxes are underestimated. Multiple studies have shown that calculations, incorrect instrument installation/calibration and measurement errors alone do not entirely account for this imbalance. Rather, research is now focused on previously neglected sources of heat storage in the soil, biomass and air beneath the EC station. This project examined the potential of five "minor flux terms" - soil heat storage, biomass heat storage, energy consumption by photosynthesis, air heat storage and atmospheric moisture change, to further close the energy balance gap. Eddy covariance measurements were conducted at a maize (Zea mays) field in southwest Germany during summer 2014. Soil heat storage was measured for six weeks at 11 sites around the field footprint. Biomass and air heat storage were measured for six subsequent weeks at seven sites around the field footprint. Energy consumption by photosynthesis was calculated using the CO2 flux data. Evapotranspiration was calculated using the water balance method and then compared to the flux data processed with three post-closure methods: the sensible heat flux, the latent heat flux and the Bowen ratio post-closure methods. An energy balance closure of 66% was achieved by the EC station measurements over the entire investigation period. During the soil heat flux campaign, EC station closure was 74.1%, and the field footprint soil heat storage contributed 3.3% additional closure. During the second minor flux term measurement period, closure with the EC station data was 91%. Biomass heat storage resulted in 1.1% additional closure, the photosynthesis flux closed the gap

  6. Water desalination by air-gap membrane distillation using meltblown polypropylene nanofiber membrane

    NASA Astrophysics Data System (ADS)

    Rosalam, S.; Chiam, C. K.; Widyaparamitha, S.; Chang, Y. W.; Lee, C. A.

    2016-06-01

    This paper presents a study of air gap membrane distillation (AGMD) using meltblown polypropylene (PP) nanofiber membrane to produce fresh water via desalination process. PP nanofiber membranes with the effective area 0.17 m2 are tested with NaCl solutions (0.5 - 4.0 wt.%) and seawater as the feed solutions (9400 - 64800 μS/cm) in a tubular membrane module. Results show that the flux decreases with increasing the membrane thickness from 547 to 784 μm. The flux increases with the feed flow rate and temperature difference across the membrane. The feed concentration affects the flux insignificantly. The AGMD system can reject the salts at least 96%. Water vapor permeation rate is relatively higher than solute permeation rate resulting in the conductivity value of permeate decreases when the corresponding flux increases. The AGMD system produces the fresh water (200 - 1520 μS/cm) that is suitable for drinking, fisheries or irrigation.

  7. Surface Flux Modeling for Air Quality Applications

    EPA Science Inventory

    For many gasses and aerosols, dry deposition is an important sink of atmospheric mass. Dry deposition fluxes are also important sources of pollutants to terrestrial and aquatic ecosystems. The surface fluxes of some gases, such as ammonia, mercury, and certain volatile organic c...

  8. The Air Gap Phenomenon in Children's Landscape Drawings.

    ERIC Educational Resources Information Center

    Hargreaves, David J.; And Others

    1981-01-01

    These studies confirm the view that the "air gap" phenomenon, which refers to the area that remains when ground and sky lines are constructed at the bottom and top of a drawing, is commonly found in the free drawings of middle and later childhood, but that it is readily abandoned when task demands are modified accordingly. (Author/DB)

  9. 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

  10. Gap-dependent transitions of atmospheric microplasma in open air

    SciTech Connect

    Chu, Hong-Yu; Huang, Bo-Shiun

    2011-04-15

    We report on the gap dependence of the planar atmospheric microplasma in air. We investigate the transitions of the dielectric barrier discharge in open air, including the random walk filaments (plasma columns), localized filaments, stochastic filaments, and diffuse discharge. A star-shaped filamentary discharge pattern is observed after the formation of the localized filaments. The liquid drops found on the dielectric surface further become a confining pattern for star-shaped discharge. We also demonstrate the applications of the insulating pattern for the use of the plasma display in open air by the handwritten characters with UV adhesive.

  11. An ultrasonic air pump using an acoustic traveling wave along a small air gap.

    PubMed

    Koyama, Daisuke; Wada, Yuji; Nakamura, Kentaro; Nishikawa, Masato; Nakagawa, Tatsuyuki; Kihara, Hitoshi

    2010-01-01

    An ultrasonic air pump that uses a traveling wave along a small air gap between a bending vibrator and a reflector is discussed. The authors investigate ultrasonic air pumps that make use of bending vibrators and reflectors and confirm that air can be induced to flow by generating an asymmetric acoustic standing wave along an air gap. In this paper, we proposed a novel ultrasonic air pump in which a traveling wave along an air gap induces acoustic streaming and achieves one-way airflow. Two new reflector configurations, stepped and tapered, were designed and used to generate traveling waves. To predict airflow generation, sound pressure distribution in the air gap was calculated by means of finite element analysis (FEA). As a preliminary step, 2 FEA models were compared: one piezoelectric-structure-acoustic model and one piezoelectric- structure-fluid model, which included the viscosity effect of the fluid. The sound pressure distribution in the air gap, including fluid viscosity, was calculated by the FEA because it is expected to be dominant and thus have a strong effect on the sound pressure field in such a thin fluid layer. Based on the FEA results of the stepped and the tapered reflectors, it was determined that acoustic traveling waves could propagate along the gaps. Experiments were carried out with the designed bending vibrator and the reflectors. The acoustic fields in the air gap were measured via a fiber optic probe, and it was determined that the sound pressure and the phase distribution tendencies corresponded well with the results computed by FEA. Through our experiments, one-way airflow generation, in the same direction of the traveling wave and with the maximum flow velocity of 5.6 cm/s, was achieved.

  12. Lowering of intralevel capacitance using air gap structures

    SciTech Connect

    Fleming, J.G.; Roherty-Osmun, E.; Farino, A.J.

    1996-11-01

    Interconnect delays, arising in part from intralevel capacitance, are one of the limiting factors in the performance of advanced integrated circuits. In addition, the problem of filling the spaces between neighboring metal lines with an insulator is becoming increasingly severe as aspect ratios increase. We address these problems by intentionally creating a air gap between closely spaced metal lines. The ends of the air gap and reentrant features are then sealed using a spin on dielectric. The entire structure is then capped with silicon dioxide and planarized . Simple modeling of mechanical test structures on silicon predicts an equivalent dielectric constant of 1.9 on features similar to those expected for 0.25 micron technologies. Metal to metal test structures fabricated in a 0.5 micron CMOS technology show that the process can be readily integrated with chemical mechanical polishing and current standard CMOS processes.

  13. Problems in determining air-surface fluxes for climate studies

    SciTech Connect

    Brown, R.A.

    1994-12-31

    The modelling of global air-surface fluxes for climate studies has many problems. Data are sparse. Classical parameterization formulas have received limited verification over the ocean, the pack ice and in many remote regions with various surface characteristics. Nevertheless, surface layer models and bulk parameterization schemes often are adequate for flux calculations based on mean flow parameters. The real problems then lie in the quality of input data for the flux calculations. In general circulation models (GCMs), the surface winds and temperatures may have large errors. These have been shown to be significant to long-term fluxes.

  14. On the Global Oxygen Anomaly and Air-Sea Flux

    NASA Technical Reports Server (NTRS)

    Garcia, Hernan E.; Keeling, Ralph F.

    2001-01-01

    A new climatology of monthly air-sea oxygen fluxes throughout the ice-free surface global ocean is presented. The climatology is based on weighted linear least squares regressions using heat flux monthly anomalies for spatial and temporal interpolation of historical O2 data. The seasonal oceanic variations show that the tropical belt (20 S - 20 N) is characterized by relatively small air-sea fluxes when compared to the middle to high latitudes (40 deg - 70 deg). The largest and lowest seasonal fluxes occur during summer and winter in both hemispheres. By means of an atmospheric transport model we show that our climatology is in better agreement with the observed amplitude and phasing of the variations in atmospheric O2/N2 ratios because of seasonal air-sea exchanges at baseline stations in the Pacific Ocean than with previous air-sea O2 climatologies. Our study indicates that the component of the air-sea O2 flux that correlates with heat flux dominates the large-scale air-sea O2 exchange on seasonal timescales. The contribution of each major oceanic basin to the atmospheric observations is described. The seasonal net thermal (SNO(sub T)) and biological (SNO(sub B)) outgassing components of the flux are examined in relation to latitudinal bands, basin-wide, and hemispheric contributions. The Southern Hemisphere's SNO(sub B) (approximately 0.26 Pmol) and SNO(sub T) (approximately 0.29 Pmol) values are larger than the Northern Hemisphere's SNO(sub B) (approximately 0.15 Pmol) and SNO(sub T) (approximately 0.16 Pmol) values (1 Pmol = 10(exp 15) mol). We estimate a global extratropical carbon new production during the outgassing season of 3.7 Pg C (1 Pg = 10(exp 15) g), lower than previous estimates with air-sea O2 climatologies.

  15. Study of Various Slanted Air-Gap Structures of Interior Permanent Magnet Synchronous Motor with Brushless Field Excitation

    SciTech Connect

    Tolbert, Leon M; Lee, Seong T

    2010-01-01

    This paper shows how to maximize the effect of the slanted air-gap structure of an interior permanent magnet synchronous motor with brushless field excitation (BFE) for application in a hybrid electric vehicle. The BFE structure offers high torque density at low speed and weakened flux at high speed. The unique slanted air-gap is intended to increase the output torque of the machine as well as to maximize the ratio of the back-emf of a machine that is controllable by BFE. This irregularly shaped air-gap makes a flux barrier along the d-axis flux path and decreases the d-axis inductance; as a result, the reluctance torque of the machine is much higher than a uniform air-gap machine, and so is the output torque. Also, the machine achieves a higher ratio of the magnitude of controllable back-emf. The determination of the slanted shape was performed by using magnetic equivalent circuit analysis and finite element analysis (FEA).

  16. Application of the Hilbert-Huang Transform to the Estimation of Air-Sea Turbulent Fluxes

    NASA Astrophysics Data System (ADS)

    Wang, Juanjuan; Song, Jinbao; Huang, Yansong; Fan, Conghui

    2013-06-01

    The Hilbert-Huang transform (HHT) is applied to analyzing the turbulent time series obtained within the atmospheric boundary layer over the ocean. A method based on the HHT is introduced to reduce the influence of non-turbulent motions on the eddy-covariance based flux by removing non-turbulent modes from the time series. The scale dependence of the flux is examined and a gap mode is identified to distinguish between turbulent modes and non-turbulent modes. To examine the effectiveness of this method it is compared with three conventional methods (block average, moving-window average, and multi-resolution decomposition). The data used are from three sonic anemometers installed on a moored buoy at about 6, 4 and 2.7 m height above the sea surface. For each method, along-wind and cross-wind momentum fluxes and sensible heat fluxes at the three heights are calculated. According to the assumption of a constant-flux layer, there should be no significant difference between the fluxes at the three heights. The results show that the fluxes calculated using HHT exhibit a smaller difference and higher correlation than the other methods. These results support the successful application of HHT to the estimation of air-sea turbulent fluxes.

  17. Evaluation and gap-filling of soil NO flux dataset measured at a Hungarian semi-arid grassland

    NASA Astrophysics Data System (ADS)

    Horvath, Laszlo; Hidy, Dora; Weidinger, Tamas

    2015-04-01

    An Integrated Project ÉCLAIRE (http://www.eclaire-fp7.eu/) started in 2011 among others to study the effect of climate change on air pollution impacts. One of the main measurement tasks of this project was the continuous monitoring of soil NO emission at different kinds of lands (forest, arable, grass). Among the tree grass stations Bugacpuszta (central part of Hungary between the Danube and the Tisza) was selected to monitor and report soil NO fluxes continuously for 17 months on hourly basis. The climate is semi-arid temperate continental, the mean annual temperature is 10.7 ° C, and the average annual precipitation is around 550 mm. Nitric oxide soil emission flux was measured by 2-2 parallel manual and auto dynamic chambers on hourly basis above a semi-arid, sandy grassland between August 2012 and January 2014. Each chamber was sampled for 10 minutes at a flow rate of 2 L min-1 in sequence each hour all together for 40 minutes; in the remaining 20 minutes concentration gradients were measured by a mast at two heights. Soil temperature and moisture were measured a few meters apart from the chambers. A computer controlled valve system was switched the different channels in turn. The output concentrations of nitric oxide and ozone were measured by HORIBA gas monitors through Teflon tubing. Micrometeorological measurements (energy budget components, CO2 and O3 fluxes) were also provided. The initial NO flux datasets covered 43-85% of time period depending on chambers. Measured flux data ranges within 0-6 nmol m-2 s-1. We applied a gap-filling method based on multivariable analysis (Sigma Plot) combined with maximum likelihood method using the soil temperature and moisture data. Trend of gap-filled flux dataset shows large peaks mostly in summer and early fall. When soil parameters are far from the optimum (dry, warm conditions) the fluxes are negligible. Application of manual chambers closed for longer period results in substantial positive bias in flux

  18. Gap-filling of flux measurements over a heterogeneous urban landscape

    NASA Astrophysics Data System (ADS)

    Menzer, O.; McFadden, J.

    2012-12-01

    A small, but growing, number of urban flux towers measure surface-atmospheric exchanges of energy, water, and greenhouse gases by the eddy covariance method. Imputation of gaps in these measurements caused by low turbulence conditions and system failures is essential for obtaining annual sums of CO2 exchange and evaporation. Yet most gap-filling methods were designed for natural measurement sites such as forests and grasslands. In the urban environment, however, the assumptions on which those approaches are based are violated and well known temperature or light response models are not applicable because of urban footprint heterogeneity and localized CO2 emissions. Observation-based methods of machine learning can reveal intrinsic mechanisms by using inputs such as wind direction, footprint size, and continuous traffic data, making gap-filling results more accurate. Here, we report preliminary gap-filling results using such empirical approaches for >3 years of flux measurements from the KUOM tall tower in a suburban neighborhood of Minneapolis, Minnesota, USA. We also ran one of the most common gap-filling methods that has been used for natural systems as a baseline or null model. We found that CO2 and water vapor fluxes from the urban landscape showed higher variability than those from a nearby turfgrass lawn, in which fluxes closely followed environmental drivers of light and temperature. Higher variability was found in NEE measurements as compared to LE, due to the relatively greater heterogeneity of sources and sinks that influenced CO2 exchange in the urban landscape.

  19. Advances in Air-Sea Flux Measurement by Eddy Correlation

    NASA Astrophysics Data System (ADS)

    Blomquist, Byron W.; Huebert, Barry J.; Fairall, Christopher W.; Bariteau, Ludovic; Edson, James B.; Hare, Jeffrey E.; McGillis, Wade R.

    2014-09-01

    Eddy-correlation measurements of the oceanic flux are useful for the development and validation of air-sea gas exchange models and for analysis of the marine carbon cycle. Results from more than a decade of published work and from two recent field programs illustrate the principal interferences from water vapour and motion, demonstrating experimental approaches for improving measurement precision and accuracy. Water vapour cross-sensitivity is the greatest source of error for flux measurements using infrared gas analyzers, often leading to a ten-fold bias in the measured flux. Much of this error is not related to optical contamination, as previously supposed. While various correction schemes have been demonstrated, the use of an air dryer and closed-path analyzer is the most effective way to eliminate this interference. This approach also obviates density corrections described by Webb et al. (Q J R Meteorol 106:85-100, 1980). Signal lag and frequency response are a concern with closed-path systems, but periodic gas pulses at the inlet tip provide for precise determination of lag time and frequency attenuation. Flux attenuation corrections are shown to be 5 % for a cavity ring-down analyzer (CRDS) and dryer with a 60-m inlet line. The estimated flux detection limit for the CRDS analyzer and dryer is a factor of ten better than for IRGAs sampling moist air. While ship-motion interference is apparent with all analyzers tested in this study, decorrelation or regression methods are effective in removing most of this bias from IRGA measurements and may also be applicable to the CRDS.

  20. Development of a highly efficient brushless dc motor utilizing both radial and axial air gaps

    NASA Astrophysics Data System (ADS)

    Kang, K. J.; Jang, G. H.; Sung, S. J.; Chang, J. H.

    2012-04-01

    This research proposes an effective structure for a brushless dc motor utilizing both radial and axial air gaps. The proposed motor generates torque in both the radial and axial air gaps, while the conventional motor generates torque only in the radial air gap. The proposed motor was optimized to minimize the electromagnetic loss of the motor to increase the effective air gap length and fill-factor of the coil while decreasing the saturation of the core at the same time. The electromagnetic loss was reduced by 35% in comparison with a conventional motor.

  1. The Luther-Emery liquid: Spin gap and anomalous flux period

    NASA Astrophysics Data System (ADS)

    Seidel, Alexander; Lee, Dung-Hai

    2005-01-01

    We study the dependence of the ground state energy on an applied Aharonov-Bohm flux Φ for the Luttinger model with large momentum scattering. Employing the method of finite size bosonization, we show that for systems with a spin gap but with gapless charge degrees of freedom, the ground state energy has an exact period of hc/2e , i.e., half a flux quantum, in the limit of large system size L . Finite size corrections are found to vanish exponentially in L . This behavior is contrasted to that of the spin gapless case, for both even and odd particle number. Generalizations to finite temperature are also discussed.

  2. Controlled heat flux measurement across a closing nanoscale gap and its comparison to theory

    NASA Astrophysics Data System (ADS)

    Ma, Y.; Ghafari, A.; Budaev, B. V.; Bogy, D. B.

    2016-05-01

    We present here a controlled measurement of heat flux across a closing gap that is initially less than 10 nm wide between two solid surfaces at different temperatures. The measured heat transfer is compared with our published theoretical analyses of this phenomenon that show thermal radiation dominates the heat transfer for gaps wider than about 1-2 nm, but phonon conduction dominates between 1 and 2 nm and contact. The experiments employ a thermal actuator mounted on a rocking base block for coarse positioning that supplies Joule heating to an embedded element to cause thermal expansion of a localized region for less than 10 nm spacing control, together with an embedded near-surface resistive temperature sensor to measure its temperature change due to the heat flux across the gap. The measured results are in general agreement with the theoretical predictions, and they also agree with common sense expectations. This paper not only shows nano-scale heat transfer measurement across a closing gap, it also lends additional strong support to the validity of the referenced theoretical developments. The proposed experimental approach can provide support to design of future devices for nano-scale heat transfer measurement.

  3. Thickness and air gap measurement of assembled IR objectives

    NASA Astrophysics Data System (ADS)

    Lueerss, B.; Langehanenberg, P.

    2015-05-01

    A growing number of applications like surveillance, thermography, or automotive demand for infrared imaging systems. Their imaging performance is significantly influenced by the alignment of the individual lens elements. Besides the lateral orientation of lenses, the air spacing between the lenses is a crucial parameter. Because of restricted mechanical accessibility within an assembled objective, a non-contact technique is required for the testing of these parameters. So far commercial measurement systems were not available for testing of IR objectives since many materials used for infrared imaging are non-transparent at wavelengths below 2 μm. We herewith present a time-domain low coherent interferometer capable of measuring any kind of infrared material (e.g., Ge, Si, etc.) as well as VIS materials. The fiber-optic set-up is based on a Michelson-Interferometer in which the light from a broadband super-luminescent diode is split into a reference arm with a variable optical delay and a measurement arm where the sample is placed. On a photo detector, the reflected signals from both arms are superimposed and recorded as a function of the variable optical path. Whenever the group delay difference is zero, a coherence peak occurs and the relative lens' surface distances are derived from the optical delay. In order to penetrate IR materials, the instrument operates at 2.2 μm. The set-up allows the contactless determination of thicknesses and air gaps inside of assembled infrared objective lenses with accuracy in the micron range. It therefore is a tool for the precise manufacturing or quality control.

  4. Use of air gap structures to lower intralevel capacitance

    SciTech Connect

    Fleming, J.G.; Roherty-Osmun, E.

    1997-03-01

    Interconnect delays, arising in part from intralevel capacitance, are one of the factors limiting the performance of advanced circuits. In addition, the problem of filling the spaces between neighboring metal lines with an insulator is becoming increasingly acute as aspect ratios increase. We address these problems simultaneously by intentionally creating an air gap between closely spaced metal lines. Undesirable topography is eliminated using a spin-on dielectric. We then cap the wafers with silicon dioxide and planarize using chemical mechanical polishing. Simple modeling of test structures predicts an equivalent dielectric constant of 1.9 on features similar to those expected for 0.25 micron technologies. Two level metal test structures fabricated in a 0.5 micron CMOS technology show that the process can be readily integrated with current standard CMOS processes. The potential problems of via misalignment, overall dielectric stack height, and the relative difficulty of ensuring void formation compared to that of ensuring a void-free fill are considered.

  5. ACRIM-gap and TSI trend issue resolved using a surface magnetic flux TSI proxy model

    NASA Astrophysics Data System (ADS)

    Scafetta, Nicola; Willson, Richard C.

    2009-03-01

    The ACRIM-gap (1989.5-1991.75) continuity dilemma for satellite TSI observations is resolved by bridging the satellite TSI monitoring gap between ACRIM1 and ACRIM2 results with TSI derived from Krivova et al.'s (2007) proxy model based on variations of the surface distribution of solar magnetic flux. `Mixed' versions of ACRIM and PMOD TSI composites are constructed with their composites' original values except for the ACRIM gap, where Krivova modeled TSI is used to connect ACRIM1 and ACRIM2 results. Both `mixed' composites demonstrate a significant TSI increase of 0.033 %/decade between the solar activity minima of 1986 and 1996, comparable to the 0.037 % found in the ACRIM composite. The finding supports the contention of Willson (1997) that the ERBS/ERBE results are flawed by uncorrected degradation during the ACRIM gap and refutes the Nimbus7/ERB ACRIM gap adjustment Fröhlich and Lean (1998) employed in constructing the PMOD.

  6. The effect of very small air gaps on small field dosimetry

    NASA Astrophysics Data System (ADS)

    Charles, P. H.; Crowe, S. B.; Kairn, T.; Kenny, J.; Lehmann, J.; Lye, J.; Dunn, L.; Hill, B.; Knight, R. T.; Langton, C. M.; Trapp, J. V.

    2012-11-01

    The purpose of this study was to investigate the effect of very small air gaps (less than 1 mm) on the dosimetry of small photon fields used for stereotactic treatments. Measurements were performed with optically stimulated luminescent dosimeters (OSLDs) for 6 MV photons on a Varian 21iX linear accelerator with a Brainlab µMLC attachment for square field sizes down to 6 mm × 6 mm. Monte Carlo simulations were performed using EGSnrc C++ user code cavity. It was found that the Monte Carlo model used in this study accurately simulated the OSLD measurements on the linear accelerator. For the 6 mm field size, the 0.5 mm air gap upstream to the active area of the OSLD caused a 5.3% dose reduction relative to a Monte Carlo simulation with no air gap. A hypothetical 0.2 mm air gap caused a dose reduction >2%, emphasizing the fact that even the tiniest air gaps can cause a large reduction in measured dose. The negligible effect on an 18 mm field size illustrated that the electronic disequilibrium caused by such small air gaps only affects the dosimetry of the very small fields. When performing small field dosimetry, care must be taken to avoid any air gaps, as can be often present when inserting detectors into solid phantoms. It is recommended that very small field dosimetry is performed in liquid water. When using small photon fields, sub-millimetre air gaps can also affect patient dosimetry if they cannot be spatially resolved on a CT scan. However the effect on the patient is debatable as the dose reduction caused by a 1 mm air gap, starting out at 19% in the first 0.1 mm behind the air gap, decreases to <5% after just 2 mm, and electronic equilibrium is fully re-established after just 5 mm.

  7. Testing the applicability of neural networks as a gap-filling method using CH4 flux data from high latitude wetlands

    NASA Astrophysics Data System (ADS)

    Dengel, S.; Zona, D.; Sachs, T.; Aurela, M.; Jammet, M.; Parmentier, F. J. W.; Oechel, W.; Vesala, T.

    2013-12-01

    Since the advancement in CH4 gas analyser technology and its applicability to eddy covariance flux measurements, monitoring of CH4 emissions is becoming more widespread. In order to accurately determine the greenhouse gas balance, high quality gap-free data is required. Currently there is still no consensus on CH4 gap-filling methods, and methods applied are still study-dependent and often carried out on low resolution, daily data. In the current study, we applied artificial neural networks to six distinctively different CH4 time series from high latitudes, explain the method and test its functionality. We discuss the applicability of neural networks in CH4 flux studies, the advantages and disadvantages of this method, and what information we were able to extract from such models. Three different approaches were tested by including drivers such as air and soil temperature, barometric air pressure, solar radiation, wind direction (indicator of source location) and in addition the lagged effect of water table depth and precipitation. In keeping with the principle of parsimony, we included up to five of these variables traditionally measured at CH4 flux measurement sites. Fuzzy sets were included representing the seasonal change and time of day. High Pearson correlation coefficients (r) of up to 0.97 achieved in the final analysis are indicative for the high performance of neural networks and their applicability as a gap-filling method for CH4 flux data time series. This novel approach which we show to be appropriate for CH4 fluxes is a step towards standardising CH4 gap-filling protocols.

  8. Testing the applicability of neural networks as a gap-filling method using CH4 flux data from high latitude wetlands

    NASA Astrophysics Data System (ADS)

    Dengel, S.; Zona, D.; Sachs, T.; Aurela, M.; Jammet, M.; Parmentier, F. J. W.; Oechel, W.; Vesala, T.

    2013-05-01

    Since the advancement in CH4 gas analyser technology and its applicability to eddy covariance flux measurements, monitoring of CH4 emissions is becoming more widespread. In order to accurately determine the greenhouse gas balance, high quality gap-free data is required. Currently there is still no consensus on CH4 gap-filling methods, and methods applied are still study-dependent and often carried out on low resolution daily data. In the current study, we applied artificial neural networks to six distinctively different CH4 time series from high latitudes in order to recover missing data points, explained the method and tested its functionality. We discuss the applicability of neural networks in CH4 flux studies, the advantages and disadvantages of this method, and what information we were able to extract from such models. In keeping with the principle of parsimony, we included only five standard meteorological variables traditionally measured at CH4 flux measurement sites. These included drivers such as air and soil temperature, barometric air pressure, solar radiation, and in addition wind direction (indicator of source location). Four fuzzy sets were included representing the time of day. High Pearson correlation coefficients (r) of 0.76-0.93 achieved in the final analysis are indicative for the high performance of neural networks and their applicability as a gap-filling method for CH4 flux data time series. This novel approach that we showed to be appropriate for CH4 fluxes is a step towards standardising CH4 gap-filling protocols.

  9. Gap-filling methods to impute eddy covariance flux data by preserving variance.

    NASA Astrophysics Data System (ADS)

    Kunwor, S.; Staudhammer, C. L.; Starr, G.; Loescher, H. W.

    2015-12-01

    To represent carbon dynamics, in terms of exchange of CO2 between the terrestrial ecosystem and the atmosphere, eddy covariance (EC) data has been collected using eddy flux towers from various sites across globe for more than two decades. However, measurements from EC data are missing for various reasons: precipitation, routine maintenance, or lack of vertical turbulence. In order to have estimates of net ecosystem exchange of carbon dioxide (NEE) with high precision and accuracy, robust gap-filling methods to impute missing data are required. While the methods used so far have provided robust estimates of the mean value of NEE, little attention has been paid to preserving the variance structures embodied by the flux data. Preserving the variance of these data will provide unbiased and precise estimates of NEE over time, which mimic natural fluctuations. We used a non-linear regression approach with moving windows of different lengths (15, 30, and 60-days) to estimate non-linear regression parameters for one year of flux data from a long-leaf pine site at the Joseph Jones Ecological Research Center. We used as our base the Michaelis-Menten and Van't Hoff functions. We assessed the potential physiological drivers of these parameters with linear models using micrometeorological predictors. We then used a parameter prediction approach to refine the non-linear gap-filling equations based on micrometeorological conditions. This provides us an opportunity to incorporate additional variables, such as vapor pressure deficit (VPD) and volumetric water content (VWC) into the equations. Our preliminary results indicate that improvements in gap-filling can be gained with a 30-day moving window with additional micrometeorological predictors (as indicated by lower root mean square error (RMSE) of the predicted values of NEE). Our next steps are to use these parameter predictions from moving windows to gap-fill the data with and without incorporation of potential driver variables

  10. Mapping forest canopy gaps using air-photo interpretation and ground surveys

    USGS Publications Warehouse

    Fox, T.J.; Knutson, M.G.; Hines, R.K.

    2000-01-01

    Canopy gaps are important structural components of forested habitats for many wildlife species. Recent improvements in the spatial accuracy of geographic information system tools facilitate accurate mapping of small canopy features such as gaps. We compared canopy-gap maps generated using ground survey methods with those derived from air-photo interpretation. We found that maps created from high-resolution air photos were more accurate than those created from ground surveys. Errors of omission were 25.6% for the ground-survey method and 4.7% for the air-photo method. One variable of inter est in songbird research is the distance from nests to gap edges. Distances from real and simulated nests to gap edges were longer using the ground-survey maps versus the air-photo maps, indicating that gap omission could potentially bias the assessment of spatial relationships. If research or management goals require location and size of canopy gaps and specific information about vegetation structure, we recommend a 2-fold approach. First, canopy gaps can be located and the perimeters defined using 1:15,000-scale or larger aerial photographs and the methods we describe. Mapped gaps can then be field-surveyed to obtain detailed vegetation data.

  11. Aging and the 4-kHz Air-Bone Gap

    ERIC Educational Resources Information Center

    Nondahl, David M.; Tweed, Ted S.; Cruickshanks, Karen J.; Wiley, Terry L.; Dalton, Dayna S.

    2012-01-01

    Purpose: In this study, the authors assessed age- and sex-related patterns in the prevalence and 10-year incidence of 4-kHz air-bone gaps and associated factors. Method: Data were obtained as part of the longitudinal, population-based Epidemiology of Hearing Loss Study ( Cruickshanks et al., 1998). An air-bone gap at 4 kHz was defined as an…

  12. Methane flux across the air-water interface - Air velocity effects

    NASA Technical Reports Server (NTRS)

    Sebacher, D. I.; Harriss, R. C.; Bartlett, K. B.

    1983-01-01

    Methane loss to the atmosphere from flooded wetlands is influenced by the degree of supersaturation and wind stress at the water surface. Measurements in freshwater ponds in the St. Marks Wildlife Refuge, Florida, demonstrated that for the combined variability of CH4 concentrations in surface water and air velocity over the water surface, CH4 flux varied from 0.01 to 1.22 g/sq m/day. The liquid exchange coefficient for a two-layer model of the gas-liquid interface was calculated as 1.7 cm/h for CH4 at air velocity of zero and as 1.1 + 1.2 v to the 1.96th power cm/h for air velocities from 1.4 to 3.5 m/s and water temperatures of 20 C.

  13. Bias stress effect in "air-gap" organic field-effect transistors.

    PubMed

    Chen, Y; Podzorov, V

    2012-05-22

    The origin of the bias stress effect related only to semiconductor properties is investigated in "air-gap" organic field-effect transistors (OFETs) in the absence of a material gate dielectric. The effect becomes stronger as the density of trap states in the semiconductor increases. A theoretical model based on carrier trapping and relaxation in localized tail states is formulated. Polar molecular vapors in the gap of "air-gap" OFETs also have a significant impact on the bias stress effect via the formation of bound states between the charge carriers and molecular dipoles at the semiconductor surface. PMID:22499410

  14. Influence of film thickness and air exposure on the transport gap of manganese phthalocyanine

    SciTech Connect

    Haidu, F.; Fechner, A.; Salvan, G.; Gordan, O. D.; Fronk, M.; Zahn, D. R. T.; Lehmann, D.; Mahns, B.; Knupfer, M.

    2013-06-15

    The interface formation between manganese phthalocyanine (MnPc) and cobalt was investigated combining ultraviolet photoelectron spectroscopy and inverse photoelectron spectroscopy. The transport band gap of the MnPc increases with the film thickness up to a value of (1.2 {+-} 0.3) eV while the optical band gap as determined from spectroscopic ellipsometry amounts to 0.5 eV. The gap values are smaller compared to other phthalocyanines due to metallic Mn 3d states close to the Fermi level. The transport band gap was found to open upon air exposure as a result of the disappearance of the occupied 3d electronic states.

  15. Air Pollution and Health: Bridging the Gap from Health Outcomes: Conference Summary

    EPA Science Inventory

    Air Pollution and Health: Bridging the Gap from Sources to Health Outcomes,” an international specialty conference sponsored by the American Association for Aerosol Research, was held to address key uncertainties in our understanding of adverse health effects related to air po...

  16. The effects of air gap reflections during air-coupled leaky Lamb wave inspection of thin plates.

    PubMed

    Fan, Zichuan; Jiang, Wentao; Cai, Maolin; Wright, William M D

    2016-02-01

    Air-coupled ultrasonic inspection using leaky Lamb waves offers attractive possibilities for non-contact testing of plate materials and structures. A common method uses an air-coupled pitch-catch configuration, which comprises a transmitter and a receiver positioned at oblique angles to a thin plate. It is well known that the angle of incidence of the ultrasonic bulk wave in the air can be used to preferentially generate specific Lamb wave modes in the plate in a non-contact manner, depending on the plate dimensions and material properties. Multiple reflections of the ultrasonic waves in the air gap between the transmitter and the plate can produce additional delayed waves entering the plate at angles of incidence that are different to those of the original bulk wave source. Similarly, multiple reflections of the leaky Lamb waves in the air gap between the plate and an inclined receiver may then have different angles of incidence and propagation delays when arriving at the receiver and hence the signal analysis may become complex, potentially leading to confusion in the identification of the wave modes. To obtain a better understanding of the generation, propagation and detection of leaky Lamb waves and the effects of reflected waves within the air gaps, a multiphysics model using finite element methods was established. This model facilitated the visualisation of the propagation of the reflected waves between the transducers and the plate, the subsequent generation of additional Lamb wave signals within the plate itself, their leakage into the adjacent air, and the reflections of the leaky waves in the air gap between the plate and receiver. Multiple simulations were performed to evaluate the propagation and reflection of signals produced at different transducer incidence angles. Experimental measurements in air were in good agreement with simulation, which verified that the multiphysics model can provide a convenient and accurate way to interpret the signals in

  17. Technical Note: Spatial resolution of proton tomography: Impact of air gap between patient and detector

    SciTech Connect

    Schneider, Uwe; Besserer, Juergen; Hartmann, Matthias

    2012-02-15

    Purpose: Proton radiography and tomography were investigated since the early 1970s because of its low radiation dose, high density resolution, and ability to image directly proton stopping power. However, spatial resolution is still a limiting factor. In this note, preliminary results of the impact of an air gap between detector system and patient on spatial resolution are presented. Methods: Spatial resolution of proton radiography and tomography is governed by multiple Coulomb scattering (MCS) of the protons in the patient. In this note, the authors employ Monte Carlo simulations of protons traversing a 20 cm thick water box. Entrance and exit proton coordinate measurements were simulated for improved spatial resolution. The simulations were performed with and without a 5 cm air gap in front of and behind the patient. Loss of spatial resolution due to the air gap was studied for protons with different initial angular confusion. Results: It was found that spatial resolution is significantly deteriorated when a 5 cm air gap between the position sensitive detector and the patient is included. For a perfect parallel beam spatial resolution worsens by about 40%. Spatial resolution is getting worse with increasing angular confusion and can reach 80%. Conclusions: When proton radiographies are produced by measuring the entrance and exit coordinates of the protons in front of and behind the patient the air gap between the detector and the patient can significantly deteriorate the spatial resolution of the system by up to 80%. An alternative would be to measure in addition to the coordinates also the exit and entrance angles of each proton. In principle, using the air gap size and proton angle, images can be reconstructed with the same spatial resolution than without air gap.

  18. Estimating ocean-air heat fluxes during cold air outbreaks by satellite

    NASA Technical Reports Server (NTRS)

    Chou, S. H.; Atlas, D.

    1981-01-01

    Nomograms of mean column heating due to surface sensible and latent heat fluxes were developed. Mean sensible heating of the cloud free region is related to the cloud free path (CFP, the distance from the shore to the first cloud formation) and the difference between land air and sea surface temperatures, theta sub 1 and theta sub 0, respectively. Mean latent heating is related to the CFP and the difference between land air and sea surface humidities q sub 1 and q sub 0 respectively. Results are also applicable to any path within the cloud free region. Corresponding heat fluxes may be obtained by multiplying the mean heating by the mean wind speed in the boundary layer. The sensible heating estimated by the present method is found to be in good agreement with that computed from the bulk transfer formula. The sensitivity of the solutions to the variations in the initial coastal soundings and large scale subsidence is also investigated. The results are not sensitive to divergence but are affected by the initial lapse rate of potential temperature; the greater the stability, the smaller the heating, other things being equal. Unless one knows the lapse rate at the shore, this requires another independent measurement. For this purpose the downwind slope of the square of the boundary layer height is used, the mean value of which is also directly proportional to the mean sensible heating. The height of the boundary layer should be measurable by future spaceborn lidar systems.

  19. Air gap resonant tunneling bandpass filter and polarizer.

    PubMed

    Melnyk, A; Bitarafan, M H; Allen, T W; DeCorby, R G

    2016-04-15

    We describe a bandpass filter based on resonant tunneling through an air layer in the frustrated total internal reflection regime, and show that the concept of induced transmission can be applied to the design of thin film matching stacks. Experimental results are reported for Si/SiO2-based devices exhibiting a polarization-dependent passband, with bandwidth on the order of 10 nm in the 1550 nm wavelength range, peak transmittance on the order of 80%, and optical density greater than 5 over most of the near infrared region. PMID:27082360

  20. 30 CFR 285.659 - What requirements must I include in my SAP, COP, or GAP regarding air quality?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 2 2010-07-01 2010-07-01 false What requirements must I include in my SAP, COP, or GAP regarding air quality? 285.659 Section 285.659 Mineral Resources MINERALS MANAGEMENT SERVICE... must I include in my SAP, COP, or GAP regarding air quality? (a) You must comply with the Clean Air...

  1. Interplay between Sb flux and growth temperature during the formation of GaSb islands on GaP

    NASA Astrophysics Data System (ADS)

    El Kazzi, S.; Desplanque, L.; Wallart, X.; Wang, Y.; Ruterana, P.

    2012-06-01

    We investigate the influence of the Sb flux on the growth of GaSb islands on a highly mismatched (001) GaP substrate. Between low and medium Sb flux values, standard kinetics drives the GaSb island formation and their relaxation is progressively favored by 90° misfit dislocations at the GaSb/GaP interface. However, under high Sb flux, the GaSb islands are elongated in the [110] direction and their density decreases. Further experiments varying the growth temperature at fixed Sb flux confirm this finding. We relate this observation to an enhancement of Ga diffusion when the effective Sb flux on the surface is increased. This behavior is qualitatively explained by the large cohesive energy of Sb-Sb bonds present on the surface, which impede the Ga adatom incorporation.

  2. Effect of wind tunnel air velocity on VOC flux rates from CAFO manure and wastewater

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Wind tunnels and flux chambers are often used to estimate volatile organic compound (VOC) emissions from animal feeding operations (AFOs) without regard to air velocity or sweep air flow rates. Laboratory experiments were conducted to evaluate the effect of wind tunnel air velocity on VOC emission ...

  3. Thickness and air gap measurement of assembled IR objectives

    NASA Astrophysics Data System (ADS)

    Lueerss, B.; Langehanenberg, P.

    2015-10-01

    A growing number of applications like surveillance, thermography, or automotive demand for infrared imaging systems. Their imaging performance is significantly influenced by the alignment of the individual lenses. Besides the lateral orientation of lenses, the air spacing between the lenses is a crucial parameter. Because of restricted mechanical accessibility within an assembled objective, a non-contact technique is required for the testing of these parameters. So far, commercial measurement systems were not available for testing of IR objectives since most materials used for infrared imaging are non-transparent at wavelengths below 2 μm. We herewith present a time-domain low coherent interferometer capable of measuring any kind of infrared material (e.g., Ge, Si, etc.) as well as VIS materials. The set-up is based on a Michelson interferometer in which the light from a broadband superluminescent diode is split into a reference arm with a variable optical delay and a measurement arm where the sample is placed. On a detector, the reflected signals from both arms are superimposed and recorded as a function of the variable optical path. Whenever the group delay difference is zero, a coherence peak occurs and the relative distances of the lens surfaces are derived from the optical delay. In order to penetrate IR materials, the instrument operates at 2.2 μm. Together with an LWIR autocollimator, this technique allows for the determination of centering errors, lens thicknesses and air spacings of assembled IR objective lenses with a micron accuracy. It is therefore a tool for precision manufacturing and quality control.

  4. [Spatiotemporal distribution pattern of photosynthetic photon flux density in forest gaps of Korean pine broadleaved mixed forest].

    PubMed

    Li, Meng; Duan, Wen-biao; Chen, Li-xin

    2011-04-01

    Taking the forest gaps of natural Pinus koraiensis broadleaved mixed forest in Xiao Xing'an Mountains as test object, and by the method of grids, the photosynthetic photon flux density (PPFD) in the gaps was continuously measured during growth season, and the spatiotemporal distribution patterns of the PPFD were analyzed by fundamental statistics and geostatistics methods. In the forest gaps, the high-value region of PPFD presented an obvious diurnal change, with the maximum PPFD appeared at 12:00 and in the northern part of the gaps. The mean monthly PPFD was the highest in June, and then decreased in the sequence of July, August, and September, with the largest coefficient of variation at different locations occurred in July and the medium variability in all the months. In different months, the intensity and the scale of PPFD spatial heterogeneity in the gaps differed, with the variation degree being the highest in June and the sill and proportion being the largest in July. The complex degree of the monthly PPFD patches also differed, with the maximum located in the northeast part of the gaps. The variation sequence of the mean monthly PPFD in understory and open ground was consistent with that in gap, and the mean monthly PPFD was the highest in open ground, medium in forest gap, and the lowest in understory.

  5. Predictive methods for estimating pesticide flux to air

    SciTech Connect

    Woodrow, J.E.; Seiber, J.N.

    1996-10-01

    Published evaporative flux values for pesticides volatilizing from soil, plants, and water were correlated with compound vapor pressures (VP), modified by compound properties appropriate to the treated matrix (e.g., soil adsorption coefficient [K{sub oc}], water solubility [S{sub w}]). These correlations were formulated as Ln-Ln plots with correlation (r{sup 2}) coefficients in the range 0.93-0.99: (1) Soil surface - Ln flux vs Ln (VP/[K{sub oc} x S{sub w}]); (2) soil incorporation - Ln flux vs Ln [(VP x AR)/(K{sub oc} x S{sub w} x d)] (AR = application rate, d = incorporation depth); (3) plants - Ln flux vs Ln VP; and (4) water - Ln (flux/water conc) vs Ln (VP/Sw). Using estimated flux values from the plant correlation as source terms in the EPA`s SCREEN-2 dispersion model gave downwind concentrations that agreed to within 65-114% with measured concentrations. Further validation using other treated matrices is in progress. These predictive methods for estimating flux, when coupled with downwind dispersion modeling, provide tools for limiting downwind exposures.

  6. Method and radial gap machine for high strength undiffused brushless operation

    DOEpatents

    Hsu, John S.

    2006-10-31

    A radial gap brushless electric machine (30) having a stator (31) and a rotor (32) and a main air gap (34) also has at least one stationary excitation coil (35a, 36a) separated from the rotor (32) by a secondary air gap (35e, 35f, 36e, 36f) so as to induce a secondary flux in the rotor (32) which controls a resultant flux in the main air gap (34). Permanent magnetic (PM) material (38) is disposed in spaces between the rotor pole portions (39) to inhibit the second flux from leaking from the pole portions (39) prior to reaching the main air gap (34). By selecting the direction of current in the stationary excitation coil (35a, 36a) both flux enhancement and flux weakening are provided for the main air gap (34). A method of non-diffused flux enhancement and flux weakening for a radial gap machine is also disclosed.

  7. Measuring air gap width of permanent magnet linear generators using search coil sensor

    SciTech Connect

    Waters, R.; Danielsson, O.; Leijon, M.

    2007-01-15

    A concept for a wave power plant is being developed at the Centre for Renewable Electric Energy Conversion at the Angstroem Laboratory at Uppsala University. The concept is based on a permanent magnet linear generator placed on the seabed, directly driven by a surface following buoy. Critical for the survival of the generator is that the air gap between the moving and static parts of the generator is constantly fixed at the designed width to prevent the moving and static parts from connecting during operation. This paper shows the design and evaluation of an inductive sensor for measuring the air gap width during generator operation. In order to survive during years on the seafloor inside the wave power plants, the sensor has deliberately been chosen to be a passive component, as well as robust and compact. A coil etched on a printed circuit board, i.e., a search coil, was the chosen basis for the sensor. The sensor has been tested on an existing test rig of a wave power plant and the results have been compared with finite element simulations.The results show that a search coil magnetic sensor etched on a printed circuit board is a suitable concept for measuring the air gap width. Experimentally measured and theoretically calculated sensor signals show very good agreement. The setup has a sensitivity of {+-}0.4 mm in the range of 4-9.5 mm air gap. The potential for future improvements of the sensitivity is considerable.

  8. CHARACTERIZING DETONATING LX-17 CHARGES CROSSING A TRANSVERSE AIR GAP WITH EXPERIMENTS AND MODELING

    SciTech Connect

    Lauderbach, L M; Souers, P C; Garcia, F; Vitello, P; Vandersall, K S

    2009-06-26

    Experiments were performed using detonating LX-17 (92.5% TATB, 7.5% Kel-F by weight) charges with various width transverse air gaps with manganin peizoresistive in-situ gauges present. The experiments, performed with 25 mm diameter by 25 mm long LX-17 pellets with the transverse air gap in between, showed that transverse gaps up to about 3 mm could be present without causing the detonation wave to fail to continue as a detonation. The Tarantula/JWL{sup ++} code was utilized to model the results and compare with the in-situ gauge records with some agreement to the experimental data with additional work needed for a better match to the data. This work will present the experimental details as well as comparison to the model results.

  9. Transpiration's inhibition of air pollution fluxes to substomatal cavities. [PRECP

    SciTech Connect

    Slinn, W.G.N.

    1987-05-01

    This report presents an estimate for the resistance to transport through stomatal openings, accounting for the counterflowing flux of water vapor associated with transpiration. The specific goal of this report is to estimate the influence of transpiration on the stomatal resistance, r/sub sto/; others have estimated the substomatal and mesophyll resistances r/sub ssc/ and r/sub mes/. It might be expected that any influence of the water-vapor flux on pollutant transport would be a maximum at the stomatal opening since, at the constricted area of the stoma, the water flux is a maximum. Transpiration through stomata appears to insigifnicantly inhibit the passage of relatively small molecules (e.g., SO/sub 2/, O/sub 3/, HNO/sub 3/, PAN, etc.) through the stomata, and therefore, by entering the substomatal cavity, such pollutants have greater potential for threatening plan survival, if their concentrations are excessive. 7 refs., 5 figs.

  10. The effect of body postures on the distribution of air gap thickness and contact area

    NASA Astrophysics Data System (ADS)

    Mert, Emel; Psikuta, Agnes; Bueno, Marie-Ange; Rossi, René M.

    2016-08-01

    The heat and mass transfer in clothing is predominantly dependent on the thickness of air layer and the magnitude of contact area between the body and the garment. The air gap thickness and magnitude of the contact area can be affected by the posture of the human body. Therefore, in this study, the distribution of the air gap and the contact area were investigated for different body postures of a flexible manikin. In addition, the effect of the garment fit (regular and loose) and style (t-shirts, sweatpants, jacket and trousers) were analysed for the interaction between the body postures and the garment properties. A flexible manikin was scanned using a three-dimensional (3D) body scanning technique, and the scans were post-processed in dedicated software. The body posture had a strong effect on the air gap thickness and the contact area for regions where the garment had a certain distance from the body. Furthermore, a mathematical model was proposed to estimate the possible heat transfer coefficient for the observed air layers and their change with posture. The outcome of this study can be used to improve the design of the protective and functional garments and predict their effect on the human body.

  11. Forests under climate change and air pollution: gaps in understanding and future directions for research.

    PubMed

    Matyssek, R; Wieser, G; Calfapietra, C; de Vries, W; Dizengremel, P; Ernst, D; Jolivet, Y; Mikkelsen, T N; Mohren, G M J; Le Thiec, D; Tuovinen, J-P; Weatherall, A; Paoletti, E

    2012-01-01

    Forests in Europe face significant changes in climate, which in interaction with air quality changes, may significantly affect forest productivity, stand composition and carbon sequestration in both vegetation and soils. Identified knowledge gaps and research needs include: (i) interaction between changes in air quality (trace gas concentrations), climate and other site factors on forest ecosystem response, (ii) significance of biotic processes in system response, (iii) tools for mechanistic and diagnostic understanding and upscaling, and (iv) the need for unifying modelling and empirical research for synthesis. This position paper highlights the above focuses, including the global dimension of air pollution as part of climate change and the need for knowledge transfer to enable reliable risk assessment. A new type of research site in forest ecosystems ("supersites") will be conducive to addressing these gaps by enabling integration of experimentation and modelling within the soil-plant-atmosphere interface, as well as further model development.

  12. Ocean Winds and Turbulent Air-Sea Fluxes Inferred From Remote Sensing

    NASA Technical Reports Server (NTRS)

    Bourassa, Mark A.; Gille, Sarah T.; Jackson, Daren L.; Roberts, J. Brent; Wick, Gary A.

    2010-01-01

    Air-sea turbulent fluxes determine the exchange of momentum, heat, freshwater, and gas between the atmosphere and ocean. These exchange processes are critical to a broad range of research questions spanning length scales from meters to thousands of kilometers and time scales from hours to decades. Examples are discussed (section 2). The estimation of surface turbulent fluxes from satellite is challenging and fraught with considerable errors (section 3); however, recent developments in retrievals (section 3) will greatly reduce these errors. Goals for the future observing system are summarized in section 4. Surface fluxes are defined as the rate per unit area at which something (e.g., momentum, energy, moisture, or CO Z ) is transferred across the air/sea interface. Wind- and buoyancy-driven surface fluxes are called surface turbulent fluxes because the mixing and transport are due to turbulence. Examples of nonturbulent processes are radiative fluxes (e.g., solar radiation) and precipitation (Schmitt et al., 2010). Turbulent fluxes are strongly dependent on wind speed; therefore, observations of wind speed are critical for the calculation of all turbulent surface fluxes. Wind stress, the vertical transport of horizontal momentum, also depends on wind direction. Stress is very important for many ocean processes, including upper ocean currents (Dohan and Maximenko, 2010) and deep ocean currents (Lee et al., 2010). On short time scales, this horizontal transport is usually small compared to surface fluxes. For long-term processes, transport can be very important but again is usually small compared to surface fluxes.

  13. 30 CFR 285.659 - What requirements must I include in my SAP, COP, or GAP regarding air quality?

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 2 2011-07-01 2011-07-01 false What requirements must I include in my SAP, COP, or GAP regarding air quality? 285.659 Section 285.659 Mineral Resources BUREAU OF OCEAN ENERGY... Pipeline Deviations § 285.659 What requirements must I include in my SAP, COP, or GAP regarding air...

  14. Band gap of two-dimensional fiber-air photonic crystals

    NASA Astrophysics Data System (ADS)

    Yang, Shu; Li, Masha

    2016-04-01

    A two-dimensional photonic crystal (PC) composed of textile fiber and air is initially discussed in this paper. Textile materials are so called soft materials, which are different from the previous PCs composed of rigid materials. The plain wave expansion method is used to calculate band structure of different PCs by altering component properties or structural parameters. Results show that the dielectric constant of textile fibers, fiber filling ratio and lattice arrangement are effective factors which influence PCs' band gap. Yet lattice constant and fiber diameter make inconspicuous influence on the band gap feature.

  15. A barometric pressure sensor based on the air-gap scale effect in a cantilever

    NASA Astrophysics Data System (ADS)

    Minh-Dung, Nguyen; Takahashi, Hidetoshi; Uchiyama, Takeshi; Matsumoto, Kiyoshi; Shimoyama, Isao

    2013-09-01

    The most common structure for a conventional barometric pressure sensor consists of a vacuum-sealed cavity and a diaphragm. However, we hypothesize that a simple structure with an unsealed cavity and an ultra-thin cantilever can provide more sensitive measurements. We produced a 300-nm-thick cantilever with a small spring constant, which made the cantilever sensitive to low pressures. We demonstrated that miniaturizing the air-gap of the cantilever enables the sensor to measure barometric pressure changes at a low pressure change rate with a high resolution, which was 1 Pa at 0.05 Hz, and for a gap size of 1.7 μm.

  16. Comparisons of Ship-based Observations of Air-Sea Energy Budgets with Gridded Flux Products

    NASA Astrophysics Data System (ADS)

    Fairall, C. W.; Blomquist, B.

    2015-12-01

    Air-surface interactions are characterized directly by the fluxes of momentum, heat, moisture, trace gases, and particles near the interface. In the last 20 years advances in observation technologies have greatly expanded the database of high-quality direct (covariance) turbulent flux and irradiance observations from research vessels. In this paper, we will summarize observations from the NOAA sea-going flux system from participation in various field programs executed since 1999 and discuss comparisons with several gridded flux products. We will focus on comparisons of turbulent heat fluxes and solar and IR radiative fluxes. The comparisons are done for observing programs in the equatorial Pacific and Indian Oceans and SE subtropical Pacific.

  17. The measurement of water vapour transfer rate through clothing system with air gap between layers

    NASA Astrophysics Data System (ADS)

    Oh, Ae-Gyeong

    2008-02-01

    The experiments described in this paper are designed to test the water vapour transfer rates through outdoor clothing system with air gap between layers under conditions more closely actual wear. It was adopted distance of 5 mm to ensure no disturbance of the air gap thickness between layers throughout the measurement period with all fabrics. The results have indicated that the water vapour transfer rates of clothing system decrease very slightly with time, it is shown that they approached nearly equilibrium state throughout the experiment. It is revealed that the water vapour transfer rates of the clothing system were ordered into groups determined by the type of waterproof breathable fabric as a shell layer being ordered.

  18. Air Gaps, Size Effect, and Corner-Turning in Ambient LX-17

    SciTech Connect

    Souers, P C; Hernandez, A; Cabacungan, C; Fried, L; Garza, R; Glaesemann, K; Lauderbach, L; Liao, S; Vitello, P

    2008-02-05

    Various ambient measurements are presented for LX-17. The size (diameter) effect has been measured with copper and Lucite confinement, where the failure radii are 4.0 and 6.5 mm, respectively. The air well corner-turn has been measured with an LX-07 booster, and the dead-zone results are comparable to the previous TATB-boosted work. Four double cylinders have been fired, and dead zones appear in all cases. The steel-backed samples are faster than the Lucite-backed samples by 0.6 {micro}s. Bare LX-07 and LX-17 of 12.7 mm-radius were fired with air gaps. Long acceptor regions were used to truly determine if detonation occurred or not. The LX-07 crossed at 10 mm with a slight time delay. Steady state LX-17 crossed at 3.5 mm gap but failed to cross at 4.0 mm. LX-17 with a 12.7 mm run after the booster crossed a 1.5 mm gap but failed to cross 2.5 mm. Timing delays were measured where the detonation crossed the gaps. The Tarantula model is introduced as embedded in 0 reactive flow JWL++ and Linked Cheetah V4, mostly at 4 zones/mm. Tarantula has four pressure regions: off, initiation, failure and detonation. The physical basis of the input parameters is considered.

  19. Local droplet etching – Nanoholes, quantum dots, and air-gap heterostructures

    SciTech Connect

    Heyn, Ch.; Sonnenberg, D.; Graf, A.; Kerbst, J.; Stemmann, A.; Hansen, W.

    2014-05-15

    Local droplet etching (LDE) allows the self-organized generation of nanoholes in semiconductor surfaces and is fully compatible with molecular beam epitaxy (MBE). The influence of the process parameters as well as of droplet and substrate materials on the LDE nanohole morphology is discussed. Furthermore, recent applications of LDE, the fabrication of quantum dots by hole filling and the creation of air-gap heterostructures are addressed.

  20. Soil air and soil flux measurements of 222Radon and CO2: A soil flux parametrization at Lutjewad (NL)

    NASA Astrophysics Data System (ADS)

    Neubert, R. E. M.; Kettner, E.; Palstra, S. W. L.; Hoekman, S.; van der Graaf, E. R.

    2009-04-01

    Atmospheric 222Radon concentration measurements are used as a valuable transport tracer verifying the transport part of Carbon Cycle and Greenhouse Gas models. The production rate of the radioactive noble gas 222Radon (T1•2 = 3.8 days) by radioactive decay of 226Radium in the soil is constant, the absolute quantity depending on the local soil Radium concentration. The flux of 222Radon to the atmosphere (the soil exhalation, or effective atmospheric production rate), however, is not constant. It strongly depends on soil texture, soil humidity, precipitation and other parameters, but is nearly constant if these parameters stay unchanged. Recently, an effort has been done to predict this flux rate with widely available γ-dosimetry measurements (Szegvary et al., Predicting terrestrial 222Rn-flux using gamma dose rate as a proxy, ACP 7, 2789-2795, 2007), but real 222Radon-flux measurements are sparse. 222Radon undergoes the same transport processes on the way from soil to atmosphere as any other soil-derived (greenhouse) gas. This makes 222Radon an ideal tracer to separate variations in e.g. soil CO2-production from changes in the soil-atmosphere CO2-transport, both being reflected in the total soil-atmosphere CO2-flux. At the atmospheric measurement site Lutjewad in the north of the Netherlands (53N24'18", 6E21'13", www.rug.nl/ees/onderzoek/cio/projecten/atmosphericgases) we started in 2006 with the measurements of the soil 222Radon and CO2 concentration through soil probes as well as the Radon and CO2 soil fluxes by means of an automatic soil chamber. While there are up to eight soil air measurements per day, the soil chamber is automatically closed twice per day. The station is situated directly on the Waddensea dike at an elevation of 1 m a.s.l. on seaclay soil. The groundwater table shows variations between 0.5 m and 2 m below terrain. From our measurements we find that in the dryer summer season, from April to July, the mean 222Radon-flux can be up to 40

  1. Technique for measuring air flow and carbon dioxide flux in large, open-top chambers

    SciTech Connect

    Ham, J.M.; Owensby, C.E.; Coyne, P.I.

    1993-10-01

    Open-Top Chambers (OTCs) are commonly used to evaluate the effect of CO{sub 2},O{sub 3}, and other trace gases on vegetation. This study developed and tested a new technique for measuring forced air flow and net CO{sub 2} flux from OTCs. Experiments were performed with a 4.5-m diam. OTC with a sealed floor and a specialized air delivery system. Air flow through the chamber was computed with the Bernoulli equation using measurements of the pressure differential between the air delivery ducts and the chamber interior. An independent measurement of air flow was made simultaneously to calibrate and verify the accuracy of the Bernoulli relationship. The CO{sub 2} flux density was calculated as the product of chamber air flow and the difference in CO{sub 2} concentration between the air entering and exhausting from the OTC (C{sub in}-C{sub out}). Accuracy was evaluated by releasing CO{sub 2} within the OTC at known rates. Data were collected with OTCs at ambient and elevated CO{sub 2} ({approx}700 {mu}mol{sup -1}). Results showed the Bernoulli equation, with a flow coefficient of 0.7, accurately measured air flow in the OTC within {+-}5% regardless of flow rate and air duct geometry. Experiments in ambient OTCs showed CO{sub 2} flux density ({mu}mol m{sup -2} s{sup -1}), computed from 2-min averages of air flow and C{sub in} - C{sub out,} was typically within {+-} 10% of actual flux, provided that the exit air velocity at the top of the OTC was greater than 0.6 m s{sup -1}. Obtaining the same accuracy in CO{sub 2}-enriched OTCs required a critical exit velocity near 1.2 m s{sup -1} to minimize the incursion of ambient air and prevent contamination of exit gas sample. When flux data were integrated over time to estimate daily CO{sub 2} flux ({mu}mol m{sup -2} d{sup -1}), actual and measured values agreed to within {+-}2% for both ambient and CO{sub 2}-enriched chambers, suggesting that accurate measurements of daily net C exchange are possible with this technique.

  2. Dynamics of air gap formation around roots with changing soil water content.

    NASA Astrophysics Data System (ADS)

    Vetterlein, D.; Carminati, A.; Weller, U.; Oswald, S.; Vogel, H.-J.

    2009-04-01

    Most models regarding uptake of water and nutrients from soil assume intimate contact between roots and soil. However, it is known for a long time that roots may shrink under drought conditions. Due to the opaque nature of soil this process could not be observed in situ until recently. Combining tomography of the entire sample (field of view of 16 x 16 cm, pixel side 0.32 mm) with local tomography of the soil region around roots (field of view of 5 x 5 cm, pixel side 0.09 mm), the high spatial resolution required to image root shrinkage and formation of air-filled gaps around roots could be achieved. Applying this technique and combining it with microtensiometer measurements, measurements of plant gas exchange and microscopic assessment of root anatomy, a more detailed study was conducted to elucidate at which soil matric potential roots start to shrink in a sandy soil and which are the consequences for plant water relations. For Lupinus albus grown in a sandy soil tomography of the entire root system and of the interface between taproot and soil was conducted from day 11 to day 31 covering two drying cycles. Soil matric potential decreased from -36 hPa at day 11 after planting to -72, -251, -429 hPa, on day 17, 19, 20 after planting. On day 20 an air gap started to occur around the tap root and extended further on day 21 with matric potential below -429 hPa (equivalent to 5 v/v % soil moisture). From day 11 to day 21 stomatal conductivity decreased from 467 to 84 mmol m-2 s-1, likewise transpiration rate decreased and plants showed strong wilting symptoms on day 21. Plants were watered by capillary rise on day 21 and recovered completely within a day with stomatal conductivity increasing to 647 mmol m-2 s-1. During a second drying cycle, which was shorter as plants continuously increased in size, air gap formed again at the same matric potential. Plant stomatal conductance and transpiration decreased in a similar fashion with decreasing matric potential and

  3. Methods, fluxes and sources of gas phase alkyl nitrates in the coastal air.

    PubMed

    Dirtu, Alin C; Buczyńska, Anna J; Godoi, Ana F L; Favoreto, Rodrigo; Bencs, László; Potgieter-Vermaak, Sanja S; Godoi, Ricardo H M; Van Grieken, René; Van Vaeck, Luc

    2014-10-01

    The daily and seasonal atmospheric concentrations, deposition fluxes and emission sources of a few C3-C9 gaseous alkyl nitrates (ANs) at the Belgian coast (De Haan) on the Southern North Sea were determined. An adapted sampler design for low- and high-volume air-sampling, optimized sample extraction and clean-up, as well as identification and quantification of ANs in air samples by means of gas chromatography mass spectrometry, are reported. The total concentrations of ANs ranged from 0.03 to 85 pptv and consisted primarily of the nitro-butane and nitro-pentane isomers. Air mass backward trajectories were calculated by the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model to determine the influence of main air masses on AN levels in the air. The shorter chain ANs have been the most abundant in the Atlantic/Channel/UK air masses, while longer chain ANs prevailed in continental air. The overall mean N fluxes of the ANs were slightly higher for summer than those for winter-spring, although their contributions to the total nitrogen flux were low. High correlations between AN and HNO₂ levels were observed during winter/spring. During summer, the shorter chain ANs correlated well with precipitation. Source apportionment by means of principal component analysis indicated that most of the gas phase ANs could be attributed to traffic/combustion, secondary photochemical formation and biomass burning, although marine sources may also have been present and a contributing factor. PMID:24952420

  4. Methods, fluxes and sources of gas phase alkyl nitrates in the coastal air.

    PubMed

    Dirtu, Alin C; Buczyńska, Anna J; Godoi, Ana F L; Favoreto, Rodrigo; Bencs, László; Potgieter-Vermaak, Sanja S; Godoi, Ricardo H M; Van Grieken, René; Van Vaeck, Luc

    2014-10-01

    The daily and seasonal atmospheric concentrations, deposition fluxes and emission sources of a few C3-C9 gaseous alkyl nitrates (ANs) at the Belgian coast (De Haan) on the Southern North Sea were determined. An adapted sampler design for low- and high-volume air-sampling, optimized sample extraction and clean-up, as well as identification and quantification of ANs in air samples by means of gas chromatography mass spectrometry, are reported. The total concentrations of ANs ranged from 0.03 to 85 pptv and consisted primarily of the nitro-butane and nitro-pentane isomers. Air mass backward trajectories were calculated by the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model to determine the influence of main air masses on AN levels in the air. The shorter chain ANs have been the most abundant in the Atlantic/Channel/UK air masses, while longer chain ANs prevailed in continental air. The overall mean N fluxes of the ANs were slightly higher for summer than those for winter-spring, although their contributions to the total nitrogen flux were low. High correlations between AN and HNO₂ levels were observed during winter/spring. During summer, the shorter chain ANs correlated well with precipitation. Source apportionment by means of principal component analysis indicated that most of the gas phase ANs could be attributed to traffic/combustion, secondary photochemical formation and biomass burning, although marine sources may also have been present and a contributing factor.

  5. Effect of heterogenous and homogenous air gaps on dry heat loss through the garment.

    PubMed

    Mert, Emel; Psikuta, Agnes; Bueno, Marie-Ange; Rossi, René M

    2015-11-01

    In real life conditions, the trapped air between the human body and the garment has uneven shape and vary over the body parts as a consequence of the complex geometry of the human body. However, the existing clothing models assume uniform air layer between the human body and the garment or its full contact, which may cause large error in the output of simulations. Therefore, the aim of this study was to investigate the effect of a heterogeneous vertical air gap with different configuration of folds (size and frequency) on dry heat loss using a heated cylinder (Torso). It was found that the presence of folds in the garment led to an increased heat loss from the body in comparison to a homogeneous air gap of comparable size. Interestingly, the size of folds did not have an influence on the dry heat loss. Additionally, the effect of the contact area on dry heat loss became important when exceeding a threshold of about 42%. The results from this study are useful for modelling of a realistic dry heat loss through the clothing and contribute to the improvement of design of protective and active sport garments.

  6. Effect of heterogenous and homogenous air gaps on dry heat loss through the garment

    NASA Astrophysics Data System (ADS)

    Mert, Emel; Psikuta, Agnes; Bueno, Marie-Ange; Rossi, René M.

    2015-11-01

    In real life conditions, the trapped air between the human body and the garment has uneven shape and vary over the body parts as a consequence of the complex geometry of the human body. However, the existing clothing models assume uniform air layer between the human body and the garment or its full contact, which may cause large error in the output of simulations. Therefore, the aim of this study was to investigate the effect of a heterogeneous vertical air gap with different configuration of folds (size and frequency) on dry heat loss using a heated cylinder (Torso). It was found that the presence of folds in the garment led to an increased heat loss from the body in comparison to a homogeneous air gap of comparable size. Interestingly, the size of folds did not have an influence on the dry heat loss. Additionally, the effect of the contact area on dry heat loss became important when exceeding a threshold of about 42 %. The results from this study are useful for modelling of a realistic dry heat loss through the clothing and contribute to the improvement of design of protective and active sport garments.

  7. Measurement of air and VOC vapor fluxes during gas-driven soil remediation: bench-scale experiments.

    PubMed

    Kim, Heonki; Kim, Taeyun; Shin, Seungyeop; Annable, Michael D

    2012-09-01

    In this laboratory study, an experimental method was developed for the quantitative analyses of gas fluxes in soil during advective air flow. One-dimensional column and two- and three-dimensional flow chamber models were used in this study. For the air flux measurement, n-octane vapor was used as a tracer, and it was introduced in the air flow entering the physical models. The tracer (n-octane) in the gas effluent from the models was captured for a finite period of time using a pack of activated carbon, which then was analyzed for the mass of n-octane. The air flux was calculated based on the mass of n-octane captured by the activated carbon and the inflow concentration. The measured air fluxes are in good agreement with the actual values for one- and two-dimensional model experiments. Using both the two- and three-dimensional models, the distribution of the air flux at the soil surface was measured. The distribution of the air flux was found to be affected by the depth of the saturated zone. The flux and flux distribution of a volatile contaminant (perchloroethene) was also measured by using the two-dimensional model. Quantitative information of both air and contaminant flux may be very beneficial for analyzing the performance of gas-driven subsurface remediation processes including soil vapor extraction and air sparging.

  8. Satellite estimates of ocean-air heat fluxes during cold air outbreaks

    NASA Technical Reports Server (NTRS)

    Chou, S.-H.; Atlas, D.

    1982-01-01

    A method for estimating the heat and moisture fluxes of coastal waters using the cloud free path, the sea surface temperature, and the saturation water vapor mixing ratio is presented. Generalized nomograms for the surface sensible and latent heat fluxes are developed using the Stage and Businger (1981) mixed-layer model. The fluxes are found to be slightly dependent on wind speed. The results are found to be applicable to any path within the cloud-free region, with heat fluxes obtainable by multiplication of the mean heating by the mean wind speed in the boundary layer. Higher stability causes lowered heating. It is shown that the latent heat flux is linear. Applications of the method to lake-effect snowstorms and for verification of boundary-layer models are indicated.

  9. Extreme air-sea surface turbulent fluxes in mid latitudes - estimation, origins and mechanisms

    NASA Astrophysics Data System (ADS)

    Gulev, Sergey; Natalia, Tilinina

    2014-05-01

    Extreme turbulent heat fluxes in the North Atlantic and North Pacific mid latitudes were estimated from the modern era and first generation reanalyses (NCEP-DOE, ERA-Interim, MERRA NCEP-CFSR, JRA-25) for the period from 1979 onwards. We used direct surface turbulent flux output as well as reanalysis state variables from which fluxes have been computed using COARE-3 bulk algorithm. For estimation of extreme flux values we analyzed surface flux probability density distribution which was approximated by Modified Fisher-Tippett distribution. In all reanalyses extreme turbulent heat fluxes amount to 1500-2000 W/m2 (for the 99th percentile) and can exceed 2000 W/m2 for higher percentiles in the western boundary current extension (WBCE) regions. Different reanalyses show significantly different shape of MFT distribution, implying considerable differences in the estimates of extreme fluxes. The highest extreme turbulent latent heat fluxes are diagnosed in NCEP-DOE, ERA-Interim and NCEP-CFSR reanalyses with the smallest being in MERRA. These differences may not necessarily reflect the differences in mean values. Analysis shows that differences in statistical properties of the state variables are the major source of differences in the shape of PDF of fluxes and in the estimates of extreme fluxes while the contribution of computational schemes used in different reanalyses is minor. The strongest differences in the characteristics of probability distributions of surface fluxes and extreme surface flux values between different reanalyses are found in the WBCE extension regions and high latitudes. In the next instance we analyzed the mechanisms responsible for forming surface turbulent fluxes and their potential role in changes of midlatitudinal heat balance. Midlatitudinal cyclones were considered as the major mechanism responsible for extreme turbulent fluxes which are typically occur during the cold air outbreaks in the rear parts of cyclones when atmospheric conditions

  10. Emulating microwave-induced breakdown in air with trigatron spark gap

    NASA Astrophysics Data System (ADS)

    Lenardo, B.; Romero-Talamas, C. A.; Granatstein, V. L.; Nusinovich, G. S.

    2011-10-01

    A spark gap and power supply have been constructed to emulate the duration and energy dissipation of air breakdown induced by a 670GHz gyrotron beam, a source that our group plans to use to explore remote detection of concealed radioactive materials. The spark gap is being used in calibration and testing of diagnostics, including atomic line spectroscopy, mass spectrometry, and microwave scattering. The power supply accepts a variable high voltage input up to 5 kV, stores energy in a 1.8 microfarad capacitor, and arcs across a gap of 1.34 mm. The gap is triggered by a AA-battery powered piezoelectric igniter available commercially (used in common gas grills). Preliminary results show that for a charging voltage of 3 kV, we are able to trigger a spark with energy 1.78 +/- 0.23 Joules lasting approximately 2 microseconds, values which can be tuned by varying resistance and charging voltage of the discharge circuit. Our goal is to dissipate 3 Joules in 10 microseconds, which we expect to see in the gyrotron beam breakdown.

  11. Air Gaps, Size Effect, and Corner-Turning in Ambient LX-17

    SciTech Connect

    Souers, P C; Hernandez, A; Cabacungen, C; Fried, L; Garza, R; Glaesemann, K; Lauderbach, L; Liao, S; Vitello, P

    2007-05-30

    Various ambient measurements are presented for LX-17. The size (diameter) effect has been measured with copper and Lucite confinement, where the failure radii are 4.0 and 6.5 mm, respectively. The air well corner-turn has been measured with an LX-07 booster, and the dead-zone results are comparable to the previous TATB-boosted work. Four double cylinders have been fired, and dead zones appear in all cases. The steel-backed samples are faster than the Lucite-backed samples by 0.6 {micro}s. Bare LX-07 and LX-17 of 12.7 mm-radius were fired with air gaps. Long acceptor regions were used to truly determine if detonation occurred or not. The LX-07 crossed at 10 mm with a slight time delay. Steady state LX-17 crossed at 3.5 mm gap but failed to cross at 4.0 mm. LX-17 with a 12.7 mm run after the booster crossed a 1.5 mm gap but failed to cross 2.5 mm. Timing delays were measured where the detonation crossed the gaps. The Tarantula model is introduced as embedded in the Linked Cheetah V4.0 reactive flow code at 4 zones/mm. Tarantula has four pressure regions: off, initiation, failure and detonation. A report card of 25 tests run with the same settings on LX-17 is shown, possibly the most extensive simultaneous calibration yet tried with an explosive. The physical basis of some of the input parameters is considered.

  12. Soil Surface Carbon Dioxide Fluxes and Carbon Dioxide Concentrations in Soil Air

    NASA Astrophysics Data System (ADS)

    Arkebauer, T. J.; Billesbach, D.

    2006-12-01

    We have been monitoring soil surface CO2 fluxes at three AmeriFlux sites in eastern Nebraska for several years. Recently, we have installed soil CO2 sensors at the rainfed soybean site in order to obtain profiles of CO2 concentrations in soil air (to 0.8 m depth). Supporting data include profiles of soil water content and soil temperature, aboveground biomass, leaf area index and precipitation. Soil surface fluxes had been rather small for much of the 2006 growing season (e.g., midday values of about 5 umol/m2/s) due, in large part, to the very dry conditions in eastern Nebraska and the consequent low soil water contents. However, copious rainfall in August raised soil water contents to field capacity throughout the profile. Soil air CO2 concentrations during this period also increased and reached peaks near 10% (at 0.4 and 0.8 m depth). Through analyses of relationships between surface CO2 flux and profiles of soil parameters we seek to identify biophysical factors responsible for controlling surface fluxes as well as to begin to quantify sources and sinks of CO2 within the soil profile (e.g., plant-related production of CO2 due to root exudation and respiration). The influence of precipitation events on CO2 profiles and fluxes is of particular interest.

  13. Simulation-based study of air-sea momentum fluxes nearshore

    NASA Astrophysics Data System (ADS)

    Hao, Xuanting; Shen, Lian

    2015-11-01

    Momentum fluxes at sea surface are crucial to air-sea interactions. In nearshore regions, the bathymetry variation has a significant impact on the surface wave field and complicates the momentum fluxes at water surface. In this study, we extend a high order spectral method to address wave-bottom interactions and wave modeling. From the wave simulation data, we use the Hilbert-Huang transform to quantify the properties of the wave spectrum, based on which the wave field is reconstructed for the detailed mechanistic study of wind-wave interactions using large-eddy simulation for the wind field. The roughness of the water surface is quantified using a dynamic model for the effects of subgrid-scale waves. The results show that the waves are sensitive to the water depth variation. Associated with the changes in the wave field, the momentum fluxes at the air-sea interface increase in shallow regions.

  14. Climatic Impacts of a Stochastic Parameterization of Air-Sea Fluxes

    NASA Astrophysics Data System (ADS)

    Williams, P. D.

    2014-12-01

    The atmosphere and ocean are coupled by the exchange of fluxes across the ocean surface. Air-sea fluxes vary partly on scales that are too small and fast to be resolved explicitly in numerical models of weather and climate, making them a candidate for stochastic parameterization. This presentation proposes a nonlinear physical mechanism by which stochastic fluctuations in the air-sea buoyancy flux may modify the mean climate, even though the mean fluctuation is zero. The mechanism relies on a fundamental asymmetry in the physics of the ocean mixed layer: positive surface buoyancy fluctuations cannot undo the vertical mixing caused by negative fluctuations. The mechanism has much in common with Stommel's mixed-layer demon. The presentation demonstrates the mechanism in climate simulations with a comprehensive coupled atmosphere-ocean general circulation model (SINTEX-G). In the SINTEX-G simulations with stochastic air-sea buoyancy fluxes, significant changes are detected in the time-mean oceanic mixed-layer depth, sea-surface temperature, atmospheric Hadley circulation, and net upward water flux at the sea surface. Also, El Niño Southern Oscillation (ENSO) variability is significantly increased. The findings demonstrate that noise-induced drift and noise-enhanced variability, which are familiar concepts from simple climate models, continue to apply in comprehensive climate models with millions of degrees of freedom. The findings also suggest that the lack of representation of sub-grid variability in air-sea fluxes may contribute to some of the biases exhibited by contemporary climate models.

  15. Optimization of Magneto-Rheological Damper for Maximizing Magnetic Flux Density in the Fluid Flow Gap Through FEA and GA Approaches

    NASA Astrophysics Data System (ADS)

    Krishna, Hemanth; Kumar, Hemantha; Gangadharan, Kalluvalappil

    2016-06-01

    A magneto rheological (MR) fluid damper offers cost effective solution for semiactive vibration control in an automobile suspension. The performance of MR damper is significantly depends on the electromagnetic circuit incorporated into it. The force developed by MR fluid damper is highly influenced by the magnetic flux density induced in the fluid flow gap. In the present work, optimization of electromagnetic circuit of an MR damper is discussed in order to maximize the magnetic flux density. The optimization procedure was proposed by genetic algorithm and design of experiments techniques. The result shows that the fluid flow gap size less than 1.12 mm cause significant increase of magnetic flux density.

  16. Tuning efficiency and linewidth of electrostatically actuated multiple air-gap filters

    NASA Astrophysics Data System (ADS)

    Römer, F.; Prott, C.; Irmer, S.; Daleiden, J.; Tarraf, A.; Hillmer, H.; Strassner, M.

    2003-01-01

    We investigated the tuning efficiency of electrostatically actuated multiple air-gap filters fabricated in InP for dense wavelength division multiplex applications by comparing measured tuning curves with the results of optical and mechanical simulations. These filters exhibit a record tuning range of 127 nm at 7.3 V tuning voltage. The filters were measured in reflection using standard single mode fiber. The subsequent analysis is based on a one-dimensional electromechanical and optical model providing a reasonable estimation for the pull-in voltage. Optical simulations show that the filter linewidth does not affect the tuning efficiency.

  17. [Verification of exhaled air temperature and heat flux in respiratory diseases as useful biomarker].

    PubMed

    Ito, Wataru; Chihara, Junichi

    2008-12-01

    Asthma, chronic obstructive pulmonary disease, and diffuse panbronchiolitis are syndromes associated with chronic airway inflammation. In the conventional definition of inflammation, local pyrexia at the site of inflammation should be observed. However, there are very few reports that have evaluated the "heat" in inflammatory respiratory diseases. We considered that the evaluation of allergic airway inflammation such as asthma might be possible by measuring the exhaled air temperature, and devised an original device that stabilizes the flow rate, which is a very important factor for the direct measurement of heat. Moreover, an expiratory heat flux meter, which can detect a change in air temperature more precisely and immediately, was also incorporated into our original device. As a result, we succeeded in the measurement and evaluation of the heat flux and air temperature in healthy subjects and asthmatic patients, and, further, the air temperature was straightforwardly evaluated by a portable spirometer including a temperature sensor. These findings suggest that the heat flux and temperature of exhaled air can be used to objectively monitor airway inflammation noninvasively, and assist in the diagnosis/monitoring of inflammatory respiratory diseases, including asthma.

  18. Ammonia Flux at the Air-Water Interface of Tampa Bay

    NASA Astrophysics Data System (ADS)

    Mizak, C. A.; Poor, N. D.

    2003-12-01

    Recent nitrogen deposition research in the Tampa Bay Estuary indicates that ammonia deposition dominates the total dry nitrogen flux to the bay. Gaseous plus aerosol ammonia contribute approximately 450 tons per year or 60% of the total nitrogen deposition of 760 tons per year to the estuary. Research data also indicate that during the summer months, Tampa Bay may act as a source for atmospheric ammonia as water temperature and ammonium concentrations increase. Ammonia flux estimates will be derived from thirty days of daily summer air and water sampling at the Gandy Bridge air monitoring site located adjacent to Tampa Bay. Ammonia concentrations were measured at two heights with a URG, Inc. dual-pump annular denuder system (ADS), and water grab samples from two depths were analyzed in the laboratory for ammonium concentration. Hourly relative humidity, air and water temperature, pH and salinity were recorded at this site, and hourly wind speed and direction were obtained from the Environmental Protection Commission of Hillsborough County. Rainwater samples were obtained with a University of Michigan sequential rainwater collector and analyzed in the laboratory for ammonium concentration. The direction and magnitude for the ammonia flux will be calculated with a modified NOAA buoy model from measurements of wind speed, air and water temperature, air and water ammonia and ammonium concentrations, relative humidity, water pH and salinity. The results of this research will be used to improve the NOAA Buoy model, and to compare observed with modeled ammonia gradients.

  19. Vertical cavity surface emitting laser based on gallium arsenide/air-gap distributed Bragg reflectors: From concept to working devices

    NASA Astrophysics Data System (ADS)

    Mo, Qingwei

    Vertical-cavity surface-emitting lasers (VCSELs) have created new opportunities in optoelectronics. However, VCSELs have so far been commercialized mainly for operation at 0.85 mum, despite their potential importance at other wavelengths, such as 1.3 mum and 1.55 mum. The limitations at these longer wavelengths come from material characteristics, such as a low contrast ratio in mirror materials, lower mirror reflectivity, and smaller optical gain for longer wavelength materials versus AlGaAs/GaAs quantum wells. A similar situation, insufficient gain relative to the cavity loss, existed in the past for shorter wavelength VCSELs before high quality epitaxial mirrors were developed. Semiconductor/air-gap Distributed Bragg Reflectors (DBRs) are attractive due to their high index contrast, which leads to a high reflectivity, wide stop band and low optical loss mirror with a small number of pairs. This concept is ready to be integrated into material systems other than AlGaAs/GaAs, which is studied in this work. Therefore, the impact of these DBRs can be extended into both visible and longer infrared wavelengths as a solution to the trade-off between DBR and active region materials. Air-gap DBRs can also be used as basic building blocks of micro-opto-electro-mechanical systems (MOEMS). The high Q microcavity formed by the air-gap DBRs also provide a good platform for microcavity physics study. Air-gap DBRs are modeled using the transmission matrix formulae of the Maxwell equations. A comparison to existing DBR technology shows the great advantage and potential that the air-gap DBR possesses. Two types of air-gap are proposed and developed. The first one includes multiple GaAs/air pairs while the second one combines a single air-gap with metal and dielectric mirrors. New device structures and processing designs, especially an all-epitaxial lateral current and optical confinement technique, are carried out to incorporate air-gap DBRs into VCSEL structures. The first VCSEL

  20. Air-sea fluxes and surface layer turbulence around a sea surface temperature front

    NASA Technical Reports Server (NTRS)

    Friehe, C. A.; Shaw, W. J.; Davidson, K. L.; Rogers, D. P.; Large, W. G.; Stage, S. A.; Crescenti, G. H.; Khalsa, S. J. S.; Greenhut, G. K.; Li, F.

    1991-01-01

    The observed effects of sharp changes in sea surface temperature (SST) on the air-sea fluxes, surface roughness, and the turbulence structure in the surface layer and the marine atmospheric boundary layer are discussed. In situ flux and turbulence observations were carried out from three aircraft and two ships within the FASINEX framework. Three other aircraft used remote sensors to measure waves, microwave backscatter, and lidar signatures of cloud tops. Descriptions of the techniques, intercomparison of aircraft and ship flux data, and use of different methods for analyzing the fluxes from the aircraft data are described. Changing synoptic weather on three successive days yielded cases of wind direction both approximately parallel and perpendicular to a surface temperature front. For the wind perpendicular to the front, wind over both cold-to-warm and warm-to-cold surface temperatures occurred. Model results consistent with the observations suggest that an internal boundary layer forms at the SST.

  1. A gap-filling model for eddy covariance latent heat flux: Estimating evapotranspiration of a subtropical seasonal evergreen broad-leaved forest as an example

    NASA Astrophysics Data System (ADS)

    Chen, Yi-Ying; Chu, Chia-Ren; Li, Ming-Hsu

    2012-10-01

    SummaryIn this paper we present a semi-parametric multivariate gap-filling model for tower-based measurement of latent heat flux (LE). Two statistical techniques, the principal component analysis (PCA) and a nonlinear interpolation approach were integrated into this LE gap-filling model. The PCA was first used to resolve the multicollinearity relationships among various environmental variables, including radiation, soil moisture deficit, leaf area index, wind speed, etc. Two nonlinear interpolation methods, multiple regressions (MRS) and the K-nearest neighbors (KNNs) were examined with random selected flux gaps for both clear sky and nighttime/cloudy data to incorporate into this LE gap-filling model. Experimental results indicated that the KNN interpolation approach is able to provide consistent LE estimations while MRS presents over estimations during nighttime/cloudy. Rather than using empirical regression parameters, the KNN approach resolves the nonlinear relationship between the gap-filled LE flux and principal components with adaptive K values under different atmospheric states. The developed LE gap-filling model (PCA with KNN) works with a RMSE of 2.4 W m-2 (˜0.09 mm day-1) at a weekly time scale by adding 40% artificial flux gaps into original dataset. Annual evapotranspiration at this study site were estimated at 736 mm (1803 MJ) and 728 mm (1785 MJ) for year 2008 and 2009, respectively.

  2. Sea-air CO2 fluxes in the Indian Ocean between 1990 and 2009

    NASA Astrophysics Data System (ADS)

    Sarma, V. V. S. S.; Lenton, A.; Law, R. M.; Metzl, N.; Patra, P. K.; Doney, S.; Lima, I. D.; Dlugokencky, E.; Ramonet, M.; Valsala, V.

    2013-11-01

    The Indian Ocean (44° S-30° N) plays an important role in the global carbon cycle, yet it remains one of the most poorly sampled ocean regions. Several approaches have been used to estimate net sea-air CO2 fluxes in this region: interpolated observations, ocean biogeochemical models, atmospheric and ocean inversions. As part of the RECCAP (REgional Carbon Cycle Assessment and Processes) project, we combine these different approaches to quantify and assess the magnitude and variability in Indian Ocean sea-air CO2 fluxes between 1990 and 2009. Using all of the models and inversions, the median annual mean sea-air CO2 uptake of -0.37 ± 0.06 PgC yr-1 is consistent with the -0.24 ± 0.12 PgC yr-1 calculated from observations. The fluxes from the southern Indian Ocean (18-44° S; -0.43 ± 0.07 PgC yr-1 are similar in magnitude to the annual uptake for the entire Indian Ocean. All models capture the observed pattern of fluxes in the Indian Ocean with the following exceptions: underestimation of upwelling fluxes in the northwestern region (off Oman and Somalia), overestimation in the northeastern region (Bay of Bengal) and underestimation of the CO2 sink in the subtropical convergence zone. These differences were mainly driven by lack of atmospheric CO2 data in atmospheric inversions, and poor simulation of monsoonal currents and freshwater discharge in ocean biogeochemical models. Overall, the models and inversions do capture the phase of the observed seasonality for the entire Indian Ocean but overestimate the magnitude. The predicted sea-air CO2 fluxes by ocean biogeochemical models (OBGMs) respond to seasonal variability with strong phase lags with reference to climatological CO2 flux, whereas the atmospheric inversions predicted an order of magnitude higher seasonal flux than OBGMs. The simulated interannual variability by the OBGMs is weaker than that found by atmospheric inversions. Prediction of such weak interannual variability in CO2 fluxes by atmospheric

  3. Sea-air CO2 fluxes in the Indian Ocean between 1990 and 2009

    NASA Astrophysics Data System (ADS)

    Sarma, V. V. S. S.; Lenton, A.; Law, R.; Metzl, N.; Patra, P. K.; Doney, S.; Lima, I. D.; Dlugokencky, E.; Ramonet, M.; Valsala, V.

    2013-07-01

    The Indian Ocean (44° S-30° N) plays an important role in the global carbon cycle, yet remains one of the most poorly sampled ocean regions. Several approaches have been used to estimate net sea-air CO2 fluxes in this region: interpolated observations, ocean biogeochemical models, atmospheric and ocean inversions. As part of the RECCAP (REgional Carbon Cycle Assessment and Processes) project, we combine these different approaches to quantify and assess the magnitude and variability in Indian Ocean sea-air CO2 fluxes between 1990 and 2009. Using all of the models and inversions, the median annual mean sea-air CO2 uptake of -0.37 ± 0.06 Pg C yr-1, is consistent with the -0.24 ± 0.12 Pg C yr-1 calculated from observations. The fluxes from the Southern Indian Ocean (18° S-44° S; -0.43 ± 0.07 Pg C yr-1) are similar in magnitude to the annual uptake for the entire Indian Ocean. All models capture the observed pattern of fluxes in the Indian Ocean with the following exceptions: underestimation of upwelling fluxes in the northwestern region (off Oman and Somalia), over estimation in the northeastern region (Bay of Bengal) and underestimation of the CO2 sink in the subtropical convergence zone. These differences were mainly driven by a lack of atmospheric CO2 data in atmospheric inversions, and poor simulation of monsoonal currents and freshwater discharge in ocean biogeochemical models. Overall, the models and inversions do capture the phase of the observed seasonality for the entire Indian Ocean but over estimate the magnitude. The predicted sea-air CO2 fluxes by Ocean BioGeochemical Models (OBGM) respond to seasonal variability with strong phase lags with reference to climatological CO2 flux, whereas the atmospheric inversions predict an order of magnitude higher seasonal flux than OBGMs. The simulated interannual variability by the OBGMs is weaker than atmospheric inversions. Prediction of such weak interannual variability in CO2 fluxes by atmospheric inversions

  4. Effect of Wind Tunnel Air Velocity on VOC Flux from Standard Solutions and CAFO Manure/Wastewater

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Researchers and practitioners have used wind tunnels and flux chambers to quantify the flux of volatile organic compounds (VOCs), ammonia, and hydrogen sulfide and estimate emission factors from animal feeding operations (AFOs) without accounting for effects of air velocity or sweep air flow rate. L...

  5. 30 CFR 585.659 - What requirements must I include in my SAP, COP, or GAP regarding air quality?

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... implementing regulations as promulgated by the EPA under 40 CFR part 55. (b) For air quality modeling that you... 30 Mineral Resources 2 2014-07-01 2014-07-01 false What requirements must I include in my SAP, COP... What requirements must I include in my SAP, COP, or GAP regarding air quality? (a) You must comply...

  6. 30 CFR 585.659 - What requirements must I include in my SAP, COP, or GAP regarding air quality?

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... implementing regulations as promulgated by the EPA under 40 CFR part 55. (b) For air quality modeling that you... 30 Mineral Resources 2 2013-07-01 2013-07-01 false What requirements must I include in my SAP, COP... What requirements must I include in my SAP, COP, or GAP regarding air quality? (a) You must comply...

  7. 30 CFR 585.659 - What requirements must I include in my SAP, COP, or GAP regarding air quality?

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... implementing regulations as promulgated by the EPA under 40 CFR part 55. (b) For air quality modeling that you... 30 Mineral Resources 2 2012-07-01 2012-07-01 false What requirements must I include in my SAP, COP... What requirements must I include in my SAP, COP, or GAP regarding air quality? (a) You must comply...

  8. Distribution and air-sea fluxes of carbon dioxide on the Chukchi Sea shelf

    NASA Astrophysics Data System (ADS)

    Pipko, I. I.; Pugach, S. P.; Repina, I. A.; Dudarev, O. V.; Charkin, A. N.; Semiletov, I. P.

    2015-12-01

    This article presents the results of long-term studies of the dynamics of carbonate parameters and air-sea carbon dioxide fluxes on the Chukchi Sea shelf during the summer. As a result of the interaction of physical and biological factors, the surface waters on the west of Chukchi Sea were undersaturated with carbon dioxide when compared with atmospheric air; the partial pressure of CO2 varied in the range from 134 to 359 μatm. The average value of CO2 flux in the Chukchi Sea per unit area varied in the range from-2.4 to-22.0 mmol /(m2 day), which is significantly higher than the average value of CO2 flux in the World Ocean. It has been estimated that the minimal mass of C absorbed by the surface of Chukchi Sea from the atmosphere during ice-free season is 13 × 1012 g; a great part of this carbon is transported to the deeper layers of sea and isolated from the atmosphere for a long period of time. The studies of the carbonate system of the Chukchi Sea, especially of its western part, will provide some new data on the fluxes of carbon dioxide in the Arctic Ocean and their changes. Our analysis can be used for an interpretation of the satellite assessment of CO2 fluxes and dissolved CO2 distribution in the upper layers of the ocean.

  9. Root-soil air gap and resistance to water flow at the soil-root interface of Robinia pseudoacacia.

    PubMed

    Liu, X P; Zhang, W J; Wang, X Y; Cai, Y J; Chang, J G

    2015-12-01

    During periods of water deficit, growing roots may shrink, retaining only partial contact with the soil. In this study, known mathematical models were used to calculate the root-soil air gap and water flow resistance at the soil-root interface, respectively, of Robinia pseudoacacia L. under different water conditions. Using a digital camera, the root-soil air gap of R. pseudoacacia was investigated in a root growth chamber; this root-soil air gap and the model-inferred water flow resistance at the soil-root interface were compared with predictions based on a separate outdoor experiment. The results indicated progressively greater root shrinkage and loss of root-soil contact with decreasing soil water potential. The average widths of the root-soil air gap for R. pseudoacacia in open fields and in the root growth chamber were 0.24 and 0.39 mm, respectively. The resistance to water flow at the soil-root interface in both environments increased with decreasing soil water potential. Stepwise regression analysis demonstrated that soil water potential and soil temperature were the best predictors of variation in the root-soil air gap. A combination of soil water potential, soil temperature, root-air water potential difference and soil-root water potential difference best predicted the resistance to water flow at the soil-root interface.

  10. Air-sea exchange fluxes of synthetic polycyclic musks in the North Sea and the Arctic.

    PubMed

    Xie, Zhiyong; Ebinghaus, Ralf; Temme, Christian; Heemken, Olaf; Ruck, Wolfgang

    2007-08-15

    Synthetic polycyclic musk fragrances Galaxolide (HHCB) and Tonalide (AHTN) were measured simultaneously in air and seawater in the Arctic and the North Sea and in the rural air of northern Germany. Median concentrations of gas-phase HHCB and AHTN were 4 and 18 pg m(-3) in the Arctic, 28 and 18 pg m(-3) in the North Sea, and 71 and 21 pg m(-3) in northern Germany, respectively. Various ratios of HHCB/AHTN implied that HHCB is quickly removed by atmospheric degradation, while AHTN is relatively persistent in the atmosphere. Dissolved concentrations ranged from 12 to 2030 pg L(-1) for HHCB and from below the method detection limit (3 pg L(-1)) to 965 pg L(-1) for AHTN with median values of 59 and 23 pg L(-1), respectively. The medians of volatilization fluxes for HHCB and AHTN were 27.2 and 14.2 ng m(-2) day(-1) and the depositional fluxes were 5.9 and 3.3 ng m(-2) day(-1), respectively, indicating water-to-air volatilization is a significant process to eliminate HHCB and AHTN from the North Sea. In the Arctic, deposition fluxes dominated the air-sea gas exchange of HHCB and AHTN, suggesting atmospheric input controls the levels of HHCB and AHTN in the polar region.

  11. Sensitivity analysis of air gap motion with respect to wind load and mooring system for semi-submersible platform design

    NASA Astrophysics Data System (ADS)

    Huo, Fa-li; Nie, Yan; Yang, De-qing; Dong, Gang; Cui, Jin

    2016-07-01

    A design of semi-submersible platform is mainly based on the extreme response analysis due to the forces experienced by the components during lifetime. The external loads can induce the extreme air gap response and potential deck impact to the semi-submersible platform. It is important to predict air gap response of platforms accurately in order to check the strength of local structures which withstand the wave slamming due to negative air gap. The wind load cannot be simulated easily by model test in towing tank whereas it can be simulated accurately in wind tunnel test. Furthermore, full scale simulation of the mooring system in model test is still a tuff work especially the stiffness of the mooring system. Owing to the above mentioned problem, the model test results are not accurate enough for air gap evaluation. The aim of this paper is to present sensitivity analysis results of air gap motion with respect to the mooring system and wind load for the design of semi-submersible platform. Though the model test results are not suitable for the direct evaluation of air gap, they can be used as a good basis for tuning the radiation damping and viscous drag in numerical simulation. In the presented design example, a numerical model is tuned and validated by ANSYS AQWA based on the model test results with a simple 4 line symmetrical horizontal soft mooring system. According to the tuned numerical model, sensitivity analysis studies of air gap motion with respect to the mooring system and wind load are performed in time domain. Three mooring systems and five simulation cases about the presented platform are simulated based on the results of wind tunnel tests and sea-keeping tests. The sensitivity analysis results are valuable for the floating platform design.

  12. Simple air-gap fiber Fabry-Perot interferometers based on a fiber endface with Sn-microsphere overlay

    NASA Astrophysics Data System (ADS)

    Lee, Cheng-Ling; Hung, Cheng-Hung; Li, Chai-Ming; You, Yan-Wun

    2012-10-01

    This study presents a simple, cost-effective and sensitive air-gap fiber Fabry-Perot interferometer (AG-PPFI) which is based on a metal Tin (Sn)-overlaying fiber technique. An extremely small drop of metallic Sn was heated and then melted to shrink into a microsphere owing to the cohesion of the material. When a fiber was inserted into the melting Sn microsphere, an air gap was naturally formed between the fiber endface and the metal Sn during the cooling process. By carefully controlling the reaction time, various air-gaps can be formed as the Fabry-Perot interferometric cavities for the proposed AG-PPFIs. Measurements reveal that a smaller length of air-gap and heavier mass of Sn-microsphere are associated with higher sensitivity of temperature, but the former is dominated. A best temperature sensitivity of wavelength shift with +4.3 nm/°C is achieved when the air-gap is about 5 μm with mass of Sn-microsphere of about 10 μg. The variation of the wavelength shift is equivalent to sensitivity for a change in the cavity length of +14.83 nm/°C.

  13. Advances in Linked Air Quality, Farm Management and Biogeochemistry Models to Address Bidirectional Ammonia Flux in CMAQ

    EPA Science Inventory

    Recent increases in anthropogenic inputs of nitrogen to air, land and water media pose a growing threat to human health and ecosystems. Modeling of air-surface N flux is one area in need of improvement. Implementation of a linked air quality and cropland management system is de...

  14. "Advances in Linked Air Quality, Farm Management and Biogeochemistry Models to Address Bidrectional Ammonia Flux in CMAQ"

    EPA Science Inventory

    Recent increases in anthropogenic inputs of nitrogen to air, land and water media pose a growing threat to human health and ecosystems. Modeling of air-surface N flux is one area in need of improvement. Implementation of a linked air quality and cropland management system is de...

  15. A fiber inclinometer using a fiber microtaper with an air-gap microcavity fiber interferometer

    NASA Astrophysics Data System (ADS)

    Feng, Zhongyao; Gang, Tingting; Hu, Manli; Qiao, Xueguang; Liu, Nan; Rong, Qiangzhou

    2016-04-01

    A micro-inclinometer is proposed and demonstrated experimentally; the device consists of a micro-fiber taper followed by an air-gap microcavity. A part of the core mode can couple to cladding modes via the taper. These cladding modes and residual core modes transmitted to downstream of the Fabry-Perot (FP) interferometer. A fraction of these modes are reflected back to the SMF by two surfaces of the FP cavity and eventually recoupled to the leading-in SMF, resulting in a well-defined interference spectrum. The fringe contrast of the interferometer is highly sensitive to fiber bending with direction-independence and thus is capable of measuring tilt angles in high resolution. In addition, the interference wavelength always remains unchanged during the fiber bending.

  16. Influence of precipitation on the CO2 air-sea flux, an eddy covariance field study

    NASA Astrophysics Data System (ADS)

    Zavarsky, Alexander; Steinhoff, Tobias; Marandino, Christa

    2016-04-01

    During the SPACES-OASIS cruise (July-August 2015) from Durban, SA to Male, MV direct fluxes of CO2 and dimethyl sulfide (DMS) were measured using the eddy covariance (EC) technique. The cruise covered areas of sources and sinks for atmospheric CO2, where the bulk concentration gradient measurements resembled the Takahashi (2009) climatology. Most of the time, bulk CO2 fluxes (F=k* [cwater-cair]), calculated with the parametrization (k) by Nightingale et al. 2000, were in general agreement with direct EC measurements. However, during heavy rain events, the directly measured CO2 fluxes were 4 times higher than predicted. It has been previously described that rain influences the k parametrization of air-sea gas exchange, but this alone cannot explain the measured discrepancy. There is evidence that freshwater input and a change in the carbonate chemistry causes the water side concentration of ?c=cwater-cair to decrease. Unfortunately this cannot be detected by most bulk measurement systems. Using the flux measurements of an additional gas like DMS, this rain influence can be evaluated as DMS does not react to changes in the carbonate system and has a different solubility. A pending question is if the enhanced flux of CO2 in the ocean is sequestered into the ocean mixed layer and below. This question will be tackled using the GOTM model to understand the implications for the global carbon cycle.

  17. Mechanisms controlling the SST air-sea heat flux feedback and its dependence on spatial scale

    NASA Astrophysics Data System (ADS)

    Hausmann, Ute; Czaja, Arnaud; Marshall, John

    2016-05-01

    The turbulent air-sea heat flux feedback (α , in {W m}^{-2}{ K}^{-1} ) is a major contributor to setting the damping timescale of sea surface temperature (SST) anomalies. In this study we compare the spatial distribution and magnitude of α in the North Atlantic and the Southern Ocean, as estimated from the ERA-Interim reanalysis dataset. The comparison is rationalized in terms of an upper bound on the heat flux feedback, associated with "fast" atmospheric export of temperature and moisture anomalies away from the marine boundary layer, and a lower bound associated with "slow" export. It is found that regions of cold surface waters (≤ 10° C) are best described as approaching the slow export limit. This conclusion is not only valid at the synoptic scale resolved by the reanalysis data, but also on basin scales. In particular, it applies to the heat flux feedback acting as circumpolar SST anomaly scales are approached in the Southern Ocean, with feedbacks of ≤ 10 {W m}^{-2}{ K}^{-1} . In contrast, the magnitude of the heat flux feedback is close to that expected from the fast export limit over the Gulf Stream and its recirculation with values on the order of ≈40 {W m}^{-2}{ K}^{-1} . Further analysis suggests that this high value reflects a compensation between a moderate thermodynamic adjustment of the boundary layer, which tends to weaken the heat flux feedback, and an enhancement of the surface winds over warm SST anomalies, which tend to enhance the feedback.

  18. Surfactant-Assisted Voltage-Driven Silver Nanoparticle Chain Formation across Microelectrode Gaps in Air.

    PubMed

    Shah, Nidhi; Zamborini, Francis P

    2015-10-27

    Here we describe the electrodeposition of Ag in the presence of cetyltrimethylammonium bromide (CTAB) onto 5 μm gap Au interdigitated array (IDA) electrodes that are bare, thiol-functionalized, or thiol-functionalized and seeded with 4 nm diameter Au nanoparticles (NPs). After deposition, applying a voltage between 5 and 10 V in air for 0 to 1000 s resulted in one-dimensional (1D) Ag NP chains spanning across the IDA gap. The Ag NP chains form on IDAs functionalized with thiols and Au NP-seeded at about 5 V and at 10 V for the other nonseeded surfaces. Ag NP chains do not form at all up to 10 V when IDAs are treated with ozone or water soaking to remove possible CTA(+) ions from the surface, when Ag deposition takes place in the absence of CTAB, or when the voltage is applied under dry N2 (low humidity). Chain formation occurs by Ag moving from the positive to negative electrode. Coating the devices with a negatively charged surfactant, sodium dodecyl sulfate, also results in Ag NP chains by Ag moving from the positive to the negative electrodes, which confirms that the chains form by electrochemical oxidation at the positive electrode and deposition at the negative electrode. The surfactant ions and thin layer of water present in the humid environment facilitate this electrochemical process. PMID:26344389

  19. Surfactant-Assisted Voltage-Driven Silver Nanoparticle Chain Formation across Microelectrode Gaps in Air.

    PubMed

    Shah, Nidhi; Zamborini, Francis P

    2015-10-27

    Here we describe the electrodeposition of Ag in the presence of cetyltrimethylammonium bromide (CTAB) onto 5 μm gap Au interdigitated array (IDA) electrodes that are bare, thiol-functionalized, or thiol-functionalized and seeded with 4 nm diameter Au nanoparticles (NPs). After deposition, applying a voltage between 5 and 10 V in air for 0 to 1000 s resulted in one-dimensional (1D) Ag NP chains spanning across the IDA gap. The Ag NP chains form on IDAs functionalized with thiols and Au NP-seeded at about 5 V and at 10 V for the other nonseeded surfaces. Ag NP chains do not form at all up to 10 V when IDAs are treated with ozone or water soaking to remove possible CTA(+) ions from the surface, when Ag deposition takes place in the absence of CTAB, or when the voltage is applied under dry N2 (low humidity). Chain formation occurs by Ag moving from the positive to negative electrode. Coating the devices with a negatively charged surfactant, sodium dodecyl sulfate, also results in Ag NP chains by Ag moving from the positive to the negative electrodes, which confirms that the chains form by electrochemical oxidation at the positive electrode and deposition at the negative electrode. The surfactant ions and thin layer of water present in the humid environment facilitate this electrochemical process.

  20. Large Temporal Variations in Air-Sea CO2 Flux off the Coast of Georgia

    NASA Astrophysics Data System (ADS)

    Caves, J. K.; Sabine, C.; Cai, W.; Alin, S.

    2008-12-01

    Though the inner shelf is a small portion of global ocean area, its air-sea CO2 flux is disproportionately high. Due to its tight links with both terrestrial and oceanic systems, the inner shelf is likely to experience significant spatial and temporal variability. We measured the fugacity of CO2 (fCO2) continuously from July 2006 to June 2008 on a moored platform in Gray's Reef National Marine Sanctuary on Georgia's inner shelf. The long-term, high temporal resolution data has allowed us to begin to measure interannual variations in CO2 flux along the inner Georgia shelf. From July 2006-June 2007, the inner Georgia shelf was a CO2 sink (-3.26mmol/m2/day), while during following year, the shelf switched to being a source (2.26mmol/m2/day). Choice of wind data (satellite or buoy-derived) significantly alters these estimates of annual fluxes. QuikSCAT satellite wind data indicate a much larger sink (- 6.13mmol/m2/day) during 2006-2007, and a non-existent source (0.02mmol/m2/day) during 2007- 2008. An earlier, high-resolution spatial study from January 2005-May 2006 found that the inner shelf within the South Atlantic Bight may have been a source of 0.65 to 1.20mmol/m2/day, suggesting that the inner shelf may experience dramatic swings in CO2 flux. Though sea-surface temperature (SST) is the largest influence on surface water fCO2, average monthly SST varied little between both years; instead, possible explanations for the large variation in interannual CO2 flux include decreased biological production and increased river flow (and, hence carbon export) during 2007-2008. This is the first evidence of large-scale, annual switches in air-sea CO2 flux within an inner shelf, and it holds significant implications for global estimates of air-sea CO2 flux.

  1. Tunable complete photonic band gap in anisotropic photonic crystal slabs with non-circular air holes using liquid crystals

    NASA Astrophysics Data System (ADS)

    Fathollahi Khalkhali, T.; Bananej, A.

    2016-06-01

    In this study, we analyze the tunability of complete photonic band gap of square and triangular photonic crystal slabs composed of square and hexagonal air holes in anisotropic tellurium background with SiO2 as cladding material. The non-circular holes are infiltrated with liquid crystal. Using the supercell method based on plane wave expansion, we study the variation of complete band gap by changing the optical axis orientation of liquid crystal. Our numerical results show that noticeable tunability of complete photonic band gap can be obtained in both square and triangular structures with non-circular holes.

  2. Fabrication and optical properties of non-polar III-nitride air-gap distributed Bragg reflector microcavities

    SciTech Connect

    Tao, Renchun Kako, Satoshi; Arita, Munetaka; Arakawa, Yasuhiko

    2013-11-11

    Using the thermal decomposition technique, non-polar III-nitride air-gap distributed Bragg reflector (DBR) microcavities (MCs) with a single quantum well have been fabricated. Atomic force microscopy reveals a locally smooth DBR surface, and room-temperature micro-photoluminescence measurements show cavity modes. There are two modes per cavity due to optical birefringence in the non-polar MCs, and a systematic cavity mode shift with cavity thickness was also observed. Although the structures consist of only 3 periods (top) and 4 periods (bottom), a quality factor of 1600 (very close to the theoretical value of 2100) reveals the high quality of the air-gap DBR MCs.

  3. A flux-gradient system for simultaneous measurement of the CH4, CO2, and H2O fluxes at a lake-air interface.

    PubMed

    Xiao, Wei; Liu, Shoudong; Li, Hanchao; Xiao, Qitao; Wang, Wei; Hu, Zhenghua; Hu, Cheng; Gao, Yunqiu; Shen, Jing; Zhao, Xiaoyan; Zhang, Mi; Lee, Xuhui

    2014-12-16

    Inland lakes play important roles in water and greenhouse gas cycling in the environment. This study aims to test the performance of a flux-gradient system for simultaneous measurement of the fluxes of water vapor, CO2, and CH4 at a lake-air interface. The concentration gradients over the water surface were measured with an analyzer based on the wavelength-scanned cavity ring-down spectroscopy technology, and the eddy diffusivity was measured with a sonic anemometer. Results of a zero-gradient test indicate a flux measurement precision of 4.8 W m(-2) for water vapor, 0.010 mg m(-2) s(-1) for CO2, and 0.029 μg m(-2) s(-1) for CH4. During the 620 day measurement period, 97%, 69%, and 67% of H2O, CO2, and CH4 hourly fluxes were higher in magnitude than the measurement precision, which confirms that the flux-gradient system had adequate precision for the measurement of the lake-air exchanges. This study illustrates four strengths of the flux-gradient method: (1) the ability to simultaneously measure the flux of H2O, CO2, and CH4; (2) negligibly small density corrections; (3) the ability to resolve small CH4 gradient and flux; and (4) continuous and noninvasive operation. The annual mean CH4 flux (1.8 g CH4 m(-2) year(-1)) at this hypereutrophic lake was close to the median value for inland lakes in the world (1.6 g CH4 m(-2) year(-1)). The system has adequate precision for CH4 flux for broad applications but requires further improvement to resolve small CO2 flux in many lakes.

  4. Air-water gas exchange and CO2 flux in a mangrove-dominated estuary

    USGS Publications Warehouse

    Ho, David T.; Ferrón, Sara; Engel, Victor C.; Larsen, Laurel G.; Barr, Jordan G.

    2014-01-01

    Mangrove forests are highly productive ecosystems, but the fate of mangrove-derived carbon remains uncertain. Part of that uncertainty stems from the fact that gas transfer velocities in mangrove-surrounded waters are not well determined, leading to uncertainty in air-water CO2 fluxes. Two SF6 tracer release experiments were conducted to determine gas transfer velocities (k(600) = 8.3 ± 0.4 and 8.1 ± 0.6 cm h−1), along with simultaneous measurements of pCO2 to determine the air-water CO2 fluxes from Shark River, Florida (232.11 ± 23.69 and 171.13 ± 20.28 mmol C m−2 d−1), an estuary within the largest contiguous mangrove forest in North America. The gas transfer velocity results are consistent with turbulent kinetic energy dissipation measurements, indicating a higher rate of turbulence and gas exchange than predicted by commonly used wind speed/gas exchange parameterizations. The results have important implications for carbon fluxes in mangrove ecosystems.

  5. Heat flux: thermohydraulic investigation of solar air heaters used in agro-industrial applications

    NASA Astrophysics Data System (ADS)

    Rahmati Aidinlou, H.; Nikbakht, A. M.

    2016-07-01

    A new design of solar air heater simulator is presented to comply with the extensive applications inagro-industry. A wise installation of increased heat transfer surface area provided uniform and efficient heat diffusion over the duct. Nusselt number and friction factor have been investigated based on the constant roughness parameters such as relative roughness height (e/D), relative roughness pitch (P/e), angle of attack (α) and aspect ratio with Reynolds numbers ranging from 5000 to 19,000 in the fully developed region. Heat fluxes of 800, 900 and 1000 Wm-2 were provided. The enhancement in friction factor is observed to be 3.1656, 3.47 and 3.0856 times, and for the Nusselt number either, augmentation is calculated to be 1.4437, 1.4963 and 1.535 times, respectively, over the smooth duct for 800, 900 and 1000 Wm-2 heat fluxes. Thermohydraulic performance is plotted versus the Reynolds number based on the aforementioned roughness parameters at varying heat fluxes. The results show up that thermohydraulic performance is found to be maximum for 1000 Wm-2 at the average Reynolds number of 5151. Based on the results, we can verify that the introduced solar simulator can help analyzing and developing solar collector installations at the simulated heat fluxes.

  6. Diode laser-based air mass flux sensor for subsonic aeropropulsion inlets

    NASA Astrophysics Data System (ADS)

    Miller, Michael F.; Kessler, William J.; Allen, Mark G.

    1996-08-01

    An optical air mass flux sensor based on a compact, room-temperature diode laser in a fiber-coupled delivery system has been tested on a full-scale gas turbine engine. The sensor is based on simultaneous measurements of O 2 density and Doppler-shifted velocity along a line of sight across the inlet duct. Extensive tests spanning engine power levels from idle to full afterburner demonstrate accuracy and precision of the order of 1 2 of full scale in density, velocity, and mass flux. The precision-limited velocity at atmospheric pressure was as low as 40 cm s. Multiple data-reduction procedures are quantitatively compared to suggest optimal strategies for flight sensor packages.

  7. A fluorenone based low band gap solution processable copolymer for air stable and high mobility organic field effect transistors.

    PubMed

    Sonar, Prashant; Ha, Tae-Jun; Dodabalapur, Ananth

    2013-02-25

    A fluorenone based alternating copolymer () with a furan based fused aromatic moiety has been designed and synthesized. exhibits a small band gap with a lower HOMO value. Testing this polymer semiconductor as the active layer in organic thin-film transistors results in hole mobilities as high as 0.15 cm(2) V(-1) s(-1) in air.

  8. Heat flux measurements in stagnation point methane/air flames with thermographic phosphors

    NASA Astrophysics Data System (ADS)

    Salem, Mohamed; Staude, Susanne; Bergmann, Ulf; Atakan, Burak

    2010-10-01

    Light-induced phosphorescence from thermographic phosphors was used to study the wall temperatures and heat fluxes from nearly one-dimensional flat premixed flames. The investigated flames were stoichiometric, lean and rich laminar methane/air flames with equivalence ratios of φ = 1, φ = 0.75 and φ = 1.25 at ambient pressure. The flames were burning in a stagnation point arrangement against a water-cooled plate. The central part of this plate was an alumina ceramic plate coated from both sides with chromium-doped alumina (ruby) and excited with a Nd:YAG laser or a green light-emitting diode (LED) array to measure the wall temperature from both sides and thus the heat flux rate from the flame. The outlet velocity of the gases was varied from 0.1 to 1.2 m/s. The burner to plate distance (H) ranged from 0.5 to 2 times the burner exit diameter ( d = 30 mm). The measured heat flux rates indicate the change of the flame stabilization mechanism from a burner stabilized to a stagnation plate stabilized flame. The results were compared to modeling results of a one-dimensional stagnation point flow, with a detailed reaction mechanism. In order to prove the model, gas phase temperatures were measured by OH-LIF for a stoichiometric stagnation point flame. It turns out that the flame stabilization mechanism and with it the heat fluxes change from low to high mass fluxes. This geometry may be well suited for further studies of the elementary flame wall interaction.

  9. Air-sea interaction and surface flux in non-equilibrium sea-states

    SciTech Connect

    Levy, G.; Ek, M.; Mahrt, L.

    1994-12-31

    The wind forcing over the ocean determines the air-sea exchanges of heat, moisture and momentum which affect and drive the surface wave dynamics and the mixed layer circulation. In turn, it has been shown that wave dynamics and wave age affect ocean surface roughness and air-sea exchange processes so that the wind flow is not always in equilibrium with the ocean surface waves. This effect of wave spectrum on surface roughness has been discussed by many authors; yet it is rarely, if ever, accounted for in flux parameterization in models of the marine atmospheric boundary layer (MABL). Proper representation of these effects in both remote sensors` signal to geophysical-parameter models and in physical models of the ocean and the atmosphere on all scales is essential given the increased reliance of ocean monitoring systems on remote sea-surface sensors and the fundamental sensitivity of physical models to surface fluxes. In this paper the authors present a methodology for modeling these effects from data along with some results from data analyses of observations taken in two field experiments.

  10. Air-Sea Spray Airborne Radar Profiler Characterizes Energy Fluxes in Hurricanes

    NASA Technical Reports Server (NTRS)

    Durden, Stephen L.; Esteban-Fermandez, D.

    2010-01-01

    A report discusses ASAP (Air-sea Spray Airborne Profiler), a dual-wavelength radar profiler that provides measurement information about the droplet size distribution (DSD) of sea-spray, which can be used to estimate heat and moisture fluxes for hurricane research. Researchers have recently determined that sea spray can have a large effect on the magnitude and distribution of the air-sea energy flux at hurricane -force wind speeds. To obtain information about the DSD, two parameters of the DSD are required; for example, overall DSD amplitude and DSD mean diameter. This requires two measurements. Two frequencies are used, with a large enough separation that the differential frequency provides size information. One frequency is 94 GHz; the other is 220 GHz. These correspond to the Rayleigh and Mie regions. Above a surface wind speed of 10 m/ s, production of sea spray grows exponentially. Both the number of large droplets and the altitude they reach are a function of the surface wind speed.

  11. Air-Sea Methane Flux after the Deepwater Horizon Oil Leak

    NASA Astrophysics Data System (ADS)

    McAdoo, J.; Sweeney, C.; Kiene, R. P.; McGillis, W. R.

    2012-12-01

    One of the key questions associated with the Deepwater Horizon's (DWH) oil leak involves understanding how much of its methane is still entrained in deep waters. Analysis of air-sea fluxes reveals a slight decrease in average aqueous CH4 from 3.3 nM in June to 3.1 and 2.8 nM in August and September, respectively. The flux estimate showed higher methane flux to the atmosphere after the blowout was capped (3.8 μmol m-2 d-1 in August) compared to 0.024 μmol m-2 d-1 during the leak. Almost all observations were within the range of historical levels. The exception was one large peak to the southwest of the wellhead, but its contribution to atmospheric methane is found to be insignificant compared to the total amount of methane released by the leak. This result supports findings that DWH methane remained entrained in the deep waters and consequently is available for biological degradation and threatens to deplete oxygen, adding further stress to an area that already suffers from anoxic-induced dead zones.

  12. Surface-air mercury fluxes across Western North America: A synthesis of spatial trends and controlling variables

    USGS Publications Warehouse

    Eckley, Chris S.; Tate, Michael T.; Lin, Che-Jen; Gustin, Mae S.; Dent, Stephen; Eagles-Smith, Collin A.; Lutz, Michelle A; Wickland, Kimberly; Wang, Bronwen; Gray, John E.; Edwards, Grant; Krabbenhoft, David P.; Smith, David

    2016-01-01

    Mercury (Hg) emission and deposition can occur to and from soils, and are an important component of the global atmospheric Hg budget. This paper focuses on synthesizing existing surface-air Hg flux data collected throughout the Western North American region and is part of a series of geographically focused Hg synthesis projects. A database of existing Hg flux data collected using the dynamic flux chamber (DFC) approach from almost a thousand locations was created for the Western North America region. Statistical analysis was performed on the data to identify the important variables controlling Hg fluxes and to allow spatiotemporal scaling. The results indicated that most of the variability in soil-air Hg fluxes could be explained by variations in soil-Hg concentrations, solar radiation, and soil moisture. This analysis also identified that variations in DFC methodological approaches were detectable among the field studies, with the chamber material and sampling flushing flow rate influencing the magnitude of calculated emissions. The spatiotemporal scaling of soil-air Hg fluxes identified that the largest emissions occurred from irrigated agricultural landscapes in California. Vegetation was shown to have a large impact on surface-air Hg fluxes due to both a reduction in solar radiation reaching the soil as well as from direct uptake of Hg in foliage. Despite high soil Hg emissions from some forested and other heavily vegetated regions, the net ecosystem flux (soil flux + vegetation uptake) was low. Conversely, sparsely vegetated regions showed larger net ecosystem emissions, which were similar in magnitude to atmospheric Hg deposition (except for the Mediterranean California region where soil emissions were higher). The net ecosystem flux results highlight the important role of landscape characteristics in effecting the balance between Hg sequestration and (re-)emission to the atmosphere.

  13. On the Potential Impact of Daytime Surface Sensible Heat Flux on the Dissipation of Martian Cold Air Outbreaks

    NASA Technical Reports Server (NTRS)

    Segal, M.; Arritt, R. W.; Tillman, J. E.

    1997-01-01

    The Martian daytime soil surface temperature is governed primarily by the net irradiance balance and surface soil heat flux. Thus the outbreak of a cold air mass generates increased sensible heat flux that is conducive to daytime dissipation of the cold air mass thermal characteristics. Conceptual and scaling evaluations of this dissipation are provided while comparison is made with similar situations on Earth. It is estimated that sensible heat flux contribution to the dissipation of the original thermal structure of the cold air could be three times larger than the corresponding situation on Earth. Illustrative numerical model simulations provide scaling of the potential impact on the dissipation of cold air masses for various combinations of background wind speed and latitudes.

  14. BOREAS AFM-2 King Air 1994 Aircraft Flux and Moving Window Data

    NASA Technical Reports Server (NTRS)

    Kelly, Robert D.; Hall, Forrest G. (Editor); Newcomer, Jeffrey A. (Editor); Smith, David E. (Technical Monitor)

    2000-01-01

    The BOREAS AFM-2 team collected pass-by-pass fluxes (and many other statistics) for a large number of level (constant altitude), straight-line passes used in a variety of flight patterns. The data were collected by the University of Wyoming King Air in 1994 BOREAS IFCs 1-3. Most of these data were collected at 60-70 m above ground level, but a significant number of passes were also flown at various levels in the planetary boundary layer, up to about the inversion height. This documentation concerns only the data from the straight and level passes that are presented as original (over the NSA and SSA) and moving window values (over the Transect). Another archive of King Air data is also available, containing data from all the soundings flown by the King Air 1994 IFCs 1-3. The data are stored in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884) or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

  15. A fiber air-gap Fabry-Pérot temperature sensor demodulated by using frequency modulated continuous wave

    NASA Astrophysics Data System (ADS)

    Zheng, Wanfu; Xie, Jianglei; Li, Yi; Xu, Ben; Kang, Juan; Shen, Changyu; Wang, Jianfeng; Jin, Yongxing; Liu, Honglin; Ni, Kai; Dong, Xinyong; Zhao, Chunliu; Jin, Shangzhong

    In this study, a fiber in-line air-gap Fabry-Pérot interferometer (FPI) is fabricated by HF acid etching. For a low-cost and higher precise measurement, a demodulation system based on frequency modulated continuous wave (FMCW) technique is build up and demonstrated in this air-gap FPI. In temperature measurements, the temperature sensitivity is about 1.75 rad/°C by phase shift detection. We also test the long term performance of the system and the RMS error is about 0.04 rad, which corresponds to the temperature resolution of ~0.02 °C. It is much higher than the measurement resolution by using the traditional wavelength shift detection method. Our experiments show that the FMCW can provide a low-cost, high resolution and high speed interrogation solution to the fiber FPIs.

  16. Air-ice CO2 fluxes and pCO2 dynamics in the Arctic coastal area (Amundsen Gulf, Canada)

    NASA Astrophysics Data System (ADS)

    Geilfus, Nicolas-Xavier; Tison, Jean Louis; Carnat, Gauthier; Else, Brent; Borges, Alberto V.; Thomas, Helmuth; Shadwick, Elizabeth; Delille, Bruno

    2010-05-01

    Sea ice covers about 7% of the Earth surface at its maximum seasonal extent. For decades sea ice was assumed to be an impermeable and inert barrier for air - sea exchange of CO2 so that global climate models do not include CO2 exchange between the oceans and the atmosphere in the polar regions. However, uptake of atmospheric CO2 by sea ice cover was recently reported raising the need to further investigate pCO2 dynamics in the marine cryosphere realm and related air-ice CO2 fluxes. In addition, budget of CO2 fluxes are poorly constrained in high latitudes continental shelves [Borges et al., 2006]. We report measurements of air-ice CO2 fluxes above the Canadian continental shelf and compare them to previous measurements carried out in Antarctica. We carried out measurements of pCO2 within brines and bulk ice, and related air-ice CO2 fluxes (chamber method) in Antarctic first year pack ice ("Sea Ice Mass Balance in Antarctica -SIMBA" drifting station experiment September - October 2007) and in Arctic first year land fast ice ("Circumpolar Flaw Lead" - CFL, April - June 2008). These 2 experiments were carried out in contrasted sites. SIMBA was carried out on sea ice in early spring while CFL was carried out in from the middle of the winter to the late spring while sea ice was melting. Both in Arctic and Antarctic, no air-ice CO2 fluxes were detected when sea ice interface was below -10°C. Slightly above -10°C, fluxes toward the atmosphere were observed. In contrast, at -7°C fluxes from the atmosphere to the ice were significant. The pCO2 of the brine exhibits a same trend in both hemispheres with a strong decrease of the pCO2 anti-correlated with the increase of sea ice temperature. The pCO2 shifted from a large over-saturation at low temperature to a marked under-saturation at high temperature. These air-ice CO2 fluxes are partly controlled by the permeability of the air-ice interface, which depends of the temperature of this one. Moreover, air-ice CO2 fluxes are

  17. Calculation of nonequilibrium hydrogen-air reactions with implicit flux vector splitting method

    NASA Technical Reports Server (NTRS)

    Lee, Seung-Ho; Deiwert, George S.

    1989-01-01

    Two methods, fully- and loosely-coupled, are developed to incorporate nonequilibrium hydrogen-air chemistry into the fluid dynamic implicit flux vector splitting code (F3D). The new code (F3D/Chem) is validated against other existing codes for two cases: nozzle expansion, and shock-induced combustion around a blunt body. The shock-induced combustion case is compared also with an experimental data. The reaction rate constants are varied in an effort to reproduce the experimental data. The fully- and loosely-coupled methods are found to yield comparable results, but the computation time is shorter using the loosely-coupled method. The present method is found to reproduce results obtained using different existing codes. The experimental data was not reproduced with any selected rate coefficients set.

  18. The sensitivity of latent heat flux to the air humidity approximations used in ocean circulation models

    NASA Technical Reports Server (NTRS)

    Liu, W. Timothy; Niiler, Pearn P.

    1990-01-01

    In deriving the surface latent heat flux with the bulk formula for the thermal forcing of some ocean circulation models, two approximations are commonly made to bypass the use of atmospheric humidity in the formula. The first assumes a constant relative humidity, and the second supposes that the sea-air humidity difference varies linearly with the saturation humidity at sea surface temperature. Using climatological fields derived from the Marine Deck and long time series from ocean weather stations, the errors introduced by these two assumptions are examined. It is shown that the errors reach above 100 W/sq m over western boundary currents and 50 W/sq m over the tropical ocean. The two approximations also introduce erroneous seasonal and spatial variabilities with magnitudes over 50 percent of the observed variabilities.

  19. Amelioration of the reactive nitrogen flux calculation by a day/night separation in weekly mean air concentration measurements

    NASA Astrophysics Data System (ADS)

    Hayashi, Kentaro; Matsuda, Kazuhide; Ono, Keisuke; Tokida, Takeshi; Hasegawa, Toshihiro

    2013-11-01

    The low time resolution of air concentration data of atmospheric deposition in regional monitoring networks makes it difficult to estimate fluxes between the land and the atmosphere. The present study was an evaluation of the effects of day/night separation for a low time resolution of air concentration measurements (i.e., weekly mean) for the estimation of reactive nitrogen fluxes. The target chemical species included reactive nitrogen primarily ammonia (NH3) and nitric acid gas (HNO3) and secondarily nitrous acid gas, particulate ammonium, and particulate nitrate in addition to sulfur dioxide (SO2) as a reference. Monitoring was conducted for one year at a single-crop rice paddy field in central Japan. The study period was divided into the cropping and fallow seasons, which were characterized by rice plants or a drained bare soil surface, respectively. The filter-pack method was applied to measure the weekly mean air concentrations with day/night separation for the target species at two heights (6 and 2 m above the ground surface). Both an inferential and a gradient method were applied to calculate the deposition and exchange fluxes, respectively. The day/night separation in a weekly sampling protocol, on average, reduced the underestimation of HNO3 fluxes for the inferential method by 15.2% ± 6.8% and 8.2% ± 6.1% in the cropping and fallow seasons, respectively, and reduced the overestimation of NH3 fluxes for the gradient method by 121% ± 128% in the cropping season. The fluxes calculated using the inferential method agreed relatively well with those calculated using the gradient method for HNO3 and SO2. The use of single-height measurements for air concentrations with day/night separation and flux calculations using the inferential method are recommended as an appropriate way to enhance the quality in calculated fluxes while simultaneously suppress the increase in labor cost.

  20. Sea-air carbon dioxide fluxes along 35°S in the South Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Lencina-Avila, J. M.; Ito, R. G.; Garcia, C. A. E.; Tavano, V. M.

    2016-09-01

    The oceans play an important role in absorbing a significant fraction of the atmospheric CO2 surplus, but there are still uncertainties concerning several open ocean regions, such as the under-sampled South Atlantic Ocean. This study assessed the net sea-air CO2 fluxes and distribution of sea-surface CO2 fugacity (f C O2sw) along the 35°S latitude in the South Atlantic, during 2011 spring and early summer periods. Underway CO2 molar fraction, temperature, salinity and dissolved oxygen measurements were taken continuously from South American to South African continental shelves. Values of both satellite and discrete in situ chlorophyll-a concentration along the ship's track were used as ancillary data. Both f C O2sw and difference in sea-air fugacity (ΔfCO2) showed high variability along the cruise track, with higher values found on the continental shelf and slope regions. All ΔfCO2 values were negative, implying that a sinking process was occurring during the cruise period, with an average net CO2 flux of -3.1±2.2 mmol CO2 m-2 day-1 (using Wanninkhof, 1992). Physical variables were the main drivers of f C O2sw variability in South American continental shelf and open ocean regions, while the biological factor dominated the South African continental shelf. Algorithms for estimating fCO2 and temperature-normalized fCO2 were developed and applied separately to the three defined sub-regions: the South American shelf, the open ocean and the South African continental shelf, with the regional temperature-normalized fCO2 models showing better results.

  1. Oceanic distributions and air-sea fluxes of biogenic halocarbons in the open ocean

    NASA Astrophysics Data System (ADS)

    Chuck, Adele L.; Turner, Suzanne M.; Liss, Peter S.

    2005-10-01

    Surface seawater and atmospheric concentrations of methyl iodide, chloroiodomethane, bromoform, dichlorobromomethane, and chlorodibromethane were measured during three open ocean cruises in the Atlantic and Southern oceans. The measurements spanned a longitudinal range of 115°, between 50°N and 65°S. The saturation anomalies and the instantaneous air-sea fluxes of the gases during one of these cruises (ANT XVIII/1) are presented and discussed. Methyl iodide and chloroiodomethane were highly supersaturated (>1000%) throughout the temperate and tropical regions, with calculated mean fluxes of 15 and 5.5 nmol m-2 d-1, respectively. The oceanic emissions of the brominated compounds were less substantial, and a significant area of the temperate Atlantic Ocean was found to be a sink for bromoform. Correlation analyses have been used to investigate possible controls on the concentrations of these gases. In particular, the relationship of CH3I with sea surface temperature and light is discussed, with the tentative conclusion that this compound may be formed abiotically.

  2. Spatio-temporal visualization of air-sea CO2 flux and carbon budget using volume rendering

    NASA Astrophysics Data System (ADS)

    Du, Zhenhong; Fang, Lei; Bai, Yan; Zhang, Feng; Liu, Renyi

    2015-04-01

    This paper presents a novel visualization method to show the spatio-temporal dynamics of carbon sinks and sources, and carbon fluxes in the ocean carbon cycle. The air-sea carbon budget and its process of accumulation are demonstrated in the spatial dimension, while the distribution pattern and variation of CO2 flux are expressed by color changes. In this way, we unite spatial and temporal characteristics of satellite data through visualization. A GPU-based direct volume rendering technique using half-angle slicing is adopted to dynamically visualize the released or absorbed CO2 gas with shadow effects. A data model is designed to generate four-dimensional (4D) data from satellite-derived air-sea CO2 flux products, and an out-of-core scheduling strategy is also proposed for on-the-fly rendering of time series of satellite data. The presented 4D visualization method is implemented on graphics cards with vertex, geometry and fragment shaders. It provides a visually realistic simulation and user interaction for real-time rendering. This approach has been integrated into the Information System of Ocean Satellite Monitoring for Air-sea CO2 Flux (IssCO2) for the research and assessment of air-sea CO2 flux in the China Seas.

  3. Analyzing consistency of interannual variability in air-sea sensible and latent heat fluxes in CMIP5 model simulations

    NASA Astrophysics Data System (ADS)

    Serykh, Ilya; Gulev, Sergey

    2015-04-01

    Surface turbulent heat fluxes are critically important in climate model experiments, since they represent a language of communication of the ocean and atmosphere. Interannual variability of surface turbulent heat fluxes is believed to be the major contributor to the changes in the ocean surface heat balance, at least in mid latitudes. Being relatively well assessed and validated in reanalyses, surface turbulent heat fluxes always were of a lesser attention in diagnostics of climate model experiments. We analysed interannual variability of sensible and latent heat fluxes in historical climate simulations with several CMIP5 models. Variability in surface turbulent sensible and latent heat fluxes in model simulations has been analysed during several last decades (from 1950s to 2005) with the emphasis on different scales of variability (short-term, interannual, decadal). At all scales has been found a little consistency between the changes in turbulent surface fluxes diagnosed by reanalyses and blended data sets (OA-FLUX) on one hand and model simulations on the other. Furthermore, some models (e.g. ECHAM, IPSL) surprisingly demonstrate large regions with negative correlations between sensible and latent heat fluxes, which is not the case in observational data sets (reanalyses and OAFLUX). Interestingly, variability in air temperature and surface humidity (which could be potentially considered as the reason for autocorrelation between sensible and latent fluxes) demonstrates consistency with each other at most scales. Further we discuss potential reasons for the discovered phenomenon.

  4. Seasonal variations in concentrations, distributions, and air-soil exchange fluxes of dioxin-like polychlorinated biphenyls in Shanghai, China.

    PubMed

    Tian, Yajun; Nie, Zhiqiang; He, Jie; Die, Qingqi; Fang, Yanyan; Liu, Feng; Yang, Yufei; Gao, Xingbao; Huang, Qifei

    2016-02-01

    Dioxin-like polychlorinated biphenyl (dl-PCB) concentrations in ambient air and soil in Shanghai, China, were measured to allow seasonal and spatial differences in the dl-PCB concentrations, profiles, distributions, fugacity fractions, and air-soil fluxes to be determined. The toxic equivalent (TEQ) DL-PCB concentrations in the air were higher in summer (mean 9.46 fg m(-3), range 1.32-26.3 fg m(-3)) than in winter (mean 4.57 fg m(-3), range 1.55-10.9 fg m(-3)). The DL-PCB concentrations in air were different in different areas, and the concentrations decreased in the order industrial areas > commercial and residential areas > suburban areas > rural area. The mean DL-PCB concentration in soil was 0.25 pg TEQ g(-1) dry weight (dw) and the range was 0.05-0.90 pg TEQ g(-1) dw. The highest DL-PCB concentration in soil was found in a sample from a commercial/residential area. The DL-PCB fluxes were negative (-216 pg m(-2) h(-1) in summer and -41.1 pg m(-2) h(-1) in winter), and the fugacity fractions were below 0.5, indicating that dl-PCBs in Shanghai are deposited from the air to the soil in all seasons. The net fluxes were higher in summer than in winter, and the deposition fluxes were higher in industrial areas than in other areas in both summer and winter.

  5. Turbulent Fluxes and Pollutant Mixing during Wintertime Air Pollution Episodes in Complex Terrain.

    PubMed

    Holmes, Heather A; Sriramasamudram, Jai K; Pardyjak, Eric R; Whiteman, C David

    2015-11-17

    Cold air pools (CAPs) are stagnant stable air masses that form in valleys and basins in the winter. Low wintertime insolation limits convective mixing, such that pollutant concentrations can build up within the CAP when pollutant sources are present. In the western United States, wintertime CAPs often persist for days or weeks. Atmospheric models do not adequately capture the strength and evolution of CAPs. This is in part due to the limited availability of data quantifying the local turbulence during the formation, maintenance, and destruction of persistent CAPs. This paper presents observational data to quantify the turbulent mixing during two CAP episodes in Utah's Salt Lake Valley during February of 2004. Particulate matter (PM) concentration data and turbulence measurements for CAP and non-CAP time periods indicate that two distinct types of mixing scenarios occur depending on whether the CAP is dry or cloudy. Where cloudy, CAPs have enhanced vertical mixing due to top-down convection from the cloud layer. A comparison between the heat and momentum fluxes during 5 days of a dry CAP episode in February to those of an equivalent 5 day time period in March with no CAP indicates that the average turbulent kinetic energy during the CAP was suppressed by approximately 80%.

  6. Influence of eutrophication on air-water exchange, vertical fluxes, and phytoplankton concentrations of persistent organic pollutants

    SciTech Connect

    Dachs, J.; Eisenreich, S.J.; Hoff, R.M.

    2000-03-15

    The influence of eutrophication on the biogeochemical cycles of persistent organic pollutants (POPs) such as polychlorinated biphenyls (PCBs) is largely unknown. In this paper, the application of a dynamic air-water-phytoplankton exchange model to Lake Ontario is used as a framework to study the influence of eutrophication on air-water exchange, vertical fluxes, and phytoplankton concentrations of POPs. The results of these simulations demonstrate that air-water exchange controls phytoplankton concentrations in remote aquatic environments with little influence from land-based sources of pollutants and supports levels in even historically contaminated systems. Furthermore, eutrophication or high biomass leads to a disequilibrium between the gas and dissolved phase, enhanced air-water exchange, and vertical sinking fluxes of PCBs. Increasing biomass also depletes the water concentrations leading to lower than equilibrium PCB concentrations in phytoplankton. Implications to future trends in PCB pollution in Lake Ontario are also discussed.

  7. Plasmonic waveguide ring resonators with 4 nm air gap and λ0(2)/15,000 mode-area fabricated using photolithography.

    PubMed

    Lee, Jaehak; Song, Juhee; Sung, Gun Yong; Shin, Jung H

    2014-10-01

    Plasmonic air-gap disk resonators with 3.5 μm diameter and a 4 nm thick, 40 nm wide air gap for a mode area of only λ0(2)/15,000 were fabricated using photolithography only. The resonant modes were clearly identified using tapered fiber coupling method at the resonant wavelengths of 1280-1620 nm. We also demonstrate the advantage of the air-gap structure by using the resonators as label-free biosensors with a sensitivity of 1.6 THz/nm.

  8. A method of exploration of the atmosphere of Titan. [hot air balloon heated by solar radiation or planetary thermal flux

    NASA Technical Reports Server (NTRS)

    Blamont, J.

    1978-01-01

    A hot-air balloon, with the air heated by natural sources, is described. Buoyancy is accomplished by either solar heating or by utilizing the IR thermal flux of the planet to heat the gas in the balloon. Altitude control is provided by a valve which is opened and closed by a barometer. The balloon is made of an organic material which has to absorb radiant energy and to emit as little as possible.

  9. Using an ensemble data set of turbulent air-sea fluxes to evaluate the IPSL climate model in tropical regions

    NASA Astrophysics Data System (ADS)

    Gainusa-Bogdan, Alina; Servonnat, Jerome; Braconnot, Pascale

    2014-05-01

    Low-latitude turbulent ocean-atmosphere fluxes play a major role in the ocean and atmosphere dynamics, heat distribution and availability for meridional transport to higher latitudes, as well as for the global freshwater cycle. Their representation in coupled ocean-atmosphere models is thus of chief importance in climate simulations. Despite numerous reports of important observational uncertainties in large-scale turbulent flux products, only few model flux evaluation studies attempt to quantify and directly consider these uncertainties. To address this problem for large-scale, climatological flux evaluation, we assemble a comprehensive database of 14 climatological surface flux products, including in situ-based, satellite, hybrid and reanalysis data sets. We develop an associated analysis protocol and use it together with this database to offer an observational ensemble approach to model flux evaluation. We use this approach to perform an evaluation of the representation of the intertropical turbulent air-sea fluxes in a suite of CMIP5 historical simulations run with different recent versions of the IPSL model. To enhance model understanding, we consider both coupled and forced atmospheric model configurations. For the same purpose, we not only analyze the surface fluxes, but also their associated meteorological state variables and inter-variable relationships. We identify an important, systematic underestimation of the near-surface wind speed and a significant exaggeration of the sea-air temperature contrast in all the IPSL model versions considered. Furthermore, the coupled model simulations develop important sea surface temperature and associated air humidity bias patterns. Counterintuitively, these biases do not systematically transfer to significant biases in the surface fluxes. This is due to a combination of compensation of effects and the large flux observational spread. Our analyses reveal several inconsistencies in inter-variable relationships between

  10. Experimental Study on Branch and Diffuse Type of Streamers in Leader Restrike of Long Air Gap Discharge

    NASA Astrophysics Data System (ADS)

    Chen, She; Zeng, Rong; Zhuang, Chijie; Zhou, Xuan; Ding, Yujian

    2016-03-01

    One of the main problems in the Ultra High Voltage (UHV) transmission project is to choose the external insulation distance, which requires a deep understanding of the long air gap discharge mechanism. The leader-streamer propagation is one of most important stages in long air gap discharge. In the conductor-tower lattice configuration, we have measured the voltage, the current on the high voltage side and the electric field in the gap. While the streamer in the leader-streamer system presented a conical or hyperboloid diffuse shape, the clear branch structure streamer in front of the leader was firstly observed by a high speed camera in the experiment. Besides, it is found that the leader velocity, width and injected charge for the branch type streamer are greater than those of a diffuse type. We propose that the phenomenon results from the high humidity, which was 15.5-16.5 g/m3 in our experiment. supported by the Fund of the National Priority Basic Research of China (2011CB209403) and National Natural Science Foundation of China (Nos. 51325703, 51377094, 51577098)

  11. The influence of the sand-dust environment on air-gap breakdown discharge characteristics of the plate-to-plate electrode

    NASA Astrophysics Data System (ADS)

    He, Bo; Zhang, Gang; Chen, Bangfa; Gao, Naikui; Li, Yaozhong; Peng, Zongren; Jin, Haiyun

    2010-03-01

    The experiments of plane-plane gap discharge was carried out in an environment of artificial sandstorm. By comparing and analyzing the differences in gap breakdown voltage between the sand & dust environment and clean air, some problems were investigated, such as effects of wind speed and particle concentration on the breakdown voltage, differences of gap discharge characteristics between the dust & sand medium and the clean air medium. The results showed that compared with the clean air environment, the dust & sand environment had a decreased gap breakdown voltage. The longer the gap distance, the greater the voltage drop; the breakdown voltage decreased with the increase of particle concentration in flow. With the increase of wind speed, the breakdown voltage decreased at the beginning and rose afterwards. The results of the paper may helpful for further research regarding the unidentified flashover and external insulation characteristics of the HV power grid in the dust & sand environment.

  12. OAFlux Satellite-Based High-Resolution Analysis of Air-Sea Turbulent Heat, Moisture, and Momentum Fluxes

    NASA Astrophysics Data System (ADS)

    Yu, Lisan

    2016-04-01

    The Objectively Analyzed air-sea Fluxes (OAFlux) project at the Woods Hole Oceanographic Institution has recently developed a new suite of products: the satellite-based high-resolution (HR) air-sea turbulent heat, moisture, and momentum fluxes over the global ocean from 1987 to the present. The OAFlux-HR fluxes are computed from the COARE bulk algorithm using air-sea variables (vector wind, near-surface humidity and temperature, and ocean surface temperature) derived from multiple satellite sensors and multiple missions. The vector wind time series are merged from 14 satellite sensors, including 4 scatterometers and 10 passive microwave radiometers. The near-surface humidity and temperature time series are retrieved from 11 satellite sensors, including 7 microwave imagers and 4 microwave sounders. The endeavor has greatly improved the depiction of the air-sea turbulent exchange on the frontal and meso-scales. The OAFlux-HR turbulent flux products are valuable datasets for a broad range of studies, including the study of the long-term change and variability in the oean-surface forcing functions, quantification of the large-scale budgets of mass, heat, and freshwater, and assessing the role of the ocean in the change and variability of the Earth's climate.

  13. Preliminary study of osmotic membrane bioreactor: effects of draw solution on water flux and air scouring on fouling.

    PubMed

    Qin, Jian-Jun; Kekre, Kiran A; Oo, Maung H; Tao, Guihe; Lay, Chee L; Lew, Cheun H; Cornelissen, Emile R; Ruiken, Chris J

    2010-01-01

    Preliminary study on a novel osmotic membrane bioreactor (OMBR) was explored. Objective of this study was to investigate the effects of draw solution on membrane flux and air scouring at the feed side on fouling tendency in a pilot OMBR system composing the anoxic/aerobic and forward osmosis (FO) processes. Domestic sewage was the raw feed, FO membrane from HTI and NaCl/MgSO4 draw solutions were used in the experiments. Fluxes of 3 l/m2/h (LMH) and 7.2 LMH were achieved at osmotic pressure of 5 and 22.4 atm, respectively. No significant flux decline was observed at 3 LMH over 190 h and at 7.2 LMH over 150 h when air scouring was provided at the feed side of the membrane. However, without air scouring, the flux at 22.4 atm osmotic pressure declined by 30% after 195 h and then levelled off. The potential advantages of the fouling reversibility with air scouring under the operating conditions of the pilot OMBR and better water quality in OMBR over the conventional MBR were preliminarily demonstrated.

  14. Preliminary study of osmotic membrane bioreactor: effects of draw solution on water flux and air scouring on fouling.

    PubMed

    Qin, Jian-Jun; Kekre, Kiran A; Oo, Maung H; Tao, Guihe; Lay, Chee L; Lew, Cheun H; Cornelissen, Emile R; Ruiken, Chris J

    2010-01-01

    Preliminary study on a novel osmotic membrane bioreactor (OMBR) was explored. Objective of this study was to investigate the effects of draw solution on membrane flux and air scouring at the feed side on fouling tendency in a pilot OMBR system composing the anoxic/aerobic and forward osmosis (FO) processes. Domestic sewage was the raw feed, FO membrane from HTI and NaCl/MgSO4 draw solutions were used in the experiments. Fluxes of 3 l/m2/h (LMH) and 7.2 LMH were achieved at osmotic pressure of 5 and 22.4 atm, respectively. No significant flux decline was observed at 3 LMH over 190 h and at 7.2 LMH over 150 h when air scouring was provided at the feed side of the membrane. However, without air scouring, the flux at 22.4 atm osmotic pressure declined by 30% after 195 h and then levelled off. The potential advantages of the fouling reversibility with air scouring under the operating conditions of the pilot OMBR and better water quality in OMBR over the conventional MBR were preliminarily demonstrated. PMID:20861550

  15. Contribution of tropical cyclones to the air-sea CO2 flux: A global view

    NASA Astrophysics Data System (ADS)

    LéVy, M.; Lengaigne, M.; Bopp, L.; Vincent, E. M.; Madec, G.; Ethé, C.; Kumar, D.; Sarma, V. V. S. S.

    2012-06-01

    Previous case studies have illustrated the strong local influence of tropical cyclones (TCs) on CO2 air-sea flux ? suggesting that they can significantly contribute to the global ? In this study, we use a state-of-the art global ocean biochemical model driven by TCs wind forcing derived from a historical TCs database, allowing to sample the ? response under 1663 TCs. Our results evidence a very weak contribution of TCs to global ? one or two order of magnitude smaller than previous estimates extrapolated from case studies. This result arises from several competing effects involved in the ? response to TCs, not accounted for in previous studies. While previous estimates have hypothesized the ocean to be systematically oversaturated in CO2 under TCs, our results reveal that a similar proportion of TCs occur over oversaturated regions (i.e. the North Atlantic, Northeast Pacific and the Arabian Sea) and undersaturated regions (i.e. Westernmost North Pacific, South Indian and Pacific Ocean). Consequently, by increasing the gas exchange coefficient, TCs can generate either instantaneous CO2 flux directed from the ocean to the atmosphere (efflux) or the opposite (influx), depending on the CO2 conditions at the time of the TC passage. A large portion of TCs also occurs over regions where the ocean and the atmosphere are in near equilibrium, resulting in very weak instantaneous fluxes. Previous estimates also did not account for any asynchronous effect of TCs on ? during several weeks after the storm, oceanic pCO2 is reduced in response to vertical mixing, which systematically causes an influx anomaly. This implies that, contrary to previous estimates, TCs weakly affect the CO2 efflux when they blow over supersaturated areas because the instantaneous storm wind effect and post-storm mixing effect oppose with each other. In contrast, TCs increase the CO2 influx in undersaturated conditions because the two effects add up. These compensating effects result in a very weak

  16. Air-sea CO2 fluxes measured by eddy covariance in a coastal station in Baja California, México

    NASA Astrophysics Data System (ADS)

    Gutiérrez-Loza, L.; Ocampo-Torres, F. J.

    2016-05-01

    The influence of wave-associated parameters controlling turbulent CO2 fluxes through the air-sea water interface is evaluated in a coastal region. The study area, located within the Todos Santos Bay, Baja California, México, was found to be a weak sink of CO2 with a mean flux of -1.32 µmol m-2s-1. The low correlation found between flux and wind speed (r = 0.09), suggests that the influence of other forcing mechanisms, besides wind, is important for gas transfer modulation through the sea surface, at least for the conditions found in this study. In addition, the results suggest that for short periods where an intensification of the wave conditions occurs, a CO2 flux response increases the transport of gas to the ocean.

  17. Heat fluxes and roll circulations over the western Gulf Stream during an intense cold-air outbreak

    NASA Technical Reports Server (NTRS)

    Chou, Shu-Hsien; Ferguson, Michael P.

    1991-01-01

    Turbulence and heat fluxes in the marine atmospheric boundary layer (MABL) for three aircraft stacks near the western Gulf Stream front, observed during the Genesis of Atlantic Lows Experiment (GALE) January 28, 1986 cold-air outbreak, has been studied using mixed-layer scaling. The GOES image and stability parameter indicates that these three stacks were in the roll vortex regime. The turbulence structure in the MABL is studied for this case, as well as the significance of roll vortices to heat fluxes. The roll circulations are shown to contribute significantly to the sensible (temperature) and latent heat (moisture) fluxes with importance increasing upward. The results suggest that the entrainment at the MABL top might affect the the budgets of temperature and humidity fluxes in the lower MABL, but not in the unstable surface layer.

  18. Air Pollution and Health: Bridging the Gap from Sources to Health Outcomes

    EPA Science Inventory

    The U.S. Environmental Protection Agency (EPA) has established National Ambient Air Quality Standards (NAAQS) for six principal air pollutants (“criteria” pollutants): carbon monoxide (CO), lead (Pb), nitrogen dioxide (NO2), particulate matter (PM) in two size ranges [...

  19. Developing and Applications of a Gap-filling Model for Eddy covariance CO2 Flux: Evaluating the Net Ecosystem Exchange of a Subtropical Evergreen Forest after a Server Environmental Disturbance

    NASA Astrophysics Data System (ADS)

    Li, M.; CHEN, Y.

    2013-12-01

    Successful eddy covariance (EC) applications often challenged by several difficulties, including non-ideal micrometeorological conditions, instrument failures, measurement limitations, and lacking consistent footprint area. Consequently, the resultant gaps in the time series of EC measurements limit the use of these dataset and cause the uncertainty in a range of 1 to 2 ton C/ha/yr for evaluating net ecosystem exchange (NEE) after different CO2 gap-filling procedures (Saigusa et al., 2013). It is crucial to develop a suitable gap-filling model for EC CO2 flux observations to provide reliable long-term surface fluxes for numerous applications. In this study, a gap-filling model was developed for EC CO2 flux by linking the gap-filled water vapor fluxes estimated by Chen et al. (2012) and the optimal nearest QC/QA passed CO2 fluxes for interpolating CO2 flux gaps. Considering the atmosphere characteristics and controlling mechanisms of CO2 fluxes, measured hydrometerological and flux data at the Lien-Hua-Chih (LHC) experimental watershed were separated into clear sky and cloudy/nighttime conditions. The successful applications of our gap-filling approaches were examined with various sizes of artificial CO2 gaps. Without any significant environmental disturbance in 2012, the annual NEE of this subtropical evergreen forest was estimated around 6.7 ton C/ha/yr as the amount of terrestrial CO2 sequestration. The effect of sever Typhoon Soulik (11-13, July, 2013) invasion on several ecosystem variables, such as changes of intrinsic water use efficiency, leaf area index, and canopy storage capacity, will be investigated to propose indicators for estimating NEE variations in association with environmental disturbances at this forest ecosystem.

  20. Localization of metal-induced gap states at the metal-insulator interface: Origin of flux noise in SQUIDs and superconducting qubits

    SciTech Connect

    Choi, SangKook; Lee, Dung-Hai; Louie, Steven G.; Clarke, John

    2009-10-10

    The origin of magnetic flux noise in Superconducting Quantum Interference Devices with a power spectrum scaling as 1/f (f is frequency) has been a puzzle for over 20 years. This noise limits the decoherence time of superconducting qubits. A consensus has emerged that the noise arises from fluctuating spins of localized electrons with an areal density of 5 x 10(17)m(-2). We show that, in the presence of potential disorder at the metal-insulator interface, some of the metal-induced gap states become localized and produce local moments. A modest level of disorder yields the observed areal density.

  1. CO2 CH4 flux Air temperature Soil temperature and Soil moisture, Barrow, Alaska 2013 ver. 1

    SciTech Connect

    Margaret Torn

    2015-01-14

    This dataset consists of field measurements of CO2 and CH4 flux, as well as soil properties made during 2013 in Areas A-D of Intensive Site 1 at the Next-Generation Ecosystem Experiments (NGEE) Arctic site near Barrow, Alaska. Included are i) measurements of CO2 and CH4 flux made from June to September (ii) Calculation of corresponding Gross Primary Productivity (GPP) and CH4 exchange (transparent minus opaque) between atmosphere and the ecosystem (ii) Measurements of Los Gatos Research (LGR) chamber air temperature made from June to September (ii) measurements of surface layer depth, type of surface layer, soil temperature and soil moisture from June to September.

  2. Spatial Variability in Ozone and CO2 Flux during the Front Range Air Pollution and Photochemistry Experiment

    NASA Astrophysics Data System (ADS)

    Almand-Hunter, B.; Piedrahita, R.; Kaushik, A.; Noone, D. C.; Walker, J. T.; Hannigan, M.

    2014-12-01

    Air quality problems persist in the Northern Front-Range Metropolitan Area (NFRMA) of Colorado despite efforts to reduce emissions, and summertime ozone concentrations frequently exceed the NAAQS. Atmospheric modeling in the NFRMA is challenging due to the complex topography of the area, as well as diversity of pollutant sources (urban NOx and VOCs, power plants, oil and gas, agricultural emissions, biogenic emissions, and wildfires). An improved understanding of the local atmospheric chemistry will enable researchers to advance atmospheric models, which will subsequently be used to develop and test more effective air quality management strategies. The Front Range Air Pollution and Photochemistry Experiment (FRAPPE) investigates this problem through detailed examination of atmospheric chemistry in the NFRMA. Our project specifically explores the spatial variability in ozone (O3) concentration and dry deposition within the FRAPPE study area. One source of uncertainty in atmospheric models is O3 flux, which varies spatially due to local meteorology and variation in ambient concentration and deposition velocity. Model grid cells typically range in size from 10-100 km and 100-500 km, for regional and global models, respectively, and accurate representations of an entire grid cell cannot always be achieved. Large spatial variability within a model grid cell can lead to poor estimates of trace-gas flux and concentration. Our research addresses this issue by measuring spatial variability in O3 flux using low-cost dry-deposition flux chambers. We are measuring O3 and CO2 flux with 5 low-cost flux chambers and one eddy-covariance tower. The eddy-covariance tower is located at the Boulder Atmospheric Observatory in Erie, CO. All 5 chambers are within a 8.3 x 6 km square, with one chamber collocated with the eddy-covariance tower, and the other 4 chambers at distances of 0.33, 1.14, 3.22, and 7.55 km from the tower. The largest distance between any two chambers is 8.5 km. All

  3. CLIVAR-GSOP/GODAE Ocean Synthesis Inter-Comparison of Global Air-Sea Fluxes From Ocean and Coupled Reanalyses

    NASA Astrophysics Data System (ADS)

    Valdivieso, Maria

    2014-05-01

    The GODAE OceanView and CLIVAR-GSOP ocean synthesis program has been assessing the degree of consistency between global air-sea flux data sets obtained from ocean or coupled reanalyses (Valdivieso et al., 2014). So far, fifteen global air-sea heat flux products obtained from ocean or coupled reanalyses have been examined: seven are from low-resolution ocean reanalyses (BOM PEODAS, ECMWF ORAS4, JMA/MRI MOVEG2, JMA/MRI MOVECORE, Hamburg Univ. GECCO2, JPL ECCOv4, and NCEP GODAS), five are from eddy-permitting ocean reanalyses developed as part of the EU GMES MyOcean program (Mercator GLORYS2v1, Reading Univ. UR025.3, UR025.4, UKMO GloSea5, and CMCC C-GLORS), and the remaining three are couple reanalyses based on coupled climate models (JMA/MRI MOVE-C, GFDL ECDA and NCEP CFSR). The global heat closure in the products over the period 1993-2009 spanned by all data sets is presented in comparison with observational and atmospheric reanalysis estimates. Then, global maps of ensemble spread in the seasonal cycle, and of the Signal to Noise Ratio of interannual flux variability over the 17-yr common period are shown to illustrate the consistency between the products. We have also studied regional variability in the products, particularly at the OceanSITES project locations (such as, for instance, the TAO/TRITON and PIRATA arrays in the Tropical Pacific and Atlantic, respectively). Comparisons are being made with other products such as OAFlux latent and sensible heat fluxes (Yu et al., 2008) combined with ISCCP satellite-based radiation (Zhang et al., 2004), the ship-based NOC2.0 product (Berry and Kent, 2009), the Large and Yeager (2009) hybrid flux dataset CORE.2, and two atmospheric reanalysis products, the ECMWF ERA-Interim reanalysis (referred to as ERAi, Dee et al., 2011) and the NCEP/DOE reanalysis R2 (referred to as NCEP-R2, Kanamitsu et al., 2002). Preliminary comparisons with the observational flux products from OceanSITES are also underway. References Berry, D

  4. A comparison of airborne eddy correlation and bulk aerodynamic methods for ocean-air turbulent fluxes during cold-air outbreaks

    NASA Technical Reports Server (NTRS)

    Chou, Shu-Hsien

    1993-01-01

    The viscous interfacial-sublayer model of Liu et al. (1979) is used to derive four bulk schemes (LKB, FG, D, and DB), with the flux-profile relationships of Lie et al., Francey and Garratt (1981), Dyer (1974), and Dyer and Bradley (1982). These schemes, with stability-dependent transfer coefficients, are tested against the eddy-correlation fluxes measured at the 50-m flight level above the western Atlantic Ocean during cold-air outbreaks. The bulk fluxes of momentum (tau), sensible heat (H), and latent heat (E) are found to increase with various von Karman constants. The dependence of transfer coefficients on wind speeds and roughness lengths is discussed. The transfer coefficients for tau and E agree excellently between LKB and FG. The ratio of the coefficent for H of LKB to that of FG, increasing with decreasing stability, is very sensitive to stability at low winds, but approaches the neutral value of 1.25 at high winds.

  5. Band gap shift in the indium-tin-oxide films on polyethylene napthalate after thermal annealing in air

    NASA Astrophysics Data System (ADS)

    Han, H.; Mayer, J. W.; Alford, T. L.

    2006-10-01

    Indium-tin-oxide (ITO) thin films on polyethylene napthalate (PEN) with high carrier concentration (˜1021/cm3) have been grown by electron-beam deposition without the introduction of oxygen into the chamber. The electrical properties of the ITO films (such as, carrier concentration, electrical mobility, and resistivity) abruptly changed after annealing in the air atmospheres. In addition, optical transmittance and optical band gap values significantly changed after heat treatment. The optical band gap narrowing behavior is observed in the as-deposited sample because of impurity band and heavy carrier concentration. The influence of annealing in air on the electrical and optical properties of ITO/PEN samples can be explained by the change in the free electron concentration, which is evaluated in terms of the oxygen content. Rutherford backscattering spectrometry and x-ray photoelectron spectroscopy analyses are used to determine the oxygen content in the film. Hall effect measurements are used to determine the dependence of electrical properties on oxygen content.

  6. Air-Gapped Structures as Magnetic Elements for Use in Power Processing Systems. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Ohri, A. K.

    1977-01-01

    Methodical approaches to the design of inductors for use in LC filters and dc-to-dc converters using air gapped magnetic structures are presented. Methods for the analysis and design of full wave rectifier LC filter circuits operating with the inductor current in both the continuous conduction and the discontinuous conduction modes are also described. In the continuous conduction mode, linear circuit analysis techniques are employed, while in the case of the discontinuous mode, the method of analysis requires computer solutions of the piecewise linear differential equations which describe the filter in the time domain. Procedures for designing filter inductors using air gapped cores are presented. The first procedure requires digital computation to yield a design which is optimized in the sense of minimum core volume and minimum number of turns. The second procedure does not yield an optimized design as defined above, but the design can be obtained by hand calculations or with a small calculator. The third procedure is based on the use of specially prepared magnetic core data and provides an easy way to quickly reach a workable design.

  7. Air-sea fluxes in a climate model using hourly coupling between the atmospheric and the oceanic components

    NASA Astrophysics Data System (ADS)

    Tian, Fangxing; von Storch, Jin-Song; Hertwig, Eileen

    2016-06-01

    We analyse the changes in the air-sea fluxes of momentum, heat and fresh water flux caused by increasing the ocean-atmosphere coupling frequency from once per day to once per hour in the Max Planck Institute Earth System Model. We diagnose the relative influences of daily averaging and high-frequency feedbacks on the basic statistics of the air-sea fluxes at grid point level and quantify feedback modes responsible for large scale changes in fluxes over the Southern Ocean and the Equatorial Pacific. Coupling once per hour instead of once per day reduces the mean of the momentum-flux magnitude by up to 7 % in the tropics and increases it by up to 10 % in the Southern Ocean. These changes result solely from feedbacks between atmosphere and ocean occurring on time scales shorter than 1 day . The variance and extremes of all the fluxes are increased in most parts of the oceans. Exceptions are found for the momentum and fresh water fluxes in the tropics. The increases result mainly from the daily averaging, while the decreases in the tropics are caused by the high-frequency feedbacks. The variance increases are substantial, reaching up to 50 % for the momentum flux, 100 % for the fresh water flux, and a factor of 15 for the net heat flux. These diurnal and intra-diurnal variations account for up to 50-90 % of the total variances and exhibit distinct seasonality. The high-frequency coupling can influence the large-scale feedback modes that lead to large-scale changes in the magnitude of wind stress over the Southern Ocean and Equatorial Pacific. In the Southern Ocean, the dependence of the SST-wind-stress feedback on the mean state of SST, which is colder in the experiment with hourly coupling than in the experiment with daily coupling, leads to an increase of westerlies. In the Equatorial Pacific, Bjerknes feedback in the hourly coupled experiment reveals a diurnal cycle during the El Niño events, with the feedback being stronger in the nighttime than in the daytime and

  8. Effect of Sampling Depth on Air-Sea CO2 Flux Estimates in River-Stratified Arctic Coastal Waters

    NASA Astrophysics Data System (ADS)

    Miller, L. A.; Papakyriakou, T. N.

    2015-12-01

    In summer-time Arctic coastal waters that are strongly influenced by river run-off, extreme stratification severely limits wind mixing, making it difficult to effectively sample the surface 'mixed layer', which can be as shallow as 1 m, from a ship. During two expeditions in southwestern Hudson Bay, off the Nelson, Hayes, and Churchill River estuaries, we confirmed that sampling depth has a strong impact on estimates of 'surface' pCO2 and calculated air-sea CO2 fluxes. We determined pCO2 in samples collected from 5 m, using a typical underway system on the ship's seawater supply; from the 'surface' rosette bottle, which was generally between 1 and 3 m; and using a niskin bottle deployed at 1 m and just below the surface from a small boat away from the ship. Our samples confirmed that the error in pCO2 derived from typical ship-board versus small-boat sampling at a single station could be nearly 90 μatm, leading to errors in the calculated air-sea CO2 flux of more than 0.1 mmol/(m2s). Attempting to extrapolate such fluxes over the 6,000,000 km2 area of the Arctic shelves would generate an error approaching a gigamol CO2/s. Averaging the station data over a cruise still resulted in an error of nearly 50% in the total flux estimate. Our results have implications not only for the design and execution of expedition-based sampling, but also for placement of in-situ sensors. Particularly in polar waters, sensors are usually deployed on moorings, well below the surface, to avoid damage and destruction from drifting ice. However, to obtain accurate information on air-sea fluxes in these areas, it is necessary to deploy sensors on ice-capable buoys that can position the sensors in true 'surface' waters.

  9. Inverse modeling of Asian (222)Rn flux using surface air (222)Rn concentration.

    PubMed

    Hirao, Shigekazu; Yamazawa, Hiromi; Moriizumi, Jun

    2010-11-01

    When used with an atmospheric transport model, the (222)Rn flux distribution estimated in our previous study using soil transport theory caused underestimation of atmospheric (222)Rn concentrations as compared with measurements in East Asia. In this study, we applied a Bayesian synthesis inverse method to produce revised estimates of the annual (222)Rn flux density in Asia by using atmospheric (222)Rn concentrations measured at seven sites in East Asia. The Bayesian synthesis inverse method requires a prior estimate of the flux distribution and its uncertainties. The atmospheric transport model MM5/HIRAT and our previous estimate of the (222)Rn flux distribution as the prior value were used to generate new flux estimates for the eastern half of the Eurasian continent dividing into 10 regions. The (222)Rn flux densities estimated using the Bayesian inversion technique were generally higher than the prior flux densities. The area-weighted average (222)Rn flux density for Asia was estimated to be 33.0 mBq m(-2) s(-1), which is substantially higher than the prior value (16.7 mBq m(-2) s(-1)). The estimated (222)Rn flux densities decrease with increasing latitude as follows: Southeast Asia (36.7 mBq m(-2) s(-1)); East Asia (28.6 mBq m(-2) s(-1)) including China, Korean Peninsula and Japan; and Siberia (14.1 mBq m(-2) s(-1)). Increase of the newly estimated fluxes in Southeast Asia, China, Japan, and the southern part of Eastern Siberia from the prior ones contributed most significantly to improved agreement of the model-calculated concentrations with the atmospheric measurements. The sensitivity analysis of prior flux errors and effects of locally exhaled (222)Rn showed that the estimated fluxes in Northern and Central China, Korea, Japan, and the southern part of Eastern Siberia were robust, but that in Central Asia had a large uncertainty.

  10. A Sensitivity Analysis of the Impact of Rain on Regional and Global Sea-Air Fluxes of CO2

    PubMed Central

    Shutler, J. D.; Land, P. E.; Woolf, D. K.; Quartly, G. D.

    2016-01-01

    The global oceans are considered a major sink of atmospheric carbon dioxide (CO2). Rain is known to alter the physical and chemical conditions at the sea surface, and thus influence the transfer of CO2 between the ocean and atmosphere. It can influence gas exchange through enhanced gas transfer velocity, the direct export of carbon from the atmosphere to the ocean, by altering the sea skin temperature, and through surface layer dilution. However, to date, very few studies quantifying these effects on global net sea-air fluxes exist. Here, we include terms for the enhanced gas transfer velocity and the direct export of carbon in calculations of the global net sea-air fluxes, using a 7-year time series of monthly global climate quality satellite remote sensing observations, model and in-situ data. The use of a non-linear relationship between the effects of rain and wind significantly reduces the estimated impact of rain-induced surface turbulence on the rate of sea-air gas transfer, when compared to a linear relationship. Nevertheless, globally, the rain enhanced gas transfer and rain induced direct export increase the estimated annual oceanic integrated net sink of CO2 by up to 6%. Regionally, the variations can be larger, with rain increasing the estimated annual net sink in the Pacific Ocean by up to 15% and altering monthly net flux by > ± 50%. Based on these analyses, the impacts of rain should be included in the uncertainty analysis of studies that estimate net sea-air fluxes of CO2 as the rain can have a considerable impact, dependent upon the region and timescale. PMID:27673683

  11. Observed screen (air) and GCM surface/screen temperatures: Implications for outgoing longwave fluxes at the surface

    SciTech Connect

    Garratt, J.R.

    1995-05-01

    There is direct evidence that excess net radiation calculated in general circulation models at continental surfaces (of about 11-17 W m{sup -2} (20%-27%) on an annual basis) is not only due to overestimates in annual incoming shortwave fluxes of 9-18 W m{sup -2} (6%-9%), but also to underestimates in outgoing longwave fluxes. THe bias in the outgoing longwave flux is deduced from a comparison of screen-air temperature observations, available as a global climatology of mean monthly values, and model-calculated surface and screen-air temperatures. An underestimate in the screen temperature computed in general circulation models over continents, of about 3 K on an annual basis, implies an underestimate in the outgoing longwave flux, averaged in six models under study, of 11-15 W m{sup -2} (3%-4%). For a set of 22 inland stations studied previously, the residual bias on an annual basis (the residual is the net radiation minus incoming shortwave plus outgoing longwave) varies between 18 and -23 W m{sup -2} for the models considered. Additional biases in one or both of the reflected shortwave and incoming longwave components cannot be ruled out. 13 refs., 3 figs., 5 tabs.

  12. Response of air-sea carbon fluxes and climate to orbital forcing changes in the Community Climate System Model

    NASA Astrophysics Data System (ADS)

    Jochum, M.; Peacock, S.; Moore, K.; Lindsay, K.

    2010-07-01

    A global general circulation model coupled to an ocean ecosystem model is used to quantify the response of carbon fluxes and climate to changes in orbital forcing. Compared to the present-day simulation, the simulation with the Earth's orbital parameters from 115,000 years ago features significantly cooler northern high latitudes but only moderately cooler southern high latitudes. This asymmetry is explained by a 30% reduction of the strength of the Atlantic Meridional Overturning Circulation that is caused by an increased Arctic sea ice export and a resulting freshening of the North Atlantic. The strong northern high-latitude cooling and the direct insolation induced tropical warming lead to global shifts in precipitation and winds to the order of 10%-20%. These climate shifts lead to regional differences in air-sea carbon fluxes of the same order. However, the differences in global net air-sea carbon fluxes are small, which is due to several effects, two of which stand out: first, colder sea surface temperature leads to a more effective solubility pump but also to increased sea ice concentration which blocks air-sea exchange, and second, the weakening of Southern Ocean winds that is predicted by some idealized studies occurs only in part of the basin, and is compensated by stronger winds in other parts.

  13. Soil-Air Mercury Flux near a Large Industrial Emission Source before and after Closure (Flin Flon, Manitoba, Canada).

    PubMed

    Eckley, Chris S; Blanchard, Pierrette; McLennan, Daniel; Mintz, Rachel; Sekela, Mark

    2015-08-18

    Prior to its closure, the base-metal smelter in Flin Flon, Manitoba, Canada was one of the North America's largest mercury (Hg) emission sources. Our project objective was to understand the exchange of Hg between the soil and the air before and after the smelter closure. Field and laboratory Hg flux measurements were conducted to identify the controlling variables and used for spatial and temporal scaling. Study results showed that deposition from the smelter resulted in the surrounding soil being enriched in Hg (up to 99 μg g(-1)) as well as other metals. During the period of smelter operation, air concentrations were elevated (30 ± 19 ng m(-3)), and the soil was a net Hg sink (daily flux: -3.8 ng m(-2) h(-1)). Following the smelter closure, air Hg(0) concentrations were reduced, and the soils had large emissions (daily flux: 108 ng m(-2) h(-1)). The annual scaling of soil Hg emissions following the smelter closure indicated that the landscape impacted by smelter deposition emitted or re-emitted almost 100 kg per year. Elevated soil Hg concentrations and emissions are predicted to continue for hundreds of years before background concentrations are re-established. Overall, the results indicate that legacy Hg deposition will continue to cycle in the environment long after point-source reductions.

  14. Variability in surface meteorology and air-sea fluxes due to cumulus convective systems observed during CINDY/DYNAMO

    NASA Astrophysics Data System (ADS)

    Yokoi, Satoru; Katsumata, Masaki; Yoneyama, Kunio

    2014-03-01

    This study examines the variability in surface meteorological parameters and air-sea heat fluxes due to cold pools emanating from cumulus convective systems observed over the tropical Indian Ocean in November 2011. In particular, this study focuses on convective systems that are spatially smaller than mesoscale convective systems in a southeasterly trade wind environment. Composite analyses of convectively active periods show an increase in the sensible heat flux by 15-20 W m-2 that is primarily attributed to an increase in the difference between the surface air temperature and sea surface temperature and an increase in the latent heat flux by 30-70 W m-2 due to enhanced surface wind speeds. A succession of convectively active periods leads to a greater influence than those occurring independently. The direction of the surface wind velocity anomaly due to cold pools tends to be close to that of the environmental wind velocity, resulting in an efficient enhancement of wind speed. This study also demonstrates the close relation between cold pool intensities and convective activity. In particular, two measures of cold pool intensity, a minimum surface air temperature and a maximum amount of surface wind speed enhancement, are correlated with each other and with the convective activity around the observation point measured by radar-estimated rainfall and radar echo coverage.

  15. Localization of Metal-Induced Gap States at the Metal-Insulator Interface: Origin of Flux Noise in SQUIDs and Superconducting Qubits

    NASA Astrophysics Data System (ADS)

    Choi, Sangkook; Lee, Dung-Hai; Louie, Steven G.; Clarke, John

    2010-03-01

    The origin of magnetic flux noise in dc Superconducting Quantum Interference Devices (SQUIDs) with a power spectrum scaling as 1/f (f is frequency) has been a puzzle for over 25 years. This noise limits both the low frequency performance of SQUIDs and the decoherence time of flux-sensitive superconducting qubits, making scaling-up for quantum computing problematic. Recent calculations and experiments indicate that the noise is generated by electrons that randomly reverse their spin directions. Their areal density of ˜ 5 x 10^17 m-2 is relatively insensitive to the nature of the superconductor and substrate. Here, we propose that the local magnetic moments originate in metal-induced gap states (MIGSs) localized by potential disorder at the metal-insulator interface. MIGSs are particularly sensitive to such disorder, so that the localized states have a Coulomb repulsion sufficiently large to make them singly occupied. Our calculations demonstrate that a modest level of disorder generates the required areal density of localized moments. This result suggests that magnetic flux noise could be reduced by fabricating superconductor-insulator interfaces with less disorder. Support: NSF DMR07-05941, US DOE De-AC02-05CH11231, Samsung Foundation, Teragrid, NERSC.

  16. Design of single-winding energy-storage reactors for dc-to-dc converters using air-gapped magnetic-core structures

    NASA Technical Reports Server (NTRS)

    Ohri, A. K.; Wilson, T. G.; Owen, H. A., Jr.

    1977-01-01

    A procedure is presented for designing air-gapped energy-storage reactors for nine different dc-to-dc converters resulting from combinations of three single-winding power stages for voltage stepup, current stepup and voltage stepup/current stepup and three controllers with control laws that impose constant-frequency, constant transistor on-time and constant transistor off-time operation. The analysis, based on the energy-transfer requirement of the reactor, leads to a simple relationship for the required minimum volume of the air gap. Determination of this minimum air gap volume then permits the selection of either an air gap or a cross-sectional core area. Having picked one parameter, the minimum value of the other immediately leads to selection of the physical magnetic structure. Other analytically derived equations are used to obtain values for the required turns, the inductance, and the maximum rms winding current. The design procedure is applicable to a wide range of magnetic material characteristics and physical configurations for the air-gapped magnetic structure.

  17. Theoretical model for diffusive greenhouse gas fluxes estimation across water-air interfaces measured with the static floating chamber method

    NASA Astrophysics Data System (ADS)

    Xiao, Shangbin; Wang, Chenghao; Wilkinson, Richard Jeremy; Liu, Defu; Zhang, Cheng; Xu, Wennian; Yang, Zhengjian; Wang, Yuchun; Lei, Dan

    2016-07-01

    Aquatic systems are sources of greenhouse gases on different scales, however the uncertainty of gas fluxes estimated using popular methods are not well defined. Here we show that greenhouse gas fluxes across the air-water interface of seas and inland waters are significantly underestimated by the currently used static floating chamber (SFC) method. We found that the SFC CH4 flux calculated with the popular linear regression (LR) on changes of gas concentration over time only accounts for 54.75% and 35.77% of the corresponding real gas flux when the monitoring periods are 30 and 60 min respectively based on the theoretical model and experimental measurements. Our results do manifest that nonlinear regression models can improve gas flux estimations, while the exponential regression (ER) model can give the best estimations which are close to true values when compared to LR. However, the quadratic regression model is proved to be inappropriate for long time measurements and those aquatic systems with high gas emission rate. The greenhouse gases effluxes emitted from aquatic systems may be much more than those reported previously, and models on future scenarios of global climate changes should be adjusted accordingly.

  18. Fluxes of lactate into, from, and among gap junction-coupled astrocytes and their interaction with noradrenaline.

    PubMed

    Hertz, Leif; Gibbs, Marie E; Dienel, Gerald A

    2014-01-01

    Lactate is a versatile metabolite with important roles in modulation of brain glucose utilization rate (CMRglc), diagnosis of brain-injured patients, redox- and receptor-mediated signaling, memory, and alteration of gene transcription. Neurons and astrocytes release and accumulate lactate using equilibrative monocarboxylate transporters that carry out net transmembrane transport of lactate only until intra- and extracellular levels reach equilibrium. Astrocytes have much faster lactate uptake than neurons and shuttle more lactate among gap junction-coupled astrocytes than to nearby neurons. Lactate diffusion within syncytia can provide precursors for oxidative metabolism and glutamate synthesis and facilitate its release from endfeet to perivascular space to stimulate blood flow. Lactate efflux from brain during activation underlies the large underestimation of CMRglc with labeled glucose and fall in CMRO2/CMRglc ratio. Receptor-mediated effects of lactate on locus coeruleus neurons include noradrenaline release in cerebral cortex and c-AMP-mediated stimulation of astrocytic gap junctional coupling, thereby enhancing its dispersal and release from brain. Lactate transport is essential for its multifunctional roles. PMID:25249930

  19. Fluxes of lactate into, from, and among gap junction-coupled astrocytes and their interaction with noradrenaline

    PubMed Central

    Hertz, Leif; Gibbs, Marie E.; Dienel, Gerald A.

    2014-01-01

    Lactate is a versatile metabolite with important roles in modulation of brain glucose utilization rate (CMRglc), diagnosis of brain-injured patients, redox- and receptor-mediated signaling, memory, and alteration of gene transcription. Neurons and astrocytes release and accumulate lactate using equilibrative monocarboxylate transporters that carry out net transmembrane transport of lactate only until intra- and extracellular levels reach equilibrium. Astrocytes have much faster lactate uptake than neurons and shuttle more lactate among gap junction-coupled astrocytes than to nearby neurons. Lactate diffusion within syncytia can provide precursors for oxidative metabolism and glutamate synthesis and facilitate its release from endfeet to perivascular space to stimulate blood flow. Lactate efflux from brain during activation underlies the large underestimation of CMRglc with labeled glucose and fall in CMRO2/CMRglc ratio. Receptor-mediated effects of lactate on locus coeruleus neurons include noradrenaline release in cerebral cortex and c-AMP-mediated stimulation of astrocytic gap junctional coupling, thereby enhancing its dispersal and release from brain. Lactate transport is essential for its multifunctional roles. PMID:25249930

  20. Ultra sub-wavelength surface plasmon confinement using air-gap, sub-wavelength ring resonator arrays

    NASA Astrophysics Data System (ADS)

    Lee, Jaehak; Sung, Sangkeun; Choi, Jun-Hyuk; Eom, Seok Chan; Mortensen, N. Asger; Shin, Jung H.

    2016-02-01

    Arrays of sub-wavelength, sub-10 nm air-gap plasmonic ring resonators are fabricated using nanoimprinting. In near infra-red (NIR) range, the resonator supports a single dipole mode which is excited and identified via simple normal illumination and explored through transmission measurements. By controlling both lateral and vertical confinement via a metal edge, the mode volume is successfully reduced down to 1.3 × 10‑5 λ03. The advantage of such mode confinement is demonstrated by applying the resonators biosensing. Using bovine serum albumin (BSA) molecules, a dramatic enhancement of surface sensitivity up to 69 nm/nm is achieved as the modal height approaches the thickness of the adsorbed molecule layers.

  1. Prediction of DC Corona Onset Voltage for Rod-Plane Air Gaps by a Support Vector Machine

    NASA Astrophysics Data System (ADS)

    Jin, Shuo; Ruan, Jiangjun; Du, Zhiye; Zhu, Lin; Shu, Shengwen

    2016-10-01

    This paper proposes a new method to predict the corona onset voltage for a rod-plane air gap, based on the support vector machine (SVM). Because the SVM is not limited by the size, dimension and nonlinearity of the samples, this method can realize accurate prediction with few training data. Only electric field features are chosen as the input; no geometric parameter is included. Therefore, the experiment data of one kind of electrode can be used to predict the corona onset voltages of other electrodes with different sizes. With the experimental data obtained by ozone detection technology, and experimental data provided by the reference, the efficiency of the proposed method is validated. Accurate predicted results with an average relative less than 3% are obtained with only 6 experimental data. supported by National Natural Science Foundation of China (No. 51477120)

  2. Ultra sub-wavelength surface plasmon confinement using air-gap, sub-wavelength ring resonator arrays

    PubMed Central

    Lee, Jaehak; Sung, Sangkeun; Choi, Jun-Hyuk; Eom, Seok Chan; Mortensen, N. Asger; Shin, Jung H.

    2016-01-01

    Arrays of sub-wavelength, sub-10 nm air-gap plasmonic ring resonators are fabricated using nanoimprinting. In near infra-red (NIR) range, the resonator supports a single dipole mode which is excited and identified via simple normal illumination and explored through transmission measurements. By controlling both lateral and vertical confinement via a metal edge, the mode volume is successfully reduced down to 1.3 × 10−5 λ03. The advantage of such mode confinement is demonstrated by applying the resonators biosensing. Using bovine serum albumin (BSA) molecules, a dramatic enhancement of surface sensitivity up to 69 nm/nm is achieved as the modal height approaches the thickness of the adsorbed molecule layers. PMID:26923610

  3. Dual rotor single- stator axial air gap PMSM motor/generator drive for high torque vehicles applications

    NASA Astrophysics Data System (ADS)

    Tutelea, L. N.; Deaconu, S. I.; Boldea, I.; Popa, G. N.

    2014-03-01

    The actual e - continuously variable transmission (e-CVT) solution for the parallel Hybrid Electric Vehicle (HEV) requires two electric machines, two inverters, and a planetary gear. A distinct electric generator and a propulsion electric motor, both with full power converters, are typical for a series HEV. In an effort to simplify the planetary-geared e-CVT for the parallel HEV or the series HEV we hereby propose to replace the basically two electric machines and their two power converters by a single, axial-air-gap, electric machine central stator, fed from a single PWM converter with dual frequency voltage output and two independent PM rotors, destined for hybrid electric vehicles (HEV) and military vehicles applications. The proposed topologies and the magneto-motive force analysis are the core of the paper.

  4. Estimation of Minimal Breakdown Point in a GaP Plasma Structure and Discharge Features in Air and Argon Media

    NASA Astrophysics Data System (ADS)

    Kurt, H. Hilal; Tanrıverdi, Evrim

    2016-08-01

    We present gas discharge phenomena in argon and air media using a gallium phosphide (GaP) semiconductor and metal electrodes. The system has a large-diameter ( D) semiconductor and a microscaled adjustable interelectrode gap ( d). Both theoretical and experimental findings are discussed for a direct-current (dc) electric field ( E) applied to this structure with parallel-plate geometry. As one of the main parameters, the pressure p takes an adjustable value from 0.26 kPa to 101 kPa. After collection of experimental data, a new theoretical formula is developed to estimate the minimal breakdown point of the system as a function of p and d. It is proven that the minimal breakdown point in the semiconductor and metal electrode system differs dramatically from that in metal and metal electrode systems. In addition, the surface charge density σ and spatial electron distribution n e are calculated theoretically. Current-voltage characteristics (CVCs) demonstrate that there exist certain negative differential resistance (NDR) regions for small interelectrode separations (i.e., d = 50 μm) and low and moderate pressures between 3.7 kPa and 13 kPa in Ar medium. From the difference of currents in CVCs, the bifurcation of the discharge current is clarified for an applied voltage U. Since the current differences in NDRs have various values from 1 μA to 7.24 μA for different pressures, the GaP semiconductor plasma structure can be used in microwave diode systems due to its clear NDR region.

  5. Reconstruction Of Air-Sea Fluxes And Meridional Transport Rates Of Anthropogenic Carbon With An Ensemble Kalman Filter Data Assimilation

    NASA Astrophysics Data System (ADS)

    Gerber, M.; Joos, F.; Vazquez Rodriguez, M.

    2007-12-01

    Regional air-sea fluxes and meridional transport of anthropogenic carbon are inferred by assimilating anthropogenic carbon concentrations within the ocean from different data-based reconstructions. An inverse, Ensemble Kalman Filter method with the Bern3D ocean model is applied. The Bern3D model (Müller et al., 2006) is a computationally-efficient, 3-dimensional coarse resolution ocean model. The Ensemble Kalman Filter (Evenson, 2003) is suited for the assimilation of spatially and temporally varying data into a range of models, for model tuning or for model initialization. Regional fluxes through the air-sea interface and meridional transport rates in the ocean are determined by minimizing deviations between the distributions of anthropogenic carbon from the GLODAP database (Key et al., 2004) and from the Bern3D ocean model in the Ensemble Kalman Filtering optimzation. The resulting anthropogenic carbon fluxes are in agreement with those from another ocean inversion study using the same GLODAP data (Mikaloff Fletcher et al., 2006). Transport uncertainties are addressed by utilizing different configuration of the Bern3D model. The inferred transport uncertainties are comparable in magnitude to the uncertainties obtained by Mikaloff Fletcher et al. The fields of anthropogenic carbon reconstructed with six different reconstruction methods: CFC-shortcut (Thomas et al., 2001), C-star (Gruber et al. 1996), IPSL (Lo Monaco et al., 2005), PHI-CT (Vazquez Rodriguez et al, submitted), TrOCA (Touratier et al., 2004), and TTD (Waugh et al., 2006) from four sections in the Atlantic are assimilated individually to investigate the influence of data uncertainties on the inferred fluxes. Deviations in the inferred fluxes from the different reconstruction methods are comparable or even larger than uncertainties arising from model transport uncertainties. For example, anthropogenic carbon uptake is more than twice as large for the IPSL reconstruction than for the PHI

  6. Air-gap gating of MgZnO/ZnO heterostructures

    SciTech Connect

    Tambo, T.; Falson, J. Kozuka, Y.; Maryenko, D.; Tsukazaki, A.; Kawasaki, M.

    2014-08-28

    The adaptation of “air-gap” dielectric based field-effect transistor technology to controlling the MgZnO/ZnO heterointerface confined two-dimensional electron system (2DES) is reported. We find it possible to tune the charge density of the 2DES via a gate electrode spatially separated from the heterostructure surface by a distance of 5 μm. Under static gating, the observation of the quantum Hall effect suggests that the charge carrier density remains homogeneous, with the 2DES in the 3 mm square sample the sole conductor. The availability of this technology enables the exploration of the charge carrier density degree of freedom in the pristine sample limit.

  7. [Comparative study on water-air CO2, CH4 flux in two tributaries in the Three Gorges Reservoir, China].

    PubMed

    Li, Zhe; Bai, Lei; Guo, Jin-Song; Fang, Fang; Jiang, Tao

    2013-03-01

    The Three Gorges Reservoir (TGR) is a huge reservoir under the subtropical climate condition. It shows great spatio-temporal heterogeneity on biogeochemical cycling of carbon in the TGR's aquatic ecosystem. 1 a field monitoring on water-air CO2 and CH4 fluxes was conducted from June, 2010 to May, 2011 in Longxi River and Pengxi River, the 2 typical tributaries in the Three Gorges Reservoir. Comparative study showed that annual CO2 diffusive fluxes in the Longxi River and Pengxi River were (7.30 +/- 1.89) mmol x (m2 x h)(-1) and (0.71 +/- 0.46) mmol x (m2 x h)(-1), respectively, and the CH4 diffusive fluxes were (0.11 +/- 0.095) mmol x (m2 x h)(-1) and (0.007 4 +/- 0.001 7) mmol x (m2 x h)(-1). Higher intensities and seasonal variance of CO2 and CH4 fluxes were observed in Longxi River compared to those in Pengxi River. Through a comparative analysis of the environmental and watershed parameters in both rivers, it was found that the unstable hydraulic conditions and habitat of Longxi River prohibited the growth of phytoplankton, reducing its capability of carbon assimilation. The higher pollution load in the basin and the higher organic matters and total nitrogen in the impounding soil of Longxi River also resulted in the higher level of greenhouse gas fluxes compared to those in the Pengxi River. More studies shall be conducted to elucidate the variance of CH4 flux and its controlling factors in both rivers.

  8. Enhancement of magnetic flux distribution in a DC superconducting electric motor

    NASA Astrophysics Data System (ADS)

    Hamid, N. A.; Ewe, L. S.; Chin, K. M.

    2013-06-01

    Most motor designs require an air gap between the rotor and stator to enable the armature to rotate freely. The interaction of magnetic flux from rotor and stator within the air gap will provide the thrust for rotational motion. Thus, the understanding of magnetic flux in the vicinity of the air gap is very important to mathematically calculate the magnetic flux generated in the area. In this work, a finite element analysis was employed to study the behavior of the magnetic flux in view of designing a synchronous DC superconducting electric motor. The analysis provides an ideal magnetic flux distribution within the components of the motor. From the flux plot analysis, it indicates that flux losses are mainly in the forms of leakage and fringe effect. The analysis also shows that the flux density is high at the area around the air gap and the rotor. The high flux density will provide a high force area that enables the rotor to rotate. In contrast, the other parts of the motor body do not show high flux density indicating low distribution of flux. Consequently, a bench top model of a DC superconducting motor was developed where by motor with a 2-pole type winding was chosen. Each field coil was designed with a racetrack-shaped double pancake wound using DI-BSCCO Bi-2223 superconducting tapes. The performance and energy efficiency of the superconducting motor was superior when compared to the conventional motor with similar capacity.

  9. Resistance modulation in VO2 nanowires induced by an electric field via air-gap gates

    NASA Astrophysics Data System (ADS)

    Kanki, Teruo; Chikanari, Masashi; Wei, Tingting; Tanaka, Hidekazu; The Institute of Scientific; Industrial Research Team

    Vanadium dioxide (VO2) shows huge resistance change with metal-insulator transition (MIT) at around room temperature. Controlling of the MIT by applying an electric field is a topical ongoing research toward the realization of Mott transistor. In this study, we have successfully switched channel resistance of VO2 nano-wire channels by a pure electrostatic field effect using a side-gate-type field-effect transistor (SG-FET) viaair gap and found that single crystalline VO2 nanowires and the channels with narrower width enhance transport modulation rate. The rate of change in resistance ((R0-R)/R, where R0 and R is the resistance of VO2 channel with off state and on state gate voltage (VG) , respectively) was 0.42 % at VG = 30 V in in-plane poly-crystalline VO2 channels on Al2O3(0001) substrates, while the rate in single crystalline channels on TiO2 (001) substrates was 3.84 %, which was 9 times higher than that using the poly-crystalline channels. With reducing wire width from 3000 nm to 400 nm of VO2 on TiO2 (001) substrate, furthermore, resistance modulation ratio enhanced from 0.67 % to 3.84 %. This change can not be explained by a simple free-electron model. In this presentation, we will compare the electronic properties between in-plane polycrystalline VO2 on Al2O3 (0001) and single crystalline VO2 on TiO2 (001) substrates, and show experimental data in detail..

  10. Similarity laws for cathode-directed streamers in gaps with an inhomogeneous field at elevated air pressures

    SciTech Connect

    Bolotov, O. V.; Golota, V. I.; Kadolin, B. B.; Karas', V. I.; Ostroushko, V. N.; Zavada, L. M.; Shulika, A. Yu.

    2010-11-15

    Results are presented from experimental studies of cathode-directed streamers in the gap closure regime without a transition into spark breakdown. Spatiotemporal, electrodynamic, and spectroscopic characteristics of streamer discharges in air at different pressures were studied. Similarity laws for streamer discharges were formulated. These laws allow one to compare the discharge current characteristics and streamer propagation dynamics at different pressures. Substantial influence of gas photoionization on the deviations from the similarity laws was revealed. The existence of a pressure range in which the discharges develop in a similar way was demonstrated experimentally. In particular, for fixed values of the product pd and discharge voltage U, the average streamer velocity is also fixed. It is found that, although the similarity laws are violated in the interstreamer pause of the discharge, the average discharge current and the product of the pressure and the streamer repetition period remain the same at different pressures. The radiation spectra of the second positive system of nitrogen (the C{sup 3{Pi}}{sub u}-B{sup 3{Pi}}{sub g} transitions) in a wavelength range of 300-400 nm at air pressures of 1-3 atm were recorded. It is shown that, in the entire pressure range under study, the profiles of the observed radiation bands practically remain unchanged and the relative intensities of the spectral lines corresponding to the {sup 3{Pi}}{sub u}-B{sup 3{Pi}}{sub g} transitions are preserved.

  11. From pores to eddies - linking diffusion-based evaporative fluxes from porous surfaces with a turbulent air boundary layer

    NASA Astrophysics Data System (ADS)

    Haghighi, E.; Or, D.

    2012-04-01

    Evaporation affects hydration and energy balance of terrestrial surfaces. Evaporation rates exhibit complex dynamics reflecting interactions between external conditions and internal transport properties of a the drying porous surface Motivated by recent progress in estimating evaporative fluxes from isolated pores across laminar air sublayer, we seek to expand the description and quantify evaporation across a turbulent boundary layer. We adopt concepts from surface renewal (SR) theory focusing on turbulent exchange with individual eddies and linking eddies surface footprint and their local boundary layer over patches of a drying surface. The model resolves diffusive exchange during limited residence time and integrates fluxes over the entire surface to quantify mean evaporative fluxes from drying surfaces into turbulent airflows accounting for subsurface internal transport processes and diffusive exchanges. Input parameters and model evaluation would be based on data from spatially and temporally resolved Infrared (IR) thermography of drying surfaces under prescribe turbulent regimes conducted in a wind-tunnel experiment. The study provides basic ingredients and building blocks essential for upscaling the results to estimation of evaporative fluxes at the field and landscape scales. Keywords: Evaporation; Turbulent Coupling; Surface Renewal; Infrared Imaging.

  12. Annual and seasonal fCO2 and air-sea CO2 fluxes in the Barents Sea

    NASA Astrophysics Data System (ADS)

    Lauvset, S. K.; Chierici, M.; Counillon, F.; Omar, A.; Nondal, G.; Johannessen, T.; Olsen, A.

    2013-03-01

    The Barents Sea is the strongest CO2 sink in the Arctic region, yet estimates of the air-sea CO2 flux in this area show a large span reflecting uncertainty as well as significant variability both seasonally and regionally. Here we use a previously unpublished data set of seawater CO2 fugacity (fCO2), and map these data over the western Barents Sea through multivariable linear regressions with SeaWiFS/MODIS remote sensing and TOPAZ model data fields. We find that two algorithms are necessary in order to cover the full seasonal cycle, mainly because not all proxy variables are available for the entire year, and because variability in fCO2 is driven by different mechanisms in summer and winter. A comprehensive skill assessment indicates that there is a good overall correspondence between observations and predictions. The algorithms are also validated using two independent data sets, with good results. The gridded fCO2 fields reveal tight links between water mass distribution and fCO2 in all months, and particularly in winter. The seasonal cycle show peaks in the total air-sea CO2 influx in May and September, caused by respectively biological drawdown of CO2 and low sea ice concentration leaving a large open water area. For 2007 the annual average air-sea CO2 flux is - 48 ± 5 gC m- 2, which is comparable to previous estimates.

  13. Dissolved methane concentration profiles and air-sea fluxes from 41°S to 27°N

    NASA Astrophysics Data System (ADS)

    Kelley, Cheryl A.; Jeffrey, Wade H.

    2002-07-01

    Water column samples from a transect cruise from southern Chile through the Panama Canal to the Gulf of Mexico were used to determine dissolved methane depth profiles and air-sea methane fluxes. In the Gulf of Mexico, surface concentrations were approximately 40% supersaturated with respect to the atmosphere, whereas near the equator and in the Peru upwelling region, 10-20% supersaturation generally occurred. These saturation ratios translate into an average flux of methane from the sea surface to the atmosphere of 0.38 μmol m-2 d-1. In addition, water column profiles of dissolved methane indicate that subsurface maxima in dissolved methane concentrations are a consistent feature of the open ocean, except near the equator. At the equator, the subsurface peak at the base of the mixed layer may be bowed down by the Equatorial Undercurrent. The highest methane concentration (12 nM) was observed in the Peru upwelling region.

  14. Carbon budgets for three autotrophic Australian estuaries: Implications for global estimates of the coastal air-water CO2 flux

    NASA Astrophysics Data System (ADS)

    Maher, D. T.; Eyre, B. D.

    2012-03-01

    Estuaries are `hot spots' in the global carbon cycle, yet data on carbon dynamics, in particular air-sea CO2 fluxes, from autotrophic systems are rare. Estuarine carbon budgets were constructed for three geomorphically distinct warm temperate Australian estuaries over an annual cycle. All three estuaries were net autotrophic, with annual net ecosystem metabolism (NEM) ranging from 8 ± 13.4 molC m-2 yr-1 to 10 ± 14 molC m-2 yr-1. There was a net flux of CO2 from the atmosphere to the estuaries of between 0.4 ± 0.6 molC m-2 yr-1 and 2 ± 0.9 molC m-2 yr-1. Loading of dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC) to the estuaries varied markedly within and between the estuaries, and was directly related to freshwater inflow. While NEM was similar in all three estuaries, the ratio of benthic versus pelagic contributions to NEM differed, with NEM dominated by pelagic production in the river dominated system, benthic production dominating in the intermediate estuary, and equal contributions of benthic and pelagic production in the marine dominated lagoon. All three estuaries exported more organic carbon than was imported, fueled by additional organic carbon supplied by NEM. The estuaries essentially acted as bioreactors, transforming DIC to organic carbon. Burial of organic carbon ranged from 1.2 ± 0.3 molC m-2 yr-1 to 4.4 ± 1.2 molC m-2 yr-1 and represented up to half of NEM. The annual net uptake of atmospheric CO2 in these systems, along with previous estimates of the global estuarine CO2flux being based predominantly on heterotrophic, large river dominated estuarine systems, indicates that the global estimate of the estuarine air-water CO2flux may be over-estimated due to the lack of studies from autotrophic marine dominated estuaries.

  15. Parameterization of Sea-Spray Impact on Air-Sea Momentum and Heat Fluxes in Hurricane Prediction Models

    NASA Astrophysics Data System (ADS)

    Bao, Jian-Wen; Fairall, Chris; Michelson, Sara; Bianco, Laura

    2010-05-01

    Although it is widely recognized that sea spray under hurricane-strength winds is omnipresent in the marine surface boundary layer (MSBL), how to parameterize the effects of sea spray on the air-sea momentum and heat fluxes at hurricane-strength winds in numerical weather prediction (NWP) models still remains a subject of research. This paper focuses on how the effects of sea spray on the momentum and heat fluxes are parameterized in NWP models using the Monin-Obukhov similarity theory. In this scheme, the effects of sea spray can be considered as an additional modification to the stratification of the near surface profiles of wind, temperature and moisture in the MSBL. The overall impact of sea-spray droplets on the mean profiles of wind, temperature and moisture depends on the wind speed at the level of sea-spray generation (or wave state if available). As the wind speed increases, the droplet size increases, rendering an increase in the spray-mediated total enthalpy flux from the sea to the air and leveling off of the surface drag. When the wind is below 35 ms-1, the droplets are small in size and tend to evaporate substantially and thus cool the spray-filled layer. When the wind is above 50 ms-1, the size of droplets is so big that they do not have enough time to evaporate that much before falling back into the sea. Furthermore, the scheme includes the physics of the suspended sea-spray droplets reducing the buoyancy of the MSBL air, therefore making the surface layer more stable. Results from testing the scheme in a numerical weather prediction model are presented along with a dynamical interpretation of the impact of sea spray on the intensification of tropical cyclones.

  16. Air-water fluxes of N₂O and CH₄ during microalgae (Staurosira sp.) cultivation in an open raceway pond.

    PubMed

    Ferrón, Sara; Ho, David T; Johnson, Zackary I; Huntley, Mark E

    2012-10-01

    The industrial-scale production of biofuels from cultivated microalgae has gained considerable interest in the last several decades. While the climate benefits of microalgae cultivation that result from the capture of atmospheric CO(2) are known, the counteracting effect from the potential emission of other greenhouse gases has not been well quantified. Here, we report the results of a study conducted at an industrial pilot facility in Hawaii to determine the air-water fluxes of N(2)O and CH(4) from open raceway ponds used to grow the marine diatom Staurosira sp. as a feedstock for biofuel. Dissolved O(2), CH(4), and N(2)O concentrations were measured over a 24 h cycle. During this time, four SF(6) tracer release experiments were conducted to quantify gas transfer velocities in the ponds, and these were then used to calculate air-water fluxes. Our results show that pond waters were consistently supersaturated with CH(4) (up to 725%) resulting in an average emission of 19.9 ± 5.6 μmol CH(4) m(-2) d(-1). Upon NO(3)(-) depletion, the pond shifted from being a source to being a sink of N(2)O, with an overall net uptake during the experimental period of 3.4 ± 3.5 μmol N(2)O m(-2) d(-1). The air-water fluxes of N(2)O and CH(4) expressed as CO(2) equivalents of global warming potential were 2 orders of magnitude smaller than the overall CO(2) uptake by the microalgae.

  17. Assessing the potential for dimethylsulfide enrichment at the sea surface and its influence on air-sea flux

    NASA Astrophysics Data System (ADS)

    Walker, Carolyn F.; Harvey, Mike J.; Smith, Murray J.; Bell, Thomas G.; Saltzman, Eric S.; Marriner, Andrew S.; McGregor, John A.; Law, Cliff S.

    2016-09-01

    The flux of dimethylsulfide (DMS) to the atmosphere is generally inferred using water sampled at or below 2 m depth, thereby excluding any concentration anomalies at the air-sea interface. Two independent techniques were used to assess the potential for near-surface DMS enrichment to influence DMS emissions and also identify the factors influencing enrichment. DMS measurements in productive frontal waters over the Chatham Rise, east of New Zealand, did not identify any significant gradients between 0.01 and 6 m in sub-surface seawater, whereas DMS enrichment in the sea-surface microlayer was variable, with a mean enrichment factor (EF; the concentration ratio between DMS in the sea-surface microlayer and in sub-surface water) of 1.7. Physical and biological factors influenced sea-surface microlayer DMS concentration, with high enrichment (EF > 1.3) only recorded in a dinoflagellate-dominated bloom, and associated with low to medium wind speeds and near-surface temperature gradients. On occasion, high DMS enrichment preceded periods when the air-sea DMS flux, measured by eddy covariance, exceeded the flux calculated using National Oceanic and Atmospheric Administration (NOAA) Coupled-Ocean Atmospheric Response Experiment (COARE) parameterized gas transfer velocities and measured sub-surface seawater DMS concentrations. The results of these two independent approaches suggest that air-sea emissions may be influenced by near-surface DMS production under certain conditions, and highlight the need for further study to constrain the magnitude and mechanisms of DMS production in the sea-surface microlayer.

  18. Error Analysis of Clay-Rock Water Content Estimation with Broadband High-Frequency Electromagnetic Sensors—Air Gap Effect

    PubMed Central

    Bore, Thierry; Wagner, Norman; Delepine Lesoille, Sylvie; Taillade, Frederic; Six, Gonzague; Daout, Franck; Placko, Dominique

    2016-01-01

    Broadband electromagnetic frequency or time domain sensor techniques present high potential for quantitative water content monitoring in porous media. Prior to in situ application, the impact of the relationship between the broadband electromagnetic properties of the porous material (clay-rock) and the water content on the frequency or time domain sensor response is required. For this purpose, dielectric properties of intact clay rock samples experimental determined in the frequency range from 1 MHz to 10 GHz were used as input data in 3-D numerical frequency domain finite element field calculations to model the one port broadband frequency or time domain transfer function for a three rods based sensor embedded in the clay-rock. The sensor response in terms of the reflection factor was analyzed in time domain with classical travel time analysis in combination with an empirical model according to Topp equation, as well as the theoretical Lichtenecker and Rother model (LRM) to estimate the volumetric water content. The mixture equation considering the appropriate porosity of the investigated material provide a practical and efficient approach for water content estimation based on classical travel time analysis with the onset-method. The inflection method is not recommended for water content estimation in electrical dispersive and absorptive material. Moreover, the results clearly indicate that effects due to coupling of the sensor to the material cannot be neglected. Coupling problems caused by an air gap lead to dramatic effects on water content estimation, even for submillimeter gaps. Thus, the quantitative determination of the in situ water content requires careful sensor installation in order to reach a perfect probe clay rock coupling. PMID:27096865

  19. Error Analysis of Clay-Rock Water Content Estimation with Broadband High-Frequency Electromagnetic Sensors--Air Gap Effect.

    PubMed

    Bore, Thierry; Wagner, Norman; Lesoille, Sylvie Delepine; Taillade, Frederic; Six, Gonzague; Daout, Franck; Placko, Dominique

    2016-01-01

    Broadband electromagnetic frequency or time domain sensor techniques present high potential for quantitative water content monitoring in porous media. Prior to in situ application, the impact of the relationship between the broadband electromagnetic properties of the porous material (clay-rock) and the water content on the frequency or time domain sensor response is required. For this purpose, dielectric properties of intact clay rock samples experimental determined in the frequency range from 1 MHz to 10 GHz were used as input data in 3-D numerical frequency domain finite element field calculations to model the one port broadband frequency or time domain transfer function for a three rods based sensor embedded in the clay-rock. The sensor response in terms of the reflection factor was analyzed in time domain with classical travel time analysis in combination with an empirical model according to Topp equation, as well as the theoretical Lichtenecker and Rother model (LRM) to estimate the volumetric water content. The mixture equation considering the appropriate porosity of the investigated material provide a practical and efficient approach for water content estimation based on classical travel time analysis with the onset-method. The inflection method is not recommended for water content estimation in electrical dispersive and absorptive material. Moreover, the results clearly indicate that effects due to coupling of the sensor to the material cannot be neglected. Coupling problems caused by an air gap lead to dramatic effects on water content estimation, even for submillimeter gaps. Thus, the quantitative determination of the in situ water content requires careful sensor installation in order to reach a perfect probe clay rock coupling. PMID:27096865

  20. Error Analysis of Clay-Rock Water Content Estimation with Broadband High-Frequency Electromagnetic Sensors--Air Gap Effect.

    PubMed

    Bore, Thierry; Wagner, Norman; Lesoille, Sylvie Delepine; Taillade, Frederic; Six, Gonzague; Daout, Franck; Placko, Dominique

    2016-04-18

    Broadband electromagnetic frequency or time domain sensor techniques present high potential for quantitative water content monitoring in porous media. Prior to in situ application, the impact of the relationship between the broadband electromagnetic properties of the porous material (clay-rock) and the water content on the frequency or time domain sensor response is required. For this purpose, dielectric properties of intact clay rock samples experimental determined in the frequency range from 1 MHz to 10 GHz were used as input data in 3-D numerical frequency domain finite element field calculations to model the one port broadband frequency or time domain transfer function for a three rods based sensor embedded in the clay-rock. The sensor response in terms of the reflection factor was analyzed in time domain with classical travel time analysis in combination with an empirical model according to Topp equation, as well as the theoretical Lichtenecker and Rother model (LRM) to estimate the volumetric water content. The mixture equation considering the appropriate porosity of the investigated material provide a practical and efficient approach for water content estimation based on classical travel time analysis with the onset-method. The inflection method is not recommended for water content estimation in electrical dispersive and absorptive material. Moreover, the results clearly indicate that effects due to coupling of the sensor to the material cannot be neglected. Coupling problems caused by an air gap lead to dramatic effects on water content estimation, even for submillimeter gaps. Thus, the quantitative determination of the in situ water content requires careful sensor installation in order to reach a perfect probe clay rock coupling.

  1. Sensitivity of Global Sea-Air CO2 Flux to Gas Transfer Algorithms, Climatological Wind Speeds, and Variability of Sea Surface Temperature and Salinity

    NASA Technical Reports Server (NTRS)

    McClain, Charles R.; Signorini, Sergio

    2002-01-01

    Sensitivity analyses of sea-air CO2 flux to gas transfer algorithms, climatological wind speeds, sea surface temperatures (SST) and salinity (SSS) were conducted for the global oceans and selected regional domains. Large uncertainties in the global sea-air flux estimates are identified due to different gas transfer algorithms, global climatological wind speeds, and seasonal SST and SSS data. The global sea-air flux ranges from -0.57 to -2.27 Gt/yr, depending on the combination of gas transfer algorithms and global climatological wind speeds used. Different combinations of SST and SSS global fields resulted in changes as large as 35% on the oceans global sea-air flux. An error as small as plus or minus 0.2 in SSS translates into a plus or minus 43% deviation on the mean global CO2 flux. This result emphasizes the need for highly accurate satellite SSS observations for the development of remote sensing sea-air flux algorithms.

  2. [Distribution and air-sea fluxes of methane in the Yellow Sea and the East China Sea in the spring].

    PubMed

    Cao, Xing-Peng; Zhang, Gui-Ling; Ma, Xiao; Zhang, Guo-Ling; Liu, Su-Mei

    2013-07-01

    A survey was carried out in the Yellow Sea and the East China Sea from March 17 to April 06 of 2011. Dissolved CH4 in various depths were measured and sea-to-air fluxes were estimated. Methane concentrations in surface and bottom waters ranged between 2.39-29.67 nmol x L(-1) and 2.63-30.63 nmol x L(-1), respectively. Methane concentrations in bottom waters were slightly higher than those in surface waters, suggesting the existence of methane source in bottom waters or sediments. The horizontal distribution of dissolved CH4 showed a decrease from the river mouth to the open sea, and was influenced by the freshwater discharge and the Kuroshio intrusion. Surface methane saturations ranged from 93%-1 038%. Sea to air CH4 fluxes were (2.85 +/- 5.11) micromol x (m2 x d)(-1) (5.18 +/- 9.99) micromol x (m2 x d)(-1) respectively, calculated using the Liss and Merlivat (LM86), the Wanninkhof (W92) relationships and in situ wind speeds, and estimated emission rates of methane from the East China Sea and the Yellow Sea range from 7.05 x 10(-2) - 12.0 x 10(-2) Tg x a(-1) and 1.17 x 10(-2) - 2.20 x 10(-2) Tg x a(-1), respectively. The Yellow Sea and East China Sea are the net sources of atmospheric methane in the spring.

  3. SST, Winds, and Air-Sea Fluxes in the Gulf Stream Region in the First Winter of CLIMODE

    NASA Astrophysics Data System (ADS)

    Kelly, K. A.; Dickinson, S.; Jones, H. R.

    2006-12-01

    The NSF sponsored CLIvar MOde Water Dynamic Experiment (CLIMODE) focuses on the wintertime processes responsible for the formation and dispersal of Eighteen Degree Water (EDW), the subtropical mode water of the North Atlantic. This region has the largest wintertime loss of heat from the ocean to the atmosphere, made possible by the influx of heat from the Gulf Stream (GS). These fluxes fuel the formation and intensification of storms, as cool, dry continental air encounters the warm boundary current waters. The actual impact of the large transfers of heat on the ocean and on the atmosphere are likely underestimated in weather and climate models, owing to poor observational input and inaccurate boundary layer physics. Several new sources of data are available with which to examine the relationship between the Gulf Stream, air-sea heat fluxes, winds, and storms: wind vector and SST measurements from satellites, as well as in situ measurements, including data from CLIMODE. Improved satellite data includes the ocean vector winds from QuikSCAT, re-processed at a spatial resolution of 12.5km, and microwave SST from AMSR-E. Although the microwave resolution is coarser than for infrared SST, the ability of microwave sensors to see through clouds gives better effective resolution of SST, particularly during storms. Two CLIMODE cruises were conducted in the winter of 2005-2006. During the first cruise in November 2005, SST dropped by about 1.5-2C, leaving SST in the recirculation region at about 22C. By the start of the second cruise in January 2006, SST had fallen to 20C near the GS core, and 19C in the mode water region. By the end of the second cruise 2 weeks later, the region of 20C water had dropped to 19C, suggesting that EDW formation was imminent. SST in the mode water region reached 18C the following week. Maximum wind speeds were distinctly centered on the GS warm core for much of January 2006. Recent studies suggest that the Gulf Stream could affect the storm

  4. A comparative study on the effects of air gap wind and walking motion on the thermal properties of Arabian Thawbs and Chinese Cheongsams.

    PubMed

    Cui, Zhiying; Fan, Jintu; Wu, Yuenshing

    2016-08-01

    This paper reports on an experimental investigation on the effects of air gap, wind and walking motion on the thermal properties of traditional Arabian thawbs and Chinese cheongsams. Total thermal resistance (It) and vapour resistance (Re) were measured using the sweating fabric manikin - 'Walter', and the air gap volumes of the garments were determined by a 3D body scanner. The results showed the relative changes of It and Re of thawbs due to wind and walking motion are greater than those of cheongsams, which provided an explanation of why thawbs are preferred in extremely hot climate. It is further shown that thermal insulation and vapour resistance of thawbs increase with the air gap volume up to about 71,000 cm(3) and then decrease gradually. Thawbs with higher air permeability have significantly lower evaporative resistance particularly under windy conditions demonstrating the advantage of air permeable fabrics in body cooling in hot environments. Practitioner Summary: This paper aims to better understand the thermal insulation and vapour resistance of traditional Arabian thawbs and Chinese cheongsams, and the relationship between the thermal properties and their fit and design. The results of this study provide a scientific basis for designing ethnic clothing used in hot environments.

  5. Climate simulations with a new air-sea turbulent flux parameterization in the National Center for Atmospheric Research Community Atmosphere Model (CAM3)

    NASA Astrophysics Data System (ADS)

    Ban, Junmei; Gao, Zhiqiu; Lenschow, Donald H.

    2010-01-01

    This study examines climate simulations with the National Center for Atmospheric Research Community Atmosphere Model version 3 (NCAR CAM3) using a new air-sea turbulent flux parameterization scheme. The current air-sea turbulent flux scheme in CAM3 consists of three basic bulk flux equations that are solved simultaneously by an iterative computational technique. We recently developed a new turbulent flux parameterization scheme where the Obukhov stability length is parameterized directly by using a bulk Richardson number, an aerodynamic roughness length, and a heat roughness length. Its advantages are that it (1) avoids the iterative process and thus increases the computational efficiency, (2) takes account of the difference between z0m and z0h and allows large z0m/z0h, and (3) preserves the accuracy of iteration. An offline test using Tropical Ocean-Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE) data shows that the original scheme overestimates the surface fluxes under very weak winds but the new scheme gives better results. Under identical initial and boundary conditions, the original CAM3 and CAM3 coupled with the new turbulent flux scheme are used to simulate the global distribution of air-sea surface turbulent fluxes, and precipitation. Comparisons of model outputs against the European Remote Sensing Satellites (ERS), the Objectively Analyzed air-sea Fluxes (OAFlux), and Climate Prediction Center (CPC) Merged Analysis of Precipitation (CMAP) show that: (1) the new scheme produces more realistic surface wind stress in the North Pacific and North Atlantic trade wind belts and wintertime extratropical storm track regions; (2) the latent heat flux in the Northern Hemisphere trade wind zones shows modest improvement in the new scheme, and the latent heat flux bias in the western boundary current region of the Gulf Stream is reduced; and (3) the simulated precipitation in the new scheme is closer to observation in the Asian monsoon

  6. The effect of coronae on leader initiation and development under thunderstorm conditions and in long air gaps

    NASA Astrophysics Data System (ADS)

    Aleksandrov, N. L.; Bazelyan, E. M.; Carpenter, R. B., Jr.; Drabkin, M. M.; Raizer, Yu P.

    2001-11-01

    The initiation and development of a leader is theoretically studied by considering an electrode which is embedded in a cloud of space charge injected by a corona discharge. The focus is on the initiation of upward lightning from a stationary grounded object in a thundercloud electric field. The main results are also applicable to the leader process in long laboratory air gaps at direct voltage. Simple physical models of non-stationary coronae developing in free space near a solitary stressed sphere and of a leader propagating in the space charge cloud of coronae are suggested. It is shown that the electric field redistribution due to the space charge released by the long corona discharge near the top of a high object hinders the initiation and development of an upward leader from the object in a thundercloud electric field. The conditions for the formation of corona streamers that are required to initiate a leader are derived. The criteria are obtained for a leader to be initiated and propagate in the space charge cloud. A hypothesis is proposed that the streamers are never initiated near the top of a high object under thunderstorm conditions if at ground level there is only a slowly-varying electric field of the thundercloud. The streamers may be induced by the fast-rising electric field of distant downward leaders or intracloud discharges.

  7. A Coupled Multiphase Fluid Flow And Heat And Vapor Transport Model For Air-Gap Membrane Distillation

    NASA Astrophysics Data System (ADS)

    Mukhopadhyay, Sumit

    2010-05-01

    Membrane distillation (MD) is emerging as a viable desalination technology because of its low energy requirements that can be provided from low-grade, waste heat and because it causes less fouling. In MD, desalination is accomplished by transporting water vapour through a porous hydrophobic membrane. The vapour transport process is governed by the vapour pressure difference between the two sides of a membrane. A variety of configurations have been tested to impose this vapour pressure gradient, however, the air-gap membrane distillation (AGMD) has been found to be the most efficient. The separation mechanism of AGMD and its overall efficiency is based on vapour-liquid equilibrium (VLE). At present, little knowledge is available about the optimal design of such a transmembrane VLE-based evaporation, and subsequent condensation processes. While design parameters for MD have evolved mostly through experimentations, a comprehensive mathematical model is yet to be developed. This is primarily because the coupling and non-linearity of the equations, the interactions between the flow, heat and mass transport regimes, and the complex geometries involved pose a challenging modelling and simulation problem. Yet a comprehensive mathematical model is needed for systematic evaluation of the processes, design parameterization, and performance prediction. This paper thus presents a coupled fluid flow, heat and mass transfer model to investigate the main processes and parameters affecting the performance of an AGMD.

  8. The health impacts of exposure to indoor air pollution from solid fuels in developing countries: knowledge, gaps, and data needs.

    PubMed Central

    Ezzati, Majid; Kammen, Daniel M

    2002-01-01

    Globally, almost 3 billion people rely on biomass (wood, charcoal, crop residues, and dung) and coal as their primary source of domestic energy. Exposure to indoor air pollution (IAP) from the combustion of solid fuels is an important cause of morbidity and mortality in developing countries. In this paper, we review the current knowledge on the relationship between IAP exposure and disease and on interventions for reducing exposure and disease. We take an environmental health perspective and consider the details of both exposure and health effects that are needed for successful intervention strategies. We also identify knowledge gaps and detailed research questions that are essential in successful design and dissemination of preventive measures and policies. In addition to specific research recommendations, we conclude that given the interaction of housing, household energy, and day-to-day household activities in determining exposure to indoor smoke, research and development of effective interventions can benefit tremendously from integration of methods and analysis tools from a range of disciplines in the physical, social, and health sciences. PMID:12417475

  9. Temperature dependence of beat-length and confinement loss in an air-core photonic band-gap fiber

    NASA Astrophysics Data System (ADS)

    Xu, Zhenlong; Li, Xuyou; Hong, Yong; Liu, Pan; Yang, Hanrui; Ling, Weiwei

    2016-05-01

    The temperature dependence of polarization-maintaining (PM) property and loss in a highly-birefringent air-core photonic band-gap fiber (PBF) is investigated. The effects of temperature variation on the effective index, beat-length and confinement loss are studied numerically by using the full-vector finite element method (FEM). It is found that, the PM property of this PBF is insensitive to the temperature, and the temperature-dependent beat-length coefficient can be as low as 2.86×10-8 m/°C, which is typically 200 times less than those of conventional panda fibers, the PBF has a stable confinement loss of 0.01 dB/m over the temperature range of -30 to 20 °C for the slow axis at the wavelength of 1.55 μm. The PBF with ultra-low temperature-dependent PM property and low loss can reduce the thermally induced polarization instability apparently in interferometric applications such as resonant fiber optic gyroscope (RFOG), optical fiber sensors, and so on.

  10. Indium phosphide all air-gap Fabry-Pérot filters for near-infrared spectroscopic applications

    NASA Astrophysics Data System (ADS)

    Ullah, A.; Butt, M. A.; Fomchenkov, S. A.; Khonina, S. N.

    2016-08-01

    Food quality can be characterized by noninvasive techniques such as spectroscopy in the Near Infrared wavelength range. For example, 930 -1450 nm wavelength range can be used to detect diseases and differentiate between meat samples. Miniaturization of such NIR spectrometers is useful for quick and mobile characterization of food samples. Spectrometers can be miniaturized, without compromising the spectral resolution, using Fabry-Pérot (FP) filters consisting of two highly reflecting mirrors with a central cavity in between. The most commonly used mirrors in the design of FP filters are Distributed Bragg Reflections (DBRs) consisting of alternating high and low refractive index material pairs, due to their high reflectivity compared to metal mirrors. However, DBRs have high reflectivity for a selected range of wavelengths known as the stopband of the DBR. This range is usually much smaller than the sensitivity range of the spectrometer detector. Therefore, a bandpass filter is usually required to restrict wavelengths outside the stopband of the FP DBRs. Such bandpass filters are difficult to design and implement. Alternatively, high index contrast materials must be can be used to broaden the stopband width of the FP DBRs. In this work, Indium phosphide all air-gap filters are proposed in conjunction with InGaAs based detectors. The designed filter has a wide stopband covering the entire InGaAs detector sensitivity range. The filter can be tuned in the 950-1450 nm with single mode operation. The designed filter can hence be used for noninvasive meat quality control.

  11. Carbon fluxes in tropical forest ecosystems: the value of Eddy-covariance data for individual-based dynamic forest gap models

    NASA Astrophysics Data System (ADS)

    Roedig, Edna; Cuntz, Matthias; Huth, Andreas

    2015-04-01

    The effects of climatic inter-annual fluctuations and human activities on the global carbon cycle are uncertain and currently a major issue in global vegetation models. Individual-based forest gap models, on the other hand, model vegetation structure and dynamics on a small spatial (<100 ha) and large temporal scale (>1000 years). They are well-established tools to reproduce successions of highly-diverse forest ecosystems and investigate disturbances as logging or fire events. However, the parameterizations of the relationships between short-term climate variability and forest model processes are often uncertain in these models (e.g. daily variable temperature and gross primary production (GPP)) and cannot be constrained from forest inventories. We addressed this uncertainty and linked high-resolution Eddy-covariance (EC) data with an individual-based forest gap model. The forest model FORMIND was applied to three diverse tropical forest sites in the Amazonian rainforest. Species diversity was categorized into three plant functional types. The parametrizations for the steady-state of biomass and forest structure were calibrated and validated with different forest inventories. The parameterizations of relationships between short-term climate variability and forest model processes were evaluated with EC-data on a daily time step. The validations of the steady-state showed that the forest model could reproduce biomass and forest structures from forest inventories. The daily estimations of carbon fluxes showed that the forest model reproduces GPP as observed by the EC-method. Daily fluctuations of GPP were clearly reflected as a response to daily climate variability. Ecosystem respiration remains a challenge on a daily time step due to a simplified soil respiration approach. In the long-term, however, the dynamic forest model is expected to estimate carbon budgets for highly-diverse tropical forests where EC-measurements are rare.

  12. ASGASEX, a comprehensive flux experiment

    SciTech Connect

    Oost, W.A.

    1994-12-31

    Among scientists working on CO{sub 2} exchange between air and sea there is a controversy between methods based on concentration measurements and transport coefficients on one hand and direct measurements of CO{sub 2} fluxes with the eddy correlation technique on the other. The controversy is caused by a gap of often more than an order of magnitude between the results of the two methods, in the transfer velocity k. The author decided to use the expertise gained during the HEXOS program to try to contribute to a solution of this problem by measuring all fluxes involved.

  13. "Advances in Coupled Air Quality, Farm Management and Biogeochemistry to address bidirectional ammonia flux"

    EPA Science Inventory

    A cropland farm management modeling system for regional air quality and field-scale applications of bi-directional ammonia exchange was presented at ITM XXI. The goal of this research is to improve estimates of nitrogen deposition to terrestrial and aquatic ecosystems and ambien...

  14. Historical changes in air temperature are evident in temperature fluxes measured in the sub-soil.

    NASA Astrophysics Data System (ADS)

    Fraser, Fiona; McCormick, Benjamin; Hallett, Paul; Wookey, Philip; Hopkins, David

    2013-04-01

    Warming trends in soil temperature have implications for a plethora of soil processes, including exacerbated climate change through the net release of greenhouse gases. Whereas long-term datasets of air temperature changes are abundant, a search of scientific literature reveals a lack of information on soil temperature changes and their specific consequences. We analysed five long-term data series collected in the UK (Dundee and Armagh) and Canada (Charlottetown, Ottawa and Swift Current). They show that the temperatures of soils at 5 - 20 cm depth, and sub-soils at 30 - 150 cm depth, increased in line with air temperature changes over the period 1958 - 2003. Differences were found, however, between soil and air temperatures when data were sub-divided into seasons. In spring, soil temperature warming ranged from 0.19°C at 30 cm in Armagh to 4.30°C at 50 cm in Charlottetown. In summer, however, the difference was smaller and ranged from 0.21°C at 10 cm in Ottawa to 3.70°C at 50 cm in Charlottetown. Winter temperatures were warmer in soil and ranged from 0.45°C at 5 cm in Charlottetown to 3.76°C at 150 cm in Charlottetown. There were significant trends in changes to soil temperature over time, whereas air temperature trends tended only to be significant in winter (changes range from 1.27°C in Armagh to 3.35°C in Swift Current). Differences in the seasonal warming patterns between air and soil temperatures have potential implications for the parameterization of models of biogeochemical cycling.

  15. Spectrally Resolved Flux Derived from Collocated AIRS and CERES Observations and its Application in Model Validation. Part I; Clear-Sky Over the Tropic Oceans

    NASA Technical Reports Server (NTRS)

    Huang, Xianglei; Yang, Wenze; Loeb, Norman G.; Ramaswamy, V.

    2008-01-01

    Spectrally resolved outgoing IR flux, the integrand of the outgoing longwave radiation (OLR), has its unique value in evaluating model simulations. Here we describe an algorithm of deriving such clear-sky outgoing spectral flux through the whole IR region from the collocated Atmospheric Infrared Sounder (AIRS) and the Clouds & the Earth's Radiant Energy System (CERES) measurements over the tropical oceans. Based on the scene types and corresponding angular distribution models (ADMs) used in the CERES Single Satellite Footprint (SSF) dataset, spectrally-dependent ADMs are developed and used to estimate the spectral flux at each AIRS channel. A multivariate linear prediction scheme is then used to estimate spectral fluxes at frequencies not covered by the AIRS instrument. The whole algorithm is validated using synthetic spectra as well as the CERES OLR measurements. Using the GFDL AM2 model simulation as a case study, the application of the derived clear-sky outgoing spectral flux in model evaluation is illustrated. By comparing the observed and simulated spectral flux in 2004, compensating errors in the simulated OLR from different absorption bands can be revealed, so does the errors from frequencies within a given absorption band. Discrepancies between the simulated and observed spatial distributions and seasonal evolutions of the spectral fluxes at different spectral ranges are further discussed. The methodology described in this study can be applied to other surface types as well as cloudy-sky observations and corresponding model evaluations.

  16. An automatic remotely web-based control equipment for investigating gas flux at water - air interfaces

    NASA Astrophysics Data System (ADS)

    Duc, N. T.; Silverstein, S.; Wik, M.; Crill, P. M.; Bastviken, D.; Varner, R. K.

    2014-12-01

    Aquatic ecosystems are major sources of greenhouse gases (GHG). Robust measurements of natural GHG emissions are vital for evaluating regional to global carbon budgets and for assessing climate feedbacks on natural emissions to improve climate models. Diffusive and ebullitive (bubble) transport are two major pathways of gas release from surface waters. Capturing the high temporal variability of these fluxes has been labor intensive using manual based methods, or expensive using available high resolution equipment (e.g. eddy correlation methods). Here, we present an inexpensive device that includes an easily mobile diffusive flux chamber and a bubble counter (inverted funnel) all in one. It is equipped with wireless data readout and web-based remote monitoring and control functions. The device can be programmed to measure in situ mixing ratios of gas in the chamber, and accumulation of ebullitive gas in the funnel. The device can also collect gas samples into sample bottles for subsequent analyses (e.g concentration, stable isotopes) in the laboratory.

  17. Modeling of the anthropogenic heat flux and its effect on air quality over the Yangtze River Delta region, China

    NASA Astrophysics Data System (ADS)

    Xie, M.; Liao, J.; Wang, T.; Zhu, K.; Zhuang, B.; Han, Y.; Li, M.; Li, S.

    2015-11-01

    Anthropogenic heat (AH) emissions from human activities caused by urbanization can affect the city environment. Based on the energy consumption and the gridded demographic data, the spatial distribution of AH emission over the Yangtze River Delta (YRD) region is estimated. Meanwhile, a new method for the AH parameterization is developed in the WRF/Chem model, which incorporates the gridded AH emission data with the seasonal and the diurnal variations into the simulations. By running this upgraded WRF/Chem for two typical months in 2010, the impacts of AH on the meteorology and air quality over the YRD region are studied. The results show that the AH fluxes over YRD have been growing in recent decades. In 2010, the annual mean values of AH over Shanghai, Jiangsu and Zhejiang are 14.46, 2.61 and 1.63 W m-2 respectively, with the high values of 113.5 W m-2 occurring in the urban areas of Shanghai. These AH emissions can significantly change the urban heat island and urban-breeze circulations in the cities of the YRD region. In Shanghai, 2 m air temperature increases by 1.6 °C in January and 1.4 °C in July, the planetary boundary layer height rises up by 140 m in January and 160 m in July, and 10 m wind speed is enhanced by 0.7 m s-1 in January and 0.5 m s-1 in July, with higher increment at night. And the enhanced vertical movement can transport more moisture to higher levels, which causes the decrease of water vapor at the ground level and the increase in the upper PBL, and thereby induces the accumulative precipitation to increase by 15-30 % over the megacities in July. The adding AH can impact the spatial and vertical distributions of the simulated pollutants as well. The concentrations of primary air pollutants decrease near surface and increase at the upper levels, due mainly to the increases of PBLH, surface wind speed and upward air vertical movement. But surface O3 concentrations increase in the urban areas, with maximum changes of 2.5 ppb in January and 4

  18. Air-sea fluxes and satellite-based estimation of water masses formation

    NASA Astrophysics Data System (ADS)

    Sabia, Roberto; Klockmann, Marlene; Fernandez-Prieto, Diego; Donlon, Craig

    2015-04-01

    Recent work linking satellite-based measurements of sea surface salinity (SSS) and sea surface temperature (SST) with traditional physical oceanography has demonstrated the capability of generating routinely satellite-derived surface T-S diagrams [1] and analyze the distribution/dynamics of SSS and its relative surface density with respect to in-situ measurements. Even more recently [2,3], this framework has been extended by exploiting these T-S diagrams as a diagnostic tool to derive water masses formation rates and areas. A water mass describes a water body with physical properties distinct from the surrounding water, formed at the ocean surface under specific conditions which determine its temperature and salinity. The SST and SSS (and thus also density) at the ocean surface are largely determined by fluxes of heat and freshwater. The surface density flux is a function of the latter two and describes the change of the density of seawater at the surface. To obtain observations of water mass formation is of great interest, since they serve as indirect observations of the thermo-haline circulation. The SSS data which has become available through the SMOS [4] and Aquarius [5] satellite missions will provide the possibility of studying also the effect of temporally-varying SSS fields on water mass formation. In the present study, the formation of water masses as a function of SST and SSS is derived from the surface density flux by integrating the latter over a specific area and time period in bins of SST and SSS and then taking the derivative of the total density flux with respect to density. This study presents a test case using SMOS SSS, OSTIA SST, as well as Argo ISAS SST and SSS for comparison, heat fluxes from the NOCS Surface Flux Data Set v2.0, OAFlux evaporation and CMORPH precipitation. The study area, initially referred to the North Atlantic, is extended over two additional ocean basins and the study period covers the 2011-2012 timeframe. Yearly, seasonal

  19. Entrainment Heat Flux Computed with Lidar and Wavelet Technique in Buenos Aires During Last Chaitén Volcano Eruption

    NASA Astrophysics Data System (ADS)

    Pawelko, Ezequiel Eduardo; Salvador, Jacobo Omar; Ristori, Pablo Roberto; Pallotta, Juan Vicente; Otero, Lidia Ana; Quel, Eduardo Jaime

    2016-06-01

    At Lidar Division of CEILAP (CITEDEF-CONICET) a multiwavelength Raman-Rayleigh lidar optimized to measure the atmospheric boundary layer is being operated. This instrument is used for monitoring important aerosol intrusion events in Buenos Aires, such as the arrival of volcanic ashes from the Chaitén volcano eruption on May 2008. That was the first monitoring of volcanic ash with lidar in Argentina. In this event several volcanic ash plumes with high aerosol optical thickness were detected in the free atmosphere, affecting the visibility, surface radiation and therefore, the ABL evolution. In this work, the impact of ashes in entrainment flux ratio is studied. This parameter is obtained from the atmospheric boundary layer height and entrainment zone thickness using algorithms based on covariance wavelet transform.

  20. Distributions and sea-to-air fluxes of nitrous oxide in the South China Sea and the West Philippines Sea

    NASA Astrophysics Data System (ADS)

    Tseng, Hsiao-Chun; Chen, Chen-Tung Arthur; Borges, Alberto V.; DelValls, T. Angel; Lai, Chao-Ming; Chen, Ting-Yu

    2016-09-01

    Approximately 600 water samples from the South China Sea (SCS) and 250 water samples from the West Philippines Sea (WPS) were collected during seven cruises from August 2003 to July 2007 to determine nitrous oxide (N2O) distributions between the surface and a maximum depth of 4250 m. In the SCS, the average surface N2O concentration exceeded the atmospheric equilibrium concentration (on average 132±23%); however in the WPS, the surface N2O concentration was lower than the atmospheric equilibrium concentration (on average 90±22%). The N2O concentration reached a maximum (~23 nmol L-1) in the WPS at 800-1000 m, and (~28 nmol L-1) at a shallower depth of around 600-800 m in the SCS, owing to vertical mixing and intensive upwelling in the SCS. In the SCS, the surface N2O concentration was 7.59±1.32 nmol L-1 and the calculated sea-to-air flux was 5.5±3.9 μmol m-2 d-1. The surface N2O concentration in the WPS, 5.19±1.26 nmol L-1, was lower than that in the SCS. The WPS is a sink for N2O and the calculated sea-to-air flux was -1.7±3.9 μmol m-2 d-1. The SCS emitted 19.3×106 mol d-1 N2O to the atmosphere and exported 8.5×106 mol d-1 N2O to the WPS during the wet season.

  1. Air

    MedlinePlus

    ... do to protect yourself from dirty air . Indoor air pollution and outdoor air pollution Air can be polluted indoors and it can ... this chart to see what things cause indoor air pollution and what things cause outdoor air pollution! Indoor ...

  2. Interaction between isoprene and ozone fluxes in a poplar plantation and its impact on air quality at the European level.

    PubMed

    Zenone, Terenzio; Hendriks, Carlijn; Brilli, Federico; Fransen, Erik; Gioli, Beniamio; Portillo-Estrada, Miguel; Schaap, Martijn; Ceulemans, Reinhart

    2016-09-12

    The emission of isoprene and other biogenic volatile organic compounds from vegetation plays an important role in tropospheric ozone (O3) formation. The potentially large expansion of isoprene emitting species (e.g., poplars) for bioenergy production might, therefore, impact tropospheric O3 formation. Using the eddy covariance technique we have simultaneously measured fluxes isoprene, O3 and of CO2 from a poplar (Populus) plantation grown for bioenergy production. We used the chemistry transport model LOTOS-EUROS to scale-up the isoprene emissions associated with the existing poplar plantations in Europe, and we assessed the impact of isoprene fluxes on ground level O3 concentrations. Our findings suggest that isoprene emissions from existing poplar-for-bioenergy plantations do not significantly affect the ground level of O3 concentration. Indeed the overall land in Europe covered with poplar plantations has not significantly changed over the last two decades despite policy incentives to produce bioenergy crops. The current surface area of isoprene emitting poplars-for-bioenergy remains too limited to significantly enhance O3 concentrations and thus to be considered a potential threat for air quality and human health.

  3. Interaction between isoprene and ozone fluxes in a poplar plantation and its impact on air quality at the European level.

    PubMed

    Zenone, Terenzio; Hendriks, Carlijn; Brilli, Federico; Fransen, Erik; Gioli, Beniamio; Portillo-Estrada, Miguel; Schaap, Martijn; Ceulemans, Reinhart

    2016-01-01

    The emission of isoprene and other biogenic volatile organic compounds from vegetation plays an important role in tropospheric ozone (O3) formation. The potentially large expansion of isoprene emitting species (e.g., poplars) for bioenergy production might, therefore, impact tropospheric O3 formation. Using the eddy covariance technique we have simultaneously measured fluxes isoprene, O3 and of CO2 from a poplar (Populus) plantation grown for bioenergy production. We used the chemistry transport model LOTOS-EUROS to scale-up the isoprene emissions associated with the existing poplar plantations in Europe, and we assessed the impact of isoprene fluxes on ground level O3 concentrations. Our findings suggest that isoprene emissions from existing poplar-for-bioenergy plantations do not significantly affect the ground level of O3 concentration. Indeed the overall land in Europe covered with poplar plantations has not significantly changed over the last two decades despite policy incentives to produce bioenergy crops. The current surface area of isoprene emitting poplars-for-bioenergy remains too limited to significantly enhance O3 concentrations and thus to be considered a potential threat for air quality and human health. PMID:27615148

  4. Interaction between isoprene and ozone fluxes in a poplar plantation and its impact on air quality at the European level

    PubMed Central

    Zenone, Terenzio; Hendriks, Carlijn; Brilli, Federico; Fransen, Erik; Gioli, Beniamio; Portillo-Estrada, Miguel; Schaap, Martijn; Ceulemans, Reinhart

    2016-01-01

    The emission of isoprene and other biogenic volatile organic compounds from vegetation plays an important role in tropospheric ozone (O3) formation. The potentially large expansion of isoprene emitting species (e.g., poplars) for bioenergy production might, therefore, impact tropospheric O3 formation. Using the eddy covariance technique we have simultaneously measured fluxes isoprene, O3 and of CO2 from a poplar (Populus) plantation grown for bioenergy production. We used the chemistry transport model LOTOS-EUROS to scale-up the isoprene emissions associated with the existing poplar plantations in Europe, and we assessed the impact of isoprene fluxes on ground level O3 concentrations. Our findings suggest that isoprene emissions from existing poplar-for-bioenergy plantations do not significantly affect the ground level of O3 concentration. Indeed the overall land in Europe covered with poplar plantations has not significantly changed over the last two decades despite policy incentives to produce bioenergy crops. The current surface area of isoprene emitting poplars-for-bioenergy remains too limited to significantly enhance O3 concentrations and thus to be considered a potential threat for air quality and human health. PMID:27615148

  5. Air-sea fluxes of CO2 and CH4 from the Penlee Point Atmospheric Observatory on the south-west coast of the UK

    NASA Astrophysics Data System (ADS)

    Yang, Mingxi; Bell, Thomas G.; Hopkins, Frances E.; Kitidis, Vassilis; Cazenave, Pierre W.; Nightingale, Philip D.; Yelland, Margaret J.; Pascal, Robin W.; Prytherch, John; Brooks, Ian M.; Smyth, Timothy J.

    2016-05-01

    We present air-sea fluxes of carbon dioxide (CO2), methane (CH4), momentum, and sensible heat measured by the eddy covariance method from the recently established Penlee Point Atmospheric Observatory (PPAO) on the south-west coast of the United Kingdom. Measurements from the south-westerly direction (open water sector) were made at three different sampling heights (approximately 15, 18, and 27 m above mean sea level, a.m.s.l.), each from a different period during 2014-2015. At sampling heights ≥ 18 m a.m.s.l., measured fluxes of momentum and sensible heat demonstrate reasonable ( ≤ ±20 % in the mean) agreement with transfer rates over the open ocean. This confirms the suitability of PPAO for air-sea exchange measurements in shelf regions. Covariance air-sea CO2 fluxes demonstrate high temporal variability. Air-to-sea transport of CO2 declined from spring to summer in both years, coinciding with the breakdown of the spring phytoplankton bloom. We report, to the best of our knowledge, the first successful eddy covariance measurements of CH4 emissions from a marine environment. Higher sea-to-air CH4 fluxes were observed during rising tides (20 ± 3; 38 ± 3; 29 ± 6 µmole m-2 d-1 at 15, 18, 27 m a.m.s.l.) than during falling tides (14 ± 2; 22 ± 2; 21 ± 5 µmole m-2 d-1), consistent with an elevated CH4 source from an estuarine outflow driven by local tidal circulation. These fluxes are a few times higher than the predicted CH4 emissions over the open ocean and are significantly lower than estimates from other aquatic CH4 hotspots (e.g. polar regions, freshwater). Finally, we found the detection limit of the air-sea CH4 flux by eddy covariance to be 20 µmole m-2 d-1 over hourly timescales (4 µmole m-2 d-1 over 24 h).

  6. Resolving the abundance and air-sea fluxes of airborne microorganisms in the North Atlantic Ocean.

    PubMed

    Mayol, Eva; Jiménez, María A; Herndl, Gerhard J; Duarte, Carlos M; Arrieta, Jesús M

    2014-01-01

    Airborne transport of microbes may play a central role in microbial dispersal, the maintenance of diversity in aquatic systems and in meteorological processes such as cloud formation. Yet, there is almost no information about the abundance and fate of microbes over the oceans, which cover >70% of the Earth's surface and are the likely source and final destination of a large fraction of airborne microbes. We measured the abundance of microbes in the lower atmosphere over a transect covering 17° of latitude in the North Atlantic Ocean and derived estimates of air-sea exchange of microorganisms from meteorological data. The estimated load of microorganisms in the atmospheric boundary layer ranged between 6 × 10(4) and 1.6 × 10(7) microbes per m(2) of ocean, indicating a very dynamic air-sea exchange with millions of microbes leaving and entering the ocean per m(2) every day. Our results show that about 10% of the microbes detected in the boundary layer were still airborne 4 days later and that they could travel up to 11,000 km before they entered the ocean again. The size of the microbial pool hovering over the North Atlantic indicates that it could play a central role in the maintenance of microbial diversity in the surface ocean and contribute significantly to atmospheric processes.

  7. Resolving the abundance and air-sea fluxes of airborne microorganisms in the North Atlantic Ocean

    PubMed Central

    Mayol, Eva; Jiménez, María A.; Herndl, Gerhard J.; Duarte, Carlos M.; Arrieta, Jesús M.

    2014-01-01

    Airborne transport of microbes may play a central role in microbial dispersal, the maintenance of diversity in aquatic systems and in meteorological processes such as cloud formation. Yet, there is almost no information about the abundance and fate of microbes over the oceans, which cover >70% of the Earth's surface and are the likely source and final destination of a large fraction of airborne microbes. We measured the abundance of microbes in the lower atmosphere over a transect covering 17° of latitude in the North Atlantic Ocean and derived estimates of air-sea exchange of microorganisms from meteorological data. The estimated load of microorganisms in the atmospheric boundary layer ranged between 6 × 104 and 1.6 × 107 microbes per m2 of ocean, indicating a very dynamic air-sea exchange with millions of microbes leaving and entering the ocean per m2 every day. Our results show that about 10% of the microbes detected in the boundary layer were still airborne 4 days later and that they could travel up to 11,000 km before they entered the ocean again. The size of the microbial pool hovering over the North Atlantic indicates that it could play a central role in the maintenance of microbial diversity in the surface ocean and contribute significantly to atmospheric processes. PMID:25400625

  8. Experimental method to reveal the effect of rotor magnet size and air gap on artificial heart driving motor torque and efficiency.

    PubMed

    Qian, K X; Yuan, H Y; Ru, W M; Zeng, P

    2002-01-01

    To investigate experimentally the effect of rotor magnet design on artificial heart driving motor performance, seven rotors with different magnet lengths or thicknesses, as well as different peripheral angles, were manufactured and tested in the same motor stator with different rotating speeds. The input power (voltage and current) and output torque were measured and the motor efficiency was computed. The results demonstrated that the reduction of rotor magnet size and the enlargement of the air gap between the rotor magnets and the stator coil core have no significant effect on motor efficiency, but will reduce the torque value on which the motor achieves the highest efficiency; it could be remedied however by increasing the rotating speed, because the torque at the high efficiency point will increase along with the rotating speed. These results may provide a basis for developing small rotor magnets, large air gap and high efficiency motors for driving an artificial heart pump.

  9. Evaluation of Trichloroethylene vapour fluxes using measurements at the soil-air interface and in the atmosphere close to the soil surface

    NASA Astrophysics Data System (ADS)

    Cotel, Solenn; Nagel, Vincent; Schäfer, Gerhard; Marzougui, Salsabil; Razakarisoa, Olivier; Millet, Maurice

    2013-04-01

    Industrialization during the 19th and 20th century led to the use of chemical products such as chlorinated solvents, e.g., trichloroethylene (TCE). At locations where volatile organic compounds were accidentally spilled on the soil during transport or leaked from their storage places, they could have migrated vertically through the unsaturated zone towards the underlying groundwater. As a result of their high volatility a large vapour plume is consequently formed. Understanding when, at which concentrations and how long, these pollutants will be present in soil, groundwater, atmosphere or indoor air, still remains a challenge up to date. This study was conducted as part of a broader experiment of TCE multiphase mass transfer in a large (25m×12m×3m) well-instrumented artificial basin. TCE was injected as liquid phase in the vadose zone and experiments were conducted during several months. Firstly, TCE vapour fluxes were experimentally determined in two different ways: (a) direct measurements at the soil-air interface using a flux chamber and (b) evaluations based on measurements of TCE concentrations in the air above the soil surface using a modular experimental flume (5m×1m×1m) with a fixed air flow. Secondly, numerical simulations were conducted to analyse the differences between these two types of fluxes. Several positions of the flume on the soil surface were tested. Based on the TCE concentrations measured in the air, vapour fluxes were determined with the aerodynamic method using the modified Thornthwaite-Holzmann equation. It assumes that the concentrations and velocities are temporally and spatially constant in horizontal planes and requires data on the gradients of concentration, horizontal wind velocity and temperature. TCE vapour fluxes measured at the soil-air interface decrease with distance from the source zone. However, this decrease was either high, at the first stage of experiment (120μg/(m2s) near the source zone compared to 1,1μg/(m2s) 2m

  10. Investigation on the Importance of Fast Air Temperature Measurements in the Sampling Cell of Short-Tube Closed-Path Gas Analyzer for Eddy-Covariance Fluxes

    NASA Astrophysics Data System (ADS)

    Kathilankal, J. C.; Fratini, G.; Burba, G. G.

    2014-12-01

    High-speed, precise gas analyzers used in eddy covariance flux research measure gas content in a known volume, thus essentially measuring gas density. The classical eddy flux equation, however, is based on the dry mole fraction. The relation between dry mole fraction and density is regulated by the ideal gas law and law of partial pressures, and depends on water vapor content, temperature and pressure of air. If the instrument can output precise fast dry mole fraction, the flux processing is significantly simplified and WPL terms accounting for air density fluctuations are no longer required. This will also lead to the reduction in uncertainties associated with the WPL terms. For instruments adopting an open-path design, this method is difficult to use because of complexities with maintaining reliable fast temperature measurements integrated over the entire measuring path, and also because of extraordinary challenges with accurate measurements of fast pressure in the open air flow. For instruments utilizing a traditional long-tube closed-path design, with tube length 1000 or more times the tube diameter, this method can be used when instantaneous fluctuations in the air temperature of the sampled air are effectively dampened, instantaneous pressure fluctuations are regulated or negligible, and water vapor is measured simultaneously with gas, or the sample is dried. For instruments with a short-tube enclosed design, most - but not all - of the temperature fluctuations are attenuated, so calculating unbiased fluxes using fast dry mole fraction output requires high-speed, precise temperature measurements of the air stream inside the cell. In this presentation, authors look at short-term and long-term data sets to assess the importance of high-speed, precise air temperature measurements in the sampling cell of short-tube enclosed gas analyzers. The CO2 and H2O half hourly flux calculations, as well as long-term carbon and water budgets, are examined.

  11. Regulation of CO2 Air Sea Fluxes by Sediments in the North Sea

    NASA Astrophysics Data System (ADS)

    Burt, William; Thomas, Helmuth; Hagens, Mathilde; Brenner, Heiko; Pätsch, Johannes; Clargo, Nicola; Salt, Lesley

    2016-04-01

    A multi-tracer approach is applied to assess the impact of boundary fluxes (e.g. benthic input from sediments or lateral inputs from the coastline) on the acid-base buffering capacity, and overall biogeochemistry, of the North Sea. Analyses of both basin-wide observations in the North Sea and transects through tidal basins at the North-Frisian coastline, reveal that surface distributions of the δ13C signature of dissolved inorganic carbon (DIC) are predominantly controlled by a balance between biological production and respiration. In particular, variability in metabolic DIC throughout stations in the well-mixed southern North Sea indicates the presence of an external carbon source, which is traced to the European continental coastline using naturally-occurring radium isotopes (224Ra and 228Ra). 228Ra is also shown to be a highly effective tracer of North Sea total alkalinity (AT) compared to the more conventional use of salinity. Coastal inputs of metabolic DIC and AT are calculated on a basin-wide scale, and ratios of these inputs suggest denitrification as a primary metabolic pathway for their formation. The AT input paralleling the metabolic DIC release prevents a significant decline in pH as compared to aerobic (i.e. unbuffered) release of metabolic DIC. Finally, long-term pH trends mimic those of riverine nitrate loading, highlighting the importance of coastal AT production via denitrification in regulating pH in the southern North Sea.

  12. CO2 air-sea fluxes across the Portuguese estuaries Tagus and Sado

    NASA Astrophysics Data System (ADS)

    Oliveira, A. P.; Cabeçadas, G.; Nogueira, M.

    2009-04-01

    Generally, estuaries and proximal shelves under the direct influence of river runoff and large inputs of organic matter are mostly heterotrophic and, therefore, act as a carbon source. In this context the CO2 dynamics in Tagus and Sado estuaries (SW Portugal) was studied under two different climate and hydrological situations. These moderately productive mesotidal coastal-plain lagoon-type estuaries, localised in the center of Portugal and distant 30-40 km apart, present quite different freshwater inflows, surface areas and water residence times. A study performed in 2001 revealed that the magnitude of CO2 fluxes in the two estuarine systems varied seasonally. CO2 emissions during the huge rainfall winter were similar in both estuaries, reaching a mean value of ~50 mmol m-2 d-1, while in spring emissions from Sado were ~6 times higher then Tagus ones, attaining a mean value of 62 mmol m-2 d-1. Nevertheless, in both sampling periods, Sado estuary showed, within the upper estuary (salinity

  13. Concentrations, size-distributions and air-to-sea fluxes of bio-active trace elements on the New Jersey coast

    NASA Astrophysics Data System (ADS)

    Gao, Y.; Xu, G.; Xu, T.; Mukherjee, P.

    2014-12-01

    The coastal marine atmosphere adjacent to large urban and industrial centers can be strongly impacted by pollution emissions, resulting in high loading of pollutants in the ambient air. Among airborne substances are certain bioactive trace elements including Cd, Cu, and Zn from a variety of emission sources. High concentrations of these elements in coastal air could not only result in enhanced air-to-sea deposition fluxes to coastal waters, but they could also be transported over the open ocean, affecting the composition of the remote marine atmosphere. In this presentation, we will discuss the concentrations, particle-size distributions of selected trace elements in aerosols and their properties in precipitation observed on the New Jersey coast. The estimates of the air-to-water deposition fluxes of these elements will also be discussed.

  14. Environmental controls of energy and trace gas exchanges at the water-air interface: Global synthesis of eddy fluxes over inland waters

    NASA Astrophysics Data System (ADS)

    Golub, M.; Desai, A. R.; Bohrer, G.; Blanken, P.; Deshmukh, C. S.; Franz, D.; Guérin, F.; Heiskanen, J. J.; Jammet, M.; Jonsson, A.; Karlsson, J.; Koebsch, F.; Liu, H.; Lohila, A.; Lundin, E.; Mammarella, I.; Rutgersson, A.; Sachs, T.; Serça, D.; Spence, C.; Strachan, I. B.; Vesala, T.; Weyhenmeyer, G. A.; Xiao, W.; Glatzel, S.

    2015-12-01

    Current estimates of energy and trace gases from inland waters often rely on limited point in time measurements, therefore, short time variation of fluxes and mechanism controlling the fluxes are particularly understudied. Here we present the results of a global synthesis of eddy fluxes from 29 globally distributed aquatic sites. The objective of this study was to quantify the magnitudes and variation of energy and CO2 fluxes and investigate their responses to environmental controls across half-hourly to monthly time scales. The coupled observations of in-lake physical and biogeochemical parameters with meteorology and eddy covariance fluxes were analyzed using decomposed correlation and wavelength coherence analysis to quantify the critical time scales that are associated with variation of energy and CO2 fluxes, and related drivers. The rates of fluxes were synthesized according to time scale, climate, and water body type. The diurnal cycles of both energy and CO2 fluxes variation were attributed to wind speed, solar radiation cycle, vapor pressure deficit, temperature gradients at water-air interface, and metabolism. Weekly time scales of variations were correlated with synoptic weather patterns. The monthly sums of energy fluxes showed a latitudinal gradient with the maxima observed in mid-latitude waterbodies. We found an inconsistent latitudinal pattern of monthly CO2 fluxes. Instead, we found correlation with proxies of lake productivity suggesting lake-specific characteristics play an important role in controlling flux magnitudes and variation. The results presented here highlight the importance of quantifying short-term variation of energy and trace gases fluxes towards improving the understanding of the water and carbon cycles and linked ecological processes.

  15. A correlation to predict the heat flux on the air-side of a vapor chamber with overturn-U flattened tubes

    NASA Astrophysics Data System (ADS)

    Srimuang, Wasan; Limkaisang, Viroj

    2016-08-01

    The heat transfer characteristics of a conventional vapor chamber (CVC) and a loop vapor chamber (LVC) are compared. The vapor chambers consisted of a stainless steel box with different covers. The results indicated that the heat flux and convective heat transfer coefficient of the air-side of LVC is higher than CVC. An empirical correlation was developed to predict the convective heat transfer coefficient of the air-side of the LVC.

  16. Eddy covariance flux of sulfur dioxide to the sea surface: Air-side resistance to deposition of a highly soluble gas

    NASA Astrophysics Data System (ADS)

    Porter, J.; De Bruyn, W. J.; Miller, S. D.; Saltzman, E. S.

    2014-12-01

    Deposition to the sea surface represents a major atmospheric removal mechanism for sulfur dioxide and many other highly soluble products of tropospheric photochemistry. Such gases include nitric acid, ammonia, organic acids, sulfur dioxide, and highly soluble organic compounds such as methanol and acetone. The deposition of highly soluble gases is controlled by turbulent and diffusive transport on the air side of the air/sea interface. In this study, air/sea fluxes of the soluble gas sulfur dioxide (SO2 ), sensible and latent heat, and momentum were measured using eddy covariance. This was a pilot study carried out in April 2014 on Scripps pier in La Jolla, California, that was designed to assess the potential for measuring SO2 fluxes over the ocean. SO2 was detected using chemical ion mass spectrometry in negative ion mode with a sensitivity of roughly 100 Hz/ppt. The ionization scheme involved addition of ozone to a dried air stream and subsequent conversion of SO2 to the SO5 - ion. The results demonstrate the feasibility of seagoing SO2 flux measurements. Such measurements can be used to constrain the depositional velocities of soluble gases and test models for air-side resistance to air/sea gas transfer.

  17. A regression approach for estimation of anthropogenic heat flux based on a bottom-up air pollutant emission database

    NASA Astrophysics Data System (ADS)

    Lee, Sang-Hyun; McKeen, Stuart A.; Sailor, David J.

    2014-10-01

    A statistical regression method is presented for estimating hourly anthropogenic heat flux (AHF) using an anthropogenic pollutant emission inventory for use in mesoscale meteorological and air-quality modeling. Based on bottom-up AHF estimated from detailed energy consumption data and anthropogenic pollutant emissions of carbon monoxide (CO) and nitrogen oxides (NOx) in the US National Emission Inventory year 2005 (NEI-2005), a robust regression relation between the AHF and the pollutant emissions is obtained for Houston. This relation is a combination of two power functions (Y = aXb) relating CO and NOx emissions to AHF, giving a determinant coefficient (R2) of 0.72. The AHF for Houston derived from the regression relation has high temporal (R = 0.91) and spatial (R = 0.83) correlations with the bottom-up AHF. Hourly AHF for the whole US in summer is estimated by applying the regression relation to the NEI-2005 summer pollutant emissions with a high spatial resolution of 4-km. The summer daily mean AHF range 10-40 W m-2 on a 4 × 4 km2 grid scale with maximum heat fluxes of 50-140 W m-2 for major US cities. The AHFs derived from the regression relations between the bottom-up AHF and either CO or NOx emissions show a small difference of less than 5% (4.7 W m-2) in city-scale daily mean AHF, and similar R2 statistics, compared to results from their combination. Thus, emissions of either species can be used to estimate AHF in the US cities. An hourly AHF inventory at 4 × 4 km2 resolution over the entire US based on the combined regression is derived and made publicly available for use in mesoscale numerical modeling.

  18. Distribution and Sea-to-air Flux of Nitrous Oxide in the East China Sea during the Summer of 2013

    NASA Astrophysics Data System (ADS)

    Wang, Lan; Zhang, Guiling; Zhu, Zhuoyi; Li, Jia; Liu, Sumei; Ye, Wangwang; Han, Yu

    2016-07-01

    Dissolved nitrous oxide (N2O) at different depths of 73 stations in the Changjiang (Yangtze River) Estuary and the East China Sea (ECS) were determined from August 4 to 31 of 2013, and the sea-to-air fluxes of N2O were also estimated in this study. N2O concentrations in the surface waters ranged from 6.33 to 44.40 nmol L-1 with an average of (9.27±4.30) nmol L-1 and the values in the bottom waters ranged from 5.19 to 26.98 nmol L-1 with an average of (11.87±3.71) nmol L-1. The concentrations of N2O decreased with distance from the Changjiang Estuary to the open sea. The vertical distributions of N2O indicated great spatial variations. A region of significant bottom-water hypoxia, with oxygen concentration less than 1.5 mg L-1, occurred at the north of the ECS, and increased bottom N2O concentrations was observed. Frequent vertical mixing may enhance the emission of N2O from this hypoxic area. N2O in the surface waters of all stations were over-saturated, and the N2O saturations ranged from 106% to 658%, with an average of (149±62)%. We estimated the sea-to-air fluxes of N2O as (30.6±59.1) μmol m-2 d-1 from the Changjiang Estuary, (9.8±8.8) μmol m-2 d-1 from the coastal and shelf, and (21.0±12.7) μmol m-2 d-1 from the continental slope using the Wanninkhof 1992 equation, (24.9±47.2) μmol m-2 d-1, (8.0±6.7) μmol m-2 d-1 and (16.5±9.6) μmol m-2 d-1 using the Nightingale 2000 equation, respectively. N2O emission from the ECS was estimated to be about (8.2-16.0)×10-2 Tg-N2O yr-1, suggesting that the ECS was a significant net source of atmospheric N2O.

  19. Climate and air quality impacts of altered BVOC fluxes from land cover change in Southeast Asia 1990 - 2010

    NASA Astrophysics Data System (ADS)

    Harper, Kandice; Yue, Xu; Unger, Nadine

    2016-04-01

    Large-scale transformation of the natural rainforests of Southeast Asia in recent decades, driven primarily by logging and agroforestry activities, including rapid expansion of plantations of high-isoprene-emitting oil palm (Elaeis guineensis) trees at the expense of comparatively low-emitting natural dipterocarp rainforests, may have altered the prevailing regime of biogenic volatile organic compound (BVOC) fluxes from this tropical region. Chemical processing of isoprene in the atmosphere impacts the magnitude and distribution of several short-lived climate forcers, including ozone and secondary organic aerosols. Consequently, modification of the fluxes of isoprene and other BVOCs from vegetation serves as a mechanism by which tropical land cover change impacts both air quality and climate. We apply satellite-derived snapshots of land cover for the period 1990 - 2010 to the NASA ModelE2-Yale Interactive Terrestrial Biosphere (ModelE2-YIBs) global carbon-chemistry-climate model to quantify the impact of Southeast Asian land cover change on atmospheric chemical composition and climate driven by changes in isoprene emission. NASA ModelE2-YIBs features a fully interactive land carbon cycle and includes a BVOC emission algorithm which energetically couples isoprene production to photosynthesis. The time-slice simulations are nudged with large-scale winds from the GMAO reanalysis dataset and are forced with monthly anthropogenic and biomass burning reactive air pollution emissions from the MACCity emissions inventory. Relative to the year 1990, regional isoprene emissions in 2010 increased by 2.6 TgC/yr from the expansion of Southeast Asian oil palm plantations and decreased by 0.7 TgC/yr from the loss of regional dipterocarp rainforest. Considering only the impact of land-cover-change-induced isoprene emission changes in Southeast Asia over this period, we calculate a spatially heterogeneous impact on regional seasonal surface-level ozone concentrations (minimum: -1

  20. Ecosystem Metabolism and Air-Water Fluxes of Greenhouse Gases in High Arctic Wetland Ponds

    NASA Astrophysics Data System (ADS)

    Lehnherr, I.; Venkiteswaran, J.; St. Louis, V. L.; Emmerton, C.; Schiff, S. L.

    2012-12-01

    Freshwater lakes and wetlands can be very productive systems on the Arctic landscape compared to terrestrial tundra ecosystems and provide valuable resources to many organisms, including waterfowl, fish and humans. Rates of ecosystem productivity dictate how much energy flows through food webs, impacting the abundance of higher-level organisms (e.g., fish), as well as the net carbon balance, which determines whether a particular ecosystem is a source or sink of carbon. Climate change is predicted to result in warmer temperatures, increased precipitation and permafrost melting in the Arctic and is already altering northern ecosystems at unprecedented rates; however, it is not known how freshwater systems are responding to these changes. To predict how freshwater systems will respond to complex environmental changes, it is necessary to understand the key processes, such as primary production and ecosystem respiration, that are driving these systems. We sampled wetland ponds (n=8) and lakes (n=2) on northern Ellesmere Island (81° N, Nunavut, Canada) during the open water season for a suite of biogeochemical parameters, including concentrations of dissolved gases (O2, CO2, CH4, N2O) as well as stable-isotope ratios of dissolved inorganic carbon (δ13C-DIC), dissolved oxygen (δ18O-DO), and water (δ18O-H2O). We will present rates of primary production and ecosystem respiration, modeled from the concentration and stable isotope ratios of DIC and DO, as well as air-water gas exchange of greenhouse gases in these high Arctic ponds and lakes. Preliminary results demonstrate that ecosystem metabolism in these ponds was high enough to result in significant deviations in the isotope ratios of DIC and DO from atmospheric equilibrium conditions. In other words ecosystem rates of primary production and respiration were faster than gas exchange even in these small, shallow, well-mixed ponds. Furthermore, primary production was elevated enough at all sites except Lake Hazen, a

  1. An Optimized Air-Core Coil Sensor with a Magnetic Flux Compensation Structure Suitable to the Helicopter TEM System

    PubMed Central

    Chen, Chen; Liu, Fei; Lin, Jun; Zhu, Kaiguang; Wang, Yanzhang

    2016-01-01

    The air-core coil sensor (ACS) is widely used as a transducer to measure the variation in magnetic fields of a helicopter transient electromagnetic (TEM) system. A high periodic emitting current induces the magnetic field signal of the underground medium. However, such current also generates a high primary field signal that can affect the received signal of the ACS and even damage the receiver. To increase the dynamic range of the received signal and to protect the receiver when emitting current rises/falls, the combination of ACS with magnetic flux compensation structure (bucking coil) is necessary. Moreover, the optimized ACS, which is composed of an air-core coil and a differential pre-amplifier circuit, must be investigated to meet the requirements of the helicopter TEM system suited to rapid surveying for shallow buried metal mine in rough topography. Accordingly, two ACSs are fabricated in this study, and their performance is verified and compared inside a magnetic shielding room. Using the designed ACSs, field experiments are conducted in Baoqing County. The field experimental data show that the primary field response can be compensated when the bucking coil is placed at an appropriate point in the range of allowed shift distance beyond the center of the transmitting coil and that the damage to the receiver induced by the over-statured signal can be solved. In conclusion, a more suitable ACS is adopted and is shown to have better performance, with a mass of 2.5 kg, resultant effective area of 11.6 m2 (i.e., diameter of 0.496 m), 3 dB bandwidth of 66 kHz, signal-to-noise ratio of 4 (i.e., varying magnetic field strength of 0.2 nT/s), and normalized equivalent input noise of 3.62 nV/m2. PMID:27077862

  2. Kinetics of the wetting of tin on air-passivated copper in the absence of a fluxing agent

    SciTech Connect

    Peebles, D.E.; Peebles, H.C.; Ohlhausen, J.A.; Yost, F.G.

    1994-10-01

    A specially designed ultrahigh vacuum in situ surface analysis and wetting system has been constructed to study the spreading of liquid metal solders on carefully prepared and well-characterized solid substrates. Initial studies have been completed for the spreading of pure tin solder on copper substrates in the absence of any fluxing agent. Surface chemical analysis by x-ray photoelectron spectroscopy showed the air-exposed surface to consisted of about 3 nm of Cu{sub 2}O, while the as-received surface consisted of about 8 nm of Cu{sub 2}O. The sputter-cleaned surface contained less than one monolayer (0.3 nm) of Cu{sub 2}O. Sample surfaces were prepared and spreading experiments performed without intermediate exposure of the surfaces to contaminating atmospheres. Solder spreading was performed under 50 torr of highly purified helium gas to allow for adequate thermal coupling between the solder and the substrate. Spreading experiments utilizing a linear temperature ramp show that pure tin solder spreads readily on oxidized copper surfaces at elevated temperatures. The initiation temperature for rapid tin spreading on the as-received copper surface was 325{degrees}C, similar to the temperature where isothermal spreading changes activation energy or rate. Decreasing the thickness of the oxide on the surface lowered the observed temperature for the initiation of spreading and increased the rate of spreading. On the sputter-cleaned copper surface, rapid solder spreading was observed immediately upon melting of the solder.

  3. Two-photon excitation of surface plasmon and the period-increasing effect of low spatial frequency ripples on a GaP crystal in air/water

    NASA Astrophysics Data System (ADS)

    Liu, Jukun; Jia, Tianqing; Zhao, Hongwei; Huang, Yaoqing

    2016-11-01

    We report the period-increasing effect of low spatial frequency ripples on a GaP crystal irradiated by 1 kHz, 50 fs, 800 nm femtosecond laser pulses. Massive free electrons are excited by a two-photon absorption process and surface plasmon is excited. The Drude model is used to estimate the changing of the dielectric constant of the GaP crystal. The period-increasing effects of low spatial frequency laser-induced ripples are theoretically predicted in air/water, and the experimental results agree well. The experimental and theoretical results indicate that surface plasmon excited by two-photon absorption plays a key role in the formation of low spatial frequency ripples.

  4. Introduction: Special Issue of Air Quality, Atmosphere and Health for Air Pollution and Health: Bridging the Gap from Source-to-Health Outcomes

    EPA Science Inventory

    The U.S. Environmental Protection Agency has established the National Ambient Air Quality Standards for six principal air pollutants (criteria pollutants): carbon monoxide (CO), lead (Pb), nitrogen dioxide, particulate matter in two size ranges [less than 2.5 μm (PM2.5) and less ...

  5. Air-sea flux of methane from selected marine hydrate/seep sites in the northern Gulf of Mexico during HYFLUX

    NASA Astrophysics Data System (ADS)

    Hu, L.; Yvon-Lewis, S. A.; Kessler, J. D.; MacDonald, I.

    2009-12-01

    Methane is one of the most important greenhouse gases, playing a significant role in global climate change and atmospheric chemistry. In spite of tremendous efforts made to constrain the strength of its sources and sinks, large uncertainties remain for some individual sources. Based on the previous observations and modeling studies, the flux of CH4 from marine hydrates and seeps to the atmosphere comprises a significant fraction of the entire methane flux from the global ocean. However, most of the estimates are based on the seafloor methane flux or discrete water column concentrations of methane and the averaged atmospheric methane ratios. In this study, we investigated three marine hydrate/seep sites in northern Gulf of Mexico in July of 2009 during the HYFLUX cruise. Continuous saturation-anomaly (deviation from equilibrium) measurements of methane, ethane and propane were made by alternately sampling the air or the headspace of Weiss-type equilibrator and analyzing it in a GC-FID system. Some 13CH4 measurements were also made continuously using a cavity ring-down spectrometer (CRDS). During this cruise, the maximum concentrations observed at the 3 marine hydrate/seep sites MC118, GC600, and GC185 were 14.5, 5.1, and 2.2 nmol/L, respectively. The air-sea fluxes, calculated from saturation anomalies, are used to create extremely high resolution flux maps for the three marine hydrate/seeps sites.

  6. Special Issue of Inhalation Toxicology for Air Pollution and Health: Bridging the Gap from Sources-to-Health Outcomes

    EPA Science Inventory

    Pollution and Health: Bridging the Gap from Sources to Health Outcomes”, an international specialty conference by the American Association for Aerosol Research (AAAR) (http://aaar.2010specialty.org/), provided one such opportunity for these interactions. The Conference was organi...

  7. Accounting for observational uncertainties in the evaluation of low latitude turbulent air-sea fluxes simulated in a suite of IPSL model versions

    NASA Astrophysics Data System (ADS)

    Servonnat, Jerome; Braconnot, Pascale; Gainusa-Bogdan, Alina

    2015-04-01

    Turbulent momentum and heat (sensible and latent) fluxes at the air-sea interface are key components of the whole energetic of the Earth's climate and their good representation in climate models is of prime importance. In this work, we use the methodology developed by Braconnot & Frankignoul (1993) to perform a Hotelling T2 test on spatio-temporal fields (annual cycles). This statistic provides a quantitative measure accounting for an estimate of the observational uncertainty for the evaluation of low-latitude turbulent air-sea fluxes in a suite of IPSL model versions. The spread within the observational ensemble of turbulent flux data products assembled by Gainusa-Bogdan et al (submitted) is used as an estimate of the observational uncertainty for the different turbulent fluxes. The methodology holds on a selection of a small number of dominating variability patterns (EOFs) that are common to both the model and the observations for the comparison. Consequently it focuses on the large-scale variability patterns and avoids the possibly noisy smaller scales. The results show that different versions of the IPSL couple model share common large scale model biases, but also that there the skill on sea surface temperature is not necessarily directly related to the skill in the representation of the different turbulent fluxes. Despite the large error bars on the observations the test clearly distinguish the different merits of the different model version. The analyses of the common EOF patterns and related time series provide guidance on the major differences with the observations. This work is a first attempt to use such statistic on the evaluation of the spatio-temporal variability of the turbulent fluxes, accounting for an observational uncertainty, and represents an efficient tool for systematic evaluation of simulated air-seafluxes, considering both the fluxes and the related atmospheric variables. References Braconnot, P., and C. Frankignoul (1993), Testing Model

  8. Real Time Flux Control in PM Motors

    SciTech Connect

    Otaduy, P.J.

    2005-09-27

    Significant research at the Oak Ridge National Laboratory (ORNL) Power Electronics and Electric Machinery Research Center (PEEMRC) is being conducted to develop ways to increase (1) torque, (2) speed range, and (3) efficiency of traction electric motors for hybrid electric vehicles (HEV) within existing current and voltage bounds. Current is limited by the inverter semiconductor devices' capability and voltage is limited by the stator wire insulation's ability to withstand the maximum back-electromotive force (emf), which occurs at the upper end of the speed range. One research track has been to explore ways to control the path and magnitude of magnetic flux while the motor is operating. The phrase, real time flux control (RTFC), refers to this mode of operation in which system parameters are changed while the motor is operating to improve its performance and speed range. RTFC has potential to meet an increased torque demand by introducing additional flux through the main air gap from an external source. It can augment the speed range by diverting flux away from the main air gap to reduce back-emf at high speeds. Conventional RTFC technology is known as vector control [1]. Vector control decomposes the stator current into two components; one that produces torque and a second that opposes (weakens) the magnetic field generated by the rotor, thereby requiring more overall stator current and reducing the efficiency. Efficiency can be improved by selecting a RTFC method that reduces the back-emf without increasing the average current. This favors methods that use pulse currents or very low currents to achieve field weakening. Foremost in ORNL's effort to develop flux control is the work of J. S. Hsu. Early research [2,3] introduced direct control of air-gap flux in permanent magnet (PM) machines and demonstrated it with a flux-controlled generator. The configuration eliminates the problem of demagnetization because it diverts all the flux from the magnets instead of

  9. Intraday evaporation and heat fluxes variation at air-water interface of extremely shallow lakes in Chilean Andean Plateau

    NASA Astrophysics Data System (ADS)

    Vergara, Jaime; de la Fuente, Alberto

    2016-04-01

    Salars are landscapes formed by evapo-concentration of salts that usually have extremely shallow terminal lagoons (de la Fuente & Niño, 2010). They are located in the altiplanic region of the Andes Mountains of Chile, Argentina, Bolivia and Peru, and they sustain highly vulnerable and isolated ecosystems in the Andean Desert. These ecosystems are sustained by benthic primary production, which is directly linked to mass, heat and momentum transfer between the water column and the atmosphere (de la Fuente, 2014). Despite the importance of these transport processes across the air-water interface, there are few studies describing their intraday variation and how they are influenced by the stability of the atmospheric boundary layer in the altiplano. The main objective of this work is to analyze the intraday vertical transport variation of water vapor, temperature and momentum between the atmosphere and a shallow water body on Salar del Huasco located in northern Chile (20°19'40"S, 68°51'25"W). To achieve this goal, we measured atmospheric and water variables in a campaign realized on late October 2015, using high frequency meteorological instruments (a sonic anemometer with an incorporated infrared gas analyzer, and a standard meteorological station) and water sensors. From these data, we characterize the intraday variation of water vapor, temperature and momentum fluxes, we quantify the influence of the atmospheric boundary layer stability on them, and we estimate transfer coefficients associated to latent heat, sensible heat, hydrodynamic drag and vertical transport of water vapor. As first results, we found that latent and sensible heat fluxes are highly influenced by wind speed rather buoyancy, and we can identify four intraday intervals with different thermo-hydrodynamic features: (1) cooling under stable condition with wind speed near 0 from midnight until sunrise; (2) free convection with nearly no wind speed under unstable condition from sunrise until midday

  10. Sea surface carbon dioxide at the Georgia time series site (2006-2007): Air-sea flux and controlling processes

    NASA Astrophysics Data System (ADS)

    Xue, Liang; Cai, Wei-Jun; Hu, Xinping; Sabine, Christopher; Jones, Stacy; Sutton, Adrienne J.; Jiang, Li-Qing; Reimer, Janet J.

    2016-01-01

    Carbon dioxide partial pressure (pCO2) in surface seawater was continuously recorded every three hours from 18 July 2006 through 31 October 2007 using a moored autonomous pCO2 (MAPCO2) system deployed on the Gray's Reef buoy off the coast of Georgia, USA. Surface water pCO2 (average 373 ± 52 μatm) showed a clear seasonal pattern, undersaturated with respect to the atmosphere in cold months and generally oversaturated in warm months. High temporal resolution observations revealed important events not captured in previous ship-based observations, such as sporadically occurring biological CO2 uptake during April-June 2007. In addition to a qualitative analysis of the primary drivers of pCO2 variability based on property regressions, we quantified contributions of temperature, air-sea exchange, mixing, and biological processes to monthly pCO2 variations using a 1-D mass budget model. Although temperature played a dominant role in the annual cycle of pCO2, river inputs especially in the wet season, biological respiration in peak summer, and biological production during April-June 2007 also substantially influenced seawater pCO2. Furthermore, sea surface pCO2 was higher in September-October 2007 than in September-October 2006, associated with increased river inputs in fall 2007. On an annual basis this site was a moderate atmospheric CO2 sink, and was autotrophic as revealed by monthly mean net community production (NCP) in the mixed layer. If the sporadic short productive events during April-May 2007 were missed by the sampling schedule, one would conclude erroneously that the site is heterotrophic. While previous ship-based pCO2 data collected around this buoy site agreed with the buoy CO2 data on seasonal scales, high resolution buoy observations revealed that the cruise-based surveys undersampled temporal variability in coastal waters, which could greatly bias the estimates of air-sea CO2 fluxes or annual NCP, and even produce contradictory results.

  11. Characterization of Sea-Air Methane Fluxes Around a Seafloor Gas Seep in the Central Laptev Sea

    NASA Astrophysics Data System (ADS)

    Geibel, M. C.; Thornton, B. F.; Prytherch, J.; Brooks, I. M.; Salisbury, D. J.; Tjernstrom, M. K. H.; Semiletov, I. P.; Mörth, C. M.; Humborg, C.; Crill, P. M.

    2015-12-01

    The fate of CH4 released from thawing subsea permafrost on the East Siberian Arctic Shelf (ESAS) is unclear. In recent years, interest has focused on the possibility of large emissions of CH4 directly to the atmosphere from this remote area. It is uncertain how high those emissions are and whether they are primarily of biogenic or thermogenic nature, or some combination of sources. The SWERUS-C3 expedition onboard the Swedish icebreaker Oden during July-August 2014 sought to document possible CH4 release from subsea permafrost, and to understand mechanisms and magnitudes of such CH4 being released to the atmosphere. During the first leg of the expedition continuous high-resolution measurements were made to determine the in situ concentrations of CH4 in both the atmosphere and surface water. During SWERUS-C3, several underwater gas flares were found within the ESAS region showing elevated CH4 concentrations collocated in the surface waters. Here we focus on one seep area, a so-called "mega-flare" site, in the central Laptev Sea. Over individual gas flares of this site the surface water concentration of CH4 reached as high as 200ppm. The atmospheric concentrations of CH4 briefly (< 1 s) reached a maximum of ~3.2 ppm. More typical atmospheric values around the seeps were between 1.9-2.0 ppm (background values were approximately 1.88 ppm). However, such peak concentrations in both air and water were highly localized, returning to background levels within a few hundred meters of the source seeps. Together with continuous high-precision eddy-covariance measurements that were made during the SWERUS-C3 expedition, the combined dataset allows an intensive analysis these highly inhomogeneous gas flares. This gives the opportunity to calculate accurate high-resolution CH4 fluxes and thus give a better insight into the current rates of subsea CH4 outgassing reaching the atmosphere.

  12. Extinction measurements for optical band gap determination of soot in a series of nitrogen-diluted ethylene/air non-premixed flames.

    PubMed

    Adkins, Erin M; Miller, J Houston

    2015-01-28

    Visible light extinction was measured in a series of nitrogen-diluted, ethylene/air, non-premixed flames and this data was used to determine the optical band gap, OBG, as a function of flame position. Collimated light from a supercontinuum source is telescopically expanded and refocused to match the f- number of a dispersing monochromator. The dispersed light is split into a power metering channel and a channel that is periscoped and focused into the flame. The transmitted light is then recollimated and focussed onto a silicon photodiode detector. After tomographic reconstruction of the radial extinction field, the OBG was derived from the near-edge absorption feature using Tauc/Davis-Mott analysis. A slight evolution in OBG was observed throughout all flame systems with a consistent range of OBG observed between approximately 1.85 eV and 2.35 eV. Averaging over all positions the mean OBG was approximately 2.09 eV for all flame systems. Comparing these results to previously published computational results relating calculated HOMO-LUMO gaps for a variety of D2h PAH molecules to the number of aromatic rings in the structure, showed that the observed optical band gap is consistent with a PAH of about 14 rings or a conjugation length of 0.97 nm. This work provides experimental support to the model of soot formation where the transition from chemical to physical growth starts at a modest molecular size; about the size of circumpyrene.

  13. Characteristics of a laser triggered spark gap using air, Ar, CH4, H2, He, N2, SF6, and Xe

    NASA Astrophysics Data System (ADS)

    Kimura, W. D.; Kushner, M. J.; Seamans, J. F.

    1988-03-01

    A KrF discharge laser (248 nm) has been used to laser trigger, by volume preionization, a spark gap switch (38-65 kV, >10 kA, 100 ns pulse duration) filled with 20 different gas mixtures using various combinations of air, Ar, CH4, H2, He, N2 SF6, and Xe. A pulsed laser interferometer is used to probe the spark column. Characteristics studied include the internal structure of the column, the arc expansion rate, and evidence of any photoionization precursor effect. Our results show that the rate of arc expansion varies depending on the average molecular weight of the mixtures. In this experiment, pure H2 has the highest rate (≊9.5×105 cm/s) and air has one of the lowest (≊7×105 cm/s) for the same hold-off voltage. A computer model of the spark column formation is able to predict most of the structure observed in the arcs, including the effect of mixing gases with widely different molecular weights. The work suggests that, under proper circumstances, the spark gap switch performance may be improved by using gases lighter than conventional switch gases such as SF6.

  14. X-ray and runaway electron generation in repetitive pulsed discharges in atmospheric pressure air with a point-to-plane gap

    NASA Astrophysics Data System (ADS)

    Shao, Tao; Tarasenko, Victor F.; Zhang, Cheng; Shut'ko, Yuliya V.; Yan, Ping

    2011-05-01

    In this paper, using two repetitive nanosecond generators, x-rays were detected in atmospheric air with a highly inhomogeneous electric field by a point-to- plane gap. The rise times of the generators were about 15 and 1 ns. The x-rays were directly measured by various dosimeters and a NaI scintillator with a photomultiplier tube. X-rays were detected in the continuous mode at pulse repetition frequency up to 1 kHz and a voltage pulse rise time of ˜15 ns. It is shown that the maximum x-ray intensity is attainable at different pulse repetition frequencies depending on the voltage pulse parameters and cathode design. In atmospheric pressure air the x-ray intensity is found to increase with increasing the pulse repetition frequency up to 1 kHz. It is confirmed that the maximum x-ray intensity is attained in a diffuse discharge in a point-to-plane gap.

  15. X-ray and runaway electron generation in repetitive pulsed discharges in atmospheric pressure air with a point-to-plane gap

    SciTech Connect

    Shao Tao; Yan Ping; Tarasenko, Victor F.; Shut'ko, Yuliya V.; Zhang Cheng

    2011-05-15

    In this paper, using two repetitive nanosecond generators, x-rays were detected in atmospheric air with a highly inhomogeneous electric field by a point-to- plane gap. The rise times of the generators were about 15 and 1 ns. The x-rays were directly measured by various dosimeters and a NaI scintillator with a photomultiplier tube. X-rays were detected in the continuous mode at pulse repetition frequency up to 1 kHz and a voltage pulse rise time of {approx}15 ns. It is shown that the maximum x-ray intensity is attainable at different pulse repetition frequencies depending on the voltage pulse parameters and cathode design. In atmospheric pressure air the x-ray intensity is found to increase with increasing the pulse repetition frequency up to 1 kHz. It is confirmed that the maximum x-ray intensity is attained in a diffuse discharge in a point-to-plane gap.

  16. Reconstruction of super-resolution fields of ocean pCO2 and air-sea fluxes of CO2 from satellite imagery in the Southeastern Atlantic

    NASA Astrophysics Data System (ADS)

    Hernández-Carrasco, I.; Sudre, J.; Garçon, V.; Yahia, H.; Garbe, C.; Paulmier, A.; Dewitte, B.; Illig, S.; Dadou, I.

    2015-01-01

    The knowledge of Green House Gases GHGs fluxes at the air-sea interface at high resolution is crucial to accurately quantify the role of the ocean in the absorption and emission of GHGs. In this paper we present a novel method to reconstruct maps of surface ocean partial pressure of CO2, pCO2, and air-sea CO2 fluxes at super resolution (4 km) using Sea Surface Temperature (SST) and Ocean Colour (OC) data at this resolution, and CarbonTracker CO2 fluxes data at low resolution (110 km). Inference of super-resolution of pCO2, and air-sea CO2 fluxes is performed using novel nonlinear signal processing methodologies that prove efficient in the context of oceanography. The theoretical background comes from the Microcanonical Multifractal Formalism which unlocks the geometrical determination of cascading properties of physical intensive variables. As a consequence, a multiresolution analysis performed on the signal of the so-called singularity exponents allows the correct and near optimal cross-scale inference of GHGs fluxes, as the inference suits the geometric realization of the cascade. We apply such a methodology to the study offshore of the Benguela area. The inferred representation of oceanic partial pressure of CO2 improves and enhances the description provided by CarbonTracker, capturing the small scale variability. We examine different combinations of Ocean Colour and Sea Surface Temperature products in order to increase the number of valid points and the quality of the inferred pCO2 field. The methodology is validated using in-situ measurements by means of statistical errors. We obtain that mean absolute and relative errors in the inferred values of pCO2 with respect to in-situ measurements are smaller than for CarbonTracker.

  17. Natural Air-Sea Flux of CO2 in Simulations of the NASA-GISS Climate Model: Sensitivity to the Physical Ocean Model Formulation

    NASA Technical Reports Server (NTRS)

    Romanou, A.; Gregg, Watson W.; Romanski, J.; Kelley, M.; Bleck, R.; Healy, R.; Nazarenko, L.; Russell, G.; Schmidt, G. A.; Sun, S.; Tausnev, N.

    2013-01-01

    Results from twin control simulations of the preindustrial CO2 gas exchange (natural flux of CO2) between the ocean and the atmosphere are presented here using the NASA-GISS climate model, in which the same atmospheric component (modelE2) is coupled to two different ocean models, the Russell ocean model and HYCOM. Both incarnations of the GISS climate model are also coupled to the same ocean biogeochemistry module (NOBM) which estimates prognostic distributions for biotic and abiotic fields that influence the air-sea flux of CO2. Model intercomparison is carried out at equilibrium conditions and model differences are contrasted with biases from present day climatologies. Although the models agree on the spatial patterns of the air-sea flux of CO2, they disagree on the strength of the North Atlantic and Southern Ocean sinks mainly because of kinematic (winds) and chemistry (pCO2) differences rather than thermodynamic (SST) ones. Biology/chemistry dissimilarities in the models stem from the different parameterizations of advective and diffusive processes, such as overturning, mixing and horizontal tracer advection and to a lesser degree from parameterizations of biogeochemical processes such as gravitational settling and sinking. The global meridional overturning circulation illustrates much of the different behavior of the biological pump in the two models, together with differences in mixed layer depth which are responsible for different SST, DIC and nutrient distributions in the two models and consequently different atmospheric feedbacks (in the wind, net heat and freshwater fluxes into the ocean).

  18. The influence of dynamic chamber design and operating parameters on calculated surface-to-air mercury fluxes

    NASA Astrophysics Data System (ADS)

    Eckley, C. S.; Gustin, M.; Lin, C.-J.; Li, X.; Miller, M. B.

    2010-01-01

    Dynamic Flux Chambers (DFCs) are commonly applied for the measurement of non-point source mercury (Hg) emissions from a wide range of surfaces. A standard operating protocol and design for DFCs does not exist, and as a result there is a large diversity in methods described in the literature. Because natural and anthropogenic non-point sources are thought to contribute significantly to the atmosphere Hg pool, development of accurate fluxes during field campaigns is essential. The objective of this research was to determine how differences in chamber material, sample port placement, vertical cross sectional area/volume, and flushing flow rate influence the Hg flux from geologic materials. Hg fluxes measured with a Teflon chamber were higher than those obtained using a polycarbonate chamber, with differences related to light transmission and substrate type. Differences in sample port placement (side versus top) did not have an influence on Hg fluxes. When the same flushing flow rate was applied to two chambers of different volumes, higher fluxes were calculated for the chamber with the smaller volume. Conversely, when two chambers with different volumes were maintained at similar turnover times, the larger volume chamber yielded higher Hg fluxes. Overall, the flushing flow rate and associated chamber turnover time had the largest influence on Hg flux relative to the other parameters tested. Results from computational fluid dynamic (CFD) modeling inside a DFC confirm that the smaller diffusion resistance at higher flushing flows contributes to the higher measured flux. These results clearly illustrate that differences in chamber design and operation can significantly influence the resulting calculated Hg flux, and thus impact the comparability of results obtained using DFC designs and/or operating parameters. A protocol for determining a flushing flow rate that results in fluxes less affected by chamber operating conditions and design is proposed. Application of this

  19. Measurement of gas species, temperatures, coal burnout, and wall heat fluxes in a 200 MWe lignite-fired boiler with different overfire air damper openings

    SciTech Connect

    Jianping Jing; Zhengqi Li; Guangkui Liu; Zhichao Chen; Chunlong Liu

    2009-07-15

    Measurements were performed on a 200 MWe, wall-fired, lignite utility boiler. For different overfire air (OFA) damper openings, the gas temperature, gas species concentration, coal burnout, release rates of components (C, H, and N), furnace temperature, and heat flux and boiler efficiency were measured. Cold air experiments for a single burner were conducted in the laboratory. The double-swirl flow pulverized-coal burner has two ring recirculation zones starting in the secondary air region in the burner. As the secondary air flow increases, the axial velocity of air flow increases, the maxima of radial velocity, tangential velocity and turbulence intensity all increase, and the swirl intensity of air flow and the size of recirculation zones increase slightly. In the central region of the burner, as the OFA damper opening widens, the gas temperature and CO concentration increase, while the O{sub 2} concentration, NOx concentration, coal burnout, and release rates of components (C, H, and N) decrease, and coal particles ignite earlier. In the secondary air region of the burner, the O{sub 2} concentration, NOx concentration, coal burnout, and release rates of components (C, H, and N) decrease, and the gas temperature and CO concentration vary slightly. In the sidewall region, the gas temperature, O{sub 2} concentration, and NOx concentration decrease, while the CO concentration increases and the gas temperature varies slightly. The furnace temperature and heat flux in the main burning region decrease appreciably, but increase slightly in the burnout region. The NOx emission decreases from 1203.6 mg/m{sup 3} (6% O{sub 2}) for a damper opening of 0% to 511.7 mg/m{sup 3} (6% O{sub 2}) for a damper opening of 80% and the boiler efficiency decreases from 92.59 to 91.9%. 15 refs., 17 figs., 3 tabs.

  20. Spatial and seasonal variability of CO2 flux at the air-water interface of the Three Gorges Reservoir.

    PubMed

    Le, Yang; Lu, Fei; Wang, Xiaoke; Duan, Xiaonan; Tong, Lei; Ouyang, Zhiyun; Li, Hepeng

    2013-11-01

    Diffusive carbon dioxide (CO2) emissions from the water surface of the Three Gorges Reservoir, currently the largest hydroelectric reservoir in the world, were measured using floating static chambers over the course of a yearlong survey. The results showed that the average annual CO2 flux was (163.3 +/- 117.4) mg CO2/(m2.hr) at the reservoir surface, which was larger than the CO2 flux in most boreal and temperate reservoirs but lower than that in tropical reservoirs. Significant spatial variations in CO2 flux were observed at four measured sites, with the largest flux measured at Wushan (221.9 mg CO2/(m2.hr)) and the smallest flux measured at Zigui (88.6 mg CO2/(m(2).hr)); these differences were probably related to the average water velocities at different sites. Seasonal variations in CO2 flux were also observed at four sites, starting to increase in January, continuously rising until peaking in the summer (June-August) and gradually decreasing thereafter. Seasonal variations in CO2 flux could reflect seasonal dynamics in pH, water velocity, and temperature. Since the spatial and temporal variations in CO2 flux were significant and dependent on multiple physical, chemical, and hydrological factors, it is suggested that long-term measurements should be made on a large spatial scale to assess the climatic influence of hydropower in China, as well as the rest of the world.

  1. Automatic Web-Based, Radio-Network System To Monitor And Control Equipment For Investigating Gas Flux At Water - Air Interfaces

    NASA Astrophysics Data System (ADS)

    Duc, N. T.; Silverstein, S.; Wik, M.; Beckman, P.; Crill, P. M.; Bastviken, D.; Varner, R. K.

    2015-12-01

    Aquatic ecosystems are major sources of greenhouse gases (GHG). Robust measurements of natural GHG emissions are vital for evaluating regional to global carbon budgets and for assessing climate feedbacks on natural emissions to improve climate models. Diffusive and ebullitive (bubble) transport are two major pathways of gas release from surface waters. To capture the high temporal variability of these fluxes in a well-defined footprint, we designed and built an inexpensive automatic device that includes an easily mobile diffusive flux chamber and a bubble counter, all in one. Besides a function of automatically collecting gas samples for subsequent various analyses in the laboratory, this device utilizes low cost CO2 sensor (SenseAir, Sweden) and CH4 sensor (Figaro, Japan) to measure GHG fluxes. To measure the spatial variability of emissions, each of the devices is equipped with an XBee module to enable a local radio communication DigiMesh network for time synchronization and data readout at a server-controller station on the lakeshore. Software of this server-controller is operated on a low cost Raspberry Pi computer which has a 3G connection for remote monitoring - controlling functions from anywhere in the world. From field studies in Abisko, Sweden in summer 2014 and 2015, the system has resulted in measurements of GHG fluxes comparable to manual methods. In addition, the deployments have shown the advantage of a low cost automatic network system to study GHG fluxes on lakes in remote locations.

  2. Experimental investigations on decay heat removal in advanced nuclear reactors using single heater rod test facility: Air alone in the annular gap

    SciTech Connect

    Bopche, Santosh B.; Sridharan, Arunkumar

    2010-11-15

    During a loss of coolant accident in nuclear reactors, radiation heat transfer accounts for a significant amount of the total heat transfer in the fuel bundle. In case of heavy water moderator nuclear reactors, the decay heat of a fuel bundle enclosed in the pressure tube and outer concentric calandria tube can be transferred to the moderator. Radiation heat transfer plays a significant role in removal of decay heat from the fuel rods to the moderator, which is available outside the calandria tube. A single heater rod test facility is designed and fabricated as a part of preliminary investigations. The objective is to anticipate the capability of moderator to remove decay heat, from the reactor core, generated after shut down. The present paper focuses mainly on the role of moderator in removal of decay heat, for situation with air alone in the annular gap of pressure tube and calandria tube. It is seen that the naturally aspirated air is capable of removing the heat generated in the system compared to the standstill air or stagnant water situations. It is also seen that the flowing moderator is capable of removing a greater fraction of heat generated by the heater rod compared to a stagnant pool of boiling moderator. (author)

  3. 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).

  4. High resolution measurements of methane and carbon dioxide in surface waters over a natural seep reveal dynamics of dissolved phase air-sea flux.

    PubMed

    Du, Mengran; Yvon-Lewis, Shari; Garcia-Tigreros, Fenix; Valentine, David L; Mendes, Stephanie D; Kessler, John D

    2014-09-01

    Marine hydrocarbon seeps are sources of methane and carbon dioxide to the ocean, and potentially to the atmosphere, though the magnitude of the fluxes and dynamics of these systems are poorly defined. To better constrain these variables in natural environments, we conducted the first high-resolution measurements of sea surface methane and carbon dioxide concentrations in the massive natural seep field near Coal Oil Point (COP), California. The corresponding high resolution fluxes were calculated, and the total dissolved phase air-sea fluxes over the surveyed plume area (∼363 km(2)) were 6.66 × 10(4) to 6.71 × 10(4) mol day(-1) with respect to CH4 and -6.01 × 10(5) to -5.99 × 10(5) mol day(-1) with respect to CO2. The mean and standard deviation of the dissolved phase air-sea fluxes of methane and carbon dioxide from the contour gridding analysis were estimated to be 0.18 ± 0.19 and -1.65 ± 1.23 mmol m(-2) day(-1), respectively. This methane flux is consistent with previous, lower-resolution estimates and was used, in part, to conservatively estimate the total area of the dissolved methane plume at 8400 km(2). The influx of carbon dioxide to the surface water refutes the hypothesis that COP seep methane appreciably influences carbon dioxide dynamics. Seeing that the COP seep field is one of the biggest natural seeps, a logical conclusion could be drawn that microbial oxidation of methane from natural seeps is of insufficient magnitude to change the resulting plume area from a sink of atmospheric carbon dioxide to a source.

  5. On the importance of high-frequency air-temperature fluctuations for spectroscopic corrections of open-path carbon dioxide flux measurements

    NASA Astrophysics Data System (ADS)

    Bogoev, Ivan; Helbig, Manuel; Sonnentag, Oliver

    2015-04-01

    A growing number of studies report systematic differences in CO2 flux estimates obtained with the two main types of gas analyzers: compared to eddy-covariance systems based on closed-path (CP) gas analyzers, systems with open-path (OP) gas analyzers systematically overestimate CO2 uptake during daytime periods with high positive sensible heat fluxes, while patterns for differences in nighttime CO2 exchange are less obvious. These biases have been shown to correlate with the sign and the magnitude of the sensible heat flux and to introduce large uncertainties when calculating annual CO2 budgets. In general, CP and OP gas analyzers commonly used to measure the CO2 density in the atmosphere operate on the principle of infrared light absorption approximated by Beer-Lambert's law. Non-dispersive interference-based optical filter elements are used to select spectral bands with strong attenuation of light transmission, characteristic to the gas of interest. The intensity of the light passing through the optical sensing path depends primarily on the amount of absorber gas in the measurement volume. Besides the density of the gas, barometric pressure and air temperature are additional factors affecting the strength and the half-width of the absorption lines. These so-called spectroscopic effects are accounted for by measuring barometric pressure and air temperature in the sensing path and scaling the light-intensity measurements before applying the calibration equation. This approach works well for CP gas analyzers with an intake tube that acts as a low-pass filter on fast air-temperature fluctuations. Low-frequency response temperature sensors in the measurement cell are therefore sufficient to account for spectroscopic temperature effects. In contrast, OP gas analyzers are exposed to high-frequency air-temperature fluctuations associated with the atmospheric surface-layer turbulent heat exchange. If not corrected adequately, these fast air-temperature variations can cause

  6. A study of the evolution of the surface heat flux off the southeast coast of the United States during a cold air outbreak using satellite remote sensing data

    NASA Technical Reports Server (NTRS)

    Vukovich, Fred M.; Dunn, J. W.; Crissman, Bobby W.

    1990-01-01

    Attention is given to the contribution of the marine boundary layer to storm development via a study of the evolution of the spatial distribution of the heat flux during a cold-air outburst (CAO) which occurred during the GALE Field Program period in a 550,000-sq-km area off the southeast coast of the United States. The study focuses on a CAO that occurred in the period February 24-26, 1986. During the CAO, the area averaged total surface heat flux ranged from 190 W/sq m to 1114 W/sq m. The high value was characterized by a lower average surface air and dew-point temperatures and a higher average surface wind speed. In general, the surface heat flux increased as the sea-surface temperatures on the continental shelf increased. It reached the maximum over the Gulf Stream, and then decreased over the eastern portions of the Gulf Stream and over the Sargasso Sea. The configuration conforms with some of the earlier findings of Bane and Osgoode (1989) and Blanton et al. (1989).

  7. A quantitative determination of air-water heat fluxes in Hermit Lake, New Hampshire under varying meteorological conditions, time of day, and time of year

    NASA Astrophysics Data System (ADS)

    Kyper, Nicholas D.

    An extensive heat flux study is performed at Hermit Lake, New Hampshire from May 26, 2010 till November 7, 2010 to determine the effects of the five individual heat fluxes on Hermit Lake and the surrounding amphibian community. Hermit Lake was chosen due to the relatively long meteorological observations record within the White Mountains of New Hampshire, a new lakeside meteorological station, and ongoing phenology studies of the surrounding eco-system. Utilizing meteorological data from the lakeside weather station and moored water temperature sensors, the incident (Qi), blackbody ( Qbnet ), latent (Qe), sensible (Q s), and net (Qn) heat fluxes are calculated. The incident heat flux is the dominate term in the net flux, accounting for 93% of the variance found in Qn and producing a heat gain of ˜ 19x108 J m-2 throughout the period of study. This large gain produces a net gain of heat in the lake until October 1, 2010, where gains by Qi are offset by the large combined losses of Qbnet , Qs, and Qe thereby producing a gradual decline of heat within the lake. The latent and blackbody heat fluxes produce the largest losses of heat in the net heat flux with a total losses of ˜ -8x108 J m-2 and ˜ -7x108 J m-2, respectively. The sensible heat flux is negligible, producing a total minimal loss of ˜ -1x108 J m-2. Overall the net heat produces a net gain of heat of 2x108 J m-2 throughout the study period. Frog calls indicative of breeding are recorded from May 26, 2010 until August 16, 2010. The spring peeper, American toad, and green frog each produced enough actively calling days to be compared to air temperature, surface water temperature, and wind speed data, as well as data from the five heat fluxes. Linear regression analysis reveals that certain water temperature thresholds affect the calling activities of the spring peeper and green frog, while higher wind speeds have a dramatic effect on the calling activities of both the green frog and American toad. All three

  8. Influence and impact of the parametrization of the turbulent air-sea fluxes on atmospheric moisture and convection in the tropics

    NASA Astrophysics Data System (ADS)

    Torres, Olivier; Braconnot, Pascale; Gainusa-Bogdan, Alina; Hourdin, Frédéric; Marti, Olivier; Pelletier, Charles

    2016-04-01

    The turbulent fluxes across the ocean/atmosphere interface represent one of the principal driving forces of the global atmospheric and oceanic circulation and are also responsible for various phenomena like the water supply to the atmospheric column, which itself is extremely important for atmospheric convection. Although the representation of these fluxes has been the subject of major studies, it still remains a very challenging problem. Our aim is to better understand the role of these fluxes in climate change experiments and in the equator-pole redistribution of heat and water by the oceanic and atmospheric circulation. For this, we are developing a methodology starting from idealized 1D experiments and going all the way up to fully coupled ocean-atmosphere simulations of past and future climates. The poster will propose a synthesis of different simulations we have performed with a 1D version of the LMDz atmosphere model towards a first objective of understanding how different parameterizations of the turbulent fluxes affect the moisture content of the atmosphere and the feedback with the atmospheric boundary layer and convection schemes. Air-sea fluxes are not directly resolved by the models because they are subgrid-scale phenomena and are therefore represented by parametrizations. We investigate the differences between several 1D simulations of the TOGA-COARE campaign (1992-1993, Pacific warm pool region), for which 1D boundary conditions and observations are available to test the results of atmospheric models. Each simulation considers a different version of the LMDz model in terms of bulk formula (four) used to compute the turbulent fluxes. We also consider how the representation of gustiness in these parameterizations affects the results. The use of this LMDz test case (very constrained within an idealized framework) allows us to determine how the response of surface fluxes helps to reinforce or damp the atmospheric water vapor content or cloud feedbacks

  9. Characterization of the NOx-Ox relationship in a mountain gap rural area of interchange of air masses southeast of the Metropolitan Area of Mexico City

    NASA Astrophysics Data System (ADS)

    Ruiz Suarez, L.; Garcia-Yee, J.; Torres-JArdon, R.; Barrera Huertas, H.; Torres-Jaramillo, A.; Ortinez, A.

    2013-05-01

    Varying levels of oxidants (Ox = O3 + NO2) with respect to NOx were registered at three sites in a mountain southeast of the Mexico City Metropolitan Area (MCMA) in February and March 2011. The Ox-NOx ratio was used to gain a better understanding of the photochemical and transport processes happening over this mountain pass. Relatively high concentrations of O3 (moving average concentrations of 8 hours) exceeded maximum levels of the World Health Organization, and the European Union. The cumulative exceedances above background level of O3 in the one month-long campaign also exceeded the three months accumulative UN-ECE AOT40 critical level for crop protection. It was observed that the level of Ox in the mountain gap sites consisted of two contributions: One, independent of NOx emissions, extremely dominant and considered equivalent to the regional background O3 concentration; the second and much smaller was dependent of NOx local concentrations. Evidence was found that the oxidation of NO provided the major contribution of NO2 to Ox, rather than direct NO2 emissions. The contribution of regional Ox dominated from midmorning to noon when the boundary layer height began to increase due to sunlight heating of the surface leading to the mixing of higher concentrations of O3 above the nighttime thermal inversion. After noon, when the ozone vertical distribution was uniform, the Ox and O3 concentrations reached their maximum; they were very similar with very low levels of NO2. The analysis of wind data collected at the monitoring sites showed that from mid-morning to early afternoon, a northerly weak flow was common. Afterwards stronger southerly winds became dominant bringing in O3 rich air parcels into the atmospheric basin where MCMA is located. The high regional ozone concentrations add evidence for the need of coordinated air quality management policies for the complete central part of Mexico. Keywords: mountain gap, oxidant, ground level ozone, Central Mexico

  10. An upper limit of muon flux of energies above 100 TeV determined from horizontal air showers observed at Akeno

    NASA Technical Reports Server (NTRS)

    Nagano, M.; Yoshii, H.; Hara, T.; Kamata, K.; Kawaguchi, S.; Kifune, T.

    1985-01-01

    Muon energy spectrum above 100 TeV was determined by observing the extensive air showers (EAS) from the horizontal direction (HAS). No definite muon originated shower of sizes above 100,000 and zenith angles above 60 deg was observed. The upper limits of HAS intensity is 5x10/12 m/2 s/1 sn/1 above 100,000. It is indicated that the upper limit of muon flux above 100 TeV is about 1.3x10/8 m/2 s/1 sr/1 and is in agreement with that expected from the primary spectrum with a knee assuming scaling in the fragmentation region and 40% protons in the primary beam. The critical energy at which muon flux from prompt processes take over that from the conventional process is higher than 100 Tev at horizontal direction.

  11. On the calculation of air-sea fluxes of CO2 in the presence of temperature and salinity gradients

    NASA Astrophysics Data System (ADS)

    Woolf, D. K.; Land, P. E.; Shutler, J. D.; Goddijn-Murphy, L. M.; Donlon, C. J.

    2016-02-01

    The presence of vertical temperature and salinity gradients in the upper ocean and the occurrence of variations in temperature and salinity on time scales from hours to many years complicate the calculation of the flux of carbon dioxide (CO2) across the sea surface. Temperature and salinity affect the interfacial concentration of aqueous CO2 primarily through their effect on solubility with lesser effects related to saturated vapor pressure and the relationship between fugacity and partial pressure. The effects of temperature and salinity profiles in the water column and changes in the aqueous concentration act primarily through the partitioning of the carbonate system. Climatological calculations of flux require attention to variability in the upper ocean and to the limited validity of assuming "constant chemistry" in transforming measurements to climatological values. Contrary to some recent analysis, it is shown that the effect on CO2 fluxes of a cool skin on the sea surface is large and ubiquitous. An opposing effect on calculated fluxes is related to the occurrence of warm layers near the surface; this effect can be locally large but will usually coincide with periods of low exchange. A salty skin and salinity anomalies in the upper ocean also affect CO2 flux calculations, though these haline effects are generally weaker than the thermal effects.

  12. Intraseasonal variability linked to sampling alias in air-sea CO2 fluxes in the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Monteiro, Pedro M. S.; Gregor, Luke; Lévy, Marina; Maenner, Stacy; Sabine, Christopher L.; Swart, Sebastiaan

    2015-10-01

    The Southern Ocean (SO) contributes most of the uncertainty in contemporary estimates of the mean annual flux of carbon dioxide CO2 between the ocean and the atmosphere. Attempts to reduce this uncertainty have aimed at resolving the seasonal cycle of the fugacity of CO2 (fCO2). We use hourly CO2 flux and driver observations collected by the combined deployment of ocean gliders to show that resolving the seasonal cycle is not sufficient to reduce the uncertainty of the flux of CO2 to below the threshold required to reveal climatic trends in CO2 fluxes. This was done by iteratively subsampling the hourly CO2 data set at various time intervals. We show that because of storm-linked intraseasonal variability in the spring-late summer, sampling intervals longer than 2 days alias the seasonal mean flux estimate above the required threshold. Moreover, the regional nature and long-term trends in storm characteristics may be an important influence in the future role of the SO in the carbon-climate system.

  13. Spatio-temporal dynamics of biogeochemical processes and air-sea CO2 fluxes in the Western English Channel based on two years of FerryBox deployment

    NASA Astrophysics Data System (ADS)

    Marrec, P.; Cariou, T.; Latimier, M.; Macé, E.; Morin, P.; Vernet, M.; Bozec, Y.

    2014-12-01

    From January 2011 to January 2013, a FerryBox system was installed on a Voluntary Observing Ship (VOS), which crossed the Western English Channel (WEC) between Roscoff (France) and Plymouth (UK) up to 3 times a day. The FerryBox continuously measured sea surface temperature (SST), sea surface salinity (SSS), dissolved oxygen (DO), fluorescence and partial pressure of CO2 (from April 2012) along the ferry track. Sensors were calibrated based on 714 bimonthly surface samplings with precisions of 0.016 for SSS, 3.3 μM for DO, 0.40 μg L- 1 for Chlorophyll-a (Chl-a) (based on fluorescence measurements) and 5.2 μatm for pCO2. Over the 2 years of deployment (900 crossings), we reported 9% of data lost due to technical issues and quality checked data was obtained to allow investigation of the dynamics of biogeochemical processes related to air-sea CO2 fluxes in the WEC. Based on this unprecedented high-frequency dataset, the physical structure of the WEC was assessed using SST anomalies and the presence of a thermal front was observed around the latitude 49.5°N, which divided the WEC in two main provinces: the seasonally stratified northern WEC (nWEC) and the all-year well-mixed southern WEC (sWEC). These hydrographical properties strongly influenced the spatial and inter-annual distributions of phytoplankton blooms, which were mainly limited by nutrients and light availability in the nWEC and the sWEC, respectively. Air-sea CO2 fluxes were also highly related to hydrographical properties of the WEC between late April and early September 2012, with the sWEC a weak source of CO2 to the atmosphere of 0.9 mmol m- 2 d- 1, whereas the nWEC acted as a sink for atmospheric CO2 of 6.9 mmol m- 2 d- 1. The study of short time-scale dynamics of air-sea CO2 fluxes revealed that an intense and short (less than 10 days) summer bloom in the nWEC contributed to 29% of the CO2 sink during the productive period, highlighting the necessity for high frequency observations in coastal

  14. Methane distribution and sea-to-air flux in the East China Sea during the summer of 2013: Impact of hypoxia

    NASA Astrophysics Data System (ADS)

    Ye, Wangwang; Zhang, Guiling; Zhu, Zhuoyi; Huang, Daji; Han, Yu; Wang, Lan; Sun, Mingshuang

    2016-02-01

    We measured dissolved methane (CH4) at different depths and calculated sea-to-air CH4 fluxes at 65 stations in the East China Sea (ECS) from August 4 to 31 of 2013. CH4 concentrations in surface waters ranged from 2.07 to 27.39 nM and concentrations in bottom waters ranged from 1.76 to 31.35 nM. The concentration of CH4 also decreased with distance from the Changjiang (Yangtze River) Estuary. Analysis of the depth profiles of CH4 indicated great variations among the different stations due to the influence of different water masses and variations in other factors. A region of significant bottom-water hypoxia, with an oxygen level less than 1.5 mg L-1, occurred at the northern region of the ECS. This hypoxic region also had enhanced CH4 production in the water column and sedimentary release of CH4. CH4 saturations in the surface waters ranged from 113% to 1364%, with an average of 317% (±236). We estimated the sea-to-air CH4 flux as 6.5±7.4 μmol m-2 d-1 using the LM86 equation, and as 11.5±11.9 μmol m-2 d-1 using the W92 equation. The overall estimated CH4 emission rate from the ECS was 6.4×10-2 Tg yr-1. The saturation and sea-to-air flux of CH4 varied significantly among the stations. Taken together, our data suggest that the ECS is a net source of atmospheric CH4.

  15. Dynamics of air-sea CO2 fluxes in the northwestern European shelf based on voluntary observing ship and satellite observations

    NASA Astrophysics Data System (ADS)

    Marrec, P.; Cariou, T.; Macé, E.; Morin, P.; Salt, L. A.; Vernet, M.; Taylor, B.; Paxman, K.; Bozec, Y.

    2015-09-01

    From January 2011 to December 2013, we constructed a comprehensive pCO2 data set based on voluntary observing ship (VOS) measurements in the western English Channel (WEC). We subsequently estimated surface pCO2 and air-sea CO2 fluxes in northwestern European continental shelf waters using multiple linear regressions (MLRs) from remotely sensed sea surface temperature (SST), chlorophyll a concentration (Chl a), wind speed (WND), photosynthetically active radiation (PAR) and modeled mixed layer depth (MLD). We developed specific MLRs for the seasonally stratified northern WEC (nWEC) and the permanently well-mixed southern WEC (sWEC) and calculated surface pCO2 with uncertainties of 17 and 16 μatm, respectively. We extrapolated the relationships obtained for the WEC based on the 2011-2013 data set (1) temporally over a decade and (2) spatially in the adjacent Celtic and Irish seas (CS and IS), two regions which exhibit hydrographical and biogeochemical characteristics similar to those of WEC waters. We validated these extrapolations with pCO2 data from the SOCAT and LDEO databases and obtained good agreement between modeled and observed data. On an annual scale, seasonally stratified systems acted as a sink of CO2 from the atmosphere of -0.6 ± 0.3, -0.9 ± 0.3 and -0.5 ± 0.3 mol C m-2 yr-1 in the northern Celtic Sea, southern Celtic sea and nWEC, respectively, whereas permanently well-mixed systems acted as source of CO2 to the atmosphere of 0.2 ± 0.2 and 0.3 ± 0.2 mol C m-2 yr-1 in the sWEC and IS, respectively. Air-sea CO2 fluxes showed important inter-annual variability resulting in significant differences in the intensity and/or direction of annual fluxes. We scaled the mean annual fluxes over these provinces for the last decade and obtained the first annual average uptake of -1.11 ± 0.32 Tg C yr-1 for this part of the northwestern European continental shelf. Our study showed that combining VOS data with satellite observations can be a powerful tool to

  16. Dynamics of air-sea CO2 fluxes in the North-West European Shelf based on Voluntary Observing Ship (VOS) and satellite observations

    NASA Astrophysics Data System (ADS)

    Marrec, P.; Cariou, T.; Macé, E.; Morin, P.; Salt, L. A.; Vernet, M.; Taylor, B.; Paxman, K.; Bozec, Y.

    2015-04-01

    From January 2011 to December 2013, we constructed a comprehensive pCO2 dataset based on voluntary observing ship (VOS) measurements in the Western English Channel (WEC). We subsequently estimated surface pCO2 and air-sea CO2 fluxes in north-west European continental shelf waters using multiple linear regressions (MLRs) from remotely sensed sea surface temperature (SST), chlorophyll a concentration (Chl a), the gas transfer velocity coefficient (K), photosynthetically active radiation (PAR) and modeled mixed layer depth (MLD). We developed specific MLRs for the seasonally stratified northern WEC (nWEC) and the permanently well-mixed southern WEC (sWEC) and calculated surface pCO2 with relative uncertainties of 17 and 16 μatm, respectively. We extrapolated the relationships obtained for the WEC based on the 2011-2013 dataset (1) temporally over a decade and (2) spatially in the adjacent Celtic and Irish Seas (CS and IS), two regions which exhibit hydrographical and biogeochemical characteristics similar to those of WEC waters. We validated these extrapolations with pCO2 data from the SOCAT database and obtained relatively robust results with an average precision of 4 ± 22 μatm in the seasonally stratified nWEC and the southern and northern CS (sCS and nCS), but less promising results in the permanently well-mixed sWEC, IS and Cap Lizard (CL) waters. On an annual scale, seasonally stratified systems acted as a sink of CO2 from the atmosphere of -0.4, -0.9 and -0.4 mol C m-2 year-1 in the nCS, sCS and nWEC, respectively, whereas, permanently well-mixed systems acted as source of CO2 to the atmosphere of 0.2, 0.4 and 0.4 mol C m-2 year-1 in the sWEC, CL and IS, respectively. Air-sea CO2 fluxes showed important inter-annual variability resulting in significant differences in the intensity and/or direction of annual fluxes. We scaled the mean annual fluxes over six provinces for the last decade and obtained the first annual average uptake of -0.95 Tg C year-1 for this

  17. Two approaches to determining the sea-to-air flux of dimethyl sulfide: Satellite ocean color and a photochemical model with atmospheric measurements

    SciTech Connect

    Thompson, A.M.; Esaias, W.E. ); Iverson, R.L. )

    1990-11-20

    Two estimates of the ocean-to-atmosphere flux of dimethyl sulfide (DMS) are presented to determine the feasibility of using remotely sensed data to map the marine sources of a photoreactive trace gas. First, an empirical relationship between chlorophyll a and DMS in surface seawater is used with NASA coastal zone color scanner (CZCS) data for chlorophyll a pigment to derive a mean DMS flux for a region in the tropical North Atlantic for October 1980. This is compared with the sea-to-air flux derived from a one-dimensional photochemical model that reproduces boundary layer concentrations of O{sub 3}, CO, NO, and hydrocarbon s measured on a cruise at the same location and time (Meteor 56/1). Both evaluations of DMS fluxes are in the range (2-7) {times} 10{sup 9} molecules DMS cm{sup {minus}2} s{sup {minus}1} and agree well with fluxes based on the seawater DMS concentration given by Barnard et al. (1982) for the Meteor cruise. The applicability of the results to strategies for satellite remote sensing of the tropospheric sulfur cycle is discussed. For some species (e.g., DMS) surface sensing of sources is feasible, but only in regions and seasons where phytoplankton pigment is a meaningful marker for biogenic emissions. The general applicability of ocean color to DMS determination awaits the development of an algorithm that can extract distributions of DMS emitting species from the optical signal. For other sulfur constituents (e.g., SO{sub 2}, COS) atmospheric measurements are appropriate for determining tropospheric distribution. Wind, moisture, cloud, precipitation, and temperature data are also required for complete characterization of the marine sulfur cycle.

  18. Model-measurement comparison of ammonia bi-directional air-surface exchange fluxes over agricultural fields

    EPA Science Inventory

    Modeling of the bi-directional fluxes (BDFs) of ammonia (NH3) over fertilized soybean and corn canopies was evaluated for three intensive sampling periods: the first, during the summer of 2002 in Warsaw, North Carolina (NC), USA; and the second and third during the summer of 2007...

  19. Axial gap rotating electrical machine

    DOEpatents

    None

    2016-02-23

    Direct drive rotating electrical machines with axial air gaps are disclosed. In these machines, a rotor ring and stator ring define an axial air gap between them. Sets of gap-maintaining rolling supports bear between the rotor ring and the stator ring at their peripheries to maintain the axial air gap. Also disclosed are wind turbines using these generators, and structures and methods for mounting direct drive rotating electrical generators to the hubs of wind turbines. In particular, the rotor ring of the generator may be carried directly by the hub of a wind turbine to rotate relative to a shaft without being mounted directly to the shaft.

  20. Effect of gas-transfer velocity parameterization choice on air-sea CO2 fluxes in the North Atlantic Ocean and the European Arctic

    NASA Astrophysics Data System (ADS)

    Wrobel, Iwona; Piskozub, Jacek

    2016-09-01

    The oceanic sink of carbon dioxide (CO2) is an important part of the global carbon budget. Understanding uncertainties in the calculation of this net flux into the ocean is crucial for climate research. One of the sources of the uncertainty within this calculation is the parameterization chosen for the CO2 gas-transfer velocity. We used a recently developed software toolbox, called the FluxEngine (Shutler et al., 2016), to estimate the monthly air-sea CO2 fluxes for the extratropical North Atlantic Ocean, including the European Arctic, and for the global ocean using several published quadratic and cubic wind speed parameterizations of the gas-transfer velocity. The aim of the study is to constrain the uncertainty caused by the choice of parameterization in the North Atlantic Ocean. This region is a large oceanic sink of CO2, and it is also a region characterized by strong winds, especially in winter but with good in situ data coverage. We show that the uncertainty in the parameterization is smaller in the North Atlantic Ocean and the Arctic than in the global ocean. It is as little as 5 % in the North Atlantic and 4 % in the European Arctic, in comparison to 9 % for the global ocean when restricted to parameterizations with quadratic wind dependence. This uncertainty becomes 46, 44, and 65 %, respectively, when all parameterizations are considered. We suggest that this smaller uncertainty (5 and 4 %) is caused by a combination of higher than global average wind speeds in the North Atlantic (> 7 ms-1) and lack of any seasonal changes in the direction of the flux direction within most of the region. We also compare the impact of using two different in situ pCO2 data sets (Takahashi et al. (2009) and Surface Ocean CO2 Atlas (SOCAT) v1.5 and v2.0, for the flux calculation. The annual fluxes using the two data sets differ by 8 % in the North Atlantic and 19 % in the European Arctic. The seasonal fluxes in the Arctic computed from the two data sets disagree with each

  1. High-speed Air Temperature Measurements in a Closed-path Cell and Quality of CO2 and H2O Fluxes from a Short-tube Gas Analyzer.

    NASA Astrophysics Data System (ADS)

    Burba, G. G.; Kathilankal, J. C.; Fratini, G.

    2015-12-01

    Gas analyzers traditionally used for eddy covariance method measure gas density. When fluxes are calculated, corrections are applied to account for the changes in gas density due to changing temperature and pressure (Ideal Gas Law) and changing water vapor density (Dalton's Law). The new generation of gas analyzers with fast air temperature and pressure measurements in the sampling cell enables on-the-fly calculation of fast dry mole fraction. This significantly simplifies the flux processing because the WPL density terms are no longer required, and leads to the reduction in uncertainties associated with latent and sensible heat flux inputs into the density terms. Traditional closed-path instruments with long intake tubes often can effectively dampen the fast temperature fluctuations in the tube before reaching the measurement cell, thus reducing or eliminating the need for temperature correction for density-based fluxes. But in instruments with a short-tube design, most - but not all - of the temperature fluctuations are attenuated, so calculating unbiased fluxes using fast dry mole fraction requires high-speed precise temperature measurements of the air stream inside the cell. Fast pressure and water vapor content of the sampled air should also be measured in the cell and carefully aligned in time with gas density and sample temperature measurements.In this study we examine the impact of fast-response air temperature measurements in the cell on the calculations of carbon dioxide and water vapor fluxes at different time scales from three different ecosystems. The fast cell air temperature data is filtered mathematically to obtain slower response cell temperature time series, which is used in the calculation of fluxes. This exercise is intended to simulate the use of thicker slower response thermocouples instead of fast response fine wire thermocouples for estimating cell temperature. The directly measured block temperature is also utilized to illustrate the

  2. Variability of 14C reservoir age and air-sea flux of CO2 in the Peru-Chile upwelling region during the past 12,000 years

    NASA Astrophysics Data System (ADS)

    Carré, Matthieu; Jackson, Donald; Maldonado, Antonio; Chase, Brian M.; Sachs, Julian P.

    2016-01-01

    The variability of radiocarbon marine reservoir age through time and space limits the accuracy of chronologies in marine paleo-environmental archives. We report here new radiocarbon reservoir ages (ΔR) from the central coast of Chile (~ 32°S) for the Holocene period and compare these values to existing reservoir age reconstructions from southern Peru and northern Chile. Late Holocene ΔR values show little variability from central Chile to Peru. Prior to 6000 cal yr BP, however, ΔR values were markedly increased in southern Peru and northern Chile, while similar or slightly lower-than-modern ΔR values were observed in central Chile. This extended dataset suggests that the early Holocene was characterized by a substantial increase in the latitudinal gradient of marine reservoir age between central and northern Chile. This change in the marine reservoir ages indicates that the early Holocene air-sea flux of CO2 could have been up to five times more intense than in the late Holocene in the Peruvian upwelling, while slightly reduced in central Chile. Our results show that oceanic circulation changes in the Humboldt system during the Holocene have substantially modified the air-sea carbon flux in this region.

  3. Experimental observations of air-sea parameters and fluxes associated with anomalous event in the Indian Ocean during 1997-1998 El Niño period

    NASA Astrophysics Data System (ADS)

    Ramana, M. V.; Krishnan, Praveena; Muraleedharan Nair, S.; Kunhikrishnan, P. K.

    2004-04-01

    This paper describes the variation of air-sea parameters and fluxes during winter months of 1997 (pre-INDOEX) and 1998 (INDOEX-FFP) using ship-based in situ measurements in the latitude range 15°N to 20°S over the Indian Ocean and Arabian Sea. The 1998 cruise period coincided with one of the strongest El Niño events in the decade over the Pacific Ocean. The tropical Indian Ocean underwent a highly anomalous series of events during 1998 with warm sea surface temperature (SST) anomaly over 2 °C during February 1998 and easterly winds associated with the reversed Walker circulation. In situ observations during 1998 cruise period show that the winds in the Indian Ocean region had basically resumed their climatological state as of March 15, 1998 with lesser wind speeds as El Niño waned. However, the sea surface temperatures in Indian Ocean were found to be high even though climatological state had resumed. The present results are the observational evidence to show that the reduced latent heat flux due to low wind speeds could have contributed to the surface warming in the Indian Ocean. The sensible heat and latent heat fluxes are found to be high during anomalous period due to higher sea surface temperature and wind speeds in comparison to the normal period.

  4. Assessing the Potential to Derive Air-Sea Freshwater Fluxes from Aquarius-Like Observations of Surface Salinity

    NASA Technical Reports Server (NTRS)

    Zhen, Li; Adamec, David

    2009-01-01

    A state-of-the-art numerical model is used to investigate the possibility of determining freshwater flux fields from temporal changes io sea-surface salinity (SSS), a goal of the satellite salinity-measuring mission, Aquarius/SAC-D. Because the estimated advective temporal scale is usually longer than the Aquarius/SAC-D revisit time, the possibility of producing freshwater flux estimates from temporal salinity changes is first examined by using a correlation analysis. For the mean seasonal cycle, the patterns of the correlations between the freshwater fluxes and surface salinity temporal tendencies are mainly zonally oriented, and are highest where the local precipitation is also relatively high. Nonseasonal (deviations from the monthly mean) correlations are highest along mid-latitude moon tracks and are relatively small in the tropics. The complex correlation patterns presented here suggest that a global retrieval of the difference between evaporation and precipitation (E-P) from salinity changes requires more complex techniques than a simple consideration of local balance with surface forcing.

  5. The Influence of Roughness Length on Simulated Surface air Temperature (2 m), Wind (10 m), Precipitation, and Energy and Water Fluxes in Eastern China

    NASA Astrophysics Data System (ADS)

    Zuo, J.; Lu, L.

    2012-12-01

    The heterogeneity of land cover characteristics has significant impact on the land-atmosphere water, energy, and momentum exchanges. The aerodynamic roughness length (z0) is an important surface parameter for estimating surface fluxes in numerical models. This study is to investigate the sensitivity of z0 on weather and climate in Eastern China, which has experienced dramatic growth in the urban areas over the past 30 years. Driven by ERA-40 reanalysis product as atmospheric lateral boundary conditions, Regional Atmospheric Modeling System (RAMS) was used to perform a series of one-year ensemble simulations over the eastern China. Ten sensitivity experiments were conducted by increasing and decreasing vegetation roughness length by 10%, 25%, 50%, 70%, 90%, as well as a control run by using the model's default parameterization of z0, which is derived from a look-up table based on vegetation type. Furthermore, a data assimilation run using the real time z0 map that is derived from MODIS product was carried out, which includes the heteorogenous z0 within the same vegetation type. The difference between the data assimilation run and the default run will help us to understand how remotely sensed land-surface information influences land-atmosphere interactions and mesoscale circulations. The preliminary results show that the bigger the magnitude of z0 changes, the larger the responses in surface air temperatures, wind speeds, and fluxes, except that these changes are opposite in sign with z0 changes. More localized changes occur in the Southeast China than Northeast China, as there are more vegetation cover variations in the south. In addition, z0 has larger effect on spring and summer surface air temperature, and summer sensible heat fluxes. The remote sensing product derived z0 map shows different spatial and temporal distribution when compare to the default z0 distribution, which in turn results in both spatial and seasonal differences in simulated climate variables.

  6. Propagation or failure of detonation across an air gap in an LX-17 column: continuous time-dependent detonation or shock speed using the Embedded Fiber Optic (EFO) technique

    SciTech Connect

    Hare, D E; Chandler, J B; Compton, S M; Garza, R G; Grimsley, D A; Hernandez, A; Villafana, R J; Wade, J T; Weber, S R; Wong, B M; Souers, P C

    2008-01-16

    The detailed history of the shock/detonation wave propagation after crossing a room-temperature-room-pressure (RTP) air gap between a 25.4 mm diameter LX-17 donor column and a 25.4 mm diameter by 25.4 mm long LX-17 acceptor pellet is investigated for three different gap widths (3.07, 2.08, and 0.00 mm) using the Embedded Fiber Optic (EFO) technique. The 2.08 mm gap propagated and the 3.07 mm gap failed and this can be seen clearly and unambiguously in the EFO data even though the 25.4 mm-long acceptor pellet would be considered quite short for a determination by more traditional means such as pins.

  7. Spatial and temporal variability of CO2 fluxes at the sediment-air interface in a tidal flat of a temperate lagoon (Arcachon Bay, France)

    NASA Astrophysics Data System (ADS)

    Migné, Aline; Davoult, Dominique; Spilmont, Nicolas; Ouisse, Vincent; Boucher, Guy

    2016-03-01

    This study aimed to explore the spatial and temporal variability of benthic metabolism in a temperate mesotidal lagoon. This was achieved by measuring fluxes of CO2 in static chambers during emersion, both under light and dark conditions. Three sample sites were selected according to their tidal level (upper or mid), their sediment type (sand or mud) and the presence/absence of the seagrass Zostera noltei. The three sites were investigated at three seasons (end of winter, spring and beginning of autumn). At each site and each season, three benthic chambers were used simultaneously in successive incubations over the emersion period. The sediment chlorophyll-a content varied seasonally in the upper sands (reaching 283 mg.m- 2 in spring) but not in the mid muds (averaging 142 mg m- 2 in bare muds and 186 mg m- 2 in muds covered by seagrass). The maximum sediment CO2-uptake under light was 9.89 mmol m- 2 h- 1 in the mid-bare muds, in early autumn. The maximum sediment CO2-release under darkness was 6.97 mmol m- 2 h- 1 in the mid muds covered by seagrass, in spring. Both CO2-fluxes measured in the light and in the dark increased over periods of emersion. This increase, not related to light nor temperature variations, could be explained by changes in the amount and chemistry of pore water during the air exposure of sediments. The benthic trophic state index, based on the maximum light CO2-flux versus maximum dark CO2-flux ratio, assigned to each site at each season indicated that the sediments were net autotrophic in spring in upper sands and in mid muds covered by seagrass and highly autotrophic in other cases. The most autotrophic sediments were the mid-level bare muds whatever the season. The relevance of this index is discussed compared to carbon annual budget.

  8. Seasonal and interannual variability of sea-air CO2 fluxes in the tropical Atlantic affected by the Amazon River plume

    NASA Astrophysics Data System (ADS)

    Ibánhez, J. Severino P.; Diverrès, Denis; Araujo, Moacyr; Lefèvre, Nathalie

    2015-10-01

    CO2 fugacities obtained from a merchant ship sailing from France to French Guyana were used to explore the seasonal and interannual variability of the sea-air CO2 exchange in the western tropical North Atlantic (TNA; 5-14°N, 41-52°W). Two distinct oceanic water masses were identified in the area associated to the main surface currents, i.e., the North Brazil Current (NBC) and the North Equatorial Current (NEC). The NBC was characterized by permanent CO2 oversaturation throughout the studied period, contrasting with the seasonal pattern identified in the NEC. The NBC retroflection was the main contributor to the North Equatorial Counter Current (NECC), thus spreading into the central TNA, the Amazon River plume, and the CO2-rich waters probably originated from the equatorial upwelling. Strong CO2 undersaturation was associated to the Amazon River plume. Total inorganic carbon drawdown due to biological activity was estimated to be 154 µmol kg-1 within the river plume. As a consequence, the studied area acted as a net sink of atmospheric CO2 (from -72.2 ± 10.2 mmol m-2 month-1 in February to 14.3 ± 4.5 mmol m-2 month-1 in May). This contrasted with the net CO2 efflux estimated by the main global sea-air CO2 flux climatologies. Interannual sea surface temperature changes in the TNA caused by large-scale climatic events could determine the direction and intensity of the sea-air CO2 fluxes in the NEC. Positive temperature anomalies observed in the TNA led to an almost permanent CO2 outgassing in the NEC in 2010.

  9. Performance and emission characteristics of a low heat rejection engine with different air gap thicknesses with Jatropha oil based bio-diesel.

    PubMed

    Murali Krishna, M V S; Sarita, G; Seshagiri Rao, V V R; Chowdary, R P; Ramana Reddy, Ch V

    2010-04-01

    The research work on alternate fuels has been the topic of wider interest in the context of depletion of fossil fuels and increasing of pollution levels of the engines with conventional fossil fuels. Alcohols and vegetable oils are considered to replace diesel fuels as they are renewable in nature. However, use of alcohols in internal combustion engines is limited in India, as these fuels are diverted to PetroChemical industries and hence much emphasis is given to the non-edible vegetable oils as alternate fuels in internal combustion engines. However, the drawbacks of low volatility and high viscosity associated with non-edible vegetable oils call for hot combustion chamber, provided by low heat rejection (LHR) diesel engine. Investigations are carried out on a LHR diesel engine with varied air gap thicknesses and injection pressures with jatropha oil based bio-diesel at normal temperature. Performance is improved with high degree of insulation with LHR engine with vegetable oil in comparison with conventional engine (CE) with pure diesel operation. PMID:21114115

  10. Performance and emission characteristics of a low heat rejection engine with different air gap thicknesses with Jatropha oil based bio-diesel.

    PubMed

    Murali Krishna, M V S; Sarita, G; Seshagiri Rao, V V R; Chowdary, R P; Ramana Reddy, Ch V

    2010-04-01

    The research work on alternate fuels has been the topic of wider interest in the context of depletion of fossil fuels and increasing of pollution levels of the engines with conventional fossil fuels. Alcohols and vegetable oils are considered to replace diesel fuels as they are renewable in nature. However, use of alcohols in internal combustion engines is limited in India, as these fuels are diverted to PetroChemical industries and hence much emphasis is given to the non-edible vegetable oils as alternate fuels in internal combustion engines. However, the drawbacks of low volatility and high viscosity associated with non-edible vegetable oils call for hot combustion chamber, provided by low heat rejection (LHR) diesel engine. Investigations are carried out on a LHR diesel engine with varied air gap thicknesses and injection pressures with jatropha oil based bio-diesel at normal temperature. Performance is improved with high degree of insulation with LHR engine with vegetable oil in comparison with conventional engine (CE) with pure diesel operation.

  11. Sensitivity of modelled sulfate aerosol and its radiative effect on climate to ocean DMS concentration and air-sea flux

    NASA Astrophysics Data System (ADS)

    Tesdal, Jan-Erik; Christian, James R.; Monahan, Adam H.; von Salzen, Knut

    2016-09-01

    Dimethylsulfide (DMS) is a well-known marine trace gas that is emitted from the ocean and subsequently oxidizes to sulfate in the atmosphere. Sulfate aerosols in the atmosphere have direct and indirect effects on the amount of solar radiation reaching the Earth's surface. Thus, as a potential source of sulfate, ocean efflux of DMS needs to be accounted for in climate studies. Seawater concentration of DMS is highly variable in space and time, which in turn leads to high spatial and temporal variability in ocean DMS emissions. Because of sparse sampling (in both space and time), large uncertainties remain regarding ocean DMS concentration. In this study, we use an atmospheric general circulation model with explicit aerosol chemistry (CanAM4.1) and several climatologies of surface ocean DMS concentration to assess uncertainties about the climate impact of ocean DMS efflux. Despite substantial variation in the spatial pattern and seasonal evolution of simulated DMS fluxes, the global-mean radiative effect of sulfate is approximately linearly proportional to the global-mean surface flux of DMS; the spatial and temporal distribution of ocean DMS efflux has only a minor effect on the global radiation budget. The effect of the spatial structure, however, generates statistically significant changes in the global-mean concentrations of some aerosol species. The effect of seasonality on the net radiative effect is larger than that of spatial distribution and is significant at global scale.

  12. Net sea-air CO2 fluxes and modelled pCO2 in the southwestern subtropical Atlantic continental shelf during spring 2010 and summer 2011

    NASA Astrophysics Data System (ADS)

    Ito, Rosane Gonçalves; Garcia, Carlos Alberto Eiras; Tavano, Virginia Maria

    2016-05-01

    Sea-air CO2 fluxes over continental shelves vary substantially in time on both seasonal and sub-seasonal scales, driven primarily by variations in surface pCO2 due to several oceanic mechanisms. Furthermore, coastal zones have not been appropriately considered in global estimates of sea-air CO2 fluxes, despite their importance to ecology and to productivity. In this work, we aimed to improve our understanding of the role played by shelf waters in controlling sea-air CO2 fluxes by investigating the southwestern Atlantic Ocean (21-35°S) region, where physical, chemical and biological measurements were made on board the Brazilian R. V. Cruzeiro do Sul during late spring 2010 and early summer 2011. Features such as discharge from the La Plata River, intrusions of tropical waters on the outer shelf due to meandering and flow instabilities of the Brazil Current, and coastal upwelling in the Santa Marta Grande Cape and São Tomé Cape were detected by both in situ measurements and ocean colour and thermal satellite imagery. Overall, shelf waters in the study area were a source of CO2 to the atmosphere, with an average of 1.2 mmol CO2 m-2 day-1 for the late spring and 11.2 mmol CO2 m-2 day-1 for the early summer cruises. The spatial variability in ocean pCO2 was associated with surface ocean properties (temperature, salinity and chlorophyll-a concentration) in both the slope and shelf waters. Empirical algorithms for predicting temperature-normalized surface ocean pCO2 as a function of surface ocean properties were shown to perform well in both shelf and slope waters, except (a) within cyclonic eddies produced by baroclinic instability of the Brazil Current as detected by satellite SST imagery and (b) in coastal upwelling regions. In these regions, surface ocean pCO2 values were higher as a result of upwelled CO2-enriched subsurface waters. Finally, a pCO2 algorithm based on both sea surface temperature and surface chlorophyll-a was developed that enabled the spatial

  13. Quantifying the air-sea CO2 flux at a time-series in the Eastern Tropical Atlantic

    NASA Astrophysics Data System (ADS)

    Lefevre, Nathalie; Veleda, Doris; Araujo, Moacyr; Caniaux, Guy

    2016-04-01

    Hourly fCO2 is recorded at a time-series at the PIRATA buoy located at 6oS 10oW in the eastern tropical Atlantic since June 2006. This site is located south and west of the seasonal Atlantic cold tongue and is affected by its propagation from June to September. Using an alkalinity-salinity relationship determined for the eastern tropical Atlantic and the observed fCO2, pH and the inorganic carbon concentration are calculated. The time-series of fCO2 exhibits strong intraseasonal, seasonal and interannual variability. On seasonal timescales, the variations of fCO2 and pH are mostly controlled by sea surface salinity. At interannual timescales, some important differences appear in 2011-2012: lower fCO2 and fluxes are observed from September to December 2011 and are explained by higher advection of salty waters at the mooring. In early 2012, the anomaly is still present and is associated with lower sea surface temperatures. No significant long-term trend is detected over the period 2006-2013 on CO2 and any other physical parameter. However, as atmospheric fCO2 is increasing over time, the outgassing of CO2 is reduced over the period 2006-2013 as the flux is mainly controlled by the difference of fCO2 between the ocean and the atmosphere. A longer time-series is required to determine if any significant trend exists in this region.

  14. Surface Ocean pCO2 Seasonality and Sea-Air CO2 Flux Estimates for the North American East Coast

    NASA Technical Reports Server (NTRS)

    Signorini, Sergio; Mannino, Antonio; Najjar, Raymond G., Jr.; Friedrichs, Marjorie A. M.; Cai, Wei-Jun; Salisbury, Joe; Wang, Zhaohui Aleck; Thomas, Helmuth; Shadwick, Elizabeth

    2013-01-01

    Underway and in situ observations of surface ocean pCO2, combined with satellite data, were used to develop pCO2 regional algorithms to analyze the seasonal and interannual variability of surface ocean pCO2 and sea-air CO2 flux for five physically and biologically distinct regions of the eastern North American continental shelf: the South Atlantic Bight (SAB), the Mid-Atlantic Bight (MAB), the Gulf of Maine (GoM), Nantucket Shoals and Georges Bank (NS+GB), and the Scotian Shelf (SS). Temperature and dissolved inorganic carbon variability are the most influential factors driving the seasonality of pCO2. Estimates of the sea-air CO2 flux were derived from the available pCO2 data, as well as from the pCO2 reconstructed by the algorithm. Two different gas exchange parameterizations were used. The SS, GB+NS, MAB, and SAB regions are net sinks of atmospheric CO2 while the GoM is a weak source. The estimates vary depending on the use of surface ocean pCO2 from the data or algorithm, as well as with the use of the two different gas exchange parameterizations. Most of the regional estimates are in general agreement with previous studies when the range of uncertainty and interannual variability are taken into account. According to the algorithm, the average annual uptake of atmospheric CO2 by eastern North American continental shelf waters is found to be between 3.4 and 5.4 Tg C/yr (areal average of 0.7 to 1.0 mol CO2 /sq m/yr) over the period 2003-2010.

  15. Climatological mean and decadal change in surface ocean pCO 2, and net sea-air CO 2 flux over the global oceans

    NASA Astrophysics Data System (ADS)

    Takahashi, Taro; Sutherland, Stewart C.; Wanninkhof, Rik; Sweeney, Colm; Feely, Richard A.; Chipman, David W.; Hales, Burke; Friederich, Gernot; Chavez, Francisco; Sabine, Christopher; Watson, Andrew; Bakker, Dorothee C. E.; Schuster, Ute; Metzl, Nicolas; Yoshikawa-Inoue, Hisayuki; Ishii, Masao; Midorikawa, Takashi; Nojiri, Yukihiro; Körtzinger, Arne; Steinhoff, Tobias; Hoppema, Mario; Olafsson, Jon; Arnarson, Thorarinn S.; Tilbrook, Bronte; Johannessen, Truls; Olsen, Are; Bellerby, Richard; Wong, C. S.; Delille, Bruno; Bates, N. R.; de Baar, Hein J. W.

    2009-04-01

    A climatological mean distribution for the surface water pCO 2 over the global oceans in non-El Niño conditions has been constructed with spatial resolution of 4° (latitude) ×5° (longitude) for a reference year 2000 based upon about 3 million measurements of surface water pCO 2 obtained from 1970 to 2007. The database used for this study is about 3 times larger than the 0.94 million used for our earlier paper [Takahashi et al., 2002. Global sea-air CO 2 flux based on climatological surface ocean pCO 2, and seasonal biological and temperature effects. Deep-Sea Res. II, 49, 1601-1622]. A time-trend analysis using deseasonalized surface water pCO 2 data in portions of the North Atlantic, North and South Pacific and Southern Oceans (which cover about 27% of the global ocean areas) indicates that the surface water pCO 2 over these oceanic areas has increased on average at a mean rate of 1.5 μatm y -1 with basin-specific rates varying between 1.2±0.5 and 2.1±0.4 μatm y -1. A global ocean database for a single reference year 2000 is assembled using this mean rate for correcting observations made in different years to the reference year. The observations made during El Niño periods in the equatorial Pacific and those made in coastal zones are excluded from the database. Seasonal changes in the surface water pCO 2 and the sea-air pCO 2 difference over four climatic zones in the Atlantic, Pacific, Indian and Southern Oceans are presented. Over the Southern Ocean seasonal ice zone, the seasonality is complex. Although it cannot be thoroughly documented due to the limited extent of observations, seasonal changes in pCO 2 are approximated by using the data for under-ice waters during austral winter and those for the marginal ice and ice-free zones. The net air-sea CO 2 flux is estimated using the sea-air pCO 2 difference and the air-sea gas transfer rate that is parameterized as a function of (wind speed) 2 with a scaling factor of 0.26. This is estimated by inverting

  16. Inference of super-resolution ocean pCO2 and air-sea CO2 fluxes from non-linear and multiscale processing methods

    NASA Astrophysics Data System (ADS)

    Hernández-Carrasco, Ismael; Sudre, Joel; Garçon, Veronique; Yahia, Hussein; Dewitte, Boris; Garbe, Christoph; Illig, Séréna; Montes, Ivonne; Dadou, Isabelle; Paulmier, Aurélien; Butz, André

    2014-05-01

    In recent years the role of submesoscale activity is emerging as being more and more important to understand global ocean properties, for instance, for accurately estimating the sources and sinks of Greenhouse Gases (GHGs) at the air-sea interface. The scarcity of oceanographic cruises and the lack of available satellite products for GHG concentrations at high resolution prevent from obtaining a global assessment of their spatial variability at small scales. In this work we develop a novel method to reconstruct maps of CO2 fluxes at super resolution (4km) using SST and ocean colour data at this resolution, and CarbonTracker CO2 fluxes data at low resolution (110 km). The responsible process for propagating the information between scales is related to cascading properties and multiscale organization, typical of fully developed turbulence. The methodology, based on the Microcanonical Multifractal Formalism, makes use, from the knowledge of singularity exponents, of the optimal wavelet for the determination of the energy injection mechanism between scales. We perform a validation analysis of the results of our algorithm using pCO2 ocean data from in-situ measurements in the upwelling region off Namibia.

  17. Synoptic evaluation of carbon cycling in Beaufort Sea during summer: contrasting river inputs, ecosystem metabolism and air-sea CO2 fluxes

    NASA Astrophysics Data System (ADS)

    Forest, A.; Coupel, P.; Else, B.; Nahavandian, S.; Lansard, B.; Raimbault, P.; Papakyriakou, T.; Gratton, Y.; Fortier, L.; Tremblay, J.-É.; Babin, M.

    2013-10-01

    The accelerated decline in Arctic sea ice combined with an ongoing trend toward a more dynamic atmosphere is modifying carbon cycling in the Arctic Ocean. A critical issue is to understand how net community production (NCP; the balance between gross primary production and community respiration) responds to changes and modulates air-sea CO2 fluxes. Using data collected as part of the ArcticNet-Malina 2009 expedition in southeastern Beaufort Sea (Arctic Ocean), we synthesize information on sea ice, wind, river, water column properties, metabolism of the planktonic food web, organic carbon fluxes and pools, as well as air-sea CO2 exchange, with the aim of identifying indices of ecosystem response to environmental changes. Data were analyzed to develop a non-steady-state carbon budget and an assessment of NCP against air-sea CO2 fluxes. The mean atmospheric forcing was a mild upwelling-favorable wind (~5 km h-1) blowing from the N-E and a decaying ice cover (<80% concentration) was observed beyond the shelf, the latter being fully exposed to the atmosphere. We detected some areas where the surface mixed layer was net autotrophic owing to high rates of primary production (PP), but the ecosystem was overall net heterotrophic. The region acted nonetheless as a sink for atmospheric CO2 with a mean uptake rate of -2.0 ± 3.3 mmol C m-2d-1. We attribute this discrepancy to: (1) elevated PP rates (>600 mg C m-2d-1) over the shelf prior to our survey, (2) freshwater dilution by river runoff and ice melt, and (3) the presence of cold surface waters offshore. Only the Mackenzie River delta and localized shelf areas directly affected by upwelling were identified as substantial sources of CO2 to the atmosphere (>10mmol C m-2d-1). Although generally <100 mg C m-2d-1, daily PP rates cumulated to a total PP of ~437.6 × 103 t C, which was roughly twice higher than the organic carbon delivery by river inputs (~241.2 × 103 t C). Subsurface PP represented 37.4% of total PP for the

  18. [Summer Greenhouse Gases Exchange Flux Across Water-air Interface in Three Water Reservoirs Located in Different Geologic Setting in Guangxi, China].

    PubMed

    Li, Jian-hong; Pu, Jun-bing; Sun, Ping-an; Yuan, Dao-xian; Liu, Wen; Zhang, Tao; Mo, Xue

    2015-11-01

    Due to special hydrogeochemical characteristics of calcium-rich, alkaline and DIC-rich ( dissolved inorganic carbon) environment controlled by the weathering products from carbonate rock, the exchange characteristics, processes and controlling factors of greenhouse gas (CO2 and CH4) across water-air interface in karst water reservoir show obvious differences from those of non-karst water reservoir. Three water reservoirs (Dalongdong reservoir-karst reservoir, Wulixia reservoir--semi karst reservoir, Si'anjiang reservoir-non-karst reservoir) located in different geologic setting in Guangxi Zhuang Autonomous Region, China were chosen to reveal characteristics and controlling factors of greenhouse gas exchange flux across water-air interface. Two common approaches, floating chamber (FC) and thin boundary layer models (TBL), were employed to research and contrast greenhouse gas exchange flux across water-air interface from three reservoirs. The results showed that: (1) surface-layer water in reservoir area and discharging water under dam in Dalongdong water reservoir were the source of atmospheric CO2 and CH4. Surface-layer water in reservoir area in Wulixia water reservoir was the sink of atmospheric CO2 and the source of atmospheric CH4, while discharging water under dam was the source of atmospheric CO2 and CH4. Surface-layer water in Si'anjiang water reservoir was the sink of atmospheric CO2 and source of atmospheric CH4. (2) CO2 and CH4 effluxes in discharging water under dam were much more than those in surface-layer water in reservoir area regardless of karst reservoir or non karst reservoir. Accordingly, more attention should be paid to the CO2 and CH4 emission from discharging water under dam. (3) In the absence of submerged soil organic matters and plants, the difference of CH4 effluxes between karst groundwater-fed reservoir ( Dalongdong water reservoir) and non-karst area ( Wulixia water reservoir and Si'anjiang water reservoir) was less. However, CO2

  19. [Summer Greenhouse Gases Exchange Flux Across Water-air Interface in Three Water Reservoirs Located in Different Geologic Setting in Guangxi, China].

    PubMed

    Li, Jian-hong; Pu, Jun-bing; Sun, Ping-an; Yuan, Dao-xian; Liu, Wen; Zhang, Tao; Mo, Xue

    2015-11-01

    Due to special hydrogeochemical characteristics of calcium-rich, alkaline and DIC-rich ( dissolved inorganic carbon) environment controlled by the weathering products from carbonate rock, the exchange characteristics, processes and controlling factors of greenhouse gas (CO2 and CH4) across water-air interface in karst water reservoir show obvious differences from those of non-karst water reservoir. Three water reservoirs (Dalongdong reservoir-karst reservoir, Wulixia reservoir--semi karst reservoir, Si'anjiang reservoir-non-karst reservoir) located in different geologic setting in Guangxi Zhuang Autonomous Region, China were chosen to reveal characteristics and controlling factors of greenhouse gas exchange flux across water-air interface. Two common approaches, floating chamber (FC) and thin boundary layer models (TBL), were employed to research and contrast greenhouse gas exchange flux across water-air interface from three reservoirs. The results showed that: (1) surface-layer water in reservoir area and discharging water under dam in Dalongdong water reservoir were the source of atmospheric CO2 and CH4. Surface-layer water in reservoir area in Wulixia water reservoir was the sink of atmospheric CO2 and the source of atmospheric CH4, while discharging water under dam was the source of atmospheric CO2 and CH4. Surface-layer water in Si'anjiang water reservoir was the sink of atmospheric CO2 and source of atmospheric CH4. (2) CO2 and CH4 effluxes in discharging water under dam were much more than those in surface-layer water in reservoir area regardless of karst reservoir or non karst reservoir. Accordingly, more attention should be paid to the CO2 and CH4 emission from discharging water under dam. (3) In the absence of submerged soil organic matters and plants, the difference of CH4 effluxes between karst groundwater-fed reservoir ( Dalongdong water reservoir) and non-karst area ( Wulixia water reservoir and Si'anjiang water reservoir) was less. However, CO2

  20. PAH and PCB in the Baltic -- A budget approach including fluxes, occurrence and concentration variability in air, suspended and settling particulates in water, surface sediments and river water

    SciTech Connect

    Broman, D.; Axelman, J.; Bandh, C.; Ishaq, R.; Naef, C.; Pettersen, H.; Zebuehr, Y.

    1995-12-31

    In order to study the fate and occurrence of two groups of hydrophobic compounds in the Baltic aquatic environment a large number of samples were collected from the southern Baltic proper to the northern Bothnian Bay for the analyses of polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs). The following sample matrices were collected; bottom surface sediments (0--1 cm, collected with gravity corer), settling particulate matter (collected with sediment traps), open water samples and over water samples (suspended particulates and dissolved fraction sampled by filtration) and air samples (aerosols and vapor phase sampled by filtration). All samples (except over water and air) were collected at open sea in the Baltic. The analyses results have been used to make a model approach on the whole Baltic and to elucidate different aspects of the behavior of PAHs and PCBs in the Baltic, such as the occurrence of the compounds in water and sediment, the total content as well as the concentration variabilities over such a large geographical area, Further, the data on settling particulate matter as well as the air concentration data were used to estimate the total fluxes of PAHs and PCBs to the bottoms of the Baltic and t o the total water area of the Baltic, respectively. Further, data on the PAH and PCB content in river water from four major rivers provides rough estimates of the riverine input to the Baltic. The dynamics of PAHs and PCBs within the water mass have also been studied in terms of settling velocities and residence times in the water mass for these type of compounds in the open Baltic.

  1. A Modeling Study of Irrigation Effects on Surface Fluxes and Land-Air-Cloud Interactions in the Southern Great Plains

    SciTech Connect

    Qian, Yun; Huang, Maoyi; Yang, Ben; Berg, Larry K.

    2013-06-13

    In this study, the authors incorporate an operational-like irrigation scheme into the Noah land surface model as part of the Weather Research and Forecasting Model (WRF). A series of simulations, with and without irrigation, is conducted over the Southern Great Plains (SGP) for an extremely dry (2006) and wet (2007) year. The results show that including irrigation reduces model bias in soil moisture and surface latent heat (LH) and sensible heat (SH) fluxes, especially during a dry year. Irrigation adds additional water to the surface, leading to changes in the planetary boundary layer. The increase in soil moisture leads to increases in the surface evapotranspiration and near-surface specific humidity but decreases in the SH and surface temperature. Those changes are local and occur during daytime. There is an irrigation-induced decrease in both the lifting condensation level (ZLCL) and mixed-layer depth. The decrease in ZLCL is larger than the decrease in mixed-layer depth, suggesting an increasing probability of shallow clouds. The simulated changes in precipitation induced by irrigation are highly variable in space, and the average precipitation over the SGP region only slightly increases. A high correlation is found among soil moisture, SH, and ZLCL. Larger values of soil moisture in the irrigated simulation due to irrigation in late spring and summer persist into the early fall, suggesting that irrigation-induced soil memory could last a few weeks to months. The results demonstrate the importance of irrigation parameterization for climate studies and improve the process-level understanding on the role of human activity in modulating land–air–cloud interactions.

  2. Carbon dioxide fluxes across the air-water interface and its impact on carbon availability in aquatic systems

    SciTech Connect

    Portielje, R.; Lijklema, L.

    1995-06-01

    Diffusion of CO{sub 2} across the air-water interface was analyzed with a model that simulates both transport and reaction of CO{sub 2} in a stagnant boundary layer. The atmospheric C influx was determined in relation to several environmental variables: pH, total dissolved inorganic C, temperature, and the thickness of the stagnant boundary layer in relation to ambient windspeed. We used the model to calculate the atmospheric CO{sub 2} influx into experimental ditches for a period of 6 to 8 months, starting in early spring. Three of the six ditches were dominated by aquatic macrophytes and three by benthic algae. Each series received three levels of external N and P input. A comparison with net C assimilation during the same period, as estimated from continuous oxygen measurements, showed that, especially in the ditches dominated by submersed macrophytes, a sizable fraction of the C requirements during this period could have been obtained from atmospheric CO{sub 2}. In the ditches dominated by benthic algae, this fraction was considerably less, but nonetheless substantial, and was related to the level of N and P loading. Increased primary production due to enhanced external N and P loading increased the atmospheric C input due to the resultant higher pH values. The trophic state with respect to N and P and the availability of C are therefore interrelated. 25 refs., 8 figs., 5 tabs.

  3. Mind the Gap

    NASA Astrophysics Data System (ADS)

    Staedter, Tracy

    2007-03-01

    A new finding gets scientists one step closer to understanding what causes the gap in the Van Allen radiation belts. The discovery could help better predict fluxes of energetic particles that have the potential for damaging spacecraft and satellites and harming astronauts. An improved understanding could also give space physicists better insight into the radiation belts of other planets, including Jupiter, Saturn, Uranus, and Neptune, all of which have strong magnetic fields.

  4. A method to determine true air temperature fluctuations in clouds with liquid water fraction and estimate water droplet effect on the calculations of the spectral structure of turbulent heat fluxes in cumulus clouds based on aircraft data

    NASA Astrophysics Data System (ADS)

    Strunin, Alexander M.; Zhivoglotov, Dmitriy N.

    2014-03-01

    Liquid water droplets could distort aircraft temperature measurements in clouds, leading to errors in calculated heat fluxes and incorrect flux distribution pattern. The estimation of cloud droplet effect on the readings of the high-frequency aircraft thermometer employed at the Central Aerological Observatory (CAO) was based on an experimental study of the sensor in a wind tunnel, using an air flow containing liquid water droplets. Simultaneously, calculations of the distribution of speed and temperature in a flow through the sensitive element of the sensor were fulfilled. This permitted estimating the coefficient of water content effect on temperature readings. Another way of estimating cloud droplet effect was based on the analysis of data obtained during aircraft observations of cumulus clouds in a tropical zone (Cuba Island). As a result, a method of correcting air temperature and recovering true air temperature fluctuations inside clouds was developed. This method has provided consistent patterns of heat flux distribution in a cumulus area. Analysis of the results of aircraft observations of cumulus clouds with temperature correction fulfilled has permitted investigation of the spectral structure of the fields of air temperature and heat fluxes to be performed in cumulus zones based on wavelet transformation. It is shown that mesoscale eddies (over 500 m in length) were the main factor of heat exchange between a cloud and the ambient space. The role of turbulence only consisted in mixing inside the cloud.

  5. Modeling of the anthropogenic heat flux and its effect on regional meteorology and air quality over the Yangtze River Delta region, China

    NASA Astrophysics Data System (ADS)

    Xie, Min; Liao, Jingbiao; Wang, Tijian; Zhu, Kuanguang; Zhuang, Bingliang; Han, Yong; Li, Mengmeng; Li, Shu

    2016-05-01

    Anthropogenic heat (AH) emissions from human activities caused by urbanization can affect the city environment. Based on the energy consumption and the gridded demographic data, the spatial distribution of AH emission over the Yangtze River Delta (YRD) region is estimated. Meanwhile, a new method for the AH parameterization is developed in the WRF/Chem model, which incorporates the gridded AH emission data with the seasonal and diurnal variations into the simulations. By running this upgraded WRF/Chem for 2 typical months in 2010, the impacts of AH on the meteorology and air quality over the YRD region are studied. The results show that the AH fluxes over the YRD have been growing in recent decades. In 2010, the annual-mean values of AH over Shanghai, Jiangsu and Zhejiang are 14.46, 2.61 and 1.63 W m-2, respectively, with the high value of 113.5 W m-2 occurring in the urban areas of Shanghai. These AH emissions can significantly change the urban heat island and urban-breeze circulations in the cities of the YRD region. In Shanghai, 2 m air temperature increases by 1.6 °C in January and 1.4 °C in July, the PBLH (planetary boundary layer height) rises up by 140 m in January and 160 m in July, and 10 m wind speed is enhanced by 0.7 m s-1 in January and 0.5 m s-1 in July, with a higher increment at night. The enhanced vertical movement can transport more moisture to higher levels, which causes the decrease in water vapor at ground level and the increase in the upper PBL (planetary boundary layer), and thereby induces the accumulative precipitation to increase by 15-30 % over the megacities in July. The adding of AH can impact the spatial and vertical distributions of the simulated pollutants as well. The concentrations of primary air pollutants decrease near the surface and increase at the upper levels, due mainly to the increases in PBLH, surface wind speed and upward air vertical movement. But surface O3 concentrations increase in the urban areas, with maximum

  6. Relationships Between the Bulk-Skin Sea Surface Temperature Difference, Wind, and Net Air-Sea Heat Flux

    NASA Technical Reports Server (NTRS)

    Emery, William J.; Castro, Sandra L.; Lindstrom, Eric (Technical Monitor)

    2002-01-01

    The primary purpose of this project was to evaluate and improve models for the bulk-skin temperature difference to the point where they could accurately and reliably apply under a wide variety of environmental conditions. To accomplish this goal, work was conducted in three primary areas. These included production of an archive of available data sets containing measurements of the skin and bulk temperatures and associated environmental conditions, evaluation of existing skin layer models using the compiled data archive, and additional theoretical work on the development of an improved model using the data collected under diverse environmental conditions. In this work we set the basis for a new physical model of renewal type, and propose a parameterization for the temperature difference across the cool skin of the ocean in which the effects of thermal buoyancy, wind stress, and microscale breaking are all integrated by means of the appropriate renewal time scales. Ideally, we seek to obtain a model that will accurately apply under a wide variety of environmental conditions. A summary of the work in each of these areas is included in this report. A large amount of work was accomplished under the support of this grant. The grant supported the graduate studies of Sandra Castro and the preparation of her thesis which will be completed later this year. This work led to poster presentations at the 1999 American Geophysical Union Fall Meeting and 2000 IGARSS meeting. Additional work will be presented in a talk at this year's American Meteorological Society Air-Sea Interaction Meeting this May. The grant also supported Sandra Castro during a two week experiment aboard the R/P Flip (led by Dr. Andrew Jessup of the Applied Physics Laboratory) to help obtain additional shared data sets and to provide Sandra with a fundamental understanding of the physical processes needed in the models. In a related area, the funding also partially supported Dr. William Emery and Daniel

  7. Gap Junctions

    PubMed Central

    Nielsen, Morten Schak; Axelsen, Lene Nygaard; Sorgen, Paul L.; Verma, Vandana; Delmar, Mario; Holstein-Rathlou, Niels-Henrik

    2013-01-01

    Gap junctions are essential to the function of multicellular animals, which require a high degree of coordination between cells. In vertebrates, gap junctions comprise connexins and currently 21 connexins are known in humans. The functions of gap junctions are highly diverse and include exchange of metabolites and electrical signals between cells, as well as functions, which are apparently unrelated to intercellular communication. Given the diversity of gap junction physiology, regulation of gap junction activity is complex. The structure of the various connexins is known to some extent; and structural rearrangements and intramolecular interactions are important for regulation of channel function. Intercellular coupling is further regulated by the number and activity of channels present in gap junctional plaques. The number of connexins in cell-cell channels is regulated by controlling transcription, translation, trafficking, and degradation; and all of these processes are under strict control. Once in the membrane, channel activity is determined by the conductive properties of the connexin involved, which can be regulated by voltage and chemical gating, as well as a large number of posttranslational modifications. The aim of the present article is to review our current knowledge on the structure, regulation, function, and pharmacology of gap junctions. This will be supported by examples of how different connexins and their regulation act in concert to achieve appropriate physiological control, and how disturbances of connexin function can lead to disease. © 2012 American Physiological Society. Compr Physiol 2:1981-2035, 2012. PMID:23723031

  8. Distributions and sea-to-air fluxes of chloroform, trichloroethylene, tetrachloroethylene, chlorodibromomethane and bromoform in the Yellow Sea and the East China Sea during spring.

    PubMed

    He, Zhen; Yang, Gui-Peng; Lu, Xiao-Lan; Zhang, Hong-Hai

    2013-06-01

    Halocarbons including chloroform (CHCl3), trichloroethylene (C2HCl3), tetrachloroethylene (C2Cl4), chlorodibromomethane (CHBr2Cl) and bromoform (CHBr3) were measured in the Yellow Sea (YS) and the East China Sea (ECS) during spring 2011. The influences of chlorophyll a, salinity and nutrients on the distributions of these gases were examined. Elevated levels of these gases in the coastal waters were attributed to anthropogenic inputs and biological release by phytoplankton. The vertical distributions of these gases in the water column were controlled by different source strengths and water masses. Using atmospheric concentrations measured in spring 2012 and seawater concentrations obtained from this study, the sea-to-air fluxes of these gases were estimated. Our results showed that the emissions of C2HCl3, C2Cl4, CHBr2Cl, and CHBr3 from the study area could account for 16.5%, 10.5%, 14.6%, and 3.5% of global oceanic emissions, respectively, indicating that the coastal shelf may contribute significantly to the global oceanic emissions of these gases.

  9. Mercury in the marine boundary layer and seawater of the South China Sea: Concentrations, sea/air flux, and implication for land outflow

    NASA Astrophysics Data System (ADS)

    Fu, Xuewu; Feng, Xinbin; Zhang, Gan; Xu, Weihai; Li, Xiangdong; Yao, Hen; Liang, Peng; Li, Jun; Sommar, Jonas; Yin, Runsheng; Liu, Na

    2010-03-01

    Using R/V Shiyan 3 as a sampling platform, measurements of gaseous elemental mercury (GEM), surface seawater total mercury (THg), methyl mercury (MeHg), and dissolved gaseous mercury (DGM) were carried out above and in the South China Sea (SCS). Measurements were collected for 2 weeks (10 to 28 August 2007) during an oceanographic expedition, which circumnavigated the northern SCS from Guangzhou (Canton), Hainan Inland, the Philippines, and back to Guangzhou. GEM concentrations over the northern SCS ranged from 1.04 to 6.75 ng m-3 (mean: 2.62 ng m-3, median: 2.24 ng m-3). The spatial distribution of GEM was characterized by elevated concentrations near the coastal sites adjacent to mainland China and lower concentrations at stations in the open sea. Trajectory analysis revealed that high concentrations of GEM were generally related to air masses from south China and the Indochina peninsula, while lower concentrations of GEM were related to air masses from the open sea area, reflecting great Hg emissions from south China and Indochina peninsula. The mean concentrations of THg, MeHg, and DGM in surface seawater were 1.2 ± 0.3 ng L-1, 0.12 ± 0.05 ng L-1, and 36.5 ± 14.9 pg L-1, respectively. In general, THg and MeHg levels in the northern SCS were higher compared to results reported from most other oceans/seas. Elevated THg levels in the study area were likely attributed to significant Hg delivery from surrounding areas of the SCS primarily via atmospheric deposition and riverine input, whereas other sources like in situ production by various biotic and abiotic processes may be important for MeHg. Average sea/air flux of Hg in the study area was estimated using a gas exchange method (4.5 ± 3.4 ng m-2 h-1). This value was comparable to those from other coastal areas and generally higher than those from open sea environments, which may be attributed to the reemission of Hg previously transported to this area.

  10. Synoptic evaluation of carbon cycling in the Beaufort Sea during summer: contrasting river inputs, ecosystem metabolism and air-sea CO2 fluxes

    NASA Astrophysics Data System (ADS)

    Forest, A.; Coupel, P.; Else, B.; Nahavandian, S.; Lansard, B.; Raimbault, P.; Papakyriakou, T.; Gratton, Y.; Fortier, L.; Tremblay, J.-É.; Babin, M.

    2014-05-01

    The accelerated decline in Arctic sea ice and an ongoing trend toward more energetic atmospheric and oceanic forcings are modifying carbon cycling in the Arctic Ocean. A critical issue is to understand how net community production (NCP; the balance between gross primary production and community respiration) responds to changes and modulates air-sea CO2 fluxes. Using data collected as part of the ArcticNet-Malina 2009 expedition in the southeastern Beaufort Sea (Arctic Ocean), we synthesize information on sea ice, wind, river, water column properties, metabolism of the planktonic food web, organic carbon fluxes and pools, as well as air-sea CO2 exchange, with the aim of documenting the ecosystem response to environmental changes. Data were analyzed to develop a non-steady-state carbon budget and an assessment of NCP against air-sea CO2 fluxes. During the field campaign, the mean wind field was a mild upwelling-favorable wind (~ 5 km h-1) from the NE. A decaying ice cover (< 80% concentration) was observed beyond the shelf, the latter being fully exposed to the atmosphere. We detected some areas where the surface mixed layer was net autotrophic owing to high rates of primary production (PP), but the ecosystem was overall net heterotrophic. The region acted nonetheless as a sink for atmospheric CO2, with an uptake rate of -2.0 ± 3.3 mmol C m-2 d-1 (mean ± standard deviation associated with spatial variability). We attribute this discrepancy to (1) elevated PP rates (> 600 mg C m-2 d-1) over the shelf prior to our survey, (2) freshwater dilution by river runoff and ice melt, and (3) the presence of cold surface waters offshore. Only the Mackenzie River delta and localized shelf areas directly affected by upwelling were identified as substantial sources of CO2 to the atmosphere (> 10 mmol C m-2 d-1). Daily PP rates were generally < 100 mg C m-2 d-1 and cumulated to a total PP of ~ 437.6 × 103 t C for the region over a 35-day period. This amount was about twice the

  11. [Research advances in ecosystem flux].

    PubMed

    Zhang, Xudong; Peng, Zhenhua; Qi, Lianghua; Zhou, Jinxing

    2005-10-01

    To develop the long-term localized observation and investigation on ecosystem flux is of great importance. On the basis of generalizing the concepts and connotations of ecosystem flux, this paper introduced the construction and development histories of Global Flux Networks, Regional Flux Networks (Ameri-Flux, Euro-Flux and Asia-Flux) and China-Flux, as well as the main methodologies, including micrometeorological methods (such as eddy correlation method, mass balance method, energy balance method and air dynamic method)and chamber methods (static and dynamic chamber methods), and their basic operation principles. The research achievements, approaches and advances of CO2, N2O, CH4, and heat fluxes in forest ecosystem, farmland ecosystem, grassland ecosystem and water ecosystem were also summarized. In accordance with the realities and necessities of ecosystem flux research in China, some suggestions and prospects were put forward.

  12. Soil-air greenhouse gas fluxes influenced by farming practices in reservoir drawdown area: A case at the Three Gorges Reservoir in China.

    PubMed

    Li, Zhe; Zhang, Zengyu; Lin, Chuxue; Chen, Yongbo; Wen, Anbang; Fang, Fang

    2016-10-01

    The Three Gorges Reservoir (TGR) in China has large water level variations, creating about 393 km(2) of drawdown area seasonally. Farming practices in drawdown area during the low water level period is common in the TGR. Field experiments on soil-air greenhouse gas (GHG) emissions in fallow grassland, peanut field and corn field in reservoir drawdown area at Lijiaba Bay of the Pengxi River, a tributary of the Yangtze River in the TGR were carried out from March through September 2011. Experimental fields in drawdown area had the same land use history. They were adjacent to each other horizontally at a narrow range of elevation i.e. 167-169 m, which assured that they had the same duration of reservoir inundation. Unflooded grassland with the same land-use history was selected as control for study. Results showed that mean value of soil CO2 emissions in drawdown area was 10.38 ± 0.97 mmol m(-2) h(-1). The corresponding CH4 fluxes and N2O fluxes were -8.61 ± 2.15 μmol m(-2) h(-1) and 3.42 ± 0.80 μmol m(-2) h(-1). Significant differences and monthly variations among land uses in treatments of drawdown area and unflooded grassland were evident. These were impacted by the change in soil physiochemical properties which were alerted by reservoir operation and farming. Particularly, N-fertilization in corn field stimulated N2O emissions from March to May. In terms of global warming potentials (GWP), corn field in drawdown area had the maximum GWP mainly due to N-fertilization. Gross GWP in peanut field in drawdown area was about 7% lower than that in fallow grassland. Compared to unflooded grassland, reservoir operation created positive net effect on GHG emissions and GWPs in drawdown area. However, selection of crop species, e.g. peanut, and best practices in farming, e.g. prohibiting N-fertilization, could potentially mitigate GWPs in drawdown area. In the net GHG emissions evaluation in the TGR, farming practices in the drawdown area shall be taken

  13. Soil-air greenhouse gas fluxes influenced by farming practices in reservoir drawdown area: A case at the Three Gorges Reservoir in China.

    PubMed

    Li, Zhe; Zhang, Zengyu; Lin, Chuxue; Chen, Yongbo; Wen, Anbang; Fang, Fang

    2016-10-01

    The Three Gorges Reservoir (TGR) in China has large water level variations, creating about 393 km(2) of drawdown area seasonally. Farming practices in drawdown area during the low water level period is common in the TGR. Field experiments on soil-air greenhouse gas (GHG) emissions in fallow grassland, peanut field and corn field in reservoir drawdown area at Lijiaba Bay of the Pengxi River, a tributary of the Yangtze River in the TGR were carried out from March through September 2011. Experimental fields in drawdown area had the same land use history. They were adjacent to each other horizontally at a narrow range of elevation i.e. 167-169 m, which assured that they had the same duration of reservoir inundation. Unflooded grassland with the same land-use history was selected as control for study. Results showed that mean value of soil CO2 emissions in drawdown area was 10.38 ± 0.97 mmol m(-2) h(-1). The corresponding CH4 fluxes and N2O fluxes were -8.61 ± 2.15 μmol m(-2) h(-1) and 3.42 ± 0.80 μmol m(-2) h(-1). Significant differences and monthly variations among land uses in treatments of drawdown area and unflooded grassland were evident. These were impacted by the change in soil physiochemical properties which were alerted by reservoir operation and farming. Particularly, N-fertilization in corn field stimulated N2O emissions from March to May. In terms of global warming potentials (GWP), corn field in drawdown area had the maximum GWP mainly due to N-fertilization. Gross GWP in peanut field in drawdown area was about 7% lower than that in fallow grassland. Compared to unflooded grassland, reservoir operation created positive net effect on GHG emissions and GWPs in drawdown area. However, selection of crop species, e.g. peanut, and best practices in farming, e.g. prohibiting N-fertilization, could potentially mitigate GWPs in drawdown area. In the net GHG emissions evaluation in the TGR, farming practices in the drawdown area shall be taken

  14. Gap Resolution

    2009-06-16

    With the continued improvements of next generation DNA sequencing technologies and their advantages over traditional Sanger sequencing, the Joint Genome Institute (JGI) has modified its sequencing pipeline to take advantage of the benefits of such technologies. Currently, standard 454 Titanium, paired end 454 Titanium, and Illumina GAll data are generated for all microbial projects and then assembled using draft assemblies at a much greater throughput than before. However, it also presents us with new challenges.more » In addition to the increased throughput, we also have to deal with a larger number of gaps in the Newbler genome assemblies. Gaps in these assemblies are usually caused by repeats (Newbler collapses repeat copies into individual contigs, thus creating gaps), strong secondary structures, and artifacts of the PCR process (specific to 454 paired end libraries). Some gaps in draft assemblies can be resolved merely by adding back the collapsed data from repeats. To expedite gap closure and assembly improvement on large numbers of these assemblies, we developed software to address this issue.« less

  15. Model estimating the effect of marginal ice zone processes on the phytoplankton primary production and air-sea flux of CO2 in the Barents Sea

    NASA Astrophysics Data System (ADS)

    Dvornikov, Anton; Sein, Dmitry; Ryabchenko, Vladimir; Gorchakov, Victor; Martjyanov, Stanislav

    2016-04-01

    This study is aimed to assess the impact of sea ice on the primary production of phytoplankton (PPP) and air-sea CO2 flux in the Barents Sea. To get the estimations, we apply a three-dimensional eco-hydrodynamic model based on the Princeton Ocean Model which includes: 1) a module of sea ice with 7 categories, and 2) the 11-component module of marine pelagic ecosystem developed in the St. Petersburg Branch, Institute of Oceanology. The model is driven by atmospheric forcing, prescribed from the reanalysis NCEP / NCAR, and conditions on the open sea boundary, prescribed from the regional model of the atmosphere-ocean-sea ice-ocean biogeochemistry, developed at Max Planck Institute for Meteorology, Hamburg. Comparison of the model results for the period 1998-2007 with satellite data showed that the model reproduces the main features of the evolution of the sea surface temperature, seasonal changes in the ice extent, surface chlorophyll "a" concentration and PPP in the Barents Sea. Model estimates of the annual PPP for whole sea, APPmod, appeared in 1.5-2.3 times more than similar estimates, APPdata, from satellite data. The main reasons for this discrepancy are: 1) APPdata refers to the open water, while APPmod, to the whole sea area (under the pack ice and marginal ice zone (MIZ) was produced 16 - 38% of PPP); and 2) values of APPdata are underestimated because of the subsurface chlorophyll maximum. During the period 1998-2007, the modelled maximal (in the seasonal cycle) sea ice area has decreased by 15%. This reduction was accompanied by an increase in annual PPP of the sea at 54 and 63%, based, respectively, on satellite data and the model for the open water. According to model calculations for the whole sea area, the increase is only 19%. Using a simple 7-component model of oceanic carbon cycle incorporated into the above hydrodynamic model, the CO2 exchange between the atmosphere and sea has been estimated in different conditions. In the absence of biological

  16. Air-Sea CO2 fluxes and NEP changes in a Baja California Coastal Lagoon during the anomalous North Pacific warm condition in 2014

    NASA Astrophysics Data System (ADS)

    Ávila López, M. D. C.; Martin Hernandez-Ayon, J. M.; Camacho-Ibar, V.; Sandoval Gil, J.; Mejía-Trejo, A.; Félix-Bermudez, A.; Pacheco-Ruiz, I.

    2015-12-01

    The present study examines the temporal variability of seawater carbonate chemistry and air-sea CO2 fluxes (FCO2) in a Baja California Mediterranean-climate coastal lagoon. This study was carried out from Nov-2013 to Nov-2014, a period in which anomalous warm conditions were present in the North Pacific Ocean influenced the local oceanography in the adjacent coastal waters off Baja California. These ocean conditions resulted on a negative anomaly of upwelling index, which led to summer-like season (weak upwelling condition) that could be observed in the response of carbon dynamics and metabolic status in San Quintín Bay. Minor changes in dissolved inorganic carbon (DIC) concentration during spring months (~100 µmol kg-1) where observed and were associated to biological processes within the lagoon. High DIC (~2200 µmol kg-1), pCO2 (~800 μatm), and minimum pH (~7.8) values were observed in summer, reflecting the predominance of respiration processes apparently mostly linked to the remineralization of sedimentary organic matter supplied from macroalgal blooms. San Quintín Bay acted as a weak source of CO2 to the atmosphere during the study period, with maximum value observed in July (~10 mmol C m-2 d-1). Temporal biomass production of macroalgae contributed to about 50% of total FCO2 estimated in spring-summer seasons, that was a potencial internal source of organic matter to fuel respiration processes in San Quintín Bay. Eelgrass metabolism contributes in a lower degree in total FCO2. During the anomalous ocean conditions in 2014, the lagoon switched seasonally between net heterotrophy and net autotrophy during the study period, where photosynthesis and respiration processes in the lagoon were closer to a balance. Whole-system metabolism and FCO2 clearly indicated the strong dependence of San Quintín Bay on upwelling conditions and benthic metabolism activity, which was mainly controlled by dominant primary producer communities.

  17. Global representation of tropical cyclone-induced ocean thermal changes using Argo data - Part 2: Estimating air-sea heat fluxes and ocean heat content changes

    NASA Astrophysics Data System (ADS)

    Cheng, L.; Zhu, J.; Sriver, R. L.

    2014-12-01

    We use Argo temperature data to examine changes in ocean heat content (OHC) and air-sea heat fluxes induced by tropical cyclones (TC)s on a global scale. A footprint technique that analyzes the vertical structure of cross-track thermal responses along all storm tracks during the period 2004-2012 is utilized (see part I). We find that TCs are responsible for 1.87 PW (11.05 W m-2 when averaging over the global ocean basin) of heat transfer annually from the global ocean to the atmosphere during storm passage (0-3 days) on a global scale. Of this total, 1.05 ± 0.20 PW (4.80 ± 0.85 W m-2) is caused by Tropical storms/Tropical depressions (TS/TD) and 0.82 ± 0.21 PW (6.25 ± 1.5 W m-2) is caused by hurricanes. Our findings indicate that ocean heat loss by TCs may be a substantial missing piece of the global ocean heat budget. Net changes in OHC after storm passage is estimated by analyzing the temperature anomalies during wake recovery following storm events (4-20 days after storm passage) relative to pre-storm conditions. Results indicate the global ocean experiences a 0.75 ± 0.25 PW (5.98 ± 2.1W m-2) net heat gain annually for hurricanes. In contrast, under TS/TD conditions, ocean experiences 0.41 ± 0.21 PW (1.90 ± 0.96 W m-2) net ocean heat loss, suggesting the overall oceanic thermal response is particularly sensitive to the intensity of the event. The net ocean heat uptake caused by all storms is 0.34 PW.

  18. Linking Air Quality and Watershed Models for Environmental Assessments: Analysis of the Effects of Model-Specific Precipitation Estimates on Calculated Water Flux

    EPA Science Inventory

    Directly linking air quality and watershed models could provide an effective method for estimating spatially-explicit inputs of atmospheric contaminants to watershed biogeochemical models. However, to adequately link air and watershed models for wet deposition estimates, each mod...

  19. Nitrous oxide and methane in Atlantic and Mediterranean waters in the Strait of Gibraltar: Air-sea fluxes and inter-basin exchange

    NASA Astrophysics Data System (ADS)

    de la Paz, M.; Huertas, I. E.; Flecha, S.; Ríos, A. F.; Pérez, F. F.

    2015-11-01

    The global ocean plays an important role in the overall budget of nitrous oxide (N2O) and methane (CH4), as both gases are produced within the ocean and released to the atmosphere. However, for large parts of the open and coastal oceans there is little or no spatial data coverage for N2O and CH4. Hence, a better assessment of marine emissions estimates is necessary. As a contribution to remedying the scarcity of data on marine regions, N2O and CH4 concentrations have been determined in the Strait of Gibraltar at the ocean Fixed Time series (GIFT). During six cruises performed between July 2011 and November 2014 samples were collected at the surface and various depths in the water column, and subsequently measured using gas chromatography. From this we were able to quantify the temporal variability of the gas air-sea exchange in the area and examine the vertical distribution of N2O and CH4 in Atlantic and Mediterranean waters. Results show that surface Atlantic waters are nearly in equilibrium with the atmosphere whereas deeper Mediterranean waters are oversaturated in N2O, and a gradient that gradually increases with depth was detected in the water column. Temperature was found to be the main factor responsible for the seasonal variability of N2O in the surface layer. Furthermore, although CH4 levels did not reveal any feature clearly associated with the circulation of water masses, vertical distributions showed that higher concentrations are generally observed in the Atlantic layer, and that the deeper Mediterranean waters are considerably undersaturated (by up to 50%). Even though surface waters act as a source of atmospheric N2O during certain periods, on an annual basis the net N2O flux in the Strait of Gibraltar is only 0.35 ± 0.27 μmol m-2 d-1, meaning that these waters are almost in a neutral status with respect to the atmosphere. Seasonally, the region behaves as a slight sink for atmospheric CH4 in winter and as a source in spring and fall. Approximating

  20. Muon and neutrino fluxes

    NASA Technical Reports Server (NTRS)

    Edwards, P. G.; Protheroe, R. J.

    1985-01-01

    The result of a new calculation of the atmospheric muon and neutrino fluxes and the energy spectrum of muon-neutrinos produced in individual extensive air showers (EAS) initiated by proton and gamma-ray primaries is reported. Also explained is the possibility of detecting atmospheric nu sub mu's due to gamma-rays from these sources.

  1. In situ evaluation of air-sea CO2 gas transfer velocity in an inner estuary using eddy covariance - with a special focus on the importance of using reliable CO2-fluxes

    NASA Astrophysics Data System (ADS)

    Jørgensen, E. T.; Sørensen, L. L.; Jensen, B.; Sejr, M. K.

    2012-04-01

    The air-sea exchange of CO2 or CO2 flux is driven by the difference in the partial pressure of CO2 in the water and the atmosphere (ΔpCO2), the solubility of CO2 (K0) and the gas transfer velocity (k) (Wanninkhof et al., 2009;Weiss, 1974) . ΔpCO2 and K0 are determined with relatively high precision and it is estimated that the biggest uncertainty when modelling the air-sea flux is the parameterization of k. As an example; the estimated global air-sea flux increases by 70 % when using the parameterization by Wanninkhof and McGillis (1999) instead of Wanninkhof (1992) (Rutgersson et al., 2008). In coastal areas the uncertainty is even higher and only few studies have focused on determining transfer velocity for the coastal waters and even fewer on estuaries (Borges et al., 2004;Rutgersson et al., 2008). The transfer velocity (k600) of CO2 in the inner estuary of Roskilde Fjord, Denmark was investigated using eddy covariance CO2 fluxes (ECM) and directly measured ΔpCO2 during May and June 2010. The data was strictly sorted to heighten the certainty of the results and the outcome was; DS1; using only ECM, and DS2; including the inertial dissipation method (IDM). The inner part of Roskilde Fjord showed to be a very biological active CO2 sink and preliminary results showed that the average k600 was more than 10 times higher than transfer velocities from similar studies of other coastal areas. The much higher transfer velocities were estimated to be caused by the greater fetch and shallower water in Roskilde Fjord, which indicated that turbulence in both air and water influence k600. The wind speed parameterization of k600 using DS1 showed some scatter but when including IDM the r2 of DS2 reached 0.93 with an exponential parameterization, where U10 was based on the Businger-Dyer relationships using friction velocity and atmospheric stability. This indicates that some of the uncertainties coupled with CO2 fluxes calculated by the ECM are removed when including the IDM.

  2. Dry and wet deposition of 7Be, 210Pb and 137Cs in Monaco air during 1998-2010: seasonal variations of deposition fluxes.

    PubMed

    Pham, Mai K; Povinec, Pavel P; Nies, Hartmut; Betti, Maria

    2013-06-01

    Temporal variations of (7)Be, (210)Pb and (137)Cs activity concentrations in precipitation in Monaco from 1998 to 2010 showed that maxima of (7)Be and (210)Pb deposition fluxes coincide with the peaks of precipitation amounts observed in different months of a year, and most of (7)Be and (210)Pb was washout from the atmosphere by precipitation. The seasonal variations were not uniform from year to year, and the amount of precipitation controlled the deposition fluxes of (7)Be and (210)Pb, which was not the case for (137)Cs. The fractional deposition fluxes of (7)Be and (210)Pb in different seasons were in the order fall > spring > winter > summer, while the fractional amount of precipitation followed the order fall > winter > spring > summer. The fractional deposition fluxes of (137)Cs were found in the order spring > fall > summer > winter. The precipitation-normalized deposition fluxes of (7)Be, (210)Pb and (137)Cs were generally higher during summer. The highest (7)Be/(210)Pb activity ratio was observed in 2010, and the smallest one in 2001, following the influence of the modulation of cosmic rays on the production rates of (7)Be in the atmosphere by solar activity. Activity ratios of (7)Be/(210)Pb observed in winter and fall were generally higher than during summer and spring.

  3. An examination of boundary layer structure under the influence of the gap winds in Urumqi, China, during air pollution episode in winter.

    PubMed

    Li, Xia; Xia, Xiangao; Xin, Yu; Ma, Yufen; Yang, Jing; Li, Jinglin; Yang, Xinghua

    2012-01-01

    Tethered-sonde measurements of atmospheric profiles were performed at Urumuqi, capital of the Xinjiang Uyghur Autonomous Region of China, from 29 December 2008 to 14 January 2009. The data were used to examine the boundary layer structure during this severe air pollution period. Diurnal evolution of local wind flow near Urumqi was simulated using the fifth-generation Pennsylvania State University-National Center for Atmospheric Research (NCAR) Mesoscale Model (MM5). Measurements from operational radiosonde data showed that a southeasterly elevated low-level jet often intruded upon Urumqi through the middle Tianshan Mountain pass to the south of the city. The tethered-sonde measurements showed that calm and northwesterly winds prevailed near the surface in Urumqi, whereas the southeasterly winds of relatively higher speed were dominant above approximately 400 m. Both temperature inversion and humidity inversion frequently occured during day and nighttime. Temperature inversion intensity could sharply rise as the stronger elevated southeasterly gale (ESEG) happened. Model simulations showed that the winds near the surface around Urumqi remained calm during nighttime and developed toward the mountains during daytime. As cool airflow in the basin confronted the southeasterly winds from the pass in the lower layer, they formed a convergence line around Urumqi city, which was not favor for dilution of air pollutants.

  4. Atmospheric air diffuse array-needles dielectric barrier discharge excited by positive, negative, and bipolar nanosecond pulses in large electrode gap

    NASA Astrophysics Data System (ADS)

    Zhang, Li; Yang, De-zheng; Wang, Wen-chun; Liu, Zhi-jie; Wang, Sen; Jiang, Peng-chao; Zhang, Shuai

    2014-09-01

    In this paper, positive, negative, and bipolar nanosecond pulses are employed to generate stable and diffuse discharge plasma using array needles-plate electrode configuration at atmospheric pressure. A comparison study of discharge images, electrical characteristics, optical emission spectra, and plasma vibrational temperature and rotational temperatures in three pulsed polarity discharges is carried on under different discharge conditions. It is found that bipolar pulse is beneficial to the excitation of diffuse dielectric barrier discharge, which can generate a room temperature plasma with more homogeneous and higher discharge intensity compared with unipolar discharges. Under the condition of 6 mm electrode gap distance, 26 kV pulse peak voltage, and 150 Hz pulse repetition rate, the emission intensity of N2 (C3Πu → B3Πg) of the bipolar pulsed discharge is 4 times higher than the unipolar discharge (both positive and negative), while the plasma gas temperature is kept at 300 K, which is about 10-20 K lower than the unipolar discharge plasma.

  5. Sensitivity analysis of an Ocean Carbon Cycle Model in the North Atlantic: an investigation of parameters affecting the air-sea CO2 flux, primary production and export of detritus

    NASA Astrophysics Data System (ADS)

    Scott, V.; Kettle, H.; Merchant, C. J.

    2010-12-01

    The sensitivity of the biological parameters in a nutrient-phytoplankton-zooplankton-detritus (NPZD) model in the calculation of the air-sea CO2 flux, primary production and detrital export is analysed. The NPZD model is the Hadley Centre Ocean Carbon Cycle model (HadOCC) from the UK Met Office, used in the Hadley Centre Coupled Model 3 (HadCM3) and FAst Met Office and Universities Simulator (FAMOUS) GCMs. Here, HadOCC is coupled to the 1-D General Ocean Turbulence Model (GOTM) and forced with European Centre for Medium-Range Weather Forecasting meteorology to undertake a sensitivity analysis of its twenty biological parameters. Analyses are performed at three sites in the EuroSITES European Ocean Observatory Network: the Central Irminger Sea (60° N 40° W), the Porcupine Abyssal Plain (49° N 16° W) and the European Station for Time series in the Ocean Canary Islands (29° N 15° W) to assess variability in parameter sensitivities at different locations in the North Atlantic Ocean. Reasonable changes to the values of key parameters are shown to have a large effect on the calculation of the air-sea CO2 flux, primary production, and export of biological detritus to the deep ocean. Changes in the values of key parameters have a greater effect in more productive regions than in less productive areas. We perform the analysis using one-at-a-time perturbations and using a statistical emulator, and compare results. The most sensitive parameters are generic to many NPZD ocean ecosystem models. The air-sea CO2 flux is most influenced by variation in the parameters that control phytoplankton growth, detrital sinking and carbonate production by phytoplankton (the rain ratio). Primary production is most sensitive to the parameters that define the shape of the photosythesis-irradiance curve. Export production is most sensitive to the parameters that control the rate of detrital sinking and the remineralisation of detritus.

  6. ) Mold Fluxes

    NASA Astrophysics Data System (ADS)

    Seo, Myung-Duk; Shi, Cheng-Bin; Cho, Jung-Wook; Kim, Seon-Hyo

    2014-10-01

    The effects of basicity (CaO/SiO2), B2O3, and Li2O addition on the crystallization behaviors of lime-silica-based mold fluxes have been investigated by non-isothermal differential scanning calorimetry (DSC), field emission scanning electron microscopy, X-ray diffraction (XRD), and single hot thermocouple technique. It was found that the crystallization temperature of cuspidine increased with increasing the basicity of mold fluxes. The crystallization of wollastonite was suppressed with increasing the mold flux basicity due to the enhancement of cuspidine crystallization. The addition of B2O3 suppresses the crystallization of mold flux. The crystallization temperature of mold flux decreases with Li2O addition. The size of cuspidine increases, while the number of cuspidine decreases with increasing mold flux basicity. The morphology of cuspidine in mold fluxes with lower basicity is largely dendritic. The dendritic cuspidine in mold fluxes is composed of many fine cuspidine crystals. On the contrary, in mold fluxes with higher basicity, the cuspidine crystals are larger in size with mainly faceted morphology. The crystalline phase evolution was also calculated using a thermodynamic database, and compared with the experimental results determined by DSC and XRD. The results of thermodynamic calculation of crystalline phase formation are in accordance with the results determined by DSC and XRD.

  7. Air Ejection by a Flux of Particles of a Bulk Material in a Vertical Porous Pipe with a Bypass Cylindrical Chamber

    NASA Astrophysics Data System (ADS)

    Averkova, O. A.; Logachev, I. N.; Logachev, K. I.

    2015-07-01

    Hydrodynamic equations have been derived for a fl ux of particles free falling in an air-filled circular porous pipe which is surrounded by a cylindrical bypass chamber. In these equations, the reverse influence of air on the particles' dynamics is disregarded. Numerical and analytical investigations of the derived equations made it possible to establish the regularities of change in the velocity of ejected air in the porous chute and in the pressure in the bypass chamber along the chute length as a function of the porosity of the walls and the dimensions of the chamber, and also on the ejection number. A rational range has been determined for ejection parameters ensuring the greatest reduction in the ejection volume due to the recycling of air.

  8. Measuring surface fluxes in CAPE

    NASA Technical Reports Server (NTRS)

    Kanemasu, E. T.; D-Shah, T.; Nie, Dalin

    1992-01-01

    Two stations (site 1612 and site 2008) were operated by the University of Georgia group from 6 July 1991 to 18 August 1991. The following data were collected continuously: surface energy fluxes (i.e., net radiation, soil heat fluxes, sensible heat flux and latent heat flux), air temperature, vapor pressure, soil temperature (at 1 cm depth), and precipitation. Canopy reflectance and light interception data were taken three times at each site between 6 July and 18 August. Soil moisture content was measured twice at each site.

  9. Development of an Agricultural Fertilizer Modeling System for Bi-Directional Ammonia Fluxes in the Community Multiscale Air Quality (CMAQ) Model

    EPA Science Inventory

    Atmospheric ammonia (NH3) plays an important role in fine-mode aerosol formation. Accurate estimates of ammonia from both human and natural emissions can reduce uncertainties in air quality modeling. The majority of ammonia anthropogenic emissions come from the agricul...

  10. Closed Gap Slug Calorimeter for Plasma Stream Characterization

    NASA Technical Reports Server (NTRS)

    Nawaz, Anuscheh; Gorbunov, Sergey; Terrazas-Salinas, Imelda; Jones, Steven M.

    2012-01-01

    Slug calorimeters are used in sheer and stagnation mode to characterize heat flux levels for high enthalpy streams. The traditional design features a gap between slug and holder, which can be of concern in these convective heat flux environments. The challenge is to develop a calorimeter that closes the gap to gas flow, but largely maintains thermal insulation of the slug. The work presented herein introduces two new slug calorimeter designs featuring a closed gap. This is done using either aerogel as a filler or press fitting the slug with a disk. The designs were verified and compared to the baseline calorimeter design under radiative heat flux. Building on this, the calorimeters were exposed to convective heat flux in the arc-jet facilities. Results from the new designs and conclusions on the impact of the gap in convective heat flux will be shown.

  11. The effect of photoemission on the streamer development and propagation in short uniform gaps

    NASA Astrophysics Data System (ADS)

    Georghiou, G. E.; Morrow, R.; Metaxas, A. C.

    2001-01-01

    Results are presented for the time evolution of photoemission in a 0.1 cm parallel-plane gap in atmospheric pressure air when a positive dc voltage is applied at one of the electrodes. The hydrodynamic set of equations is solved using the finite-element flux-corrected transport method in two dimensions. The time evolution of the electron distribution at the cathode and the variation of the spread of the electrons are examined during the avalanche, the avalanche-to-streamer transition and streamer propagation stages. Finally, the effect of the variation of the photoemission coefficient on the field distribution and the current waveform are presented.

  12. Numerical Simulation of Supersonic Gap Flow

    PubMed Central

    Jing, Xu; Haiming, Huang; Guo, Huang; Song, Mo

    2015-01-01

    Various gaps in the surface of the supersonic aircraft have a significant effect on airflows. In order to predict the effects of attack angle, Mach number and width-to-depth ratio of gap on the local aerodynamic heating environment of supersonic flow, two-dimensional compressible Navier-Stokes equations are solved by the finite volume method, where convective flux of space term adopts the Roe format, and discretization of time term is achieved by 5-step Runge-Kutta algorithm. The numerical results reveal that the heat flux ratio is U-shaped distribution on the gap wall and maximum at the windward corner of the gap. The heat flux ratio decreases as the gap depth and Mach number increase, however, it increases as the attack angle increases. In addition, it is important to find that chamfer in the windward corner can effectively reduce gap effect coefficient. The study will be helpful for the design of the thermal protection system in reentry vehicles. PMID:25635395

  13. Carbonate chemistry and air-sea CO2 flux at a fixed point in a NW Mediterranean Bay, Villefranche-sur-Mer, France

    NASA Astrophysics Data System (ADS)

    De Carlo, E. H.; Mousseau, L.; Passafiume, O.; Drupp, P. S.; Gattuso, J.

    2011-12-01

    The purpose of the Service d'Observation de la Rade de Villefranche-sur-Mer (SO-RADE) is to study the temporal variability of hydrological conditions as well as the abundance and composition of holo- and meroplankton at a fixed station in the bay of Villefranche-sur-Mer, North West Mediterranean. The weekly data collected at this site, designated as "Point B (43° 41.10'N - 7° 18.94'E), since 1957 are recognized as a long-term time series describing the evolution of the hydrological conditions in a coastal environment. Since 2007, historical measurements of hydrological and biological conditions have been complemented by measurements of the CO2-carbonate system parameters. In this contribution we present CO2-carbonate system parameters and ancillary data for the period 2007-2010. The data are evaluated in the context of the physical and biogeochemical processes that contribute to the fluxes of CO2 between the ocean and atmosphere. Seasonal cycles of seawater pCO2 are controlled principally by variations in temperature, showing maxima in the summer and minima during the winters. Normalization of pCO2 to the mean seawater temperature (18oC) results in an apparent reversal of the seasonal cycle with maxima observed in the winters and minima in the summers, consistent with a control of pCO2 by primary productivity. Calculations of "instantaneous fluxes" of CO2 between the ocean and atmosphere show this area to be primarily a weak source of CO2 to the atmosphere during the summer and a weak sink during the winter and near neutral overall (range: -0.3 to +0.3 mmol CO2 m-2 h-1, average: 0.02 mmol CO2 m-2 h-1). We will also provide projections of errors incurred from the estimation of annualized fluxes of CO2 based on weekly measurements relative to daily and high-frequency (3 h) data such as those obtained at the Hawaii Kilo Nalu coastal time series station, which shows similar behavior to the Point B location despite significant differences in climate and hydrological

  14. Aircraft trace gas measurements during the London 2012 Olympics: Air quality and emission fluxes derived from sampling upwind and downwind of a megacity

    NASA Astrophysics Data System (ADS)

    Allen, G.; O'Shea, S.; Muller, J.; Jones, B.; O'Sullivan, D.; Lee, J. D.; Bauguitte, S.; Gallagher, M. W.; Percival, C.; Barratt, B.; McQuaid, J. B.; Illingworth, S.

    2013-12-01

    This study presents airborne in situ and remote sensing measurements recorded during July and August 2012, across the period of the London 2012 Summer Olympics and simultaneous with the Clear air for London (ClearfLo) ground-based measurement and modelling campaign. Through long-term (2-year) and intensive observation periods (Winter 2011 and Summer 2012), the ClearfLo programme aims to better understand emissions, as well as the chemical, dynamical and micro-meteorological processes which modulate air quality in the London urban environment - an important risk factor for both acute and chronic health effects. The work presented here focuses on two contrasting case studies within the summer ClearfLo period: 30 July 2012 and 9 August 2012, representing relatively clean background and polluted background cases, respectively, and characterised by well-mixed Atlantic westerly maritime inflow in the former and stagnant air (high pressure) in the latter. Measurements of CO, CO2, CH4, N2O, O3, HCN, and other gases measured on board the UK Facility for Airborne Atmospheric Measurement (FAAM) BAe-146 aircraft will be presented and interpreted, with emphasis on observed concentration gradients and tracer-tracer correlations as well as airmass vertical structure and airmass history upwind and downwind of central London in each case. By applying a simple advective model and making use of vertically resolved thermodynamic and composition data, we are able to derive emission strengths for these gases that are representative of the total enclosed surface area. Example emissions for these two cases range between 6x105 kg(C)/hr and 9x105 kg(C)/hr for CO2, and ~0.6x105 kg(C)/hr for CH4. This airborne sampling methodology highlights the unique utility of aircraft measurements to routinely and climatologically characterise emissions from area sources such as cities, and points to future missions to target localised hotspots and distributed point sources.

  15. Enforcement of Levitation Force by Capturing Magnetic Flux between YBa2Cu3O7-x Superconductor Bulk and Permanent Magnet

    NASA Astrophysics Data System (ADS)

    Song, Daniel; Jang, Hyungkwan; Kim, Se Bin; Han, Young Hee; Park, Byung Jun; Sung, Tae Hyun

    2012-09-01

    An iron block was placed on a permanent magnet (PM) as a path to capture the magnetic flux between a high-temperature superconductor (HTS) bulk and a PM. The effects of the magnetic flux for different iron block thicknesses (0, 2, 4, and 6 mm), configurations, and dimensions were experimentally determined. The optimal conditions for increasing the levitation force, which increased with decreasing air gap between the iron block and the PM, and with increasing iron block thickness, were determined. As the area of the iron block decreased, the levitation force increased, reaching a saturation point. Some iron block configurations acted as a path to capture the magnetic flux, and a higher levitation force was observed for a certain gap distance. Software simulation results support the obtained experimental results.

  16. Carbon Fluxes on the Florida shelf

    NASA Astrophysics Data System (ADS)

    Robbins, L. L.; Knorr, P. O.; Liu, X. S.; Byrne, R.; Gledhill, D. K.

    2008-12-01

    Lack of baseline data on carbonate saturation state and pCO2 fluxes on the west Florida shelf, a low- gradient calcium carbonate platform, constrains the ability of managers and scientists to predict aspects of ecosystem change. Ecosystem change may result from a number of factors, such as climate change, ocean acidification, riverine and groundwater contribution, and biogeochemical cycling. Maps and models of pCO2 fluxes and carbonate saturation state are needed for the Florida shelf where significant decline of carbonate ecosystems, fishery habitats, and calcifying organisms are predicted over the next decade. To address critical information gaps and an incomplete understanding of nearshore carbon flux variability, the U.S. Geological Survey (USGS) is conducting a field campaign with the University of South Florida (USF) and National Oceanographic and Atmospheric Administration (NOAA) to acquire baseline pCO2, pH, total dissolved inorganic carbon (DIC), and total alkalinity (TA) on the west Florida shelf. These data are being used to model nearshore to offshore regional pCO2 and carbonate saturation state and, in conjunction with acquired habitat data, will be used to describe and interpret habitat change over time. Using the Multiparameter Inorganic Carbon Analyzer (MICA) developed by USF, data on air and sea pCO2, pH, DIC, and TA were collected underway during July and August 2008 cruises on the west Florida shelf. Maps depicting carbonate saturation state of the marine water, underlying sediment, and habitat data show varying relations. An additional cruise is planned for winter 2009.

  17. Analytical Modeling of a Novel Transverse Flux Machine for Direct Drive Wind Turbine Applications

    SciTech Connect

    Hasan, IIftekhar; Husain, Tausif; Uddin, Md Wasi; Sozer, Yilmaz; Husain, Iqbal; Muljadi, Eduard

    2015-09-02

    This paper presents a nonlinear analytical model of a novel double sided flux concentrating Transverse Flux Machine (TFM) based on the Magnetic Equivalent Circuit (MEC) model. The analytical model uses a series-parallel combination of flux tubes to predict the flux paths through different parts of the machine including air gaps, permanent magnets (PM), stator, and rotor. The two-dimensional MEC model approximates the complex three-dimensional flux paths of the TFM and includes the effects of magnetic saturation. The model is capable of adapting to any geometry which makes it a good alternative for evaluating prospective designs of TFM as compared to finite element solvers which are numerically intensive and require more computation time. A single phase, 1 kW, 400 rpm machine is analytically modeled and its resulting flux distribution, no-load EMF and torque, verified with Finite Element Analysis (FEA). The results are found to be in agreement with less than 5% error, while reducing the computation time by 25 times.

  18. Analytical Modeling of a Novel Transverse Flux Machine for Direct Drive Wind Turbine Applications: Preprint

    SciTech Connect

    Hasan, IIftekhar; Husain, Tausif; Uddin, Md Wasi; Sozer, Yilmaz; Husain; Iqbal; Muljadi, Eduard

    2015-08-24

    This paper presents a nonlinear analytical model of a novel double-sided flux concentrating Transverse Flux Machine (TFM) based on the Magnetic Equivalent Circuit (MEC) model. The analytical model uses a series-parallel combination of flux tubes to predict the flux paths through different parts of the machine including air gaps, permanent magnets, stator, and rotor. The two-dimensional MEC model approximates the complex three-dimensional flux paths of the TFM and includes the effects of magnetic saturation. The model is capable of adapting to any geometry that makes it a good alternative for evaluating prospective designs of TFM compared to finite element solvers that are numerically intensive and require more computation time. A single-phase, 1-kW, 400-rpm machine is analytically modeled, and its resulting flux distribution, no-load EMF, and torque are verified with finite element analysis. The results are found to be in agreement, with less than 5% error, while reducing the computation time by 25 times.

  19. Phytoplankton carbon fixation gene (RuBisCO) transcripts and air-sea CO2 flux in the Mississippi River plume

    SciTech Connect

    John, David E.; Wang, Zhaohui A.; Liu, Xuewu; Byrne, Robert H.; Corredor, Jorge E.; López, José M.; Cabrera, Alvaro; Bronk, Deborah A.; Tabita, F. Robert; Paul, John H.

    2007-08-30

    River plumes deliver large quantities of nutrients to oligotrophic oceans, often resulting in significant CO2 drawdown. To determine the relationship between expression of the major gene in carbon fixation (large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase, RuBisCO) and CO2 dynamics, we evaluated rbcL mRNA abundance using novel quantitative PCR assays, phytoplankton cell analyses, photophysiological parameters, and pCO2 in and around the Mississippi River plume (MRP) in the Gulf of Mexico. Lower salinity (30–32) stations were dominated by rbcL mRNA concentrations from heterokonts, such as diatoms and pelagophytes, which were at least an order of magnitude greater than haptophytes, alpha-Synechococcus or high-light Prochlorococcus. However, rbcL transcript abundances were similar among these groups at oligotrophic stations (salinity 34–36). Diatom cell counts and heterokont rbcL RNA showed a strong negative correlation to seawater pCO2. While Prochlorococcus cells did not exhibit a large difference between low and high pCO2 water, Prochlorococcus rbcL RNA concentrations had a strong positive correlation to pCO2, suggesting a very low level of RuBisCO RNA transcription among Prochlorococcus in the plume waters, possibly due to their relatively poor carbon concentrating mechanisms (CCMs). These results provide molecular evidence that diatom/pelagophyte productivity is largely responsible for the large CO2 drawdown occurring in the MRP, based on the co-occurrence of elevated RuBisCO gene transcript concentrations from this group and reduced seawater pCO2 levels. This may partly be due to efficient CCMs that enable heterokont eukaryotes such as diatoms to continue fixing CO2 in the face of strong CO2 drawdown. Finally, our work represents the first attempt to relate in situ microbial gene expression to contemporaneous CO2 flux

  20. Dual-rotor, radial-flux, toroidally-wound, permanent-magnet machine

    DOEpatents

    Qu, Ronghai; Lipo, Thomas A.

    2005-08-02

    The present invention provides a novel dual-rotor, radial-flux, toroidally-wound, permanent-magnet machine. The present invention improves electrical machine torque density and efficiency. At least one concentric surface-mounted permanent magnet dual-rotor is located inside and outside of a torus-shaped stator with back-to-back windings, respectively. The machine substantially improves machine efficiency by reducing the end windings and boosts the torque density by at least doubling the air gap and optimizing the machine aspect ratio.

  1. Errors in airborne flux measurements

    NASA Astrophysics Data System (ADS)

    Mann, Jakob; Lenschow, Donald H.

    1994-07-01

    We present a general approach for estimating systematic and random errors in eddy correlation fluxes and flux gradients measured by aircraft in the convective boundary layer as a function of the length of the flight leg, or of the cutoff wavelength of a highpass filter. The estimates are obtained from empirical expressions for various length scales in the convective boundary layer and they are experimentally verified using data from the First ISLSCP (International Satellite Land Surface Climatology Experiment) Field Experiment (FIFE), the Air Mass Transformation Experiment (AMTEX), and the Electra Radome Experiment (ELDOME). We show that the systematic flux and flux gradient errors can be important if fluxes are calculated from a set of several short flight legs or if the vertical velocity and scalar time series are high-pass filtered. While the systematic error of the flux is usually negative, that of the flux gradient can change sign. For example, for temperature flux divergence the systematic error changes from negative to positive about a quarter of the way up in the convective boundary layer.

  2. A study of the influence of forest gaps on fire-atmosphere interactions

    NASA Astrophysics Data System (ADS)

    Kiefer, Michael T.; Heilman, Warren E.; Zhong, Shiyuan; Charney, Joseph J.; Bian, Xindi

    2016-07-01

    Much uncertainty exists regarding the possible role that gaps in forest canopies play in modulating fire-atmosphere interactions in otherwise horizontally homogeneous forests. This study examines the influence of gaps in forest canopies on atmospheric perturbations induced by a low-intensity fire using the ARPS-CANOPY model, a version of the Advanced Regional Prediction System (ARPS) model with a canopy parameterization. A series of numerical experiments are conducted with a stationary low-intensity fire, represented in the model as a line of enhanced surface sensible heat flux. Experiments are conducted with and without forest gaps, and with gaps in different positions relative to the fire line. For each of the four cases considered, an additional simulation is performed without the fire to facilitate comparison of the fire-perturbed atmosphere and the background state. Analyses of both mean and instantaneous wind velocity, turbulent kinetic energy, air temperature, and turbulent mixing of heat are presented in order to examine the fire-perturbed atmosphere on multiple timescales. Results of the analyses indicate that the impact of the fire on the atmosphere is greatest in the case with the gap centered on the fire and weakest in the case with the gap upstream of the fire. It is shown that gaps in forest canopies have the potential to play a role in the vertical as well as horizontal transport of heat away from the fire. Results also suggest that, in order to understand how the fire will alter wind and turbulence in a heterogeneous forest, one needs to first understand how the forest heterogeneity itself influences the wind and turbulence fields without the fire.

  3. Gap filling strategies and error in estimating annual soil respiration

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil respiration (Rsoil) is one of the largest CO2 fluxes in the global carbon (C) cycle. Estimation of annual Rsoil requires extrapolation of survey measurements or gap-filling of automated records to produce a complete time series. While many gap-filling methodologies have been employed, there is ...

  4. Thermaikos Gulf Coastal System, NW Aegean Sea: an overview of water/sediment fluxes in relation to air land ocean interactions and human activities

    NASA Astrophysics Data System (ADS)

    Poulos, S. E.; Chronis, G. Th; Collins, M. B.; Lykousis, V.

    2000-04-01

    zone ecosystem. Thus, the construction of dams along the routes of the main rivers has reduced dramatically the water/sediment fluxes; this caused, for example, retreat of the deltaic coastlines and seawater intrusion into the groundwater aquifers. Similarly, pollution and/or eutrophication of the nearshore marine environment have resulted from the inputs of industrial wastes, urban untreated sewage, and agricultural activities on the coastal plains. This effect is demonstrated by high levels of pollutants, nutrients, and by the increased concentrations of non-residual trace-metals within the surficial sediments. Finally, climatic changes associated with a potential rise in sea level (i.e. 30-50 cm) will threaten a substantial part of the low-lying lands of Thermaikos Gulf. Thus, systematic and thorough monitoring is needed in order to protect the coastal ecosystem; this will ensure its sustainable development and successful management, in relation to present and future socio-economic activities and climatic changes.

  5. Behind the Pay Gap

    ERIC Educational Resources Information Center

    Dey, Judy Goldberg; Hill, Catherine

    2007-01-01

    Women have made remarkable gains in education during the past three decades, yet these achievements have resulted in only modest improvements in pay equity. The gender pay gap has become a fixture of the U.S. workplace and is so ubiquitous that many simply view it as normal. "Behind the Pay Gap" examines the gender pay gap for college graduates.…

  6. Practice Gaps in Pruritus.

    PubMed

    Silverberg, Jonathan I

    2016-07-01

    There are several practice gaps in the evaluation and management of itch. These gaps include a dearth of objective measures of itch, infrequent use of validated patient-reported outcomes for itch, non-evidence-based treatment, and lack of consensus about the ideal workup for generalized itch. The present article reviews these gaps and presents potential solutions. PMID:27363881

  7. A novel single-phase flux-switching permanent magnet linear generator used for free-piston Stirling engine

    NASA Astrophysics Data System (ADS)

    Zheng, Ping; Sui, Yi; Tong, Chengde; Bai, Jingang; Yu, Bin; Lin, Fei

    2014-05-01

    This paper investigates a novel single-phase flux-switching permanent-magnet (PM) linear machine used for free-piston Stirling engines. The machine topology and operating principle are studied. A flux-switching PM linear machine is designed based on the quasi-sinusoidal speed characteristic of the resonant piston. Considering the performance of back electromotive force and thrust capability, some leading structural parameters, including the air gap length, the PM thickness, the ratio of the outer radius of mover to that of stator, the mover tooth width, the stator tooth width, etc., are optimized by finite element analysis. Compared with conventional three-phase moving-magnet linear machine, the proposed single-phase flux-switching topology shows advantages in less PM use, lighter mover, and higher volume power density.

  8. Plasmon transmission through excitonic subwavelength gaps.

    PubMed

    Sukharev, Maxim; Nitzan, Abraham

    2016-04-14

    We study the transfer of electromagnetic energy across a subwavelength gap separating two co-axial metal nanorods. In the absence of spacer in the gap separating the rods, the system exhibits strong coupling behavior between longitudinal plasmons in the two rods. The nature and magnitude of this coupling are studied by varying various geometrical parameters. As a function of frequency, the transmission is dominated by a split longitudinal plasmon peak. The two hybrid modes are the dipole-like "bonding" mode characterized by a peak intensity in the gap and a quadrupole-like "antibonding" mode whose amplitude vanishes at the gap center. When the length of one rod is varied, this mode spectrum exhibits the familiar anti-crossing behavior that depends on the coupling strength determined by the gap width. When off-resonant 2-level emitters are placed in the gap, almost no effect on the frequency dependent transmission is observed. In contrast, when the molecular system is resonant with the plasmonic line shape, the transmission is strongly modified, showing characteristics of strong exciton-plasmon coupling. Most strongly modified is the transmission near the lower frequency "bonding" plasmon mode. The presence of resonant molecules in the gap affects not only the molecule-field interaction but also the spatial distribution of the field intensity and the electromagnetic energy flux across the junction. PMID:27083741

  9. Rho/RacGAPs

    PubMed Central

    Csépányi-Kömi, Roland; Lévay, Magdolna; Ligeti, Erzsébet

    2012-01-01

    Regulatory proteins such as guanine nucleotide exchange factors (GEFs) and GTPase activating proteins (GAPs) determine the activity of small GTPases. In the Rho/Rac family, the number of GEFs and GAPs largely exceeds the number of small GTPases, raising the question of specific or overlapping functions. In our recent study we investigated the first time ARHGAP25 at the protein level, determined its activity as RacGAP and showed its involvement in phagocytosis. With the discovery of ARHGAP25, the number of RacGAPs described in phagocytes is increased to six. We provide data that indicate the specific functions of selected Rho/RacGAPs and we show an example of differential regulation of a Rho/Rac family GAP by different kinases. We propose that the abundance of Rho/Rac family GAPs is an important element of the fine spatiotemporal regulation of diverse cellular functions. PMID:22751505

  10. Homopolar dc motor and trapped flux brushless dc motor using high temperature superconductor materials

    SciTech Connect

    Crapo, A.D.; Lloyd, J.D. )

    1991-03-01

    This paper reports on two motors designed and built for use with high temperature superconductor (HTSC) materials. They are a homopolar DC motor that will use HTSC field windings and a brushless DC motor that will use bulk HTSC material to trap flux in steel rotor poles. The HTSC field windings of the homopolar DC motor are designed to operate at 1000 Amperes/cm{sup 2} in a 0.010 Tesla (100 Gauss) field. In order to maximize torque in the homopolar DC motor, an iron magnetic circuit with small air gaps gives maximum flux for minimum Ampere turns in the field. A copper field winding version of the homopolar DC motor has been tested while the authors wait for 575 Ampere turn HTSC coils.

  11. A biogenic CO2 flux adjustment scheme for the mitigation of large-scale biases in global atmospheric CO2 analyses and forecasts

    NASA Astrophysics Data System (ADS)

    Agustí-Panareda, Anna; Massart, Sébastien; Chevallier, Frédéric; Balsamo, Gianpaolo; Boussetta, Souhail; Dutra, Emanuel; Beljaars, Anton

    2016-08-01

    Forecasting atmospheric CO2 daily at the global scale with a good accuracy like it is done for the weather is a challenging task. However, it is also one of the key areas of development to bridge the gaps between weather, air quality and climate models. The challenge stems from the fact that atmospheric CO2 is largely controlled by the CO2 fluxes at the surface, which are difficult to constrain with observations. In particular, the biogenic fluxes simulated by land surface models show skill in detecting synoptic and regional-scale disturbances up to sub-seasonal time-scales, but they are subject to large seasonal and annual budget errors at global scale, usually requiring a posteriori adjustment. This paper presents a scheme to diagnose and mitigate model errors associated with biogenic fluxes within an atmospheric CO2 forecasting system. The scheme is an adaptive scaling procedure referred to as a biogenic flux adjustment scheme (BFAS), and it can be applied automatically in real time throughout the forecast. The BFAS method generally improves the continental budget of CO2 fluxes in the model by combining information from three sources: (1) retrospective fluxes estimated by a global flux inversion system, (2) land-use information, (3) simulated fluxes from the model. The method is shown to produce enhanced skill in the daily CO2 10-day forecasts without requiring continuous manual intervention. Therefore, it is particularly suitable for near-real-time CO2 analysis and forecasting systems.

  12. Influence of Gap-Filling to Generate Continuous Datasets on Process Network Analysis

    NASA Astrophysics Data System (ADS)

    Yun, J.; Kim, J.; Kim, S.; Chun, J.

    2013-12-01

    The interplay of environmental conditions, energy, matter, and information defines the context and constraints for the set of processes and structures that may emerge during self-organization in complex ecosystems. Following Ruddell and Kumar (2009), we have evaluated statistical measures of characterizing the organization of the information flow in ecohydrological process networks in a deciduous forest ecosystem. We used the time series data obtained in 2008 (normal year) from the KoFlux forest tower site in central Korea. The 30-minute averages of eddy fluxes of energy, water and CO2 were measured at 40m above an oak-dominated old deciduous forest along with other micrometeorological variables. In this analysis, we selected 13 variables: atmospheric pressure (Pa), net ecosystem CO2 exchange (NEE), gross primary productivity (GPP), ecosystem respiration (RE), latent heat flux (LE), precipitation (Precip), solar radiation (Rg), air temperature (T), vapor pressure deficit (VPD), sensible heat flux (H), canopy temperature (Tc), wind direction (WD), and wind speed (WS). Our results support that a process network approach can be used to formally resolve feedback, time scales, and subsystems that define the complex ecosystem's organization by considering mutual information and transfer entropy simultaneously. We also observed that the turbulent and atmospheric boundary layer subsystems are coupled through feedback loops, and form a regional self-organizing subsystem in August when the forest is in healthy environment. In particular, we noted that the observed feedback loops in the process network disappeared when the time series data were artificially gap-filled for missing data, which is a common practice in post-data processing. In this presentation, we report the influence of gap-filling on the process network analysis by artificially assigning different sizes and periods of missing data and discuss the implication of our results on validation and calibration of

  13. High temporal resolution dynamics of wintertime soil CO2 flux

    NASA Astrophysics Data System (ADS)

    Risk, D. A.; McArthur, G. S.; Nickerson, N. R.; Beltrami, H.

    2009-12-01

    Few studies have undertaken soil CO2 flux measurements during winter, despite the fact that even in temperate zones, winter-like conditions may persist for one-third of the year or more. When growing season monitoring equipment is stowed for the winter, we potentially miss a large portion of the carbon budget, and may also fail to develop an adequate appreciation of winter c production dynamics. These are critical gaps, especially with respect to soil carbon stability and CO2 emissions in northern and permafrost areas, which are expected to accelerate as a consequence of climate change and which may create a positive feedback on atmospheric CO2 concentrations. This study undertakes a thorough examination of overwinter soil CO2 dynamics at two contrasting sites; one with deeply frozen soils where snow cover is absent as a result of sustained high winds; and another site with heavy snow load (>150 cm typical) where soils underneath remain frost-free because of snowpack insulation. Our overwinter soil-surface CO2 flux measurements were facilitated by use of a new instrumental technique called Continuous Timeseries - Forced Diffusion (CT-FD) to record soil CO2 fluxes continuously at a temporal resolution of 60 seconds. The high frequency monitoring allows us to look not only at magnitudes of change and carbon budgets, but also in detail at the temporal characteristics of response to environmental forcings. Here, we concentrate our analysis on rates of change near critical thresholds such as freeze-thaw. At the deep snowpack site where soil frost was absent, we observed pronounced diurnal cyclicity in CO2 flux even under a >150 cm snowpack, marked moisture response after midwinter rain events, and a springtime respiratory burst that began slightly before full snowpack melt. The CO2 emission dynamics from the frozen soils of the snow-free site were dominated by respiratory bursts at freeze-thaw thresholds when solar heating and warm air temperatures created a thin active

  14. Narrowing Participation Gaps

    ERIC Educational Resources Information Center

    Hand, Victoria; Kirtley, Karmen; Matassa, Michael

    2015-01-01

    Shrinking the achievement gap in mathematics is a tall order. One way to approach this challenge is to think about how the achievement gap manifests itself in the classroom and take concrete action. For example, opportunities to participate in activities that involve mathematical reasoning and argumentation in a safe and supportive manner are…

  15. The National "Expertise Gap"

    ERIC Educational Resources Information Center

    Hamilton, Kendra

    2005-01-01

    This article discusses the Woodrow Wilson National Fellowship Foundation's report, "Diversity and the Ph.D.," released in May, which documents in troubling detail the exact dimensions of what the foundation's president, Dr. Robert Weisbuch, is calling the national "expertise gap." Weisbuch states that the expertise gap extends beyond the…

  16. Confronting the Achievement Gap

    ERIC Educational Resources Information Center

    Gardner, David

    2007-01-01

    This article talks about the large achievement gap between children of color and their white peers. The reasons for the achievement gap are varied. First, many urban minorities come from a background of poverty. One of the detrimental effects of growing up in poverty is receiving inadequate nourishment at a time when bodies and brains are rapidly…

  17. California: Emigrant Gap

    Atmospheric Science Data Center

    2014-05-15

    article title:  Emigrant Gap Fire, California     View Larger ... The most prominent plume arises from the Emigrant Gap Fire, located about 40 kilometers west of Lake Tahoe. The animated panorama ... left is Mount Shasta. As of August 30, 2001, the US Forest Service reported the total year-to-date area burned in Northern ...

  18. Knowledge Gaps, Social Locators, and Media Schemata: Gaps, Reverse Gaps, and Gaps of Disaffection.

    ERIC Educational Resources Information Center

    Fredin, Eric S.; And Others

    1994-01-01

    Studies a public school controversy and finds a knowledge gap--a gap of disaffection. Finds that, among women only, higher education leads to greater knowledge but does so partly through reduced trust of government and lower perceived fairness of the news media. Shows similar findings with other less powerful groups. (SR)

  19. The Parenting Gap

    ERIC Educational Resources Information Center

    Reeves, Richard V.; Howard, Kimberly

    2013-01-01

    The parenting gap is a big factor in the opportunity gap. The chances of upward social mobility are lower for children with parents struggling to do a good job--in terms of creating a supportive and stimulating home environment. Children lucky enough to have strong parents are more likely to succeed at all the critical life stages, which means…

  20. Measurement of particulate matter emission fluxes from a beef cattle feedlot using Flux-gradient technique

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Data on air emissions from open-lot beef cattle feedlots are limited. This research was conducted to determine PM10 emission fluxes from a commercial beef cattle feedlot in Kansas using the flux-gradient technique, a widely-used micrometeorological method for gaseous emissions from open sources. V...

  1. Standardization of flux chamber and wind tunnel flux measurements for quantifying emissions from area sources at animal feeding operations

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A variety of wind tunnels and flux chambers have been used to measure fluxes of volatile organic compounds (VOC) and ammonia (NH3) at animal feeding operations (AFO). However, there has been little regard to the extreme variation and inaccuracy caused by inappropriate air velocity or sweep air flow...

  2. Method for limiting heat flux in double-wall tubes

    DOEpatents

    Hwang, Jaw-Yeu

    1982-01-01

    A method of limiting the heat flux in a portion of double-wall tubes including heat treating the tubes so that the walls separate when subjected to high heat flux and supplying an inert gas mixture to the gap at the interface of the double-wall tubes.

  3. Magnetic bearing. [for supplying magnetic fluxes

    NASA Technical Reports Server (NTRS)

    Studer, P. A. (Inventor)

    1975-01-01

    A magnetic bearing is described which includes a pair of coaxial, toroidal, and permanent magnets having axially directed poles. Like poles of the permanent magnets are adjacent to each other, whereby the permanent magnets have a tendency to be urged apart along the common axis. An electromagnet is wound coaxially with the permanent magnets in such a manner that the poles are axially directed. Between the poles of each permanent magnet there is a low magnetic reluctance circuit including two series air gaps. Between the poles of the electromagnet a low reluctance path including only one air gap of each of the low magnetic reluctance circuits is provided. The low reluctance path for the electromagnet includes a ring axially translatable relative to the permanent magnets. The ring forms opposite faces of the air gaps in the magnetic circuits for each permanent magnet.

  4. Eddy covariance measurements in screenhouses: turbulence characteristics and flux gradients

    NASA Astrophysics Data System (ADS)

    Dicken, U.; Cohen, S.; Tanny, J.

    2012-04-01

    Shading banana and other orchard crops with screens is popular in arid and semi-arid regions for decreasing water use and increasing fruit quality. However, crop water use within this unique environment is much less studied than for canopies in the open. Previous studies of our research group have established the use of the Eddy Covariance (EC) technique for reliable evapotranspiration and sensible heat flux measurements within screenhouses. These studies focused on operating conditions of the system. The present paper is a comprehensive study which examined the performance of the EC system in different types of screenhouses (shading and insect-proof), different crops (banana and pepper) at different development stages (small and large plants) and different climatic regions in Israel. The main goal was to establish guidelines for optimal application of the EC technique in screenhouses. The research consisted of 6 field campaigns: in 3 campaigns two EC systems were simultaneously deployed either vertically or horizontally, and in 3 other campaigns a single EC system was deployed at one measurement height. EC systems were deployed at different normalized system heights, Zs, which define the relative measurement heights within the air gap between the canopy top and the horizontal screened roof. System performance was examined using quality tests like energy balance closure, flux variance similarity, friction velocity, footprint modeling, energy spectrum, turbulence intensity and vertical and horizontal flux gradient analyses. Resulting energy balance closure slopes averaged 0.81±0.08 and 0.91±0.08 for the smaller and larger plants, respectively. Turbulent flows were found to be marginally developed within the air gap between the top of the plants and the horizontal screened roof. Turbulence intensity, flux variance similarity test, energy spectrum decay rate and friction velocity were essentially independent of the measurement height and were within the common range

  5. Fast flux locked loop

    DOEpatents

    Ganther, Jr., Kenneth R.; Snapp, Lowell D.

    2002-09-10

    A flux locked loop for providing an electrical feedback signal, the flux locked loop employing radio-frequency components and technology to extend the flux modulation frequency and tracking loop bandwidth. The flux locked loop of the present invention has particularly useful application in read-out electronics for DC SQUID magnetic measurement systems, in which case the electrical signal output by the flux locked loop represents an unknown magnetic flux applied to the DC SQUID.

  6. Anion gap acidosis.

    PubMed

    Ishihara, K; Szerlip, H M

    1998-01-01

    Although an anion gap at less than 20 mEq/L rarely has a defined etiology, significant elevations in the anion gap almost always signify presence of an acidosis that can be easily identified. Anion gap acidoses can be divided into those caused by lactate accumulation, ketoacid production, toxin/drugs, and uremia. Lactic acidoses caused by decreased oxygen delivery or defective oxygen utilization are associated with high mortality. The treatment of lactic acidosis is controversial. The use of bicarbonate to increase pH is rarely successful and, by generating PCO2, may worsen outcome. Ketoacidosis is usually secondary to diabetes or alcohol. Treatment is aimed at turning off ketogenesis and repairing fluid and electrolyte abnormalities. Methanol, ethylene glycol, and salicylates are responsible for the majority of toxin-induced anion gap acidoses. Both methanol and ethylene glycol are associated with severe acidoses and elevated osmolar gaps. Treatment of both is alcohol infusion to decrease formation of toxic metabolites and dialyses to remove toxins. Salicylate toxicity usually is associated with a mild metabolic acidosis and a respiratory alkalosis. Uremia is associated with a mild acidosis secondary to decreased ammonia secretion and an anion gap caused by the retention of unmeasured anions. A decrease in anion gap is caused by numerous mechanisms and thus has little clinical utility.

  7. Mercury vapor air-surface exchange measured by collocated micrometeorological and enclosure methods - Part I: Data comparability and method characteristics

    NASA Astrophysics Data System (ADS)

    Zhu, W.; Sommar, J.; Lin, C.-J.; Feng, X.

    2015-01-01

    Reliable quantification of air-biosphere exchange flux of elemental mercury vapor (Hg0) is crucial for understanding the global biogeochemical cycle of mercury. However, there has not been a standard analytical protocol for flux quantification, and little attention has been devoted to characterize the temporal variability and comparability of fluxes measured by different methods. In this study, we deployed a collocated set of micrometeorological (MM) and dynamic flux chamber (DFC) measurement systems to quantify Hg0 flux over bare soil and low standing crop in an agricultural field. The techniques include relaxed eddy accumulation (REA), modified Bowen ratio (MBR), aerodynamic gradient (AGM) as well as dynamic flux chambers of traditional (TDFC) and novel (NDFC) designs. The five systems and their measured fluxes were cross-examined with respect to magnitude, temporal trend and correlation with environmental variables. Fluxes measured by the MM and DFC methods showed distinct temporal trends. The former exhibited a highly dynamic temporal variability while the latter had much more gradual temporal features. The diurnal characteristics reflected the difference in the fundamental processes driving the measurements. The correlations between NDFC and TDFC fluxes and between MBR and AGM fluxes were significant (R>0.8, p<0.05), but the correlation between DFC and MM fluxes were from weak to moderate (R=0.1-0.5). Statistical analysis indicated that the median of turbulent fluxes estimated by the three independent MM techniques were not significantly different. Cumulative flux measured by TDFC is considerably lower (42% of AGM and 31% of MBR fluxes) while those measured by NDFC, AGM and MBR were similar (<10% difference). This suggests that incorporating an atmospheric turbulence property such as friction velocity for correcting the DFC-measured flux effectively bridged the gap between the Hg0 fluxes measured by enclosure and MM techniques. Cumulated flux measured by REA

  8. SPARK GAP SWITCH

    DOEpatents

    Neal, R.B.

    1957-12-17

    An improved triggered spark gap switch is described, capable of precisely controllable firing time while switching very large amounts of power. The invention in general comprises three electrodes adjustably spaced and adapted to have a large potential impressed between the outer electrodes. The central electrode includes two separate elements electrically connected togetaer and spaced apart to define a pair of spark gaps between the end electrodes. Means are provided to cause the gas flow in the switch to pass towards the central electrode, through a passage in each separate element, and out an exit disposed between the two separate central electrode elements in order to withdraw ions from the spark gap.

  9. Gaps in Oncology

    Cancer.gov

    The first plenary of the EPEC-O (Education in Palliative and End-of-Life Care for Oncology) Self-Study Original Version provides background for the curriculum and identifies gaps in current and desired comprehensive cancer care.

  10. Fiber optic gap gauge

    DOEpatents

    Wood, Billy E.; Groves, Scott E.; Larsen, Greg J.; Sanchez, Roberto J.

    2006-11-14

    A lightweight, small size, high sensitivity gauge for indirectly measuring displacement or absolute gap width by measuring axial strain in an orthogonal direction to the displacement/gap width. The gap gauge includes a preferably titanium base having a central tension bar with springs connecting opposite ends of the tension bar to a pair of end connector bars, and an elongated bow spring connected to the end connector bars with a middle section bowed away from the base to define a gap. The bow spring is capable of producing an axial strain in the base proportional to a displacement of the middle section in a direction orthogonal to the base. And a strain sensor, such as a Fabry-Perot interferometer strain sensor, is connected to measure the axial strain in the base, so that the displacement of the middle section may be indirectly determined from the measurement of the axial strain in the base.

  11. Photonic band gap materials

    SciTech Connect

    Soukoulis, C.M. |

    1993-12-31

    An overview of the theoretical and experimental efforts in obtaining a photonic band gap, a frequency band in three-dimensional dielectric structures in which electromagnetic waves are forbidden, is presented.

  12. Computation of radiative heat transport across a nanoscale vacuum gap

    SciTech Connect

    Budaev, Bair V. Bogy, David B.

    2014-02-10

    Radiation heat transport across a vacuum gap between two half-spaces is studied. By consistently applying only the fundamental laws of physics, we obtain an algebraic equation that connects the temperatures of the half-spaces and the heat flux between them. The heat transport coefficient generated by this equation for such structures matches available experimental data for nanoscale and larger gaps without appealing to any additional specific mechanisms of energy transfer.

  13. Robotic Tube-Gap Inspector

    NASA Technical Reports Server (NTRS)

    Gilbert, Jeffrey L.; Gutow, David A.; Maslakowski, John E.

    1993-01-01

    Robotic vision system measures small gaps between nearly parallel tubes. Robot-held video camera examines closely spaced tubes while computer determines gaps between tubes. Video monitor simultaneously displays data on gaps.

  14. Magnetic-flux pump

    NASA Technical Reports Server (NTRS)

    Hildebrandt, A. F.; Elleman, D. D.; Whitmore, F. C. (Inventor)

    1966-01-01

    A magnetic flux pump is described for increasing the intensity of a magnetic field by transferring flux from one location to the magnetic field. The device includes a pair of communicating cavities formed in a block of superconducting material, and a piston for displacing the trapped magnetic flux into the secondary cavity producing a field having an intense flux density.

  15. High Flux Propagation Through The Atmosphere

    NASA Astrophysics Data System (ADS)

    Reilly, James P.

    1983-07-01

    Discussions are presented on laser-induced plasma generation in free air propagation (no target surface present). Plasmas can be generated with very high flux levels (for clean air) or with much lower flux levels (for dust-laden air). Pure water aerosols have not proven to substantially reduce air breakdown thresholds below those for clean air. Clean air breakdown at laser wavelengths has been predicted successfully for many years using theories developed for microwave wavelengths. By directly extending those theories to laser wavelengths, the dependencies on ambient pressure, spot size, wavelength and intensities have been predicted with favorable comparison to experimental data. Pure water aerosols (fogs, rain, clouds) have been investigated as to the phenomenology to be expected when irradiated by pulsed and CW laser devices at CO2 and DF laser wave-lengths. These aerosols are shown to heat, vaporize and/or shatter at various incident flux and fluence levels. The data base appears to substantiate this phenomology, but no substantive reduction of clean air breakdown thresholds has been observed when water aerosols are present. Dry solid single-material aerosols (e.g., Si02 dust) have been examined, both analytically and experimentally, for verification of phenomenology at various flux and fluence levels. Air breakdown induced by the onset of substantial vaporization rates of the irradiated particulate has been shown to be coincident with the onset of dirty air break-down. Real-world and man-made aerosol clouds have not been studied extensively, if at all, to the author's knowledge. Of particular importance are the effects on high energy laser beams of dust, vehicle exhaust, smoke, road dust and maritime aerosols (e.g., sea spray, sea fogs, etc.). For these important components of the HEL propagation story, no substantial HEL propagation data base exists.

  16. Extending quantum coherence of superconducting flux

    NASA Astrophysics Data System (ADS)

    Yan, Fei; Kamal, Archana; Orlando, Terry; Gustavsson, Simon; Oliver, William; Engineering Quantum Systems, MIT Team

    We present the design of a superconducting qubit with multiple Josephson junctions. The design starts with a capacitively shunted flux qubit, and it incorporates particular junction parameter choices for the purpose of simultaneously optimizing over transition frequency, anharmonicity, flux- and charge-noise sensitivity around flux degeneracy. By studying the scaling properties with design parameters, we identify directions to extend coherence substantially. This research was funded by the Office of the Director of National Intelligence (ODNI), Intelligence Advanced Research Projects Activity (IARPA) via MIT Lincoln Laboratory under Air Force Contract No. FA8721-05-C-0002.

  17. 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.

  18. Gap Cycling for SWIFT

    PubMed Central

    Corum, Curtis A.; Idiyatullin, Djaudat; Snyder, Carl J.; Garwood, Michael

    2014-01-01

    Purpose SWIFT (SWeep Imaging with Fourier Transformation) is a non-Cartesian MRI method with unique features and capabilities. In SWIFT, radiofrequency (RF) excitation and reception are performed nearly simultaneously, by rapidly switching between transmit and receive during a frequency-swept RF pulse. Because both the transmitted pulse and data acquisition are simultaneously amplitude-modulated in SWIFT (in contrast to continuous RF excitation and uninterrupted data acquisition in more familiar MRI sequences), crosstalk between different frequency bands occurs in the data. This crosstalk leads to a “bulls-eye” artifact in SWIFT images. We present a method to cancel this inter-band crosstalk by cycling the pulse and receive gap positions relative to the un-gapped pulse shape. We call this strategy “gap cycling.” Methods We carry out theoretical analysis, simulation and experiments to characterize the signal chain, resulting artifacts, and their elimination for SWIFT. Results Theoretical analysis reveals the mechanism for gap-cycling’s effectiveness in canceling inter-band crosstalk in the received data. We show phantom and in-vivo results demonstrating bulls-eye artifact free images. Conclusion Gap cycling is an effective method to remove bulls-eye artifact resulting from inter-band crosstalk in SWIFT data. PMID:24604286

  19. MULTIPLE SPARK GAP SWITCH

    DOEpatents

    Schofield, A.E.

    1958-07-22

    A multiple spark gap switch of unique construction is described which will permit controlled, simultaneous discharge of several capacitors into a load. The switch construction includes a disc electrode with a plurality of protuberances of generally convex shape on one surface. A firing electrode is insulatingly supponted In each of the electrode protuberances and extends substantially to the apex thereof. Individual electrodes are disposed on an insulating plate parallel with the disc electrode to form a number of spark gaps with the protuberances. These electrodes are each connected to a separate charged capacitor and when a voltage ls applied simultaneously between the trigger electrodes and the dlsc electrode, each spark gap fires to connect its capacitor to the disc electrode and a subsequent load.

  20. Precision gap particle separator

    DOEpatents

    Benett, William J.; Miles, Robin; Jones, II., Leslie M.; Stockton, Cheryl

    2004-06-08

    A system for separating particles entrained in a fluid includes a base with a first channel and a second channel. A precision gap connects the first channel and the second channel. The precision gap is of a size that allows small particles to pass from the first channel into the second channel and prevents large particles from the first channel into the second channel. A cover is positioned over the base unit, the first channel, the precision gap, and the second channel. An port directs the fluid containing the entrained particles into the first channel. An output port directs the large particles out of the first channel. A port connected to the second channel directs the small particles out of the second channel.

  1. Bridging NCL research gaps.

    PubMed

    Stehr, Frank; van der Putten, Herman

    2015-10-01

    The neuronal ceroid lipofuscinoses, collectively called NCLs, are rare and fatal lysosomal storage diseases that mainly affect children. Due to the fact that NCLs are both rare and heterogeneous (mutations in thirteen different genes) significant gaps exist in both preclinical and clinical research. Altogether, these gaps are major hurdles to bring therapies to patients while the need for new therapies is urgent to help them and their families. To define gaps and discuss solutions, a round table discussion involving teams and different stake holders took place during the 14th International Conference on Neuronal Ceroid Lipofuscinoses (Batten Disease) in Cordóba, Argentina. Topics covered by the teams and their leaders (in parentheses) included basic and translational research gaps with regard to large animal models (I. Tammen, D.N. Palmer), human NCL pathology and access to human tissue (J.D. Cooper, H.H. Goebel), rare NCLs (S. Hofman, I. Noher), links of NCLs to other diseases (F.M. Platt), gaps between clinic and clinical trials (H. Adams, A. Schulz), international collaborative efforts working towards a cure (S.E. Mole, H. Band) perspectives on palliative care from patient organizations (M. Frazier, A. West), and issues NCL researchers face when progressing to independent career in academia (M. Bond). Thoughts presented by the team leaders include previously unpublished opinions and information on the lack of understanding of disease pathomechanisms, gene function, assays for drug discovery and target validation, natural history of disease, and biomarkers for monitoring disease progression and treatment effects. This article is not intended to review the NCL literature. It includes personal opinions of the authors and it provides the reader with a summary of gaps discussed and solutions proposed by the teams. This article is part of a Special Issue entitled: Current Research on the Neuronal Ceroid Lipofuscinoses (Batten Disease). PMID:26056946

  2. Flux-p: automating metabolic flux analysis.

    PubMed

    Ebert, Birgitta E; Lamprecht, Anna-Lena; Steffen, Bernhard; Blank, Lars M

    2012-11-12

    Quantitative knowledge of intracellular fluxes in metabolic networks is invaluable for inferring metabolic system behavior and the design principles of biological systems. However, intracellular reaction rates can not often be calculated directly but have to be estimated; for instance, via 13C-based metabolic flux analysis, a model-based interpretation of stable carbon isotope patterns in intermediates of metabolism. Existing software such as FiatFlux, OpenFLUX or 13CFLUX supports experts in this complex analysis, but requires several steps that have to be carried out manually, hence restricting the use of this software for data interpretation to a rather small number of experiments. In this paper, we present Flux-P as an approach to automate and standardize 13C-based metabolic flux analysis, using the Bio-jETI workflow framework. Exemplarily based on the FiatFlux software, it demonstrates how services can be created that carry out the different analysis steps autonomously and how these can subsequently be assembled into software workflows that perform automated, high-throughput intracellular flux analysis of high quality and reproducibility. Besides significant acceleration and standardization of the data analysis, the agile workflow-based realization supports flexible changes of the analysis workflows on the user level, making it easy to perform custom analyses.

  3. Mind the Gap

    NASA Astrophysics Data System (ADS)

    Litim, Daniel F.

    We discuss an optimisation criterion for the exact renormalisation group based on the inverse effective propagator, which displays a gap. We show that a simple extremisation of the gap stabilises the flow, leading to better convergence of approximate solutions towards the physical theory. This improves the reliability of truncations, most relevant for any high precision computation. These ideas are closely linked to the removal of a spurious scheme dependence and a minimum sensitivity condition. The issue of predictive power and a link to the Polchinski RG are discussed as well. We illustrate our findings by computing critical exponents for the Ising universality class.

  4. Spark gap electrode erosion

    NASA Astrophysics Data System (ADS)

    Krompholz, H.; Kristiansen, M.

    1984-12-01

    The results of a one-year contract on electrode erosion phenomena are summarized. The arc voltage drop in a spark gap was measured for various electrode, gas, and pressure combinations. A previously developed model of self breakdown voltage distribution was extended. A jet model for electrode erosion was proposed and an experimental arrangement for testing the model was constructed. The effects of inhomogeneities and impurities in the electrodes were investigated. Some of the work described here is scheduled for completion in 1985 under a current grant (AFOSR 84-0032). The areas of investigation described here include: (1) Self breakdown voltage distributions; (2) Electrode erosion; (3) Spark gap voltage recovery.

  5. Health risk assessment of migrant workers' exposure to polychlorinated biphenyls in air and dust in an e-waste recycling area in China: Indication for a new wealth gap in environmental rights.

    PubMed

    Wang, Yalin; Hu, Jinxing; Lin, Wei; Wang, Ning; Li, Cheng; Luo, Peng; Hashmi, Muhammad Zaffar; Wang, Wenbo; Su, Xiaomei; Chen, Chen; Liu, Yindong; Huang, Ronglang; Shen, Chaofeng

    2016-02-01

    Migrant workers who work and live in polluted environment are a special vulnerable group in the accelerating pace of urbanization and industrialization in China. In the electronic waste (e-waste) recycling area, for example, migrant workers' exposure to pollutants, such as PCBs (polychlorinated biphenyls), is the result of an informal e-waste recycling process. A village in an electronic waste recycling area where migrant workers gather was surveyed. The migrant workers' daily routines were simulated according to the three-space transition: work place-on the road-home. Indoor air and dust in the migrant workers' houses and workplaces and the ambient air on the roads were sampled. The PCB levels of the air and dust in the places corresponding to the migrant workers are higher than those for local residents. The migrant workers have health risks from PCBs that are 3.8 times greater than those of local residents. This is not only caused by the exposure at work but also by their activity patterns and the environmental conditions of their dwellings. These results revealed the reason for the health risk difference between the migrant workers and local residents, and it also indicated that lifestyle and economic status are important factors that are often ignored compared to occupational exposure. PMID:26641519

  6. Health risk assessment of migrant workers' exposure to polychlorinated biphenyls in air and dust in an e-waste recycling area in China: Indication for a new wealth gap in environmental rights.

    PubMed

    Wang, Yalin; Hu, Jinxing; Lin, Wei; Wang, Ning; Li, Cheng; Luo, Peng; Hashmi, Muhammad Zaffar; Wang, Wenbo; Su, Xiaomei; Chen, Chen; Liu, Yindong; Huang, Ronglang; Shen, Chaofeng

    2016-02-01

    Migrant workers who work and live in polluted environment are a special vulnerable group in the accelerating pace of urbanization and industrialization in China. In the electronic waste (e-waste) recycling area, for example, migrant workers' exposure to pollutants, such as PCBs (polychlorinated biphenyls), is the result of an informal e-waste recycling process. A village in an electronic waste recycling area where migrant workers gather was surveyed. The migrant workers' daily routines were simulated according to the three-space transition: work place-on the road-home. Indoor air and dust in the migrant workers' houses and workplaces and the ambient air on the roads were sampled. The PCB levels of the air and dust in the places corresponding to the migrant workers are higher than those for local residents. The migrant workers have health risks from PCBs that are 3.8 times greater than those of local residents. This is not only caused by the exposure at work but also by their activity patterns and the environmental conditions of their dwellings. These results revealed the reason for the health risk difference between the migrant workers and local residents, and it also indicated that lifestyle and economic status are important factors that are often ignored compared to occupational exposure.

  7. Isotopic Compositions of Evaporative Fluxes

    NASA Astrophysics Data System (ADS)

    Feng, X.; Lauder, A. M.; Kopec, B. G.; Dade, W. B.; Virginia, R. A.; Posmentier, E. S.

    2013-12-01

    The isotopic fluxes of evaporation from a water surface are typically computed using a one-dimensional model, originally conceptualized by Craig and Gordon (1965) and further developed and adapted to different natural settings (such as transpiration, open surface evaporation, etc.) by various investigators. These models have two distinguishing characteristics. First, there exists a laminar layer where molecular diffusion away from the water-air interface causes kinetic isotopic fractionation. The magnitude of this fractionation is controlled by the diffusion/transport coefficient of each vapor isotopologue in air and their concentration gradients, the latter being controlled by relative humidity, isotopic ratios of ambient air, and turbulent conditions (such as wind and surface roughness). Second, the horizontal variations are ignored. In particular, the effect of horizontal advection on isotopic variations in the ambient air is not considered. The research reported here addresses the effects of relinquishing the simplifying assumptions in both of these areas. We developed a model, in which the simplification of a purely laminar layer is dropped. Instead, we express the vertical transport coefficient as the sum of the molecular diffusivity, that differs for each water isotopologue, and the turbulent diffusivity that increases linearly with height but does not vary among water isotopologues. With this model, the kinetic isotopic effect reduces with height in the vicinity of the water surface, and the net isotopic fractionation through the boundary layer can be integrated. The advantage of this conceptualization is that the magnitude of kinetic isotopic fractionation can be assessed directly with changing environmental conditions, such as humidity and wind speed, rather than approximated by discontinuous empirical functions of the environmental conditions, as in the conventional models mentioned above. To address the effect of lateral heterogeneity, we expanded the

  8. The Academic Generation Gap

    ERIC Educational Resources Information Center

    Dronzek, Anna

    2008-01-01

    The current generation gap in academia is different--fundamentally shaped by the structural problems of academic employment. The job market has especially exacerbated tensions between senior and junior faculty by ratcheting up expectations and requirements at every stage of the academic career. The disparities have been mentioned often enough to…

  9. Graphene: Mind the gap

    NASA Astrophysics Data System (ADS)

    Novoselov, Kostya

    2007-10-01

    Research now shows that interaction with silicon carbide substrate leads to the opening of a semiconductor gap in epitaxial graphene. This is an important first step towards bandgap engineering in this two-dimensional crystal, and its incorporation in electronic devices.

  10. Estimating Gender Wage Gaps

    ERIC Educational Resources Information Center

    McDonald, Judith A.; Thornton, Robert J.

    2011-01-01

    Course research projects that use easy-to-access real-world data and that generate findings with which undergraduate students can readily identify are hard to find. The authors describe a project that requires students to estimate the current female-male earnings gap for new college graduates. The project also enables students to see to what…

  11. Crossing the Gap

    ERIC Educational Resources Information Center

    Lockette, Tim

    2009-01-01

    In a nation where education is funded largely by local property taxes, schools in wealthy communities have plenty of funds to spend on programs that get their kids ready for college. Schools in poor communities scrimp and save to get the job done--or hope that funding from the state will help fill in the gap. This article describes how students…

  12. Closing the Performance Gap.

    ERIC Educational Resources Information Center

    Riggins, Cheryl G.

    2002-01-01

    Describes how the principal of a K-2, 400-student suburban elementary school near Flint, Michigan, worked with her staff and superintendent to develop and implement a strategic plan to close the student achievement gap. Reports significant improvement in reading and math scores after 1 year. (PKP)

  13. STEMMING the Gap

    ERIC Educational Resources Information Center

    Kahler, Jim; Valentine, Nancy

    2011-01-01

    America has a gap when it comes to youth pursuing science and technology careers. In an effort to improve the knowledge and application of science, technology, engineering, and math (STEM), after-school programs can work in conjunction with formal in-school curriculum to improve science education. One organization that actively addresses this…

  14. Gaining on the Gap

    ERIC Educational Resources Information Center

    Smith, Robert G.

    2010-01-01

    About three-quarters of the 2009 graduates of the highly diverse Arlington, Virginia, Public Schools completed one or more Advanced Placement or International Baccalaureate courses during their high school careers. That figure serves as one indicator of a decade-long initiative to eliminate achievement gaps while raising achievement for all…

  15. Multiple gap photovoltaic device

    DOEpatents

    Dalal, Vikram L.

    1981-01-01

    A multiple gap photovoltaic device having a transparent electrical contact adjacent a first cell which in turn is adjacent a second cell on an opaque electrical contact, includes utilizing an amorphous semiconductor as the first cell and a crystalline semiconductor as the second cell.

  16. Vortex and gap generation in gauge models of graphene

    SciTech Connect

    Oliveira, O.; Cordeiro, C.E.; Delfino, A.; Paula, W. de; Frederico, T.

    2011-04-15

    Effective quantum field theoretical continuum models for graphene are investigated. The models include a complex scalar field and a vector gauge field. Different gauge theories are considered and their gap patterns for the scalar, vector, and fermion excitations are investigated. Different gauge groups lead to different relations between the gaps, which can be used to experimentally distinguish the gauge theories. In this class of models the fermionic gap is a dynamic quantity. The finite-energy vortex solutions of the gauge models have the flux of the ''magnetic field'' quantized, making the Bohm-Aharonov effect active even when external electromagnetic fields are absent. The flux comes proportional to the scalar field angular momentum quantum number. The zero modes of the Dirac equation show that the gauge models considered here are compatible with fractionalization.

  17. Dual Active Surface Heat Flux Gage Probe

    NASA Technical Reports Server (NTRS)

    Liebert, Curt H.; Kolodziej, Paul

    1995-01-01

    A unique plug-type heat flux gage probe was tested in the NASA Ames Research Center 2x9 turbulent flow duct facility. The probe was fabricated by welding a miniature dual active surface heat flux gage body to the end of a hollow metal cylindrical bolt containing a metal inner tube. Cooling air flows through the inner tube, impinges onto the back of the gage body and then flows out through the annulus formed between the inner tube and the hollow bolt wall. Heat flux was generated in the duct facility with a Huels arc heater. The duct had a rectangular cross section and one wall was fabricated from 2.54 centimeter thick thermal insulation rigid surface material mounted onto an aluminum plate. To measure heat flux, the probe was inserted through the plate and insulating materials with the from of the gage located flush with the hot gas-side insulation surface. Absorbed heat fluxes measured with the probe were compared with absorbed heat fluxes measured with six water-cooled reference calorimeters. These calorimeters were located in a water-cooled metal duct wall which was located across from the probe position. Correspondence of transient and steady heat fluxes measured with the reference calorimeters and heat flux gage probe was generally within a satisfactory plus or minus 10 percent. This good correspondence was achieved even though the much cooler probe caused a large surface temperature disruption of 1000K between the metal gage and the insulation. However, this temperature disruption did not seriously effect the accuracy of the heat flux measurement. A current application for dual active surface heat flux gages is for transient and steady absorbed heat flux, surface temperature and heat transfer coefficient measurements on the surface of an oxidizer turbine inlet deflector operating in a space shuttle test bed engine.

  18. Investigation of mechanical field weakening of axial flux permanent magnet motor

    NASA Astrophysics Data System (ADS)

    Syaifuddin Mohd, M.; Aziz, A. Rashid A.; Syafiq Mohd, M.

    2015-12-01

    An investigation of axial flux permanent magnet motor (AFPM) characteristics was conducted with a proposed mechanical field weakening control mechanisms (by means of stator-rotor force manipulation) on the motor through modeling and experimentation. By varying the air gap between at least two bistable positions, the peak torque and top speed of the motor can be extended. The motor high efficiency region can also be extended to cover greater part of the motor operating points. An analytical model of the motor had been developed to study the correlation between the total attraction force (between the rotor and the stator) and the operating parameters of the motor. The test results shows that the motor output complies with the prediction of the research hypothesis and it is likely that a spring locking mechanism can be built to dynamically adjust the air gap of the motor to increase the operating range and could be applied in electric drivetrain applications to improve overall efficiency of electric and hybrid electric vehicles.

  19. Deterministic multidimensional nonuniform gap sampling.

    PubMed

    Worley, Bradley; Powers, Robert

    2015-12-01

    Born from empirical observations in nonuniformly sampled multidimensional NMR data relating to gaps between sampled points, the Poisson-gap sampling method has enjoyed widespread use in biomolecular NMR. While the majority of nonuniform sampling schemes are fully randomly drawn from probability densities that vary over a Nyquist grid, the Poisson-gap scheme employs constrained random deviates to minimize the gaps between sampled grid points. We describe a deterministic gap sampling method, based on the average behavior of Poisson-gap sampling, which performs comparably to its random counterpart with the additional benefit of completely deterministic behavior. We also introduce a general algorithm for multidimensional nonuniform sampling based on a gap equation, and apply it to yield a deterministic sampling scheme that combines burst-mode sampling features with those of Poisson-gap schemes. Finally, we derive a relationship between stochastic gap equations and the expectation value of their sampling probability densities.

  20. Deterministic multidimensional nonuniform gap sampling

    NASA Astrophysics Data System (ADS)

    Worley, Bradley; Powers, Robert

    2015-12-01

    Born from empirical observations in nonuniformly sampled multidimensional NMR data relating to gaps between sampled points, the Poisson-gap sampling method has enjoyed widespread use in biomolecular NMR. While the majority of nonuniform sampling schemes are fully randomly drawn from probability densities that vary over a Nyquist grid, the Poisson-gap scheme employs constrained random deviates to minimize the gaps between sampled grid points. We describe a deterministic gap sampling method, based on the average behavior of Poisson-gap sampling, which performs comparably to its random counterpart with the additional benefit of completely deterministic behavior. We also introduce a general algorithm for multidimensional nonuniform sampling based on a gap equation, and apply it to yield a deterministic sampling scheme that combines burst-mode sampling features with those of Poisson-gap schemes. Finally, we derive a relationship between stochastic gap equations and the expectation value of their sampling probability densities.

  1. Heat and moisture transfer in gaps between sweating imitation skin and nonwoven cloth: effect of gap space and alignment of skin and clothing on the moisture transfer

    NASA Astrophysics Data System (ADS)

    Morozumi, Yoshio; Akaki, Kenichi; Tanabe, Naomasa

    2012-07-01

    This study investigates heat and moisture transfer between a sweating film and a nonwoven sheet both experimentally and numerically. A mathematical model based on heat conduction and moisture diffusion in both the air gap and cloth is presented. The evaporation rate and surface temperature of the sweating film are well predicted under various conditions such as air gap height, heating conditions, and sweating film orientation by evaluating the effective thermal conductivity and diffusion coefficient from the empirical equations of the Nusselt number for a fluid layer, even though the air gap height is sufficiently large to cause natural convections.

  2. Minding the Gap

    SciTech Connect

    Firestone, Millicent Anne

    2015-02-23

    Neutron & X-ray scattering provides nano- to meso-scale details of complex fluid structure; 1D electronic density maps dervied from SAXS yield molecular level insights; Neutron reflectivity provides substructure details of substrate supported complex fluids; Complex fluids composition can be optimized to support a wide variety of both soluble and membrane proteins; The water gap dimensions can be finely tuned through polymer component.

  3. Gender gaps within management.

    PubMed

    Ronk, L L

    1993-05-01

    Traditional roles need not become self-fulfilling prophecies if managers can bridge the gender gap. Feminine, as well as masculine, characteristics can be incorporated into managerial styles to enhance effective leadership. Autonomy, decision-making and assertiveness are as important as nurturing and caring. What are little girls made of? Little girls are made of sugar and spice and everything nice. What are little boys made of? Little boys are made of rats and snails and puppy dog tails.

  4. Axial flux, modular, permanent-magnet generator with a toroidal winding for wind turbine applications

    SciTech Connect

    Muljadi, E.; Butterfield, C.P.; Wan, Y.H.

    1998-07-01

    Permanent-magnet generators have been used for wind turbines for many years. Many small wind turbine manufacturers use direct-drive permanent-magnet generators. For wind turbine generators, the design philosophy must cover the following characteristics: low cost, light weight, low speed, high torque, and variable speed generation. The generator is easy to manufacture and the design can be scaled up for a larger size without major retooling. A modular permanent-magnet generator with axial flux direction was chosen. The permanent magnet used is NdFeB or ferrite magnet with flux guide to focus flux density in the air gap. Each unit module of the generator may consist of one, two, or more phases. Each generator can be expanded to two or more unit modules. Each unit module is built from simple modular poles. The stator winding is formed like a torus. Thus, the assembly process is simplified and the winding insertion in the slot is less tedious. The authors built a prototype of one unit module and performed preliminary tests in the laboratory. Follow up tests will be conducted in the lab to improve the design.

  5. Patterns of Flux Emergence

    NASA Astrophysics Data System (ADS)

    Title, A.; Cheung, M.

    2008-05-01

    The high spatial resolution and high cadence of the Solar Optical Telescope on the JAXA Hinode spacecraft have allowed capturing many examples of magnetic flux emergence from the scale of granulation to active regions. The observed patterns of emergence are quite similar. Flux emerges as a array of small bipoles on scales from 1 to 5 arc seconds throughout the region that the flux eventually condenses. Because the fields emerging from the underlying flux rope my appear many in small segments and the total flux (absolute sum) is not a conserved quantity the amount of total flux on the surface may vary significantly during the emergence process. Numerical simulations of flux emergence exhibit patterns similar to observations. Movies of both observations and numerical simulations will be presented.

  6. GapBlaster-A Graphical Gap Filler for Prokaryote Genomes.

    PubMed

    de Sá, Pablo H C G; Miranda, Fábio; Veras, Adonney; de Melo, Diego Magalhães; Soares, Siomar; Pinheiro, Kenny; Guimarães, Luis; Azevedo, Vasco; Silva, Artur; Ramos, Rommel T J

    2016-01-01

    The advent of NGS (Next Generation Sequencing) technologies has resulted in an exponential increase in the number of complete genomes available in biological databases. This advance has allowed the development of several computational tools enabling analyses of large amounts of data in each of the various steps, from processing and quality filtering to gap filling and manual curation. The tools developed for gap closure are very useful as they result in more complete genomes, which will influence downstream analyses of genomic plasticity and comparative genomics. However, the gap filling step remains a challenge for genome assembly, often requiring manual intervention. Here, we present GapBlaster, a graphical application to evaluate and close gaps. GapBlaster was developed via Java programming language. The software uses contigs obtained in the assembly of the genome to perform an alignment against a draft of the genome/scaffold, using BLAST or Mummer to close gaps. Then, all identified alignments of contigs that extend through the gaps in the draft sequence are presented to the user for further evaluation via the GapBlaster graphical interface. GapBlaster presents significant results compared to other similar software and has the advantage of offering a graphical interface for manual curation of the gaps. GapBlaster program, the user guide and the test datasets are freely available at https://sourceforge.net/projects/gapblaster2015/. It requires Sun JDK 8 and Blast or Mummer.

  7. GapBlaster-A Graphical Gap Filler for Prokaryote Genomes.

    PubMed

    de Sá, Pablo H C G; Miranda, Fábio; Veras, Adonney; de Melo, Diego Magalhães; Soares, Siomar; Pinheiro, Kenny; Guimarães, Luis; Azevedo, Vasco; Silva, Artur; Ramos, Rommel T J

    2016-01-01

    The advent of NGS (Next Generation Sequencing) technologies has resulted in an exponential increase in the number of complete genomes available in biological databases. This advance has allowed the development of several computational tools enabling analyses of large amounts of data in each of the various steps, from processing and quality filtering to gap filling and manual curation. The tools developed for gap closure are very useful as they result in more complete genomes, which will influence downstream analyses of genomic plasticity and comparative genomics. However, the gap filling step remains a challenge for genome assembly, often requiring manual intervention. Here, we present GapBlaster, a graphical application to evaluate and close gaps. GapBlaster was developed via Java programming language. The software uses contigs obtained in the assembly of the genome to perform an alignment against a draft of the genome/scaffold, using BLAST or Mummer to close gaps. Then, all identified alignments of contigs that extend through the gaps in the draft sequence are presented to the user for further evaluation via the GapBlaster graphical interface. GapBlaster presents significant results compared to other similar software and has the advantage of offering a graphical interface for manual curation of the gaps. GapBlaster program, the user guide and the test datasets are freely available at https://sourceforge.net/projects/gapblaster2015/. It requires Sun JDK 8 and Blast or Mummer. PMID:27171416

  8. Remote sensing model for CO2 flux in wheat fields

    NASA Astrophysics Data System (ADS)

    Zhang, Renhua; Sun, Xiaomin; Zhu, Zhilin; Su, Hongbo; Chen, Gang

    1998-08-01

    In this paper we presented a model for calculating CO2 flux in the wheat field based on field simulate test. We adopted crop transpiration as 'information picker' of CO2 flux instead of the potential evaporation and crop water stress index. Another crucial factor is leaf index and air vapor saturation deficit. Experimental coefficient is equal to 1/58. Calculating values have a good agreement with real measurements. The model is useful to estimate regional distribution of CO2 flux.

  9. Short- and medium-chain chlorinated paraffins in air and soil of subtropical terrestrial environment in the pearl river delta, South China: distribution, composition, atmospheric deposition fluxes, and environmental fate.

    PubMed

    Wang, Yan; Li, Jun; Cheng, Zhineng; Li, Qilu; Pan, Xiaohui; Zhang, Ruijie; Liu, Di; Luo, Chunling; Liu, Xiang; Katsoyiannis, Athanasios; Zhang, Gan

    2013-03-19

    Research on the environmental fate of short- and medium-chain chlorinated paraffins (SCCPs and MCCPs) in highly industrialized subtropical areas is still scarce. Air, soil, and atmospheric deposition process in the Pearl River Delta of South China were investigated, and the average SCCP and MCCP concentrations were 5.2 μg/sampler (17.69 ng/m(3)) and 4.1 μg/sampler for passive air samples, 18.3 and 59.3 ng/g for soil samples, and 5.0 and 5.3 μg/(m(2)d) for deposition samples, respectively. Influenced by primary sources and the properties of chlorinated paraffins (CPs), a gradient trend of concentrations and a fractionation of composition from more to less industrialized areas were discovered. Intense seasonal variations with high levels in summer air and winter deposition samples indicated that the air and deposition CP levels were controlled mainly by the vapor and particle phase, respectively. Complex environmental processes like volatilization and fractionation resulted in different CP profiles in different environment matrixes and sampling locations, with C(10-11) C(l6-7) and C(14) C(l6-7), C(10-12) C(l6-7) and C(14) C(l6-8), and C(11-12) C(l6-8) and C(14) C(l7-8) dominating in air, soil, and atmospheric deposition, respectively. Shorter-chain and less chlorinated congeners were enriched in air in the less industrialized areas, while longer-chain and higher chlorinated congeners were concentrated in soil in the more industrialized areas. This is suggesting that the gaseous transport of CPs is the dominant mechanism responsible for the higher concentrations of lighter and likely more mobile CPs in the rural areas.

  10. Comparing three gap filling methods for eddy covariance crop evapotranspiration measurements within a hilly agricultural catchment

    NASA Astrophysics Data System (ADS)

    Boudhina, Nissaf; Prévot, Laurent; Zitouna Chebbi, Rim; Mekki, Insaf; Jacob, Frédéric; Ben Mechlia, Netij; Masmoudi, Moncef

    2015-04-01

    Hilly watersheds are widespread throughout coastal areas around the Mediterranean Basin. They experience agricultural intensification since hilly topographies allow water-harvesting techniques that compensate for rainfall storage, water being a strong limiting factor for crop production. Their fragility is likely to increase with climate change and human pressure. Within semi-arid hilly watershed conditions, evapotranspiration (ETR) is a major term of both land surface energy and water balances. Several methods allow determining ETR, based either on direct measurements, or on estimations and forecast from weather and soil moisture data using simulation models. Among these methods, eddy covariance technique is based on high-frequency measurements of fluctuations of wind speed and air temperature / humidity, to directly determine the convective fluxes between land surface and atmosphere. In spite of experimental and instrumental progresses, datasets of eddy covariance measurements often experience large portions of missing data. The latter results from energy power failure, experimental maintenance, instrumental troubles such as krypton hygrometer malfunctioning because of air humidity, or quality assessment based filtering in relation to spatial homogeneity and temporal stationarity of turbulence within surface boundary layer. This last item is all the more important as hilly topography, when combined with strong winds, tends to increase turbulence within surface boundary layer. The main objective of this study is to establish gap-filling procedures to provide complete chronicles of eddy-covariance measurements of crop evapotranspiration (ETR) within a hilly agricultural watershed. We focus on the specific conditions induced by the combination of hilly topography and wind direction, by discriminating between upslope and downslope winds. The experiment was set for three field configurations within hilly conditions: two flux measurement stations (A, B) were installed

  11. SOUTHWEST REGIONAL GAP LAND COVER

    EPA Science Inventory

    The Gap Analysis Program is a national inter-agency program that maps the distribution

    of plant communities and selected animal species and compares these distributions with land

    stewardship to identify gaps in biodiversity protection. GAP uses remote satellite imag...

  12. Skills Gaps in Australian Firms

    ERIC Educational Resources Information Center

    Lindorff, Margaret

    2011-01-01

    This paper reports the results of a survey of more than 2000 managers examining perceptions of skills gaps in a range of Australian firms. It finds that three quarters report a skills gap, and almost one third report skills gaps across the whole organisation. Firm size and industry differences exist in perceptions of the effect of the skills gap…

  13. Bridging Gaps Between Refractory Tiles

    NASA Technical Reports Server (NTRS)

    Haney, J. W. J.

    1982-01-01

    Excessively large gaps between tiles on Space Shuttle eliminated without time-consuming and costly procedure of removing and replacing tiles. Ceramic tile silver is bonded in gap. Bonded silver prevents airframe under gap from getting too hot during reentry and presents aerodynamically smooth exterior surface.

  14. 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.

  15. Air Pollution

    MedlinePlus

    Air pollution is a mixture of solid particles and gases in the air. Car emissions, chemicals from factories, ... Ozone, a gas, is a major part of air pollution in cities. When ozone forms air pollution, it's ...

  16. Return flux experiment

    NASA Technical Reports Server (NTRS)

    Tveekrem, June L.

    1992-01-01

    All spacecraft emit molecules via outgassing, thruster plumes, vents, etc. The return flux is the portion of those molecules that scatter from the ambient atmosphere and return to the spacecraft. Return flux allows critical spacecraft surfaces to become contaminated even when there is no direct line of sight between the contamination source and the critical surface. Data from the Long Duration Exposure Facility (LDEF) show that contamination of LDEF surfaces could not have come entirely from direct flux. The data suggest significant return flux. Several computer models have been developed to simulate return flux, but the predictions have never been verified in orbit. Large uncertainties in predictions lead to overly conservative spacecraft designs. The purpose of the REturn FLux EXperiment (REFLEX) is to fly a controlled experiment that can be directly compared with predictions from several models.

  17. Return flux experiment

    NASA Astrophysics Data System (ADS)

    Tveekrem, June L.

    All spacecraft emit molecules via outgassing, thruster plumes, vents, etc. The return flux is the portion of those molecules that scatter from the ambient atmosphere and return to the spacecraft. Return flux allows critical spacecraft surfaces to become contaminated even when there is no direct line of sight between the contamination source and the critical surface. Data from the Long Duration Exposure Facility (LDEF) show that contamination of LDEF surfaces could not have come entirely from direct flux. The data suggest significant return flux. Several computer models have been developed to simulate return flux, but the predictions have never been verified in orbit. Large uncertainties in predictions lead to overly conservative spacecraft designs. The purpose of the REturn FLux EXperiment (REFLEX) is to fly a controlled experiment that can be directly compared with predictions from several models.

  18. Mind the gap

    NASA Astrophysics Data System (ADS)

    Bhagwat, M. S.; Krassnigg, A.; Maris, P.; Roberts, C. D.

    2007-03-01

    In this summary of the application of Dyson-Schwinger equations to the theory and phenomenology of hadrons, some deductions following from a nonperturbative, symmetry-preserving truncation are highlighted, notable amongst which are results for pseudoscalar mesons. We also describe inferences from the gap equation relating to the radius of convergence of a chiral expansion, applications to heavy-light and heavy-heavy mesons, and quantitative estimates of the contribution of quark orbital angular momentum in pseudoscalar mesons; and recapitulate upon studies of nucleon electromagnetic form factors.

  19. Photonic band gap materials

    NASA Astrophysics Data System (ADS)

    Cassagne, D.

    Photonic band gap materials Photonic band gap materials are periodic dielectric structures that control the propagation of electromagnetic waves. We describe the plane wave method, which allows to calculate the band structures of photonic crystals. By symmetry analysis and a perturbative approach, we predict the appearance of the low energy photonic band gaps of hexagonal structures. We propose new two-dimensional structures called graphite and boron nitride. Using a transfer matrix method, we calculate the transmission of the graphite structure and we show the crucial role of the coupling with external modes. We study the appearance of allowed modes in the photonic band gap by the introduction of localized defects in the periodicity. Finally, we discuss the properties of opals formed by self-organized silica microspheres, which are very promising for the fabrication of three-dimensional photonic crystals. Les matériaux à bandes interdites photoniques sont des structures diélectriques périodiques qui contrôlent la propagation des ondes électromagnétiques. Nous décrivons la méthode des ondes planes qui permet de calculer les structures de bandes des cristaux photoniques. Par une analyse de la symétrie et une approche perturbative, nous précisons les conditions d'existence des bandes interdites de basse énergie. Nous proposons de nouvelles structures bidimensionnelles appelées graphite et nitrure de bore. Grâce à une méthode de matrices de transfert, nous calculons la transmission de la structure graphite et nous mettons en évidence le rôle fondamental du couplage avec les modes extérieurs. Nous étudions l'apparition de modes permis dans la bande interdite grâce à l'introduction de défauts dans la périodicité. Enfin, nous discutons les propriétés des opales constituées de micro-billes de silice auto-organisées, qui sont très prometteuses pour la fabrication de cristaux photoniques tridimensionnels.

  20. Air-surface exchange of Hg0 measured by collocated micrometeorological and enclosure methods - Part 1: Data comparability and method characteristics

    NASA Astrophysics Data System (ADS)

    Zhu, W.; Sommar, J.; Lin, C.-J.; Feng, X.

    2014-09-01

    Reliable quantification of air-biosphere exchange flux of elemental mercury vapor (Hg0) is crucial for understanding global biogeochemical cycle of mercury. However, there has not been a standard analytical protocol for flux quantification, and little attention has been devoted to characterize the temporal variability and comparability of fluxes measured by different methods. In this study, we deployed a collocated set of micro-meteorological (MM) and enclosure measurement systems to quantify Hg0 flux over bare soil and low standing crop in an agricultural field. The techniques include relaxed eddy accumulation (REA), modified Bowen-ratio (MBR), aerodynamic gradient (AGM) as well as dynamic flux chambers of traditional (TDFC) and novel (NDFC) designs. The five systems and their measured fluxes were cross-examined with respect to magnitude, temporal trend and sensitivity to environmental variables. Fluxes measured by the MM and DFC methods showed distinct temporal trends. The former exhibited a highly dynamic temporal variability while the latter had much gradual temporal features. The diurnal characteristics reflected the difference in the fundamental processes driving the measurements. The correlations between NDFC and TDFC fluxes and between MBR and AGM fluxes were significant (R > 0.8, p < 0.05), but the correlation between DFC and MM instantaneous fluxes were from weak to moderate (R = 0.1-0.5). Statistical analysis indicated that the median of turbulent fluxes estimated by the three independent MM-techniques were not significantly different. Cumulative flux measured by TDFC is considerably lower (42% of AGM and 31% of MBR fluxes) while those measured by NDFC, AGM and MBR were similar (< 10% difference). This implicates that the NDFC technique, which accounts for internal friction velocity, effectively bridged the gap in measured Hg0 flux compared to MM techniques. Cumulated flux measured by REA was ~60% higher than the gradient-based fluxes. Environmental

  1. Study of Discharging Characteristics of Hollow Cathode Surge Protective Gap

    NASA Astrophysics Data System (ADS)

    Yao, Xueling; Chen, Jingliang; Xu, Xiaowei; Liu, Yong; Zhao, Yong

    2010-02-01

    A hollow cathode surge protective gap (HCSPG) was designed, and the discharge characteristics was investigated in an air and nitrogen gas environment. For both the gap spacing D and the hole diameter varphi of HCSPG of 3 mm, the voltage protective value Up of HCSPG is about 3.5 kV and its converting time tc exceeds 100 ns at an air pressure from 10 Pa to 100 Pa. The maximum converting time tc from glow to arc discharging reaches 1600 ns at an air pressure of 100 Pa, while the minimum converting time tc is 120 ns at 10 Pa. For a triggered HCSPG, Up is reduced to about 1.6 kV while the converting time is 120 ns with a semiconductor trigger device and 50 ns with a dielectric porcelain trigger device under an air pressure of 100 Pa.

  2. Wind tunnels vs. flux chambers: Area source emission measurements and the necessity for VOC and odour correction factors

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Wind tunnels and flux chambers have been used to measure fluxes of volatile organic compounds (VOC), odour, and ammonia (NH3) with little regard to air velocity or sweep air flow rates. As a result, flux measurements have been highly variable and scientists have been in disagreement as to the better...

  3. Heat flux measurements

    NASA Technical Reports Server (NTRS)

    Liebert, Curt H.; Weikle, Donald H.

    1989-01-01

    A new automated, computer controlled heat flux measurement facility is described. Continuous transient and steady-state surface heat flux values varying from about 0.3 to 6 MW/sq m over a temperature range of 100 to 1200 K can be obtained in the facility. An application of this facility is the development of heat flux gauges for continuous fast transient surface heat flux measurement on turbine blades operating in space shuttle main engine turbopumps. The facility is useful for durability testing at fast temperature transients.

  4. Aspects of flux compactification

    NASA Astrophysics Data System (ADS)

    Liu, Tao

    In this thesis, we study three main aspects of flux compactifications: (1) classify supergravity solutions from flux compactification; (2) construct flux-deformed geometry and 4D low-energy theory to describe these flux vacua; and (3) study 4D particle phenomenology and cosmology of flux vacua. In the first part, we review G-structure, the basic tool to study supersymmetric flux solutions, and some typical solutions obtained in heterotic, type IIA and type IIB string theories. Then we present a comprehensive classification of supersymmetric vacua of M-theory compactification on 7D manifolds with general four-form fluxes. We analyze the cases where the resulting four-dimensional vacua have N = 1, 2, 3, 4 supersymmetry and the internal space allows for SU(2)-, SU(3)- or G 2-structures. In particular, we find for N = 2 supersymmetry, that the external space-time is Minkowski and the base manifold of the internal space is conformally Kahler for SU(2) structures, while for SU(3) structures the internal space has to be Einstein-Sasaki and no internal fluxes are allowed. Moreover, we provide a new vacuum with N = 1 supersymmetry and SU(3) structure, where all fluxes are non-zero and the first order differential equations are solved. In the second part, we simply review the methods used to construct one subclass of fluxed-deformed geometry or the so-called "twisted manifold", and the associated 4D effective theory describing these flux vacua. Then by employing (generalized) Scherk-Schwarz reduction, we construct the geometric twisting for Calabi-Yau manifolds of Voisin-Borcea type (K 3 x T2)/ Z2 and study the superpotential in a type IIA orientifold based on this geometry. The twists modify the direct product by fibering the K 3 over T2 while preserving the Z2 involution. As an important application, the Voisin-Borcea class contains T6/( Z2 x Z2 ), the usual setting for intersecting D6 brane model building. Past work in this context considered only those twists inherited

  5. Denoising surface renewal flux density measurements

    NASA Astrophysics Data System (ADS)

    Shapland, T.; Paw U, K.; Snyder, R. L.; McElrone, A.; Calderon Orellana, A.; Williams, L.

    2012-12-01

    When combined with net radiation and ground heat flux density measurements, surface renewal sensible heat flux density measurements can be used to obtain latent heat flux density, and therefore evapotranspiration, via the energy balance residual. Surface renewal is based on analyzing the energy and mass budget of air parcels that interact with plant canopies. The air parcels are manifested as ramp-like shapes in turbulent scalar time series data, and the amplitude and period of the ramps are used to calculate the flux densities. The root mean square error between calibrated surface renewal and eddy covariance is generally twice the root mean square error between two eddy covariance systems. In this presentation, we evaluate the efficacy of various methods for reducing the random error in surface renewal sensible heat flux density measurements. These methods include signal de-spiking, conventional low-pass filtering, wavelet-based filtering, ramp signal to noise thresholds, ramp period scaling, novel rearrangements of the Van Atta procedure (Arch Mech 29:161-171, 1977) for resolving the ramp amplitude and ramp period, sensor replication, and optimization of sensor placement.

  6. Turbine blade tip gap reduction system

    DOEpatents

    Diakunchak, Ihor S.

    2012-09-11

    A turbine blade sealing system for reducing a gap between a tip of a turbine blade and a stationary shroud of a turbine engine. The sealing system includes a plurality of flexible seal strips extending from a pressure side of a turbine blade generally orthogonal to the turbine blade. During operation of the turbine engine, the flexible seal strips flex radially outward extending towards the stationary shroud of the turbine engine, thereby reducing the leakage of air past the turbine blades and increasing the efficiency of the turbine engine.

  7. Gapped domain walls, gapped boundaries, and topological degeneracy.

    PubMed

    Lan, Tian; Wang, Juven C; Wen, Xiao-Gang

    2015-02-20

    Gapped domain walls, as topological line defects between (2+1)D topologically ordered states, are examined. We provide simple criteria to determine the existence of gapped domain walls, which apply to both Abelian and non-Abelian topological orders. Our criteria also determine which (2+1)D topological orders must have gapless edge modes, namely, which (1+1)D global gravitational anomalies ensure gaplessness. Furthermore, we introduce a new mathematical object, the tunneling matrix W, whose entries are the fusion-space dimensions W(ia), to label different types of gapped domain walls. By studying many examples, we find evidence that the tunneling matrices are powerful quantities to classify different types of gapped domain walls. Since a gapped boundary is a gapped domain wall between a bulk topological order and the vacuum, regarded as the trivial topological order, our theory of gapped domain walls inclusively contains the theory of gapped boundaries. In addition, we derive a topological ground state degeneracy formula, applied to arbitrary orientable spatial 2-manifolds with gapped domain walls, including closed 2-manifolds and open 2-manifolds with gapped boundaries.

  8. Video Meteor Fluxes

    NASA Technical Reports Server (NTRS)

    Campbell-Brown, M. D.; Braid, D.

    2011-01-01

    The flux of meteoroids, or number of meteoroids per unit area per unit time, is critical for calibrating models of meteoroid stream formation and for estimating the hazard to spacecraft from shower and sporadic meteors. Although observations of meteors in the millimetre to centimetre size range are common, flux measurements (particularly for sporadic meteors, which make up the majority of meteoroid flux) are less so. It is necessary to know the collecting area and collection time for a given set of observations, and to correct for observing biases and the sensitivity of the system. Previous measurements of sporadic fluxes are summarized in Figure 1; the values are given as a total number of meteoroids striking the earth in one year to a given limiting mass. The Gr n et al. (1985) flux model is included in the figure for reference. Fluxes for sporadic meteoroids impacting the Earth have been calculated for objects in the centimeter size range using Super-Schmidt observations (Hawkins & Upton, 1958); this study used about 300 meteors, and used only the physical area of overlap of the cameras at 90 km to calculate the flux, corrected for angular speed of meteors, since a large angular speed reduces the maximum brightness of the meteor on the film, and radiant elevation, which takes into account the geometric reduction in flux when the meteors are not perpendicular to the horizontal. They bring up corrections for both partial trails (which tends to increase the collecting area) and incomplete overlap at heights other than 90 km (which tends to decrease it) as effects that will affect the flux, but estimated that the two effects cancelled one another. Halliday et al. (1984) calculated the flux of meteorite-dropping fireballs with fragment masses greater than 50 g, over the physical area of sky accessible to the MORP fireball cameras, counting only observations in clear weather. In the micron size range, LDEF measurements of small craters on spacecraft have been used to

  9. Mass and Ozone Fluxes from the Lowermost Stratosphere

    NASA Technical Reports Server (NTRS)

    Schoeberl, Mark R.; Olsen, Mark A.

    2004-01-01

    Net mass flux from the stratosphere to the troposphere can be computed from the heating rate along the 380K isentropic surface and the time rate of change of the mass of the lowermost stratosphere (the region between the tropopause and the 380K isentrope). Given this net mass flux and the cross tropopause diabatic mass flux, the residual adiabatic mass flux across the tropopause can also be estimated. These fluxes have been computed using meteorological fields from a free-running general circulation model (FVGCM) and two assimilation data sets, FVDAS, and UKMO. The data sets tend to agree that the annual average net mass flux for the Northern Hemisphere is about 1P10 kg/s. There is less agreement on the southern Hemisphere flux that might be half as large. For all three data sets, the adiabatic mass flux is computed to be from the upper troposphere into the lowermost stratosphere. This flux will dilute air entering from higher stratospheric altitudes. The mass fluxes are convolved with ozone mixing ratios from the Goddard 3D CTM (which uses the FVGCM) to estimate the cross-tropopause transport of ozone. A relatively large adiabatic flux of tropospheric ozone from the tropical upper troposphere into the extratropical lowermost stratosphere dilutes the stratospheric air in the lowermost stratosphere. Thus, a significant fraction of any measured ozone STE may not be ozone produced in the higher Stratosphere. The results also illustrate that the annual cycle of ozone concentration in the lowermost stratosphere has as much of a role as the transport in the seasonal ozone flux cycle. This implies that a simplified calculation of ozone STE mass from air mass and a mean ozone mixing ratio may have a large uncertainty.

  10. Production flux of sea spray aerosol

    SciTech Connect

    de Leeuw, G.; Lewis, E.; Andreas, E. L.; Anguelova, M. D.; Fairall, C. W.; O’Dowd, C.; Schulz, M.; Schwartz, S. E.

    2011-05-07

    Knowledge of the size- and composition-dependent production flux of primary sea spray aerosol (SSA) particles and its dependence on environmental variables is required for modeling cloud microphysical properties and aerosol radiative influences, interpreting measurements of particulate matter in coastal areas and its relation to air quality, and evaluating rates of uptake and reactions of gases in sea spray drops. This review examines recent research pertinent to SSA production flux, which deals mainly with production of particles with r{sub 80} (equilibrium radius at 80% relative humidity) less than 1 {micro}m and as small as 0.01 {micro}m. Production of sea spray particles and its dependence on controlling factors has been investigated in laboratory studies that have examined the dependences on water temperature, salinity, and the presence of organics and in field measurements with micrometeorological techniques that use newly developed fast optical particle sizers. Extensive measurements show that water-insoluble organic matter contributes substantially to the composition of SSA particles with r{sub 80} < 0.25 {micro}m and, in locations with high biological activity, can be the dominant constituent. Order-of-magnitude variation remains in estimates of the size-dependent production flux per white area, the quantity central to formulations of the production flux based on the whitecap method. This variation indicates that the production flux may depend on quantities such as the volume flux of air bubbles to the surface that are not accounted for in current models. Variation in estimates of the whitecap fraction as a function of wind speed contributes additional, comparable uncertainty to production flux estimates.

  11. LCLS Spectral Flux Viewer

    2005-10-25

    This application (FluxViewer) is a tool for displaying spectral flux data for the Linac Coherent Light Source (LCLS). This tool allows the user to view sliced spatial and energy distributions of the photons selected for specific energies and positions transverse to the beam axis.

  12. Étude numérique de la convection mixte dans une cavité en forme de « T » soumise à un flux de chaleur constant et ventilée par le bas à l'aide d'un jet d'air verticalNumerical study of mixed convection in a ``T'' form cavity submitted to constant heat flux and ventilated from below with a vertical jet

    NASA Astrophysics Data System (ADS)

    Najam, Mostafa; El Alami, Mustapha; Hasnaoui, Mohammed; Amahmid, Abdelkhalk

    A numerical study of the mixed convection is presented in a "T" form cavity, heated with constant heat flux and submitted to a vertical jet of fresh air from below. The heating blocks are identical and the system presents a symmetry with respect to a vertical axis passing by the middle of the openings. The governing equations are solved using the finite difference method. The parameters of control are the Rayleigh number (0⩽Ra⩽10 6), the Reynolds number (1⩽Re⩽1000), the Prandtl number (Pr=0.72), the relative height of the heating blocks ( B= h/ H=0.5), the dimension C of admission and evacuation openings ( C= l/ L=0.15) and the relative distance D between the blocks ( D= d/ L=0.50). The results obtained, with H/ L=1, show the existence of multiple solutions on which the resulting heat transfer depends significantly. To cite this article: M. Najam et al., C. R. Mecanique 330 (2002) 461-467.

  13. A simple laboratory system for diffusive radon flux measurements

    NASA Astrophysics Data System (ADS)

    Kranrod, C.; Chanyotha, S.; Tonlublao, S.; Burnett, W. C.

    2015-05-01

    This study designed a simple, custom-made system to estimate the diffusive radon flux from solid materials (e.g., sediments, soils, building materials). Determination of the radon flux is based on the measurement of the radon activity in the air over time inside a closed loop system. For sediments, the system consists of wet sediment and water inside a gas-tight flask connected in a closed loop to a drying system and a radon analyzer (Durridge RAD7). The flux is determined based on an initial slope method in which the slope of radon activities vs. time plot during the first 12 h is evaluated. The slope is then multiplied by the total air volume and divided by the exposed sediment area to obtain the radon flux. The minimal thickness or mass of wet sediment should be about 4 cm or (equivalent to approximately 150 g of wet sediment) to obtain a reliable radon diffusive flux in this study.

  14. The Gap-Tpc

    NASA Astrophysics Data System (ADS)

    Rossi, B.; Anastasio, A.; Boiano, A.; Catalanotti, S.; Cocco, A. G.; Covone, G.; Di Meo, P.; Longo, G.; Vanzanella, A.; Walker, S.; Wang, H.; Wang, Y.; Fiorillo, G.

    2016-02-01

    Several experiments have been conducted worldwide, with the goal of observing low-energy nuclear recoils induced by WIMPs scattering off target nuclei in ultra-sensitive, low-background detectors. In the last few decades noble liquid detectors designed to search for dark matter in the form of WIMPs have been extremely successful in improving their sensitivities and setting the best limits. One of the crucial problems to be faced for the development of large size (multi ton-scale) liquid argon experiments is the lack of reliable and low background cryogenic PMTs: their intrinsic radioactivity, cost, and borderline performance at 87 K rule them out as a possible candidate for photosensors. We propose a brand new concept of liquid argon-based detector for direct dark matter search: the Geiger-mode Avalanche Photodiode Time Projection Chamber (GAP-TPC) optimized in terms of residual radioactivity of the photosensors, energy and spatial resolution, light and charge collection efficiency.

  15. Undecidability of the spectral gap.

    PubMed

    Cubitt, Toby S; Perez-Garcia, David; Wolf, Michael M

    2015-12-10

    The spectral gap--the energy difference between the ground state and first excited state of a system--is central to quantum many-body physics. Many challenging open problems, such as the Haldane conjecture, the question of the existence of gapped topological spin liquid phases, and the Yang-Mills gap conjecture, concern spectral gaps. These and other problems are particular cases of the general spectral gap problem: given the Hamiltonian of a quantum many-body system, is it gapped or gapless? Here we prove that this is an undecidable problem. Specifically, we construct families of quantum spin systems on a two-dimensional lattice with translationally invariant, nearest-neighbour interactions, for which the spectral gap problem is undecidable. This result extends to undecidability of other low-energy properties, such as the existence of algebraically decaying ground-state correlations. The proof combines Hamiltonian complexity techniques with aperiodic tilings, to construct a Hamiltonian whose ground state encodes the evolution of a quantum phase-estimation algorithm followed by a universal Turing machine. The spectral gap depends on the outcome of the corresponding 'halting problem'. Our result implies that there exists no algorithm to determine whether an arbitrary model is gapped or gapless, and that there exist models for which the presence or absence of a spectral gap is independent of the axioms of mathematics.

  16. Fabrication of Thin Film Heat Flux Sensors

    NASA Technical Reports Server (NTRS)

    Will, Herbert A.

    1992-01-01

    Prototype thin film heat flux sensors have been constructed and tested. The sensors can be applied to propulsion system materials and components. The sensors can provide steady state and fast transient heat flux information. Fabrication of the sensor does not require any matching of the mounting surface. Heat flux is proportional to the temperature difference across the upper and lower surfaces of an insulation material. The sensor consists of an array of thermocouples on the upper and lower surfaces of a thin insulating layer. The thermocouples for the sensor are connected in a thermopile arrangement. A 100 thermocouple pair heat flux sensor has been fabricated on silicon wafers. The sensor produced an output voltage of 200-400 microvolts when exposed to a hot air heat gun. A 20 element thermocouple pair heat flux sensor has been fabricated on aluminum oxide sheet. Thermocouples are Pt-Pt/Rh with silicon dioxide as the insulating material. This sensor produced an output of 28 microvolts when exposed to the radiation of a furnace operating at 1000 C. Work is also underway to put this type of heat flux sensor on metal surfaces.

  17. Gap heating with pressure gradients. [for Shuttle Orbiter thermal protection system tiles

    NASA Technical Reports Server (NTRS)

    Scott, C. D.; Maraia, R. J.

    1979-01-01

    The heating rate distribution and temperature response on the gap walls of insulating tiles is analyzed to determine significant phenomena and parameters in flows where there is an external surface pressure gradient. Convective heating due to gap flow, modeled as fully developed pipe flow, is coupled with a two-dimensional thermal model of the tiles that includes conduction and radiative heat transfer. To account for geometry and important environmental parameters, scale factors are obtained by curve-fitting measured temperatures to analytical solutions. These scale factors are then used to predict the time-dependent gap heat flux and temperature response of tile gaps on the Space Shuttle Orbiter during entry.

  18. Terminology gap in hydrological cycle

    NASA Astrophysics Data System (ADS)

    Zhuo, Lu; Han, Dawei

    2016-04-01

    Water is central to life on Earth. People have been trying to understand how water moves in the hydrosphere throughout the human history. In the 9th century BC, the famous Greek poet Homer described the hydrological cycle in Iliad as "okeanos whose stream bends back in a circle" with a belief that rivers are ocean-fed from subterranean seas. Later, Aristotle (4th century BC) claimed that most of the water came from underground caverns in which air was transformed into water. It was only until 1674, French scientist Perrault developed the correct concept of the water cycle. In modern times, scientists are interested in understanding the individual processes of the hydrological cycle with a keen focus on runoff which supplies water to rivers, lakes, and oceans. Currently, the prevailing concepts on runoff processes include 'infiltration excess runoff' and 'saturation excess runoff'. However, there is no term to describe another major runoff due to the excess beyond the soil water holding capacity (i.e., the field capacity). We argue that a new term should be introduced to fill this gap, and it could be called 'holding excess runoff' which is compatible with the convention. This new term is significant in correcting a half-century misnomer where 'holding excess runoff' has been incorrectly named as 'saturation excess runoff', which was introduced by the Xinanjiang model in China in 1960s. Similar concept has been adopted in many well-known hydrological models such as PDM and HBV in which the saturation refers to the field capacity. The term 'holding excess runoff' resolves such a common confusion in the hydrological community.

  19. Intramolecular Nuclear Flux Densities

    NASA Astrophysics Data System (ADS)

    Barth, I.; Daniel, C.; Gindensperger, E.; Manz, J.; PéRez-Torres, J. F.; Schild, A.; Stemmle, C.; Sulzer, D.; Yang, Y.

    The topic of this survey article has seen a renaissance during the past couple of years. Here we present and extend the results for various phenomena which we have published from 2012-2014, with gratitude to our coauthors. The new phenomena include (a) the first reduced nuclear flux densities in vibrating diatomic molecules or ions which have been deduced from experimental pump-probe spectra; these "experimental" nuclear flux densities reveal several quantum effects including (b) the "quantum accordion", i.e., during the turn from bond stretch to bond compression, the diatomic system never stands still — instead, various parts of it with different bond lengths flow into opposite directions. (c) Wavepacket interferometry has been extended from nuclear densities to flux densities, again revealing new phenomena: For example, (d) a vibrating nuclear wave function with compact initial shape may split into two partial waves which run into opposite directions, thus causing interfering flux densities. (e) Tunneling in symmetric 1-dimensional double-well systems yields maximum values of the associated nuclear flux density just below the potential barrier; this is in marked contrast with negligible values of the nuclear density just below the barrier. (f) Nuclear flux densities of pseudorotating nuclei may induce huge magnetic fields. A common methodologic theme of all topics is the continuity equation which connects the time derivative of the nuclear density to the divergence of the flux density, subject to the proper boundary conditions. (g) Nearly identical nuclear densities with different boundary conditions may be related to entirely different flux densities, e.g., during tunneling in cyclic versus non-cyclic systems. The original continuity equation, density and flux density of all nuclei, or of all nuclear degrees of freedom, may be reduced to the corresponding quantities for just a single nucleus, or just a single degree of freedom.

  20. Gap and stripline combined monitor

    DOEpatents

    Yin, Y.

    1986-08-19

    A combined gap and stripline monitor device for measuring the intensity and position of a charged particle beam bunch in a beam pipe of a synchrotron radiation facility is disclosed. The monitor has first and second beam pipe portions with an axial gap therebetween. An outer pipe cooperates with the first beam pipe portion to form a gap enclosure, while inner strips cooperate with the first beam pipe portion to form a stripline monitor, with the stripline length being the same as the gap enclosure length. 4 figs.

  1. Undecidability of the spectral gap

    NASA Astrophysics Data System (ADS)

    Cubitt, Toby S.; Perez-Garcia, David; Wolf, Michael M.

    2015-12-01

    The spectral gap—the energy difference between the ground state and first excited state of a system—is central to quantum many-body physics. Many challenging open problems, such as the Haldane conjecture, the question of the existence of gapped topological spin liquid phases, and the Yang-Mills gap conjecture, concern spectral gaps. These and other problems are particular cases of the general spectral gap problem: given the Hamiltonian of a quantum many-body system, is it gapped or gapless? Here we prove that this is an undecidable problem. Specifically, we construct families of quantum spin systems on a two-dimensional lattice with translationally invariant, nearest-neighbour interactions, for which the spectral gap problem is undecidable. This result extends to undecidability of other low-energy properties, such as the existence of algebraically decaying ground-state correlations. The proof combines Hamiltonian complexity techniques with aperiodic tilings, to construct a Hamiltonian whose ground state encodes the evolution of a quantum phase-estimation algorithm followed by a universal Turing machine. The spectral gap depends on the outcome of the corresponding ‘halting problem’. Our result implies that there exists no algorithm to determine whether an arbitrary model is gapped or gapless, and that there exist models for which the presence or absence of a spectral gap is independent of the axioms of mathematics.

  2. Gap and stripline combined monitor

    DOEpatents

    Yin, Y.

    1984-02-16

    A combined gap and stripline monitor device for measuring the intensity and position of a charged particle beam bunch in a beam pipe of a synchrotron radiation facility. The monitor has first and second beam pipe portions with an axial gap therebetween. An outer pipe cooperates with the first beam pipe portion to form a gap enclosure, while inner strips cooperate with the first beam pipe portion to form a stripline monitor, with the stripline length being the same as the gap enclosure length.

  3. Gap and stripline combined monitor

    DOEpatents

    Yin, Yan

    1986-01-01

    A combined gap and stripline monitor device (10) for measuring the intensity and position of a charged particle beam bunch in a beam pipe of a synchotron radiation facility. The monitor has first and second beam pipe portions (11a, 11b) with an axial gap (12) therebetween. An outer pipe (14) cooperates with the first beam pipe portion (11a) to form a gap enclosure, while inner strips (23a-d) cooperate with the first beam pipe portion (11a) to form a stripline monitor, with the stripline length being the same as the gap enclosure length.

  4. Directed flux motor

    NASA Technical Reports Server (NTRS)

    Wilson, Andrew (Inventor); Punnoose, Andrew (Inventor); Strausser, Katherine (Inventor); Parikh, Neil (Inventor)

    2011-01-01

    A directed flux motor described utilizes the directed magnetic flux of at least one magnet through ferrous material to drive different planetary gear sets to achieve capabilities in six actuated shafts that are grouped three to a side of the motor. The flux motor also utilizes an interwoven magnet configuration which reduces the overall size of the motor. The motor allows for simple changes to modify the torque to speed ratio of the gearing contained within the motor as well as simple configurations for any number of output shafts up to six. The changes allow for improved manufacturability and reliability within the design.

  5. Heat Flux Sensor

    NASA Technical Reports Server (NTRS)

    1994-01-01

    A heat flux microsensor developed under a NASP Small Business Innovation Research (SBIR) has a wide range of potential commercial applications. Vatell Corporation originally designed microsensors for use in very high temperatures. The company then used the technology to develop heat flux sensors to measure the rate of heat energy flowing in and out of a surface as well as readings on the surface temperature. Additional major advantages include response to heat flux in less than 10 microseconds and the ability to withstand temperatures up to 1,200 degrees centigrade. Commercial applications are used in high speed aerodynamics, supersonic combustion, blade cooling, and mass flow measurements, etc.

  6. Fractional flux lattice and the anyon mean-field approximation

    SciTech Connect

    Pryor, C. )

    1991-12-01

    The anyon mean-field approximation (MFA) is tested by computing the band structure of a charged particle in an infinite two-dimensional square lattice of infinitesimal flux tubes. The band structure and density of states are compared with the MFA and found to be in agreement for {Phi}=1/{ital n}, with {ital n}{gt}3. For {Phi}=1/2 and 1/3, there is no gap, unlike the MFA which predicts a gap. For {Phi}={ital m}/{ital n} (with {ital m}{gt}1), there is a gap, opening up the possibility that a superfluid may form for any rational value of the statistical parameter. A physical realization of the {Phi}=1/2 flux lattice is proposed and a connection between the {Phi}={ital m}/{ital n} lattice and the fractional quantum Hall effect is discussed.

  7. Air Abrasion

    MedlinePlus

    ... delivered directly to your desktop! more... What Is Air Abrasion? Article Chapters What Is Air Abrasion? What Happens? The Pros and Cons Will I Feel Anything? Is Air Abrasion for Everyone? print full article print this ...

  8. Atmospheric discharges and particle fluxes

    NASA Astrophysics Data System (ADS)

    Chilingarian, A.; Chilingaryan, S.; Reymers, A.

    2015-07-01

    Fluxes of the electrons, gamma rays, and neutrons observed by particle detectors located on the Earth's surface during thunderstorms originate so-called Thunderstorm Ground Enhancements (TGEs). The relativistic runaway electron avalanches giving rise to TGEs originate in the thundercloud's lower dipole between the main negatively charged region in the middle of the thundercloud and transient lower positively charged region. Acceleration of electrons in the upper dipole between main negative and main positive charge regions leads to initiation of the terrestrial gamma flashes (TGFs) intensive researched during the last two decades by orbiting gamma ray observatories. TGFs are exceptionally intense, submillisecond bursts of electromagnetic radiation directed to the open space from the thunderstorm atmosphere. Unlike visible lightning, TGF beams do not create a hot plasma channel and optical flash; hence, in the literature they got name "dark lightning." We investigate the TGEs development in 1 min and 1 s time series of particle detector count rates. Synchronized time series of the near-surface electric field and lightning occurrences allows interconnecting two atmospheric phenomena. Registration of the Extensive Air Showers allows approaching problems of relation of the lightning occurrences and particle fluxes.

  9. Gamma radiation from pulsar magnetospheric gaps

    NASA Technical Reports Server (NTRS)

    Chiang, James; Romani, Roger W.

    1992-01-01

    We investigate the production of gamma rays in two pulsar emission models: the 'polar cap' model and the 'outer cap' model. For the former, we have performed detailed simulations of energetic electrons flowing in the vacuum dipole open field line region. In the outer gap case, we generate light curves for various magnetosphere geometries. Using data from radio and optical observations, we construct models for specific viewing angles appropriate to the Crab and Vela pulsars. Phase-resolved spectra are also computed in the polar cap case and provide signatures for testing the models. The calculations have been extended to include millisecond pulsars, and we have been able to predict fluxes and spectra for populations of recycled pulsars, which are compared to COS B data for globular cluster populations.

  10. Hard diffraction with dynamic gap survival

    NASA Astrophysics Data System (ADS)

    Rasmussen, Christine O.; Sjöstrand, Torbjörn

    2016-02-01

    We present a new framework for the modelling of hard diffraction in pp and poverline{p} collisions. It starts from the the approach pioneered by Ingelman and Schlein, wherein the single diffractive cross section is factorized into a Pomeron flux and a Pomeron PDF. To this it adds a dynamically calculated rapidity gap survival factor, derived from the modelling of multiparton interactions. This factor is not relevant for diffraction in ep collisions, giving non-universality between HERA and Tevatron diffractive event rates. The model has been implemented in P ythia 8 and provides a complete description of the hadronic state associated with any hard single diffractive process. Comparisons with poverline{p} and pp data reveal improvement in the description of single diffractive events.

  11. BOREAS TF-4 CO2 and CH4 Chamber Flux Data from the SSA

    NASA Technical Reports Server (NTRS)

    Anderson, Dean; Striegl, Robert; Wickland, Kimberly; Hall, Forrest G. (Editor); Conrad, Sara (Editor)

    2000-01-01

    The BOREAS TF-4 team measured fluxes of CO2 and CH4 across the soil-air interface in four ages of jack pine forest at the BOREAS SSA during August 1993 to March 1995. Gross and net flux of CO2 and flux of CH4 between soil and air are presented for 24 chamber sites in mature jack pine forest, 20-year-old, 4-year-old, and clear cut areas. The data are stored in tabular ASCII files.

  12. Diffusive flux of methane from warm wetlands

    SciTech Connect

    Barber, T.R.; Burke, R.A.; Sackett, W.M. )

    1988-12-01

    Diffusion of methane across the air-water interface from several wetland environments in south Florida was estimated from measured surface water concentrations using an empirically derived gas exchange model. The flux from the Everglades sawgrass marsh system varied widely, ranging from 0.18 + or{minus}0.21 mol CH{sub 4}/sq m/yr for densely vegetated regions to 2.01 + or{minus}0.88 for sparsely vegetated, calcitic mud areas. Despite brackish salinities, a strong methane flux, 1.87 + or{minus}0.63 mol CH{sub 4}/sq m/yr, was estimated for an organic-rich mangrove pond near Florida Bay. The diffusive flux accounted for 23, 36, and 13% of the total amount of CH{sub 4} emitted to the atmosphere from these environments, respectively. The average dissolved methane concentration for an organic-rich forested swamp was the highest of any site at 12.6 microM; however, the calculated diffusive flux from this location, 2.57 + or{minus}1.88 mol CH{sub 4}/sq m/yr, was diminished by an extensive plant canopy that sheltered the air-water interface from the wind. The mean diffusive flux from four freshwater lakes, 0.77 + or{minus}0.73 mol CH{sub 4}/sq m/yr, demonstrated little temperature dependence. The mean diffusive flux for an urbanized, subtropical estuary was 0.06 + or{minus}0.05 mol CH{sub 4}/sq m/yr.

  13. 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.

  14. Assessment of Sea-Air Fluxes of Methane from the East Siberian Arctic Shelf Based on Multi-Year High-Precision Observations in the Atmospheric Boundary Layer and Seawater

    NASA Astrophysics Data System (ADS)

    Salyuk, A.; Semiletov, I. P.; Repina, I.; Chernykh, D.; Kosmach, D.; Shakhova, N. E.

    2015-12-01

    The latitude specific monthly mean (LSMM) methane (CH4) mixing ratio in the Arctic region atmospheric boundary layer (ABL) is established at 1.85 ppm (monitoring station at Barrow, Alaska, USA). This LSMM is about 10% higher than in Antarctica and about 5-7% higher than in the mid-latitudes, where the majority of anthropogenic activity occurs. So far, there is no reasonable explanation for the atmospheric CH4 maximum above the Arctic and no models have succeeded in satisfactorily reproducing the inter-polar gradient, due to the assumption that there are no Arctic region CH4 sources sufficient to serve year-round to maintain the existing maximum. The East Siberian Arctic Shelf (ESAS), from which extensive CH4 release was recently reported, has never been considered to be an atmospheric source of CH4, because no knowledge existed about this area until very recently. One focus of our multi-year ESAS investigations was to collect a comprehensive data set of continuous ABL CH4 mixing ratio measurements along with continuous measurements of dissolved CH4 in the surface water. When collecting the data set, we aimed to assess CH4 fluxes by using top-down and bottom-up approaches. Achieving representative spatial coverage of the study area with high-resolution, high-accuracy measurements was our priority. We collected data from 2006-2012 with a high-accuracy fast CH4 analyzer; two sonic anemometers measured the 3D wind vector and sonic temperature; a meteorological station measured wind speed and direction, moisture, and temperature; and an open path infrared gas analyzer measured H2O and CO2. Other instruments included a pressure transducer and a motion package that measured 6 components of ship's motion and also acceleration, magnetic field, and position. In 2011 and 2012 we performed such measurements in the outer ESAS seepage area. Data were synchronized in time and space to demonstrate correspondence of increased atmospheric CH4 levels (up to 3.2 ppm) to observed

  15. Influence of surface fluxes on polar low development: idealised simulations

    NASA Astrophysics Data System (ADS)

    Terpstra, Annick; Spengler, Thomas

    2016-04-01

    Polar lows develop during marine cold air outbreaks in regions with relative large sea surface temperature (SST) gradients. These conditions are favourable for large surface sensible and latent heat fluxes. Furthermore the differential heating resulting from SST gradients can provide a source for baroclinicity. We utilise an idealised numerical channel model to gain insight in the role of surface turbulence fluxes on the dynamical evolution of polar lows. The initial setup consists of a baroclinic jet in thermal wind balance with a meridional temperature gradient. To mimic cold air outbreaks we prescribe SST that is higher than the low level surface air temperature, where the SST features a meridional gradient similar to the SST gradient in the Nordic Seas during winter. This setup allows for a systematic investigation of the relative contributions from surface sensible and latent heat fluxes on polar low development by varying the intensity of the initial baroclinicity, moisture, and temperature difference between the SST and low level air temperature. In addition we investigate the relative role of sensible or latent heat fluxes with sensitivity experiments where the individual fluxes are switched off. As moisture is one of the main sources for polar low intensification, we analyse the moisture budget of the idealised simulations in greater detail. Identification of moisture sources and sinks, as well as diagnosing the moisture circulation rate shed further light on the role of surface fluxes on the intensification of polar lows.

  16. Modeling Magnetic Flux Ropes

    NASA Astrophysics Data System (ADS)

    Xia, Chun; Keppens, Rony

    2014-01-01

    The magnetic configuration hosting prominences can be a large-scale helical magnetic flux rope. As a necessary step towards future prominence formation studies, we report on a stepwise approach to study flux rope formation. We start with summarizing our recent three-dimensional (3D) isothermal magnetohydrodynamic (MHD) simulation where a flux rope is formed, including gas pressure and gravity. This starts from a static corona with a linear force-free bipolar magnetic field, altered by lower boundary vortex flows around the main polarities and converging flows towards the polarity inversion. The latter flows induce magnetic reconnection and this forms successive new helical loops so that a complete flux rope grows and ascends. After stopping the driving flows, the system relaxes to a stable helical magnetic flux rope configuration embedded in an overlying arcade. Starting from this relaxed isothermal endstate, we next perform a thermodynamic MHD simulation with a chromospheric layer inserted at the bottom. As a result of a properly parametrized coronal heating, and due to radiative cooling and anisotropic thermal conduction, the system further relaxes to an equilibrium where the flux rope and the arcade develop a fully realistic thermal structure. This paves the way to future simulations for 3D prominence formation.

  17. Interspecific Variation in SO2 Flux 1

    PubMed Central

    Olszyk, David M.; Tingey, David T.

    1985-01-01

    The objective of this study was to clarify the relationships among stomatal, residual, and epidermal conductances in determining the flux of SO2 air pollution to leaves. Variations in leaf SO2 and H2O vapor fluxes were determined using four plant species: Pisum sativum L. (garden pea), Lycopersicon esculentum Mill. flacca (mutant of tomato), Geranium carolinianum L. (wild geranium), and Diplacus aurantiacus (Curtis) Jeps. (a native California shrub). Fluxes were measured using the mass-balance approach during exposure to 4.56 micromoles per cubic meter (0.11 microliters per liter) SO2 for 2 hours in a controlled environmental chamber. Flux through adaxial and abaxial leaf surfaces with closed stomata ranged from 1.9 to 9.4 nanomoles per square meter per second for SO2, and 0.3 to 1.3 millimoles per square meter per second for H2O vapor. Flux of SO2 into leaves through stomata ranged from ∼0 to 8.5 (dark) and 3.8 to 16.0 (light) millimoles per square meter per second. Flux of H2O vapor from leaves through stomata ranged from ∼0 to 0.6 (dark) to 0.4 to 0.9 (light) millimole per square meter per second. Lycopersicon had internal flux rates for both SO2 and H2O vapor over twice as high as for the other species. Stomatal conductance based on H2O vapor flux averaged from 0.07 to 0.13 mole per square meter per second among the four species. Internal conductance of SO2 as calculated from SO2 flux was from 0.04 mole per square meter per second lower to 0.06 mole per square meter per second higher than stomatal conductance. For Pisum, Geranium, and Diplacus stomatal conductance was the same or slightly higher than internal conductance, indicating that, in general, SO2 flux could be predicted from stomatal conductance for H2O vapor. However, for the Lycopersicon mutant, internal leaf conductance was much higher than stomatal conductance, indicating that factors inside leaves can play a significant role in determining SO2 flux. PMID:16664551

  18. Quantifying the "chamber effect" in CO2 flux measurements

    NASA Astrophysics Data System (ADS)

    Vihermaa, Leena; Childs, Amy; Long, Hazel; Waldron, Susan

    2014-05-01

    The significance of aquatic CO2 emissions has received attention in recent years. For example annual aquatic emissions in the Amazon basin have been estimated as 500 Mt of carbon1. Methods for determining the flux rates include eddy covariance flux tower measurements, flux estimates calculated from partial pressure of CO2 (pCO2) in water and the use floating flux chambers connected to an infra-red gas analyser. The flux chamber method is often used because it is portable, cheaper and allows smaller scale measurements. It is also a direct method and hence avoids problems related to the estimation of the gas transfer coefficient that is required when fluxes are calculated from pCO2. However, the use of a floating chamber may influence the flux measurements obtained. The chamber shields the water underneath from effects of wind which could lead to lower flux estimates. Wind increases the flux rate by i) causing waves which increase the surface area for efflux, and ii) removing CO2 build up above the water surface, hence maintaining a higher concentration gradient. Many floating chambers have an underwater extension of the chamber below the float to ensure better seal to water surface and to prevent any ingress of atmospheric air when waves rock the chamber. This extension may cause additional turbulence in flowing water and hence lead to overestimation of flux rates. Some groups have also used a small fan in the chamber headspace to ensure thorough mixing of air in the chamber. This may create turbulence inside the chamber which could increase the flux rate. Here we present results on the effects of different chamber designs on the detected flux rates. 1Richey et al. 2002. Outgassing from Amazonian rivers and wetlands as a large tropical source of atmospheric CO2. Nature 416: 617-620.

  19. Measuring the Gap

    PubMed Central

    She, Xinshu; Zhao, Deqing; Scholnick, Jenna

    2016-01-01

    China is a large country where rapid development is accompanied by growing inequalities. How economic inequalities translate to health inequalities is unknown. Baseline health assessment is lacking among rural Chinese children. We aimed at assessing baseline student health of rural Chinese children and comparing them with those of urban children of similar ages. A cross-sectional study was conducted using the 2003 Global School-Based Student Health Survey among 100 students Grade 4 to 6 from rural Guizhou, China. Results were summarized and compared with public data from urban Beijing using multivariate logistic regression models. Rural children are more likely to not wash their hands before a meal (odds ratio [OR] = 5.71, P < .01) and after using the toilet (OR = 5.41, P < .01). They are more likely to feel sick or to get into trouble after drinking (OR = 7.28, P < .01). They are more likely to have used drugs (OR = 8.54, P < .01) and to have no close friends (OR = 8.23, P < .01). An alarming percentage of rural (8.22%) and urban (14.22%) children have had suicidal ideation in the past year (OR = 0.68, P > .05). Rural parents are more likely to not know their children’s whereabouts (OR = 1.81, P < .05). Rural children are more than 4 times likely to have serious injuries (OR = 4.64, P < .01) and to be bullied (OR = 4.01, P < .01). In conclusion, school-age rural Chinese children exhibit more health risk behaviors and fewer protective factors at baseline compared to their urban counterparts. Any intervention aimed at improving child health should take this distributive gap into consideration. PMID:27335999

  20. Paramagnetically induced gapful topological superconductors

    NASA Astrophysics Data System (ADS)

    Daido, Akito; Yanase, Youichi

    2016-08-01

    We propose a generic scenario for realizing gapful topological superconductors (TSCs) from gapless spin-singlet superconductors (SCs). Noncentrosymmetric nodal SCs in two dimensions are shown to be gapful under a Zeeman field, as a result of the cooperation of inversion-symmetry breaking and time-reversal-symmetry breaking. In particular, non-s -wave SCs acquire a large excitation gap. Such paramagnetically induced gapful SCs may be classified into TSCs in the symmetry class D specified by the Chern number. We show nontrivial Chern numbers over a wide parameter range for spin-singlet SCs. A variety of the paramagnetically induced gapful TSCs are demonstrated, including D +p -wave TSC, extended S +p -wave TSC, p +D +f -wave TSC, and s +P -wave TSC. Natural extension toward three-dimensional Weyl SCs is also discussed.

  1. Mind the Gap

    NASA Astrophysics Data System (ADS)

    2008-09-01

    Astronomers have been able to study planet-forming discs around young Sun-like stars in unsurpassed detail, clearly revealing the motion and distribution of the gas in the inner parts of the disc. This result, which possibly implies the presence of giant planets, was made possible by the combination of a very clever method enabled by ESO's Very Large Telescope. Uncovering the disc ESO PR Photo 27a/08 Planet-forming Disc Planets could be home to other forms of life, so the study of exoplanets ranks very high in contemporary astronomy. More than 300 planets are already known to orbit stars other than the Sun, and these new worlds show an amazing diversity in their characteristics. But astronomers don't just look at systems where planets have already formed - they can also get great insights by studying the discs around young stars where planets may currently be forming. "This is like going 4.6 billion years back in time to watch how the planets of our own Solar System formed," says Klaus Pontoppidan from Caltech, who led the research. Pontoppidan and colleagues have analysed three young analogues of our Sun that are each surrounded by a disc of gas and dust from which planets could form. These three discs are just a few million years old and were known to have gaps or holes in them, indicating regions where the dust has been cleared and the possible presence of young planets. The new results not only confirm that gas is present in the gaps in the dust, but also enable astronomers to measure how the gas is distributed in the disc and how the disc is oriented. In regions where the dust appears to have been cleared out, molecular gas is still highly abundant. This can either mean that the dust has clumped together to form planetary embryos, or that a planet has already formed and is in the process of clearing the gas in the disc. For one of the stars, SR 21, a likely explanation is the presence of a massive giant planet orbiting at less than 3.5 times the distance

  2. Axial-flux modular permanent-magnet generator with a toroidal winding for wind-turbine applications

    SciTech Connect

    Muljadi, E.; Butterfield, C.P.; Wan, Y.H.

    1999-08-01

    Permanent-magnet (PM) generators have been used for wind turbines for many years. Many small wind-turbine manufacturers use direct-drive PM generators. For wind-turbine generators, the design philosophy must cover the following characteristics: low cost, light weight, low speed, high torque, and variable-speed generation. The generator is easy to manufacture and the design can be scaled up for a larger size without major retooling. A modular PM generator with axial flux direction was chosen. The permanent magnet used is NdFeB or ferrite magnet with flux guide to focus flux density in the air gap. Each unit module of the generator may consist of one, two, or more phases. Each generator can be expanded to two or more unit modules. Each unit module is built from simple modular poles. The stator winding is formed like a torus. Thus, the assembly process is simplified and the winding insertion in the slot is less tedious. The authors built a prototype of one unit module and performed preliminary tests in the laboratory. Follow-up tests will be conducted in the laboratory to improve the design.

  3. GAP Analysis Bulletin Number 15

    USGS Publications Warehouse

    Maxwell, Jill; Gergely, Kevin; Aycrigg, Jocelyn; Canonico, Gabrielle; Davidson, Anne; Coffey, Nicole

    2008-01-01

    The Mission of the Gap Analysis Program (GAP) is to promote conservation by providing broad geographic information on biological diversity to resource managers, planners, and policy makers who can use the information to make informed decisions. As part of the National Biological Information Infrastructure (NBII) ?a collaborative program to provide increased access to data and information on the nation?s biological resources--GAP data and analytical tools have been used in hundreds of applications: from basic research to comprehensive state wildlife plans; from educational projects in schools to ecoregional assessments of biodiversity. The challenge: keeping common species common means protecting them BEFORE they become threatened. To do this on a state or regional basis requires key information such as land cover descriptions, predicted distribution maps for native animals, and an assessment of the level of protection currently given to those plants and animals. GAP works cooperatively with Federal, state, and local natural resource professionals and academics to provide this kind of information. GAP activities focus on the creation of state and regional databases and maps that depict patterns of land management, land cover, and biodiversity. These data can be used to identify ?gaps? in conservation--instances where an animal or plant community is not adequately represented on the existing network of conservation lands. GAP is administered through the U.S. Geological Survey. Through building partnerships among disparate groups, GAP hopes to foster the kind of collaboration that is needed to address conservation issues on a broad scale. For more information, contact: John Mosesso National GAP Director 703-648-4079 Kevin Gergely National GAP Operations Manager 208-885-3565

  4. Method and apparatus for wind turbine air gap control

    DOEpatents

    Grant, James Jonathan; Bagepalli, Bharat Sampathkumaran; Jansen, Patrick Lee; DiMascio, Paul Stephen; Gadre, Aniruddha Dattatraya; Qu, Ronghai

    2007-02-20

    Methods and apparatus for assembling a wind turbine generator are provided. The wind turbine generator includes a core and a plurality of stator windings circumferentially spaced about a generator longitudinal axis, a rotor rotatable about the generator longitudinal axis wherein the rotor includes a plurality of magnetic elements coupled to a radially outer periphery of the rotor such that an airgap is defined between the stator windings and the magnetic elements and the plurality of magnetic elements including a radially inner periphery having a first diameter. The wind turbine generator also includes a bearing including a first member in rotatable engagement with a radially inner second member, the first member including a radially outer periphery, a diameter of the radially outer periphery of the first member being substantially equal to the first diameter, the rotor coupled to the stator through the bearing such that a substantially uniform airgap is maintained.

  5. Comparing different land surface heat flux estimates

    NASA Astrophysics Data System (ADS)

    Tretkoff, Ernie

    2011-04-01

    Land surface heat fluxes are an important component of Earth's energy and water cycle, and quantifying these fluxes can help scientists better understand climate change. These heat fluxes are affected by factors such as cloud cover, precipitation, surface radiation, air temperature, and humidity. Different methods are used to estimate monthly mean land surface heat flux. To determine how well these different methods agree with one other, Jiménez et al. present a detailed global intercomparison of 12 such products for the period 1993-1995. Some of these products are based on combining global satellite-based data and physical formulations, while others come from atmospheric reanalysis and land surface models. The authors found that although there were some differences among the products, the products all captured the seasonality of the heat fluxes as well as the expected spatial distributions related to major climatic regimes and geographical features. Furthermore, the products correlate well with each other in general, in part due to large seasonable variability and the fact that some of the products use the same forcing data. (Journal of Geophysical Research-Atmospheres, doi:10.1029/2010JD014545, 2011)

  6. Biosphere-Atmosphere Fluxes in Complex Terrain: Challenges and Opportunities

    NASA Astrophysics Data System (ADS)

    Novick, K. A.; Oishi, A. C.; Brantley, S. T.; Miniat, C. F.; Walker, J. T.; Vose, J. M.

    2014-12-01

    The occurrence of advection fluxes in complex terrain complicates the interpretation of eddy covariance data. As a result, flux monitoring networks are biased towards flat, homogeneous ecosystems. Here, we discuss both the challenges and opportunities presented by efforts to quantify ecosystem mass and energy fluxes in topographically complex sites. An approach for characterizing advection fluxes that relies on data collected from a single tower is described and applied as a case study in a flux monitoring site located in complex and heterogeneous terrain at the Coweeta Hydrologic Laboratory (North Carolina, USA). This site experiences significant nocturnal advection of mass and energy driven by downslope drainage flows, and significant daytime horizontal advection driven by the effects of anabatic and katabatic flow regimes on the flux footprint. While the advection regime at Coweeta may be especially challenging, the approach presented here is also relevant for flatter and more homogeneous sites where advection fluxes may be small but nonetheless non-negligible. Having addressed the methodological challenges presented by advection flows, we discuss novel opportunities associated with efforts to monitor ecosystem fluxes in complex sites. In particular, data from Coweeta are leveraged to highlight how topography buffers the site from mesoscale hydro-climatic variability via its influence on precipitation inputs, air and soil temperature, and vapor pressure deficit. We conclude by stressing that advances in flux measurement methodology now permit flux observation campaigns in complex and heterogeneous sites; furthermore, such data may be quite useful for exploring links between terrain, micro-meteorology, and physiological functioning.

  7. On comparison of modeled surface flux variations to aircraft observations.

    SciTech Connect

    Song, J.; Wesely, M. L.; Environmental Research; Northern Illinois Univ.

    2003-07-30

    Evaluation of models of air-surface exchange is facilitated by an accurate match of areas simulated with those seen by micrometeorological flux measurements. Here, spatial variations in fluxes estimated with the parameterized subgrid-scale surface (PASS) flux model were compared to flux variations seen aboard aircraft above the Walnut River Watershed (WRW) in Kansas. Despite interference by atmospheric eddies, the areas where the modeled sensible and latent heat fluxes were most highly correlated with the aircraft flux estimates were upwind of the flight segments. To assess whether applying a footprint function to the surface values would improve the model evaluation, a two-dimensional correlation distribution was used to identify the locations and relative importance of contributing modeled surface pixels upwind of each segment of the flight path. The agreement between modeled surface fluxes and aircraft measurements was improved when upwind fluxes were weighted with an optimized footprint parameter {var_phi}, which can be estimated from wind profiler data and surface eddy covariance. Variations of the flight-observed flux were consistently greater than those modeled at the surface, perhaps because of the smoothing effect of using 1 km pixels in the model. In addition, limited flight legs prevented sufficient filtering of the effects of atmospheric convection, possibly accounting for some of the more prominent changes in fluxes measured along the flight paths.

  8. Energy balance and non-turbulent fluxes

    NASA Astrophysics Data System (ADS)

    Moderow, Uta; Feigenwinter, Christian; Bernhofer, Christian

    2010-05-01

    Often, the sum of the turbulent fluxes of sensible heat and latent heat from eddy covariance (EC) measurements does not match the available energy (sum of net radiation, ground heat flux and storage changes). This is referred to as energy balance closure gap. The reported imbalances vary between 0% and 50% (Laubach 1996). In various publications, it has been shown that the uncertainty of the available energy itself does not explain the gap (Vogt et al. 1996; Moderow et al. 2009). Among other reasons, the underestimation is attributed to an underestimation of turbulent fluxes and undetected non-turbulent transport processes, i.e. advection (e.g. Foken et al. 2006). The imbalance is typically larger during nighttime than during daytime as the EC method fails to capture non-turbulent transports that can be significant during night (e.g. Aubinet 2008). Results for the budget of CO2 showed that including non-turbulent fluxes can change the budgets considerably. Hence, it is interesting to see how the budget of energy is changed. Here, the consequences of including advective fluxes of sensible heat and latent heat in the energy balance are explored with focus on nighttime conditions. Non-turbulent fluxes will be inspected critically regarding their plausibility. Following Bernhofer et al. (2003), a ratio similar to Bowen's ratio of the turbulent fluxes are defined for the non-turbulent fluxes and compared to each other. This might have implications for the partitioning of the available energy into sensible heat and latent heat. Data of the ADVEX-campaigns (Feigenwinter et al. 2008) of three different sites across Europe are used and selected periods are inspected. References Aubinet M (2008) Eddy covariance CO2-flux measurements in nocturnal conditions: An analysis of the problem. Ecol Appl 18: 1368-1378 Bernhofer C, Grünwald T, Schwiebus A, Vogt R (2003) Exploring the consequences of non-zero energy balance closure for total surface flux. In: Bernhofer C (ed

  9. Quantifying the drivers of ocean-atmosphere CO2 fluxes

    NASA Astrophysics Data System (ADS)

    Lauderdale, Jonathan M.; Dutkiewicz, Stephanie; Williams, Richard G.; Follows, Michael J.

    2016-07-01

    A mechanistic framework for quantitatively mapping the regional drivers of air-sea CO2 fluxes at a global scale is developed. The framework evaluates the interplay between (1) surface heat and freshwater fluxes that influence the potential saturated carbon concentration, which depends on changes in sea surface temperature, salinity and alkalinity, (2) a residual, disequilibrium flux influenced by upwelling and entrainment of remineralized carbon- and nutrient-rich waters from the ocean interior, as well as rapid subduction of surface waters, (3) carbon uptake and export by biological activity as both soft tissue and carbonate, and (4) the effect on surface carbon concentrations due to freshwater precipitation or evaporation. In a steady state simulation of a coarse-resolution ocean circulation and biogeochemistry model, the sum of the individually determined components is close to the known total flux of the simulation. The leading order balance, identified in different dynamical regimes, is between the CO2 fluxes driven by surface heat fluxes and a combination of biologically driven carbon uptake and disequilibrium-driven carbon outgassing. The framework is still able to reconstruct simulated fluxes when evaluated using monthly averaged data and takes a form that can be applied consistently in models of different complexity and observations of the ocean. In this way, the framework may reveal differences in the balance of drivers acting across an ensemble of climate model simulations or be applied to an analysis and interpretation of the observed, real-world air-sea flux of CO2.

  10. Air emissions from exposed contaminated sediments and dredged material

    SciTech Connect

    Valsaraj, K.T.; Ravikrishna, R.; Reible, D.D.; Thibodeaux, L.J.; Choy, B.; Price, C.B.; Brannon, J.M.; Myers, T.E.; Yost, S.

    1999-01-01

    The sediment-to-air fluxes of two polycyclic aromatic hydrocarbons (phenanthrene and pyrene) and a heterocyclic aromatic hydrocarbon (dibenzofuran) from a laboratory-contaminated sediment and those of three polycyclic aromatic hydrocarbons (naphthalene, phenanthrene, and pyrene) from three field sediments were investigated in experimental microcosms. The flux was dependent on the sediment moisture content, air-filled porosity, and the relative humidity of the air flowing over the sediment surface. The mathematical model predictions of flux from the laboratory-spiked sediment agreed with observed values. The fluxes of compounds with higher hydrophobicity were more air-side resistance controlled. Conspicuous differences were observed between the fluxes from the laboratory-spiked and two of the three field sediments. Two field sediments showed dramatic increases in mass-transfer resistances with increasing exposure time and had significant fractions of oil and grease. The proposed mathematical model was inadequate for predicting the flux from the latter field sediments. Sediment reworking enhanced the fluxes from the field sediments due to exposure of fresh solids to the air. Variations in flux from the lab-spiked sediment as a result of change in air relative humidity were due to differences in retardation of chemicals on a dry or wet surface sediment. High moisture in the air over the dry sediment increased the competition for sorption sites between water and contaminant and increased the contaminant flux.

  11. Nutrient fluxes through the Humber estuary

    NASA Astrophysics Data System (ADS)

    Sanders, R. J.; Jickells, T.; Malcolm, S.; Brown, J.; Kirkwood, D.; Reeve, A.; Taylor, J.; Horrobin, T.; Ashcroft, C.

    1997-05-01

    The Humber is a large and complex estuarine system on the east coast of England fed by several rivers. Fluxes of dissolved inorganic nutrients to, through and from this estuary over 1990-1993 are estimated from point flux calculations and property salinity plots. Internal nutrient sources and sinks are quantified. Fluxes of nutrients to the system are highly seasonal; fluxes of nitrate and phosphate are dominated by winter flows in the River Trent, the ammonium flux is dominated by the Rivers Aire and Don. The tidal Trent has a large internal source of ammonium, removes about 80% of its dissolved phosphate load and functions as a sink for nitrate. The tidal Ouse has large internal sources of nitrate, phosphate and ammonium, removes over 60% of its dissolved phosphate load, is an overall source of nitrate and a large sink for ammonium. The main estuary, below the confluence of the two tidal river systems, removes about 6% of the phosphate and 50% of the ammonium entering at the confluence or about 50% and 80%, respectively, if internal sources are taken into account. Nitrate behaves conservatively within the main estuary; thus any conversion of ammonium to nitrate is balanced by a nitrate sink of comparable size. Buffering mechanisms in the outer estuary may release phosphate in similar magnitudes to the direct dissolved export. The seasonality in nitrate flux to the system is preserved throughout the system. The seasonality of the phosphate flux to the system is almost eliminated in the lower part of the tidal rivers at the early part of the salinity gradient. This, combined with phosphate buffering, may render the offshore region nitrogen-limited under conditions suitable for algal growth. Overall the Humber system removes 85% of its dissolved phosphate load, and 4% of its dissolved inorganic nitrogen load.

  12. PAH and OPAH Flux during the Deepwater Horizon Incident.

    PubMed

    Tidwell, Lane G; Allan, Sarah E; O'Connell, Steven G; Hobbie, Kevin A; Smith, Brian W; Anderson, Kim A

    2016-07-19

    Passive sampling devices were used to measure air vapor and water dissolved phase concentrations of 33 polycyclic aromatic hydrocarbons (PAHs) and 22 oxygenated PAHs (OPAHs) at four Gulf of Mexico coastal sites prior to, during and after shoreline oiling from the Deepwater Horizon oil spill (DWH). Measurements were taken at each site over a 13 month period, and flux across the water-air boundary was determined. This is the first report of vapor phase and diffusive flux of both PAHs and OPAHs during the DWH. Vapor phase sum PAH and OPAH concentrations ranged between 6.6 and 210 ng/m(3) and 0.02 and 34 ng/m(3) respectively. PAH and OPAH concentrations in air exhibited different spatial and temporal trends than in water, and air-water flux of 13 individual PAHs was shown to be at least partially influenced by the DWH incident. The largest PAH volatilizations occurred at the sites in Alabama and Mississippi at nominal rates of 56 000 and 42 000 ng/m(2) day(-1) in the summer. Naphthalene was the PAH with the highest observed volatilization rate of 52 000 ng/m(2) day(-1) in June 2010. This work represents additional evidence of the DWH incident contributing to air contamination, and provides one of the first quantitative air-water chemical flux determinations with passive sampling technology. PMID:27391856

  13. LOW-MASS PLANETS IN PROTOPLANETARY DISKS WITH NET VERTICAL MAGNETIC FIELDS: THE PLANETARY WAKE AND GAP OPENING

    SciTech Connect

    Zhu Zhaohuan; Stone, James M.; Rafikov, Roman R. E-mail: jstone@astro.princeton.edu

    2013-05-10

    Some regions in protoplanetary disks are turbulent, while some regions are quiescent (e.g. the dead zone). In order to study how planets open gaps in both inviscid hydrodynamic disk (e.g. the dead zone) and the disk subject to magnetorotational instability (MRI), we carried out both shearing box two-dimensional inviscid hydrodynamical simulations and three-dimensional unstratified magnetohydrodynamical (MHD) simulations (having net vertical magnetic fields) with a planet at the box center. We found that, due to the nonlinear wave steepening, even a low mass planet can open gaps in both cases, in contradiction to the ''thermal criterion'' for gap opening. In order to understand if we can represent the MRI turbulent stress with the viscous {alpha} prescription for studying gap opening, we compare gap properties in MRI-turbulent disks to those in viscous HD disks having the same stress, and found that the same mass planet opens a significantly deeper and wider gap in net vertical flux MHD disks than in viscous HD disks. This difference arises due to the efficient magnetic field transport into the gap region in MRI disks, leading to a larger effective {alpha} within the gap. Thus, across the gap, the Maxwell stress profile is smoother than the gap density profile, and a deeper gap is needed for the Maxwell stress gradient to balance the planetary torque density. Comparison with previous results from net toroidal flux/zero flux MHD simulations indicates that the magnetic field geometry plays an important role in the gap opening process. We also found that long-lived density features (termed zonal flows) produced by the MRI can affect planet migration. Overall, our results suggest that gaps can be commonly produced by low mass planets in realistic protoplanetary disks, and caution the use of a constant {alpha}-viscosity to model gaps in protoplanetary disks.

  14. Pneumatic gap sensor and method

    DOEpatents

    Bagdal, K.T.; King, E.L.; Follstaedt, D.W.

    1992-03-03

    An apparatus and method for monitoring and maintaining a predetermined width in the gap between a casting nozzle and a casting wheel, wherein the gap is monitored by means of at least one pneumatic gap sensor. The pneumatic gap sensor is mounted on the casting nozzle in proximity to the casting surface and is connected by means of a tube to a regulator and a transducer. The regulator provides a flow of gas through a restictor to the pneumatic gap sensor, and the transducer translates the changes in the gas pressure caused by the proximity of the casting wheel to the pneumatic gap sensor outlet into a signal intelligible to a control device. The relative positions of the casting nozzle and casting wheel can thereby be selectively adjusted to continually maintain a predetermined distance between their adjacent surfaces. The apparatus and method enables accurate monitoring of the actual casting gap in a simple and reliable manner resistant to the extreme temperatures and otherwise hostile casting environment. 6 figs.

  15. Pneumatic gap sensor and method

    DOEpatents

    Bagdal, Karl T.; King, Edward L.; Follstaedt, Donald W.

    1992-01-01

    An apparatus and method for monitoring and maintaining a predetermined width in the gap between a casting nozzle and a casting wheel, wherein the gap is monitored by means of at least one pneumatic gap sensor. The pneumatic gap sensor is mounted on the casting nozzle in proximity to the casting surface and is connected by means of a tube to a regulator and a transducer. The regulator provides a flow of gas through a restictor to the pneumatic gap sensor, and the transducer translates the changes in the gas pressure caused by the proximity of the casting wheel to the pneumatic gap sensor outlet into a signal intelligible to a control device. The relative positions of the casting nozzle and casting wheel can thereby be selectively adjusted to continually maintain a predetermined distance between their adjacent surfaces. The apparatus and method enables accurate monitoring of the actual casting gap in a simple and reliable manner resistant to the extreme temperatures and otherwise hostile casting environment.

  16. Ion Engine Grid Gap Measurements

    NASA Technical Reports Server (NTRS)

    Soulas, Gerge C.; Frandina, Michael M.

    2004-01-01

    A simple technique for measuring the grid gap of an ion engine s ion optics during startup and steady-state operation was demonstrated with beam extraction. The grid gap at the center of the ion optics assembly was measured with a long distance microscope that was focused onto an alumina pin that protruded through the center accelerator grid aperture and was mechanically attached to the screen grid. This measurement technique was successfully applied to a 30 cm titanium ion optics assembly mounted onto an NSTAR engineering model ion engine. The grid gap and each grid s movement during startup from room temperature to both full and low power were measured. The grid gaps with and without beam extraction were found to be significantly different. The grid gaps at the ion optics center were both significantly smaller than the cold grid gap and different at the two power levels examined. To avoid issues associated with a small grid gap during thruster startup with titanium ion optics, a simple method was to operate the thruster initially without beam extraction to heat the ion optics. Another possible method is to apply high voltage to the grids prior to igniting the discharge because power deposition to the grids from the plasma is lower with beam extraction than without. Further testing would be required to confirm this approach.

  17. Observational Studies of Parameters Influencing Air-sea Gas Exchange

    NASA Astrophysics Data System (ADS)

    Schimpf, U.; Frew, N. M.; Bock, E. J.; Hara, T.; Garbe, C. S.; Jaehne, B.

    A physically-based modeling of the air-sea gas transfer that can be used to predict the gas transfer rates with sufficient accuracy as a function of micrometeorological parameters is still lacking. State of the art are still simple gas transfer rate/wind speed relationships. Previous measurements from Coastal Ocean Experiment in the Atlantic revealed positive correlations between mean square slope, near surface turbulent dis- sipation, and wind stress. It also demonstrated a strong negative correlation between mean square slope and the fluorescence of surface-enriched colored dissolved organic matter. Using heat as a proxy tracer for gases the exchange process at the air/water interface and the micro turbulence at the water surface can be investigated. The anal- ysis of infrared image sequences allow the determination of the net heat flux at the ocean surface, the temperature gradient across the air/sea interface and thus the heat transfer velocity and gas transfer velocity respectively. Laboratory studies were carried out in the new Heidelberg wind-wave facility AELOTRON. Direct measurements of the Schmidt number exponent were done in conjunction with classical mass balance methods to estimate the transfer velocity. The laboratory results allowed to validate the basic assumptions of the so called controlled flux technique by applying differ- ent tracers for the gas exchange in a large Schmidt number regime. Thus a modeling of the Schmidt number exponent is able to fill the gap between laboratory and field measurements field. Both, the results from the laboratory and the field measurements should be able to give a further understanding of the mechanisms controlling the trans- port processes across the aqueous boundary layer and to relate the forcing functions to parameters measured by remote sensing.

  18. Implications of mercury interactions with band-gap semiconductor oxides

    SciTech Connect

    Granite, E.J.; King, W.P.; Stanko, D.C.; Pennline, H.W.

    2008-09-01

    Titanium dioxide is a well-known photooxidation catalyst. It will oxidize mercury in the presence of ultraviolet light from the sun and oxygen and/or moisture to form mercuric oxide. Several companies manufacture self-cleaning windows. These windows have a transparent coating of titanium dioxide. The titanium dioxide is capable of destroying organic contaminants in air in the presence of ultraviolet light from the sun, thereby keeping the windows clean. The commercially available self-cleaning windows were used to sequester mercury from oxygen–nitrogen mixtures. Samples of the self-cleaning glass were placed into specially designed photo-reactors in order to study the removal of elemental mercury from oxygen–nitrogen mixtures resembling air. The possibility of removing mercury from ambient air with a self-cleaning glass apparatus is examined. The intensity of 365-nm ultraviolet light was similar to the natural intensity from sunlight in the Pittsburgh region. Passive removal of mercury from the air may represent an option in lieu of, or in addition to, point source clean-up at combustion facilities. There are several common band-gap semiconductor oxide photocatalysts. Sunlight (both the ultraviolet and visible light components) and band-gap semiconductor particles may have a small impact on the global cycle of mercury in the environment. The potential environmental consequences of mercury interactions with band-gap semiconductor oxides are discussed. Heterogeneous photooxidation might impact the global transport of elemental mercury emanating from flue gases.

  19. Superradiance and flux conservation

    NASA Astrophysics Data System (ADS)

    Boonserm, Petarpa; Ngampitipan, Tritos; Visser, Matt

    2014-09-01

    The theoretical foundations of the phenomenon known as superradiance still continue to attract considerable attention. Despite many valiant attempts at pedagogically clear presentations, the effect nevertheless still continues to generate some significant confusion. Part of the confusion arises from the fact that superradiance in a quantum field theory context is not the same as superradiance (superfluorescence) in some condensed matter contexts; part of the confusion arises from traditional but sometimes awkward normalization conventions, and part is due to sometimes unnecessary confusion between fluxes and probabilities. We shall argue that the key point underlying the effect is flux conservation (and, in the presence of dissipation, a controlled amount of flux nonconservation), and that attempting to phrase things in terms of reflection and transmission probabilities only works in the absence of superradiance. To help clarify the situation we present a simple exactly solvable toy model exhibiting both superradiance and damping.

  20. Flux amplification in SSPX

    NASA Astrophysics Data System (ADS)

    Lodestro, Lynda; Hooper, E. B.; Jayakumar, R. J.; Pearlstein, L. D.; Wood, R. D.; McLean, H. S.

    2007-11-01

    Flux amplification---the ratio of poloidal flux enclosed between the magnetic and geometric axes to that between the separatrix and the geometric axis---is a key measure of efficiency for edge-current-driven spheromaks. With the new, modular capacitor bank, permitting flexible programming of the gun current, studies of flux amplification under various drive scenarios can be performed. Analysis of recent results of pulsed operation with the new bank finds an efficiency ˜ 0.2, in selected shots, of the conversion of gun energy to confined magnetic energy during the pulses, and suggests a route toward sustained efficiency at 0.2. Results of experiments, a model calculation of field build-up, and NIMROD simulations exploring this newly suggested scenario will be presented.

  1. Effect of cerium addition on casting/chill interfacial heat flux and casting surface profile during solidification of Al-14%Si alloy

    NASA Astrophysics Data System (ADS)

    Vijeesh, V.; Prabhu, K. N.

    2016-03-01

    In the present investigation, Al-14 wt. % Si alloy was solidified against copper, brass and cast iron chills, to study the effect of Ce melt treatment on casting/chill interfacial heat flux transients and casting surface profile. The heat flux across the casting/chill interface was estimated using inverse modelling technique. On addition of 1.5% Ce, the peak heat flux increased by about 38%, 42% and 43% for copper, brass and cast iron chills respectively. The effect of Ce addition on casting surface texture was analyzed using a surface profilometer. The surface profile of the casting and the chill surfaces clearly indicated the formation of an air gap at the periphery of the casting. The arithmetic average value of the profile departure from the mean line (Ra) and arithmetical mean of the absolute departures of the waviness profile from the centre line (Wa) were found to decrease on Ce addition. The interfacial gap width formed for the unmodified and Ce treated casting surfaces at the periphery were found to be about 35µm and 13µm respectively. The enhancement in heat transfer on addition of Ce addition was attributed to the lowering of the surface tension of the liquid melt. The gap width at the interface was used to determine the variation of heat transfer coefficient (HTC) across the chill surface after the formation of stable solid shell. It was found that the HTC decreased along the radial direction for copper and brass chills and increased along radial direction for cast iron chills.

  2. Optical heat flux gauge

    DOEpatents

    Noel, Bruce W.; Borella, Henry M.; Cates, Michael R.; Turley, W. Dale; MaCarthur, Charles D.; Cala, Gregory C.

    1991-01-01

    A heat flux gauge comprising first and second thermographic phosphor layers separated by a layer of a thermal insulator. The gauge may be mounted on a surface with the first thermographic phosphor in contact with the surface. A light source is directed at the gauge, causing the phosphors to luminesce. The luminescence produced by the phosphors is collected and its spectra analyzed in order to determine the heat flux on the surface. First and second phosphor layers must be different materials to assure that the spectral lines collected will be distinguishable.

  3. Optical heat flux gauge

    DOEpatents

    Noel, Bruce W.; Borella, Henry M.; Cates, Michael R.; Turley, W. Dale; MacArthur, Charles D.; Cala, Gregory C.

    1991-01-01

    A heat flux gauge comprising first and second thermographic phosphor layers separated by a layer of a thermal insulator wherein each thermographic layer comprises a plurality of respective thermographic phosphors. The gauge may be mounted on a surface with the first thermographic phosphor in contact with the surface. A light source is directed at the gauge, causing the phosphors to luminesce. The luminescence produced by the phosphors is collected and its spectra analyzed in order to determine the heat flux on the surface. First and second phosphor layers must be different materials to assure that the spectral lines collected will be distinguishable.

  4. Optical heat flux gauge

    DOEpatents

    Noel, Bruce W.; Borella, Henry M.; Cates, Michael R.; Turley, W. Dale; MacArthur, Charles D.; Cala, Gregory C.

    1991-01-01

    A heat flux gauge comprising first and second thermographic phosphor layers separated by a layer of a thermal insulator, wherein each thermographic layer comprises a plurality of respective thermographic sensors in a juxtaposed relationship with respect to each other. The gauge may be mounted on a surface with the first thermographic phosphor in contact with the surface. A light source is directed at the gauge, causing the phosphors to luminesce. The luminescence produced by the phosphors is collected and its spectra analyzed in order to determine the heat flux on the surface. First and second phosphor layers must be different materials to assure that the spectral lines collected will be distinguishable.

  5. Forest canopy gap distributions in the southern Peruvian Amazon.

    PubMed

    Asner, Gregory P; Kellner, James R; Kennedy-Bowdoin, Ty; Knapp, David E; Anderson, Christopher; Martin, Roberta E

    2013-01-01

    Canopy gaps express the time-integrated effects of tree failure and mortality as well as regrowth and succession in tropical forests. Quantifying the size and spatial distribution of canopy gaps is requisite to modeling forest functional processes ranging from carbon fluxes to species interactions and biological diversity. Using high-resolution airborne Light Detection and Ranging (LiDAR), we mapped and analyzed 5,877,937 static canopy gaps throughout 125,581 ha of lowland Amazonian forest in Peru. Our LiDAR sampling covered a wide range of forest physiognomies across contrasting geologic and topographic conditions, and on depositional floodplain and erosional terra firme substrates. We used the scaling exponent of the Zeta distribution (λ) as a metric to quantify and compare the negative relationship between canopy gap frequency and size across sites. Despite variable canopy height and forest type, values of λ were highly conservative (λ mean  = 1.83, s  = 0.09), and little variation was observed regionally among geologic substrates and forest types, or at the landscape level comparing depositional-floodplain and erosional terra firme landscapes. λ-values less than 2.0 indicate that these forests are subjected to large gaps that reset carbon stocks when they occur. Consistency of λ-values strongly suggests similarity in the mechanisms of canopy failure across a diverse array of lowland forests in southwestern Amazonia. PMID:23613748

  6. Forest Canopy Gap Distributions in the Southern Peruvian Amazon

    PubMed Central

    Asner, Gregory P.; Kellner, James R.; Kennedy-Bowdoin, Ty; Knapp, David E.; Anderson, Christopher; Martin, Roberta E.

    2013-01-01

    Canopy gaps express the time-integrated effects of tree failure and mortality as well as regrowth and succession in tropical forests. Quantifying the size and spatial distribution of canopy gaps is requisite to modeling forest functional processes ranging from carbon fluxes to species interactions and biological diversity. Using high-resolution airborne Light Detection and Ranging (LiDAR), we mapped and analyzed 5,877,937 static canopy gaps throughout 125,581 ha of lowland Amazonian forest in Peru. Our LiDAR sampling covered a wide range of forest physiognomies across contrasting geologic and topographic conditions, and on depositional floodplain and erosional terra firme substrates. We used the scaling exponent of the Zeta distribution (λ) as a metric to quantify and compare the negative relationship between canopy gap frequency and size across sites. Despite variable canopy height and forest type, values of λ were highly conservative (λ mean  = 1.83, s  = 0.09), and little variation was observed regionally among geologic substrates and forest types, or at the landscape level comparing depositional-floodplain and erosional terra firme landscapes. λ-values less than 2.0 indicate that these forests are subjected to large gaps that reset carbon stocks when they occur. Consistency of λ-values strongly suggests similarity in the mechanisms of canopy failure across a diverse array of lowland forests in southwestern Amazonia. PMID:23613748

  7. Intercomparison results for FIFE flux aircraft

    NASA Technical Reports Server (NTRS)

    Macpherson, J. I.; Grossman, R. L.; Kelly, R. D.

    1992-01-01

    Three atmospheric research aircraft were used to explore the atmospheric boundary layer during FIFE: the National Research Council of Canada Twin Otter, the National Center for Atmospheric Research (NCAR) King Air, and the University of Wyoming King Air. The aircraft were used to measure the mean and turbulent structure of the boundary layer and its variation with height, time, and space. These measurements are important to FIFE because they are being used to scale up point surface observations to landscape scales and because they can be used to relate satellite radiance measurements to boundary layer processes. Because the aircraft were used in coordinated flight patterns to investigate changes within and between intensive field campaigns, wing-to-wing intercomparisons were made so that measurements from one aircraft could be related to another. Intercomparisons were flown on 4 days in 1987 and 3 days in 1989. The eddy correlation measurements of the mixed layer fluxes of moisture and sensible heat were of particular interest to FIFE. Sensible heat fluxes agreed within 15 W/sq m and moisture fluxes agreed within 21 W/sq m. Mean wind component differences were within 1.0 m/s, air temperature within 0.3 C, and mixing ratio within 2 g/kg. Standard deviations showed similar good agreement, with mean differences generally less than 0.1 m/s for the wind components and 0.03 C for potential temperature. Intercomparisons between the NCAR King Air and the Twin Otter showed better agreement in 1989 than in 1987. Overall, the results suggest that data from the FIFE boundary layer aircraft will need little correction to account for instrument biases and spurious fluctuations.

  8. Regional airborne flux measurements in Europe

    NASA Astrophysics Data System (ADS)

    Gioli, B.; Miglietta, F.; Vaccari, F. P.; Zaldei, A.; Hutjes, R. W. A.

    2003-04-01

    The problem of identifying the spatial and temporal distribution of sources and sinks of atmospheric CO2 is the subject of considerable scientific and political debate. Even if it is now possible to estimate within reasonable accuracy the sink strength of European forests at the local scale, difficulties still exist in determining the partitioning of the sinks at the global and regional scales. The aim of the EU-project RECAB (Regional Assessment of the Carbon Balance in Europe) that is coordinated by Alterra, Wageningen (NL), is to bridge the gap between local scale flux measurements and continental scale inversion models by a generic modelling effort and measurement program, focussing on a limited number of selected regions in Europe for which previous measurements exists. This required the establishment of a European facility for airborne measurement of surface fluxes of CO2 at very low altitude, and a research aircraft capable of performing airborne eddy covariance measurements has been acquired by this project and used on several occasions at the different RECAB sites. The aircraft is the italian Sky Arrows ERA (Environmental Research Aircraft) equipped with the NOAA/ARA Mobile Flux Platform (MFP), and a commercial open-path infrared gas analyser. Airborne eddy covariance measurements were made from June 2001 onwards in Southern Spain near Valencia (June and December 2001), in Central Germany near Jena (July 2001), in Sweden near Uppsala (August 2001), in The Netherlands near Wageningen (January and July 2002) and in Italy near Rome (June 2002). Flux towers were present at each site to provide a validation of airborne eddy covariance measurements. This contribution reports some validation results based on the comparison between airborne and ground based flux measurements and some regional scale results for different locations and different seasons, in a wide range of meteorological and ecological settings.

  9. Optimizing laboratory-based radon flux measurements for sediments.

    PubMed

    Chanyotha, Supitcha; Kranrod, Chutima; Kritsananuwat, Rawiwan; Lane-Smith, Derek; Burnett, William C

    2016-07-01

    Radon flux via diffusion from sediments and other materials may be determined in the laboratory by circulating air through the sample and a radon detector in a closed loop. However, this approach is complicated by the necessity of having to determine the total air volume in the system and accounting for any small air leaks that can arise if using extended measurement periods. We designed a simple open-loop configuration that includes a measured mass of wet sediment and water inside a gas-tight reaction flask connected to a drying system and a radon-in-air analyzer. Ambient air flows through two charcoal columns before entering the reaction vessel to eliminate incoming radon. After traveling through the reaction flask, the air passes the drier and the radon analyzer and is then vented. After some time, the radon activity will reach a steady state depending upon the airflow rate. With this approach, the radon flux via diffusion is simply the product of the steady-state radon activity (Bq/m(3)) multiplied by the airflow rate (mL/min). We demonstrated that this setup could produce good results for materials that produce relatively high radon fluxes. We also show that a modified closed system approach, including radon removal of the incoming air by charcoal filtration in a bypass, can produce very good results including samples with very low emission rates. PMID:27064564

  10. Eight electrode optical readout gap

    DOEpatents

    Boettcher, Gordon E.; Crain, Robert W.

    1985-01-01

    A protective device for a plurality of electrical circuits includes a pluity of isolated electrodes forming a gap with a common electrode. An output signal, electrically isolated from the circuits being monitored, is obtained by a photosensor viewing the discharge gap through an optical window. Radioactive stabilization of discharge characteristics is provided for slowly changing voltages and carbon tipped dynamic starters provide desirable discharge characteristics for rapidly varying voltages. A hydrogen permeation barrier is provided on external surfaces of the device.

  11. Pneumatic gap sensor and method

    SciTech Connect

    Bagdal, K.T.; King, E.L.; Follstaedt, D.W.

    1992-03-03

    This patent describes in a casting system which including an apparatus for monitoring the gap between a casting nozzle and a casting surface of a substrate during casting of molten material, wherein the molten material is provided through a channel of the casting nozzle for casting onto the casting surface of the substrate for solidification. It comprises: a pneumatic gap mounted at least partially within a cavity in the casting nozzle adjacent the channel and having a sensor face located within the gap between the nozzle and the casting surface of the substrate, means for supply gas under predetermined pressure to the inlet orifice; and means for measuring the pressure of the gas within the sensor chamber during casting procedures, whereby relative changes in the gap can be determined by corresponding changes in the measured pressure. This patent also describes a method for monitoring the gap between a casting nozzle and a casting surface of a substrate for continuous casting of molten material. It comprises: providing a casting nozzle with a channel for directing the flow of molten material, locating the nozzle and the casting surface is proximity with one another and having a predetermined gap there-between, and dressing the sensor face to correspond in conformation to the casting surface and to adjust the predetermined distance as desired; providing a molten material to the nozzle for casting onto and casting surface; supplying gas at a predetermined pressure to the inlet orifice of the sensor during casting procedures.

  12. Measurement of reflection phase using thick-gap Fabry-Perot etalon.

    PubMed

    Yung, Tsz Kit; Gao, Wensheng; Leung, Ho Ming; Zhao, Qiuling; Wang, Xia; Tam, Wing Yim

    2016-09-10

    We report measurement of the reflection phase of a dielectric (glass)/titanium (Ti) surface in the visible wavelength using a thick-gap Fabry-Perot (FP) interferometry technique. Using a two-beam interference model for the reflection peaks and troughs of the FP etalon, we obtain the air-gap spacing of the etalon and, more importantly, the reflection phase of the etalon substrate. We find systematic dependence of the as-measured reflection phase on the air-gap spacing due to the numerical aperture effect of the measuring objective. However, the relative reflection phase of Ti with respect to glass is independent of the air-gap spacing. As a demonstration of our approach in the optical characterization of small metamaterial samples, we also measure the reflection phase of a micron-sized 2D Au sawtooth nanoarray. The experiment is in good agreement with the model simulation. PMID:27661366

  13. Measurement of reflection phase using thick-gap Fabry-Perot etalon.

    PubMed

    Yung, Tsz Kit; Gao, Wensheng; Leung, Ho Ming; Zhao, Qiuling; Wang, Xia; Tam, Wing Yim

    2016-09-10

    We report measurement of the reflection phase of a dielectric (glass)/titanium (Ti) surface in the visible wavelength using a thick-gap Fabry-Perot (FP) interferometry technique. Using a two-beam interference model for the reflection peaks and troughs of the FP etalon, we obtain the air-gap spacing of the etalon and, more importantly, the reflection phase of the etalon substrate. We find systematic dependence of the as-measured reflection phase on the air-gap spacing due to the numerical aperture effect of the measuring objective. However, the relative reflection phase of Ti with respect to glass is independent of the air-gap spacing. As a demonstration of our approach in the optical characterization of small metamaterial samples, we also measure the reflection phase of a micron-sized 2D Au sawtooth nanoarray. The experiment is in good agreement with the model simulation.

  14. The number and size of subhalo-induced gaps in stellar streams

    NASA Astrophysics Data System (ADS)

    Erkal, Denis; Belokurov, Vasily; Bovy, Jo; Sanders, Jason L.

    2016-11-01

    Ample observational capabilities exist today to detect the small density perturbations that low-mass dark matter subhaloes impart on stellar streams from disrupting Galactic satellites. In anticipation of these observations, we investigate the expected number and size of gaps by combining an analytic prescription for gap evolution on circular orbits with the flux of subhaloes near the stream. We explore the distribution of gap sizes and depths for a typical cold stream around the Milky Way and find that for a given stream age and gap depth, each subhalo mass produces a characteristic gap size. For a stream with an age of a few Gyr, orbiting at a distance of 10-20 kpc from the Galactic centre, even modest subhaloes with a mass of 106-107 M⊙ produce gaps with sizes that are of the order of several degrees. We consider the number and distribution of gap sizes created by subhaloes with masses 105-109 M⊙, accounting for the expected depletion of subhaloes by the Milky Way disc, and present predictions for six cold streams around the Milky Way. For Pal 5, we forecast 0.7 gaps with a density depletion of at least 25 per cent and a typical gap size of 8°. Thus, there appears to be no tension between the recent non-detection of density depletions in the Pal 5 tidal tails and ΛCDM expectations. These predictions can be used to guide the scale of future gap searches.

  15. The number and size of subhalo-induced gaps in stellar streams

    NASA Astrophysics Data System (ADS)

    Erkal, Denis; Belokurov, Vasily; Bovy, Jo; Sanders, Jason L.

    2016-08-01

    Ample observational capabilities exist today to detect the small density perturbations that low-mass dark matter subhaloes impart on stellar streams from disrupting Galactic satellites. In anticipation of these observations, we investigate the expected number and size of gaps by combining an analytic prescription for gap evolution on circular orbits with the flux of subhaloes near the stream. We explore the distribution of gap sizes and depths for a typical cold stream around the Milky Way and find that for a given stream age and gap depth, each subhalo mass produces a characteristic gap size. For a stream with an age of a few Gyr, orbiting at a distance of 10-20 kpc from the Galactic center, even modest subhaloes with a mass of 106 - 107M⊙ produce gaps with sizes that are on the order of several degrees. We consider the number and distribution of gap sizes created by subhaloes with masses 105 - 109M⊙, accounting for the expected depletion of subhaloes by the Milky Way disk, and present predictions for six cold streams around the Milky Way. For Pal 5, we forecast 0.7 gaps with a density depletion of at least 25% and a typical gap size of 8°. Thus, there appears to be no tension between the recent non-detection of density depletions in the Pal 5 tidal tails and ΛCDM expectations. These predictions can be used to guide the scale of future gap searches.

  16. Air Pollution and Control Legislation in India

    NASA Astrophysics Data System (ADS)

    P Bhave, Prashant; Kulkarni, Nikhil

    2015-09-01

    Air pollution in urban areas arises from multiple sources, which may vary with location and developmental activities. Anthropogenic activities as rampant industrialization, exploitation and over consumption of natural resources, ever growing population size are major contributors of air pollution. The presented review is an effort to discuss various aspects of air pollution and control legislation in India emphasizing on the history, present scenario, international treaties, gaps and drawbacks. The review also presents legislative controls with judicial response to certain landmark judgments related to air pollution. The down sides related to enforcement mechanism for the effective implementation of environmental laws for air pollution control have been highlighted.

  17. A title-gap flow model for use in aerodynamic loads assessment of space shuttle thermal protection system: Parallel gap faces

    NASA Technical Reports Server (NTRS)

    Dwoyer, D. L.; Newman, P. A.; Thames, F. C.; Melson, N. D.

    1981-01-01

    The problem of predicting aerodynamic loads on the insulating tiles of the space shuttle thermal protection system (TPS) is discussed and seen to require a method for predicting pressure and mass flux in the gaps between tiles. A mathematical model of the tile-gap flow is developed, based upon a slow viscous (Stokes) flow analysis, and is verified against experimental data. The tile-gap pressure field is derived from a solution of the two-dimensional Laplace equation; the mass-flux vector is then calculated from the pressure gradient. The means for incorporating this model into a lumped-parameter network analogy for porous-media flow is given. The means for incorporating this model into a lumped-parameter network analogy for porous-media flow is given. The flow model shows tile-gap mass flux to be very sensitive to the gap width indicating a need for coupling the TPS flow and tile displacement calculation. Analytical and experimental work to improve TPS flow predictions and a possible shuttle TPS hardware modification are recommended.

  18. High flux heat exchanger

    NASA Astrophysics Data System (ADS)

    Flynn, Edward M.; Mackowski, Michael J.

    1993-01-01

    This interim report documents the results of the first two phases of a four-phase program to develop a high flux heat exchanger for cooling future high performance aircraft electronics. Phase 1 defines future needs for high flux heat removal in advanced military electronics systems. The results are sorted by broad application categories: (1) commercial digital systems, (2) military data processors, (3) power processors, and (4) radar and optical systems. For applications expected to be fielded in five to ten years, the outlook is for steady state flux levels of 30-50 W/sq cm for digital processors and several hundred W/sq cm for power control applications. In Phase 1, a trade study was conducted on emerging cooling technologies which could remove a steady state chip heat flux of 100 W/sq cm while holding chip junction temperature to 90 C. Constraints imposed on heat exchanger design, in order to reflect operation in a fighter aircraft environment, included a practical lower limit on coolant supply temperature, the preference for a nontoxic, nonflammable, and nonfreezing coolant, the need to minimize weight and volume, and operation in an accelerating environment. The trade study recommended the Compact High Intensity Cooler (CHIC) for design, fabrication, and test in the final two phases of this program.

  19. Radiative Flux Analysis

    DOE Data Explorer

    Long, Chuck [NOAA

    2008-05-14

    The Radiative Flux Analysis is a technique for using surface broadband radiation measurements for detecting periods of clear (i.e. cloudless) skies, and using the detected clear-sky data to fit functions which are then used to produce continuous clear-sky estimates. The clear-sky estimates and measurements are then used in various ways to infer cloud macrophysical properties.

  20. Incident meteoroid flux density

    NASA Technical Reports Server (NTRS)

    Badadjanov, P. B.; Bibarsov, R. SH.; Getman, V. S.; Kolmakov, V. M.

    1987-01-01

    Complex photographic and radar meteor observations were carried out. Using the available observational data, the density of incident flux of meteoroids was estimated over a wide mass range of 0.001 to 100 g. To avoid the influence of apparatus selectivity a special technique was applied. The main characteristics of this technique are given and discussed.