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1

Heat Flux Determination From Measured Heating Rates Using Thermographic Phosphors  

Microsoft Academic Search

A new method for measuring the heating rate (defined as the time rate of change of temperature) and estimating heat flux from the heating rate is proposed. The example problem involves analytic heat conduction in a one-dimensional slab, where the measure- ment location of temperature or heating rate coincides with the location of the estimated heat flux. The new method

D. G. Walker

2005-01-01

2

Isoprene emission rates and fluxes measured above a Mediterranean oak ( Quercus pubescens) forest  

NASA Astrophysics Data System (ADS)

The present work, carried out as part of the European fiEld experimentS to COnstrain Models of atmospheric Pollution and Transport of Emissions project (ESCOMPTE), brings a new contribution to the inventory of the main natural hydrocarbons sources that are liable to participate in the production of ozone. The measurement campaign was conducted in Montmeyan, a site close to Marseilles (France), with the aim of quantifying the terpenic emission pattern and the behaviour of Quercus pubescens, an important Mediterranean tree species. Biogenic emissions by Q. pubescens were determined by the enclosure of an intact branch of this tree in a Teflon cuvette. The total monoterpenic emission rates thus recorded were found to reach maximum values ranged between 40 and 350 ?g g Dry Weight-1 h -1. Emissions were correlated strongly with leaf temperature and Photosynthetic Active Radiation (PAR). The fluxes were also determined by extrapolating the results of the enclosure method and by using aerodynamic gradient method. They reach around 73 mg m -2 h -1 with the first method and 55 mg m -2 h -1 with the second one. The obtained values fit with a maximal ratio of 2.

Simon, V.; Dumergues, L.; Bouchou, P.; Torres, L.; Lopez, A.

2005-03-01

3

Heat flux measurements  

NASA Technical Reports Server (NTRS)

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.

Liebert, Curt H.; Weikle, Donald H.

1989-01-01

4

Heat flux measurements  

Microsoft Academic Search

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

Curt H. Liebert; Donald H. Weikle

1989-01-01

5

Measurement of pulsed neutron flux and dose equivalent rate for a 30MeV electron linac  

Microsoft Academic Search

In this paper an active indium detector is suggested to measure the pulsed neutrons around an electron linac. It can be expected to have a correct dose response of the detector in the short pulsed neutron field, high discrimination ability between neutrons and ..gamma..-rays and against electromagnetic disturbances. This detector was used to measure the distribution of neutron flux and

Li Jian-ping; Wu Jing-min; Liu Shu-don; Tang E-sheng

1988-01-01

6

Measuring surface fluxes in CAPE  

NASA Technical Reports Server (NTRS)

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.

Kanemasu, E. T.; D-Shah, T.; Nie, Dalin

1992-01-01

7

Assessing Photosynthetic Energy Fluxes Within Microbial Communities Using Continuous Ship-Based Fast Repetition Rate (FRR) Fluorescence Measurements.  

NASA Astrophysics Data System (ADS)

Microbial life in the ocean is sustained by photosynthetically-derived energy at a power level of about 5*1014 W. Assuming photosynthetic efficiency of about 20%, this mechanism consumes less than 10% of photosynthetically-available radiation (PAR) incident on the ocean surface. Life in the ocean operates under condition of excess energy, where factors such as nutrients/trace metals availability or prevalence of nitrogen fixation limit photosynthetic light utilization. To investigate these factors we have performed fast repetition rate (FRR) fluorescence measurements, continuously, over a period of one year, along the cruise track of R/V Kilo Moana. We have identified photosynthetic signatures of Trichodesmium blooms during two cruises in 2007 and 2008, and we have used these signatures to infer the presence of Trichodesmium along the cruise track. Most surface enhancements in photosynthetic rates and the chlorophyll biomass were observed in peripheral areas between cyclonic and anticyclonic eddies. It appears that local shear zones in these areas induce small-scale vertical mixing capable of supporting near-surface blooms. Our data indicate that the gradients in the sea surface height, rather than local minima/maxima, determine the occurrence of small-scale surface blooms in the North Pacific Subtropical Gyre.

Kolber, Z. S.; Tozzi, S.; Klimov, D.

2008-12-01

8

A process-based model to estimate gas exchange and monoterpene emission rates in the mediterranean maquis - comparisons between modelled and measured fluxes at different scales  

NASA Astrophysics Data System (ADS)

This paper concerns the application of a process-based model (MOCA, Modelling of Carbon Assessment) as an useful tool for estimating gas exchange, and integrating the empirical algorithms for calculation of monoterpene fluxes, in a Mediterranean maquis of central Italy (Castelporziano, Rome). Simulations were carried out for a range of hypothetical but realistic canopies of the evergreen Quercus ilex (holm oak), Arbutus unedo (strawberry tree) and Phillyrea latifolia. More, the dependence on total leaf area and leaf distribution of monoterpene fluxes at the canopy scale has been considered in the algorithms. Simulation of the gas exchange rates showed higher values for P. latifolia and A. unedo (2.39±0.30 and 3.12±0.27 gC m-2 d-1, respectively) with respect to Q. ilex (1.67±0.08 gC m-2 d-1) in the measuring campaign (May-June). Comparisons of the average Gross Primary Production (GPP) values with those measured by eddy covariance were well in accordance (7.98±0.20 and 6.00±1.46 gC m-2 d-1, respectively, in May-June), although some differences (of about 30%) were evident in a point-to-point comparison. These differences could be explained by considering the non uniformity of the measuring site where diurnal winds blown S-SW direction affecting thus calculations of CO2 and water fluxes. The introduction of some structural parameters in the algorithms for monoterpene calculation allowed to simulate monoterpene emission rates and fluxes which were in accord to those measured (6.50±2.25 vs. 9.39±4.5?g g-1DW h-1 for Q. ilex, and 0.63±0.207?g g-1DW h-1 vs. 0.98±0.30?g g-1DW h-1 for P. latifolia). Some constraints of the MOCA model are discussed, but it is demonstrated to be an useful tool to simulate physiological processes and BVOC fluxes in a very complicated plant distributions and environmental conditions, and necessitating also of a low number of input data.

Vitale, M.; Matteucci, G.; Fares, S.; Davison, B.

2009-02-01

9

Beta ray flux measuring device  

DOEpatents

A beta ray flux measuring device in an activated member in-core instrumentation system for pressurized water reactors. The device includes collector rings positioned about an axis in the reactor's pressure boundary. Activated members such as hydroballs are positioned within respective ones of the collector rings. A response characteristic such as the current from or charge on a collector ring indicates the beta ray flux from the corresponding hydroball and is therefore a measure of the relative nuclear power level in the region of the reactor core corresponding to the specific exposed hydroball within the collector ring.

Impink, Jr., Albert J. (Murrysville, PA); Goldstein, Norman P. (Murrysville, PA)

1990-01-01

10

Relationships between enzymatic flux capacities and metabolic flux rates: Nonequilibrium reactions in muscle glycolysis  

PubMed Central

The rules that govern the relationships between enzymatic flux capacities (Vmax) and maximum physiological flux rates (v) at enzyme-catalyzed steps in pathways are poorly understood. We relate in vitro Vmax values with in vivo flux rates for glycogen phosphorylase, hexokinase, and phosphofructokinase, enzymes catalyzing nonequilibrium reactions, from a variety of muscle types in fishes, insects, birds, and mammals. Flux capacities are in large excess over physiological flux rates in low-flux muscles, resulting in low fractional velocities (%Vmax = v/Vmax × 100) in vivo. In high-flux muscles, close matches between flux capacities and flux rates (resulting in fractional velocities approaching 100% in vivo) are observed. These empirical observations are reconciled with current concepts concerning enzyme function and regulation. We suggest that in high-flux muscles, close matches between enzymatic flux capacities and metabolic flux rates (i.e., the lack of excess capacities) may result from space constraints in the sarcoplasm. PMID:9192692

Suarez, R. K.; Staples, J. F.; Lighton, J. R. B.; West, T. G.

1997-01-01

11

Carbon Dioxide Flux Measurement Systems (CO2Flux) Handbook  

SciTech Connect

The Southern Great Plains (SGP) carbon dioxide flux (CO2 flux) measurement systems provide half-hour average fluxes of CO2, H2O (latent heat), and sensible heat. The fluxes are obtained by the eddy covariance technique, which computes the flux as the mean product of the vertical wind component with CO2 and H2O densities, or estimated virtual temperature. A three-dimensional sonic anemometer is used to obtain the orthogonal wind components and the virtual (sonic) temperature. An infrared gas analyzer is used to obtain the CO2 and H2O densities. A separate sub-system also collects half-hour average measures of meteorological and soil variables from separate 4-m towers.

Fischer, M

2005-01-01

12

Measurement of heat flux from steaming ground  

Microsoft Academic Search

The total thermal flux at the surface of ‘steaming ground’ consists of a convective and a conductive component, even in the absence of any visible steam discharge at the surface. The total flux and its convective component can be measured separately and directly using a water-filled ground calorimeter. The conductive component is given by the difference between the two fluxes,

Manfred P. Hochstein; Christopher J. Bromley

2005-01-01

13

Metabolic rate measurement system  

NASA Technical Reports Server (NTRS)

The Metabolic Rate Measurement System (MRMS) is an uncomplicated and accurate apparatus for measuring oxygen consumption and carbon dioxide production of a test subject. From this one can determine the subject's metabolic rate for a variety of conditions, such as resting or light exercise. MRMS utilizes an LSI/11-03 microcomputer to monitor and control the experimental apparatus.

Koester, K.; Crosier, W.

1980-01-01

14

Quantifying the "chamber effect" in CO2 flux measurements  

NASA Astrophysics Data System (ADS)

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.

Vihermaa, Leena; Childs, Amy; Long, Hazel; Waldron, Susan

2014-05-01

15

A nonstationary method for measuring heat fluxes  

Microsoft Academic Search

A nonstationary method for measuring heat fluxes using a hollow cylindrical probe placed in the critical cross section of a nozzle is proposed. The temperature at a fixed distance from the inner surface of the probe is measured as a function of time. The time variation of the heat flux is determined by solving the one-dimensional nonlinear heat-conduction equation.

V. S. Kulikov; G. A. Surkov; V. V. Mazak; F. B. Yurevich

1975-01-01

16

Diamagnetic flux measurement in Aditya tokamak  

SciTech Connect

Measurements of diamagnetic flux in Aditya tokamak for different discharge conditions are reported for the first time. The measured diamagnetic flux in a typical discharge is less than 0.6 mWb and therefore it has required careful compensation for various kinds of pick-ups. The hardware and software compensations employed in this measurement are described. We introduce compensation of a pick-up due to plasma current of less than 20 kA in short duration discharges, in which plasma pressure gradient is supposed to be negligible. The flux measurement during radio frequency heating is also presented in order to validate compensation.

Kumar, Sameer; Jha, Ratneshwar; Lal, Praveen; Hansaliya, Chandresh; Gopalkrishna, M. V.; Kulkarni, Sanjay; Mishra, Kishore [Institute for Plasma Research, Bhat, Near Indira Bridge, Gandhinagar 382428 (India)

2010-12-15

17

Atmospheric sulfur flux rates to and from Israel.  

PubMed

Both field measurements and model simulation studies have shown that Israel is the recipient of long range transported air pollutants that originated over various parts of Europe. The present paper presents results of aircraft measurements aimed at quantitizing the sulfur flux arriving at Israel's western coast from Europe and the Israeli pollution contribution to the air masses leaving its eastern borders towards Jordan. During the research flights, measurements of sulfur dioxide and sulfate particulates and meteorological data were recorded. Two different legs were performed for each research flight: one over the Mediterranean Sea, west of the coast and the second along the Jordan Valley. All flights were carried out at a height of approximately 300 m above ground level. A total of 14 research flights were performed covering the summer and autumn seasons. The results indicate that the influx of sulfur arriving at the Israeli coast from Europe varied in the range of 1-30 mg S/h, depending on the measuring season. The particulate sulfate level in the incoming LRT air masses was at least 50% of the total sulfur content. The contribution of the local pollutant sources to the outgoing easterly fluxes also varies strongly according to season. During the early and late summer, the Israeli sources contributed an average of 25 mg S/h to the total pollution flux as compared to only approximately 9 mg S/h during the autumn period. Synoptic analysis indicates that conditions during the summer in Israel favor the accumulation of pollution species above the Mediterranean basin from upwind European sources. This season features a shallow mixed layer and weak zonal flow leads to poor ventilation rates, inhibiting an efficient dispersion of these pollutants while being transported eastward. Under these conditions, in flux, local contribution and the total out-flux of these pollutants are elevated as opposed to during other seasons. During the fall, the eastern Mediterranean region is usually subjected to weak easterly winds, interrupted at times by strong westerly wind flows inducing higher ventilation rates. These meteorological conditions and the lack of major emitting sources eastwards of Israel result in lower sulfur budgets to and from Israel for this season. An estimate of the yearly flux showed that approximately 0.06 tg S arrived at the Israeli coast from the west. This is approximately 15% of the estimated pollution leaving Europe towards the eastern edge of the Mediterranean basin. The local contribution to the out-flux towards Jordan was calculated to be 0.13 tg S per year, almost all of the sulfur air pollutants emitted in Israel. PMID:12150434

Matvev, Valeri; Dayan, Un; Tass, Iran; Peleg, Mordechai

2002-05-27

18

Diamagnetic flux measurement in Aditya tokamak  

Microsoft Academic Search

Measurements of diamagnetic flux in Aditya tokamak for different discharge conditions are reported for the first time. The measured diamagnetic flux in a typical discharge is less than 0.6 mWb and therefore it has required careful compensation for various kinds of pick-ups. The hardware and software compensations employed in this measurement are described. We introduce compensation of a pick-up due

Sameer Kumar; Ratneshwar Jha; Praveen Lal; Chandresh Hansaliya; M. V. Gopalkrishna; Sanjay Kulkarni; Kishore Mishra

2010-01-01

19

A simple method for measuring heat flux  

Microsoft Academic Search

A method is described for the measurement of heat flux using the temperature gradient in a metal pad welded to two adjacent cooling tubes. A number of laboratory experiments have shown that the simple theoretical expression for calculating the heat flux is justified; the meter has operated successfully in an oil-fired boiler.

D. Anson; A. M. Godridge

1967-01-01

20

Eddy Correlation Flux Measurement System (ECOR) Handbook  

SciTech Connect

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.

Cook, DR

2011-01-31

21

Chlorine fluxing for removal of magnesium from molten aluminum: Part I. Laboratory-scale measurements of reaction rates and bubble behavior  

Microsoft Academic Search

Chlorine fluxing is widely used in the aluminum industry for the removal of magnesium from molten aluminum. Typically, it\\u000a consists of bubbling a nitrogen\\/chlorine or argon\\/chlorine mixture into the melt. This Part I of a two-part article describes\\u000a laboratory-scale experiments on the kinetics of the reactions and emissions during chlorine fluxing for magnesium removal.\\u000a Bubble frequency, size, and residence time

Qian Fu; Dong Xu; James W. Evans

1998-01-01

22

Experimental flux measurements on a network scale  

SciTech Connect

Metabolic flux is a fundamental property of living organisms. In recent years, methods for measuring metabolic flux in plants on a network scale have evolved further. One major challenge in studying flux in plants is the complexity of the plant's metabolism. In particular, in the presence of parallel pathways in multiple cellular compartments, the core of plant central metabolism constitutes a complex network. Hence, a common problem with the reliability of the contemporary results of {sup 13}C-Metabolic Flux Analysis in plants is the substantial reduction in complexity that must be included in the simulated networks; this omission partly is due to limitations in computational simulations. Here, I discuss recent emerging strategies that will better address these shortcomings.

Schwender, J.

2011-10-11

23

Noninvasive measurement of pulmonary transvascular protein flux in normal man.  

PubMed Central

Onset of lung edema is usually associated with increase in the pulmonary transvascular flux of water and proteins. Clinical measurement of these parameters may aid in early diagnosis of pulmonary edema, and allow differentiation between "cardiogenic" and "noncardiogenic" types base on the magnitude of the detected changes. We have previously described a noninvasive method for estimating transvascular protein flux in lung (Gorin, A. B., W. J. Weidner, R. H. Demling, and N. C. Staub, 1978. Noninvasive measurement of pulmonary transvascular protein flux in sheep. J. Appl. Physiol. 45: 225-233). Using this method we measured the net transvascular flux of [113mIn]transferrin (mol wt, 76,000 in lungs of nine normal human volunteers. Plasma clearance of [113In]transferrin occurred with a T1/2 = 7.0 +/- 2.6 h (mean +/- SD). The pulmonary transvascular flux coefficient, alpha, was 2.9 +/- 1.4 X 10(-3) ml/s (mean +/- SD) in man, slightly greater than that previously measured in sheep (2.7 +/- 0.7 X 10(-3) ml/s; mean +/- SD). The pulmonary transcapillary escape rate is twofold greater than the transcapillary escape rate for the vascular bed as a whole, indicating a greater "porosity" of exchanging vessels in the lung than exists for the "average" microvessel in the body. Time taken to reach half-equilibrium concentration of tracer protein in the lung interstitium was quite short, 52 +/- 13 min (mean +/- SD). We have shown that measurement of pulmonary transvascular protein flux in man is practical. The coefficient of variation of measurements of alpha (between subjects) was 0.48, and of measurements of pulmonary transcapillary escape rates was 0.39. In animals, endothelial injury commonly results in a two- to threefold increase in transvascular protein flux. Thus, external radioflux detection should be a suitable means of quantitating lung vascular injury in human disease states. PMID:7430349

Gorin, A B; Kohler, J; DeNardo, G

1980-01-01

24

Fundamentals of heat measurement. [heat flux transducers  

NASA Technical Reports Server (NTRS)

Various methods and devices for obtaining experimental data on heat flux density over wide ranges of temperature and pressure are examined. Laboratory tests and device fabrication details are supplemented by theoretical analyses of heat-conduction and thermoelectric effects, providing design guidelines and information relevant to further research and development. A theory defining the measure of correspondence between transducer signal and the measured heat flux is established for individual (isolated) heat flux transducers subject to space and time-dependent loading. An analysis of the properties of stacked (series-connected) transducers of various types (sandwich-type, plane, and spiral) is used to derive a similarity theory providing general governing relationships. The transducers examined are used in 36 types of derivative devices involving direct heat loss measurements, heat conduction studies, radiation pyrometry, calorimetry in medicine and industry and nuclear reactor dosimetry.

Gerashchenko, O. A.

1979-01-01

25

Cosmic muon flux measurements at the Kimballton Underground Research Facility  

NASA Astrophysics Data System (ADS)

In this article, the results from a series of muon flux measurements conducted at the Kimballton Underground Research Facility (KURF), Virginia, United States, are presented. The detector employed for these investigations, is made of plastic scintillator bars readout by wavelength shifting fibers and multianode photomultiplier tubes. Data was taken at several locations inside KURF, spanning rock overburden values from ~ 200 to 1450 m.w.e. From the extracted muon rates an empirical formula was devised, that estimates the muon flux inside the mine as a function of the overburden. The results are in good agreement with muon flux calculations based on analytical models and MUSIC.

Kalousis, L. N.; Guarnaccia, E.; Link, J. M.; Mariani, C.; Pelkey, R.

2014-08-01

26

Cosmic Muon Flux Measurements at the Kimballton Underground Research Facility  

E-print Network

In this article, the results from a series of muon flux measurements conducted at the Kimballton Underground Research Facility (KURF), Virginia, United States, are presented. The detector employed for these investigations, is made of plastic scintillator bars readout by wavelength shifting fibers and multianode photomultiplier tubes. Data was taken at several locations inside KURF, spanning rock overburden values from ~ 200 to 1450 m.w.e. From the extracted muon rates an empirical formula was devised, that estimates the muon flux inside the mine as a function of the overburden. The results are in good agreement with muon flux calculations based on analytical models and MUSIC.

Kalousis, L N; Link, J M; Mariani, C; Pelkey, R

2014-01-01

27

Cosmic Muon Flux Measurements at the Kimballton Underground Research Facility  

E-print Network

In this article, the results from a series of muon flux measurements conducted at the Kimballton Underground Research Facility (KURF), Virginia, United States, are presented. The detector employed for these investigations, is made of plastic scintillator bars readout by wavelength shifting fibers and multianode photomultiplier tubes. Data was taken at several locations inside KURF, spanning rock overburden values from ~ 200 to 1450 m.w.e. From the extracted muon rates an empirical formula was devised, that estimates the muon flux inside the mine as a function of the overburden. The results are in good agreement with muon flux calculations based on analytical models and MUSIC.

L. N. Kalousis; E. Guarnaccia; J. M. Link; C. Mariani; R. Pelkey

2014-06-10

28

A process-based model to estimate gas exchange and monoterpene emission rates in the mediterranean maquis - comparisons between modelled and measured fluxes at different scales  

Microsoft Academic Search

This paper concerns the application of a process-based model (MOCA, Modelling of Carbon Assessment) as an useful tool for estimating gas exchange, and integrating the empirical algorithms for calculation of monoterpene fluxes, in a Mediterranean maquis of central Italy (Castelporziano, Rome). Simulations were carried out for a range of hypothetical but realistic canopies of the evergreen Quercus ilex (holm oak),

M. Vitale; G. Matteucci; S. Fares; B. Davison

2009-01-01

29

Denoising surface renewal flux density measurements  

NASA Astrophysics Data System (ADS)

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.

Shapland, T.; Paw U, K.; Snyder, R. L.; McElrone, A.; Calderon Orellana, A.; Williams, L.

2012-12-01

30

Plasma momentum meter for momentum flux measurements  

DOEpatents

Invention comprises an instrument in which momentum flux onto a biasable target plate is transferred via a suspended quartz tube onto a sensitive force transducer--a capacitance-type pressure gauge. The transducer is protected from thermal damage, arcing and sputtering, and materials used in the target and pendulum are electrically insulating, rigid even at elevated temperatures, and have low thermal conductivity. The instrument enables measurement of small forces (10.sup.-5 to 10.sup.3 N) accompanied by high heat fluxes which are transmitted by energetic particles with 10's of eV of kinetic energy in a intense magnetic field and pulsed plasma environment.

Zonca, Fulvio (Rome, IT); Cohen, Samuel A. (Hopewell, NJ); Bennett, Timothy (Princeton, NJ); Timberlake, John R. (Allentown, NJ)

1993-01-01

31

Calorimeter probes for measuring high thermal flux. [in arc jets  

NASA Technical Reports Server (NTRS)

Expendable, slug-type calorimeter probes were developed for measuring high heat-flux levels of 10-30 kW/sq cm in electric-arc jet facilities. The probes were constructed with thin tungsten caps mounted on Teflon bodies. The temperature of the back surface of the tungsten cap is measured, and its time rate of change gives the steady-state absorbed heat flux as the calorimeter probe heats to destruction when inserted into the arc jet. Design, construction, test, and performance data are presented.

Russell, L. D.

1979-01-01

32

An investigation of the consistency of the ionospheric measurements of the photoelectron flux and solar EUV flux  

NASA Technical Reports Server (NTRS)

This paper demonstrates that there is an inconsistency between ionospheric measurements of the photoelectron flux and the solar EUV flux. The problem which occurs for EUV wavelengths near 250 A or photoelectron energies near 35 eV has serious implications for theoretical photoelectron flux calculations and could help to explain up to 40 percent of the difference between calculated and measured photoelectron fluxes for electron energies below 35 eV. It is also shown that: (1) only photons with wavelengths shorter than 310 A are of importance in producing photoelectrons; (2) above 20 eV, the photoelectron flux is controlled by the production of primary photoelectrons, while below 20 eV the flux is controlled by degraded photoelectrons; (3) the calculated cascading production rate is insensitive to the cross sections used for the calculation; and (4) the photoelectron flux is inversely proportional to the total inelastic cross sections.

Richards, P. G.; Torr, D. G.

1984-01-01

33

High heat flux measurements and experimental calibrations/characterizations  

NASA Technical Reports Server (NTRS)

Recent progress in techniques employed in the measurement of very high heat-transfer rates in reentry-type facilities at the Arnold Engineering Development Center (AEDC) is described. These advances include thermal analyses applied to transducer concepts used to make these measurements; improved heat-flux sensor fabrication methods, equipment, and procedures for determining the experimental time response of individual sensors; performance of absolute heat-flux calibrations at levels above 2,000 Btu/cu ft-sec (2.27 kW/cu cm); and innovative methods of performing in-situ run-to-run characterizations of heat-flux probes installed in the test facility. Graphical illustrations of the results of extensive thermal analyses of the null-point calorimeter and coaxial surface thermocouple concepts with application to measurements in aerothermal test environments are presented. Results of time response experiments and absolute calibrations of null-point calorimeters and coaxial thermocouples performed in the laboratory at intermediate to high heat-flux levels are shown. Typical AEDC high-enthalpy arc heater heat-flux data recently obtained with a Calspan-fabricated null-point probe model are included.

Kidd, Carl T.

1992-01-01

34

A new disjunct eddy-covariance system for BVOC flux measurements - validation on CO2 and H2O fluxes  

NASA Astrophysics Data System (ADS)

The disjunct eddy covariance (DEC) method is an interesting alternative to the conventional eddy covariance (EC) method because it allows the estimation of turbulent fluxes of species for which fast sensors are not available. We have developed and validated a new disjunct sampling system (called MEDEE). This system is built with chemically inert materials. Air samples are taken quickly and alternately in two cylindrical reservoirs, the internal pressures of which are regulated by a moving piston. The MEDEE system was designed to be operated either on the ground or aboard an aircraft. It is also compatible with most analysers since it transfers the air samples at a regulated pressure. To validate the system, DEC and EC measurements of CO2 and latent heat fluxes were performed concurrently during a field campaign. EC fluxes were first compared to simulated DEC (SDEC) fluxes and then to actual DEC fluxes. Both the simulated and actual DEC fluxes showed a good agreement with EC fluxes in terms of correlation. The determination coefficients (R2) were 0.93 and 0.91 for DEC and SDEC latent heat fluxes, respectively. For DEC and SDEC CO2 fluxes R2 was 0.69 in both cases. The conditions of low fluxes experienced during the campaign impaired the comparison of the different techniques especially for CO2 flux measurements. Linear regression analysis showed an 14% underestimation of DEC fluxes for both CO2 and latent heat compared to EC fluxes. A first field campaign, focusing on biogenic volatile organic compound (BVOC) emissions, was carried out to measure isoprene fluxes above a downy oak (Quercus Pubescens) forest in the south-east of France. The measured standard emission rate was in the lower range of reported values in earlier studies. Further analysis will be conducted through ground-based and airborne campaigns in the coming years.

Baghi, R.; Durand, P.; Jambert, C.; Jarnot, C.; Delon, C.; Serça, D.; Striebig, N.; Ferlicoq, M.; Keravec, P.

2012-12-01

35

A new disjunct eddy-covariance system for BVOC flux measurements - validation on CO2 and H2O fluxes  

NASA Astrophysics Data System (ADS)

The disjunct eddy covariance (DEC) method is an interesting alternative to the conventional eddy covariance (EC) method, because it allows the estimation of turbulent fluxes of species for which fast sensors are not available. A new disjunct sampling system (called MEDEE) was developed and validated. This system was built with chemically inert materials. Air samples are grabbed quickly and alternately in two cylindrical reservoirs, whose internal pressures are regulated by a moving piston. It was designed to be operated either on ground or aboard an airplane (the French ATR-42 research aircraft). It is also compatible with most analysers since it transfers the air samples at a regulated pressure. For validating the system, DEC and EC measurements of CO2 and latent heat fluxes were performed concurrently during a field campaign. EC fluxes were first compared to simulated DEC (SDEC) fluxes and then to actual DEC fluxes. The EC fluxes were in agreement with both the simulated and actual DEC fluxes. The EC fluxes compare well to SDEC fluxes (R2 = 0.92 and 0.68 for latent heat and CO2 fluxes, respectively) and to actual DEC fluxes (R2 = 0.91 and 0.67 for latent heat and CO2 fluxes, respectively), in spite of low fluxes experienced during the campaign. This good agreement between the two techniques demonstrates that MEDEE is suitable for DEC measurements and highlights the DEC method as a reliable alternative to EC for slower sensors. A first field campaign focused on biogenic volatile organic compound (BVOC) emissions was done to measure isoprene fluxes above a downy oak (Quercus Pubescens) forest in the southeast of France. The measured emission rates were in good agreement with the values reported in earlier studies. Further analysis will be conducted from ground-based and airborne campaigns in the forthcoming years.

Baghi, R.; Durand, P.; Jambert, C.; Jarnot, C.; Delon, C.; Serça, D.; Striebig, N.; Ferlicoq, M.; Keravec, P.

2012-06-01

36

Upper-Bound SEU Rates In Anisotropic Fluxes  

NASA Technical Reports Server (NTRS)

Upper bounds on rates of single-event upsets (SEU's) in digital integrated circuits and other electronic devices exposed to anisotropic fluxes of energetic ionizing particles computed by use of improved method. Derived from simplified, worst-case mathematical models of charge-collecting volumes and physical phenomena in electronic devices.

Edmonds, Larry D.

1993-01-01

37

Rapid and Precise Determination of Cellular Amino Acid Flux Rates  

E-print Network

Rapid and Precise Determination of Cellular Amino Acid Flux Rates Using HPLC with Automated synthesis may consume larger quantities of amino acids than other cell types. HPLC with precolumn. Experimental HPLC The ZORBAX Eclipse Plus amino acid analysis (AAA) method was performed using an Agilent 1100

Wikswo, John

38

NIST Measurement Services: Heat-Flux Sensor Calibration  

E-print Network

NIST Measurement Services: Heat-Flux Sensor Calibration NIST Special Publication 250-65 Benjamin K Special Publication 250-65 NIST MEASUREMENT SERVICES: Heat-Flux Sensor Calibration Benjamin K. Tsai Measurement Services: Heat-Flux Sensor Calibrations is a new publication. It covers the calibration of heat

39

Rating Scale Instruments and Measurement  

ERIC Educational Resources Information Center

The article examines theoretical issues associated with measurement in the human sciences and ensuring data from rating scale instruments are measures. An argument is made that using raw scores from rating scale instruments for subsequent arithmetic operations and applying linear statistics is less preferable than using measures. These theoretical…

Cavanagh, Robert F.; Romanoski, Joseph T.

2006-01-01

40

Data assimilation tool to reconstruct particle flux measurements  

NASA Astrophysics Data System (ADS)

In the framework of the EU-FP7 MAARBLE project, the Salammbô code and an ensemble Kalman filter is being used to reproduce the electron radiation belt dynamics during storms: (1) The ONERA data assimilation tool has been improved to ingest count rates instead of flux when the instrument response function is available. As an example, the ESA/SREM radiation monitor has complex response functions (proton and electron events are mixed, and for a given specie the instrument responds to a broad range of energies with different efficiencies) which makes very challenging to get fluxes out of count rates. (2) INTEGRAL/SREM, GIOVE-B/SREM, XMM/ERMD and GOES/SEM data assimilation is performed to reproduce with high fidelity the electron belt dynamics during magnetic storms. (3) Because the outputs of the tool are phase space densities, it is then possible to reconstruct INTEGRAL/SREM and GIOVE-B/SREM fluxes time series. In the present talk, an overview of the data assimilation tool will be given. The advantage of using assimilation tool to reconstruct particle flux measurements will be discussed. MAARBLE has received fundings from the European Community's Seventh Framework Programme (FP7-SPACE-.2010-1, SP1 Cooperation, Collaborative project) under grant agreement n284520. This paper reflects only the authors' views and the European Union is not liable for any use that may be made of the information contained therein.

Bourdarie, Sebastien A.; Maget, Vincent; Lazaro, Didier; Sandberg, Ingmar

2014-05-01

41

Plasma momentum meter for momentum flux measurements  

DOEpatents

An apparatus is described for measuring momentum flux from an intense plasma stream, comprising: refractory target means oriented normal to the flow of said plasma stream for bombardment by said plasma stream where said bombardment by said plasma stream applies a pressure to said target means, pendulum means for communicating a translational displacement of said target to a force transducer where said translational displacement of said target is transferred to said force transducer by an elongated member coupled to said target, where said member is suspended by a pendulum configuration means and where said force transducer is responsive to said translational displacement of said member, and force transducer means for outputting a signal representing pressure data corresponding to said displacement.

Zonca, F.; Cohen, S.A.; Bennett, T.; Timberlake, J.R.

1993-08-24

42

An evaluation of sediment rating curves for estimating suspended sediment concentrations for subsequent flux calculations  

USGS Publications Warehouse

In the absence of actual suspended sediment concentration (SSC) measurements, hydrologists have used sediment rating (sediment transport) curves to estimate (predict) SSCs for subsequent flux calculations. Various evaluations of the sediment rating-curve method were made using data from long-term, daily sediment-measuring sites within large (>1 000 000 km2), medium ( 1000 km2), and small (<1000 km2) river basins in the USA and Europe relative to the estimation of suspended sediment fluxes. The evaluations address such issues as the accuracy of flux estimations for various levels of temporal resolution as well as the impact of sampling frequency on the magnitude of flux estimation errors. The sediment rating-curve method tends to underpredict high, and overpredict low SSCs. As such, the range of errors associated with concomitant flux estimates for relatively short time-frames (e.g. daily, weekly) are likely to be substantially larger than those associated with longer time-frames (e.g. quarterly, annually) because the over- and underpredictions do not have sufficient time to balance each other. Hence, when error limits must be kept under ??20%, temporal resolution probably should be limited to quarterly or greater. The evaluations indicate that over periods of 20 or more years, errors of <1% can be achieved using a single sediment rating curve based on data spanning the entire period. However, somewhat better estimates for the entire period, and markedly better annual estimates within the period, can be obtained if individual annual sediment rating curves are used instead. Relatively accurate (errors fluxes can be obtained from hydrologically based monthly measurements/samples. For 5-year periods or longer, similar results can be obtained from measurements/samples collected once every 2 months. In either case, hydrologically based sampling, as opposed to calendar-based sampling is likely to limit the magnitude of flux estimation errors. Published in 2003 by John Wiley and Sons, Ltd.

Horowitz, A.J.

2003-01-01

43

Large Area Lunar Dust Flux Measurement Instrument  

NASA Technical Reports Server (NTRS)

The instrument under development is designed to characterize the flux and size distribution of the lunar micrometeoroid and secondary ejecta environment. When deployed on the lunar surface, the data collected will benefit fundamental lunar science as well as enabling more reliable impact risk assessments for human lunar exploration activities. To perform this task, the instrument requirements are demanding. It must have as large a surface area as possible to sample the very sparse population of the larger potentially damage-inducing micrometeorites. It must also have very high sensitivity to enable it to measure the flux of small (<10 micron) micrometeorite and secondary ejecta dust particles. To be delivered to the lunar surface, it must also be very low mass, rugged and stow compactly. The instrument designed to meet these requirements is called FOMIS. It is a large-area thin film under tension (i.e. a drum) with multiple fiber optic displacement (FOD) sensors to monitor displacements of the film. This sensor was chosen since it can measure displacements over a wide dynamic range: 1 cm to sub-Angstrom. A prototype system was successfully demonstrated using the hypervelocity impact test facility at the University of Kent (Canterbury, UK). Based on these results, the prototype system can detect hypervelocity (approx.5 km/s) impacts by particles as small as 2 microns diameter. Additional tests using slow speeds find that it can detect secondary ejecta particles (which do not penetrate the film) with momentums as small as 15 pico-gram 100m/s, or nominally 5 microns diameter at 100 m/s.

Corsaro, R.; Giovane, F.; Liou, Jer-Chyi; Burchell, M.; Stansbery, Eugene; Lagakos, N.

2009-01-01

44

Measurement of local high-level, transient surface heat flux  

NASA Technical Reports Server (NTRS)

This study is part of a continuing investigation to develop methods for measuring local transient surface heat flux. A method is presented for simultaneous measurements of dual heat fluxes at a surface location by considering the heat flux as a separate function of heat stored and heat conducted within a heat flux gage. Surface heat flux information is obtained from transient temperature measurements taken at points within the gage. Heat flux was determined over a range of 4 to 22 MW/sq m. It was concluded that the method is feasible. Possible applications are for heat flux measurements on the turbine blade surfaces of space shuttle main engine turbopumps and on the component surfaces of rocket and advanced gas turbine engines and for testing sensors in heat flux gage calibrators.

Liebert, Curt H.

1988-01-01

45

Measuring Fluxes Of Heat To A Plasma-Arc Anode  

NASA Technical Reports Server (NTRS)

Three probes constructed to provide measurements indicative of conductive, convective, and radiative transfer of heat from free-burning plasma arc to water-cooled copper anode used in generating arc. Each probe consists mainly of copper body with two thermocouples embedded at locations 4 mm apart along length. Thermocouples provide measure of rate of conduction of heat along probe and transfers of heat from plasma to sensing surface at tip of probe. Probes identical except sensing surface of one uncoated and other two coated with different materials to make them sensitive to different components of overall flux of heat.

Sankovic, John M.; Menart, James A.; Pfender, Emil; Heberlein, Joachim

1995-01-01

46

Evaluation of the N2 flux approach for measuring sediment denitrification  

Microsoft Academic Search

Direct gas chromatographic measurement of denitrification rates via N2 fluxes from aquatic sediments can avoid some of the artifacts and complexities associated with indirect approaches and tracer techniques. However, measurement protocols have typically been determined based upon initial results or previous studies. We present a process-level study and simulation model for evaluating and optimizing N2 gas flux approaches in closed

M. Robert Hamersley; Brian L. Howes

2005-01-01

47

Denitrification in the Upper Mississippi River: rates, controls, and contribution to nitrate flux  

E-print Network

Denitrification in the Upper Mississippi River: rates, controls, and contribution to nitrate flux denitrification in the upper Mississippi River. Measurements were taken over 2 years, during which river discharge). Denitrification in this reach of the upper Mississippi River appears to be NO3 ­ limited throughout the growing

Strauss, Eric A.

48

Measuring Your Peak Flow Rate  

MedlinePLUS

... the latest information on lung health and healthy air in your email. » Register for ENews Home > Lung Disease > Asthma > Taking Control of Asthma Measuring Your Peak Flow Rate A peak flow meter is a portable, ...

49

A comparison of new measurements of total monoterpene flux with improved measurements of speciated monoterpene flux  

NASA Astrophysics Data System (ADS)

Many monoterpenes have been identified in forest emissions using gas chromatography (GC). Until now, it has been impossible to determine whether all monoterpenes are appropriately measured using GC techniques. We used a proton transfer reaction mass spectrometer (PTR-MS) coupled with the eddy covariance (EC) technique to measure mixing ratios and fluxes of total monoterpenes above a ponderosa pine plantation. We compared PTR-MS-EC results with simultaneous measurements of eight speciated monoterpenes, ?-pinene, ?-pinene, 3-carene, d-limonene, ?-phellandrene, ?-terpinene, camphene, and terpinolene, made with an automated, in situ gas chromatograph with flame ionization detectors (GC-FID), coupled to a relaxed eddy accumulation system (REA). Monoterpene mixing ratios and fluxes measured by PTR-MS averaged 30±2.3% and 31±9.2% larger than by GC-FID, with larger differences at night than during the day. Four unidentified peaks that correlated with ?-pinene were resolved in the chromatograms and completely accounted for the daytime difference and reduced the nighttime difference to 19±3.4%. Measurements of total monoterpenes by PTR-MS-EC indicated that GC-FID-REA measured the common, longer-lived monoterpenes well, but that additional monoterpenes were emitted from the ecosystem that represented an important contribution to the total mixing ratio above the forest at night, and that must have been oxidized during the day before they escaped the forest canopy.

Lee, A.; Schade, G. W.; Holzinger, R.; Goldstein, A. H.

2004-12-01

50

A comparison of new measurements of total monoterpene flux with improved measurements of speciated monoterpene flux  

NASA Astrophysics Data System (ADS)

Many monoterpenes have been identified in forest emissions using gas chromatography (GC). Until now, it has been impossible to determine whether all monoterpenes are appropriately measured using GC techniques. We used a proton transfer reaction mass spectrometer (PTR-MS) coupled with the eddy covariance (EC) technique to measure mixing ratios and fluxes of total monoterpenes above a ponderosa pine plantation. We compared PTR-MS-EC results with simultaneous measurements of eight speciated monoterpenes, ?-pinene, ?-pinene, 3-carene, d-limonene, ?-phellandrene, ?-terpinene, camphene, and terpinolene, made with an automated, in situ gas chromatograph with flame ionization detectors (GC-FID), coupled to a relaxed eddy accumulation system (REA). Monoterpene mixing ratios and fluxes measured by PTR-MS averaged 30±2.3% and 31±9.2% larger than by GC-FID, with larger mixing ratio discrepancies between the two techniques at night than during the day. Two unidentified peaks that correlated with ?-pinene were resolved in the chromatograms and completely accounted for the daytime difference and reduced the nighttime mixing ratio difference to 20±2.9%. Measurements of total monoterpenes by PTR-MS-EC indicated that GC-FID-REA measured the common, longer-lived monoterpenes well, but that additional terpenes were emitted from the ecosystem that represented an important contribution to the total mixing ratio above the forest at night.

Lee, A.; Schade, G. W.; Holzinger, R.; Goldstein, A. H.

2005-02-01

51

Heat flux microsensor measurements and calibrations  

NASA Technical Reports Server (NTRS)

A new thin-film heat flux gage has been fabricated specifically for severe high temperature operation using platinum and platinum-10 percent rhodium for the thermocouple elements. Radiation calibrations of this gage were performed at the AEDC facility over the available heat flux range (approx. 1.0 - 1,000 W/cu cm). The gage output was linear with heat flux with a slight increase in sensitivity with increasing surface temperature. Survivability of gages was demonstrated in quench tests from 500 C into liquid nitrogen. Successful operation of gages to surface temperatures of 750 C has been achieved. No additional cooling of the gages is required because the gages are always at the same temperature as the substrate material. A video of oxyacetylene flame tests with real-time heat flux and temperature output is available.

Terrell, James P.; Hager, Jon M.; Onishi, Shinzo; Diller, Thomas E.

1992-01-01

52

Evaluation of contaminant flux rates from sediments of Sinclair Inlet, WA, using a benthic flux sampling device. Final report  

SciTech Connect

A Benthic Flux Sampling Device (BFSD) was demonstrated on site to determine the mobility of contaminants in sediments off the Puget Sound Naval Shipyard (PSNS) in Sinclair Inlet, WA. Quantification of toxicant flux from the sediments will support ongoing assessment studies and facilitate the design of appropriate remediation strategies, if required. In general, where release of contaminants was found, the measured rates do not represent a significant source relative to other major inputs such as sewer discharges, nonpoint source runoff, and marinas. They may, however, represent an exposure pathway for benthic biota with a subsequent potential for toxicological effects and/or bioaccumulation. Environmental assessment, CIVAPP:Toxicity, CIVAPP:Marine chemistry, Hazardous waste.

Chadwick, D.B.; Lieberman, S.H.; Reimers, C.E.; Young, D.

1993-02-01

53

AmeriFlux Measurement Network: Science Team Research  

SciTech Connect

Research involves analysis and field direction of AmeriFlux operations, and the PI provides scientific leadership of the AmeriFlux network. Activities include the coordination and quality assurance of measurements across AmeriFlux network sites, synthesis of results across the network, organizing and supporting the annual Science Team Meeting, and communicating AmeriFlux results to the scientific community and other users. Objectives of measurement research include (i) coordination of flux and biometric measurement protocols (ii) timely data delivery to the Carbon Dioxide Information and Analysis Center (CDIAC); and (iii) assurance of data quality of flux and ecosystem measurements contributed by AmeriFlux sites. Objectives of integration and synthesis activities include (i) integration of site data into network-wide synthesis products; and (ii) participation in the analysis, modeling and interpretation of network data products. Communications objectives include (i) organizing an annual meeting of AmeriFlux investigators for reporting annual flux measurements and exchanging scientific information on ecosystem carbon budgets; (ii) developing focused topics for analysis and publication; and (iii) developing data reporting protocols in support of AmeriFlux network goals.

Law, B E

2012-12-12

54

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

NASA Astrophysics Data System (ADS)

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 % higher than the during the rest of the year, but the variability is generally very high. Short-term flux minima are mainly due to precipitation events. First results will be shown of the parameterization of the 222Radon and CO2 fluxes with the groundwater level, soil temperature and humidity, rain events and atmospheric pressure changes.

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

2009-04-01

55

Measurement of the meteoroid flux at Mars  

NASA Astrophysics Data System (ADS)

In the fall of 2005, a dedicated meteor observing campaign was carried out by the Panoramic Camera (Pancam) onboard the Mars Exploration Rover (MER) Spirit to determine the viability of using MER cameras as meteor detectors and to obtain the first experimental estimate of the meteoroid flux at Mars. Our observing targets included both the sporadic meteoroid background and two predicted martian meteor showers: one associated with 1P/Halley and a potential stream associated with 2001/R1 LONEOS. A total of 353 images covering 2.7 h of net exposure time were analyzed with no conclusive meteor detections. From these data, an upper limit to the background meteoroid flux at Mars is estimated to be <4.4×10 meteoroidskmh for meteoroids with mass larger than 4 g. For comparison, the estimated flux to this mass limit at the Earth is 10 meteoroidskmh [Grün, E., Zook, H.A., Fechtig, H., Giese, R.H., 1985. Icarus 62, 244-272]. This result is qualitatively consistent, within error bounds, with theoretical models predicting martian fluxes of ˜50% that at Earth for meteoroids of mass 10-10 g [Adolfsson, L.G., Gustafson, B.A.S., Murray, C.D., 1996. Icarus 119, 144-152]. The MER cameras, even using the most sensitive mode of operation, should expect to see on average only one coincident meteor on of order 40-150 h of total exposure time based on these same theoretical martian flux estimates. To more meaningfully constrain these flux models, a longer total integrated exposure time or more sensitive camera is needed. Our analysis also suggests that the event reported as the first martian meteor [Selsis, F., Lemmon, M.T., Vaubaillon, J., Bell, J.F., 2005. Nature 435, 581] is more likely a grazing cosmic ray impact, which we show to be a major source of confusion with potential meteors in all Pancam images.

Domokos, A.; Bell, J. F.; Brown, P.; Lemmon, M. T.; Suggs, R.; Vaubaillon, J.; Cooke, W.

2007-11-01

56

Heat flux measurement in SSME turbine blade tester  

NASA Technical Reports Server (NTRS)

Surface heat flux values were measured in the turbine blade thermal cycling tester located at NASA-Marshall. This is the first time heat flux has been measured in a space shuttle main engine turbopump environment. Plots of transient and quasi-steady state heat flux data over a range of about 0 to 15 MW/sq m are presented. Data were obtained with a miniature heat flux gage device developed at NASA-Lewis. The results from these tests are being incorporated into turbine design models. Also, these gages are being considered for airfoil surface heat flux measurement on turbine vanes mounted in SSME turbopump test bed engine nozzles at Marshall. Heat flux effects that might be observed on degraded vanes are discussed.

Liebert, Curt H.

1990-01-01

57

IR thermography heat flux measurement in fire safety applications  

NASA Astrophysics Data System (ADS)

The paper deals with heat flux measurement possibilities in fire safety applications. The paper presents two methods for radiation heat flux measurement - the thermography source-target measurement method, and the radiation contact target measurement method. Both the methods were used simultaneously for radiation heat flux measurement during a fire experiment on a high-density polyethylene plastic box storage stack. The theoretical background, experimental set-up, application example, and comparison of both methods are presented in this paper. Dependence of heat flux magnitude on a distance and direction from a heat source is evaluated. The possible safety risks ensuing from high temperatures inside the burning stack, and therefore high heat fluxes near the stack, are discussed.

Švantner, Michal; Vacíková, Petra; Honner, Milan

2012-07-01

58

Non-contact heat flux measurement using a transparent sensor  

NASA Technical Reports Server (NTRS)

A working non-contact heat flux sensor was demonstrated using a transparent material (sapphire) and a multiwavelength pyrometer. The pyrometer is used to measure the temperatures of the two surfaces of the sensor from the spectrum of radiation originating from them. The heat conducted through the material is determined from the temperature difference of the two surfaces and the thermal conductivity of the material. The measured heat flux is equal to the incident heat flux within experimental error indicating that no calibration would be necessary. A steady state heat flux of 100 kW/sq m was easily achieved.

Ng, Daniel; Spuckler, Charles M.

1993-01-01

59

Dual physiological rate measurement instrument  

NASA Technical Reports Server (NTRS)

The object of the invention is to provide an instrument for converting a physiological pulse rate into a corresponding linear output voltage. The instrument which accurately measures the rate of an unknown rectangular pulse wave over an extended range of values comprises a phase-locked loop including a phase comparator, a filtering network, and a voltage-controlled oscillator, arranged in cascade. The phase comparator has a first input responsive to the pulse wave and a second input responsive to the output signal of the voltage-controlled oscillator. The comparator provides a signal dependent on the difference in phase and frequency between the signals appearing on the first and second inputs. A high-input impedance amplifier accepts an output from the filtering network and provides an amplified output DC signal to a utilization device for providing a measurement of the rate of the pulse wave.

Cooper, Tommy G. (inventor)

1990-01-01

60

A novel ozone sensor for direct eddy flux measurements  

NASA Astrophysics Data System (ADS)

A small fast-response ozone sensor for direct eddy-flux measurements is built. The basis for detection is the chemiluminescence of an organic dye adsorbed on dry silica gel in the reaction with ozone. The chemiluminescence is monitored with a blue-sensitive photomultiplier. At a flow rate of 100 l/min the ozone sensor has a 90 percent response time of significantly better than 0.1 s with a detection limit lower than 50 ppt at S/N = 3. Water vapor and SO2 enhance the chemiluminescence efficiency of the ozone sensor. No correlation between rapid ozone fluctuations and those of these two trace gases is noticed by the ozone sensor when operating at a frequency of 10 Hz. Good agreement was found between ozone dry-deposition velocities derived from profile measurements and by eddy correlation.

Guesten, Hans; Heinrich, Guenther; Schmidt, Ralf W. H.; Schurath, Ulrich

1992-04-01

61

Thrombin flux and wall shear rate regulate fibrin fiber deposition state during polymerization under flow  

NASA Astrophysics Data System (ADS)

Thrombin is released as a soluble enzyme from the platelet surface to trigger fibrin polymerization during thrombosis under flow conditions. While isotropic fibrin polymerization under static conditions involves protofibril extension and lateral aggregation leading to a gel, factors regulating fiber diameter and orientation are poorly quantified under hemodynamic flow due to the difficulty of setting thrombin fluxes. A membrane microfluidic device allowed combined control of both thrombin wall flux (10-13 to 10-11 nmol/? m^2 s) and the wall shear rate (10 to 100 s-1) of a flowing fibrinogen solution. At the thrombin flux of 10-12 nmol/? m^2 s, both fibrin deposition and fiber thickness decreased as the wall shear rate increased from 10 to 100 s-1. Direct measurement and transport-reaction simulations at 12 different thrombin flux-wall shear rate conditions demonstrated that two dimensionless numbers, the Peclet number (Pe) and the Damkohler number (Da),defined a phase diagram to predict fibrin morphology. For Da<10,we only observed thin films at all Pe. For 10900 and Pe<100, we observed three-dimensional gels. These results indicate that increase wall shear rate first quenches lateral aggregation and then protofibril extension.

Illing, Damian; Neeves, Keith

2009-10-01

62

Measurement of Flux Density of Cas A at Low Frequencies  

NASA Astrophysics Data System (ADS)

Cas A is used as a flux calibrator throughout the radio spectrum. Therefore it is important to know the spectral and secular variations in its flux density. Earlier observations by Scott et. al. (1969) and Baars et. al. (1972) suggested a secular decrease in flux density of Cas A at a rate of about 1% per year at all frequencies. However later observations by Erickson & Perley (1975) and Read (1977) indicated anomalously high flux from Cas A at 38 MHz. Also, these observations suggested that the original idea of faster decay of the flux density rate at low frequencies may be in error or that something more complex than simple decay is affecting the flux density at low frequencies. The source changes at 38 MHz still remains a mystery. We intend to present the results of follow up observations made from 1995 to 1998 with a three element interferometer in Green Bank operating in frequency range 30 to 120 MHz. We will discuss the problems at such low frequencies due to large beamwidth and unstable ionosphere. We will also discuss the strategies we have used so far to to find the flux density of Cas A by calculating the ratio of flux density of Cas A to that of Cyg A, assuming flux density of Cyg A to be constant. Above mentioned work was performed in summer student program sponsored by National Radio Astronomy Observatory.

Patil, Ajinkya; Fisher, R.

2012-01-01

63

Measurement of flux distribution in toroidal and multiaperture cores  

Microsoft Academic Search

Recently, magnetic devices utilizing a partial switching have been used in many fields. From a point of core design, a flux distribution must be known. It is possible to calculate them under some assumptions, but it is difficult to measure them experimentally. This paper describes a technique of determining a flux distribution in toroidal and multiaperture ferrite cores. The patterns

Y. Ohbuchi; T. Urabe; Y. Sakurai

1971-01-01

64

FLUX MEASUREMENTS FROM A TALL TOWER IN A COMPLEX LANDSCAPE  

SciTech Connect

The accuracy and representativeness of flux measurements from a tall tower in a complex landscape was assessed by examining the vertical and sector variability of the ratio of wind speed to momentum flux and the ratio of vertical advective to eddy flux of heat. The 30-60 m ratios were consistent with theoretical predictions which indicate well mixed flux footprints. Some variation with sector was observed that were consistent with upstream roughness. Vertical advection was negligible compared with vertical flux except for a few sectors at night. This implies minor influence from internal boundary layers. Flux accuracy is a function of sector and stability but 30-60 m fluxes were found to be generally representative of the surrounding landscape. This paper will study flux data from a 300 m tower, with 4 levels of instruments, in a complex landscape. The surrounding landscape will be characterized in terms of the variation in the ratio of mean wind speed to momentum flux as a function of height and wind direction. The importance of local advection will be assessed by comparing vertical advection with eddy fluxes for momentum and heat.

Kurzeja, R.; Weber, A.; Chiswell, S.; Parker, M.

2010-07-22

65

An analytical quantification of mass fluxes and natural attenuation rate constants at a former gasworks site  

NASA Astrophysics Data System (ADS)

A new integral groundwater investigation approach was used for the first time to quantify natural attenuation rates at field scale. In this approach, pumping wells positioned along two control planes were operated at distances of 140 and 280 m downstream of a contaminant source zone at a former gasworks site polluted with BTEX- (benzene, toluene, ethyl-benzene, o-, p-xylene) and PAH- (polycyclic aromatic hydrocarbons) compounds. Based on the quantified changes in total contaminant mass fluxes between the control planes, first-order natural attenuation rate constants could be estimated. For BTEX-compounds, these ranged from 1.4e-02 to 1.3e-01 day -1, whereas for PAH-compounds natural attenuation rate constants of 3.7e-04 to 3.1e-02 day -1 were observed. Microbial degradation activity at the site was indicated by an increase in dissolved iron mass flux and a reduction in sulphate mass flux between the two investigated control planes. In addition to information about total contaminant mass fluxes and average concentrations, an analysis of the concentration-time series measured at the control planes also allowed to semi-quantitatively delineate the aquifer regions most likely contaminated by the BTEX- and PAH-compounds.

Bockelmann, Alexander; Ptak, Thomas; Teutsch, Georg

2001-12-01

66

A Preliminary Study of CO2 Flux Measurements by Lidar  

NASA Technical Reports Server (NTRS)

A mechanistic understanding of the global carbon cycle requires quantification of terrestrial ecosystem CO2 fluxes at regional scales. In this paper, we analyze the potential of a Doppler DIAL system to make flux measurements of atmospheric CO2 using the eddy-covariance and boundary layer budget methods and present results from a ground based experiment. The goal of this study is to put CO2 flux point measurements in a mesoscale context. In June 2007, a field experiment combining a 2-m Doppler Heterodyne Differential Absorption Lidar (HDIAL) and in-situ sensors of a 447-m tall tower (WLEF) took place in Wisconsin. The HDIAL measures simultaneously: 1) CO2 mixing ratio, 2) atmosphere structure via aerosol backscatter and 3) radial velocity. We demonstrate how to synthesize these data into regional flux estimates. Lidar-inferred fluxes are compared with eddy-covariance fluxes obtained in-situ at 396m AGL from the tower. In cases where the lidar was not yet able to measure the fluxes with acceptable precision, we discuss possible modifications to improve system performance.

Gibert, Fabien; Koch, Grady J.; Beyon, Jeffrey Y.; Hilton, T.; Davis, Kenneth J.; Andrews, Arlyn; Ismail, Syed; Singh, Upendra N.

2008-01-01

67

Sensitivity of shortwave radiative flux density, forcing, and heating rates to the aerosol vertical profile  

SciTech Connect

The effect of the aerosol vertical distribution on the solar radiation profiles, for idealized and measured profiles of optical properties (extinction and single-scattering albedo (SSA)) during the May 2003 Atmospheric Radiation Measurement (ARM) Aerosol Intensive Observation Period (AIOP), has been investigated using the Rapid Radiative Transfer Model Shortwave (RRTM_SW) code. Calculated profiles of down-welling and up-welling solar fluxes during the AIOP have been compared with the data measured by up- and down-looking solar broadband radiometers aboard a profiling research aircraft. The measured profiles of aerosol extinction, SSA, and water vapor obtained from the same aircraft that carried the radiometers served as the inputs for the model calculations. It is noteworthy that for this study, the uplooking radiometers were mounted on a stabilized platform that kept the radiometers parallel with respect to the earth’s horizontal plane. The results indicate that the shape of the aerosol extinction profiles has very little impact on direct radiative forcings at the top of atmosphere and surface in a cloud-free sky. However, as long as the aerosol is not purely scattering, the shape of the extinction profiles is important for forcing profiles. Identical extinction profiles with different absorption profiles drastically influence the forcing and heating rate profiles. Using aircraft data from 19 AIOP profiles over the Southern Great Plains (SGP), we are able to achieve broadband down-welling solar flux closure within 0.8% (bias difference) or 1.8% (rms difference), well within the expected measurement uncertainty of 1 to 3%. The poorer agreement in up-welling flux (bias -3.7%, rms 10%) is attributed to the use of inaccurate surface albedo data. The sensitivity tests reveal the important role accurate, vertically resolved aerosol extinction data plays in tightening flux closure. This study also suggests that in the presence of a strongly absorbing substance, aircraft flux measurements from a stabilized platform have the potential to determine heating rate profiles. These measurement-based heating rate profiles provide useful data for heating rate closure studies and indirect estimates of single scattering albedo assumed in radiative transfer calculations.

Guan, Hong; Schmid, Beat; Bucholtz, Anthony; Bergstrom, Robert

2010-03-31

68

Scaling in situ cosmogenic nuclide production rates using analytical approximations to atmospheric cosmic-ray fluxes  

NASA Astrophysics Data System (ADS)

Several models have been proposed for scaling in situ cosmogenic nuclide production rates from the relatively few sites where they have been measured to other sites of interest. Two main types of models are recognized: (1) those based on data from nuclear disintegrations in photographic emulsions combined with various neutron detectors, and (2) those based largely on neutron monitor data. However, stubborn discrepancies between these model types have led to frequent confusion when calculating surface exposure ages from production rates derived from the models. To help resolve these discrepancies and identify the sources of potential biases in each model, we have developed a new scaling model based on analytical approximations to modeled fluxes of the main atmospheric cosmic-ray particles responsible for in situ cosmogenic nuclide production. Both the analytical formulations and the Monte Carlo model fluxes on which they are based agree well with measured atmospheric fluxes of neutrons, protons, and muons, indicating they can serve as a robust estimate of the atmospheric cosmic-ray flux based on first principles. We are also using updated records for quantifying temporal and spatial variability in geomagnetic and solar modulation effects on the fluxes. A key advantage of this new model (herein termed LSD) over previous Monte Carlo models of cosmogenic nuclide production is that it allows for faster estimation of scaling factors based on time-varying geomagnetic and solar inputs. Comparing scaling predictions derived from the LSD model with those of previously published models suggest potential sources of bias in the latter can be largely attributed to two factors: different energy responses of the secondary neutron detectors used in developing the models, and different geomagnetic parameterizations. Given that the LSD model generates flux spectra for each cosmic-ray particle of interest, it is also relatively straightforward to generate nuclide-specific scaling factors based on recently updated neutron and proton excitation functions (probability of nuclide production in a given nuclear reaction as a function of energy) for commonly measured in situ cosmogenic nuclides. Such scaling factors reflect the influence of the energy distribution of the flux folded with the relevant excitation functions. Resulting scaling factors indicate 3He shows the strongest positive deviation from the flux-based scaling, while 14C exhibits a negative deviation. These results are consistent with a recent Monte Carlo-based study using a different cosmic-ray physics code package but the same excitation functions.

Lifton, Nathaniel; Sato, Tatsuhiko; Dunai, Tibor J.

2014-01-01

69

Measurement of advective soil gas flux: Results of field and laboratory experiments with CO2  

SciTech Connect

We modified our multi-channel, steady-state flow-through (SSFT), soil-CO2 flux monitoring system to include an array of inexpensive pyroelectric non-dispersive infrared detectors for full-range (0-100%) coverage of CO2 concentrations without dilution, and a larger-diameter vent tube. We then conducted field testing of this system from late July through mid-September 2010 at the Zero Emissions Research and Technology (ZERT) project site located in Bozeman, MT, and subsequently, laboratory testing at the Pacific Northwest National Laboratory (PNNL) in Richland, WA using a flux bucket filled with dry sand. In the field, an array of twenty-five SSFT and three non-steady-state (NSS) flux chambers was installed in a 10x4 m area, the long boundary of which was directly above a shallow (2-m depth) horizontal injection well located 0.5 m below the water table. Two additional chambers (one SSFT and one NSS) were installed 10 m from the well for background measurements. Volumetric soil moisture sensors were installed at each SSFT chamber to measure mean levels in the top 0.15 m of soil. A total flux of 52 kg CO2 d-1 was injected into the well for 27 d and the efflux from the soil was monitored by the chambers before, during, and for 27 d after the injection. Overall, the results were consistent with those from previous years, showing a radial efflux pattern centered on a known “hot spot”, rapid responses to changes in injection rate and wind power, evidence for movement of the CO2 plume during the injection, and nominal flux levels from the SSFT chambers that were up to 6-fold higher than those measured by adjacent NSS chambers. Soil moisture levels varied during the experiment from moderate to near saturation with the highest levels occurring consistently at the hot spot. The effects of wind on measured flux were complex and decreased as soil moisture content increased. In the laboratory, flux bucket testing with the SSFT chamber showed large measured-flux enhancement due to the Venturi effect on the chamber vent, but an overall decrease in measured flux when wind also reached the sand surface. Flux-bucket tests at a high flux (comparable to that at the hot spot) also showed that the measured flux levels increase linearly with the chamber-flushing rate until the actual level is reached. At the SSFT chamber-flushing rate used in the field experiment the measured flux in the laboratory was only about a third of the actual flux. The ratio of measured to actual flux increased logarithmically as flux decreased, and reached parity at low levels typical of diffusive flux systems. Taken together, our results suggest that values for advective CO2 flux measured by SSFT and NSS chamber systems are likely to be significantly lower than the actual values due to back pressure developed in the chamber that diverts flux from entering the chamber. Chamber designs that counteract the back pressure and also avoid large Venturi effects associated with vent tubes, such as the SSFT with a narrow vent tube operated at a high chamber-flushing rate, are likely to yield flux measurements closer to the true values.

Amonette, James E.; Barr, Jonathan L.; Erikson, Rebecca L.; Dobeck, Laura M.; Barr, Jamie L.; Shaw, Joseph A.

2013-10-01

70

Error Evaluation of Methyl Bromide Aerodynamic Flux Measurements  

USGS Publications Warehouse

Methyl bromide volatilization fluxes were calculated for a tarped and a nontarped field using 2 and 4 hour sampling periods. These field measurements were averaged in 8, 12, and 24 hour increments to simulate longer sampling periods. The daily flux profiles were progressively smoothed and the cumulative volatility losses increased by 20 to 30% with each longer sampling period. Error associated with the original flux measurements was determined from linear regressions of measured wind speed and air concentration as a function of height, and averaged approximately 50%. The high errors resulted from long application times, which resulted in a nonuniform source strength; and variable tarp permeability, which is influenced by temperature, moisture, and thickness. The increase in cumulative volatilization losses that resulted from longer sampling periods were within the experimental error of the flux determination method.

Majewski, M.S.

1997-01-01

71

Intercalibration of benthic flux chambers I. Accuracy of flux measurements and influence of chamber hydrodynamics [review article  

NASA Astrophysics Data System (ADS)

The hydrodynamic properties and the capability to measure sediment-water solute fluxes, at assumed steady state conditions, were compared for three radically different benthic chamber designs: the “Microcosm”, the “Mississippi” and the “Göteborg” chambers. The hydrodynamic properties were characterized by mounting a PVC bottom in each chamber and measuring mixing time, diffusive boundary layer thickness (DBL thickness) shear velocity (u ?) , and total pressure created by the water mixing. The Microcosm had the most even distribution of DBL thickness and u ?, but the highest differential pressure at high water mixing rates. The Mississippi chamber had low differential pressures at high u ?. The Göteborg chamber was in between the two others regarding these properties. DBL thickness and u ? were found to correlate according to the following empirical formula: DBL=76.18(u ?) -0.933. Multiple flux incubations with replicates of each of the chamber types were carried out on homogenized, macrofauna-free sediments in four tanks. The degree of homogeneity was determined by calculating solute fluxes (of oxygen, silicate, phosphate and ammonium) from porewater profiles and by sampling for porosity, organic carbon and meiofauna. All these results, except meiofauna, indicated that there were no significant horizontal variations within the sediment in any of the parallel incubation experiments. The statistical evaluations also suggested that the occasional variations in meiofauna abundance did not have any influence on the measured solute fluxes. Forty-three microelectrode profiles of oxygen in the DBL and porewater were evaluated with four different procedures to calculate diffusive fluxes. The procedure presented by Berg, Risgaard-Petersen and Rysgaard, 1989 [Limnol. Oceanogr. 43, 1500] was found to be superior because of its ability to fit measured profiles accurately, and because it takes into consideration vertical zonation with different oxygen consumption rates in the sediment. During the flux incubations, the mixing in the chambers was replicated ranging from slow mixing to just noticeable sediment resuspension. In the “hydrodynamic characterizations” these mixing rates corresponded to average DBL thickness from 120 to 550 ?m, to u ? from 0.12 to 0.68 cm/s, and to differential pressures from 0-3 Pa. Although not directly transferable, since the incubations were done on a “real” sediment with a rougher surface while in the characterizations a PVC plate simulated the sediments surface, these data give ideas about the prevailing hydrodynamic condition in the chambers during the incubations. The variations in water mixing did not generate statistically significant differences between the chamber types for any of the measured fluxes of oxygen or nutrients. Consequently it can be concluded that, for these non-permeable sediments and so long as appropriate water mixing (within the ranges given above) is maintained, the type of stirring mechanism and chamber design used were not critical for the magnitude of the measured fluxes. The average measured oxygen flux was 11.2 ± 2.7 (from 40 incubations), while the diffusive flux calculated (from 43 profiles using the Berg et al., 1989 [Limnol. Oceanogr. 43, 1500] procedure) was 11.1 ± 3.0 mmol m -2 day -1. This strongly suggests that accurate oxygen flux measurements were obtained with the three types of benthic chambers used and that the oxygen uptake is diffusive.

Tengberg, A.; Stahl, H.; Gust, G.; Müller, V.; Arning, U.; Andersson, H.; Hall, P. O. J.

2004-01-01

72

Design of a differential radiometer for atmospheric radiative flux measurements  

SciTech Connect

The Hemispherical Optimized NEt Radiometer (HONER) is an instrument under development at the Los Alamos National Laboratory for deployment on an unmanned aerospace vehicle as part of the Atmospheric Radiation Measurements (ARM/UAV) program. HONER is a differential radiometer which will measure the difference between the total upwelling and downwelling fluxes and is intended to provide a means of measuring the atmospheric radiative flux divergence. Unlike existing instruments which measure the upwelling and downwelling fluxes separately, HONER will achieve an optical difference by chopping the two fluxes alternately onto a common pyroelectric detector. HONER will provide data resolved into two spectral bands; one covering the solar dominated region from less than 0.4 micrometer to approximately 4.5 micrometers and the other covering the region from approximately 4.5 micrometers to greater than 50 micrometers, dominated by thermal radiation. The means of separating the spectral regions guarantees seamless summation to calculate the total flux. The fields-of-view are near-hemispherical, upward and downward. The instrument can be converted, in flight, from the differential mode to absolute mode, measuring the upwelling and downwelling fluxes separately and simultaneously. The instrument also features continuous calibration from on-board sources. We will describe the design and operation of the sensor head and the on-board reference sources as well as the means of deployment.

LaDelfe, P.C.; Weber, P.G.; Rodriguez, C.W.

1994-11-01

73

Mammalian metabolite flux rates in a teleost: lactate and glucose turnover in tuna.  

PubMed

Lactate and glucose turnover rates were measured by bolus injection of [U-14C]lactate and [6-3H]glucose in cannulated lightly anesthetized skipjack tuna, Katsuwonus pelamis. Our goals were to find out whether the high rates of lactate clearance reported during recovery from burst swimming in tuna could be accounted for by high blood lactate fluxes; to extend the observed correlation between lactate turnover and lactate concentration in mammals to a nonmammalian system, and to assess the importance of lactate and glucose as metabolic fuels in tuna and to compare their flux rates with values reported for mammals. Measured lactate turnover rates ranged from 112 to 431 mumol X min-1 X kg-1 and were correlated with blood lactate concentration. Glucose turnover rate averaged 15.3 mumol X min-1 X kg-1. When correcting for body mass and temperature, skipjack tuna has at least as high or even higher lactate turnover rates than those recorded for mammals. Tuna glucose turnover rate is similar to that of mammals but much higher than levels found in other teleosts. Even the highest lactate turnover rate measured in tuna cannot fully account for the rate of blood lactate clearance observed during recovery, suggesting that some of the lactate produced in skeletal muscle must be metabolized in situ. After injection of [U-14C]lactate, less than 5% of the total blood activity was recovered in glucose, suggesting that the Cori cycle is not an important pathway of lactate metabolism in tuna. PMID:3953854

Weber, J M; Brill, R W; Hochachka, P W

1986-03-01

74

Fast Flux Test Facility passive safety reactivity feedback measurements  

Microsoft Academic Search

A series of experiments conducted in the Fast Flux Test Facility (FFTF) measured the reactivity change between approximately 200 reactor states. The test data have been evaluated to determine the thermal hydraulic parameters of the reactor at those states. Auxiliary measurements have been analyzed to convert the measured control rod position changes to reactivity and to correct for burnup effects.

B. J. Knutson; R. A. Harris; D. H. Nguyen; R. P. Omberg

1988-01-01

75

Hybrid heat flux measurement system for solar central receiver evaluation  

Microsoft Academic Search

A hybrid heat flux measurement system has been designed, built and mounted on top of the SSPS-CRS tower at the Plataforma Solar de Almería (PSA) to measure the incident solar power that is concentrated by a heliostat field on the flat aperture of a central receiver. This device is composed of two measurement systems, one direct and the other indirect.

J. Ballestrín; R. Monterreal

2004-01-01

76

Photoabsorption cross section of CH3CN - Photodissociation rates by solar flux and interstellar radiation  

NASA Technical Reports Server (NTRS)

The photoabsorption cross section of CH2CN vapor was measured in the 106-180 nm region using synchrotron radiation as a light source. The cross section and the quantum yield for the production of CN (A, B-X) fluorescence were measured and were used to infer the photodissociation cross section of CH3CN. The cross sections were used to calculate the photodissociation rates of CH3CN by the solar flux and by the interstellar radiation. In both the stratosphere and the troposphere, the solar photodissociation of CH3CN is negligible in comparison with chemical degradation.

Suto, M.; Lee, L. C.

1985-01-01

77

Solar Model Parameters and Direct Measurements of Solar Neutrino Fluxes  

E-print Network

We explore a novel possibility of determining the solar model parameters, which serve as input in the calculations of the solar neutrino fluxes, by exploiting the data from direct measurements of the fluxes. More specifically, we use the rather precise value of the $^8B$ neutrino flux, $\\phi_B$ obtained from the global analysis of the solar neutrino and KamLAND data, to derive constraints on each of the solar model parameters on which $\\phi_B$ depends. We also use more precise values of $^7Be$ and $pp$ fluxes as can be obtained from future prospective data and discuss whether such measurements can help in reducing the uncertainties of one or more input parameters of the Standard Solar Model.

Abhijit Bandyopadhyay; Sandhya Choubey; Srubabati Goswami; S. T. Petcov

2006-08-30

78

High rates of energy expenditure and water flux in free-ranging Point Reyes mountain beavers Aplodontia rufa phaea  

USGS Publications Warehouse

We measured water flux and energy expenditure in free-ranging Point Reyes mountain beavers Aplodontia rufa phaea by using the doubly labeled water method. Previous laboratory investigations have suggested weak urinary concentrating ability, high rates of water flux, and low basal metabolic rates in this species. However, free-ranging measurements from hygric mammals are rare, and it is not known how these features interact in the environment. Rates of water flux (210 ?? 32 mL d-1) and field metabolic rates (1,488 ?? 486 kJ d-1) were 159% and 265%, respectively, of values predicted by allometric equations for similar-sized herbivores. Mountain beavers can likely meet their water needs through metabolic water production and preformed water in food and thus remain in water balance without access to free water. Arginine-vasopressin levels were strongly correlated with rates of water flux and plasma urea : creatinine ratios, suggesting an important role for this hormone in regulating urinary water loss in mountain beavers. High field metabolic rates may result from cool burrow temperatures that are well below lower critical temperatures measured in previous laboratory studies and suggest that thermoregulation costs may strongly influence field energetics and water flux in semifossorial mammals. ?? 2007 by The University of Chicago. All rights reserved.

Crocker, D. E.; Kofahl, N.; Fellers, G. D.; Gates, N. B.; Houser, D. S.

2007-01-01

79

Flux measurement and modeling in a typical mediterranean vineyard  

NASA Astrophysics Data System (ADS)

Vineyard ecosystems are typical in the Mediterranean area, since wine is one of the most important economic sectors. Nevertheless, only a few studies have been conducted to investigate the interactions between this kind of vegetation and the atmosphere. These information are important both to understand the behaviour of such ecosystems in different environmental conditions, and are crucial to parameterize crop and flux simulation models. Combining direct measurements and modelling can obtain reliable estimates of surface fluxes and crop evapotranspiration. This study would contribute both to (1) directly measure energy fluxes and evapotranspiration in a typical Mediterranean vineyard, located in the South of Sardinia (Italy), through the application of the Eddy Covariance micrometeorological technique and to (2) evaluate the land surface model ACASA (Advanced-Canopy-Atmosphere-Soil Algorithm) in simulating energy fluxes and evapotranspiration over vineyard. Independent datasets of direct measurements were used to calibrate and validate model results during the growing period. Statistical analysis was performed to evaluate model performance and accuracy in predicting surface fluxes. Results will be showed as well as the model capability to be used for future studies to predict energy fluxes and crop water requirements under actual and future climate.

Marras, Serena; Bellucco, Veronica; Pyles, David R.; Falk, Matthias; Sirca, Costantino; Duce, Pierpaolo; Snyder, Richard L.; Tha Paw U, Kyaw; Spano, Donatella

2014-05-01

80

Accuracy of quantum sensors measuring yield photon flux and photosynthetic photon flux  

NASA Technical Reports Server (NTRS)

Photosynthesis is fundamentally driven by photon flux rather than energy flux, but not all absorbed photons yield equal amounts of photosynthesis. Thus, two measures of photosynthetically active radiation have emerged: photosynthetic photon flux (PPF), which values all photons from 400 to 700 nm equally, and yield photon flux (YPF), which weights photons in the range from 360 to 760 nm according to plant photosynthetic response. We selected seven common radiation sources and measured YPF and PPF from each source with a spectroradiometer. We then compared these measurements with measurements from three quantum sensors designed to measure YPF, and from six quantum sensors designed to measure PPF. There were few differences among sensors within a group (usually <5%), but YPF values from sensors were consistently lower (3% to 20%) than YPF values calculated from spectroradiometric measurements. Quantum sensor measurements of PPF also were consistently lower than PPF values calculated from spectroradiometric measurements, but the differences were <7% for all sources, except red-light-emitting diodes. The sensors were most accurate for broad-band sources and least accurate for narrow-band sources. According to spectroradiometric measurements, YPF sensors were significantly less accurate (>9% difference) than PPF sensors under metal halide, high-pressure sodium, and low-pressure sodium lamps. Both sensor types were inaccurate (>18% error) under red-light-emitting diodes. Because both YPF and PPF sensors are imperfect integrators, and because spectroradiometers can measure photosynthetically active radiation much more accurately, researchers should consider developing calibration factors from spectroradiometric data for some specific radiation sources to improve the accuracy of integrating sensors.

Barnes, C.; Tibbitts, T.; Sager, J.; Deitzer, G.; Bubenheim, D.; Koerner, G.; Bugbee, B.; Knott, W. M. (Principal Investigator)

1993-01-01

81

Constraining isoprene emission factors using airborne flux measurements during CABERNET  

NASA Astrophysics Data System (ADS)

An aircraft flux study was conducted to assess biogenic volatile organic compound (BVOC) emissions from California ecosystems targeting oak woodlands and isoprene for most transects. The direct eddy covariance approach featured high speed proton transfer reaction mass spectrometry onboard a CIRPAS (Center for Interdisciplinary Remotely-Piloted Aircraft Studies) Twin Otter aircraft during June 2011 as part of the CABERNET (California Airborne BVOC Emission Research in Natural Ecosystem Transects) project. Isoprene fluxes were calculated using wavelet analysis and scaled to surface fluxes using a divergence term obtained by measuring fluxes at multiple altitudes over homogenous oak terrain. By normalization of fluxes to standard temperature and photosynthetically active radiation levels using standard BVOC modeling equations, the resulting emission factors could be directly compared with those used by MEGAN (Model of Emissions of Gases and Aerosols from Nature) and BEIGIS (Biogenic Emission Inventory Geographic Information System) models which are the most commonly used BVOC emission models for California. As expected, oak woodlands were found to be the dominant source of isoprene in all areas surrounding and in the Central Valley of California. The airborne fluxes averaged to 2 km spatial resolution matched remarkably well with current oak woodland distributions driving the models and hence the correspondence of modeled and aircraft derived emission factors was also good, although quantitative differences were encountered depending on the region and driving variables used. Fluxes measured from aircraft proved to be useful for the improvement of the accuracy of modeled predictions for isoprene and other important ozone and aerosol precursor compounds. These are the first regional isoprene flux measurements using direct eddy covariance on aircraft.

Misztal, P. K.; Karl, T.; Jiang, X.; Avise, J. C.; Scott, K.; Jonsson, H.; Guenther, A. B.; Goldstein, A. H.

2012-12-01

82

Uncertainties Associated with Flux Measurements Due to Heterogeneous Contaminant Distributions  

EPA Science Inventory

Mass flux and mass discharge measurements at contaminated sites have been applied to assist with remedial management, and can be divided into two broad categories: point-scale measurement techniques and pumping methods. Extrapolation across un-sampled space is necessary when usi...

83

SO2 flux measurements at Mount Etna (Sicily)  

Microsoft Academic Search

Since 1987, over 220 measurements of the SO2 flux at Mount Etna have been carried out using a correlation spectrometer (COSPEC) with different measuring techniques (mainly with COSPEC mounted on ground-based vehicle). This paper reports and analyzes the data obtained between October 1987 and December 1991. During this period, three distinct time intervals characterized by particular SO2 emission patterns were

Tommaso Caltabiano; Romolo Romano; Gennaro Budetta

1994-01-01

84

Turbogenerator field winding shorted turn detection by AC flux measurement  

Microsoft Academic Search

A new testing technique for detecting shorted turns in turbogenerator rotors is presented, where the field winding is supplied with power frequency voltage as for a normal impedance measurement. The circumferential flux is measured in the centerline of all slot wedges and compared between individual poles by amplitude and\\/or phase. When the rotor is removed, the turn short can be

E. Woschnagg

1994-01-01

85

On the heating of the outer radiation belt to produce high fluxes of relativistic electrons: Measured heating rates at geosynchronous orbit for high-speed stream-driven storms  

Microsoft Academic Search

The heating rate of the outer electron radiation belt at geosynchronous orbit is determined for the interval from 36 to 72 h after the onset of high-speed stream-driven storms. Multisatellite measurements of the radiation belt temperature are used for 93 high-speed stream-driven storms. During the storms, the outer electron radiation belt temperature changes from ?120 keV to ?190 keV. The

Joseph E. Borovsky; Michael H. Denton

2010-01-01

86

On the heating of the outer radiation belt to produce high fluxes of relativistic electrons: Measured heating rates at geosynchronous orbit for high-speed stream-driven storms  

Microsoft Academic Search

The heating rate of the outer electron radiation belt at geosynchronous orbit is determined for the interval from 36 to 72 h after the onset of high-speed stream-driven storms. Multisatellite measurements of the radiation belt temperature are used for 93 high-speed stream-driven storms. During the storms, the outer electron radiation belt temperature changes from ˜120 keV to ˜190 keV. The

Joseph E. Borovsky; Michael H. Denton

2010-01-01

87

Analysis of field measurements of carbon dioxide and water vapor fluxes  

NASA Technical Reports Server (NTRS)

Analysis of the field measurements of carbon dioxide and water vapor fluxes is discussed. These data were examined in conjunction with reflectance obtained from helicopter mounted Modular Multiband Radiometer. These measurements are representative of the canopy scale (10 to 100 m)(exp 2) and provide a good basis for investigating the hypotheses/relationship potentially useful in remote sensing applications. All the micrometeorological data collected during FIFE-89 were processed and fluxes of CO2, water vapor, and sensible heat were calculated. Soil CO2 fluxes were also estimated. Employing these soil CO2 flux values, in conjunction with micrometeorological measurements, canopy photosynthesis is being estimated. A biochemical model of leaf photosynthesis was adapted to the prairie vegetation. The modeled leaf photosynthesis rates were scaled up to the canopy level. This model and a multiplicative stomatal conductance model are also used to calculate canopy conductance.

Verma, Shashi B.

1991-01-01

88

Surface Catalysis and Oxidation on Stagnation Point Heat Flux Measurements in High Enthalpy Arc Jets  

NASA Technical Reports Server (NTRS)

Heat flux sensors are routinely used in arc jet facilities to determine heat transfer rates from plasma plume. The goal of this study is to assess the impact of surface composition changes on these heat flux sensors. Surface compositions can change due to oxidation and material deposition from the arc jet. Systematic surface analyses of the sensors were conducted before and after exposure to plasma. Currently copper is commonly used as surface material. Other surface materials were studied including nickel, constantan gold, platinum and silicon dioxide. The surfaces were exposed to plasma between 0.3 seconds and 3 seconds. Surface changes due to oxidation as well as copper deposition from the arc jets were observed. Results from changes in measured heat flux as a function of surface catalycity is given, along with a first assessment of enthalpy for these measurements. The use of cupric oxide is recommended for future heat flux measurements, due to its consistent surface composition arc jets.

Nawaz, Anuscheh; Driver, David M.; Terrazas-Salinas

2013-01-01

89

Monitoring of MNSR operation by measuring subcritical photoneutron flux.  

PubMed

Passive nondestructive assay methods are used to monitor the reactor's operation. It is required for nuclear regulatory, calculation validation and safeguards purposes. So, it plays a vital role in the safety and security of the nuclear plants. The possibility of MNSR operation monitoring by measuring the subcritical state photoneutron flux were investigated in this work. The photoneutron flux is induced by the fuels hard gamma radiation in the beryllium reflector. Theoretical formulation and experimental tests were performed. The results show that within a specified cooling time range, the photoneutron flux is induced by a single dominant hard gamma emitter such as (117)Cd (activation product) and (140)Ba ((140)La fission product). This phenomenon was utilized to monitor the cooling time and the operation neutron flux during the last campaign. Thus a passive nondestructive assay method is proposed with regard to the reactor operation's monitoring. PMID:21168337

Haddad, Kh; Alsomel, N

2011-03-01

90

Intercomparison of gas analyzers for methane flux measurements  

NASA Astrophysics Data System (ADS)

Four gas analyzers, capable of measuring methane concentration at a response time necessary for eddy covariance flux measurements, were operated in parallel for about six months between March and August 2010. Their reliability, need of maintenance, user friendliness, data coverage, and data quality were evaluated. The primary aim of this campaign was to provide an instrumentation suggestion for the European Research Infrastructure ICOS (Integrated Carbon Observation System). The instruments used were TGA100A (Campbell Scientific Inc.), RMT-200 (Los Gatos Research Inc.) , G1301-f (Picarro Inc.), and LI-7700 (Li-Cor Inc.). The last one, LI-7700, was a prototype of a later commercialized open path analyzer. The other instruments were closed path analyzers. The measurement site is an oligotrophic open fen Siikaneva, located in southern Finland. The site provides spatially quite uniform methane flux within the footprint. The methane flux rises in the spring, peaks in early August and falls down during the autumn. This provides excellent opportunity to study the performance of the analyzers at different CH4 flux levels from near zero up to about 5 mg m-2 h-1. The preliminary results show great similarity among the instruments in both concentrations and fluxes. Detailed numbers of the measurement characteristics will be provided later. The reliability and need of maintenance are difficult to evaluate quantitatively during that short period.

Haapanala, S.; Rinne, J.; Vesala, T.

2010-12-01

91

Primary Cosmic Ray Proton Flux Measured by AMS-02  

E-print Network

The Alpha Magnetic Spectrometer (AMS-02) is a high energy particle detector designed to study origin and nature of cosmic rays up to a few TV from space. It was installed on the International Space Station (ISS) on May 19, 2011. During the first two years of operation AMS-02 performed precise measurements of the proton flux. In the low rigidity range, from 1 GV to 20 GV, the proton flux was daily measured with a statistical error less than 1%. In the same rigidity range a gradual decrease due to Solar modulation effect and transit variations due to Solar Flares and Coronal Mass Ejection were also observed. In the rigidity range from 20 GV up to 100 GV instead, AMS-02 data show no drastic variation and the results are consistent with other experiments. Above 100 GV, AMS-02 proton flux exhibits a single power low behavior with no fine structures nor brakes.

C. Consolandi; on Behalf of the AMS-02 Collaboration

2014-02-03

92

Primary Cosmic Ray Proton Flux Measured by AMS-02  

E-print Network

The Alpha Magnetic Spectrometer (AMS-02) is a high energy particle detector designed to study origin and nature of cosmic rays up to a few TV from space. It was installed on the International Space Station (ISS) on May 19, 2011. During the first two years of operation AMS-02 performed precise measurements of the proton flux. In the low rigidity range, from 1 GV to 20 GV, the proton flux was daily measured with a statistical error less than 1%. In the same rigidity range a gradual decrease due to Solar modulation effect and transit variations due to Solar Flares and Coronal Mass Ejection were also observed. In the rigidity range from 20 GV up to 100 GV instead, AMS-02 data show no drastic variation and the results are consistent with other experiments. Above 100 GV, AMS-02 proton flux exhibits a single power low behavior with no fine structures nor brakes.

Consolandi, C

2014-01-01

93

The impact of high-flux dialysis on mortality rates in incident and prevalent hemodialysis patients  

PubMed Central

Background/Aims The effect of high-flux (HF) dialysis on mortality rates could vary with the duration of dialysis. We evaluated the effects of HF dialysis on mortality rates in incident and prevalent hemodialysis (HD) patients. Methods Incident and prevalent HD patients were selected from the Clinical Research Center registry for end-stage renal disease (ESRD), a Korean prospective observational cohort study. Incident HD patients were defined as newly diagnosed ESRD patients initiating HD. Prevalent HD patients were defined as patients who had been receiving HD for > 3 months. The primary outcome measure was all-cause mortality. Results This study included 1,165 incident and 1,641 prevalent HD patients. Following a median 24 months of follow-up, the mortality rates of the HF and low-flux (LF) groups did not significantly differ in the incident patients (hazard ratio [HR], 1.046; 95% confidence interval [CI], 0.592 to 1.847; p = 0.878). In the prevalent patients, HF dialysis was associated with decreased mortality compared with LF dialysis (HR, 0.606; 95% CI, 0.416 to 0.885; p = 0.009). Conclusions HF dialysis was associated with a decreased mortality rate in prevalent HD patients, but not in incident HD patients. PMID:25378976

Kim, Hyung Wook; Kim, Su-Hyun; Kim, Young Ok; Jin, Dong Chan; Song, Ho Chul; Choi, Euy Jin; Kim, Yong-Lim; Kim, Yon-Su; Kang, Shin-Wook; Kim, Nam-Ho; Yang, Chul Woo

2014-01-01

94

Direct Measurement of Turbulent Particle and Gas Fluxes by Eddy Covariance Technique  

NASA Astrophysics Data System (ADS)

Direct Measurement of Turbulent Particle and Gas Fluxes by Eddy Covariance Technique Fumiyoshi KONDO (The University of Tokyo) Frank GRIESSBAUM (Universität Münster) Osamu TSUKAMOTO (Okayama University) Mitsuo UEMATSU (The University of Tokyo) The oceans play major key roles in global energy transport, element cycles, and atmospheric radiation balance. The study of the processes at the interface of ocean and atmosphere is essential to develop profound understanding of the mechanisms driving ocean-atmosphere interaction and climate. Eddy covariance technique is the only direct measurement of air-sea particle and gas fluxes. This technique has little assumption (constant flux layer and steady state), and may evaluate small spatial and temporal particle and gas fluxes. For these reasons, we hope that the eddy covariance technique investigates uncertain processes that control the air-sea particle (aerosol) and gas (CO2) fluxes. The understanding of processes controlling both the CO2 uptake to the ocean and the oceans as major source of aerosols is vital for quantifying the role of the global oceans in the climate system. We developed the simultaneous measurement system of turbulent particle and gas fluxes by eddy covariance technique and installed with ship motion correction system on the top of the foremast of R/V Hakuho-Maru and Mirai. The turbulent flux system on the top of the foremast consisted of a sonic anemometer-thermometer (Gill, HS-50), an infrared CO2/H2O gas analyzer (LI-COR, LI-7500), a water-based condensation particle counter (TSI, WCPC3785), and Fog Monitor (Droplet Measurement, FM-100). The ship motion correction system consisted of a three-axis accelerometer and a three-axis rate gyro (Systron Donner, MotionPak II). The sonic anemometer measures three-dimensional wind components relative to the ship including apparent wind velocity due to the ship motion. Then, the ship motion correction system measures the ship motions by time integral of accelerometer and rate gyro. The turbulent flux system on the top of the foremast is capable to simultaneously measure the turbulent flux of the CO2 and H2O gases, fine aerosols (5 nm - 3 ?m diameters), and fog water droplets (2 ?m - 50 ?m diameters). Analog and digital output signals from both systems are sampled at 10 Hz by a PC-based data logging systems. In this study, we will present the direct flux measurement system and discuss results of air-sea particle and CO2 fluxes directly evaluated by the eddy covariance technique over the open ocean.

Kondo, F.; Griessbaum, F.; Tsukamoto, O.; Uematsu, M.

2010-12-01

95

Multiple-Point Mass Flux Measurement System Using Rayleigh Scattering  

NASA Technical Reports Server (NTRS)

A multiple-point Rayleigh scattering diagnostic is being developed to provide mass flux measurements in gas flows. Spectroscopic Rayleigh scattering is an established flow diagnostic that has the ability to provide simultaneous density, temperature, and velocity measurements. Rayleigh scattered light from a focused 18 Watt continuous-wave laser beam is directly imaged through a solid Fabry-Perot etalon onto a CCD detector which permits spectral analysis of the light. The spatial resolution of the measurements is governed by the locations of interference fringes, which can be changed by altering the etalon characteristics. A prototype system has been used to acquire data in a Mach 0.56 flow to demonstrate feasibility of using this system to provide mass flux measurements. Estimates of measurement uncertainty and recommendations for system improvements are presented

Mielke, Amy F.; Elam, Kristie A.; Clem, Michelle M.

2009-01-01

96

Vertical helicity flux in atmospheric vortices as a measure of their intensity  

NASA Astrophysics Data System (ADS)

It is suggested that the downward helicity flux (through the upper boundary of the viscous turbulent boundary layer) be treated as a measure of the intensity of atmospheric vortices, including tropical cyclones, tornadoes, and dust devils. As follows immediately from the general helicity balance equation known in the literature, this flux is determined by the product of the cubed maximum wind speed and the width of the strip swept by the maximum wind during vortex movement. For intense vortices in their steady-state, mature stage, this helicity flux can also serve as a measure of the rate of helicity destruction by the forces of viscous turbulent friction. Examples of applying the introduced notion to the diagnostics of tornadoes and their classification according to a destructive force are given. A comparative analysis (according to helicity flux values) of dust devils on the Earth and Mars, on the one hand, and tornadoes, on the other, is presented.

Kurgansky, M. V.

2008-02-01

97

Latent heat fluxes and TKE dissipation rates over complex terrain from airborne lidar observations  

NASA Astrophysics Data System (ADS)

The combination of a water vapour and a wind lidar on an aircraft is an interesting new tool that allows to measure latent heat flux profiles and the small- to mesoscale variability beneath the aircraft along the flight track. During the Convective and Orographically-induced Precipitation Study (COPS) in July 2007 over the Black Forest low-mountains in south-west Germany, a differential absorption lidar (DIAL) and a Doppler wind lidar were collocated nadir-viewing onboard the DLR Falcon research aircraft. One of the main goals was to measure the vertical humidity transport within the convective boundary layer (CBL) over the Rhine valley and the Black Forest on days when deep convection was expected to be mainly forced by the local orography and surface humidity. From the remotely-sensed wind and water vapour fluctuations at multiple heights within the CBL, a representative latent heat flux profile can be obtained from a single over-flight of the area under investigation using the eddy-correlation technique. The lidars' horizontal and vertical resolution is 200 m, which is just sufficient to resolve the dominant contributions to the flux, as parallel higher-resolved in-situ measurements by another research aircraft show. The flights were performed early enough, around noon, in order to avoid too many clouds that obstruct the lidar measurements. However, scattered fair-weather cumuli, as well as the presence of instrumental noise in the lidar signals do not significantly hinder the flux retrieval, as the comparisons with the in-situ measurements demonstrated. The presentation will highlight methodical advances, accuracy assessments, validations by the collocated in-situ aircraft measurements over the mountains, as well as the study of a post-frontal situation in which the latent heat flux played a key role in humidifying the boundary layer. On this exemplary day, 30. July 2007, the lidar-derived latent heat fluxes in the CBL over the mountains vary between 100 - 500 W/m2 on parallel flight tracks but are roughly constant with height. The observed positive fluxes moisten the growing CBL by upward transport of humidity from surface evaporation due to previous days' rain. However, they were probably too low to generate the deep convection predicted on that particular day. Fourier spectra of the wind lidar's vertical velocity measurements in the mid-CBL enable to estimate the dissipation rate of turbulent kinetic energy (TKE) following the Kolmogorov-Obukhov empirical relationship in the inertial subrange. It amounts to 5•10-4 m2 s-3 in the Rhine Valley between 400 and 1200 m height above ground, using a Kolmogorov constant of 0.55, valid for one-dimensional velocity spectra. This is in accordance with the mid-CBL results of the in-situ vertical velocity spectra in the valley. Over the mountains, the in-situ spectra show higher levels, as expected due to higher TKE, and bring dissipation rates of up to 10-3 m2 s-3.

Kiemle, C.; Wirth, M.; Rahm, S.; Corsmeier, U.

2012-04-01

98

Some Recent Secondary Production Measurements for Neutrino Flux Determination  

NASA Astrophysics Data System (ADS)

Recent measurements of meson production in proton-nucleus interactions have made possible reliable neutrino flux determinations at modern neutrino experiments. This article discusses preliminary results from the HARP, MIP, and E910 are discussed along with some of their implications for the MINOS, K2K, and MiniBooNE neutrino experiments.

Mills, Geoffrey B.

2011-12-01

99

A PROBLEM WITH FLUX CHAMBER MEASUREMENTS OF BIOGENIC SULFUR EMISSIONS  

EPA Science Inventory

Problems associated with identifying and quantifying factors that influence liquid-phase controlled evolution of hydrogen sulfide and organic sulfides through the air-water interface are briefly reviewed. It was found that at present flux chamber measurements of the release of th...

100

Estimation of wet surface evaporation from sensible heat flux measurements  

Microsoft Academic Search

A new method is proposed to estimate wet surface evaporation by means of measurements of sensible heat flux and of air temperature, relative humidity, and wind speed at one level only. This formulation is made possible by the linearization of the Bowen ratio, a common assumption in other methods, such as Penman's model and its derivatives. The method will be

Nikki Vercauteren; Elie Bou-Zeid; Hendrik Huwald; Marc B. Parlange; Wilfried Brutsaert

2009-01-01

101

Testing Geological Models with Terrestrial Antineutrino Flux Measurements  

E-print Network

Uranium and thorium are the main heat producing elements in the earth. Their quantities and distributions, which specify the flux of detectable antineutrinos generated by the beta decay of their daughter isotopes, remain unmeasured. Geological models of the continental crust and the mantle predict different quantities and distributions of uranium and thorium. Many of these differences are resolvable with precision measurements of the terrestrial antineutrino flux. This precision depends on both statistical and systematic uncertainties. An unavoidable background of antineutrinos from nuclear reactors typically dominates the systematic uncertainty. This report explores in detail the capability of various operating and proposed geo-neutrino detectors for testing geological models.

Dye, Steve

2009-01-01

102

Testing Geological Models with Terrestrial Antineutrino Flux Measurements  

E-print Network

Uranium and thorium are the main heat producing elements in the earth. Their quantities and distributions, which specify the flux of detectable antineutrinos generated by the beta decay of their daughter isotopes, remain unmeasured. Geological models of the continental crust and the mantle predict different quantities and distributions of uranium and thorium. Many of these differences are resolvable with precision measurements of the terrestrial antineutrino flux. This precision depends on both statistical and systematic uncertainties. An unavoidable background of antineutrinos from nuclear reactors typically dominates the systematic uncertainty. This report explores in detail the capability of various operating and proposed geo-neutrino detectors for testing geological models.

Steve Dye

2009-12-14

103

A Novel Detector for High Neutron Flux Measurements  

SciTech Connect

Measuring alpha particles from a neutron induced break-up reaction with a mass spectrometer can be an excellent tool for detecting neutrons in a high neutron flux environment. Break-up reactions of {sup 6}Li and {sup 12}C can be used in the detection of slow and fast neutrons, respectively. A high neutron flux detection system that integrates the neutron energy sensitive material and helium mass spectrometer has been developed. The description of the detector configuration is given and it is soon to be tested at iThemba LABS, South Africa.

Singo, T. D.; Wyngaardt, S. M. [Department of Physics, University of Stellenbosch, Private bag X1, Matieland, Stellenbosch (South Africa); Papka, P. [Department of Physics, University of Stellenbosch, Private bag X1, Matieland, Stellenbosch (South Africa); Nuclear Physics group, iThemba labs, P. O. Box 722, Somerset West 7129 (South Africa); Dobson, R. T. [Department of Mechanical and Mechatronic Engineering, University of Stellenbosch, Private bag X1, Matieland, Stellenbosch (South Africa)

2010-01-05

104

Advances in Air-Sea Flux Measurement by Eddy Correlation  

NASA Astrophysics Data System (ADS)

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.

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

2014-09-01

105

Evaluation of the flux gradient technique for measurement of ozone surface fluxes over snowpack at Summit, Greenland  

Microsoft Academic Search

A multi-step procedure for investigating ozone surface fluxes over polar snow by the tower gradient method was developed and evaluated. These measurements were then used to obtain five months (April-August 2004) of turbulent ozone flux data at the Summit research camp located in the center of the Greenland ice shield. Turbulent fluxes were determined by the gradient method incorporating tower

F. Bocquet; D. Helmig; B. A. van Dam; C. W. Fairall

2011-01-01

106

Using sea ice to measure vertical heat flux in the ocean  

Microsoft Academic Search

Results of an experiment performed at drifting ice station FRAM I in the Arctic Ocean northwest of Spitzbergen during March-May 1979 indicate that sensible heat flux from the ocean to the ice cover was less than 2 W m2. The estimate is based on measurements of temperature gradient, growth rate and salinity of young sea ice. Uncertainty in the magnitude

Miles G. McPhee; Norbert Untersteiner

1982-01-01

107

MEASUREMENT OF TOTAL RADIANT FLUX OF UV LEDS  

Microsoft Academic Search

We have developed a source-based method and a detector-based method for total radiant flux measurement for deep-blue and UV LEDs, using a 2.5 m integrating sphere. Several UV LEDs with peak wavelengths of 375 nm and 390 nm were measured using both the source-based method and the detector-based method with a relative expanded uncertainty (k=2) of ~6 % and ~5

108

Measuring Regional CO2 Fluxes Using a Lagrangian Approach  

Microsoft Academic Search

The difficulty of measuring regional fluxes of CO2 has limited our understanding of the global carbon budget and the processes controlling carbon exchange across politically relevant spatial scales. A Lagrangian experiment was conducted over Iowa on June 19, 2007 as part of the North American Carbon Program's Mid-Continent Intensive using a light-weight, cost-effective aircraft to measure a net drawdown of

D. K. Martins; C. Sweeney; B. H. Stirm; P. B. Shepson

2008-01-01

109

Ecosystem photosynthesis inferred from measurements of carbonyl sulphide flux  

NASA Astrophysics Data System (ADS)

Limited understanding of carbon dioxide sinks and sources on land is often linked to the inability to distinguish between the carbon dioxide taken up by photosynthesis, and that released by respiration. Carbonyl sulphide, a sulphur-containing analogue of carbon dioxide, is also taken up by plants, and could potentially serve as a powerful proxy for photosynthetic carbon dioxide uptake, which cannot be directly measured above the leaf scale. Indeed, variations in atmospheric concentrations of carbonyl sulphide are closely related to those of carbon dioxide at regional, local and leaf scales. Here, we use eddy covariance and laser spectroscopy to estimate the net exchange of carbon dioxide and carbonyl sulphide across three pine forests, a cotton field and a wheat field in Israel. We estimate gross primary productivity--a measure of ecosystem photosynthesis--directly from the carbonyl sulphide fluxes, and indirectly from carbon dioxide fluxes. The two estimates agree within an error of +/-15%. The ratio of carbonyl sulphide to carbon dioxide flux at the ecosystem scale was consistent with the variability in mixing ratios observed on seasonal timescales in the background atmosphere. We suggest that atmospheric measurements of carbonyl sulphide flux could provide an independent constraint on estimates of gross primary productivity, key to projecting the response of the land biosphere to climate change.

Asaf, David; Rotenberg, Eyal; Tatarinov, Fyodor; Dicken, Uri; Montzka, Stephen A.; Yakir, Dan

2013-03-01

110

Upward shower rates at neutrino telescopes directly determine the neutrino flux  

SciTech Connect

We show that the rate for upward showers from an isotropic cosmic neutrino flux at neutrino telescopes like IceCube is independent of the neutrino-nucleon cross section. For bins that span a relatively narrow range in energy, neither scaling the cross section, nor changing its power-law energy behavior affects the upward shower rate, which depends only on the flux. The neutrino flux can be completely known since its spectral shape can be determined by comparing the rates in neighboring bins. We also show that the downward shower rate varies linearly with cross section with a proportionality constant determined by the energy dependence of the cross section, independent of the power-law behavior of the flux. The normalization and energy dependence of the cross section can be found by comparing the downward rates in neighboring bins.

Hussain, S. [Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States); Marfatia, D.; McKay, D. W. [Department of Physics and Astronomy, University of Kansas, Lawrence, KS 66045 (United States)

2008-05-15

111

A mobile detector for measurements of the atmospheric muon flux  

NASA Astrophysics Data System (ADS)

Measurements of the underground atmospheric muon flux are important in order to determine accurately the overburden in mwe (meter water equivalent) of an underground laboratory for appreciating which kind of experiments are feasible for that location. Slanic- Prohava is one of the 7 possible locations for the European large underground experiment LAGUNA (Large Apparatus studying Grand Unification and Neutrino Astrophysics). A mobile device consisting of 2 scintillator plates (?0.9 m2, each) one above the other and measuring in coincidence, was set-up for determining the muon flux. The detector it is installed on a van which facilitates measurements on different positions at the surface or in the underground and it is in operation since autumn 2009. The measurements of muon fluxes presented in this contribution have been performed in the underground salt mine Slanic-Prahova, Romania, where IFIN-HH has built a low radiation level laboratory, and at the surface on different sites of Romania, at different elevations from 0 m a.s.l up to 655 m a.s.l. Based on our measurements we can say that Slanic site is a feasible location for LAGUNA in Unirea salt mine at a water equivalent depth of 600 mwe. The results have been compared with Monte-Carlo simulations performed with the simulation codes CORSIKA and MUSIC.

Mitrica, B.; Brancus, I. M.; Margineanu, R.; Petcu, M.; Dima, M.; Sima, O.; Haungs, A.; Rebel, H.; Petre, M.; Toma, G.; Saftoiu, A.; Apostu, A.

2011-04-01

112

Uncertainty and heterogeneity for eddy covariance flux measurement  

NASA Astrophysics Data System (ADS)

Under the issues of global climate changing, monitoring CO2 flux including sensible and latent heat flux has been carried out using eddy covariance (EC) method, and accumulating those data are available to investigate the issues over the worldwide. However, it may be difficult to make use of the data to explore ecosystem intercomparison, model development, and model-data synthesis, because of the lack of uncertainty information about EC measurements. In this study, we calculated the fractional uncertainty ? and estimated the expected fractional uncertainty ? using data collected over various land covers and at different instrumental heights. We also investigated ? properties by spatiotemporal scale and flux averaging timescale ?. We demonstrated that when ? is estimated by the least median of squares method to filter outliers, its values are stable and uniform regardless of flux type, spatiotemporal scale and land covers. Using the stability, uniformity, and randomness of ?, we determined those baseline as a function of ?: ?base=??-1/2, and the heterogeneity scale parameter ? as the normalized discrepancy between the baseline and the expected values: ?=1-(?/?). These results, therefore, suggest that there may be a general threshold to support data quality control and assurance, that uncertainty analysis can be used to estimate error value and source, and that a data-model synthesis can usefully be applied to EC measurements to explore ecosystem intercomparison, model development, and model-data synthesis.

Kim, W.; Komori, D.; Cho, J.

2009-12-01

113

Measurement of the 8B Solar Neutrino Flux with KamLAND  

SciTech Connect

We report a measurement of the neutrino-electron elastic scattering rate from {sup 8}B solar neutrinos based on a 123 kton-day exposure of KamLAND. The background-subtracted electron recoil rate, above a 5.5-MeV analysis threshold is 1.49 {+-} 0.14(stat) {+-} 0.17(syst) events per kton-day. Interpreted as due to a pure electron flavor flux with a {sup 8}B neutrino spectrum, this corresponds to a spectrum integrated flux of 2.77 {+-} 0.26(stat) {+-} 0.32(syst) x 10{sup 6} cm{sup -2}s{sup -1}. The analysis threshold is driven by {sup 208}Tl present in the liquid scintillator, and the main source of systematic uncertainty is due to background from cosmogenic {sup 11}Be. The measured rate is consistent with existing measurements and with standard solar model predictions which include matter-enhanced neutrino oscillation.

Abe, S.; Furuno, K.; Gando, A.; Gando, Y.; Ichimura, K.; Ikeda, H.; Inoue, K.; Kibe, Y.; Kimura, W.; Kishimoto, Y.; Koga, M.; Minekawa, Y.; Mitsui, T.; Morikawa, T.; Nagai, N.; Nakajima, K.; Nakamura, K.; Nakamura, M.; Narita, K.; Shimizu, I.; Shimizu, Y.; Shirai, J.; Suekane, F.; Suzuki, A.; Takahashi, H.; Takahashi, N.; Takemoto, Y.; Tamae, K.; Watanabe, H.; Xu, B.D.; Yabumoto, H.; Yonezawa, E.; Yoshida, H.; Yoshida, S.; Enomoto, S.; Kozlov, A.; Murayama, H.; Grant, C.; Keefer, G.; McKee, D.; Piepke, A.; Banks, T.I.; Bloxham, T.; Detwiler, J.A.; Freedman, S.J.; Fujikawa, B.K.; Han, K.; Kadel, R.; O'Donnell, T.; Steiner, H.M.; Winslow, L.A.; Dwyer, D.A.; Mauger, C.; McKeown, R.D.; Zhang, C.; Berger, B.E.; Lane, C.E.; Maricic, J.; Miletic, T.; Batygov, M.; Learned, J.G.; Matsuno, S.; Pakvasa, S.; Sakai, M.; Horton-Smith, G.A.; Tang, A.; Downum, K.E.; Gratta, G.; Tolich, K.; Efremenko, Y.; Kamyshkov, Y.; Perevozchikov, O.; Karwowski, H.J.; Markoff, D.M.; Tornow, W.; Heeger, K.M.; Piquemal, F.; Ricol, J.-S.; Decowski, M.P.

2011-06-04

114

Time and Space Resolved Heat Flux Measurements During Nucleate Boiling with Constant Heat Flux Boundary Conditions  

NASA Technical Reports Server (NTRS)

The lack of temporally and spatially resolved measurements under nucleate bubbles has complicated efforts to fully explain pool-boiling phenomena. The objective of this current work was to acquire time and space resolved temperature distributions under nucleating bubbles on a constant heat flux surface using a microheater array with 100x 100 square microns resolution, then numerically determine the wall to liquid heat flux. This data was then correlated with high speed (greater than l000Hz) visual recordings of The bubble growth and departure from the heater surface acquired from below and from the side of the heater. The data indicate that microlayer evaporation and contact line heat transfer are not major heat transfer mechanisms for bubble growth. The dominant heat transfer mechanism appears to be transient conduction into the liquid as the liquid rewets the wall during the bubble departure process.

Yerramilli, Vamsee K.; Myers, Jerry G.; Hussey, Sam W.; Yee, Glenda F.; Kim, Jungho

2005-01-01

115

Measurement of a surface heat flux and temperature  

NASA Technical Reports Server (NTRS)

The Heat Flux Microsensor is a new sensor which was recently patented by Virginia Tech and is just starting to be marketed by Vatell Corp. The sensor is made using the thin-film microfabrication techniques directly on the material that is to be measured. It consists of several thin-film layers forming a differential thermopile across a thermal resistance layer. The measured heat flux q is proportional to the temperature difference across the resistance layer q= k(sub g)/delta(sub g) x (t(sub 1) - T(sub 2)), where k(sub g) is the thermal conductivity and delta (sub g) is the thickness of the thermal resistance layer. Because the gages are sputter coated directly onto the surface, their total thickness is less than 2 micrometers, which is two orders of magnitude thinner than previous gages. The resulting temperature difference across the thermal resistance layer (delta is less than 1 micrometer) is very small even at high heat fluxes. To generate a measurable signal many thermocouple pairs are put in series to form a differential thermopile. The combination of series thermocouple junctions and thin-film design creates a gage with very attractive characteristics. It is not only physically non-intrusive to the flow, but also causes minimal disruption of the surface temperature. Because it is so thin, the response time is less than 20 microsec. Consequently, the frequency response is flat from 0 to over 50 kHz. Moreover, the signal of the Heat Flux Microsensor is directly proportional to the heat flux. Therefore, it can easily be used in both steady and transient flows, and it measures both the steady and unsteady components of the surface heat flux. A version of the Heat Flux Microsensor has been developed to meet the harsh demands of combustion environments. These gages use platinum and platinum-10 percent rhodium as the thermoelectric materials. The thermal resistance layer is silicon monoxide and a protective coating of Al2O3 is deposited on top of the sensor. The superimposed thin-film pattern of all six layers is presented. The large pads are for connection with pins used to bring the signal out the back of the ceramic. In addition to the heat flux measurement, the surface temperature is measured with a platinum resistance layer (RTS). The resistance of this layer increases with increasing temperature. Therefore, these gages simultaneously measure the surface temperature and heat flux. The demonstrated applications include rocket nozzles, SCRAM jet engines, gas turbine engines, boiling heat transfer, flame experiments, basic fluid heat transfer, hypersonic flight, and shock tube testing. The laboratory involves using one of these sensors in a small combustion flame. The sensor is made on a 2.5 cm diameter piece of aluminum nitride ceramic.

Davis, R. M.; Antoine, G. J.; Diller, T. E.; Wicks, A. L.

1994-01-01

116

Airborne flux measurements of biogenic isoprene over California  

NASA Astrophysics Data System (ADS)

Biogenic isoprene fluxes were measured onboard the CIRPAS Twin Otter aircraft as part of the California Airborne Biogenic volatile organic compound (BVOC) Emission Research in Natural Ecosystem Transects (CABERNET) campaign during June 2011. The airborne virtual disjunct eddy covariance (AvDEC) approach used measurements from a proton transfer reaction mass spectrometer (PTR-MS) and a wind radome probe to directly determine fluxes of isoprene over 7400 km of flight paths focusing on areas of California predicted to have the largest emissions. The fast Fourier transform (FFT) approach was used to calculate fluxes of isoprene over long transects of more than 15 km, most commonly between 50 and 150 km. The continuous wavelet transformation (CWT) approach was used over the same transects to also calculate instantaneous isoprene fluxes with localization of both frequency and time independent of non-stationarities. Fluxes were generally measured by flying consistently at 400 m ± 50 m (a.g.l.) altitude, and extrapolated to the surface according to the determined flux divergence determined in the racetrack-stacked profiles. The wavelet-derived surface fluxes of isoprene averaged to 2 km spatial resolution showed good correspondence to basal emission factor (BEF) land-cover data sets used to drive BVOC emission models. The surface flux of isoprene was close to zero over Central Valley crops and desert shrublands, but was very high (up to 15 mg m-2 h-1) above oak woodlands, with clear dependence of emissions on temperature and oak density. Isoprene concentrations of up to 8 ppb were observed at aircraft height on the hottest days and over the dominant source regions. Even though the isoprene emissions from agricultural crop regions, shrublands, and coniferous forests were extremely low, observations at the Walnut Grove tower south of Sacramento demonstrate that isoprene oxidation products from the high emitting regions in the surrounding oak woodlands accumulate at night in the residual layer above the valley and mix down into the valley in the morning. Thus, the isoprene emissions surrounding the valley have relevance for the regional photochemistry that is not immediately apparent solely from the direct emission flux distribution. This paper reports the first regional observations of fluxes from specific sources by eddy covariance from an aircraft which can finally constrain statewide isoprene emission inventories used for ozone simulations by state agencies. While previously there was no available means to constrain the biogenic models, our results provide a good understanding of what the major sources of isoprene are in California, their magnitude, and how they are distributed. This data set on isoprene fluxes will be particularly useful for evaluating potential model alternatives which will be dealt with in a separate paper to assess isoprene emission models and their driving variable data sets.

Misztal, P. K.; Karl, T.; Weber, R.; Jonsson, H. H.; Guenther, A. B.; Goldstein, A. H.

2014-10-01

117

A mobile detector for measurements of the atmospheric muon flux in underground sites  

NASA Astrophysics Data System (ADS)

Muons comprise an important contribution of the natural radiation dose in air (approx. 30 nSv/h of a total dose rate of 65-130 nSv/h), as well as in underground sites even when the flux and relative contribution are significantly reduced. The flux of muons observed underground can be used as an estimator for the depth in mwe (meter water equivalent) of the underground site. The water equivalent depth is important information to devise physics experiments feasible for a specific site. A mobile detector for performing measurements of the muon flux was developed in IFIN-HH, Bucharest. Consisting of two scintillator plates (approx. 0.9 m2) which measure in coincidence, the detector is installed on a van which facilitates measurements at different locations at the surface or underground. The detector was used to determine muon fluxes at different sites in Romania. In particular, data were taken and the values of meter water equivalents were assessed for several locations at the salt mine in Slanic-Prahova, Romania. The measurements have been performed in two different galleries of the Slanic mine at different depths. In order to test the stability of the method, also measurements of the muon flux at the surface at different elevations were performed. The results were compared with predictions of Monte-Carlo simulations using the CORSIKA and MUSIC codes.

Mitrica, Bogdan; Margineanu, Romul; Stoica, Sabin; Petcu, Mirel; Brancus, Iliana; Jipa, Alexandru; Lazanu, Ionel; Sima, Octavian; Haungs, Andreas; Rebel, Heinigerd; Petre, Marian; Toma, Gabriel; Saftoiu, Alexandra; Stanca, Denis; Apostu, Ana; Gomoiu, Claudia

2011-10-01

118

Fast Flux Test Facility passive safety reactivity feedback measurements  

SciTech Connect

A series of experiments conducted in the Fast Flux Test Facility (FFTF) measured the reactivity change between approximately 200 reactor states. The test data have been evaluated to determine the thermal hydraulic parameters of the reactor at those states. Auxiliary measurements have been analyzed to convert the measured control rod position changes to reactivity and to correct for burnup effects. The data are now available for studies of the temperature reactivity feedbacks in liquid metal reactors. Preliminary comparisons with a feedback algorithm developed from normal FFTF operation indicate that the functional form of feedbacks can be extrapolated to offnormal conditions. 1 ref., 6 figs., 3 tabs.

Knutson, B.J.; Harris, R.A.; Nguyen, D.H.; Omberg, R.P.

1988-03-01

119

Methane fluxes measured by eddy covariance at a temperate upland forest  

NASA Astrophysics Data System (ADS)

Methane flux measurements were carried out at a temperate upland forest in Central Ontario, Haliburton Forest and Wildlife Reserve (45.28° N, 78.55° W) using the eddy covariance (EC) method. An off-axis integrated cavity output spectrometer (OA-ICOS) Fast Greenhouse Gas Analyzer (FGGA from Los Gatos Research, Inc.) operated at a sampling rate of 10 Hz allowed for simultaneous measurement of methane (CH4), carbon dioxide (CO2), and water (H2O) over five months from June to October in 2011. Air was pulled from the top of a 32 m tower, 8 m above the forest canopy, to the bottom of the tower through 40 m of tubing to the instrument. A sonic anemometer and a LI-7500 open-path sensor were also used at the top of the tower to provide high frequency wind data and comparative open-path measurements of CO2 and H2O. A nearby soil station measured soil water content and soil temperature at 0, 3, and 10 cm below the surface. Observed methane fluxes showed net uptake of CH4 over the measurement period with an average uptake flux value (± standard deviation of the mean) of -2.7±0.13 nmol m-2 s-1. In early June when measurements commenced, the soil moisture was relatively high and CH4 flux values showed net emission. As the season advanced the soil became progressively drier, and there was an increasing trend in CH4 uptake, peaking in mid-September. There was also a diurnal trend in the CH4 flux, with increased uptake during the day, and decreased uptake between 0:00 and 08:00. The CH4 flux values correlated well with the horizontal wind speed measured within the forest canopy. We hypothesize that this may be due to a ventilation effect in which higher wind speed facilitates the introduction of CH4-rich air and removes CH4-depleted air near the methanotrophs in the soil. The measurements were made in an uneven-aged managed forest stand last harvested 15 years ago containing sandy and acidic soils (pH 4.0 - 5.0). Chamber flux measurements of CH4 were also performed at seven toposequences around the tower, every two weeks from June to October. These chamber flux values are qualitatively consistent with those measured by eddy covariance in terms of magnitude and seasonality. While the flux measurements indicate net uptake by soils, the diurnal cycle of mixing ratios often showed nighttime accumulation of methane, indicating that over the broader landscape around the tower, emissions may dominate.

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

2012-12-01

120

Estimating terrestrial uranium and thorium by antineutrino flux measurements  

E-print Network

Uranium and thorium within the Earth produce a major portion of terrestrial heat along with a measurable flux of electron antineutrinos. These elements are key components in geophysical and geochemical models. Their quantity and distribution drive the dynamics, define the thermal history, and are a consequence of the differentiation of the Earth. Knowledge of uranium and thorium concentrations in geological reservoirs relies largely on geochemical model calculations. This research report describes the methods and criteria to experimentally determine average concentrations of uranium and thorium in the continental crust and in the mantle using site-specific measurements of the terrestrial antineutrino flux. Optimal, model-independent determinations involve significant exposures of antineutrino detectors remote from nuclear reactors at both a mid-continental and a mid-oceanic site. This would require major, new antineutrino detection projects. The results of such projects could yield a greatly improved understa...

Dye, Stephen T

2008-01-01

121

MARIE Dose and Flux Measurements in Mars Orbit  

NASA Technical Reports Server (NTRS)

We present results from the Martian Radiation Environment Experiment (MARIE), aboard the 2001 Mars Odyssey spacecraft in orbit around Mars. MARIE operated successfully from March 2002 through October 2003. At the time of this writing, the instrument is off due to a loss of communications during an extremely intense Solar Particle Event. Efforts to revive MARIE are planned for Spring 2004, when Odyssey's role as a communications relay for the MER rovers is completed. During the period of successful operation, MARIE returned the first detailed energetic charged particle data from Mars. Due to limitations of the instrument, normalizing MARIE data to flux or dose is not straightforward - several large corrections are needed. Thus normalized results (like dose or flux) have large uncertainties and/or significant model-dependence. The problems in normalization are mainly due to inefficiency in detecting high-energy protons (signal-to-noise problems force the trigger threshold to be higher than optimal), to the excessively high gains employed in the signal processing electronics (many ions deposit energy sufficient to saturate the electronics, and dE/dx information is lost), and to artifacts associated with the two trigger detectors (incomplete registration of dE/dx). Despite these problems, MARIE is efficient for detecting helium ions with kinetic energies above about 30 MeV/nucleon, and for detecting high-energy ions (energies above about 400 MeV/nucleon) with charges from 5 to 10. Fluxes of these heavier ions can be compared to fluxes obtained from the ACE/CRIS instrument, providing at least one area of direct comparison between data obtained at Earth and at Mars; this analysis will be presented as a work in progress. We will also present dose-rate data, with a detailed explanation of the many sources of uncertainty in normalization. The results for both flux and dose will be compared to predictions of the HZETRN model of the GCR.

Zeitlin, C.; Cleghorn, T.; Cucinotta, F. A.; Saganti, P.; Andersen, V.; Lee, K. T.; Pinsky, L. S.; Turner, R.; Atwell, W.

2004-01-01

122

How are Rainfall Rates Measured?  

NSDL National Science Digital Library

In this problem-based learning activity, students learn about weather forecasting and the role of the TRMM (Tropical Rainfall Measuring Mission) satellite in data collection. Assuming the role of climatologists, students assist a reporter in determining the accuracy of weather predictions published in The Old Farmer's Almanac. The lesson requires a street map of the local community, acetate sheets to cover the map, materials needed to build a homemade rain gauge, and sample pages of the almanac. Teacher notes, student worksheet, glossary and an appendix introducing problem-based learning are included. This resource is the first of the 3-part learning module, Investigating the Climate System: Precipitation.

123

Ion fluxes across the pitcher walls of three Bornean Nepenthes pitcher plant species: flux rates and gland distribution patterns reflect nitrogen sequestration strategies.  

PubMed

Nepenthes pitcher plant species differ in their prey capture strategies, prey capture rates, and pitcher longevity. In this study, it is investigated whether or not interspecific differences in nutrient sequestration strategy are reflected in the physiology and microstructure of the pitchers themselves. Using a non-invasive technique (MIFE), ion fluxes in pitchers of Nepenthes ampullaria Jack, Nepenthes bicalcarata Hook.f., and Nepenthes rafflesiana Jack were measured. Scanning electron microscopy was also used to characterize the distribution of glandular and other structures on the inner pitcher walls. The results demonstrate that nutrient sequestration strategy is indeed mirrored in pitcher physiology and microstructure. Species producing long-lived pitchers with low prey capture rates (N. ampullaria, N. bicalcarata) showed lower rates of NH(4)(+) uptake than N. rafflesiana, a species producing short-lived pitchers with high capture rates. Crucially, species dependent upon aquatic commensals (N. ampullaria, N. bicalcarata) actively manipulated H(+) fluxes to maintain less acid pitcher fluid than found in 'typical' species; in addition, these species lacked the lunate cells and epicuticular waxes characteristic of 'typical' insectivorous congeners. An unexpected finding was that ion fluxes occurred in the wax-covered, non-glandular zones in N. rafflesiana. The only candidates for active transport of aqueous ions in these zones appear to be the epidermal cells lying beneath the lunate cells, as these are the only sites not visibly coated with epicuticular waxes. PMID:20150519

Moran, Jonathan A; Hawkins, Barbara J; Gowen, Brent E; Robbins, Samantha L

2010-03-01

124

Initial Tile Temperature and Heat Flux Measurements in NSTX  

NASA Astrophysics Data System (ADS)

Due to their compact nature, spherical tori are projected to experience higher peak heat flux than conventional aspect ratio tokamaks of comparable heating power. For NSTX, it has been predicted[1,2] that the peak heat flux in double-null divertor configuration could reach between 10-15 MW/m2, and single-null operation would result in even higher peak heat flux. To test these predictions and support physics operations, two infrared television cameras (Inframetrics 525) have been installed on NSTX to monitor real-time tile heating and surface heat flux. The data are analyzed in real-time with a frame grabber (IMAXX) and software, and these data are also archived on videotape for future analysis. The first set of measurements will focus on thermal emission from the RF antenna, the center stack, and divertor regions. Initial data and comparison with the earlier predictions will be presented. 1 R.Maingi, et. al., "Estimates of Scrape-Off Layer and Divertor Parameters in NSTX", Proc. 1996 Int’l Workshop on the Spherical Torus, Abingdon, U.K., Dec. 4-6, 1996. 2 R. Maingi, et. al., "2-D Edge Plasma Transport Calculations for NSTX", Proc. 1997 Int’l Workshop on the Spherical Torus, St. Petersburg, Russia, Sept. 3-5, 1997.

Maingi, Rajesh; Kugel, Henry; Roquemore, Lane; Lasnier, Charles; Johnson, Dave

1999-11-01

125

DIRECT MEASUREMENT OF HEAT FLUX FROM COOLING LAKE THERMAL IMAGERY  

SciTech Connect

Laboratory experiments show a linear relationship between the total heat flux from a water surface to air and the standard deviation of the surface temperature field, {sigma}, derived from thermal images of the water surface over a range of heat fluxes from 400 to 1800 Wm{sup -2}. Thermal imagery and surface data were collected at two power plant cooling lakes to determine if the laboratory relationship between heat flux and {sigma} exists in large heated bodies of water. The heat fluxes computed from the cooling lake data range from 200 to 1400 Wm{sup -2}. The linear relationship between {sigma} and Q is evident in the cooling lake data, but it is necessary to apply band pass filtering to the thermal imagery to remove camera artifacts and non-convective thermal gradients. The correlation between {sigma} and Q is improved if a correction to the measured {sigma} is made that accounts for wind speed effects on the thermal convection. Based on more than a thousand cooling lake images, the correlation coefficients between {sigma} and Q ranged from about 0.8 to 0.9.

Garrett, A; Eliel Villa-Aleman, E; Robert Kurzeja, R; Malcolm Pendergast, M; Timothy Brown, T; Saleem Salaymeh, S

2007-12-19

126

EISCAT observations of pump-enhanced plasma temperature and optical emission excitation rate as a function of power flux  

NASA Astrophysics Data System (ADS)

We analyze optical emissions and enhanced electron temperatures induced by high power HF radio waves as a function of power flux using the EISCAT heater with a range of effective radiated powers. The UHF radar was used to measure the electron temperatures and densities. The Digital All Sky Imager was used to record the 630.0 nm optical emission intensities. We quantify the HF flux loss due to self-absorption in the D-region (typically 3-11 dB) and refraction in the F-region to determine the flux which reaches the upper-hybrid resonance height. We find a quasi-linear relationship between the HF flux and both the temperature enhancement and the optical emission excitation rate with a threshold at ˜37.5 ?Wm-2. On average ˜70% of the HF flux at the upper-hybrid resonance height goes in to heating the electrons for fluxes above the threshold compared to ˜40% for fluxes below the threshold.

Bryers, C. J.; Kosch, M. J.; Senior, A.; Rietveld, M. T.; Yeoman, T. K.

2012-09-01

127

Image migration: measured retrieval rates  

NASA Astrophysics Data System (ADS)

When the Indianapolis Veterans Affairs Medical Center changed Picture Archiving and Communication Systems (PACS) vendors, we chose to use "on demand" image migration as the more cost effective solution. The legacy PACS stores the image data on optical disks in multi-platter jukeboxes. The estimated size of the legacy image data is about 5 terabytes containing studies from ~1997 to ~2003. Both the legacy and the new PACS support a manual DICOM query/retrieve. We implemented workflow rules to determine when to fetch the relevant priors from the legacy PACS. When a patient presents for a new radiology study, we used the following rules to initiate the manual DICOM query/retrieve. For general radiography we retrieved the two most recent prior examinations and for the modalities MR and CT we retrieved the clinically relevant prior examinations. We monitored the number of studies retrieved each week for about a 12 month period. For our facility which performs about 70,000 radiology examinations per year, we observed an essentially constant retrieval rate of slightly less than 50 studies per week. Some explanations for what may be considered an anomalous result maybe related to the fact that we are a tertiary care facility and a teaching hospital.

Witt, Robert M.

2007-03-01

128

Initial assessment of multi-scale measures of C02 and H20flux in the Siberian taiga  

Microsoft Academic Search

We measured C02 and HzO fluxes between undis- turbed Larix gmelinii forest and the atmosphere at a remote Eastern Siberian site in July 1993. Scaled-up leaf-level porom- eter measurements agreed with those derived from the eddy correlation technique for the canopy fluxes of COz and HzO. Patch-scale measurements of ecosystem C02 exchange agreed in turn with regional CO2 exchange rates

D. Y. HOLLINGER; F. M. KELLIHER; E.-D. SCHULZE; N. N. VYGODSKAYA; A. VARLAGIN

129

Momentum Flux Measuring Instrument for Neutral and Charged Particle Flows  

NASA Technical Reports Server (NTRS)

An instrument to measure the momentum flux (total pressure) of plasma and neutral particle jets onto a surface has been developed. While this instrument was developed for magnetized plasmas, the concept works for non-magnetized plasmas as well. We have measured forces as small as 10(exp -4) Newtons on a surface immersed in the plasma where small forces are due to ionic and neutral particles with kinetic energies on the order of a few eV impacting the surface. This instrument, a force sensor, uses a target plate (surface) that is immersed in the plasma and connected to one end of an alumina rod while the opposite end of the alumina rod is mechanically connected to a titanium beam on which four strain gauges are mounted. The force on the target generates torque causing strain in the beam. The resulting strain measurements can be correlated to a force on the target plate. The alumina rod electrically and thermally isolates the target plate from the strain gauge beam and allows the strain gauges to be located out of the plasma flow while also serving as a moment arm of several inches to increase the strain in the beam at the strain gauge location. These force measurements correspond directly to momentum flux and may be used with known plasma conditions to place boundaries on the kinetic energies of the plasma and neutral particles. The force measurements may also be used to infer thrust produced by a plasma propulsive device. Stainless steel, titanium, molybdenum, and aluminum flat target plates have been used. Momentum flux measurements of H2, D2, He, and Ar plasmas produced in a magnetized plasma device have been performed.

Chavers, Greg; Chang-Diaz, Franklin; Schafer, Charles F. (Technical Monitor)

2002-01-01

130

Saharan dust flux and deposition rate near the Gulf of Guinea  

NASA Astrophysics Data System (ADS)

It has been estimated that 240 +/- 80 Tg of Saharan dust are transported annually from Africa over the Atlantic Ocean to far away places such as the Amazon Basin and the Caribbean during the summer months of June to August. There are, however, few direct measurements of the dust transport towards the Gulf of Guinea (5°N) during the winter months of December-March. In this study, the Saharan dust flux and deposition to the Gulf of Guinea during the Harmattan (winter) season are estimated using the geographical area of Ghana (lying between latitudes 5° and 12°N) as the reference location. The flux and deposition rates were determined during the Harmattan dust episodes of 2002 and 2005 by measuring surface dust concentrations concurrently at two locations in northern and central Ghana. The average particle number concentration in 2002 was 21 cm-3 while in 2005, it was 30 cm-3 (although a few daily mean values were as high as 60 cm-3). The corresponding mean mass concentrations were 543 ?g m-3 and 1383 ?g m-3 in 2002 and 2005, respectively. The deposition rates for the two winter seasons were estimated at 13 and 31 t km-2 yr-1, respectively, corresponding to a dust deposition thickness of 5 ?m in 2002 and 12 ?m in 2005. The transit time for the dust aerosol to travel a distance of 320 km between the two measurement sites in a north-south direction was determined experimentally to be of the order of 1 d, a result which could serve as an early warning indicator for severe dust outbreaks travelling from higher to lower latitudes in the region. The results of this study may also be compared with any future simulation of the African dust plume towards the Gulf of Guinea.

Resch, F.; Sunnu, A.; Afeti, G.

2008-02-01

131

Metabolic flux is a determinant of the evolutionary rates of enzyme-encoding genes.  

PubMed

Relationships between evolutionary rates and gene properties on a genomic, functional, pathway, or system level are being explored to unravel the principles of the evolutionary process. In particular, functional network properties have been analyzed to recognize the constraints they may impose on the evolutionary fate of genes. Here we took as a case study the core metabolic network in human erythrocytes and we analyzed the relationship between the evolutionary rates of its genes and the metabolic flux distribution throughout it. We found that metabolic flux correlates with the ratio of nonsynonymous to synonymous substitution rates. Genes encoding enzymes that carry high fluxes have been more constrained in their evolution, while purifying selection is more relaxed in genes encoding enzymes carrying low metabolic fluxes. These results demonstrate the importance of considering the dynamical functioning of gene networks when assessing the action of selection on system-level properties. PMID:24102646

Colombo, Martino; Laayouni, Hafid; Invergo, Brandon M; Bertranpetit, Jaume; Montanucci, Ludovica

2014-02-01

132

Controlling quantum flux through measurement: An idealised example  

NASA Astrophysics Data System (ADS)

Classically, no transfer occurs between two equally filled reservoirs, no matter how one looks at them, but the situation can be different quantum-mechanically. This paradoxically surprising phenomenon rests on the distinctive property of the quantum world that one cannot stare at a system without disturbing it. It was recently discovered that this seemingly annoying feature could be harnessed to control small quantum systems using weak measurements. Here we present one of the simplest models —an idealised double quantum dot—where by toying with the dot measurement strength, i.e. the intensity of the look, it is possible to create a particle flux in an otherwise completely symmetric system. The basic property underlying this phenomena is that measurement disturbances are very different on a system evolving unitarily and a system evolving dissipatively. This effect shows that adaptive measurements can have dramatic effects enabling transport control but possibly inducing biases in the measurement of macroscopic quantities if not handled with care.

Tilloy, A.; Bauer, M.; Bernard, D.

2014-07-01

133

Imposing strong constraints on tropical terrestrial CO2 fluxes using passenger aircraft based measurements  

NASA Astrophysics Data System (ADS)

Better understanding of the global and regional carbon budget is needed to perform a reliable prediction of future climate with an earth system model. However, the reliability of CO2 source/sink estimation by inverse modeling, which is one of the promising methods to estimate regional carbon budget, is limited because of sparse observational data coverage. Very few observational data are available in tropics. Therefore, especially the reconstruction of tropical terrestrial fluxes has considerable uncertainties. In this study, regional CO2 fluxes for 2006-2008 are estimated by inverse modeling using the Comprehensive Observation Network for Trace gases by Airliner (CONTRAIL) in addition to the surface measurement dataset of GLOBALVIEW-CO2. CONTRAIL is a recently established CO2 measurement network using in-situ measurement instruments on board commercial aircraft. Five CONTRAIL aircraft travel back and forth between Japan and many areas: Europe, North America, Southeast Asia, South Asia, and Australia. The Bayesian synthesis approach is used to estimate monthly fluxes for 42 regions using NICAM-TM simulations with existing CO2 flux datasets and monthly mean observational data. It is demonstrated that the aircraft data have great impact on estimated tropical terrestrial fluxes. By adding the aircraft data to the surface data, the analyzed uncertainty of tropical fluxes has been reduced by 15 % and more than 30 % uncertainty reduction rate is found in Southeast and South Asia. Specifically, for annual net CO2 fluxes, nearly neutral fluxes of Indonesia, which is estimated using the surface dataset alone, turn to positive fluxes, i.e. carbon sources. In Indonesia, a remarkable carbon release during the severe drought period of October-December in 2006 is estimated, which suggests that biosphere respiration or biomass burning was larger than the prior fluxes. Comparison of the optimized atmospheric CO2 with independent aircraft measurements of CARIBIC tends to validate results of the inversion system. It is expected that the use of instantaneous observational data with more sophisticated inversion methods will provide more accurate estimation of surface CO2 fluxes.

Niwa, Y.; Machida, T.; Sawa, Y.; Matsueda, H.; Schuck, T. J.; Brenninkmeijer, C. A.; Imasu, R.; Satoh, M.

2011-12-01

134

First measurement of the flux of solar neutrinos from the sun at the Sudbury Neutrino Observatory  

NASA Astrophysics Data System (ADS)

The Sudbury Neutrino Observatory (SNO) is a second generation solar neutrino detector. SNO is the first experiment that is able to measure both the electron neutrino flux and a flavor-blind flux of all active neutrino types, allowing a model-independent determination if the deficit of solar neutrinos known as the solar neutrino problem is due to neutrino oscillation. The Sudbury Neutrino Observatory started taking production data in November, 1999. A measurement of the charged current rate will be the first indication if SNO too sees a suppression of the solar neutrino signal relative to the theoretical predictions. Such a confirmation is the first step in SNO's ambitious science program. In this thesis, we present evidence that SNO is seeing solar neutrinos and a preliminary ratio of the measured vs predicted rate of electrons as induced by 8B neutrinos in the ?e, + d --> p + p + e charged-current (CC) reaction.

Wittich, Peter

2000-12-01

135

Momentum flux measurements using an impact thrust stand  

NASA Astrophysics Data System (ADS)

A device has been developed to measure the force caused by a beam of charged and neutral particles impacting a target plate. This device, an impact thrust stand, was developed to allow thrusters, during early stages of development, to be quickly and easily evaluated and compared to other thrusters. Since some thruster concepts are tested using laboratory equipment that is heavy and cumbersome, measuring the momentum flux of the particles in the plume can be much simpler than placing the entire thruster on a thrust stand. Conservation of momentum requires the momentum flux measured in the plume to be related to the thrust produced by the thruster. The impact thrust stand was designed to be placed in the plume of an electric thruster and has been tested and compared to the thrust measured from a Hall thruster placed on a pendulum thrust stand. Force measurements taken at several axial locations in the magnetic nozzle region of the Variable Specific Impulse Magnetoplasma Rocket will be presented.

Chavers, Greg; Chang-Diaz, Franklin; Breizman, Boris; Bengtson, Roger

2004-11-01

136

Momentum Flux Measurements Using an Impact Thrust Stand  

NASA Technical Reports Server (NTRS)

A device has been developed to measure the force caused by a beam of charged and neutral particles impacting a target plate. This device, an impact thrust stand, was developed to allow thrusters, during early stages of development, to be quickly and easily exhausted and compared to other thrusters. Since some thruster concepts are tested using laboratory equipment that is heavy and cumbersome, measuring the momentum flux of the particles in the plume can be much simpler than placing the entire thruster on a thrust stand. Conservation of momentum requires the momentum flux measured in the plume to be related to the thrust produced by the thruster. The impact thrust stand was designed to be placed in the plume of an electric thruster and has been tested and compared to the thrust measured from a Hall thruster placed on a pendulum thrust stand. Force measurements taken at several axial locations in the magnetic nozzle region of the Variable Specific Impulse Magnetoplasma Rocket will be presented.

Chavers, Greg; Chang-Diaz, Franklin; Breizman, Boris; Bengtson, Roger

2004-01-01

137

HANARO core channel flow-rate measurement.  

National Technical Information Service (NTIS)

HANARO core consists of 23 hexagonal flow tubes and 16 cylindrical flow tubes. To get the core flow distribution, we used 6 flow-rate measuring dummy fuel assemblies (instrumented dummy fuel assemblies). The differential pressures were measured and conver...

H. I. Kim, H. T. Chae, D. S. Im S. D. Kim

1996-01-01

138

Development of a Passive Sensor for Measuring Water and Solute Mass Flux in the Hyporheic Zone  

NASA Astrophysics Data System (ADS)

Measuring water, pollutant and nutrient exchange at the groundwater-surface water interface is challenging due to the dynamic nature of the hyporheic zone. Quantifying the exchange is critical to understanding mass balance across this interface. Technologies currently exist to identify groundwater discharge zones and infer estimates of contaminant mass flux based on total contaminant concentration in bulk sediment, though it is generally accepted that freely dissolved concentration in pore water is a better measure of potential exposure. Laboratory and preliminary field testing has been completed to demonstrate a new tool with potential to provide more accurate characterization of water, pollutant and nutrient flux at the groundwater-surface water interface through direct in-situ measurement. The sediment bed passive flux meter (SBPFM) was designed for passively and directly providing in-situ measurements of volumetric water flux and solute mass flux vertically through the upper surface sediment layer and into the overlying water column. The SBPFM consists of an internal permeable sorbent which is impregnated with one or more water soluble tracers (typically alcohols) and is contained in a dedicated drive-point with upper and lower screened openings for fluid intake and exhaust. This configuration generates water flow through the device proportional to the vertical gradient between the sediment bed and the water column. Once the SBPFM has been deployed, the tracers are displaced from the sorbent at rates proportional to the average vertical specific discharge. The mass loss of tracers during deployment can be used to calculate the cumulative water flux. Similarly, the cumulative mass of sorbed pollutants or nutrients provide a direct measurement of the vertical mass flux during deployment. The SBPFM prototype has been tested in controlled laboratory sediment interface models. The results show good agreement between the SBPFM calculated and the applied water and contaminant fluxes through the laboratory aquifer model. Flow reversals are anticipated for tidal sites and sorbent layers within the PFM are segmented and used to determine next flux magnitude and direction averaged over the deployment period. Preliminary field testing is underway focusing on an areas with chlorinated solvent contamination discharging to surface water. The SBPFM is deployed to quantify the net mass discharge of contaminants to a small stream over a short reach. The integrated mass discharge can be compared to concentrations and mass discharge observed in surface water. The SBPFM provides a new tool to assess water and solute flux at point locations and can provide spatial variability that can be integrated to support mass balance studies on segments of surface water reaches.

Annable, Michael D.; Layton, Leif; Hatfield, Kirk; Newman, Mark C.; Cho, Jaehyun; Klammler, Harald

2014-05-01

139

Progress on a Rayleigh Scattering Mass Flux Measurement Technique  

NASA Technical Reports Server (NTRS)

A Rayleigh scattering diagnostic has been developed to provide mass flux measurements in wind tunnel flows. Spectroscopic molecular Rayleigh scattering is an established flow diagnostic tool that has the ability to provide simultaneous density and velocity measurements in gaseous flows. Rayleigh scattered light from a focused 10 Watt continuous-wave laser beam is collected and fiber-optically transmitted to a solid Fabry-Perot etalon for spectral analysis. The circular interference pattern that contains the spectral information that is needed to determine the flow properties is imaged onto a CCD detector. Baseline measurements of density and velocity in the test section of the 15 cm x 15 cm Supersonic Wind Tunnel at NASA Glenn Research Center are presented as well as velocity measurements within a supersonic combustion ramjet engine isolator model installed in the tunnel test section.

Mielke-Fagan, Amy F.; Clem, Michelle M.; Elam, Kristie A.; Hirt, Stefanie M.

2010-01-01

140

Are far-IR fluxes good measures of cloud mass?  

NASA Astrophysics Data System (ADS)

It is commonly assumed that the Herschel far-IR fluxes are a measure of column density, hence, mass of interstellar clouds. The Polaris Flare, a high galactic latitude cirrus cloud, with several starless molecular cores, has been previously observed with the Herschel Space Telescope. We used Cloudy version 13.02 to model a molecular cloud MCLD 123.5+24.9, one of the denser regions of the Polaris Flare. These models include a detailed calculation of far-IR grain opacities, subject to various assumptions about grain composition, and predict far-IR fluxes. The models suggest that the observed fluxes reflect the incident stellar UV radiation field rather than the column density, if N(H) > a few times 1021 cm2 (AV > 1). For higher column densities, the models show that dust temperatures decline rapidly into the cloud. Therefore, the cloud interiors contribute very little additional far-IR flux, and column densities based upon far-IR fluxes can be significantly underestimated. The Polaris Flare, 150 pc distant, is well within the Galactic disc. There are no nearby hot stars. Therefore, the stellar UV radiation field incident on the cloud should be close to the mean interstellar radiation field (ISRF). In addition, the calculated grain opacities required to reproduce the far-IR fluxes in the Cloudy models are a few factors larger than that calculated for standard ISM graphite and silicate grains. This result suggests that the grains in dense regions are coated with water and ammonia ices, increasing their sizes and opacities. The Cloudy models also predict mm-wavelength CO line strengths for comparison with published observations at the IRAM 30-m telescope. In order to reproduce the observed CO line strengths for cores in MCLD 123.5+24.9, the models require that CO molecules be partially frozen out onto the grains. This result places age constraints upon the cores. We have also modeled CO emission from inter-core regions in MCLD 123.5+24.9. For these regions, the models significantly under predict the observed CO line strengths unless the molecular gas is clumped into high-density regions.

Wagle, Gururaj; Ferland, G. J.; Troland, T. H.; Abel, N.

2014-01-01

141

KNVK vacuum fission chambers for measuring neutron flux density  

SciTech Connect

Vacuum fission chambers (VFC) are used to record the time dependence of the flux density of neutrons from nuclear reactors. Their comparatively high yield of slow secondary electrons (about 500 per fission fragment), large dynamic range, high temporal resolution, radiation resistance, and operating reliability make them superior to other detectors. However, the accuracy with which fast neutrons are recorded with two-electrode VFC is limited by their sensitivity to the accompanying ..gamma.. radiation. A promising approach is to create three-electrode VFC, in which the signal from the ..gamma.. radiation is compensated based on the type of differential chamber, one section of which contains a neutron-sensitive coating, while the other is employed without a coating. In this paper they describe a three-electrode VFC, called the compensated neutron vacuum chamber (KNVK), with a controllable sensitivity to ..gamma.. radiation near zero and an absolute method for measuring the time-dependence of the neutron flux density. The results of dynamic studies of the flux density of neutrons from different energy groups with a collection of VFC of the KNVK2 type with different fissioning isotopes are presented.

Malyshev, E.K.; Chuklyaev, S.V.; Shchetinin, O.I.

1987-09-01

142

CAN COSMIC-RAY NUCLEON MEASUREMENTS BE USED TO SCALE PRODUCTION RATES OF COSMOGENIC NUCLIDES?  

E-print Network

CAN COSMIC-RAY NUCLEON MEASUREMENTS BE USED TO SCALE PRODUCTION RATES OF COSMOGENIC NUCLIDES variability of nuclide production rates on the earth's surface. Direct measurements of cosmic-ray fluxes have spatial variations of cosmic-ray neu- tron intensity and production rates of in-situ cosmogenic nuclides

Zreda, Marek

143

Nitrous Oxide Fluxes in Turfgrass: Effects of Nitrogen Fertilization Rates and Types Dale J. Bremer*  

E-print Network

Nitrous Oxide Fluxes in Turfgrass: Effects of Nitrogen Fertilization Rates and Types Dale J. Bremer emissions of N2O in turfgrass; (ii) evaluate effects of fertilization with a high and low rate of urea N; and (iii) evaluate effects of urea and ammonium sulfate on N2O emissions in turfgrass. Nitrogen fertilizers

144

Imposing strong constraints on tropical terrestrial CO2 fluxes using passenger aircraft based measurements  

NASA Astrophysics Data System (ADS)

Because very few measurements of atmospheric carbon dioxide (CO2) are available in the tropics, estimates of surface CO2 fluxes in tropical regions are beset with considerable uncertainties. To improve estimates of tropical terrestrial fluxes, atmospheric CO2 inversion was performed using passenger aircraft based measurements of the Comprehensive Observation Network for Trace gases by Airliner (CONTRAIL) project in addition to the surface measurement data set of GLOBALVIEW-CO2. Regional monthly fluxes at the earth's surface were estimated using the Bayesian synthesis approach focusing on the period 2006-2008 using the Nonhydrostatic Icosahedral Atmospheric Model-based Transport Model (NICAM-TM). By adding the aircraft to the surface data, the posterior flux errors were greatly reduced; specifically, error reductions of up to 64% were found for tropical Asia regions. This strong impact is closely related to efficient vertical transport in the tropics. The optimized surface fluxes using the CONTRAIL data were evaluated by comparing the simulated atmospheric CO2 distributions with independent aircraft measurements of the Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container (CARIBIC) project. The inversion with the CONTRAIL data yields the global carbon sequestration rates of 2.22 ± 0.28 Pg C yr-1 for the terrestrial biosphere and 2.24 ± 0.27 Pg C yr-1 for the oceans (the both are adjusted by riverine input of CO2). For the first time the CONTRAIL CO2 measurements were used in an inversion system to identify the areas of greatest impact in terms of reducing flux uncertainties.

Niwa, Yosuke; Machida, Toshinobu; Sawa, Yousuke; Matsueda, Hidekazu; Schuck, Tanja J.; Brenninkmeijer, Carl A. M.; Imasu, Ryoichi; Satoh, Masaki

2012-06-01

145

11C measurement and CNO and pep fluxes at Borexino  

NASA Astrophysics Data System (ADS)

The Borexino experiment is specifically designed for measuring the solar 7Be- ? flux. Moreover, Borexino has the potential to extend the energy window of observation in order to probe solar neutrinos from the pep fusion process and from the CNO cycle, a region dominated by the in situ production of cosmogenic 11C. We investigated the possibility to reject 11C events in Borexino by looking at the three-fold coincidence with the parent muon track and the subsequent neutron capture on protons. Furthermore, the three-fold coincidence has been applied to the Counting Test Facility data in order to evaluate the detection efficiency.

Franco, D.; Borexino Collaboration

146

System having unmodulated flux locked loop for measuring magnetic fields  

DOEpatents

A system (10) for measuring magnetic fields, wherein the system (10) comprises an unmodulated or direct-feedback flux locked loop (12) connected by first and second unbalanced RF coaxial transmission lines (16a, 16b) to a superconducting quantum interference device (14). The FLL (12) operates for the most part in a room-temperature or non-cryogenic environment, while the SQUID (14) operates in a cryogenic environment, with the first and second lines (16a, 16b) extending between these two operating environments.

Ganther, Jr., Kenneth R. (Olathe, KS); Snapp, Lowell D. (Blue Springs, MO)

2006-08-15

147

The AmeriFlux Network of Long-Term CO{sub 2} Flux Measurement Stations: Methodology and Intercomparability  

SciTech Connect

A portable flux measurement system has been used within the AmeriFlux network of CO{sub 2} flux measurement stations to enhance the comparability of data collected across the network. No systematic biases were observed in a comparison between portable system and site H, LE, or CO{sub 2} flux values although there were biases observed between the portable system and site measurement of air temperature and PPFD. Analysis suggests that if values from two stations differ by greater than 26% for H, 35% for LE, and 32% for CO{sub 2} flux they are likely to be significant. Methods for improving the intercomparability of the network are also discussed.

Hollinger, D. Y.; Evans, R. S.

2003-05-20

148

Performance measurements at the fast flux test facility  

SciTech Connect

In 1984, Fast Flux Test Facility (FFTF) management recognized the need to develop a measurement system that would quantify the operational performance of the FFTF and the human resources needed to operate it. Driven by declining budgets and the need to safely manage a manpower rampdown at FFTF, an early warning system was developed. Although the initiating event for the early warning system was the need to safely manage a manpower rampdown, many related uses have evolved. The initial desired objective for the FFTF performance measurements was to ensure safety and control of key performance trends. However, the early warning system has provided a more quantitative, supportable basis upon which to make decisions. From this initial narrow focus, efforts in the FFTF plant and supporting organizations are leading to measurement of and, subsequently, improvements in productivity. Pilot projects utilizing statistical process control have started with longer range productivity improvement.

Baumhardt, R.J.; Newland, D.J.; Praetorius, P.R.

1987-01-01

149

On inferring isoprene emission surface flux from atmospheric boundary layer concentration measurements  

NASA Astrophysics Data System (ADS)

We examine the dependence of the inferred isoprene surface emission flux from atmospheric concentration on the diurnal variability of the convective boundary layer (CBL). A series of systematic numerical experiments carried out using the mixed-layer technique enabled us to study the sensitivity of isoprene fluxes to the entrainment process, the partition of surface fluxes, the horizontal advection of warm/cold air masses and subsidence. Our findings demonstrate the key role played by the evolution of boundary layer height in modulating the retrieved isoprene flux. More specifically, inaccurate values of the potential temperature lapse rate lead to changes in the dilution capacity of the CBL and as a result the isoprene flux may be overestimated or underestimated by as much as 20%. The inferred emission flux estimated in the early morning hours is highly dependent on the accurate estimation of the discontinuity of the thermodynamic values between the residual layer and the rapidly forming CBL. Uncertainties associated with the partition of the sensible and latent heat flux also yield large deviations in the calculation of the isoprene surface flux. Similar results are obtained if we neglect the influence of warm or cold advection in the development of the CBL. We show that all the above-mentioned processes are non-linear, for which reason the dynamic and chemical evolutions of the CBL must be solved simultaneously. Based on the discussion of our results, we suggest the measurements needed to correctly apply the mixed-layer technique in order to minimize the uncertainties associated with the diurnal variability of the convective boundary layer.

Vilöguerau de Arellano, J.; van den Dries, K.; Pino, D.

2009-02-01

150

On inferring isoprene emission surface flux from atmospheric boundary layer concentration measurements  

NASA Astrophysics Data System (ADS)

We examine the dependence of the inferred isoprene surface emission flux from atmospheric concentration on the diurnal variability of the convective boundary layer (CBL). A series of systematic numerical experiments carried out using the mixed-layer technique enabled us to study the sensitivity of isoprene fluxes to the entrainment process, the partition of surface fluxes, the horizontal advection of warm/cold air masses and subsidence. Our findings demonstrate the key role played by the evolution of boundary layer height in modulating the retrieved isoprene flux. More specifically, inaccurate values of the potential temperature lapse rate lead to changes in the dilution capacity of the CBL and as a result the isoprene flux may be overestimated or underestimated by as much as 20%. The inferred emission flux estimated in the early morning hours is highly dependent on the accurate estimation of the discontinuity of the thermodynamic values between the residual layer and the rapidly forming CBL. Uncertainties associated with the partition of the sensible and latent heat flux also yield large deviations in the calculation of the isoprene surface flux. Similar results are obtained if we neglect the influence of warm or cold advection in the development of the CBL. We show that all the above-mentioned processes are non-linear, for which reason the dynamic and chemical evolutions of the CBL must be solved simultaneously. Based on the discussion of our results, we suggest the measurements needed to correctly apply the mixed-layer technique in order to minimize the uncertainties associated with the diurnal variability of the convective boundary layer.

Vilöguerau de Arellano, J.; van den Dries, K.; Pino, D.

2009-06-01

151

Grasland Stable Isotope Flux Measurements: Three Isotopomers of Carbon Dioxide Measured by QCL Spectroscopy  

NASA Astrophysics Data System (ADS)

To improve our understanding of greenhouse gas dynamics of managed ecosystems such as grasslands, we not only need to investigate the effects of management (e.g., grass cuts) and weather events (e.g., rainy days) on carbon dioxide fluxes, but also need to increase the time resolution of our measurements. Thus, for the first time, we assessed respiration and assimilation fluxes with high time resolution (5Hz) stable isotope measurements at an intensively managed farmland in Switzerland (Chamau, 400m ASL). Two different methods were used to quantify fluxes of carbon dioxide and associated fluxes of stable carbon isotopes: (1) the flux gradient method, and (2) the eddy covariance method. During a week long intensive measurement campaign, we (1) measured mixing ratios of carbon dioxide isotopomers (12C16O2, 12C16O18O, 13C16O2) with a Quantum Cascade Laser (QCL, Aerodyne Inc.) spectroscope and (2) collected air samples for isotope analyses (13C/12C) and (18O/16O) of carbon dioxide by Isotope Ratio Mass Spectrometry (IRMS, Finnigan) every two hours, concurrently along a height profile (z = 0.05; 0.10; 0.31; 2.15m). In the following week, the QCL setup was used for closed-path eddy covariance flux measurement of the carbon dioxide isotopomers, with the air inlet located next to an open-path Infra Red Gas Analyzers (IRGA, LiCor 7500) used simultaneously for carbon dioxide measurements. During this second week, an area of grass inside the footprint was cut and harvested after several days. The first results of in-field continuous QCL measurements of carbon dioxide mixing ratios and their stable isotopic ratios show good agreement with IRGA measurements and isotope analysis of flask samples by IRMS. Thus, QCL spectroscopy is a very promising tool for stable isotope flux investigations.

Zeeman, M. J.; Tuzson, B.; Eugster, W.; Werner, R. A.; Buchmann, N.; Emmenegger, L.

2007-12-01

152

Field Measurements of Isoprene and Monoterpene Emission Rates from Trees.  

NASA Astrophysics Data System (ADS)

Monoterpene emission rates were measured by a branch enclosure technique from Pinus ponderosa in central Oregon in the early summer and fall along with photosynthesis and monoterpene needle concentrations. beta -pinene, Delta^3-carene, and alpha-pinene were the major constituents of the emissions with smaller amounts of myrcene, limonene, and beta-phellandrene. The emission rates of alpha-pinene and beta-pinene were highly correlated with their needle concentrations, while those of Delta ^3-carene were not. There was no discernible effect on emissions when photosynthesis was water stress limited in the fall, and monoterpene emissions appear to be distinct from short term photosynthetic carbon assimilation. Isoprene emission rates were measured from a Quercus robur on the Washington State University campus in the fall of 1989 and throughout the 1990 growing season, and from a Quercus rubra during most of the 1991 season and occasionally in 1992. The measured emission rates showed distinct seasonal patterns which could not be explained by temperature or light. Emission rates were initially low early in the season when the leaves were immature. Rates increased rapidly after leaf maturity to a maximum value and then declined over the rest of the season. Evidence suggests that the rate and magnitude of this decline depends on stresses on the tree. Isoprene emission rates were measured from several species near Oak Ridge, Tennessee. The mean normalized isoprene emission rate from the branch enclosure was compared to the rate measured from a Q. alba leaf in a light and temperature controlled cuvette. The branch enclosure result for Q. alba was about 65% lower than the mean leaf cuvette measurement. This difference appears be due to shading of leaves within the branch enclosure. A comparison was also made between the normalized branch enclosure results and normalized canopy isoprene flux measured by a micrometeorological gradient method with generally good agreement.

Dilts, Stephen Blair

153

Heat flux measurements for use in physiological and clothing research.  

PubMed

Scientists use passive heat flow meters to measure body heat exchanges with the environment. In recent years, several such sensors have been developed and concerns about their proper calibration have been addressed. However, calibration methods have differed in the geometry of the heated device as well as in the heat transfer mechanism. Therefore, a comparison of calibration methods is needed in order to understand the obtained differences in calibration lines. We chose three commercially available heat flux sensors and placed them on four different heated devices: a hot plate, double hot plate, nude cylinder and a cylinder covered with a spacer material. We found differences between the calibration line of the manufacturer and our own measurements, especially when forced convection was involved as the main heat transfer mechanism. The results showed clearly that the calibration method should be chosen according to the intended purpose of use. In addition, we recommend use a thin, light heat flux sensor with good thermal conduction in human subject studies. PMID:23824222

Niedermann, R; Psikuta, A; Rossi, R M

2014-08-01

154

Damping rates of p-modes by an ensemble of randomly distributed thin magnetic flux tubes  

NASA Astrophysics Data System (ADS)

The magnetohydrodynamic (MHD) sausage tube waves are excited in the magnetic flux tubes by p-mode forcing. These tube waves thus carry energy away from the p-mode cavity which results in the deficit of incident p-mode energy. We calculate the loss of incident p-mode energy as a damping rate of f- and p-modes. We calculate the damping rates of f- and p-modes by a model Sun consisting of an ensemble of many thin magnetic flux tubes with varying plasma properties and distributions. Each magnetic flux tube is modelled as axisymmetric, vertically oriented and untwisted. We find that the magnitude and the form of the damping rates are sensitive to the plasma-? of the tubes and the upper boundary condition used.

Gascoyne, Andrew; Jain, Rekha

2011-08-01

155

Absolute measurement of the extreme UV solar flux  

NASA Technical Reports Server (NTRS)

A windowless rare-gas ionization chamber has been developed to measure the absolute value of the solar extreme UV flux in the 50-575-A region. Successful results were obtained on a solar-pointing sounding rocket. The ionization chamber, operated in total absorption, is an inherently stable absolute detector of ionizing UV radiation and was designed to be independent of effects from secondary ionization and gas effusion. The net error of the measurement is + or - 7.3 percent, which is primarily due to residual outgassing in the instrument, other errors such as multiple ionization, photoelectron collection, and extrapolation to the zero atmospheric optical depth being small in comparison. For the day of the flight, Aug. 10, 1982, the solar irradiance (50-575 A), normalized to unit solar distance, was found to be 5.71 + or - 0.42 x 10 to the 10th photons per sq cm sec.

Carlson, R. W.; Ogawa, H. S.; Judge, D. L.; Phillips, E.

1984-01-01

156

Measurement of geothermal flux through poorly consolidated sediments  

USGS Publications Warehouse

In many regions, crystalline rocks are covered by hundreds of meters of unconsolidated and poorly consolidated sediments. Estimates of heat flux within these sediments using standard continental techniques (temperature and conductivity measurements at intervals of 10 to 30 meters) are unreliable, mainly because of the difficulty in obtaining and preserving representative lengths of core. However, it is sometimes feasible to use what amounts to an oceanographic technique by making closely spaced temperature and conductivity measurements within short cored intervals. This is demonstrated in a borehole at Menlo Park, California (37??27???N, 122??10???W, elevation 16 meters), where heat flows determined over 12 separate 1-meter intervls al lie within 10% of their mean value; 2.2 ??cal/cm2 sec. ?? 1968.

Sass, J. H.; Munroe, R. J.; Lachenbruch, A. H.

1968-01-01

157

Temperature and Heat Flux Estimation from Sampled Transient Sensor Measurements Z. C. Feng 1  

E-print Network

Page 1 Temperature and Heat Flux Estimation from Sampled Transient Sensor Measurements Z. C. Feng to calculate the front surface heat input (temperature and heat flux) from the back surface measurements (temperature and/or heat flux) when the front surface measurements are not feasible to obtain. This paper

Montgomery-Smith, Stephen

158

Estimation of VOC emission factors from flux measurements using a receptor model and footprint analysis  

NASA Astrophysics Data System (ADS)

Fluxes of 18 volatile organic compounds (VOCs) collected during May to July 2008 from a tower platform 60 m above the surface in an urban Houston residential area were analyzed using receptor-oriented statistical models and an analytical flux-footprint model to resolve daytime source specific emissions rates. The Multilinear Engine version 2 (ME-2) was used to determine that five sources were responsible for the measured flux at the tower: (i) vehicle exhaust, (ii) a foam plastics industrial source with significant pentane emissions, (iii) consumer and commercial solvent use emissions, (iv) a biogenic emissions source dominated by isoprene, and, (v) evaporative fuel emissions. The estimated median daytime (0700-1900 CST) hourly emission rate from the foam plastics industry was 15.7 ± 3.1 kg h-1, somewhat higher than its permitted hourly emission rates. The median daytime vehicle exhaust VOC emission rate of 14.5 ± 2 g h-1 vehicle-1, was slightly higher than our estimation using the Motor Vehicle Emission Simulator (MOVES) with a county-representative vehicle fleet of year 2008 (11.6 ± 0.2 g h-1 vehicle-1). The median daytime evaporative fuel VOCs emission rate from parked vehicles was 2.3 ± 1.0 g h-1 vehicle-1, which is higher than MOVES estimations and could not be explained by the age of the vehicle fleet, indicating either locally higher evaporative emission sources in the footprint or an underestimation of evaporative emissions by MOVES, or both.

Kota, Sri Harsha; Park, Changhyoun; Hale, Martin C.; Werner, Nicholas D.; Schade, Gunnar W.; Ying, Qi

2014-01-01

159

Local Heat Flux Measurements with Single Element Coaxial Injectors  

NASA Technical Reports Server (NTRS)

To support the mission for the NASA Vision for Space Exploration, the NASA Marshall Space Flight Center conducted a program in 2005 to improve the capability to predict local thermal compatibility and heat transfer in liquid propellant rocket engine combustion devices. The ultimate objective was to predict and hence reduce the local peak heat flux due to injector design, resulting in a significant improvement in overall engine reliability and durability. Such analyses are applicable to combustion devices in booster, upper stage, and in-space engines, as well as for small thrusters with few elements in the injector. In this program, single element and three-element injectors were hot-fire tested with liquid oxygen and ambient temperature gaseous hydrogen propellants at The Pennsylvania State University Cryogenic Combustor Laboratory from May to August 2005. Local heat fluxes were measured in a 1-inch internal diameter heat sink combustion chamber using Medtherm coaxial thermocouples and Gardon heat flux gauges. Injectors were tested with shear coaxial and swirl coaxial elements, including recessed, flush and scarfed oxidizer post configurations, and concentric and non-concentric fuel annuli. This paper includes general descriptions of the experimental hardware, instrumentation, and results of the hot-fire testing for three of the single element injectors - recessed-post shear coaxial with concentric fuel, flush-post swirl coaxial with concentric fuel, and scarfed-post swirl coaxial with concentric fuel. Detailed geometry and test results will be published elsewhere to provide well-defined data sets for injector development and model validatation.

Jones, Gregg; Protz, Christopher; Bullard, Brad; Hulka, James

2006-01-01

160

Calorimeter probes for measuring high thermal flux. [in electric-arc jet facilities for planetary entry heating simulation  

NASA Technical Reports Server (NTRS)

The paper describes expendable, slug-type calorimeter probes developed for measuring high heat-flux levels of 10-30 kW/sq cm in electric-arc jet facilities. The probes are constructed with thin tungsten caps mounted on Teflon bodies; the temperature of the back surface of the tungsten cap is measured, and its rate of change gives the steady-state, absorbed heat flux as the calorimeter probe heats to destruction when inserted into the arc jet. It is concluded that the simple construction of these probes allows them to be expendable and heated to destruction to obtain a measurable temperature slope at high heating rates.

Russell, L. D.

1979-01-01

161

[Application of SOF-FTIR method to measuring ammonia emission flux of chemical plant].  

PubMed

In the present paper, a new method is introduced for real-time monitoring polluted gas emission flux of chemical plant, which is called FTIR based on the solar occultation flux technique (SOF-FTIR). The model to obtain background spectrum, measured spectrum and atmospheric penetration rate surrounding polluted gas under complicated conditions is also proposed. Continuous measurements were preformed at a closed loop surrounding the contaminated areas that need to be mornitored to obtain measured spectrum, and finally column concentration of polluted gas was retrieved by using the nonlinear least squares fitting algorithm (NLLS). Then the flux information combined with the meteorological data and GPS information of the time was obtained when the experiments were done. Using this method, remote sensing experiment of ammonia emission around a chemical plant was done, and the concentration distribution and its emission flux was quantitatively analyzed. Compared with traditional FTIR methods of monitoring, this method is featured by convenient operation and high maneuverability, so it has a good application prospect in pollution monitoring and other applications in regional air pollution contingency monitoring. PMID:20707133

Jin, Ling; Gao, Min-Guang; Liu, Wen-Qing; Lu, Yi-Huai; Zhang, Yu-Jun; Wang, Ya-Ping; Zhang, Tian-Shu; Xu, Liang; Liu, Zhi-Ming; Chen, Jun

2010-06-01

162

Measurements for the JASPER Program Flux Monitor Experiment  

SciTech Connect

The Flux Monitor Experiment was conducted at the Oak Ridge National Laboratory (ORNL) Tower Shielding Facility (TSF) during the months of May and June 1992, as part of the continuing series of eight experiments planned for the Japanese-American Shielding Program for Experimental Research (JASPER) program that was started in 1986. This series of experiments was designed to examine shielding concerns and radiation transport effects pertaining to in-vessel flux monitoring systems (FMS) in current reactor shield designs proposed for both the Advanced Liquid Metal Reactor (ALMR) design and the Japanese loop-type design. The program is a cooperative effort between the United States Department of Energy (US DOE) and the Japanese Power Reactor and Nuclear Fuel Development Corporation (PNC). The Tower Shielding Reactor H (TSR-II) neutron source was altered by the spectrum modifier (SM) used previously in the Axial Shield Experiment, and part of the Japanese Removable Radial Shield (RRS) before reaching the axial shield. In the axial shield were placed six homogeneous boron carbide (B{sub 4}C) hexagons around a center hexagon of aluminum used to represent sodium. Shield designs to be studied were placed beyond the axial shield, each design forming a void directly behind the axial shield. Measurements were made in the void and behind each slab as successive slabs were added.

Muckenthaler, F.J.; Spencer, R.R.; Hunter, H.T.; Hull, J.L. [Oak Ridge National Lab., TN (United States); Shono, A. [Power Reactor and Nuclear Fuel Development Corp., Oarai, Ibaraki (Japan). Oarai Engineering Center

1993-02-01

163

Measurement of the atmospheric ?e flux in IceCube.  

PubMed

We report the first measurement of the atmospheric electron neutrino flux in the energy range between approximately 80 GeV and 6 TeV, using data recorded during the first year of operation of IceCube's DeepCore low-energy extension. Techniques to identify neutrinos interacting within the DeepCore volume and veto muons originating outside the detector are demonstrated. A sample of 1029 events is observed in 281 days of data, of which 496±66(stat)±88(syst) are estimated to be cascade events, including both electron neutrino and neutral current events. The rest of the sample includes residual backgrounds due to atmospheric muons and charged current interactions of atmospheric muon neutrinos. The flux of the atmospheric electron neutrinos is consistent with models of atmospheric neutrinos in this energy range. This constitutes the first observation of electron neutrinos and neutral current interactions in a very large volume neutrino telescope optimized for the TeV energy range. PMID:25167245

Aartsen, M G; Abbasi, R; Abdou, Y; Ackermann, M; Adams, J; Aguilar, J A; Ahlers, M; Altmann, D; Auffenberg, J; Bai, X; Baker, M; Barwick, S W; Baum, V; Bay, R; Beattie, K; Beatty, J J; Bechet, S; Becker Tjus, J; Becker, K-H; Bell, M; Benabderrahmane, M L; BenZvi, S; Berdermann, J; Berghaus, P; Berley, D; Bernardini, E; Bernhard, A; Bertrand, D; Besson, D Z; Bindig, D; Bissok, M; Blaufuss, E; Blumenthal, J; Boersma, D J; Bohaichuk, S; Bohm, C; Bose, D; Böser, S; Botner, O; Brayeur, L; Brown, A M; Bruijn, R; Brunner, J; Buitink, S; Carson, M; Casey, J; Casier, M; Chirkin, D; Christy, B; Clark, K; Clevermann, F; Cohen, S; Cowen, D F; Cruz Silva, A H; Danninger, M; Daughhetee, J; Davis, J C; De Clercq, C; De Ridder, S; Desiati, P; de Vries-Uiterweerd, G; de With, M; DeYoung, T; Díaz-Vélez, J C; Dreyer, J; Dunkman, M; Eagan, R; Eberhardt, B; Eisch, J; Ellsworth, R W; Engdegård, O; Euler, S; Evenson, P A; Fadiran, O; Fazely, A R; Fedynitch, A; Feintzeig, J; Feusels, T; Filimonov, K; Finley, C; Fischer-Wasels, T; Flis, S; Franckowiak, A; Franke, R; Frantzen, K; Fuchs, T; Gaisser, T K; Gallagher, J; Gerhardt, L; Gladstone, L; Glüsenkamp, T; Goldschmidt, A; Golup, G; Goodman, J A; Góra, D; Grant, D; Groß, A; Gurtner, M; Ha, C; Haj Ismail, A; Hallgren, A; Halzen, F; Hanson, K; Heereman, D; Heimann, P; Heinen, D; Helbing, K; Hellauer, R; Hickford, S; Hill, G C; Hoffman, K D; Hoffmann, R; Homeier, A; Hoshina, K; Huelsnitz, W; Hulth, P O; Hultqvist, K; Hussain, S; Ishihara, A; Jacobi, E; Jacobsen, J; Japaridze, G S; Jero, K; Jlelati, O; Kaminsky, B; Kappes, A; Karg, T; Karle, A; Kelley, J L; Kiryluk, J; Kislat, F; Kläs, J; Klein, S R; Köhne, J-H; Kohnen, G; Kolanoski, H; Köpke, L; Kopper, C; Kopper, S; Koskinen, D J; Kowalski, M; Krasberg, M; Kroll, G; Kunnen, J; Kurahashi, N; Kuwabara, T; Labare, M; Landsman, H; Larson, M J; Lesiak-Bzdak, M; Leute, J; Lünemann, J; Madsen, J; Maruyama, R; Mase, K; Matis, H S; McNally, F; Meagher, K; Merck, M; Mészáros, P; Meures, T; Miarecki, S; Middell, E; Milke, N; Miller, J; Mohrmann, L; Montaruli, T; Morse, R; Nahnhauer, R; Naumann, U; Niederhausen, H; Nowicki, S C; Nygren, D R; Obertacke, A; Odrowski, S; Olivas, A; Olivo, M; O'Murchadha, A; Panknin, S; Paul, L; Pepper, J A; Pérez de los Heros, C; Pfendner, C; Pieloth, D; Pirk, N; Posselt, J; Price, P B; Przybylski, G T; Rädel, L; Rawlins, K; Redl, P; Resconi, E; Rhode, W; Ribordy, M; Richman, M; Riedel, B; Rodrigues, J P; Rott, C; Ruhe, T; Ruzybayev, B; Ryckbosch, D; Saba, S M; Salameh, T; Sander, H-G; Santander, M; Sarkar, S; Schatto, K; Scheel, M; Scheriau, F; Schmidt, T; Schmitz, M; Schoenen, S; Schöneberg, S; Schönherr, L; Schönwald, A; Schukraft, A; Schulte, L; Schulz, O; Seckel, D; Seo, S H; Sestayo, Y; Seunarine, S; Sheremata, C; Smith, M W E; Soiron, M; Soldin, D; Spiczak, G M; Spiering, C; Stamatikos, M; Stanev, T; Stasik, A; Stezelberger, T; Stokstad, R G; Stößl, A; Strahler, E A; Ström, R; Sullivan, G W; Taavola, H; Taboada, I; Tamburro, A; Ter-Antonyan, S; Tilav, S; Toale, P A; Toscano, S; Usner, M; van der Drift, D; van Eijndhoven, N; Van Overloop, A; van Santen, J; Vehring, M; Voge, M; Vraeghe, M; Walck, C; Waldenmaier, T; Wallraff, M; Wasserman, R; Weaver, Ch; Wellons, M; Wendt, C; Westerhoff, S; Whitehorn, N; Wiebe, K; Wiebusch, C H; Williams, D R; Wissing, H; Wolf, M; Wood, T R; Woschnagg, K; Xu, C; Xu, D L; Xu, X W; Yanez, J P; Yodh, G; Yoshida, S; Zarzhitsky, P; Ziemann, J; Zierke, S; Zilles, A; Zoll, M

2013-04-12

164

Measurement of the 36Cl deposition flux in central Japan: natural background levels and seasonal variability.  

PubMed

Essential parameters for the applications of (36)Cl as a tracer in groundwater studies include the initial (36)Cl/Cl ratio, at the time of recharge, and/or the natural background deposition flux of (36)Cl in the recharge area. To facilitate the hydrological use of (36)Cl in central Japan, this study aimed to obtain a precise estimate of the long-term average local (36)Cl flux and to characterize its seasonal variability. The (36)Cl in precipitation was continuously monitored in Tsukuba, central Japan over a period of >5 years. The (36)Cl flux showed a clear seasonal variation with an annual peak during the spring, which was attributed to the seasonal variability of tropopause height. The long-term average (36)Cl flux (32±2atoms m(-2)s(-1)), estimated from the measured data, was consistent with the prediction from the (36)Cl latitudinal fallout model scaled using the global mean production rate of 20atoms m(-2)s(-1). The initial (36)Cl/Cl ratio was estimated to be (41±6)×10(-15), which is similar to that of pre-bomb groundwater in the Tsukuba Upland. An observation period covering an 11-year solar cycle would yield more accurate estimates of the values, given the increased (36)Cl flux during the solar minimum. PMID:22305003

Tosaki, Yuki; Tase, Norio; Sasa, Kimikazu; Takahashi, Tsutomu; Nagashima, Yasuo

2012-04-01

165

Angular-Rate Estimation Using Quaternion Measurements  

NASA Technical Reports Server (NTRS)

In most spacecraft (SC) there is a need to know the SC angular rate. Precise angular rate is required for attitude determination, and a coarse rate is needed for attitude control damping. Classically, angular rate information is obtained from gyro measurements. These days, there is a tendency to build smaller, lighter and cheaper SC, therefore the inclination now is to do away with gyros and use other means and methods to determine the angular rate. The latter is also needed even in gyro equipped satellites when performing high rate maneuvers whose angular-rate is out of range of the on board gyros or in case of gyro failure. There are several ways to obtain the angular rate in a gyro-less SC. When the attitude is known, one can differentiate the attitude in whatever parameters it is given and use the kinematics equation that connects the derivative of the attitude with the satellite angular-rate and compute the latter. Since SC usually utilize vector measurements for attitude determination, the differentiation of the attitude introduces a considerable noise component in the computed angular-rate vector.

Azor, Ruth; Bar-Itzhack, Y.; Deutschmann, Julie K.; Harman, Richard R.

1998-01-01

166

In-situ, high spatio-temporal resolution measurements of CO2 flux and isotopic composition on Mammoth Mountain, CA  

NASA Astrophysics Data System (ADS)

Measurement of CO2 emissions from volcano flanks and in ground waters has become an integral part of many monitoring programs, as spatial and temporal variations in these emissions may be indicative of volcanic unrest. The source and magnitude of CO2 emissions have been intensely studied at Mammoth Mountain, a dacitic volcano located on the rim of Long Valley caldera, California. These observations, combined with multiple geophysical data sets, suggest that unrest at Mammoth Mountain is driven by periodic release of CO2-rich magmatic fluid derived from basaltic dikes and sills at mid-crustal depths. While measurements of CO2 flux and determination of CO2 sources at volcanoes can place important constraints on gas transport and its relationship to volcanic activity, the spatio-temporal resolution of these measurements has been limited by the time and cost associated with making “point” CO2 flux measurements using the accumulation chamber (AC) method and sample collection and analysis of isotopic (14C-CO2 and 13C-CO2) compositions. We present a novel instrument platform for real-time monitoring of spatio-temporal distribution, emission rate and source of CO2 in volcanic systems. Time and space averaged CO2 fluxes are measured every half hour by the eddy covariance (EC) method. Least-squares inversions of EC data and modeled footprint functions provide estimates of CO2 emission rate and surface flux spatial distribution. AC measurements of soil CO2 flux yield detailed maps of flux spatial distribution and comparative emission rate estimates. A new field-portable isotopic analyzer provides, for the first time, in-situ, high frequency measurements of 14C and 13C compositions of CO2 in the atmosphere, soil gas, and dissolved in ground water. We tested the CO2 flux-monitoring component of this platform at the Horseshoe Lake tree kill area on Mammoth Mountain from 8 September to 24 October 2006. EC CO2 fluxes ranged from 218 to 3500 g m-2d-1. Maps of surface CO2 flux were simulated based on AC measurements made repeatedly on a grid over a ten-day period; large meteorologically driven variations in surface flux distributions and emission rates (16 to 52 t d-1) were observed. Using footprint modeling, we compared EC to AC measurements of CO2 flux. Half-hour EC CO2 fluxes were moderately correlated (R2 = 0.42) with AC fluxes, whereas average-daily EC and AC fluxes were well correlated (R2 = 0.70). The integrated CO2 flux and isotopic monitoring platform will be deployed and tested in Fall 2010 at Mammoth Mountain. EC and AC measurements of CO2 fluxes will be made at the Horseshoe Lake tree kill area and modeled CO2 surface flux distributions and emission rates will be compared. Measurements of 14C and 13C compositions of atmospheric, soil, and ground water CO2 will provide real-time determination of CO2 source.

Lewicki, J. L.; Hilley, G. E.; Marino, B.; Bergfeld, D.; Fischer, M. L.; Hancyk, J.; Xu, L.

2010-12-01

167

Heart Rate Detection from Plantar Bioimpedance Measurements  

Microsoft Academic Search

The heart rate is a basic health indicator, useful in both clinical measurements and home health care. Current home care systems often require the attachment of electrodes or other sensors to the body, which can be cumbersome to the patient. Moreover, some measurements are sensitive to movement artifacts, are not user-friendly and require a specialized supervision. In this paper, a

R. González Landaeta; O. Casas; R. Pallas-Areny

2006-01-01

168

Chamber and Diffusive Based Carbon Flux Measurements in an Alaskan Arctic Ecosystem  

NASA Astrophysics Data System (ADS)

Eric Wilkman, Walter Oechel, Donatella Zona Comprising an area of more than 7 x 106 km2 and containing over 11% of the world's organic matter pool, Arctic terrestrial ecosystems are vitally important components of the global carbon cycle, yet their structure and functioning are sensitive to subtle changes in climate and many of these functional changes can have large effects on the atmosphere and future climate regimes (Callaghan & Maxwell 1995, Chapin et al. 2002). Historically these northern ecosystems have acted as strong C sinks, sequestering large stores of atmospheric C due to photosynthetic dominance in the short summer season and low rates of decomposition throughout the rest of the year as a consequence of cold, nutrient poor, and generally water-logged conditions. Currently, much of this previously stored carbon is at risk of loss to the atmosphere due to accelerated soil organic matter decomposition in warmer future climates (Grogan & Chapin 2000). Although there have been numerous studies on Arctic carbon dynamics, much of the previous soil flux work has been done at limited time intervals, due to both the harshness of the environment and labor and time constraints. Therefore, in June of 2013 an Ultraportable Greenhouse Gas Analyzer (UGGA - Los Gatos Research Inc.) was deployed in concert with the LI-8100A Automated Soil Flux System (LI-COR Biosciences) in Barrow, AK to gather high temporal frequency soil CO2 and CH4 fluxes from a wet sedge tundra ecosystem. An additional UGGA in combination with diffusive probes, installed in the same location, provides year-round soil and snow CO2 and CH4 concentrations. When used in combination with the recently purchased AlphaGUARD portable radon monitor (Saphymo GmbH), continuous soil and snow diffusivities and fluxes of CO2 and CH4 can be calculated (Lehmann & Lehmann 2000). Of particular note, measuring soil gas concentration over a diffusive gradient in this way allows one to separate both net production and consumption, whereas chamber and eddy covariance methodologies only document net production from the surface. Also, the capability to measure spring, summer and fall chamber fluxes, and to continuously determine year-round CO2 and CH4 fluxes under even the most extreme weather conditions, allows an unprecedented level of data continuity and local spatial coverage. Comparison to a nearby eddy covariance tower measuring CO2 and CH4 fluxes with an LGR Fast Greenhouse Gas Analyzer add additional power to this set of measurements. Thus, inter-comparison between diffusive, chamber, and tower-based carbon fluxes should lend much insight into the spatial and temporal controls on carbon cycling in this ecosystem.

Wilkman, E.; Oechel, W. C.; Zona, D.

2013-12-01

169

First UAV Measurements of Entrainment Layer Fluxes with Coupled Cloud Property Measurements  

NASA Astrophysics Data System (ADS)

This study details entrainment flux measurements made from a lightweight unmanned aerial vehicle (UAV) containing turbulent water vapor flux instrumentation (Thomas et al., 2012). The system was flown for 26 flights during the Cloud, Aerosol, Radiative forcing, Dynamics EXperiment (CARDEX) in the Maldives in March 2012 to study interrelationships between entrainment, aerosols, water budget, cloud microphysics and radiative fluxes in a trade wind cumulus cloud regime. A major advantage of using this lightweight, precision autopiloted UAV system with scientific telemetry is the ability to target small-scale features in the boundary layer, such as an entrainment layer, with minimal aircraft induced disruption. Results are presented from two UAVs flown in stacked formation: one UAV situated in-cloud measuring cloud-droplet size distribution spectra and liquid water content, and another co-located 100m above measuring turbulent properties and entrainment latent heat flux (?EE). We also show latent heat flux and turbulence measurements routinely made at the entrainment layer base and altitudes from the surface up to 4kft. Ratios of ?EE to corresponding surface tower values (?ES) display a bimodal frequency distribution with ranges 0.22-0.53 and 0.79-1.5, with occasional events >7. Reasons for this distribution are discussed drawing upon boundary layer and free tropospheric dynamics and meteorology, turbulence length scales, surface conditions, and cloud interactions. Latent heat flux profiles are combined with in-cloud UAV Liquid Water Content (LWC) data and surface based Liquid Water Path (LWP) and Precipitable Water Vapor (PWV) measurements to produce observationally constrained vertical water budgets, providing insights into diurnal coupling of ?EE and ?ES. Observed ?EE, ?ES, water budgets, and cloud microphysical responses to entrainment are then contextualized with respect to measured aerosol loading profiles and airmass history.

Thomas, R. M.; Praveen, P. S.; Wilcox, E. M.; Pistone, K.; Bender, F.; Ramanathan, V.

2012-12-01

170

FFTF (Fast Flux Test Facility) Integrated Leak Rate Test Computer System  

Microsoft Academic Search

The Fast Flux Test Facility (FFTF) is a liquid-metal-cooled test reactor located on the Hanford Site. The FFTF is the only reactor of this type designed and operated with the intent of meeting the licensing requirements of the Nuclear Regulatory Commission (NRC). Unique characteristics of the FFTF that present special challenges related to leak rate testing include thin wall containment

Hubbard

1987-01-01

171

Fieldable computer system for determining gamma-ray pulse-height distributions, flux spectra, and dose rates from Little Boy  

SciTech Connect

Our system consists of a LeCroy 3500 data acquisition system with a built-in CAMAC crate and eight bismuth-germanate detectors 7.62 cm in diameter and 7.62 cm long. Gamma-ray pulse-height distributions are acquired simultaneously for up to eight positions. The system was very carefully calibrated and characterized from 0.1 to 8.3 MeV using gamma-ray spectra from a variety of radioactive sources. By fitting the pulse-height distributions from the sources with a function containing 17 parameters, we determined theoretical repsonse functions. We use these response functions to unfold the distributions to obtain flux spectra. A flux-to-dose-rate conversion curve based on the work of Dimbylow and Francis is then used to obtain dose rates. Direct use of measured spectra and flux-to-dose-rate curves to obtain dose rates avoids the errors that can arise from spectrum dependence in simple gamma-ray dosimeter instruments. We present some gamma-ray doses for the Little Boy assembly operated at low power. These results can be used to determine the exposures of the Hiroshima survivors and thus aid in the establishment of radation exposure limits for the nuclear industry.

Moss, C.E.; Lucas, M.C.; Tisinger, E.W.; Hamm, M.E.

1984-01-01

172

A novel approach to measuring heat flux in swimming animals Kate Willis*, Markus Horning  

E-print Network

A novel approach to measuring heat flux in swimming animals Kate Willis*, Markus Horning Laboratory measurements of heat flux from animal experiments to account for the thermal resistance of HFSs and insulative 22 September 2004 Abstract We present a design for long-term or removable attachment of heat flux

173

Prediction and measurement of incipient boiling heat flux in micro-channel heat sinks  

E-print Network

Prediction and measurement of incipient boiling heat flux in micro-channel heat sinks Weilin Qu Abstract Experiments were performed to measure the incipient boiling heat flux in a heat sink containing 21 to predict the incipient boiling heat flux, accounting for the complexities of bubble formation along

Qu, Weilin

174

Investigation of Flux Linkage Profile Measurement Methods for Switched Reluctance Motors and Permanent Magnet  

E-print Network

- 1 - Investigation of Flux Linkage Profile Measurement Methods for Switched Reluctance Motors and Permanent Magnet Motors K. Y. Lu, P. O. Rasmussen, A. E. Ritchie Abstract ­ Knowledge of actual flux linkage pure AC flux linkage measurement method is discussed and evaluated, which does not require a search

Lu, Kaiyuan

175

Comparative soil CO2 flux measurements and geostatistical estimation methods on Masaya volcano, Nicaragua  

USGS Publications Warehouse

We present a comparative study of soil CO2 flux (FCO2) measured by five groups (Groups 1-5) at the IAVCEI-CCVG Eighth Workshop on Volcanic Gases on Masaya volcano, Nicaragua. Groups 1-5 measured (FCO2) using the accumulation chamber method at 5-m spacing within a 900 m2 grid during a morning (AM) period. These measurements were repeated by Groups 1-3 during an afternoon (PM) period. Measured (FCO2 ranged from 218 to 14,719 g m-2 day-1. The variability of the five measurements made at each grid point ranged from ??5 to 167%. However, the arithmetic means of fluxes measured over the entire grid and associated total CO2 emission rate estimates varied between groups by only ??22%. All three groups that made PM measurements reported an 8-19% increase in total emissions over the AM results. Based on a comparison of measurements made during AM and PM times, we argue that this change is due in large part to natural temporal variability of gas flow, rather than to measurement error. In order to estimate the mean and associated CO2 emission rate of one data set and to map the spatial FCO2 distribution, we compared six geostatistical methods: Arithmetic and minimum variance unbiased estimator means of uninterpolated data, and arithmetic means of data interpolated by the multiquadric radial basis function, ordinary kriging, multi-Gaussian kriging, and sequential Gaussian simulation methods. While the total CO2 emission rates estimated using the different techniques only varied by ??4.4%, the FCO2 maps showed important differences. We suggest that the sequential Gaussian simulation method yields the most realistic representation of the spatial distribution of FCO2, but a variety of geostatistical methods are appropriate to estimate the total CO2 emission rate from a study area, which is a primary goal in volcano monitoring research. ?? Springer-Verlag 2005.

Lewicki, J. L.; Bergfeld, D.; Cardellini, C.; Chiodini, G.; Granieri, D.; Varley, N.; Werner, C.

2005-01-01

176

Evidence for electron neutrino flavor change through measurement of the (8)B solar neutrino flux at the Sudbury Neutrino Observatory  

NASA Astrophysics Data System (ADS)

The Sudbury Neutrino Observatory (SNO) is a water Cerenkov detector designed to study solar neutrinos. Using 1 kiloton of heavy water as the target and detection medium, SNO is able to separately determine the flux of electron neutrinos (?e) and the flux of all active neutrinos from the Sun by measuring the rate of charged current (CC) and neutral current (NC) interactions with deuterons. A comparison of these interaction rates allows for direct observation of solar neutrino oscillations. SNO can also search for oscillations by comparing the rate of CC and neutrino- electron elastic scattering (ES) events, since ES has both charged current and neutral current sensitivity. In this thesis, we present measurement of the 8B solar ? e flux of 1.78+0.13-0.14 (stat+syst) × 106cm-2s -1 (35% BP2000 SSM) through measurement of the CC rate over 169.3 days of livetime. We have also measured the 8B flux from the ES reaction to be 2.56+0.48-0.45 (stat+syst), consistent with measurements by previous water Cerenkov experiments. A flavor analysis comparing the CC measured flux with that determined through ES by SuperKamiokande yields a non- ?e active neutrino flux from 8B of 3.62+1.06-1.08 × 106cm-2s-1 , providing evidence for ?e --> ? ?,? oscillations as a solution to the solar neutrino problem. This result excludes pure solar ?e --> ? s oscillations at greater than the 99.7% C.I. The total active 8B neutrino flux has been measured to be 5.39+1.07-1.09 × 106cm-2s-1 , consistent with BP2000 SSM predictions. First analyses of the CC (NHit) spectrum and hep flux in SNO are presented. The CC spectrum is found to be a good fit to expectations from an undistorted 8B spectrum, and global best fit vacuum oscillation solutions are disfavored over the other solutions by the data. Through observations near the 8B endpoint with consideration of energy systematics, hep flux limits of 4.1 (90% C.I.) and 6.9 (99% C.I.) times SSM expectations are obtained. A statistical fit for the hep flux signal yields a 3? upper limit of 3.2 times the SSM expected flux.

Neubauer, Mark Stephen

2001-11-01

177

Just Breathe Green: Measuring Transpiration Rates  

NSDL National Science Digital Library

Through multi-trial experiments, students are able to see and measure something that is otherwise invisible to themâseeing plants breathe. Student groups are given two small plants of native species and materials to enclose them after watering with colored water. After being enclosed for 5, 10 and 15 minutes, teams collect and measure the condensed water from the plants' "breathing," and then calculate the rates at which the plants breathe. A plant's breath is known as transpiration, which is the flow of water from the ground where it is taken up by roots (plant uptake) and then lost through the leaves. Students plot volume/time data for three different native plant species, determine and compare their transpiration rates to see which had the highest reaction rate and consider how a plant's unique characteristics (leaf surface area, transpiration rate) might figure into engineers' designs for neighborhood stormwater management plans.

Water Awareness Research and Education (WARE) Research Experience for Teachers (RET),

178

Steady-state nucleation rate and flux of composite nucleus at saddle point.  

PubMed

The steady-state nucleation rate and flux of composite nucleus at the saddle point is studied by extending the theory of binary nucleation. The Fokker-Planck equation that describes the nucleation flux is derived using the Master equation for the growth of the composite nucleus, which consists of the core of the final stable phase surrounded by a wetting layer of the intermediate metastable phase nucleated from a metastable parent phase recently evaluated by Iwamatsu [J. Chem. Phys. 134, 164508 (2011)]. The Fokker-Planck equation is similar to that used in the theory of binary nucleation, but the non-diagonal elements exist in the reaction rate matrix. First, the general solution for the steady-state nucleation rate and the direction of nucleation flux is derived. Next, this information is then used to study the nucleation of composite nucleus at the saddle point. The dependence of steady-state nucleation rate as well as the direction of nucleation flux on the reaction rate in addition to the free-energy surface is studied using a model free-energy surface. The direction of nucleation current deviates from the steepest-descent direction of the free-energy surface. The results show the importance of two reaction rate constants: one from the metastable environment to the intermediate metastable phase and the other from the metastable intermediate phase to the stable new phase. On the other hand, the gradient of the potential ? or the Kramers crossover function (the commitment or splitting probability) is relatively insensitive to reaction rates or free-energy surface. PMID:22667576

Iwamatsu, Masao

2012-05-28

179

Steady-state nucleation rate and flux of composite nucleus at saddle point  

NASA Astrophysics Data System (ADS)

The steady-state nucleation rate and flux of composite nucleus at the saddle point is studied by extending the theory of binary nucleation. The Fokker-Planck equation that describes the nucleation flux is derived using the Master equation for the growth of the composite nucleus, which consists of the core of the final stable phase surrounded by a wetting layer of the intermediate metastable phase nucleated from a metastable parent phase recently evaluated by Iwamatsu [J. Chem. Phys. 134, 164508 (2011)]. The Fokker-Planck equation is similar to that used in the theory of binary nucleation, but the non-diagonal elements exist in the reaction rate matrix. First, the general solution for the steady-state nucleation rate and the direction of nucleation flux is derived. Next, this information is then used to study the nucleation of composite nucleus at the saddle point. The dependence of steady-state nucleation rate as well as the direction of nucleation flux on the reaction rate in addition to the free-energy surface is studied using a model free-energy surface. The direction of nucleation current deviates from the steepest-descent direction of the free-energy surface. The results show the importance of two reaction rate constants: one from the metastable environment to the intermediate metastable phase and the other from the metastable intermediate phase to the stable new phase. On the other hand, the gradient of the potential ? or the Kramers crossover function (the commitment or splitting probability) is relatively insensitive to reaction rates or free-energy surface.

Iwamatsu, Masao

2012-05-01

180

Energetic ion diagnostics using neutron flux measurements during pellet injection  

SciTech Connect

Neutron measurements during injection of deuterium pellets into deuterium plasmas on the Tokamak Fusion Test Reactor (TFTR) indicate that the fractional increase in neutron emission about 0.5 msec after pellet injection is proportional to the fraction of beam-plasma reactions to total fusion reactions in the unperturbed plasma. These observations suggest three diagnostic applications of neutron measurements during pellet injection: (1) measurement of the beam-plasma reaction rate in deuterium plasmas for use in determining the fusion Q in an equivalent deuterium-tritium plasma, (2) measurement of the radial profile of energetic beam ions by varying the pellet size and velocity, and (3) measurement of the ''temperature'' of ions accelerated during wave heating. 18 refs., 3 figs.

Heidbrink, W.W.

1986-01-01

181

Time and space resolved wall temperature and heat flux measurements during nucleate boiling with constant heat flux boundary conditions  

Microsoft Academic Search

The lack of time and space resolved measurements under nucleating bubbles has complicated efforts to fully explain pool-boiling phenomena. In this work, time and space resolved temperature and heat flux distributions under nucleating bubbles on a constant heat flux surface were obtained using a 10×10 microheater array with 100?m resolution along with high-speed images. A numerical simulation was used to

Jerry G. Myers; Vamsee K. Yerramilli; Sam W. Hussey; Glenda F. Yee; Jungho Kim

2005-01-01

182

Ways of measuring rates of recurrent events.  

PubMed Central

Recurrent events are common in medical research, yet the best ways to measure their occurrence remain controversial. Moreover, the correct statistical techniques to compare the occurrence of such events across populations or treatment groups are not widely known. In both observational studies and randomised clinical trials one natural and intuitive measure of occurrence is the event rate, defined as the number of events (possibly including multiple events per person) divided by the total person-years of experience. This is often a more relevant and clinically interpretable measure of disease burden in a population than considering only the first event that occurs. Appropriate statistical tests to compare such event rates among treatment groups or populations require the recognition that some individuals may be especially likely to experience recurrent events. Straightforward approaches are available to account for this tendency in crude and stratified analyses. Recently developed regression models can appropriately examine the association of several variables with rates of recurrent events. PMID:8611837

Glynn, R. J.; Buring, J. E.

1996-01-01

183

Optimization of magnetic flux density measurement using multiple RF receiver coils and multi-echo in MREIT  

NASA Astrophysics Data System (ADS)

Magnetic Resonance Electrical Impedance Tomography (MREIT) is an MRI method that enables mapping of internal conductivity and/or current density via measurements of magnetic flux density signals. The MREIT measures only the z-component of the induced magnetic flux density B = (Bx, By, Bz) by external current injection. The measured noise of Bz complicates recovery of magnetic flux density maps, resulting in lower quality conductivity and current-density maps. We present a new method for more accurate measurement of the spatial gradient of the magnetic flux density gradient (? Bz). The method relies on the use of multiple radio-frequency receiver coils and an interleaved multi-echo pulse sequence that acquires multiple sampling points within each repetition time. The noise level of the measured magnetic flux density Bz depends on the decay rate of the signal magnitude, the injection current duration, and the coil sensitivity map. The proposed method uses three key steps. The first step is to determine a representative magnetic flux density gradient from multiple receiver coils by using a weighted combination and by denoising the measured noisy data. The second step is to optimize the magnetic flux density gradient by using multi-echo magnetic flux densities at each pixel in order to reduce the noise level of ? Bz and the third step is to remove a random noise component from the recovered ? Bz by solving an elliptic partial differential equation in a region of interest. Numerical simulation experiments using a cylindrical phantom model with included regions of low MRI signal to noise (‘defects’) verified the proposed method. Experimental results using a real phantom experiment, that included three different kinds of anomalies, demonstrated that the proposed method reduced the noise level of the measured magnetic flux density. The quality of the recovered conductivity maps using denoised ? Bz data showed that the proposed method reduced the conductivity noise level up to 3–4 times at each anomaly region in comparison to the conventional method.

Jeong, Woo Chul; Chauhan, Munish; Sajib, Saurav Z. K.; Kim, Hyung Joong; Serša, Igor; In Kwon, Oh; Woo, Eung Je

2014-09-01

184

The BESS-Polar Proton & Helium flux measurements  

NASA Astrophysics Data System (ADS)

The Balloon-borne Experiment with a Superconducting Spectrometer (BESS) instrument pro-vides precise measurements of the elemental and isotopic composition of the light Galactic cosmic radiation (GCR) component. The ability to determine the charge sign of incident par-ticles enables the instrument to search for GCR antimatter, which is a major objective of the BESS program. Since 1993, the US-Japan BESS collaboration has conducted 11 successful balloon flights, nine northern-latitude flights of 1-day duration and most recently two long-duration balloon flights (8.5 days in 2004 & 24.5 days in 2007/2008), with the BESS-Polar instrument. The BESS-Polar instrument is the current effort of BESS program specifically designed for long-duration, low-geomagnetic cutoff Antarctic flights with significantly increased transparency for incident CR particle allowing to study anti/proton down to 100 MeV and a faster data acquisition enables processing of all CR events without event selection. The first BESS-Polar flight was launched on Dec 13, 2004 from Williams Field, near McMurdo Station in Antarctica. The instrument recorded data for 8.5 days, limited by the cryogenic life time of the superconducting magnet. During this flight the BESS-Polar instrument recorded 0.9 x 109 CR events. In this paper, we present the absolute proton and helium flux for the first BESS-Polar flight as well as the time variation of the fluxes due to solar activity.

Hams, Thomas; et al.

185

A high sensitivity momentum flux measuring instrument for plasma thruster exhausts and diffusive plasmas  

SciTech Connect

A high sensitivity momentum flux measuring instrument based on a compound pendulum has been developed for use with electric propulsion devices and radio frequency driven plasmas. A laser displacement system, which builds upon techniques used by the materials science community for surface stress measurements, is used to measure with high sensitivity the displacement of a target plate placed in a plasma thruster exhaust. The instrument has been installed inside a vacuum chamber and calibrated via two different methods and is able to measure forces in the range of 0.02-0.5 mN with a resolution of 15 {mu}N. Measurements have been made of the force produced from the cold gas flow and with a discharge ignited using argon propellant. The plasma is generated using a Helicon Double Layer Thruster prototype. The instrument target is placed about 1 mean free path for ion-neutral charge exchange collisions downstream of the thruster exit. At this position, the plasma consists of a low density ion beam (10%) and a much larger downstream component (90%). The results are in good agreement with those determined from the plasma parameters measured with diagnostic probes. Measurements at various flow rates show that variations in ion beam velocity and plasma density and the resulting momentum flux can be measured with this instrument. The instrument target is a simple, low cost device, and since the laser displacement system used is located outside the vacuum chamber, the measurement technique is free from radio frequency interference and thermal effects. It could be used to measure the thrust in the exhaust of other electric propulsion devices and the momentum flux of ion beams formed by expanding plasmas or fusion experiments.

West, Michael D.; Charles, Christine; Boswell, Rod W. [Space Plasma, Power and Propulsion Group, Research School of Physics and Engineering, Australian National University, Canberra ACT 0200 (Australia)

2009-05-15

186

A high sensitivity momentum flux measuring instrument for plasma thruster exhausts and diffusive plasmas  

NASA Astrophysics Data System (ADS)

A high sensitivity momentum flux measuring instrument based on a compound pendulum has been developed for use with electric propulsion devices and radio frequency driven plasmas. A laser displacement system, which builds upon techniques used by the materials science community for surface stress measurements, is used to measure with high sensitivity the displacement of a target plate placed in a plasma thruster exhaust. The instrument has been installed inside a vacuum chamber and calibrated via two different methods and is able to measure forces in the range of 0.02-0.5mN with a resolution of 15?N. Measurements have been made of the force produced from the cold gas flow and with a discharge ignited using argon propellant. The plasma is generated using a Helicon Double Layer Thruster prototype. The instrument target is placed about 1 mean free path for ion-neutral charge exchange collisions downstream of the thruster exit. At this position, the plasma consists of a low density ion beam (10%) and a much larger downstream component (90%). The results are in good agreement with those determined from the plasma parameters measured with diagnostic probes. Measurements at various flow rates show that variations in ion beam velocity and plasma density and the resulting momentum flux can be measured with this instrument. The instrument target is a simple, low cost device, and since the laser displacement system used is located outside the vacuum chamber, the measurement technique is free from radio frequency interference and thermal effects. It could be used to measure the thrust in the exhaust of other electric propulsion devices and the momentum flux of ion beams formed by expanding plasmas or fusion experiments.

West, Michael D.; Charles, Christine; Boswell, Rod W.

2009-05-01

187

A high sensitivity momentum flux measuring instrument for plasma thruster exhausts and diffusive plasmas.  

PubMed

A high sensitivity momentum flux measuring instrument based on a compound pendulum has been developed for use with electric propulsion devices and radio frequency driven plasmas. A laser displacement system, which builds upon techniques used by the materials science community for surface stress measurements, is used to measure with high sensitivity the displacement of a target plate placed in a plasma thruster exhaust. The instrument has been installed inside a vacuum chamber and calibrated via two different methods and is able to measure forces in the range of 0.02-0.5 mN with a resolution of 15 microN. Measurements have been made of the force produced from the cold gas flow and with a discharge ignited using argon propellant. The plasma is generated using a Helicon Double Layer Thruster prototype. The instrument target is placed about 1 mean free path for ion-neutral charge exchange collisions downstream of the thruster exit. At this position, the plasma consists of a low density ion beam (10%) and a much larger downstream component (90%). The results are in good agreement with those determined from the plasma parameters measured with diagnostic probes. Measurements at various flow rates show that variations in ion beam velocity and plasma density and the resulting momentum flux can be measured with this instrument. The instrument target is a simple, low cost device, and since the laser displacement system used is located outside the vacuum chamber, the measurement technique is free from radio frequency interference and thermal effects. It could be used to measure the thrust in the exhaust of other electric propulsion devices and the momentum flux of ion beams formed by expanding plasmas or fusion experiments. PMID:19485509

West, Michael D; Charles, Christine; Boswell, Rod W

2009-05-01

188

A comparison of methane flux rates from the margins of a permanent wetland and an ephemeral wetland in southern Minnesota  

NASA Astrophysics Data System (ADS)

The degree of expansion and contraction of wetlands is likely to change as climate change alters drought and precipitation events. As wetland size becomes more dynamic, the extent and duration of inundation of soils on their margins will change. The amount of methane released from wetlands will also change since methanogens thrive in anoxic, saturated soils. It is critical to study the factors that influence methane emissions from wetlands because methane is 20 times more effective at trapping heat in the atmosphere than carbon dioxide. The objective of our research was to compare methane flux rates from the margins of a permanent wetland and an ephemeral wetland. We also assessed the impact of Reed Canary Grass (Phalaris arundinacea) on transport of methane from the soil to the atmosphere. Methane flux emissions were measured using portable gas flux chambers at Bakko Pond (a permanent wetland) and East Coyote Pond (an ephemeral wetland) on the St. Olaf College Natural Lands in southern Minnesota. At each wetland, we measured methane emissions from plots of clipped and unclipped Reed Canary Grass. We found no statistical difference between clipped and unclipped plots, suggesting that a diffusive gas transport system rather than a coupling of a diffusive and convective gas transport emits methane. We also found that the average rate of methane flux was higher at East Coyote Pond at both the wet Reed Canary Grass and dry Reed Canary Grass sites, when compared to the dry Reed Canary Grass site at Bakko Pond. Higher methane emission rates at East Coyote Pond is consistent with the characteristics of a wetland with a shallow bank where marginal soil is frequently inundated with water, creating a favorable anoxic environment for active methanogens. In contrast, Bakko Pond has a steep embankment, reducing soil saturation. We also found that soil moisture was strongly correlated with methane flux rates between the sites and over time within a site. Overall, our results suggest that increases in the intensity of precipitation events due to climate change may lead to increased methane emissions from wetlands by increasing the extent of soil saturation. The total impact of these changes on annual methane flux will depend, however, on changes in the frequency of these events and the resulting changes in duration of soil saturation.

Nelson, L. C.; Kannenberg, S.; Ludwig, S.; Rich, H.; Spawn, S.; Porterfield, J.; Schade, J. D.

2012-12-01

189

Direct Measurement of CO2 Fluxes in Marine Whitings  

SciTech Connect

Clean, affordable energy is a requisite for the United States in the 21st Century Scientists continue to debate over whether increases in CO{sub 2} emissions to the atmosphere from anthropogenic sources, including electricity generation, transportation and building systems may be altering the Earth's climate. While global climate change continues to be debated, it is likely that significant cuts in net CO{sub 2} emissions will be mandated over the next 50-100 years. To this end, a number of viable means of CO{sub 2} sequestration need to be identified and implemented. One potential mechanism for CO{sub 2} sequestration is the use of naturally-occurring biological processes. Biosequestration of CO{sub 2} remains one of the most poorly understood processes, yet environmentally safe means for trapping and storing CO{sub 2}. Our investigation focused on the biogeochemical cycling of carbon in microbial precipitations of CaCO{sub 3}. Specifically, we investigated modern whitings (microbially-induced precipitates of the stable mineral calcium carbonate) as a potential, natural mechanism for CO{sub 2} abatement. This process is driven by photosynthetic metabolism of cyanobacteria and microalgae. We analyzed net air: sea CO{sub 2} fluxes, net calcification and photosynthetic rates in whitings. Both field and laboratory investigations have demonstrated that atmospheric CO{sub 2}decreases during the process of microbial calcification.

Lisa L. Robbins; Kimberly K. Yates

2001-07-05

190

A Summary of Mass Flux Measurements in Solid 4He  

NASA Astrophysics Data System (ADS)

Here we provide a summary and brief review of some of the work done with solid 4He at the University of Massachusetts Amherst below a sample pressure of 28 bar. The motivation for the work has been to attempt to pass 4He atoms through solid 4He without directly applying mechanical pressure to the solid itself. The specific technique chosen is limited to pressures near the melting curve and was initially designed to provide a yes/no answer to the question of whether or not it might be possible to observe such a mass flux. The thermo-mechanical effect and direct mass injection have been separately used to create chemical potential differences between two reservoirs of superfluid 4He connected to each other through superfluid-filled Vycor rods in series with solid 4He, which is in the hcp region of the phase diagram. The thermo-mechanical effect is a more versatile approach. And, in a particular symmetric application it is designed to provide a mass flux with little or no net increase in the density of the solid. Our observations, off but near the melting curve, have included: (1) the presence of an increasing DC flux of atoms through the solid-filled cell with decreasing temperature below ?650 mK and no flux above this temperature; (2) the presence of a flux minimum and flux instability in the vicinity of 75-80 mK, with a flux increase at lower temperatures; (3) the temperature dependence of the flux above 100 mK and the dependence of the flux on the net driving chemical potential difference provide interesting insights on the possible mechanism that leads to the flux above 100 mK. The most recent data suggest that whatever is responsible for the flux in solid 4He, at least for T>100 mK, may be an example of a Bosonic Luttinger liquid.

Hallock, R. B.; Ray, M. W.; Vekhov, Y.

2012-11-01

191

High Resolution Measurement of the Glycolytic Rate  

PubMed Central

The glycolytic rate is sensitive to physiological activity, hormones, stress, aging, and malignant transformation. Standard techniques to measure the glycolytic rate are based on radioactive isotopes, are not able to resolve single cells and have poor temporal resolution, limitations that hamper the study of energy metabolism in the brain and other organs. A new method is described in this article, which makes use of a recently developed FRET glucose nanosensor to measure the rate of glycolysis in single cells with high temporal resolution. Used in cultured astrocytes, the method showed for the first time that glycolysis can be activated within seconds by a combination of glutamate and K+, supporting a role for astrocytes in neurometabolic and neurovascular coupling in the brain. It was also possible to make a direct comparison of metabolism in neurons and astrocytes lying in close proximity, paving the way to a high-resolution characterization of brain energy metabolism. Single-cell glycolytic rates were also measured in fibroblasts, adipocytes, myoblasts, and tumor cells, showing higher rates for undifferentiated cells and significant metabolic heterogeneity within cell types. This method should facilitate the investigation of tissue metabolism at the single-cell level and is readily adaptable for high-throughput analysis. PMID:20890447

Bittner, Carla X.; Loaiza, Anitsi; Ruminot, Ivan; Larenas, Valeria; Sotelo-Hitschfeld, Tamara; Gutierrez, Robin; Cordova, Alex; Valdebenito, Rocio; Frommer, Wolf B.; Barros, L. Felipe

2010-01-01

192

High resolution measurement of the glycolytic rate.  

PubMed

The glycolytic rate is sensitive to physiological activity, hormones, stress, aging, and malignant transformation. Standard techniques to measure the glycolytic rate are based on radioactive isotopes, are not able to resolve single cells and have poor temporal resolution, limitations that hamper the study of energy metabolism in the brain and other organs. A new method is described in this article, which makes use of a recently developed FRET glucose nanosensor to measure the rate of glycolysis in single cells with high temporal resolution. Used in cultured astrocytes, the method showed for the first time that glycolysis can be activated within seconds by a combination of glutamate and K(+), supporting a role for astrocytes in neurometabolic and neurovascular coupling in the brain. It was also possible to make a direct comparison of metabolism in neurons and astrocytes lying in close proximity, paving the way to a high-resolution characterization of brain energy metabolism. Single-cell glycolytic rates were also measured in fibroblasts, adipocytes, myoblasts, and tumor cells, showing higher rates for undifferentiated cells and significant metabolic heterogeneity within cell types. This method should facilitate the investigation of tissue metabolism at the single-cell level and is readily adaptable for high-throughput analysis. PMID:20890447

Bittner, Carla X; Loaiza, Anitsi; Ruminot, Iván; Larenas, Valeria; Sotelo-Hitschfeld, Tamara; Gutiérrez, Robin; Córdova, Alex; Valdebenito, Rocío; Frommer, Wolf B; Barros, L Felipe

2010-01-01

193

A scintillating fission detector for neutron flux measurements  

SciTech Connect

Neutron flux monitors are commonly used for a variety of nuclear physics applications. A scintillating neutron detector, consisting of a liquid scintillator loaded with fissionable material, has been developed, characterized, and tested in the beam line at the Los Alamos Neutron Science Center, and shows a significant improvement in neutron sensitivity compared with a conventional fission chamber. Recent research on nanocomposite-based scintillators for gamma-ray detection indicates that this approach can be extended to load nanoparticles of fissionable material into a scintillating matrix, with up to three orders of magnitude higher loading than typical fission chambers. This will result in a rugged, cost-efficient detector with high efficiency, a short signal rise time, and the ability to be used in low neutron-flux environments. Initial efforts to utilize the luminescence of uranyl oxide to eliminate the need for wavelength-shifting dyes were unsuccessful. Excitation of uranyl compounds has been reported at wavelengths ranging from 266 nm to 532 nm. However, neither the 300 nm emission of toluene, nor the 350 nm emission of PPO, nor the 410 nm emission of POPOP resulted in significant excitation of and emission by uranyl oxide. As indicated by UV/visible spectroscopy, light emitted at these wavelengths was absorbed by the colored solution. {sup 235}U remains the most attractive candidate for a fissionable scintillator, due to its high fission cross-section and lack of a threshold fission energy, but all solutions containing molecular uranium compounds will be colored, most more highly than the U{sup 6+} compounds used here. Research is therefore continuing toward the fabrication of uranium nanoparticles, in which, due to Rayleigh scattering, the coloration should be less pronounced. The characterization of the thorium-loaded liquid scintillator and the fabrication of the 100 mL detectors for use at LANSCE demonstrated the feasibility of loading fissionable material into a liquid scintillator. Analysis of beam line experiments using the thorium-loaded scintillator is underway to determine the fission event rate in the detector, for comparison with a conventional fission chamber as well as with an unloaded liquid scintillator.

Stange, Sy [Los Alamos National Laboratory; Esch, Ernst I [Los Alamos National Laboratory; Burgett, Eric A [Los Alamos National Laboratory; May, Iain [Los Alamos National Laboratory; Muenchausen, Ross E [Los Alamos National Laboratory; Taw, Felicia [Los Alamos National Laboratory; Tovesson, Fredrik K [Los Alamos National Laboratory

2010-01-01

194

The effect of cumulus cloud field anisotropy on solar radiative fluxes and atmospheric heating rates  

NASA Astrophysics Data System (ADS)

The effect of fair-weather cumulus cloud field anisotropy on domain average surface fluxes and atmospheric heating profiles was studied. Causes of anisotropy were investigated using a large-eddy simulation (LES) model. Cloud formation under a variety of environmental conditions was simulated and the degree of anisotropy in the output fields was calculated. Wind shear was found to be the single greatest factor in the development of both vertically tilted and horizontally stretched cloud structures. A stochastic field generation algorithm was used to produce twenty three-dimensional liquid water content fields based on the statistical properties of the LES cloud scenes. Progressively greater degrees of tilt and stretching were imposed on each of these scenes, so that an ensemble of scenes were produced for each level of distortion. The resulting scenes were used as input to a three-dimensional Monte Carlo model. Domain-average transmission, reflection, and absorption of broadband solar radiation were computed for each scene along with the average heating rate profile. Both tilt and horizontal stretching were found to significantly affect calculated fluxes, with the amount and sign of flux differences depending strongly on sun position relative to cloud distortion geometry. For nearly all solar geometries, domain-averaged fluxes and atmospheric heating rate profiles calculated using the Independent Pixel Approximation differed substantially from the corresponding three-dimensional Monte Carlo results.

Hinkelman, Laura M.

195

Outer atmospheres of cool stars. II - Mg II flux profiles and chromospheric radiative loss rates  

NASA Technical Reports Server (NTRS)

International Ultraviolet Explorer high-resolution spectra of the Mg II lines at 2796, 2803 A in 15 stars of spectral type G2-M2 including a wide range of luminosities are presented. These spectra are calibrated in absolute flux units at earth and at the stellar surface, and the chromospheric radiative loss rates in the Mg II lines are compared with corresponding rates in the Ca II H, K, and 8542 lines. The ratio of Mg II surface flux to total surface flux is found to be independent of stellar luminosity and thus gravity; may decrease slowly with decreasing effective temperature, and increases with decreasing period among RS Canum Venaticorum binaries. The factor of 10 range in this ratio at each effective temperature may be due to differences in the fractional surface area covered by plages and may indicate that stars of all luminosity classes have chromospheric plages. In this small data sample no evidence is found that the Mg II line surface fluxes indicate whether a star possesses a transition region and hot corona.

Basri, G. S.; Linsky, J. L.

1979-01-01

196

Seawater methane flux, methane oxidation rates, and methane sources on the Central US Beaufort Sea Continental Shelf  

NASA Astrophysics Data System (ADS)

Previous studies have shown that some shallow-water circum-Arctic Ocean continental shelves (e.g., the Laptev Sea) are releasing substantial methane to the atmosphere. A number of processes -- including microbial degradation of organic matter in shallow sediments or in deeper sediments that were only recently thawed from permafrost, the dissociation of gas hydrates that formed in association with permafrost, and leakage from deeper thermogenic reservoirs -- may contribute to these methane fluxes. In August 2012, the USGS Gas Hydrates Project, with sponsorship from the DOE Methane Hydrates R&D Program, conducted a cross-shelf survey of greenhouse gas fluxes, carbon isotopic signatures of methane and CO2, and methane oxidation rates on the Central US Beaufort Sea continental shelf. IODP drilling has been proposed for a shelf-to-upper continental slope transect on this part of the Alaskan Beaufort passive margin to unravel the history of late Pleistocene to contemporary climate warming and sea level rise. The work presented here complements a 2012 USGS multichannel seismic program intended as IODP site survey. The flux, isotopic, and oxidation rate surveys sampled nearshore areas still underlain by subsea permafrost, a location where relict gas hydrate previously associated with permafrost may still exist and extend across the shelf to where present-day methane release is likely dominated by microbial methane generated in situ. The new geochemical data were acquired using dedicated cavity ringdown spectrometers (CRDS) for the atmospheric and sea surface measurements. The seawater CRDS also characterized the carbon isotopic signature of the CO2 and CH4 in real-time. Oxidation rate measurements were carried out using the low level 14C-CH4 (LL 14C) tracer method. Continuous measurements of surface air and surface seawater methane and carbon dioxide concentration, in conjunction with relevant meteorological and water chemistry data, permit us to calculate sea-to-air methane fluxes from nearshore shallow water to the shelf break. By surveying across the geophysically-defined permafrost-no-permafrost transition in both 2011 (Harrison Bay) and 2012, we have been able to evaluate the extent to which the thawing of subsea permafrost corresponds to changes in methane emission patterns. Vertical profiles of LL 14C tracer methane oxidation rates at distinct locations along the transect provide the modern constraints on the role of water column aerobic methanotrophs in mitigating methane emitted at the seafloor before it reaches the atmosphere. The combination of techniques employed here provide novel first order constraints on the sources of methane escaping sediments of the Central US Beaufort Shelf, the magnitude of greenhouse gases transmitted to the atmosphere and the role that methane oxidation plays in regulating these fluxes.

Pohlman, J.; Pack-Woo, M.; Xu, X.; Ruppel, C. D.; Casso, M.; Worley, C.

2012-12-01

197

Flow rate measurement in aggressive conductive fluids  

NASA Astrophysics Data System (ADS)

Two non-contact experimental methods of flow rate measurements for aggressive conductive liquids are described. The techniques are based on electromagnetic forces and Faraday's law: Lorentz force is induced inside moving conductive liquid under influence of variable magnetic field of permanent magnets. They are mounted along a liquid metal channel or (in case of the second method) inserted into rotated metal wheels. The force acts in the opposite of fluids' velocity direction and hence it is possible to measure reaction force of it that takes place according to Newton's law on magnetic field source - permanent magnets. And by knowing the force, which linearly depends on velocity, one can calculate mean flow rate of liquid. In addition experimental "dry" calibration and its results are described for one of the measurements' techniques.

Dubovikova, Nataliia; Kolesnikov, Yuri; Karcher, Christian

2014-03-01

198

Evapotranspiration fluxes over mixed vegetation areas measured from large aperture scintillometer  

Microsoft Academic Search

Routine measurement of spatially averaged surface fluxes of sensible heat (H) in river basins is now feasible. These fluxes, when combined with net radiation estimates, can be used to derive areally averaged actual evapotranspiration (ET). The scintillation method is shown to be promising method for estimating areally averaged sensible heat fluxes. The large aperture scintillometer (LAS) is an optical device

H. M. Hemakumara; Lalith Chandrapala; Arnold F. Moene

2003-01-01

199

Efficient Calculation of Infrared Fluxes and Cooling Rates Using the Two-Stream Equations  

Microsoft Academic Search

The calculation of infrared radiative fluxes and cooling rates using the two-stream equations is discussed. It is argued that at infrared wavelengths the two-stream equations are best viewed as an approximation to the differential radiance, the difference between the actual radiance and the local isotropic Planckian radiance. In this formulation the diffusivity factor and the forward- and backward-scattering fractions are

J. M. Edwards

1996-01-01

200

Airborne Flux Measurements of Volatile Organic Compounds and NOx over a European megacity  

NASA Astrophysics Data System (ADS)

Ground level ozone (O3) and nitrogen dioxide (NO2) are priority pollutants whose concentrations are closely regulated by European Union Air Quality Directive 2008/50/EC. O3 is a secondary pollutant, produced from a complex chemical interplay between oxides of nitrogen (NOx = NO + NO2) and volatile organic compounds (VOCs). Whilst the basic atmospheric chemistry leading to O3 formation is generally well understood, there are substantial uncertainties associated with the magnitude of emissions of both VOCs and NOx. At present our knowledge of O3 precursor emissions in the UK is primarily derived from National Atmospheric Emission inventories (NAEI) that provide spatially disaggregated estimates at 1x1km resolution, and these are not routinely tested at city or regional scales. Uncertainties in emissions propagate through into uncertainties in predictions of air quality in the future, and hence the likely effectiveness of control policies on both background and peak O3 and NO2 concentrations in the UK. The Ozone Precursor Fluxes in the Urban Environment (OPFUE) project aims to quantify emission rates for NOx and selected VOCs in and around the megacity of London using airborne eddy covariance (AEC). The mathematical foundation for AEC has been extensively reviewed and AEC measurements of ozone, dimethyl sulphide, CO2 and VOCs have been previously reported. During the summer of 2013, approximately 30 hours of airborne flux measurements of toluene, benzene, NO and NO2 were obtained from the NERC Airborne Research and Survey Facility's (ARSF) Dornier-228 aircraft. Over SE England, flights involved repeated south west to north east transects of ~50 km each over Greater London and it's surrounding suburbs and rural areas, flying at the aircraft's minimum operating flight altitude and airspeed (~300m, 80m/s). Mixing ratios of benzene and toluene were acquired at 2Hz using a proton transfer reaction mass spectrometer (PTR-MS) and compared to twice hourly whole air canister samples (WAS) which were quantitatively determined post-flight via TD-GCMS. Mixing ratios between the PTR-MS and WAS-TD-GCMS were in good agreement with R2 values of 0.8 and 1.0 for Toluene and Benzene respectively. Mixing ratios of NO and NO2 were acquired at 10Hz using a 2 channel NOx chemiluminescence detector with photolytic converter. These measurements were used with 20 Hz 3-D wind vector data from an AIMMS-20 turbulence probe on the aircraft to calculate highly spatially resolved (1 km) surface-to-atmosphere emission flux rates of these compounds using the eddy covariance method of Karl et al. (2013). Measured surface to atmosphere emission fluxes of NOx, benzene and toluene from London were between 40 - 91 mg m2 h-1, 0.1 - 0.4 mg m2 h-1 and 0.2 - 2 mg m2 h-1 respectively, showing the spatial flux heterogeneity over the city. This demonstrates for the first time the feasibility of airborne eddy covariance flux measurements of reactive NOx species. We also show the applicability of wavelet analysis using virtually disjunct eddy covariance measurements of anthropogenic compounds in estimating regional fluxes over a European megacity. We compare our measured emission rates with those estimated from 'bottom-up' emissions inventories and highlight the agreement between the two.

Shaw, Marvin; Lee, James; Davison, Brian; Misztal, Pawel; Karl, Thomas; Hewitt, Nick; Lewis, Alistair

2014-05-01

201

Carbon fluxes of surfaces vs. ecosystems: advantages of measuring eddy covariance and soil respiration simultaneously in dry grassland ecosystems  

NASA Astrophysics Data System (ADS)

An automated open system for measurement of soil CO2 efflux (Rsc) was developed and calibrated against known fluxes. The system was tested in the field, while estimating soil respiration simultaneously by the gradient method (Rsg) at a dry, sandy grassland site (Bugac, Hungary). Ecosystem respiration (Rego) was measured using the eddy covariance technique. The small chamber size (5 cm in diameter) made it possible to use the chambers in vegetation gaps, thereby avoiding the necessity of removing shoots and disturbing the spatial structure of vegetation and the upper soil layer. Low air flow rates associated with small chamber volume and chamber design allowed the overpressure range to stabilize between 0.05-0.12 Pa. The correlation between ecosystem and soil CO2 efflux rates as measured by the independent methods was significant, Reco rates were similar or even lower than Rsc in the low flux (up to 2 ?mol CO2 m-2 s-1) range but the differences were within the uncertainty limits for the two fluxes. Rsc from trenched and non-trenched plots amounted to 16 % and 44 % of Reco, respectively. The gradient method showed both up and downward CO2 fluxes originating from the main rooting zone after rains. Diffusive retardation played a smaller role than CO2 production considering the soil air CO2 concentration increase after rains in a given layer. Downward fluxes within the soil profile amounted to 15 % of the simultaneous upward fluxes and to ~7.6 % of the total (upward) effluxes during the 3-month study. The upper 5 cm soil layer contributed to ~50 % of the total soil CO2 efflux. Downward fluxes are expected to seriously affect (1) the Reco vs. temperature response functions and (2) the net ecosystem exchange of CO2 (NEE) vs. photon flux density response functions, therefore potentially affecting the gap filling procedures and to lead to a situation (3) when the measured surface and the real time ecosystem fluxes will necessarily differ in the short term. Simultaneous measurements of Reco and soil CO2 effluxes may reveal the timing and magnitude of the decoupling, thereby contributing to decreasing uncertainty associated with eddy flux measurements over flat terrains. While the correlations between CO2 effluxes measured by independent systems are strong, Rsg was generally larger than Rsc or Reco, mainly due to overestimation of effective diffusivity in the soil.

Nagy, Z.; Pintér, K.; Pavelka, M.; Darenová, E.; Balogh, J.

2011-09-01

202

Estimating terrestrial uranium and thorium by antineutrino flux measurements  

E-print Network

the dynamics, define the thermal history, and are a consequence of the differentiation of the Earth. Knowledge of the elec- tron antineutrino flux from 238 U and 232 Th decay and of radio- genic heat production within

Mcdonough, William F.

203

Mass Flux Measurements of Arsenic in Groundwater (Battelle Conference)  

EPA Science Inventory

Concentration trends of arsenic are typically used to evaluate the performance of remediation efforts designed to mitigate arsenic contamination in groundwater. A complementary approach would be to track changes in mass flux of the contaminant through the subsurface, for exampl...

204

The flux measure of influence in engineering networks  

E-print Network

The objective of this project is to characterize the influence of individual nodes in complex networks. The flux metric developed here achieves this goal by considering the difference between the weighted outdegree and ...

Schwing, Kyle Michael

2009-01-01

205

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

206

Decoupled cantilever arms for highly versatile and sensitive temperature and heat flux measurements  

E-print Network

Microfabricated cantilever beams have been used in microelectromechanical systems for a variety of sensor and actuator applications. Bimorph cantilevers accurately measure temperature change and heat flux with resolutions ...

Burg, Brian R.

207

A novel approach to measuring heat flux in swimming animals  

Microsoft Academic Search

We present a design for long-term or removable attachment of heat flux sensors (HFSs) to stationary or swimming animals in water that enables collection of heat flux data on both captive and free-ranging pinnipeds. HFSs were modified to allow for independent, continuous, and long-term or removable attachment to study animals. The design was tested for effects of HFSs and the

Kate Willis; Markus Horning

2005-01-01

208

The measurable heat flux that accompanies active transport Dick Bedeauxw and Signe Kjelstrupw  

E-print Network

The measurable heat flux that accompanies active transport by Ca2+ -ATPase Dick Bedeauxw and Signe how the measurable heat flux and the heat production under isothermal conditions, as well of measurements, that the heat production in active trans- port is significant and varies. These authors studied

Kjelstrup, Signe

209

High repetition rate alexandrite laser divergence measurements  

NASA Astrophysics Data System (ADS)

Beam divergence measurements were performed on a high repetition rate alexandrite laser currently being developed for a Los Alamos National Laboratory photochemistry research program, and were found to be spherically correctable and approximately constant at 8 times diffraction limited over a large input power range. A 0.5 x 10 cm alexandrite rod was pumped in a double ellipse head at a constant 42 joules/pulse input energy at repetition rates of 75 to 200 Hz. Several resonators were employed over the input power range to compensate for the thermal lensing, which varied from 0.63 to 0.12 m. The divergence measurements were performed by splitting a fraction of the output beam, passing it through a long focal length lens, and measuring the transmission percentage through calibrated apertures at the focal plane. This measurement was performed for seven resonators and cross-checked by imaging the far field pattern through a TV camera system and observing the spot sizes. With a similar experimental setup, a Glan prism was placed extra-cavity to examine the magnitude of depolarization losses due to stress induced birefringence under pumped conditions. No measurable effect was found up to 1 kW input power.

Birrell, S. E.; Rapoport, W. R.; Budgor, A. B.

210

PHOTON FLUX DETERMINATION FOR A PRECISION MEASUREMENT OF THE NEUTRAL PION LIFETIME  

SciTech Connect

The Jefferson Lab Hall B PrimEx Collaboration is using tagged photons to perform a 1.4% level measurement of the absolute cross section for the photo-production of neutral pions in the Coulomb field of a nucleus as a test of Chiral Perturbation Theory. Such a high precision pushes the limits of the photon tagging technique in regards to the determination of the absolute photon flux. A multifaceted approach to this problem has included measuring the absolute tagging ratios with a Total Absorption Counter (TAC) as well as relative tagging ratios with a Pair Spectrometer (PS), and determining the rate of the tagging counters using multi-hit TDCâ s and a clock trigger. This enables the determination of the absolute tagged photon flux for the PrimEx experiment with uncertainty of ? 1.0%, which is unprecedented. In view of the stringent constraints on the required precision of the photon flux for this experiment, periodicmeasurements of the pair production cross section were perform

Teymurazyan, Aram

2007-12-01

211

Influence of thermal and resonance neutron on fast neutron flux measurement by Pu-239 fission chamber  

E-print Network

The Pu-239 fission chambers are widely used to measure fission spectrum neutron flux due to a flat response to fast neutrons. However, in the mean time the resonance and thermal neutrons can cause a significant influence on the measurement if they are moderated, which could be eliminated by using B and Cd covers. At a column enriched uranium fast neutron critical assembly, the fission reaction rates of Pu-239 are measured as 1.791*10-16,2.350*10-16 and 1.385*10-15 per second for 15mm thick B cover, 0.5mm thick Cd cover, and no cover respectively. While the fission reaction rate of Pu-239 is rapidly increased to 2.569*10-14 for a 20mm thick polythene covering fission chamber. The average Pu-239 fission cross-section of thermal and resonance neutrons is calculated to be 500b and 24.95b with the assumption of 1/v and 1/E spectra respectively, then thermal, resonance and fast neutron flux are achieved to be 2.30*106,2.24*106 and 1.04*108cm-2s-1.

Lina zeng; Qiang Wang; Lingli Song; Chun Zheng

2014-03-19

212

MEASURING TINY MASS ACCRETION RATES ONTO YOUNG BROWN DWARFS  

SciTech Connect

We present low-resolution Keck I/LRIS spectra spanning from 3200 to 9000 A of nine young brown dwarfs and three low-mass stars in the TW Hya Association and in Upper Sco. The optical spectral types of the brown dwarfs range from M5.5 to M8.75, though two have near-IR spectral types of early L dwarfs. We report new accretion rates derived from excess Balmer continuum emission for the low-mass stars TW Hya and Hen 3-600A and the brown dwarfs 2MASS J12073347-3932540, UScoCTIO 128, SSSPM J1102-3431, USco J160606.29-233513.3, DENIS-P J160603.9-205644, and Oph J162225-240515B, and upper limits on accretion for the low-mass star Hen 3-600B and the brown dwarfs UScoCTIO 112, Oph J162225-240515A, and USco J160723.82-221102.0. For the six brown dwarfs in our sample that are faintest at short wavelengths, the accretion luminosity or upper limit is measurable only when the image is binned over large wavelength intervals. This method extends our sensitivity to accretion rate down to {approx}10{sup -13} M{sub sun}yr{sup -1} for brown dwarfs. Since the ability to measure an accretion rate from excess Balmer continuum emission depends on the contrast between excess continuum emission and the underlying photosphere, for objects with earlier spectral types the upper limit on accretion rate is much higher. Absolute uncertainties in our accretion rate measurements of {approx}3-5 include uncertainty in accretion models, brown dwarf masses, and distance. The accretion rate of 2 x 10{sup -12} M {sub sun} yr{sup -1} onto 2MASS J12073347-3932540 is within 15% of two previous measurements, despite large changes in the H{alpha} flux.

Herczeg, Gregory J.; Cruz, Kelle L.; Hillenbrand, Lynne A., E-mail: gregoryh@mpe.mpg.de

2009-05-10

213

Measuring radiative capture rates at DRAGON  

NASA Astrophysics Data System (ADS)

The DRAGON recoil separator facility is located at the ISAC facility at TRIUMF, Vancouver. It is designed to measure radiative alpha and proton capture reactions of astrophysical importance in inverse kinematics. The Supernanogan ion source at ISAC provides stable beams of high intensities. The DRAGON collaboration has taken advantage of this over the last years by measuring several reactions requiring high-intensity stable oxygen beams. In particular,the ^17O(p,?) and ^16O(?,?) reaction rates were recently measured. The former reaction is part of the hot CNO cycle, and strongly influences the abundance of ^18F in classical novae. Because of its relatively long lifetime, ^18F is a possible target for satellite-based gamma-ray spectroscopy. The ^16O(?,?) reaction plays a role in steady-state helium burning in massive stars, where it follows the ^12C(?,?) reaction. At astrophysically relevant energies, the reaction proceeds exclusively via direct capture, resulting in a low rate. In both cases, the unique capabilities of DRAGON enabled determination not only of the total reaction rates, but also of decay branching ratios. Results from both experiments will be presented.

Hager, U.; Davids, B.; Fallis, J.; Greife, U.; Hutcheon, D. A.; Rojas, A.; Ruiz, C.

2013-04-01

214

[Volatile organic compounds (VOCs) emitted from wood furniture--estimation of emission rate by passive flux sampler].  

PubMed

The aim of this study was to evaluate aldehydes and other volatile organic compounds (VOCs) emission from furniture, which may cause hazardous influence on human being such as sick building/sick house syndrome. In this study, VOCs emitted from six kinds of wood furniture, including three set of dining tables and three beds, were analyzed by large chamber test method (JIS A 1911). Based on the emission rates of total VOCs (TVOC), the impacts on the indoor TVOC was estimated by the simulation model with volume of 20 m3 and ventilation frequency of 0.5 times/h. The estimated increment of formaldehyde were exceeded the guideline value (100 microg/m3) in one set of dining table and one bed. The estimated TVOC increment values were exceeded the provisional target value for indoor air (400 microg/m3) in two sets of dining tables and two beds. These results revealed that VOC emissions from wood furniture may influence significantly indoor air quality. Also, in this study, to establish the alternative method for large chamber test methods, emission rates from representative five areas of furniture unit were evaluated by passive sampling method using flux sampler and emission rate from full-sized furniture was predicted. Emission rates predicted by flux passive sampler were 10-106% (formaldehyde) and 8-141% (TVOC) of the data measured using large chamber test, respectively. PMID:22259847

Jinno, Hideto; Tanaka-Kagawa, Toshiko; Furuta, Mitsuko; Shibatsuji, Masayoshi; Nishimura, Tetsuji

2011-01-01

215

Compact Instruments Measure Helium-Leak Rates  

NASA Technical Reports Server (NTRS)

Compact, lightweight instruments have been developed for measuring small flows of helium and/or detecting helium leaks in solenoid valves when the valves are nominally closed. These instruments do not impede the flows when the valves are nominally open. They can be integrated into newly fabricated valves or retrofitted to previously fabricated valves. Each instrument includes an upstream and a downstream thermistor separated by a heater, plus associated analog and digital heater-control, signal- conditioning, and data-processing circuits. The thermistors and heater are off-the-shelf surface mount components mounted on a circuit board in the flow path. The operation of the instrument is based on a well-established thermal mass-flow-measurement technique: Convection by the flow that one seeks to measure gives rise to transfer of heat from the heater to the downstream thermistor. The temperature difference measured by the thermistors is directly related to the rate of flow. The calibration curve from temperature gradient to helium flow is closely approximated via fifth-order polynomial. A microprocessor that is part of the electronic circuitry implements the calibration curve to compute the flow rate from the thermistor readings.

Stout, Stephen; Immer, Christopher

2003-01-01

216

Estimating Total Heliospheric Magnetic Flux from Single-Point in Situ Measurements  

NASA Technical Reports Server (NTRS)

A fraction of the total photospheric magnetic flux opens to the heliosphere to form the interplanetary magnetic field carried by the solar wind. While this open flux is critical to our understanding of the generation and evolution of the solar magnetic field, direct measurements are generally limited to single-point measurements taken in situ by heliospheric spacecraft. An observed latitude invariance in the radial component of the magnetic field suggests that extrapolation from such single-point measurements to total heliospheric magnetic flux is possible. In this study we test this assumption using estimates of total heliospheric flux from well-separated heliospheric spacecraft and conclude that single-point measurements are indeed adequate proxies for the total heliospheric magnetic flux, though care must be taken when comparing flux estimates from data collected at different heliocentric distances.

Owens, M. J.; Arge, C. N.; Crooker, N. U.; Schwardron, N. A.; Horbury, T. S.

2008-01-01

217

Comparison of measured and modeled radiation, heat and water vapor fluxes: FIFE pilot study  

NASA Technical Reports Server (NTRS)

The feasibility of using radio frequency receivers to collect data from automated weather stations to model fluxes of latent heat, sensible heat, and radiation using routine weather data collected by automated weather stations was tested and the estimated fluxes were compared with fluxes measured over wheat. The model Cupid was used to model the fluxes. Two or more automated weather stations, interrogated by radio frequency and other means, were utilized to examine some of the climatic variability of the First ISLSCP (International Satellite Land-Surface Climatology Project) Field Experiment (FIFE) site, to measure and model reflected and emitted radiation streams from various locations at the site and to compare modeled latent and sensible heat fluxes with measured values. Some bidirectional reflected and emitted radiation data were collected from 23 locations throughout the FIFE site. Analysis of these data along with analysis of the measured sensible and latent heat fluxes is just beginning.

Blad, Blaine L.; Hubbard, Kenneth G.; Verma, Shashi B.; Starks, Patrick; Norman, John M.; Walter-Shea, Elizabeth

1987-01-01

218

Airborne eddy correlation gas flux measurements - Design criteria for optical techniques  

NASA Technical Reports Server (NTRS)

Although several methods exist for the determination of the flux of an atmospheric species, the airborne eddy correlation method has the advantage of providing direct flux measurements that are representative of regional spatial domains. The design criteria pertinent to the construction of chemical instrumentation suitable for use in airborne eddy correlation flux measurements are discussed. A brief overview of the advantages and limitations of the current instrumentation used to obtain flux measurements for CO, CH4, O3, CO2, and water vapor are given. The intended height of the measurement within the convective boundary layer is also shown to be an important design criteria. The sensitivity, or resolution, which is required in the measurement of a scalar species to obtain an adequate species flux measurement is discussed. The relationship between the species flux resolution and the more commonly stated instrumental resolution is developed and it is shown that the standard error of the flux estimate is a complicated function of the atmospheric variability and the averaging time that is used. The use of the recently proposed intermittent sampling method to determine the species flux is examined. The application of this technique may provide an opportunity to expand the suite of trace gases for which direct flux measurements are possible.

Ritter, John A.; Sachse, Glen W.; Anderson, Bruce E.

1993-01-01

219

New technique of the local heat flux measurement in combustion chambers of steam boilers  

NASA Astrophysics Data System (ADS)

A new method for measurement of local heat flux to water-walls of steam boilers was developed. A flux meter tube was made from an eccentric tube of short length to which two longitudinal fins were attached. These two fins prevent the boiler setting from heating by a thermal radiation from the combustion chamber. The fins are not welded to the adjacent water-wall tubes, so that the temperature distribution in the heat flux meter is not influenced by neighbouring water-wall tubes. The thickness of the heat flux tube wall is larger on the fireside to obtain a greater distance between the thermocouples located inside the wall which increases the accuracy of heat flux determination. Based on the temperature measurements at selected points inside the heat flux meter, the heat flux absorbed by the water-wall, heat transfer coefficient on the inner tube surface and temperature of the water-steam mixture was determined.

Taler, Jan; Taler, Dawid; Sobota, Tomasz; Dzierwa, Piotr

2011-12-01

220

Turbulent heat flux to the ice shelf base: Microstructure measurements in the oceanic boundary layer  

NASA Astrophysics Data System (ADS)

Basal melting of Antarctic ice shelves plays an important role in ice sheet dynamics, as ice shelf loss allows the flow of inland glaciers to accelerate. Observed ice shelf thinning leads to suggestions of an increasing basal melt rate, yet given the inaccessibility of the ice shelf-ocean interface, the melt rate, vertical heat flux and processes that drive them are rarely quantified directly. Microstructure shear and conductivity observations from a tethered profiler were made beneath Larsen C Ice Shelf in December 2011 and repeated along with microstructure temperature beneath George VI Ice Shelf in January 2012. Such measurements at the ice-ocean interface within the cavity of an ice shelf are unprecedented. CTD and 3D current velocity measurements were also made at both sites, and radar measurements showed that the ice base was melting. Mean potential temperature in the upper ocean beneath Larsen C Ice Shelf was 77m° C above the in situ freezing point. Eddy diffusivities immediately beneath the ice base of up to 10-4 m2s-1 were calculated from shear derived dissipation rates of turbulent kinetic energy between 10-9 and 10-7 Wkg-1. Associated mean heat flux of 0.7 Wm-2 leads to an underestimation of the observed melt rate by at least an order of magnitude. Sharp interfaces dividing mixed layers of O(4m) thickness were detected in both CTD and microstructure measurements within a thermohaline staircase beneath George VI Ice Shelf. Temperature differences of ~0.05° C occurred across the steps and temperature at the ice base was 2° C warmer than in situ freezing point. Stability calculations confirmed that this was a primarily double diffusive environment. Turbulent mixing was strong in some layers and weak in others, with shear and thermal variance-derived dissipation rates of turbulent kinetic energy varying between 10-10 (close to the shear probe noise limit) and 10-7 Wkg-1. Vertical diffusion of heat is thought to provide the primary contribution to vertical heat flux where turbulent mixing is weak. We use the first direct microstructure profiles taken through hot water-drilled access boreholes in these two different environments to gain insight into the processes involved in the transport of heat from the upper ocean to the ice shelf base.

Venables, Emily; Nicholls, Keith; Makinson, Keith

2013-04-01

221

Quantitative method for measuring heat flux emitted from a cryogenic object  

Microsoft Academic Search

The present invention is a quantitative method for measuring the total heat flux, and of deriving the total power dissipation, of a heat-fluxing object which includes the steps of placing an electrical noise-emitting heat-fluxing object in a liquid helium bath and measuring the superfluid transition temperature of the bath. The temperature of the liquid helium bath is thereafter reduced until

Robert V

1993-01-01

222

Measurements of NO(x) and NO(y) concentrations and fluxes over Arctic tundra  

NASA Technical Reports Server (NTRS)

Measurements of the atmospheric concentrations of NO, NO2, total NO(y), and O3 were made during the NASA Arctic Boundary Layer Expedition (ABLE 3A) at a remote location in a tundra bog ecosystem in southeastern Alaska during the growing season (July-August 1988). Concentrations of NO(x) and NO(y) were found to be very low compared to other remote continental sites, indicating that anthropogenic influences were small at this site during this time of year. The NO(y) emission rate from the soil were 0.13 +/- 0.05 x 10 exp 9 molecules/sq cm/s. Direct measurements of the flux of total NO(y) were made for the first time, indicating downward flux of NO(y) at all times of day, with maximum deposition of 2.5 +/- 0.9 x 10 exp 9 molecules/sq cm/s in the afternoon. Deposition of HNO3 appears to dominate the atmosphere/surface exchange of NO(y). The mean dry deposition rate of NO(y) to the tundra was 1.8 +/- 1.0 x 10 exp 9 molecules/sq cm/s.

Bakwin, Peter S.; Wofsy, Steven C.; Fan, Song-Miao; Fitzjarrald, David R.

1992-01-01

223

Measurements of NO(x) and NO(y) concentrations and fluxes over Arctic tundra  

SciTech Connect

Measurements of the atmospheric concentrations of NO, NO[sub 2], total NO(y), and O[sub 3] were made during the NASA Arctic Boundary Layer Expedition (ABLE 3A) at a remote location in a tundra bog ecosystem in southeastern Alaska during the growing season (July-August 1988). Concentrations of NO(x) and NO(y) were found to be very low compared to other remote continental sites, indicating that anthropogenic influences were small at this site during this time of year. The NO(y) emission rate from the soil were 0.13 +/- 0.05 x 10 exp 9 molecules/sq cm/s. Direct measurements of the flux of total NO(y) were made for the first time, indicating downward flux of NO(y) at all times of day, with maximum deposition of 2.5 +/- 0.9 x 10 exp 9 molecules/sq cm/s in the afternoon. Deposition of HNO3 appears to dominate the atmosphere/surface exchange of NO(y). The mean dry deposition rate of NO(y) to the tundra was 1.8 +/- 1.0 x 10 exp 9 molecules/sq cm/s. 58 refs.

Bakwin, P.S.; Wofsy, S.C.; Fan, Songmiao; Fitzjarrald, D.R. (Harvard Univ., Cambridge, MA (United States) New York State Univ., Albany (United States))

1992-10-01

224

Solids flow rate measurement in dense slurries  

SciTech Connect

Accurate and rapid flow rate measurement of solids in dense slurries remains an unsolved technical problem, with important industrial applications in chemical processing plants and long-distance solids conveyance. In a hostile two-phase medium, such a measurement calls for two independent parameter determinations, both by non-intrusive means. Typically, dense slurries tend to flow in laminar, non-Newtonian mode, eliminating most conventional means that usually rely on calibration (which becomes more difficult and costly for high pressure and temperature media). These issues are reviewed, and specific solutions are recommended in this report. Detailed calculations that lead to improved measuring device designs are presented for both bulk density and average velocity measurements. Cross-correlation, chosen here for the latter task, has long been too inaccurate for practical applications. The cause and the cure of this deficiency are discussed using theory-supported modeling. Fluid Mechanics are used to develop the velocity profiles of laminar non-Newtonian flow in a rectangular duct. This geometry uniquely allows the design of highly accurate `capacitive` devices and also lends itself to gamma transmission densitometry on an absolute basis. An absolute readout, though of less accuracy, is also available from a capacitive densitometer and a pair of capacitive sensors yields signals suitable for cross-correlation velocity measurement.

Porges, K.G.; Doss, E.D.

1993-09-01

225

Heat flux measurement from vertical temperature profile and thermal infrared imagery in low-flux fumarolic zones  

NASA Astrophysics Data System (ADS)

Hydrothermal systems are associated to most of the dormant volcanoes. Heat is transported by steam from the hot magma body in the connected porosity and the fissures of the rock to the surface. If the flux is low enough (<500 W/m²), the steam mainly condensates in the soil close to surface, and a significant proportion of the heat is transported to the surface by conduction, producing a gradient of temperature and a thermal anomaly detectable at the surface. Detecting and monitoring these fluxes is crucial for hazard management, since it reflects the state of the magma body in depth. In order to quantify this flux two methods are considered. First, a vertical profile of temperature is measured by a series of thermocouples, and the conducted flux is estimated thanks to the Fourier law. Secondly, a more recent method uses the thermal infrared imagery to monitor the surface temperature anomaly (STA) between the studied zone and an equivalent zone not affected by the geothermal flux. The heat flux from the soil to the atmosphere is computed as the sum of (1) the radiative flux, (2) the sensible flux and (3) the residual steam flux. These two methods are complementary and have an equivalent uncertainty of approximately 20%, which would allow to track the major changes in the hydrothermal system. However, the surface and sub-surface temperatures are strongly influenced by the climate. For instance, it has been widely demonstrated that the surface temperature dramatically decreases after a rainfall. In order to estimate the reliability of the measurements, a numerical model simulating the evolution of the subsurface temperature in low flux fumarolic zone has been built. In depth, the heat can be transported either by conduction, or by the rising steam, or by condensed water. In surface, both the radiative flux and the sensible flux (convection of the atmosphere) are taken into account. This model allows to estimate the changes of temperature due to a variation of solar illumination, wind, or rainfalls. It has been successfully tested during 5 months with a permanent station built on the Ty fault on La Soufrière volcano (Guadeloupe, Lesser Antilles). Results show that the diurnal cycle has a significant influence on the temperature up to ca. 30 cm depth, hindering the use of the thermal gradient in this zone, while the STA has a negligible variation. Rain has a more dramatic influence: the surface temperature and the STA are significantly affected, even for small rains. The model shows that the drop of temperature and the affected thickness are mainly controlled by the amount of rain, while the relaxation time is primarily a function of the heat flux. These results have strong implications in the interpretation and the reliability of the temperature surveys, and could be used to correct them from the climate fluctuations.

Gaudin, Damien; Finizola, Anthony; Beauducel, François; Brothelande, Elodie; Allemand, Pascal; Delacourt, Christophe; Delcher, Eric; Peltier, Aline

2014-05-01

226

Galileo Probe Measurements of Thermal and Solar Radiation Fluxes in the Jovian Atmosphere  

NASA Technical Reports Server (NTRS)

The Galileo probe net flux radiometer (NFR) measured radiation fluxes in Jupiter's atmosphere from about 0.44 to 14 bars, using five spectral channels to separate solar and thermal components. Onboard calibration results confirm that the NFR responded to radiation approximately as expected. NFR channels also responded to a superimposed thermal perturbation, which can be approximately removed using blind channel measurements and physical constraints. Evidence for the expected NH3 cloud was seen in the spectral character of spin-induced modulations of the direct solar beam signals. These results are consistent with an overlying cloud of small NH3 ice particles (0.5-0.75 microns in radius) of optical depth 1.5-2 at 0.5 microns. Such a cloud would have so little effect on thermal fluxes that NFR thermal channels provide no additional constraints on its properties. However, evidence for heating near 0.45 bar in the NFR thermal channels would seem to require either an additional opacity source beyond this small-particle cloud, implying a heterogeneous-cloud structure to avoid conflicts with solar modulation results, or a change in temperature lapse rate just above the probe measurements. The large thermal flux levels imply water vapor mixing ratios that are only 6% of solar at 10 bars, but possibly increasing with depth, and significantly subsaturated ammonia at pressures less than 3 bars. If deep NH3 mixing ratios at the probe entry site are 3-4 times ground-based inferences, as suggested by probe radio signal attenuation, then only half as much water is needed to match NFR observations. No evidence of a water cloud was seen near the 5-bar level. The 5 microns thermal channel detected the presumed NH4SH cloud base near 1.35 bars. Effects of this cloud were also seen in the solar channel upflux measurements but not in the solar net fluxes, implying that the cloud is a conservative scatterer of sunlight. The minor thermal signature of this cloud is compatible with particle radii near 3 microns, but it cannot rule out smaller particles. Deeper than about 3 bars, solar channels indicate unexpectedly large absorption of sunlight at wavelengths longer than 0.6 microns, which might be due to unaccounted-for absorption by NH3 between 0.65 and 1.5 microns.

Sromovsky, L. A.; Collard, A. D.; Fry, P. M.; Orton, G. S.; Lemmon, M. T.; Tomasko, M. G.; Freedman, R. S.

1998-01-01

227

Galileo Probe Measurements of Thermal and Solar Radiation Fluxes in the Jovian Atmosphere  

NASA Technical Reports Server (NTRS)

The Galileo probe net flux radiometer (NFR) measured radiation fluxes in Jupiter's atmosphere from about 0.44 to 14 bars, using five spectral channels to separate solar and thermal components. Onboard calibration results confirm that the NFR responded to radiation approximately as expected. NFR channels also responded to a superimposed thermal perturbation, which can be approximately removed using blind channel measurements and physical constraints. Evidence for the expected NH3 cloud was seen in the spectral character of spin-induced modulations of the direct solar beam signals. These results are consistent with an overlying cloud of small NH3 ice particles (0.5-0.75 microns in radius) of optical depth 1.5-2 at 0.5 microns. Such a cloud would have so little effect on thermal fluxes that NFR thermal channels provide no additional constraints on its properties. However, evidence for heating near 0.45 bar in the NFR thermal channels would seem to require either an additional opacity source beyond this small-particle cloud, implying a heterogeneous cloud structure to avoid conflicts with solar modulation results, or a change in temperature lapse rate just above the probe measurements. The large thermal flux levels imply water vapor mixing ratios that are only 6% of solar at 10 bars, but possibly increasing with depth, and significantly subsaturated ammonia at pressures less than 3 bars. If deep NH3 mixing ratios at the probe entry site are 3-4 times ground-based inferences, as suggested by probe radio signal attenuation, then only half as much water is needed to match NFR observations. No evidence of a water cloud was seen near the 5-bar level. The 5-microns thermal channel detected the presumed NH4SH cloud base near 1.35 bars. Effects of this cloud were also seen in the solar channel upflux measurements but not in the solar net fluxes, implying that the cloud is a conservative scatterer of sunlight. The minor thermal signature of this cloud is compatible with particle radii near 3 gm, but it cannot rule out smaller particles. Deeper than about 3 bars, solar channels indicate unexpectedly large absorption of sunlight at wavelengths longer than 0.6 microns, which might be due to unaccounted-for absorption by NH3 between 0.65 and 1.5 microns.

Sromovsky, L. A.; Collard, A. D.; Fry, P. M.; Orton, G. S.; Lemmon, M. T.; Tomasko, M. G.; Freedman, R. S.

1998-01-01

228

LEAF, BRANCH, STAND & LANDSCAPE SCALE MEASUREMENTS OF VOLATILE ORGANIC COMPOUND FLUXES FROM U.S. WOODLANDS  

EPA Science Inventory

Natural volatile organic compounds (VOC) fluxes were measured in three U.S. woodlands in summer 1993. Fluxes from individual leaves and branches were estimated with enclosure techniques and used to initialize and evaluate VOC emission model estimates. Ambient measurements were us...

229

A method of measuring heat fluxes across nickel surfaces using the metal oxide on the surface  

Microsoft Academic Search

The feasibility of using the semiconducting oxide film on a metal surface to measure the heat flux through that surface and to measure the temperature of the surface has been demonstrated for nickel. The output compares favourably with other available heat flux meters.

P L Weickhardt; I M Ritchie; R J Batterham; D G Wood

1969-01-01

230

Measurements and heat-flux transport modelling in a heated cylinder wake  

Microsoft Academic Search

Hot-wire measurements of velocity and temperature fluctuations have been made in the self-preserving turbulent wake region of a heated cylinder. Second order statistics including Reynolds fluxes, ui?, are determined along with relevant triple correlations appearing in the Reynolds stress and Reynolds flux transport equations. The primary aim with these measurements is to study different modelling levels for passive scalar quantities.

Petra M. Wikström; Magnus Hallbäck; Arne V. Johansson

1998-01-01

231

Galileo probe measurements of thermal and solar radiation fluxes in the Jovian atmosphere  

Microsoft Academic Search

The Galileo probe net flux radiometer (NFR) measured radiation fluxes in Jupiter's atmosphere from about 0.44 to 14 bars, using five spectral channels to separate solar and thermal components. Onboard calibration results confirm that the NFR responded to radiation approximately as expected. NFR channels also responded to a superimposed thermal perturbation, which can be approximately removed using blind channel measurements

L. A. Sromovsky; A. D. Collard; P. M. Fry; G. S. Orton; M. T. Lemmon; M. G. Tomasko; R. S. Freedman

1998-01-01

232

MERCURY FLUX MEASUREMENTS OVER AIR AND WATER IN KEJIMKUJIK NATIONAL PARK, NOVA SCOTIA  

E-print Network

MERCURY FLUX MEASUREMENTS OVER AIR AND WATER IN KEJIMKUJIK NATIONAL PARK, NOVA SCOTIA F. S. BOUDALA. Mercury flux measurements were conducted at two lakes and three soil sites in Kejimkujik National Park, located in the eastern Canadian province of Nova Scotia. One of the lakes had high levels of both mercury

Folkins, Ian

233

Ir Thermographic Measurements of Temperatures and Heat Fluxes in Hypersonic Plasma Flow  

Microsoft Academic Search

The technological development achieved in instruments and methodology concerning both flights and ground hypersonic experiment (employed in space plane planning) goes towards an updating and a standardization of the heat flux technical measurements. In fact, the possibility to simulate high enthalpy flow relative to reentry condition by hypersonic arc-jet facility needs devoted methods to measure heat fluxes. Aim of this

G. Cardone; G. Tortora; A. del Vecchio

2005-01-01

234

Measurement of the cosmic ray and neutrino-induced muon flux at the Sudbury neutrino observatory  

Microsoft Academic Search

Results are reported on the measurement of the atmospheric neutrino-induced muon flux at a depth of 2 kilometers below the Earth's surface from 1229 days of operation of the Sudbury Neutrino Observatory (SNO). By measuring the flux of through-going muons as a function of zenith angle, the SNO experiment can distinguish between the oscillated and unoscillated portion of the neutrino

B. Aharmim; S. N. Ahmed; T. C. Andersen; A. E. Anthony; N. Barros; E. W. Beier; A. Bellerive; B. Beltran; M. Bergevin; S. D. Biller; K. Boudjemline; M. G. Boulay; T. H. Burritt; B. Cai; Y. D. Chan; M. Chen; M. C. Chon; B. T. Cleveland; G. A. Cox-Mobrand; C. A. Currat; X. Dai; F. Dalnoki-Veress; H. Deng; J. Detwiler; P. J. Doe; R. S. Dosanjh; G. Doucas; P.-L. Drouin; F. A. Duncan; M. Dunford; S. R. Elliott; H. C. Evans; G. T. Ewan; J. Farine; H. Fergani; F. Fleurot; R. J. Ford; J. A. Formaggio; N. Gagnon; J. T. M. Goon; K. Graham; D. R. Grant; E. Guillian; S. Habib; R. L. Hahn; A. L. Hallin; E. D. Hallman; C. K. Hargrove; P. J. Harvey; R. Hazama; K. M. Heeger; W. J. Heintzelman; J. Heise; R. L. Helmer; R. J. Hemingway; R. Henning; A. Hime; C. Howard; M. A. Howe; M. Huang; B. Jamieson; N. A. Jelley; J. R. Klein; M. Kos; A. Krüger; C. Kraus; C. B. Krauss; T. Kutter; C. C. M. Kyba; R. Lange; J. Law; I. T. Lawson; K. T. Lesko; J. R. Leslie; I. Levine; J. C. Loach; S. Luoma; R. MacLellan; S. Majerus; H. B. Mak; J. Maneira; A. D. Marino; R. Martin; N. McCauley; A. B. McDonald; S. McGee; C. Mifflin; M. L. Miller; B. Monreal; J. Monroe; A. J. Noble; N. S. Oblath; C. E. Okada; H. M. O'Keeffe; Y. Opachich; G. D. Orebi Gann; S. M. Oser; R. A. Ott; S. J. M. Peeters; A. W. P. Poon; G. Prior; K. Rielage; B. C. Robertson; R. G. H. Robertson; E. Rollin; M. H. Schwendener; J. A. Secrest; S. R. Seibert; O. Simard; J. J. Simpson; D. Sinclair; P. Skensved; M. W. E. Smith; T. J. Sonley; T. D. Steiger; L. C. Stonehill; N. Tagg; G. Tesic; N. Tolich; T. Tsui; R. G. van de Water; B. A. Vandevender; C. J. Virtue; D. Waller; C. E. Waltham; H. Wan Chan Tseung; D. L. Wark; P. Watson; J. Wendland; J. F. Wilkerson; J. R. Wilson; J. M. Wouters; A. Wright; M. Yeh; F. Zhang; K. Zuber

2009-01-01

235

Nitrogen and phosphorus flux rates from sediment in the lower St. Johns River estuary.  

PubMed

Internal cycling of nutrients from the sediment and water column can be an important contribution to the total nutrient load of an aquatic ecosystem. Our objective was to estimate the internal nutrient loading of the Lower St. Johns River (LSJR). Dissolved reactive phosphorus (DRP) and ammonium (NH(4)-N) flux from sediments were measured under aerobic and anaerobic water column conditions using intact cores, to estimate the overall contribution of the sediments to P and N loading to the LSJR. The DRP flux under aerobic water column conditions averaged 0.13 mg m(-2) d(-1), approximately 37 times lower than that under anaerobic conditions (4.77 mg m(-2) d(-1)). The average NH(4)-N released from the anaerobic cores (18.03 mg m(-2) d(-1)) was also significantly greater than in the aerobic cores for all sites and seasons, indicating the strong relationship between nutrient fluxes and oxygen availability in the water column. The mean annual internal DRP load was estimated to be 330 metric tons (Mg) yr(-1), 21% of the total P load to the river, while the mean annual internal load of NH(4)-N was determined to be 2066 Mg yr(-1), 28% of the total N load to the LSJR estuary. As water resource managers reduce external loading to the LSJR the frequency of anaerobic events should decline, thereby reducing nutrient fluxes from the sediment to the water column, reducing the internal loading of DRP and NH(4)-N. Results from this study demonstrate that the internal flux of nutrients from sediments may be a significant portion of the total load and should be accounted for in the total nutrient budget of the river for successful restoration. PMID:15254137

Malecki, Lynette M; White, John R; Reddy, K R

2004-01-01

236

Measurements and Phenomenological Modeling of Magnetic FluxBuildup in Spheromak Plasmas  

SciTech Connect

Internal magnetic field measurements and high-speed imaging at the Sustained Spheromak Physics Experiment (SSPX) [E. B. Hooper, L. D. Pearlstein, R. H. Bulmer, Nucl. Fusion 39, 863 (1999)] are used to study spheromak formation and field buildup. The measurements are analyzed in the context of a phenomenological model of magnetic helicity based on the topological constraint of minimum helicity in the open flux before reconnecting and linking closed flux. Two stages are analyzed: (1) the initial spheromak formation, i. e. when all flux surfaces are initially open and reconnect to form open and closed flux surfaces, and (2) the stepwise increase of closed flux when operating the gun on a new mode that can apply a train of high-current pulses to the plasma. In the first stage, large kinks in the open flux surfaces are observed in the high-speed images taken shortly after plasma breakdown, and coincide with large magnetic asymmetries recorded in a fixed insertable magnetic probe that spans the flux conserver radius. Closed flux (in the toroidal average sense) appears shortly after this. This stage is also investigated using resistive magnetohydrodynamic simulations. In the second stage, a time lag in response between open and closed flux surfaces after each current pulse is interpreted as the time for the open flux to build helicity, before transferring it through reconnection to the closed flux. Large asymmetries are seen during these events, which then relax to a slowly decaying spheromak before the next pulse.

Romero-Talamas, C A; Hooper, E B; Jayakumar, R; McLean, H S; Wood, R D; Moller, J M

2007-12-14

237

KNVK vacuum fission chambers for measuring neutron flux density  

Microsoft Academic Search

Vacuum fission chambers (VFC) are used to record the time dependence of the flux density of neutrons from nuclear reactors. Their comparatively high yield of slow secondary electrons (about 500 per fission fragment), large dynamic range, high temporal resolution, radiation resistance, and operating reliability make them superior to other detectors. However, the accuracy with which fast neutrons are recorded with

E. K. Malyshev; S. V. Chuklyaev; O. I. Shchetinin

1987-01-01

238

Comparison of Heat Flux Measurements and Calculations at an Arctic Site  

NASA Astrophysics Data System (ADS)

The complex exchanges between the atmosphere and the surface are one of the primary drivers of the changes that are occurring in the Arctic environment. These exchanges are exceedingly difficult to parameterize or observe remotely, and it is clear that flux parameterizations developed for lower latitudes and oceans are not representative in the Arctic. In response, several Arctic sites have recently installed micrometeorological flux towers with suites of instruments to produce measurements that can be used to calculate turbulent and sensible heat fluxes. These towers typically also have surface heat flux plates and active layer thermistor strings as part of the suite of instruments characterizing the near surface boundary layer. In this presentation we compare measurements from two surface heat flux plates and a one meter thermistor probe that is installed near the micrometeorological flux tower at the Tiksi Hydrometeorological Observatory in the Sakha Republic of Russia. Theoretically the direct measurement of heat flux from the plates and the calculated flux from the thermistor temperature profiles should be identical, however, it is expected that a number of biases and inconsistencies will result from inhomogeneity in surface characteristics, and within the underlying active layer, including snow cover, standing water, vegetation, soil characteristics as well as instrument measurement limitations. Quantification and error analysis of these measurement limitations are important as the surface heat flux is an important parameter in achieving closure between the heat budgets of the atmosphere and the underlying surface.

Crepinsek, S.; Uttal, T.; Sandoval, C.; Persson, O. P.; Grachev, A. A.

2013-12-01

239

Pb-210 fluxes and sedimentation rates on the lower continental slope between Taiwan and the South Okinawa Trough  

NASA Astrophysics Data System (ADS)

Pb-210 and Ra-226 have been measured on 11 cores taken from the continental slope between northern Taiwan and the western South Okinawa Trough. Ra-226 activities generally fall between 0.5 and 2 dpm g -1. Pb-210 activities are widely variable in these cores: negligible excess Pb-210 (or no Pb-210 flux) is observed on the upper and middle slope while large excess Pb-210 values (50-90 dpm g -1) are present on the lower slope. Sedimentation rates estimated from the excess Pb-210 profiles of the cores range from 0.09 to 0.52 cm y -1 (0.08 - 0.42 g cm -2 y -1) for the lower slope and decrease toward the deeper (eastern) slope. Excess Pb-210 inventories and the Pb-210 fluxes calculated from the lower slope are 320-840 dpm cm -2 and 10-26 dpm cm -2 y -1 , respectively, assuming a steady-state input at each site for the past 100 years. Atmospheric input of Pb-210 and local production from Ra-226 do not account for the observed fluxes. Two alternative explanations are proposed: (1) boundary scavenging coupled with the Kuroshio water flowing through the area; or (2) downslope transport of high Pb-210 activity fine-grained particles from the shelf and upper/middle slope to the lower slope where they are deposited.

Chung, Y.; Chang, W. C.

1995-03-01

240

SkyLine and SkyGas: Novel automated technologies for automatic GHG flux measurements  

NASA Astrophysics Data System (ADS)

1. Concerns for the future of the Earth's climate centre around the anthropogenically-driven continuing increases in atmospheric concentrations of the major 'greenhouse gases' (GHGs) which include CO2, CH4 and N2O. A major component of the global budgets for all three of these gases is the flux between the atmosphere and terrestrial ecosystems. 2. Currently, these fluxes are poorly quantified, largely due to technical limitations associated with making these flux measurements. Whilst eddy covariance systems have greatly improved such measurements at the ecosystem scale, flux measurements at the plot scale are commonly made using labour intensive traditional 'cover box' approaches; technical limitations have frequently been a bottle-neck in producing adequate and appropriate GHG flux data necessary for making land management decisions. For example, there are almost no night time flux data for N2O fluxes, and frequently such data are only measured over bare soil patches. 3. We have been addressing the design of novel field equipment for the automation of GHG flux measurements at the chamber and plot scale and will present here some of the technical solutions we have developed. These solutions include the development of the SkyLine and SkyGas approaches which resolve many of the common problems associated with making high frequency, sufficiently replicated GHG flux measurements under field conditions. 4. Unlike most other automated systems, these technologies 'fly' a single chamber to the measurement site, rather than have multiple replicated chambers and analysers. We will present data showing how such systems can deliver high time and spatial resolution flux data, with a minimum of operator intervention and, potentially, at relatively low per plot cost. We will also show how such measurements can be extended to monitoring fluxes from freshwater features in the landscape.

Ineson, Philip; Stockdale, James

2014-05-01

241

Continuous Measurements of Nitrous Oxide Fluxes Through the Seasonal Snowpack, Niwot Ridge, Colorado  

NASA Astrophysics Data System (ADS)

Until recently, microbial activity in seasonally snow covered ecosystems was thought to be limited during the snow-covered season. However, in the last decade many studies have shown that the gas fluxes through the snowpack in winter can be a significant component of the annual flux of gases produced by microbial processes in soils. Because of the logistical difficulties of winter measurements, these cumulative fluxes have often been based on weekly or even more infrequent measurements. Here we present what we believe is the first essentially continuous record of nitrous oxide fluxes through deep (up to 2 m) seasonal snowpack for a four-month period on Niwot Ridge, Colorado. Air samples were collected at four heights throughout the snowpack and analyzed for nitrous oxide on a gas chromatograph in a nearby underground laboratory. The sample collection was automated such that the concentration gradient through the snowpack was assessed every eighty minutes. In addition to nitrous oxide, the concentrations of nitric oxide, and carbon dioxide were also measured. Fluxes of these gases were then calculated based on the concentration gradient using Fick's law. This sampling design allowed us to examine the patterns of gas fluxes throughout the snowpack and at multiple temporal scales. In addition, we can compare the fluxes of multiple gases produced by microbial processes in soils. The winter fluxes can also be contrasted to growing season fluxes to estimate the contribution of winter fluxes to the annual total.

Liptzin, D.; Chowanski, K. M.; Helmig, D.; Hueber, J.; Seok, B.; Williams, M. W.

2006-12-01

242

Arrangement Analysis of Leaves Optimized on Photon Flux Density or Photosynthetic Rate  

NASA Astrophysics Data System (ADS)

By clarifying a plant evolutive process, useful information may be obtained on engineering. Consequently, an analysis algorithm that investigates the optimal arrangement of plant leaves was developed. In the developed algorithm, the Monte Carlo method is introduced and sunlight is simulated. Moreover, the arrangement optimization of leaves is analyzed using a Genetic Algorithm (GA). The number of light quanta (photon flux density) that reaches leaves, or the average photosynthetic rate of the same was set as the objective function, and leaf models of a dogwood and a ginkgo tree were analyzed. The number of leaf models was set between two to four, and the position of the leaf was expressed in terms of the angle of direction, elevation angle, rotation angle, and the representative length of the branch of a leaf. The chromosome model introduced into GA consists of information concerning the position of the leaf. Based on the analysis results, the characteristics of the leaf of an actual plant could be simulated by ensuring the algorithm had multiple constrained conditions. The optimal arrangement of leaves differs in maximization of the photon flux density, and that of the average value of a photosynthetic rate. Furthermore, the leaf form affecting the optimal arrangement of leave and also having a significant influence also on a photosynthetic rate was shown.

Obara, Shin'ya; Tanno, Itaru

243

Daytime Chamber Measurements Miss Substantial Nighttime Methane Spikes Captured by Flux Tower  

NASA Astrophysics Data System (ADS)

Methane emissions from natural wetlands are estimated to range from 105 to 278 Tg per year, making wetlands the Earth's largest natural source of methane to the atmosphere. It is well established that methane production from a wetland varies spatially and temporally with parameters such as topography, soil temperature, and soil moisture content. Numerous studies on methane emission from wetlands have been performed using static chamber measurements. While this method measures methane emission directly from a known location, it may not capture spatial heterogeneity for the landscape of interest and the choice of chamber locations may lead to non-representative estimates of methane emissions. Furthermore, these emission estimates are limited in their temporal resolution due to the amount of time required to install and sample the chambers. Few studies have compared, from a wetland, both static chamber methane measurements and continuous measurements from a flux tower. In this work we analyzed methane emissions based on both techniques using data from the 1996 BOREAS project. The mean daytime methane emission rate from chamber measurements was greater than the mean from the tower, which suggests that a small number of chambers may be inadequate to describe spatial heterogeneity. Surprisingly, the nighttime methane emissions, measured with the flux tower, were often an order of magnitude greater than emissions recorded during the day by either method. Thus, the use of only daytime measurements would lead to a substantial underestimation of total methane emissions from the wetland. We will evaluate several potential explanations for heightened nighttime emissions and evaluate how this affects our efforts to reconcile static chamber measurements with ecosystem-wide estimates based on tower methods.

Godwin, C. M.; Markfort, C. D.; McNamara, P.

2011-12-01

244

A bottom-up perspective of the net land methanol flux: synthesis of global eddy covariance flux measurements  

NASA Astrophysics Data System (ADS)

Methanol (CH3OH) is, after methane, the second most abundant VOC in the troposphere and globally represents nearly 20% of the total biospheric VOC emissions. With typical concentrations of 1-10 ppb in the continental boundary layer, methanol plays a crucial role in atmospheric chemistry, which needs to be evaluated in the light of ongoing changes in land use and climate. Previous global methanol budgets have approached the net land flux by summing up the various emission terms (namely primary biogenic and anthropogenic emissions, plant decay and biomass burning) and by subtracting dry and wet deposition, resulting in a net land flux in the range of 75-245 Tg y-1. The data underlying these budget calculations largely stem from small-scale leaf gas exchange measurements and while recently column-integrated remotely sensed methanol concentrations have become available for constraining budget calculations, there have been few attempts to contrast model calculations with direct net ecosystem-scale methanol flux measurements. Here we use eddy covariance methanol flux measurements from 8 sites in Europe and North America to study the magnitude of and controls on the diurnal and seasonal variability in the net ecosystem methanol flux. In correspondence with leaf-level literature, our data show that methanol emission and its strong environmental and biotic control (by temperature and stomatal conductance) prevailed at the more productive (agricultural) sites and at a perturbed forest site. In contrast, at more natural, less productive sites substantial deposition of methanol occurred, in particular during periods of surface wetness. These deposition processes are poorly represented by currently available temperature/light and/or production-driven modelling algorithms. A new framework for modelling the bi-directional land-atmosphere methanol exchange is proposed which accounts for the production of methanol in leaves, the regulation of leaf methanol emission by stomatal conductance and the bi-directional methanol exchange within plant canopies as governed by surface wetness and ambient methanol concentrations.

Wohlfahrt, Georg; Amelynck, Crist; Ammann, Christof; Arneth, Almut; Bamberger, Ines; Goldstein, Allen; Hansel, Armin; Heinesch, Bernhard; Holst, Thomas; Hörtnagl, Lukas; Karl, Thomas; Neftel, Albrecht; McKinney, Karena; Munger, William; Schade, Gunnar; Schoon, Niels

2014-05-01

245

Area-Averaged Surface Fluxes Over the Litfass Region Based on Eddy-Covariance Measurements  

NASA Astrophysics Data System (ADS)

Micrometeorological measurements (including eddy-covariance measurements of the surface fluxes of sensible and latent heat) were performed during the LITFASS-2003 experiment at 13 field sites over different types of land use (forest, lake, grassland, various agricultural crops) in a 20 × 20 km2 area around the Meteorological Observatory Lindenberg (MOL) of the German Meteorological Service (Deutscher Wetterdienst, DWD). Significant differences in the energy fluxes could be found between the major land surface types (forest, farmland, water), but also between the different agricultural crops (cereals, rape, maize). Flux ratios between the different surfaces changed during the course of the experiment as a result of increased water temperature of the lake, changing soil moisture, and of the vegetation development at the farmland sites. The measurements over grass performed at the boundary-layer field site Falkenberg of the MOL were shown to be quite representative for the farmland part of the area. Measurements from the 13 sites were composed into a time series of the area-averaged surface flux by taking into account the data quality of the single flux values from the different sites and the relative occurrence of each surface type in the area. Such composite fluxes could be determined for about 80% of the whole measurement time during the LITFASS-2003 experiment. Comparison of these aggregated surface fluxes with area-averaged fluxes from long-range scintillometer measurements and from airborne measurements showed good agreement.

Beyrich, Frank; Leps, Jens-Peter; Mauder, Matthias; Bange, Jens; Foken, Thomas; Huneke, Sven; Lohse, Horst; Lüdi, Andreas; Meijninger, Wouter M. L.; Mironov, Dmitrii; Weisensee, Ulrich; Zittel, Peter

2006-10-01

246

Comparison of Two Chamber Methods for Measuring Soil Trace-gas Fluxes in Bioenergy Cropping Systems  

NASA Astrophysics Data System (ADS)

Greenhouse gas emissions from soils are often measured using trace-gas flux chamber techniques without a standardized protocol, raising concerns about measurement accuracy and consistency. To address this, we compared measurements from non-steady-state non-through-flow (NTF) chambers with a non-steady-state through-flow (TF) chamber system in three bioenergy cropping systems located in Wisconsin. Additionally, we investigated the effects of NTF flux calculation method and deployment time on flux measurements. In all cropping systems, when NTF chambers were deployed for 60 min and a linear (LR) flux calculation was used, soil CO2 and N2O fluxes were, on average, 18% and 12% lower, respectively, than fluxes measured with a 15 min deployment. Fluxes calculated with the HMR method, a hybrid of non-linear and linear approaches, showed no deployment time effects for CO2 and N2O and produced 27-32% higher CO2 fluxes and 28-33% higher N2O fluxes in all crops than the LR approach with 60 min deployment. Across all crops, CO2 fluxes measured with the TF chamber system were higher by 24.4 to 84.9 mg CO2-C m-2 h-1, than fluxes measured with NTF chambers using either flux calculation method. These results suggest NTF chamber deployment time should be shortened if the LR approach is used though detection limits should be considered, and the HMR approach may be more appropriate when long deployment times are necessary. Significant differences in absolute flux values with different chamber types highlight the need for significant effort in determining the accuracy of methods or alternative flux measurement technologies. N2O fluxes with chamber deployment time for (a) all crops (switchgrass, corn, hybrid poplar) using both linear (LR) and HMR flux calculation methods, (b) each crop individually using LR approach, and (c) each crop individually using HMR approach. Given are seasonal (May-August) means + standard error. Letters indicate significant differences among deployment times (p<0.05, Tukey-Kramer test). Because there were no significant crop x deployment time interactions, significance letters are not shown in (b) and (c).

Duran, B. E.; Kucharik, C. J.

2013-12-01

247

Measurement of the cosmic ray and neutrino-induced muon flux at the Sudbury neutrino observatory  

E-print Network

Results are reported on the measurement of the atmospheric neutrino-induced muon flux at a depth of 2 kilometers below the Earth’s surface from 1229 days of operation of the Sudbury Neutrino Observatory (SNO). By measuring ...

Formaggio, Joseph A.

248

Improved radon-flux-measurement system for uranium-tailings pile measurement  

SciTech Connect

The Pacific Northwest Laboratory (PNL) is developing cover technology for uranium mill tailings that will inhibit the diffusion of radon to the atmosphere. As part of this cover program, an improved radon flux measurement system has been developed. The radon measurement system is a recirculating, pressure-balanced, flow-through system that uses activated carbon at ambient temperatures to collect the radon. With the system, an area of 0.93 m/sup 2/ is sampled for periods ranging from 1 to 12 h. The activated carbon is removed from the radon trap and the collected radon is determined by counting the /sup 214/Bi daughter product. Development of the system included studies to determine the efficiency of activated carbon, relative calibration measurements and field measurements made during 1980 at the inactive tailings pile in Grand Junction, Colorado. Results of these studies are presented.

Freeman, H.D.

1981-10-01

249

Quantitative method for measuring heat flux emitted from a cryogenic object  

DOEpatents

The present invention is a quantitative method for measuring the total heat flux, and of deriving the total power dissipation, of a heat-fluxing object which includes the steps of placing an electrical noise-emitting heat-fluxing object in a liquid helium bath and measuring the superfluid transition temperature of the bath. The temperature of the liquid helium bath is thereafter reduced until some measurable parameter, such as the electrical noise, exhibited by the heat-fluxing object or a temperature-dependent resistive thin film in intimate contact with the heat-fluxing object, becomes greatly reduced. The temperature of the liquid helum bath is measured at this point. The difference between the superfluid transition temperature of the liquid helium bath surrounding the heat-fluxing object, and the temperature of the liquid helium bath when the electrical noise emitted by the heat-fluxing object becomes greatly reduced, is determined. The total heat flux from the heat-fluxing object is determined as a function of this difference between these temperatures. In certain applications, the technique can be used to optimize thermal design parameters of cryogenic electronics, for example, Josephson junction and infra-red sensing devices.

Duncan, Robert V. (Tijeras, NM)

1993-01-01

250

Quantitative method for measuring heat flux emitted from a cryogenic object  

DOEpatents

The present invention is a quantitative method for measuring the total heat flux, and of deriving the total power dissipation, of a heat-fluxing object which includes the steps of placing an electrical noise-emitting heat-fluxing object in a liquid helium bath and measuring the superfluid transition temperature of the bath. The temperature of the liquid helium bath is thereafter reduced until some measurable parameter, such as the electrical noise, exhibited by the heat-fluxing object or a temperature-dependent resistive thin film in intimate contact with the heat-fluxing object, becomes greatly reduced. The temperature of the liquid helum bath is measured at this point. The difference between the superfluid transition temperature of the liquid helium bath surrounding the heat-fluxing object, and the temperature of the liquid helium bath when the electrical noise emitted by the heat-fluxing object becomes greatly reduced, is determined. The total heat flux from the heat-fluxing object is determined as a function of this difference between these temperatures. In certain applications, the technique can be used to optimize thermal design parameters of cryogenic electronics, for example, Josephson junction and infrared sensing devices.

Duncan, R.V.

1993-03-16

251

A fast gauge for energy flux density measurement  

NASA Astrophysics Data System (ADS)

Herein, the design and characterization of a fast energy flux density gauge are described. The gauge is based on a thermoelectrical pair with the junction made of a thin layer of silver. High absorptivity is attained by an electrolytic deposit of platinum black on the silver coat. Dynamic calibration gives a response time below 100 microsec. Computer methods to obtain the energy flux density from temperature-time history were evaluated. The results of the tests performed with igniters of pelleted boron/potassium nitrate and black powder, used in solid propellant ignition, are shown. The gauge developed can be applied to fast processes which require small response time. The gauge does not need previous calibration, it is resistant to vibrations and accelerations, and, at the same time, it is small in size, economical, and easy to build.

Garcia, Jorge; Bana de Schor, Beatriz

1990-01-01

252

Rn-222 tracing and stable isotope measurements of biogenic gas fluxes from methane saturated sediments  

NASA Technical Reports Server (NTRS)

Transport of reduced biogenic gases from anoxic sediments and soils to the atmosphere can be quantitatively studied through measurement of radon-222/radium-226 disequilibrium. In previous work, seasonal variations in biogenic gas transport mechanisms, net fluxes and overall composition were documented. Now presented are direct field measurements of radon-222 activity in gases exiting organic rich sediments which show their usefulness for tracing of the stripping of dissolved biogenic gases from within the sediment column and transport via bubble ebullition. Methane is depleted in deuterium during the summer as compared with winter months and is in general lighter than in most marine sediments signaling the probable importance of acetate as an important precursor molecule. The significant seasonal isotopic variations observed illustrate the importance of understanding mechanisms and rates of biogenic gas production in order to interpret observed tropospheric isotopic data.

Martens, Christopher S.; Green, C. D.; Blair, Neal; Chanton, J. P.

1985-01-01

253

Relationships among canopy scale energy fluxes and isoprene flux derived from long-term, seasonal eddy covariance measurements over a hardwood forest  

Microsoft Academic Search

The flux of isoprene, one of the more reactive biogenic volatile organic compounds, was measured using eddy covariance techniques on a continuous basis during the 2000–2002 growing seasons at a mixed hardwood forest in northern lower MI. Daytime fluxes of isoprene and both sensible (H) and latent heat flux (LE) were linearly correlated with a positive slope on a daily

Shelley Pressley; Brian Lamb; Hal Westberg; Christoph Vogel

2006-01-01

254

A comparison of methods for deriving solute flux rates using long-term data from streams in the mirror lake watershed  

USGS Publications Warehouse

Calculation of chemical flux rates for streams requires integration of continuous measurements of discharge with discrete measurements of solute concentrations. We compared two commonly used methods for interpolating chemistry data (time-averaging and flow-weighting) to determine whether discrepancies between the two methods were large relative to other sources of error in estimating flux rates. Flux rates of dissolved Si and SO42- were calculated from 10 years of data (1981-1990) for the NW inlet and Outlet of Mirror Lake and for a 40-day period (March 22 to April 30, 1993) during which we augmented our routine (weekly) chemical monitoring with collection of daily samples. The time-averaging method yielded higher estimates of solute flux during high-flow periods if no chemistry samples were collected corresponding to peak discharge. Concentration-discharge relationships should be used to interpolate stream chemistry during changing flow conditions if chemical changes are large. Caution should be used in choosing the appropriate time-scale over which data are pooled to derive the concentration-discharge regressions because the model parameters (slope and intercept) were found to be sensitive to seasonal and inter-annual variation. Both methods approximated solute flux to within 2-10% for a range of solutes that were monitored during the intensive sampling period. Our results suggest that errors arising from interpolation of stream chemistry data are small compared with other sources of error in developing watershed mass balances.

Bukaveckas, P.A.; Likens, G.E.; Winter, T.C.; Buso, D.C.

1998-01-01

255

Characteristics of microbial volatile organic compound flux rates from soil and plant litter  

NASA Astrophysics Data System (ADS)

Our knowledge of microbial production and consumption of volatile organic compounds (VOCs) from soil and litter, as well as which microorganisms are involved, is relatively limited compared to what we know about VOC emissions from terrestrial plants. With climate change expecting to alter plant community composition, nitrogen (N) deposition rates, mean annual temperatures, precipitation patterns, and atmospheric VOC concentrations, it is unknown how microbial production and consumption of VOCs from litter and soil will respond. We have spent the last 5 years quantifying VOC flux rates in decaying plant litter, mineral soils and from a subalpine field site using a proton transfer reaction mass spectrometer (PTR-MS). Microbial production, relative to abiotic sources, accounted for 78% to 99% of the total VOC emissions from decomposing litter, highlighting the importance of microbial metabolisms in these systems. Litter chemistry correlated with the types of VOCs emitted, of which, methanol was emitted at the highest rates from all studies. The net emissions of carbon as VOCs was found to be up to 88% of that emitted as CO2 suggesting that VOCs likely represent an important component of the carbon cycle in many terrestrial systems. Nitrogen additions drastically reduced VOC emissions from litter to near zero, though it is still not understood whether this was due to an increase in consumption or a decrease in production. In the field, the root system contributed to 53% of the carbon that was emitted as VOCs from the soil with increasing air temperatures correlating to an increase in VOC flux rates from the soil system. Finally, we are currently utilizing next generation sequencing techniques (Illumina MiSeq) along with varying concentrations of isoprene, the third most abundant VOC in the atmosphere behind methane and methanol, above soils in a laboratory incubation to determine consumption rates and the microorganisms (bacteria, archaea and fungi) associated with the consumption of isoprene in soils. To our knowledge, this is a novel technique for identifying microorganisms associated with consumption without the use of culturing or isotopic labeling. Together, these series of studies are moving us toward a predictive understanding of VOC fluxes and microbial ecology in soil and litter.

Gray, C. M.; Fierer, N.

2013-12-01

256

Remote Measurement of Heat Flux from Power Plant Cooling Lakes  

SciTech Connect

Laboratory experiments have demonstrated a correlation between the rate of heat loss q? from an experimental fluid to the air above and the standard deviation ? of the thermal variability in images of the fluid surface. These experimental results imply that q? can be derived directly from thermal imagery by computing ?. This paper analyses thermal imagery collected over two power plant cooling lakes to determine if the same relationship exists. Turbulent boundary layer theory predicts a linear relationship between q? and ? when both forced (wind driven) and free (buoyancy driven) convection are present. Datasets derived from ground- and helicopter-based imagery collections had correlation coefficients between ? and q? of 0.45 and 0.76, respectively. Values of q? computed from a function of ? and friction velocity u* derived from turbulent boundary layer theory had higher correlations with measured values of q? (0.84 and 0.89). This research may be applicable to the problem of calculating losses of heat from the ocean to the atmosphere during high-latitude cold-air outbreaks because it does not require the information typically needed to compute sensible, evaporative, and thermal radiation energy losses to the atmosphere.

Garrett, A.; Kurzeja, R.; Villa-Aleman, E.; Bollinger, J.

2013-01-01

257

Satellite Angular Rate Estimation From Vector Measurements  

NASA Technical Reports Server (NTRS)

This paper presents an algorithm for estimating the angular rate vector of a satellite which is based on the time derivatives of vector measurements expressed in a reference and body coordinate. The computed derivatives are fed into a spacial Kalman filter which yields an estimate of the spacecraft angular velocity. The filter, named Extended Interlaced Kalman Filter (EIKF), is an extension of the Kalman filter which, although being linear, estimates the state of a nonlinear dynamic system. It consists of two or three parallel Kalman filters whose individual estimates are fed to one another and are considered as known inputs by the other parallel filter(s). The nonlinear dynamics stem from the nonlinear differential equation that describes the rotation of a three dimensional body. Initial results, using simulated data, and real Rossi X ray Timing Explorer (RXTE) data indicate that the algorithm is efficient and robust.

Azor, Ruth; Bar-Itzhack, Itzhack Y.; Harman, Richard R.

1996-01-01

258

Soil Greenhouse Gas Flux Measurements in a Pacific Northwestern Douglas-fir Forest  

NASA Astrophysics Data System (ADS)

Forests and forest soils are dynamic sources and sinks for greenhouse gases (GHG). Climate and management practices can impact the GHG balance of a forest. Motivated by the contemporary scientific understanding of climate change, carbon (C) cycle studies to date have largely been concerned with carbon dioxide (CO2) fluxes. Methane (CH4) and nitrous oxide (N2O) are less abundant trace gases, but with large greenhouse warming potentials and differing lifetimes in the atmosphere, CH4 and N2O are also significant global warming contributors, warranting careful consideration when trying to determine complete GHG balances. Soil fluxes of CO2, CH4 and N2O were measured at a Pacific Northwestern Douglas-fir forest on Vancouver Island, BC, Canada (49o 52' N, 125o 20' W). Samples were syringe collected (0, 3, 10, 20, 30 min) and transferred to pre-evacuated 12-ml vials (Exetainers, Labco Limited, Buckinghamshire, UK) once a month (Oct-Dec, 2011) from each of 16 closed-chambers in order to determine soil GHG flux rates. Samples were analysed using an Agilent 7890A Gas Chromatography (GC) system for CO2 and CH4 using a Flame Ionisation Detector (FID) with methanizer, and for N2O using an Electron Capture Detector (ECD). Resulting data were analysed using the HMR package implemented with the R language for statistical computing to determine the best fit for flux estimation considering linear and non-linear Hutchinson and Mosier models. The presence of outliers and questionable features in the data resulted in the need for careful data screening. Initial results suggest that the CH4sink strength of these soils decrease during the cooling and increasingly wet autumn to winter months (3.6-2.6 ?mol m-2hr-1). Low concentrations of N2O made it difficult to quantify any emissions (0.15-0.05 ?mol m-2hr-1), while CO2 was emitted to the atmosphere (2.05-0.75 ?mol m-2s-1). Monthly results for Jan-Mar 2012 will be included. Results of CO2 fluxes measured by GC using the closed-chambers compared with a portable flow-through (4 L min-1) chamber with a LI-COR Inc LI 840 infrared gas analyzer using collars installed in close proximity will be presented. Developments made on a flow-through chamber design for CH4 will be discussed.

Hawthorne, I.; Johnson, M. S.; Jassal, R.; Black, T. A.; Webster, C.

2012-04-01

259

Continuous Measurement of Methane Ebullition Flux from a Northern Peatland using a Fast Methane Analyzer  

NASA Astrophysics Data System (ADS)

Northern peatlands are an important source of methane (CH4) release to the atmosphere, estimated at between 20 and 50 Tg/yr. Recent work on CH4 emissions from peatlands has demonstrated that ebullition can be a more important emission pathway than previously assumed. However, accurate quantification of the atmospheric CH4 burden due to ebullition is still very limited because ebullition exhibits high spatiotemporal variability such that sudden episodic events are difficult to capture and quantify with existing experimental methods. We have initiated a novel measurement program to better quantify the spatiotemporal variability in CH4 flux in peatlands, and to examine potential effects of vegetation and environmental factors, e.g. atmospheric pressure, water table, etc on these releases. A flow-through system was designed, consisting of a closed static chamber and a fast methane analyzer (FMA) (LI-COR model 7700) that has been employed at both the field and laboratory scale. The CH4 concentration in the air flowing through the chamber is continuously measured by the analyzer and used to reconstruct continuous CH4 emission fluxes. The high sampling rate of the FMA makes it sensitive to both ebullition and diffusion of gaseous CH4, capturing short duration, episodic ebullition fluxes. Non-steady static chamber measurements were also conducted to cross-validate the continuous measurements. Results acquired during summer 2011 show that episodic ebullition occurred more frequently at the pool site where previous studies indicate extensive wood layers at depth and the vegetation was a mix of Sphagnum and wooded heath. During a 3 day period of continuous measurements captured the passage of a tropical storm Irene, where short term episodic releases of CH4, ranging from 113 mg CH4/m2/d to 202 mg CH4/m2/d, were observed at the time of lowest atmospheric pressure, providing new evidence that atmospheric pressure is an important factor to controlling CH4 ebullition from peatlands. While traditional techniques, e.g. static chamber measurement can only occasionally detect the occurrence of ebullition, the continuous measurement by using a flow-through system is able to resolve spatiotemporal complexity of episodic CH4 ebullition events. These continuous CH4 measurements provide new insights into the timing of CH4 ebullition from peatlands to the atmosphere as climate changes and the role of environmental variables in regulating these CH4 releases.

Zhongjie, Y.; Schafer, K. V.; Slater, L. D.; Varner, R. K.; Amante, J.; Comas, X.; Reeve, A. S.; Alcivar, W.; Gonzalez, D.

2012-12-01

260

Measurement of the Cosmic Ray and Neutrino-Induced Muon Flux at the Sudbury Neutrino Observatory  

SciTech Connect

Results are reported on the measurement of the atmospheric neutrino-induced muon flux at a depth of 2 kilometers below the Earth's surface from 1229 days of operation of the Sudbury Neutrino Observatory (SNO). By measuring the flux of through-going muons as a function of zenith angle, the SNO experiment can distinguish between the oscillated and un-oscillated portion of the neutrino flux. A total of 514 muon-like events are measured between -1 {le} cos {theta}{sub zenith} 0.4 in a total exposure of 2.30 x 10{sup 14} cm{sup 2} s. The measured flux normalization is 1.22 {+-} 0.09 times the Bartol three-dimensional flux prediction. This is the first measurement of the neutrino-induced flux where neutrino oscillations are minimized. The zenith distribution is consistent with previously measured atmospheric neutrino oscillation parameters. The cosmic ray muon flux at SNO with zenith angle cos {theta}{sub zenith} > 0.4 is measured to be (3.31 {+-} 0.01 (stat.) {+-} 0.09 (sys.)) x 10{sup -10} {micro}/s/cm{sup 2}.

SNO collaboration; Aharmim, B.; Ahmed, S.N.; Andersen, T.C.; Anthony, A.E.; Barros, N.; Beier, E.W.; Bellerive, A.; Beltran, B.; Bergevin, M.; Biller, S.D.; Boudjemline, K.; Boulay, M.G.; Burritt, T.H.; Cai, B.; Chan, Y.D.; Chen, M.; Chon, M.C.; Cleveland, B.T.; Cox-Mobrand, G.A.; Currat, C.A.; Dai, X.; Dalnoki-Veress, F.; Deng, H.; Detwiler, J.; Doe, P.J.; Dosanjh, R.S.; Doucas, G.; Drouin, P.-L.; Duncan, F.A.; Dunford, M.; Elliott, S.R.; Evans, H.C.; Ewan, G.T.; Farine, J.; Fergani, H.; Fleurot, F.; Ford, R.J.; Formaggio, J.A.; Gagnon, N.; Goon, J.TM.; Grant, D.R.; Guillian, E.; Habib, S.; Hahn, R.L.; Hallin, A.L.; Hallman, E.D.; Hargrove, C.K.; Harvey, P.J.; Harvey, P.J.; Heeger, K.M.; Heintzelman, W.J.; Heise, J.; Helmer, R.L.; Hemingway, R.J.; Henning, R.; Hime, A.; Howard, C.; Howe, M.A.; Huang, M.; Jamieson, B.; Jelley, N.A.; Klein, J.R.; Kos, M.; Kruger, A.; Kraus, C.; Krauss, C.B.; Kutter, T.; Kyba, C.C.M.; Lange, R.; Law, J.; Lawson, I.T.; Lesko, K.T.; Leslie, J.R.; Levine, I.; Loach, J.C.; Luoma, S.; MacLellan, R.; Majerus, S.; Mak, H.B.; Maneira, J.; Marino, A.D.; Martin, R.; McCauley, N.; McDonald, A.B.; McGee, S.; Mifflin, C.; Miller, M.L.; Monreal, B.; Monroe, J.; Noble, A.J.; Oblath, N.S.; Okada, C.E.; O?Keeffe, H.M.; Opachich, Y.; Orebi Gann, G.D.; Oser, S.M.; Ott, R.A.; Peeters, S.J.M.; Poon, A.W.P.; Prior, G.; Rielage, K.; Robertson, B.C.; Robertson, R.G.H.; Rollin, E.; Schwendener, M.H.; Secrest, J.A.; Seibert, S.R.; Simard, O.; Simpson, J.J.; Sinclair, D.; Skensved, P.; Smith, M.W.E.; Sonley, T.J.; Steiger, T.D.; Stonehill, L.C.; Tagg, N.; Tesic, G.; Tolich, N.; Tsui, T.; Van de Water, R.G.; VanDevender, B.A.; Virtue, C.J.; Waller, D.; Waltham, C.E.; Wan Chan Tseung, H.; Wark, D.L.; Watson, P.; Wendland, J.; West, N.; Wilkerson, J.F.; Wilson, J.R.; Wouters, J.M.; Wright, A.; Yeh, M.; Zhang, F.; Zuber, K.

2009-02-16

261

Measurement of the Cosmic Ray and Neutrino-Induced Muon Flux at the Sudbury Neutrino Observatory  

E-print Network

Results are reported on the measurement of the atmospheric neutrino-induced muon flux at a depth of 2 kilometers below the Earth's surface from 1229 days of operation of the Sudbury Neutrino Observatory (SNO). By measuring the flux of through-going muons as a function of zenith angle, the SNO experiment can distinguish between the oscillated and un-oscillated portion of the neutrino flux. A total of 514 muon-like events are measured between $-1 \\le \\cos{\\theta}_{\\rm zenith} \\le 0.4$ in a total exposure of 2.30\\times 10^{14}$ cm$^{2}$ s. The measured flux normalization is $1.22 \\pm 0.09$ times the Bartol three-dimensional flux prediction. This is the first measurement of the neutrino-induced flux where neutrino oscillations are minimized. The zenith distribution is consistent with previously measured atmospheric neutrino oscillation parameters. The cosmic ray muon flux at SNO with zenith angle $\\cos{\\theta}_{\\rm zenith} > 0.4$ is measured to be $(3.31 \\pm 0.01 {\\rm (stat.)} \\pm 0.09 {\\rm (sys.)}) \\times 10^{-10}~\\mu$/s/cm$^{2}$.

SNO Collaboration

2009-02-16

262

Time and Space Resolved Wall Temperature Measurements during Nucleate Boiling with Constant Heat Flux Boundary Conditions  

NASA Technical Reports Server (NTRS)

The lack of temporally and spatially resolved measurements under nucleate bubbles has complicated efforts to fully explain pool-boiling phenomena. The objective of this current work is to acquire time and space resolved temperature distributions under nucleate bubbles on a constant heat flux surface. This was performed using a microheater array with 100 micron resolution that allowed effectively simultaneous measurements of surface temperature while supplying a constant dissipative heat flux. This data is then correlated with high speed (> 1000Hz) visual recordings of the bubble growth and departure from the heater surface acquired from below and from the side of the heater. The data indicate that a significant source of energy during bubble nucleation and initial growth is the superheated layer around the bubble. Bubble coalescence was not observed to decrease surface temperature as significantly as bubble departure from the surface. Since bubble departure is typically followed by a sharp increase in the heater surface temperature, it is surmised that the departing bubble effectively removes the superheated layer, allowing a high local heat transfer rate with the bulk fluid through transient conduction/micro-convection during rewetting.

Myers, Jerry G.; Hussey, Sam W.; Yee, Glenda F.; Yerramilli, Vamsee K.; Kim, Jungho

2005-01-01

263

A comparison of six methods for measuring soil-surface carbon dioxide fluxes  

USGS Publications Warehouse

Measurements of soil-surface CO2 fluxes are important for characterizing the carbon budget of boreal forests because these fluxes can be the second largest component of the budget. Several methods for measuring soil-surface CO2 fluxes are available: (1) closed-dynamic-chamber systems, (2) closed-static-chamber systems, (3) open-chamber systems, and (4) eddy covariance systems. This paper presents a field comparison of six individual systems for measuring soil-surface CO2 fluxes with each of the four basic system types represented. A single system is used as a reference and compared to each of the other systems individually in black spruce (Picea mariana), jack pine (Pinus banksiana), or aspen (Populus tremuloides) forests. Fluxes vary from 1 to 10 ??mol CO2 m-2 s-1. Adjustment factors to bring all of the systems into agreement vary from 0.93 to 1.45 with an uncertainty of about 10-15%.

Norman, J.M.; Kucharik, C.J.; Gower, S.T.; Baldocchi, D.D.; Crill, P.M.; Rayment, M.; Savage, K.; Striegl, R.G.

1997-01-01

264

Development of Test Method for Measuring Sintering Temperature of Mould Fluxes  

Microsoft Academic Search

Excessive sintering of mould fluxes can readily cause defects and sticker breakouts in continuously cast strands. Studying the sintering property is important to minimize problems related to sintering arising from the use of mould fluxes in continuous casting. An effective method of measuring the apparent sintering temperature has been developed in this study. The method is based on monitoring the

Qian WANG; Yong-jian LU; Sheng-ping HE; Li-juan WANG; KC Mills

2011-01-01

265

Field measurement of small ozone fluxes to snow, wet bare soil, and lake water  

Microsoft Academic Search

Eddy-correlation measurements over snow, wet bare soil, and lake water indicate very small vertical ozone fluxes. Adjustments to the small vertical fluxes are needed to take into account the effect of mean Stefan flow associated with evaporation at the surface and the effects of correlation between density variations and vertical wind fluctuations. For snow, the residual resistance calculated for the

M. L. Wesely; D. R. Cook; R. M. Williams

1981-01-01

266

Absolute beam flux measurement at NDCX-I using gold-melting calorimetry technique  

SciTech Connect

We report on an alternative way to measure the absolute beam flux at the NDCX-I, LBNL linear accelerator. Up to date, the beam flux is determined from the analysis of the beam-induced optical emission from a ceramic scintilator (Al-Si). The new approach is based on calorimetric technique, where energy flux is deduced from the melting dynamics of a gold foil. We estimate an average 260 kW/cm2 beam flux over 5 {micro}s, which is consistent with values provided by the other methods. Described technique can be applied to various ion species and energies.

Ni, P.A.; Bieniosek, F.M.; Lidia, S.M.; Welch, J.

2011-04-01

267

Enhancing the precision and accuracy within and among AmeriFlux site measurements  

SciTech Connect

This is the final report for AmeriFlux QA/QC at Oregon State University. The major objective of this project is to contribute to the AmeriFlux network by continuing to build consistency in AmeriFlux measurements by addressing objectives stated in the AmeriFlux strategic plan and self evaluation, the North American Carbon Program, and the US Carbon Cycle Science Program. The project directly contributes to NACP and CCSP goals to establish an integrated, near-real time network of observations to inform climate change science.

Law, Bev

2013-11-25

268

Quantifying particle size and turbulent scale dependence of dust flux in the Sahara using aircraft measurements  

NASA Astrophysics Data System (ADS)

first size-resolved airborne measurements of dust fluxes and the first dust flux measurements from the central Sahara are presented and compared with a parameterization by Kok (2011a). High-frequency measurements of dust size distribution were obtained from 0.16 to 300 µm diameter, and eddy covariance fluxes were derived. This is more than an order of magnitude larger size range than previous flux estimates. Links to surface emission are provided by analysis of particle drift velocities. Number flux is described by a -2 power law between 1 and 144 µm diameter, significantly larger than the 12 µm upper limit suggested by Kok (2011a). For small particles, the deviation from a power law varies with terrain type and the large size cutoff is correlated with atmospheric vertical turbulent kinetic energy, suggesting control by vertical transport rather than emission processes. The measured mass flux mode is in the range 30-100 µm. The turbulent scales important for dust flux are from 0.1 km to 1-10 km. The upper scale increases during the morning as boundary layer depth and eddy size increase. All locations where large dust fluxes were measured had large topographical variations. These features are often linked with highly erodible surface features, such as wadis or dunes. We also hypothesize that upslope flow and flow separation over such features enhance the dust flux by transporting large particles out of the saltation layer. The tendency to locate surface flux measurements in open, flat terrain means these favored dust sources have been neglected in previous studies.

Rosenberg, Philip D.; Parker, Douglas J.; Ryder, Claire L.; Marsham, John H.; Garcia-Carreras, Luis; Dorsey, James R.; Brooks, Ian M.; Dean, Angela R.; Crosier, Jonathon; McQuaid, James B.; Washington, Richard

2014-06-01

269

Correcting airborne flux measurements for aircraft speed variation  

NASA Astrophysics Data System (ADS)

Airplane aerodynamic characteristics correlate aircraft speed with vertical wind velocity, making the time average inappropriate for estimating the ensemble average in airborne eddy-correlation flux computations. The space average, the proper form, is implemented as a time integral by a transformation of variables, which can be interpreted as a ground-speed correction to the time average. The mathematical forms are presented, and the importance of the speed correction is illustrated with airborne data. The computed correction is found to be highly variable, depending on both the turbulent flow encountered and the aircraft used. In general, the speed connection becomes more important as airplane size is reduced. For a small, single-engine Long-EZ airplane, used as an example, the straight time average erred, half the time, by 12%, 10%, 20%, and 15%, respectively, for computed fluxes of momentum, heat, moisture, and CO2. For a much heavier Twin Otter airplane, also used as an example, the straight time average erred, half the time by only 1%. These errors increased with decreasing altitude for the Long-EZ and with increasing altitude for the Twin Otter.

Crawford, Timothy L.; McMillen, Robert T.; Dobosy, Ronald J.; MacPherson, Ian

1993-11-01

270

Measurement of magnetic helicity flux into the solar corona  

NASA Astrophysics Data System (ADS)

We developed a new methodology which can determine magnetic helicity flux across the photosphere based on the magnetograph observation, In order to derive the helicity flux, first the velocity tangential to the solar surface is constructed by applying a correlation tracking technique on the magnetic observation, and secondly the velocity component across the photosphere is derived from the condition that the magnetic evolution must be consistent with the induction equation, Through this procedure, we can determine the helicity flow across the photosphere as a function of time and space, Based on this new method, we analyzed magnetic helicity of the active regions NOAA 9026 and 9077. using the data taken by SOHO/MDI and the vector magnetograph at NAOJ/Tokyo. As a result, it was revealed that positive and negative helicity is supplied in each region simultaneously. In particular, temporary activation of the helicity injection of the both signs was observed prior to X-class flare events in the GOES classification. The investigation on the helicity distribution suggests some relationship between flare onset and the increase of complexity in the helicity structure.

Kusano, K.; Maeshiro, T.; Yokoyama, T.; Sakurai, T.

271

Measuring the Natural Rate of Interest  

Microsoft Academic Search

The natural rate of interest-the real interest rate consistent with output equaling its natural rate and stable inflation-plays a central role in macroeconomic theory and monetary policy. Estimation of the natural rate of interest, however, has received little attention. We apply the Kalman filter to estimate jointly time-varying natural rates of interest and output and trend growth. We find a

Thomas Laubach; John C. Williams

2003-01-01

272

A framework to utilize turbulent flux measurements for mesoscale models and remote sensing applications  

NASA Astrophysics Data System (ADS)

Meteorologically measured fluxes of energy and matter between the surface and the atmosphere originate from a source area of certain extent, located in the upwind sector of the device. The spatial representativeness of such measurements is strongly influenced by the heterogeneity of the landscape. The footprint concept is capable of linking observed data with spatial heterogeneity. This study aims at upscaling eddy covariance derived fluxes to a grid size of 1 km edge length, which is typical for mesoscale models or low resolution remote sensing data. Here an upscaling strategy is presented, utilizing footprint modelling and SVAT modelling as well as observations from a target land-use area. The general idea of this scheme is to model fluxes from adjacent land-use types and combine them with the measured flux data to yield a grid representative flux according to the land-use distribution within the grid cell. The performance of the upscaling routine is evaluated with real datasets, which are considered to be land-use specific fluxes in a grid cell. The measurements above rye and maize fields stem from the LITFASS experiment 2003 in Lindenberg, Germany and the respective modelled timeseries were derived by the SVAT model SEWAB. Contributions from each land-use type to the observations are estimated using a forward lagrangian stochastic model. A representation error is defined as the error in flux estimates made when accepting the measurements unchanged as grid representative flux and ignoring flux contributions from other land-use types within the respective grid cell. Results show that this representation error can be reduced up to 56 % when applying the spatial integration. This shows the potential for further application of this strategy, although the absolute differences between flux observations from rye and maize were so small, that the spatial integration would be rejected in a real situation. Corresponding thresholds for this decision have been estimated as a minimum mean absolute deviation in modelled timeseries of the different land-use types with 35 W m-2 for the sensible heat flux and 50 W m-2 for the latent heat flux. Finally, a quality lagging scheme to classify the data with respect to representativeness for a given grid cell is proposed, based on an overall flux error estimate. This enables the data user to infer the uncertainty of mesoscale models and remote sensing products with respect to ground observations. Major uncertainty sources remaining are the lack of an adequate method for energy balance closure correction as well as model structure and parameter estimation, when applying the model for surfaces without flux measurements.

Babel, W.; Huneke, S.; Foken, T.

2011-05-01

273

Whole-body calcium flux rates in cichlid teleost fish Oreochromis mossambicus adapted to freshwater  

SciTech Connect

Radiotracer techniques were used to measure influx and efflux rates of CaS in freshwater-adapted Oreochromis mossambicus. The influx rate of CaS is related to body weight (W) as Fin = 50W0.805 nmol CaS /h. For a 20-g fish the calculated influx rate was 558 nmol CaS /h, and this was attributed largely to extraintestinal uptake since the drinking rate was estimated to be only 28 microliter water/h, which corresponds to an intake of 22.4 nmol CaS /h. The CaS efflux rate was calculated using the initial rate of appearance of radiotracer in the ambient water and the specific activity of plasma CaS . Tracer efflux rates were constant over 6-8 h, which indicated that there was no substantial loss of tracer in either the urine or the feces because this would have resulted in random bursts of tracer loss. Efflux rates then primarily represent integumentary and presumably branchial efflux rates. The efflux rate of CaS is related to body weight as Fout = 30W0.563 nmol CaS /h, which means an efflux rate of 162 nmol CaS /h for a 20-g fish. The net whole-body CaS influx, calculated as Fnet = Fin - Fout, was 396 nmol/h for a 20-g fish, which proves that the ambient water is an important source of CaS .

Flik, G.; Fenwick, J.C.; Kolar, Z.; Mayer-Gostan, N.; Wendelaar Bonga, S.E.

1985-10-01

274

A Measurement of the Flux of Secondary Cosmic Ray Muons and Protons in the Earth's Atmosphere  

NASA Astrophysics Data System (ADS)

A measurement of the absolute fluxes of secondary protons and muons as a function of depth in the atmosphere is made using data collected during the 1994 ascent of the High Energy Antimatter Telescope (HEAT), a large acceptance balloon-borne magnetic spectrometer. The HEAT instrument and first flight are described in detail, especially the electromagnetic calorimeter design, data analysis, and performance. The Monte Carlo simulation of the HEAT instrument using GEANT is also described in detail. Results for the muon charge ratio, absolute flux of ?±, and absolute flux of protons are given in the momentum interval 0.4-1.0 GeV/c. The absolute flux of ?sp- is extended out to 40 GeV/c because the proton background is not present in negative rigidities. To date, Monte Carlo methods for the calculation of fluxes of atmospheric neutrinos have shown an anomalously large value of the atmospheric ??/? e flux ratio as compared to measurements by several large underground detectors. Possible reasons for the anomaly are reviewed. The experimental result is in agreement with previously measured atmospheric muon fluxes. A toy Monte Carlo simulation of the atmosphere was developed using GEANT which reproduces the charge ratio of muons well, but fails to reproduce the absolute fluxes of muons well below 1 GeV, especially at high altitude. The results do not require modification of current theories regarding the source of the atmospheric neutrino anomaly.

Schneider, Eric John

1997-08-01

275

An inter-comparison of surface energy flux measurement systems used during FIFE, 1987  

NASA Technical Reports Server (NTRS)

During the first International Satellite Land Surface Climatology Program Field Experiment (FIFE-87), surface energy fluxes were measured at 22 flux sites by nine groups of scientists using different measuring systems. A rover Bowen ratio station was taken to nearly all the flux stations to serve as a reference for estimating the instrument related differences. The rover system was installed within a few meters from the host instrument of a site. Net radiation, Bowen ratio, and latent heat fluxes were compared between the rover and the host for the stations visited. Linear regression analysis was used to examine the relationship between rover measurements and host measurements. These inter-comparisons are needed to examine the influence of instrumentation on measurement uncertainty. Highly significant effects of instrument type were detected from these comparisons. Instruments of the same type showed average differences of less than 5 percent for net radiation, 10 percent for Bowen ratio, and 6 percent for latent heat flux. The corresponding average differences for different types of instruments can be up to 10, 30, and 20 percent respectively. The Didcot net radiometer gave higher net radiation while the Swissteco type showed lower values, as compared to the corrected REBS model. The 4-way components methed and the Thornswaite type give similar values to the REBS. The SERBS type Bowen ratio systems exhibit slightly lower Bowen ratios and thus higher latent heat fluxes, compared to the AZET systems. Eddy correlation systems showed slightly lower latent heat flux in comparison to the Bowen ratio systems.

Nie, D.; Kanemasu, E. T.; Fritschen, L. J.; Weaver, H.; Smith, E. A.; Verma, S. B.; Field, R. T.; Kustas, W.; Stewart, J. B.

1990-01-01

276

Independent Measurement of the Total Active B8 Solar Neutrino Flux Using an Array of He3 Proportional Counters at the Sudbury Neutrino Observatory  

Microsoft Academic Search

The Sudbury Neutrino Observatory (SNO) used an array of He3 proportional counters to measure the rate of neutral-current interactions in heavy water and precisely determined the total active (nux) B8 solar neutrino flux. This technique is independent of previous methods employed by SNO. The total flux is found to be 5.54-0.31+0.33(stat)-0.34+0.36(syst)×106cm-2s-1, in agreement with previous measurements and standard solar models.

B. Aharmim; S. N. Ahmed; J. F. Amsbaugh; A. E. Anthony; J. Banar; N. Barros; E. W. Beier; A. Bellerive; B. Beltran; M. Bergevin; S. D. Biller; K. Boudjemline; M. G. Boulay; T. J. Bowles; M. C. Browne; T. V. Bullard; T. H. Burritt; B. Cai; Y. D. Chan; D. Chauhan; M. Chen; B. T. Cleveland; G. A. Cox-Mobrand; C. A. Currat; X. Dai; H. Deng; J. Detwiler; M. Dimarco; P. J. Doe; G. Doucas; P.-L. Drouin; C. A. Duba; F. A. Duncan; M. Dunford; E. D. Earle; S. R. Elliott; H. C. Evans; G. T. Ewan; J. Farine; H. Fergani; F. Fleurot; R. J. Ford; J. A. Formaggio; M. M. Fowler; N. Gagnon; J. V. Germani; A. Goldschmidt; J. T. M. Goon; K. Graham; E. Guillian; S. Habib; R. L. Hahn; A. L. Hallin; E. D. Hallman; A. A. Hamian; G. C. Harper; P. J. Harvey; R. Hazama; K. M. Heeger; W. J. Heintzelman; J. Heise; R. L. Helmer; R. Henning; A. Hime; C. Howard; M. A. Howe; M. Huang; P. Jagam; B. Jamieson; N. A. Jelley; K. J. Keeter; J. R. Klein; L. L. Kormos; M. Kos; A. Krüger; C. Kraus; C. B. Krauss; T. Kutter; C. C. M. Kyba; R. Lange; J. Law; I. T. Lawson; K. T. Lesko; J. R. Leslie; J. C. Loach; R. MacLellan; S. Majerus; H. B. Mak; J. Maneira; R. Martin; K. McBryde; N. McCauley; A. B. McDonald; S. McGee; C. Mifflin; G. G. Miller; M. L. Miller; B. Monreal; J. Monroe; B. Morissette; A. Myers; B. G. Nickel; A. J. Noble; N. S. Oblath; H. M. O'Keeffe; R. W. Ollerhead; G. D. Orebi Gann; S. M. Oser; R. A. Ott; S. J. M. Peeters; A. W. P. Poon; G. Prior; S. D. Reitzner; K. Rielage; B. C. Robertson; R. G. H. Robertson; E. Rollin; M. H. Schwendener; J. A. Secrest; S. R. Seibert; O. Simard; J. J. Simpson; L. Sinclair; P. Skensved; M. W. E. Smith; T. D. Steiger; L. C. Stonehill; G. Tesic; P. M. Thornewell; N. Tolich; T. Tsui; C. D. Tunnell; T. van Wechel; R. van Berg; B. A. Vandevender; C. J. Virtue; T. J. Walker; B. L. Wall; D. Waller; H. Wan Chan Tseung; J. Wendland; J. B. Wilhelmy; J. F. Wilkerson; J. R. Wilson; J. M. Wouters; A. Wright; M. Yeh; F. Zhang; K. Zuber

2008-01-01

277

Apparatus for measuring high-flux heat transfer in radiatively heated compact exchangers  

NASA Technical Reports Server (NTRS)

An apparatus is described which can deliver uniform heat flux densities of up to 80 W/sq cm over an area 7.8 cm x 15.2 cm for use in measuring the heat transfer and pressure drop in thin (6 mm or less), compact heat exchangers. Helium gas at flow rates of 0 to 40 kg/h and pressures to 6.9 MPa (1000 psi) is the working fluid. The instrumentation used in the apparatus and the methods for analyzing the data is described. The apparatus will be used initially to test the performance of prototype cooling jackets for the engine struts of the National Aerospace Plane (NASP).

Olson, Douglas A.

1989-01-01

278

Measuring Degradation Rates Without Irradiance Data  

Microsoft Academic Search

A method to report PV system degradation rates without using irradiance data is demonstrated. First, a set of relative degradation rates are determined by comparing daily AC final yields from a group of PV systems relative to the average final yield of all the PV systems. Then, the difference between relative and absolute degradation rates is found from a statistical

S. Pulver; D. Cormode; A. Cronin; D. Jordan; S. Kurtz; R. Smith

2011-01-01

279

Measuring degradation rates without irradiance data  

Microsoft Academic Search

A method to report photovoltaic (PV) system degradation rates without using irradiance data is demonstrated. First, a set of relative degradation rates are determined by comparing daily AC final yields from a group of PV systems relative to the average final yield of all the PV systems. Then, the difference between relative and absolute degradation rates is found using a

Steve Pulver; Daniel Cormode; Alex Cronin; Dirk Jordan; Sarah Kurtz; Ryan Smith

2010-01-01

280

Study on methodology of LED's luminous flux measurement with integrating sphere  

NASA Astrophysics Data System (ADS)

Errors are introduced when using traditional methods for measuring the total luminous flux of LEDs since an LED is quite different from traditional light sources in terms of physical size, flux level, spectrum and spatial distribution. This paper uses commercial lighting simulation software named Tracepro to simulate the self-absorption effect when using traditional integrating sphere methods to measure the total luminous flux of LEDs and then presents a modified method for the measurement. The LED under investigation or a specially designed narrow beam standard lamp is placed on the interior wall of the sphere in our method. The results show that the measurement method presented here can lead to better precision in the evaluation of the total luminous flux of LEDs.

Liu, Mu-Qing; Zhou, Xiao-Li; Li, Wen-Yi; Chen, Yu-Yang; Zhang, Wan-Lu

2008-07-01

281

Eddy covariance flux measurements of pollutant gases in urban Mexico City  

E-print Network

Eddy covariance (EC) flux measurements of the atmosphere/surface exchange of gases over an urban area are a direct way to improve and evaluate emissions inventories, and, in turn, to better understand urban atmospheric ...

Velasco, Erik

282

FFTF (Fast Flux Test Facility) Integrated Leak Rate Test Computer System  

SciTech Connect

The Fast Flux Test Facility (FFTF) is a liquid-metal-cooled test reactor located on the Hanford Site. The FFTF is the only reactor of this type designed and operated with the intent of meeting the licensing requirements of the Nuclear Regulatory Commission (NRC). Unique characteristics of the FFTF that present special challenges related to leak rate testing include thin wall containment vessel construction, cover gas systems that penetrate containment, and a low-pressure design basis accident. The successful completion in 1986 of the third FFTF Integrated Leak Rate Test (ILRT) five days ahead of schedule and 10% under budget was a major achievement for the Westinghouse Hanford Company. The success of this operational safety test was due in large part to a special local area network (LAN) of three IBM PC/XT computers that monitored the sensor data, calculated the containment vessel leak rate, and displayed test results. The multiple computer configuration allowed continuous monitoring of the progress of the test independently of the data acquisition and analysis functions, and also provided improved overall system reliability by permitting immediate switching of computers if the equipment failed. 5 refs., 8 figs.

Hubbard, J.A.

1987-08-01

283

A stochastic model for estimating groundwater and contaminant discharges from fractured rock passive flux meter measurements  

NASA Astrophysics Data System (ADS)

Estimation of water and contaminant discharges is an important hydrological problem. Fractured rock aquifers are recognized as highly complex flow and transport systems, and the fractured rock passive flux meter (FRPFM) is a recently tested device to simultaneously measure cumulative water and contaminant mass fluxes in fractures intersecting an observation well (boring). Furthermore, the FRPFM is capable of indicating orientations and directions of flow in hydraulically active ("flowing") fractures. The present work develops a discharge estimator for when FRPFM measurements of fracture fluxes in the direction perpendicular to a transect (control plane) along one or more observation wells are available. In addition, estimation uncertainty in terms of a coefficient of variation is assessed based on a Monte Carlo approach under normalized conditions. Sources of uncertainty considered are spatially random fracture trace locations, random trace lengths, and orientations as well as variability of trace average fluxes (including smooth spatial trends), variability of local fluxes within traces, and flux measurement errors. Knowledge about the trace length distribution, which is commonly not available from borehole surveys, is not required for discharge estimation. However, it does affect the uncertainty assessment, and equations for upper uncertainty bounds are given as an alternative. In agreement with general statistical inference, it is found that discharge uncertainty decreases proportionally with the number of fluxes measured. Results are validated, and an example problem illustrates practical application and performance.

Acar, Özlem; Klammler, Harald; Hatfield, Kirk; Newman, Mark A.; Annable, Michael D.; Cho, Jaehyun; Parker, Beth L.; Cherry, John A.; Pehme, Pete; Quinn, Patryk; Kroeker, Ryan

2013-03-01

284

Geothermal Flux, Basal Melt Rates, and Subglacial Lakes in Central East Antarctica  

NASA Astrophysics Data System (ADS)

The lakes beneath the East Antarctic ice sheet represent a unique environment on Earth, entirely untouched by human interference. Life forms which survive in this cold, lightless, high pressure environment may resemble the life forms which survived through "snowball earth" and evolved into the life forms we know today (Kirchvink, 2000). Recent airborne radar surveys over Dome C and the South Pole regions allow us to assess where these lakes are most likely to exist and infer melting and freezing rates at base of the ice sheet. Lakes appear as strong, flat basal reflectors in airborne radar sounding data. In order to determine the absolute strength of the reflector it is important to accurately estimate signal loss due to absorption by the ice. As this quantity is temperature sensitive, especially in regions where liquid water is likely to exist, we have developed a one dimensional heat transfer model, incorporating surface temperature, accumulation, ice sheet thickness, and geothermal flux. Of the four quantities used for our temperature model, geothermal flux has usually proven to be the most difficult to asses, due to logistical difficulties. A technique developed by Fahnestock et al 2001 is showing promise for inferring geothermal flux, with airborne radar data. This technique assumes that internal reflectors, which result from varying electrical properties within the ice column, can be approximated as constant time horizons. Using ice core data from our study area, we can place dates upon these internal layers and develop an age versus depth relationship for the surveyed region, with margin of error of +- 50 m for each selected layer. Knowing this relationship allows us to infer the vertical strain response of the ice to the stress of vertical loading by snow accumulation. When ice is frozen to the bed the deeper ice will accommodate the increased stress of by deforming and thinning (Patterson 1994). This thinning of deeper layers occurs throughout most of our study area. However, analysis of dated internal layers over several bright, flat, "lake-like" reflectors reveals a very different age versus depth relationship in which deeper layers actually thicken with depth. This thickening of deep layers results from ice flowing in from the sides to accommodate significant liquid water production at the base of the ice sheet. This melt is occurring today and can be quantified. With our knowledge of melt rates we can begin to estimate inputs and assess hydrologic parameters for the subglacial lake systems of East Antarctica.

Carter, S. P.; Blankenship, D. D.; Morse, D. L.

2002-12-01

285

Nightside electron flux measurements at Mars by the Phobos-2 HARP instrument  

NASA Technical Reports Server (NTRS)

All the available nightside electron data obtained during circular orbits at Mars from the Phobos-2 Hyperbolic Retarded Potential Analyzer (HARP) instrument have been examined in detail and are summarized in this paper. An electron flux component with energies exceeding that of the unperturbed solar wind was observed inside the magnetosheath, indicating the presence of acceleration mechanism(s). The character of the electron fluxes measured in the magnetotail cannot be classified in any simple manner, however, there is a correlation between the electron fluxes measured well inside this region and the unperturbed solar wind ram pressure.

Shutte, N.; Gringauz, K.; Kiraly, P.; Kotova, G.; Nagy, A. F.; Rosenbauer, H.; Szego, K.; Verigin, M.

1995-01-01

286

Differential radiometry for measuring the net radiative flux in the earth`s atmosphere  

SciTech Connect

The Hemispheric Optimized NEt Radiometer (HONER) is very briefly described. HONER was developed to resolve technical issues impeding the accurate measurement of atmospheric radiative flux. HONER uses differential radiometry, chopping the signal from upwelling and downwelling fluxes onto a single AC detector system, allowing true optical differencing as well as measurements of the individual fluxes. Wavelength coverage encompasses ultraviolet to more than 50 micrometers. HONER has been used in a ground-based version and will be tested on the Perseus B Unmanned Aerospace Vehicle.

La Delfe, P.C.; Love, S.P.; Weber, P.G. [Los Alamos National Lab., NM (United States)

1996-11-01

287

Absolute Flux Measurements for IR Spectromicroscopy Michael C. Martina  

E-print Network

. of Chemistry, University of California, Berkeley, CA 94720 1. INTRODUCTION Measurements of the effects a self consistent picture which can be used to estimate the absolute exposure to cells and bacteria which was measured with a disappearing filament style optical pyrometer to have a brightness temperature of ~1343K

288

Application of an energy balance correction method for turbulent flux measurements based on buoyancy  

NASA Astrophysics Data System (ADS)

The energy imbalance in flux measurements between the atmosphere and the surface is a well-known problem, but unsolved due to the complexity of possible reasons and potential error sources. In order to provide unbiased budgets, however, eddy-covariance measurements of sensible and latent heat flux should be corrected according to the closure gap. Recent studies utilising turbulent flux data and LES models suggest that the transport of the missing turbulent flux is triggered by meso-scale circulations, not detected by eddy-covariance measurements within typical averaging intervals of 30 minutes. These motions on longer timescales are driven by buoyancy, suggesting that the missing turbulent flux is a missing buoyancy flux. Based on this assumption we present an energy balance closure correction method according to the buoyancy flux. The effects are compared with the results obtained by the commonly used correction according to the Bowen ratio (Twine et al., Agr. Forest Meteorol., 2000). We show that in general both correction methods could be applied to daytime fluxes and conditions with positive Bowen ratios. Finally the corrected turbulent fluxes are compared with different simulations of SVAT-type models for Tibetan grassland sites and a central European spruce forest site. The model performance with respect to the used data correction method is linked to the different mechanism of closing the energy balance within the model. Model validation requires energy balance closure correction in case the model relies on the energy balance equation. We conclude that mechanistic model development of turbulent flux parameterisations should recognize the recent hypotheses concerning the energy balance closure rather than fitting just to the uncorrected eddy-covariance data.

Babel, Wolfgang; Charuchittipan, Doojdao; Zhao, Peng; Biermann, Tobias; Gatzsche, Kathrin; Foken, Thomas

2014-05-01

289

Measurement of erosion rate by absorption spectroscopy in a Hall thruster  

SciTech Connect

The erosion rate of a Hall thruster was estimated with the objective of building a real-time erosion rate monitoring system using a 1 kW class anode layer type Hall thruster. This system aids the understanding of the tradeoff between lifetime and performance. To estimate the flux of the sputtered wall material, the number density of the sputtered iron was measured by laser absorption spectroscopy using an absorption line from ground atomic iron at 371.9935 nm. An ultravioletAl{sub x}In{sub y}Ga{sub (1-x-y)}N diode laser was used as the probe. The estimated number density of iron was 1.1x10{sup 16} m{sup -3}, which is reasonable when compared with that measured by duration erosion tests. The relation between estimated erosion rate and magnetic flux density also agreed with that measured by duration erosion tests.

Yamamoto, Naoji; Yokota, Shigeru; Matsui, Makoto; Komurasaki, Kimiya; Arakawa, Yoshihiro [Department of Advanced Energy Engineering Science, Kyushu University, 6-1 Kasuga-kouen, Kasuga, Fukuoka 816-8580 (Japan); Department of Aeronautics and Astronautics, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-8656 (Japan); Department of Advanced Energy, The University of Tokyo, Kashiwanoha 5-1-5, Kashiwa, Chiba 277-8562 (Japan); Department of Aeronautics and Astronautics, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-8656 (Japan)

2005-08-15

290

A comparison of two nitrification inhibitors used to measure nitrification rates in estuarine sediments  

USGS Publications Warehouse

Nitrification rates were measured using intact sediment cores from South San Francisco Bay and two different nitrification inhibitors: acetylene and methyl fluoride. Sediment oxygen consumption and ammonium and nitrate fluxes were also measured in these cores. Four experiments were conducted in the spring, and one in the fall of 1993. There was no significant difference in nitrification rates measured using the two inhibitors, which suggests that methyl fluoride can be used as an effective inhibitor of nitrification. Nitrification was positively correlated with sediment oxygen consumption and numbers of macrofauna. This suggests that bioturbation by macrofauna is an important control of nitrification rates. Irrigation by the tube-dwelling polychaete, Asychis elongata, which dominates the benthic biomass at this location, appears particularly important. Ammonium fluxes out of the sediment were greatest about one week after the spring bloom, while nitrification peaked about one month later.

Caffrey, J.M.; Miller, L.G.

1995-01-01

291

Comparison of measured and modeled radiation, heat and water vapor fluxes: FIFE pilot study  

NASA Technical Reports Server (NTRS)

The primary objectives of the 1985 study were to test the feasibility of using radio frequency receivers to collect data from automated weather stations and to evaluate the use of the data collected by the automated weather stations for modeling the fluxes of latent heat, sensible heat, and radiation over wheat. The model Cupid was used to calculate these fluxes which were compared with fluxes of these entities measured using micrometeorological techniques. The primary objectives of the 1986 study were to measure and model reflected and emitted radiation streams at a few locations within the First International Satellite Land-Surface Climatology Project Field Experiment (FIFE) site and to compare modeled and measured latent heat and sensible heat fluxes from the prairie vegetation.

Blad, Blaine L.; Verma, Shashi B.; Hubbard, Kenneth G.; Starks, Patrick; Hays, Cynthia; Norman, John M.; Waltershea, Elizabeth

1988-01-01

292

Flux measurements of CA II H and K emission. [from stellar chromospheres  

NASA Technical Reports Server (NTRS)

A four-channel photon-counting spectrophotometer (designated HKP-2) is described which is designed for measuring stellar chromospheric calcium emission. The HKP-2 is calibrated, and its performance and accuracy evaluated, by observing 63 of Wilson's (1968) program stars on the same nights with both the HKP-2 and a coude scanner designated HKP-1. The results of the observations are discussed in terms of the calibration of mean H-K flux indices, variations in individual stellar fluxes, the flux ratio for H and K, and the instrument color index. It is shown that the HKP-2 provides satisfactory performance in the measurement of stellar chromospheric emission in a manner closely analogous to the method of Wilson and that a single observation yields a color index as well as flux indices for H and K that can be calibrated and transferred unambiguously to Wilson's system of measurement.

Vaughan, A. H.; Preston, G. W.; Wilson, O. C.

1978-01-01

293

Ir Thermographic Measurements of Temperatures and Heat Fluxes in Hypersonic Plasma Flow  

NASA Astrophysics Data System (ADS)

The technological development achieved in instruments and methodology concerning both flights and ground hypersonic experiment (employed in space plane planning) goes towards an updating and a standardization of the heat flux technical measurements. In fact, the possibility to simulate high enthalpy flow relative to reentry condition by hypersonic arc-jet facility needs devoted methods to measure heat fluxes. Aim of this work is to develop an experimental numerical technique for the evaluation of heat fluxes over Thermal Protection System (TPS) by means of InfraRed (IR) thermographic temperature measurements and a new heat flux sensor (IR-HFS). We tackle the numerical validation of IR-HFS, apply the same one to the Hyflex nose cap model and compare the obtained results with others ones obtained by others methodology.

Cardone, G.; Tortora, G.; del Vecchio, A.

2005-02-01

294

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

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

295

Field intercomparison of two optical analyzers for CH4 eddy covariance flux measurements  

NASA Astrophysics Data System (ADS)

Fast response optical analyzers based on laser absorption spectroscopy are the preferred tools to measure field-scale mixing ratios and fluxes of a range of trace gases. Several state-of-the-art instruments have become commercially available and are gaining in popularity. This paper aims for a critical field evaluation and intercomparison of two compact, cryogen-free and fast response instruments: a quantum cascade laser based absorption spectrometer from Aerodyne Research, Inc., and an off-axis integrated cavity output spectrometer from Los Gatos Research, Inc. In this paper, both analyzers are characterized with respect to precision, accuracy, response time and also their sensitivity to water vapour. The instruments were tested in a field campaign to assess their behaviour under various meteorological conditions. The instrument's suitability for eddy covariance flux measurements was evaluated by applying an artificial flux of CH4 generated above a managed grassland with otherwise very low methane flux. This allowed an independent verification of the flux measurements accuracy, including the overall eddy covariance setup and data treatment. The retrieved fluxes were in good agreement with the known artificial emission flux, which is more than satisfactory, given that the analyzers were attached to separate sonic anemometers placed on individual eddy towers with different data acquisition systems but similar data treatment that are specific to the best practice used by the involved research teams.

Tuzson, B.; Hiller, R. V.; Zeyer, K.; Eugster, W.; Neftel, A.; Ammann, C.; Emmenegger, L.

2010-07-01

296

Flux correction for closed-path laser spectrometers without internal water vapor measurements  

NASA Astrophysics Data System (ADS)

Recently, instruments became available on the market that provide the possibility to perform eddy covariance flux measurements of CH4 and many other trace gases, including the traditional CO2 and H2O. Most of these instruments employ laser spectroscopy, where a cross-sensitivity to H2O is frequently observed leading to an increased dilution effect. Additionally, sorption processes at the intake tube walls modify and delay the observed H2O signal in closed-path systems more strongly than the signal of the sampled trace gas. Thereby, a phase shift between the trace gas and H2O fluctuations is introduced that dampens the H2O flux observed in the sampling cell. For instruments that do not provide direct H2O measurement in the sampling cell, transfer functions from externally measured H2O fluxes are needed to estimate the effect of H2O on trace gas flux measurements. The effects of cross-sensitivity and the damping are shown for an eddy covariance setup with the Fast Greenhouse Gas Analyzer (FGGA, Los Gatos Research Inc.) that measures CO2, CH4, and H2O fluxes. This instrument is technically identical with the Fast Methane Analyzer (FMA, Los Gatos Research Inc.) that does not measure H2O concentrations. Hence, we used measurements from a FGGA to derive a modified correction for the FMA accounting for dilution as well as phase shift effects in our instrumental setup. With our specific setup for eddy covariance flux measurements, the cross-sensitivity counteracts the damping effects, which compensate each other. Hence, the new correction only deviates very slightly from the traditional Webb, Pearman, and Leuning density correction, which is calculated from separate measurements of the atmospheric water vapor flux.

Hiller, R. V.; Zellweger, C.; Knohl, A.; Eugster, W.

2012-01-01

297

A Re-evaluation of Early Solar EUV and Soft X-ray Flux Measurements  

NASA Astrophysics Data System (ADS)

Measurements of the solar extreme ultraviolet and soft X-ray spectrum made at the (then) Air Force Geophysics Laboratory (AFGL) by a group under the direction of Hans Hinteregger were the basis for early estimates of the solar flux in the spectral range of 5 to 190 nm. Subsequent studies have indicated a discrepancy between the fluxes reported at the lower end of this spectral range and those required in modeling the Earth's ionosphere. We have examined a possible systematic source of error in the original calibration between 25 nm and 120 nm, the range over which the photoelectric yield of a tungsten surface was the basis for calibration. We find differences (never greater than 30 percent) between the adopted photoelectric yield values as a function of wavelength and measurements made elsewhere. Suggested corrections to EUV fluxes due to these deviations will be presented. To extend the analysis of AFGL results below 25 nm, but only for a period of intermediate solar activity, we use an OSO-5 spectrum between 2.5 and 40 nm having a spectral resolution of 0.05 nm. This spectrum was calibrated in-orbit using coronal density-insensitive emission line ratios and absolute flux measurements at 30.4 nm made independently by an instrument on OSO-4. These data provide independent measurements of solar fluxes in the 3-40 nm region that can be compared with AFGL observations and more recent measurements and flux models for moderate levels of solar activity.

Neupert, W. M.

2002-12-01

298

Comparison of Measured and Calculated Actinic Flux Density and Downward Uv Irradiance At The Ground  

Microsoft Academic Search

Ground-based measurements of spectral actinic flux density (300 - 660 nm wave- length) and spectral downward UV irradiance (300 - 325 nm) have been compared with the results obtained from radiative transfer calculations employing concurrent airborne vertical profile measurements of aerosol particle size distributions. The same comparison was made for measured and calculated photolysis frequencies of nitro- gen dioxide, J(NO2),

B. Früh; E. Eckstein; T. Trautmann; M. Wendisch; M. Fiebig; U. Feister

2002-01-01

299

Time and space resolved wall temperature and heat flux measurements during nucleate boiling with constant  

E-print Network

Time and space resolved wall temperature and heat flux measurements during nucleate boiling used to measure heat transfer data are often on the order of, or larger than, the bubble characteristic al. [4]. Yaddanapudi and Kim [5] measured local heat trans- fer underneath single bubbles nucleating

Kim, Jungho

300

Field intercomparison of four methane gas analyzers suitable for eddy covariance flux measurements  

NASA Astrophysics Data System (ADS)

Performances of four methane gas analyzers suitable for eddy covariance measurements are assessed. The assessment and comparison was performed by analyzing eddy covariance data obtained during summer 2010 (1 April to 26 October) at a pristine fen, Siikaneva, Southern Finland. High methane fluxes with pronounced seasonality have been measured at this fen. The four participating methane gas analyzers are commercially available closed-path units TGA-100A (Campbell Scientific Inc., USA), RMT-200 (Los Gatos Research, USA), G1301-f (Picarro Inc., USA) and an early prototype open-path unit Prototype-7700 (LI-COR Biosciences, USA). The RMT-200 functioned most reliably throughout the measurement campaign, during low and high flux periods. Methane fluxes from RMT-200 and G1301-f had the smallest random errors and the fluxes agree remarkably well throughout the measurement campaign. Cospectra and power spectra calculated from RMT-200 and G1301-f data agree well with corresponding temperature spectra during a high flux period. None of the gas analyzers showed statistically significant diurnal variation for methane flux. Prototype-7700 functioned only for a short period of time, over one month, in the beginning of the measurement campaign during low flux period, and thus, its overall accuracy and season-long performance were not assessed. The open-path gas analyzer is a practical choice for measurement sites in remote locations due to its low power demand, whereas for G1301-f methane measurements interference from water vapor is straightforward to correct since the instrument measures both gases simultaneously. In any case, if only the performance in this intercomparison is considered, RMT-200 performed the best and is the recommended choice if a new fast response methane gas analyzer is needed.

Peltola, O.; Mammarella, I.; Haapanala, S.; Burba, G.; Vesala, T.

2013-06-01

301

Direct rate measurements of eruption plumes at Augustine volcano: A problem of scaling and uncontrolled variables  

SciTech Connect

The March--April 1986 eruption of Augustine Volcano, Alaska, provided an opportunity to directly measure the flux of gas, aerosol, and ash particles during explosive eruption. Most previous direct measurements of volcanic emission rates are on plumes from fuming volcanoes or on very small eruption clouds. Direct measurements during explosive activity are needed to understand the scale relationships between passive degassing or small eruption plumes and highly explosive events. Conditions on April 3, 1986 were ideal: high winds, clear visibility, moderate activity. Three measurements were made: (1) an airborne correlation spectrometer (Cospec) provided mass flux rates of SO/sub 2/; (2) treated filter samples chemically characteized the plume and (3) a quartz crystal microcascade impactor provided particle size distribution. Atmospheric conditions on April 3 caused the development of a lee wave plume, which allowed us to constrain a model of plume dispersion leading to a forecast map of concentrations of SO/sub 2/ at greater distances from the vent.

Rose, W.I.; Heiken, G.; Wohletz, K.; Eppler, D.; Barr, S.; Miller, T.; Chuan, R.L.; Symonds, R.B.

1988-05-10

302

Graduation Rates: Whose Success Do They Measure?  

E-print Network

Engineering Health Sciences LiberalArts Leadership Studies/Public Administration Science Multidisciplinary... Semester 8-12... #12;The Lost Origins of Graduation Rates · Established in 1992 by the NCAA to monitor

Ward, Karen

303

Seasonality of Overstory and Understory Fluxes in a Semi-Arid Oak Savanna: What can be Learned from Comparing Measured and Modeled Fluxes?  

NASA Astrophysics Data System (ADS)

Semi-arid climates experience large seasonal and inter-annual variability in radiation and precipitation, creating natural conditions adequate to study how year-to-year changes affect atmosphere-biosphere fluxes. Especially, savanna ecosystems, that combine tree and below-canopy components, create a unique environment in which phenology dramatically changes between seasons. We used a 10-year flux database in order to define seasonal and interannual variability of climatic inputs and fluxes, and evaluate model capability to reproduce observed variability. This is based on the perception that model capability to construct the deviation, and not the average, is important in order to correctly predict ecosystem sensitivity to climate change. Our research site is a low density and low LAI (0.8) semi-arid savanna, located at Tonzi Ranch, Northern California. In this system, trees are active during the warm season (Mar - Oct), and grasses are active during the wet season (Dec - May). Measurements of carbon and water fluxes above and below the tree canopy using eddy covariance and supplementary measurements have been made since 2001. Fluxes were simulated using bio-meteorological process-oriented ecosystem models: BEPS and 3D-CAONAK. Models were partly capable of reproducing fluxes on daily scales (R2=0.66). We then compared model outputs for different ecosystem components and seasons, and found distinct seasons with high correlations while other seasons were purely represented. Comparison was much higher for ET than for GPP. The understory was better simulated than the overstory. CANOAK overestimated spring understory fluxes, probably due to the capability to directly calculated 3D radiative transfer. BEPS underestimated spring understory fluxes, following the pre-description of grass die-off. Both models underestimated peak spring overstory fluxes. During winter tree dormant, modeled fluxes were null, but occasional high fluxes of both ET and GPP were measured following precipitation events, likely produced by an adverse measurement effect. This analysis enabled to pinpoint specific areas where models break, and stress that model capability to reproduce fluxes vary among seasons and ecosystem components. The combined response was such, that comparison decreases when ecosystem fluxes were partitioned between overstory and understory fluxes. Model performance decreases with time scale; while performance was high for some seasons, models were less capable of reproducing the high variability in understory fluxes vs. the conservative overstory fluxes on annual scales. Discrepancies were not always a result of models' faults; comparison largely improved when measurements of overstory fluxes during precipitation events were excluded. Conclusions raised from this research enable to answer the critical question of the level and type of details needed in order to correctly predict ecosystem respond to environmental and climatic change.

Raz-Yaseef, N.; Sonnentag, O.; Kobayashi, H.; Chen, J. M.; Verfaillie, J. G.; Ma, S.; Baldocchi, D. D.

2011-12-01

304

How Well Do Social Ratings Actually Measure Corporate Social Responsibility?*  

E-print Network

How Well Do Social Ratings Actually Measure Corporate Social Responsibility?* Aaron K. Chatterji the implications of our findings for advocates and opponents of corporate social responsibility as well Ratings Actually Measure Corporate Social Responsibility? 1. Introduction An important element

Sadoulet, Elisabeth

305

Measurement of Hydraulic Properties During Constant Flux Infiltration: Field Average  

Microsoft Academic Search

tant for developing, testing, and applying water and solute transport theory. A method of measuring hydraulic conductivity (K ), soil matric fixed depth of soil by integration of the parametric water pressure head (c), and water content (u) relationships is presented. content-depth relationships presented by Broadbridge The procedure uses a series of multipurpose time domain reflectome- and White (1988) for

B. Si; R. G. Kachanoski; F. Zhang; G. W. Parkin; D. E. Elrick

306

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

PubMed

An intercomparison was made between eddy covariance flux measurements of ammonia by a quantum cascade laser absorption spectrometer (QCLAS) and a lead-salt tunable diode laser absorption spectrometer (TDLAS). The measurements took place in September 2004 and again in April 2005 over a managed grassland site in Southern Scotland, U.K. These were also compared with a flux estimate derived from an "Ammonia Measurement by ANnular Denuder with online Analysis" (AMANDA), using the aerodynamic gradient method (AGM). The concentration and flux measurements from the QCLAS correlated well with those of the TDLAS and the AGM systems when emissions were high, following slurry application to the field. Both the QCLAS and TDLAS, however, underestimated the flux when compared with the AMANDA system, by 64%. A flux loss of 41% due to chemical reaction of ammonia in the QCLAS (and 37% in the TDLAS) sample tube walls was identified and characterized using laboratory tests but did not fully accountforthis difference. Recognizing these uncertainties, the agreement between the systems was nevertheless very close (R2 = 0.95 between the QCLAS and the TDLAS; R2 = 0.84 between the QCLAS and the AMANDA) demonstrating the suitability of the laser absorption methods for quantifying the temporal dynamics of ammonia fluxes. PMID:18409634

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

2008-03-15

307

Measuring and modeling near surface reflected and emitted radiation fluxes at the FIFE site  

NASA Technical Reports Server (NTRS)

Research was conducted during the four Intensive Field Campaigns (IFC) of the FIFE project in 1987. The research was done on a tall grass prairie with specific measurement sites on and near the Konza Prairie in Kansas. Measurements were made to help meet the following objectives: determination of the variability in reflected and emitted radiation fluxes in selected spectral wavebands as a function of topography and vegetative community; development of techniques to account for slope and sun angle effects on the radiation fluxes; estimation of shortwave albedo and net radiation fluxes using the reflected and emitted spectral measurements described; estimation of leaf and canopy spectral properties from calculated normalized differences coupled with off-nadir measurements using inversion techniques; estimation of plant water status at several locations with indices utilizing plant temperature and other environmental parameters; and determination of relationships between estimated plant water status and measured soil water content. Results are discussed.

Blad, Blaine L.; Norman, John M.; Walter-Shea, Elizabeth; Starks, Patrick; Vining, Roel; Hays, Cynthia

1988-01-01

308

CO{sub 2} flux measurements across portions of the Dixie Valley geothermal system, Nevada  

SciTech Connect

A map of the CO{sub 2} flux across a newly formed area of plant kill in the NW part of the Dixie Valley geothermal system was constructed to monitor potential growth of a fumarole field. Flux measurements were recorded using a LI-COR infrared analyzer. Sample locations were restricted to areas within and near the dead zone. The data delineate two areas of high CO{sub 2} flux in different topographic settings. Older fumaroles along the Stillwater range front produce large volumes of CO{sub 2} at high temperatures. High CO{sub 2} flux values were also recorded at sites along a series of recently formed ground fractures at the base of the dead zone. The two areas are connected by a zone of partial plant kill and moderate flux on an alluvial fan. Results from this study indicate a close association between the range front fumaroles and the dead zone fractures. The goals of this study are to characterize recharge to the geothermal system, provide geochemical monitoring of reservoir fluids and to examine the temporal and spatial distribution of the CO{sub 2} flux in the dead zone. This paper reports the results of the initial CO{sub 2} flux measurements taken in October, 1997.

Bergfeld, D.; Goff, F. [Los Alamos National Lab., NM (United States). Earth and Environmental Sciences Div.; Janik, C.J. [Geological Survey, Menlo Park, CA (United States); Johnson, S.D. [Oxbow Power Services, Reno, NV (United States)

1998-12-31

309

Continuous measurement of methane flux over a larch forest using a relaxed eddy accumulation method  

NASA Astrophysics Data System (ADS)

We measured the methane flux of a forest canopy throughout a year using a relaxed eddy accumulation (REA) method. This sampling system was carefully validated against heat and CO2 fluxes measured by the eddy covariance method. Although the sampling system was robust, there were large uncertainties in the measured methane fluxes because of the limited precision of the methane gas analyzer. Based on the spectral characteristics of signals from the methane analyzer and the diurnal variations in the standard deviation of the vertical wind velocity, we found the daytime and nighttime precision of half-hourly methane flux measurements to be approximately 1.2 and 0.7 ?g CH4 m-2 s-1, respectively. Additional uncertainties caused by the dilution effect were estimated to affect the accuracy by as much as 0.21 ?g CH4 m-2 s-1 on a half-hourly basis. Diurnal and seasonal variations were observed in the measured fluxes. The biological emission from plant leaves was not observed in our studies, and thus could be negligible at the canopy-scale exchange. The annual methane sink was 835 ± 175 mg CH4 m-2 year-1 (8.35 kg CH4 ha-1 year-1), which was comparable to the flux range of 379-2,478 mg CH4 m-2 year-1 previously measured in other Japanese forest soils. This study indicated that the REA method could be a promising technique to measure canopy scale methane fluxes over forests, but further improvement of precision of the analyzer will be required.

Ueyama, Masahito; Hamotani, Ken; Nishimura, Wataru; Takahashi, Yoshiyuki; Saigusa, Nobuko; Ide, Reiko

2012-08-01

310

Improved Eddy Flux Measurements by Open-Path Gas Analyzer and Sonic Anemometer Co-Location  

NASA Astrophysics Data System (ADS)

A novel instrument design combines the sensing paths of an open-path gas analyzer and a 3-D sonic anemometer and integrates the sensors in a single aerodynamic body. Common electronics provide fast-response, synchronized measurements of wind vector, sonic temperature, CO2 and H2O densities, and atmospheric pressure. An instantaneous CO2 mixing ratio, relative to dry air, is computed in real time. The synergy of combined sensors offers an alternative to the traditional density-based flux calculation method historically used for standalone open-path analyzers. A simple method is described for a direct, in-situ, mixing-ratio-based flux calculation. The method consists of: (i) correcting sonically derived air temperature for humidity effects using instantaneous water vapor density and atmospheric pressure measurements, (ii) computing water vapor pressure based on water-vapor density and humidity-corrected sonic temperature, (iii) computing fast-response CO2 mixing ratio based on CO2 density, sonic temperature, water vapor, and atmospheric pressures, and (iv) computing CO2 flux from the covariance of the vertical wind speed and the CO2 mixing ratio. Since CO2 mixing ratio is a conserved quantity, the proposed method simplifies the calculations and eliminates the need for corrections in post-processing by accounting for temperature, water-vapor, and pressure-fluctuation effects on the CO2 density. A field experiment was conducted using the integrated sensor to verify performance of the mixing-ratio method and to quantify the differences with density-derived CO2 flux corrected for sensible and latent-heat fluxes. The pressure term of the density corrections was also included in the comparison. Results suggest that the integrated sensor with co-located sonic and gas sensing paths and the mixing-ratio-based method minimize or eliminate the following uncertainties in the measured CO2 flux: (i) correcting for frequency-response losses due to spatial separation of measured quantities, (ii) correcting sonically-derived, sensible-heat flux for humidity, (iii) correcting latent-heat flux for sensible-heat flux and water-vapor self-dilution, (iv) correcting CO2 flux for sensible- and latent-heat fluxes, (v) correcting CO2 flux for pressure-induced density fluctuations.

Bogoev, Ivan

2014-05-01

311

Can CO2 Turbulent Flux Be Measured by Lidar? A Preliminary Study  

NASA Technical Reports Server (NTRS)

The vertical profiling ofCO2 turbulent fluxes in the atmospheric boundary layer (ABL) is investigated using a coherent differential absorption lidar (CDIAL) operated nearby a tall tower in Wisconsin during June 2007. A CDIAL can perform simultaneous range-resolved CO2 DIAL and velocity measurements. The lidar eddy covariance technique is presented. The aims of the study are (i) an assessment of performance and current limitation of available CDIAL for CO2 turbulent fluxes and (ii) the derivation of instrument specifications to build a future CDIAL to perform accurate range-resolved CO2 fluxes. Experimental lidar CO2 mixing ratio and vertical velocity profiles are successfully compared with in situ sensors measurements. Time and space integral scales of turbulence in the ABL are addressed that result in limitation for time averaging and range accumulation. A first attempt to infer CO2 fluxes using an eddy covariance technique with currently available 2-mm CDIAL dataset is reported.

Gilbert, Fabien; Koch, Grady; Beyon, Jeffrey Y.; Hilton, Timothy W.; Davis, Kenneth J.; Andrews, Arlyn; Flamant, Pierre H.; Singh, Upendra N.

2011-01-01

312

Direct measurement of the oceanic carbon monoxide flux by eddy correlation  

NASA Astrophysics Data System (ADS)

This report presents results from a field trial of ship-based air-sea flux measurements of carbon monoxide (CO) by direct eddy correlation with an infrared-laser trace gas analyzer. The analyzer utilizes Off-Axis Integrated-Cavity-Output Spectroscopy (OA-ICOS) to achieve high selectivity for CO, rapid response (~2 Hz) and low noise. Over a two-day sea trial, peak daytime seawater CO concentrations were ~1.5 nM and wind speeds were consistently 10-12 m s-1. A clear diel cycle in CO flux with an early afternoon maximum was observed. An analysis of flux error suggests the effects of non-stationarity are important, and air-sea CO flux measurements are best performed in regions remote from continental pollution sources.

Blomquist, B. W.; Fairall, C. W.; Huebert, B. J.; Wilson, S. T.

2012-12-01

313

Direct measurement of the oceanic carbon monoxide flux by eddy correlation  

NASA Astrophysics Data System (ADS)

This report presents results from a field trial of ship-based air-sea flux measurements of carbon monoxide (CO) by direct eddy correlation using an infrared-laser trace gas analyzer. The analyzer utilizes Off-Axis Integrated-Cavity-Output Spectroscopy (OA-ICOS) to achieve high selectivity for CO, rapid response (10 Hz) and low noise. Over a two-day sea trial, peak daytime seawater CO concentrations were ~ 1.5 nM and wind speeds were consistently 10-12 m s-1. A clear diel cycle in CO flux with an early afternoon maximum was observed. An analysis of flux error sources suggests air-sea CO flux measurements are best performed in regions remote from continental pollution sources.

Blomquist, B. W.; Fairall, C. W.; Huebert, B. J.; Wilson, S. T.

2012-07-01

314

Aerosol properties derived from spectral actinic flux measurements  

Microsoft Academic Search

Measurement of aerosol properties is very important for understanding climate change. Aerosol optical properties influence solar radiation throughout the troposphere. According to the Working Group I report of the intergovernmental panel for climate change [IPCC, 2007], aerosols have a direct radiative forcing of - 0.5±0.4 W\\/m2 with a medium to low level of scientific understanding. This relatively large uncertainty indicates

H. Stark; K. S. Schmidt; P. Pilewskie; J. Cozic; A. G. Wollny; C. A. Brock; T. Baynard; D. Lack; D. D. Parrish; F. C. Fehsenfeld

2008-01-01

315

ESCAPE RATES FOR GIBBS MEASURES ANDREW FERGUSON AND MARK POLLICOTT  

E-print Network

ESCAPE RATES FOR GIBBS MEASURES ANDREW FERGUSON AND MARK POLLICOTT Abstract. In this paper we study the asymptotic behaviour of the escape rate of a Gibbs measure supported on a conformal repeller through a small Borel set A X the escape rate quantifies the asymptotic behaviour of the measure of the set of points x

Pollicott, Mark

316

Managerial Experience and the Measurement Equivalence of Performance Ratings  

Microsoft Academic Search

: Establishing the measurement equivalence of instruments is a prerequisite to making meaningful comparisons between individuals or within individuals over time. Whereas previous research has investigated the effects of rater characteristics on the measurement equivalence of performance ratings, the current study investigated a ratee characteristic—ratee job experience. Using confirmatory factor analysis and item response theory methods with replication, the measurement

Gary J. Greguras

2005-01-01

317

Field intercomparison of four methane gas analysers suitable for eddy covariance flux measurements  

NASA Astrophysics Data System (ADS)

Performances of four methane gas analyzers suitable for eddy covariance measurements are assessed. The assessment and comparison was performed by analyzing eddy covariance data obtained during summer 2010 (1 April to 26 October) at a pristine fen, Siikaneva, Southern Finland. High methane fluxes with pronounced seasonality have been measured at this fen. The four participating methane gas analyzers are commercially available closed-path units TGA-100A (Campbell Scientific Inc., USA), RMT-200 (Los Gatos Research, USA), G1301-f (Picarro Inc., USA) and an early prototype open-path unit Prototype-7700 (LI-COR Biosciences, USA). The RMT-200 functioned most reliably throughout the measurement campaign, during low and high flux periods. Methane fluxes from RMT-200 and G1301-f had the smallest random errors and the fluxes agree remarkably well throughout the measurement campaign. Cospectra and power spectra calculated from RMT-200 and G1301-f data agree well with corresponding temperature spectra during a high flux period. None of the gas analysers showed statistically significant diurnal variation for methane flux. Prototype-7700 functioned only for a short period of time, over one month, in the beginning of the measurement campaign during low flux period, and thus, its overall accuracy and long-term performance were not assessed. Prototype-7700 is a practical choice for measurement sites in remote locations due to its low power demand, however if only the performance in this intercomparison is considered, RMT-200 performed the best and is the recommended choice if a new fast response methane gas analyser is needed.

Peltola, O.; Mammarella, I.; Haapanala, S.; Burba, G.; Vesala, T.

2012-12-01

318

Urban greenhouse gas mole fraction in-situ measurements: Results from the Indianapolis Flux Experiment (INFLUX)  

NASA Astrophysics Data System (ADS)

The Indianapolis Flux Experiment (INFLUX) was designed to develop and evaluate methods for the measurement and modeling of greenhouse gas fluxes from urban environments. Determination of greenhouse gas fluxes and uncertainty bounds is essential for the evaluation of the effectiveness of mitigation strategies. The current INFLUX observation network includes twelve in-situ tower-based, continuous measurements of CO2, CO, and CH4, flask sampling of 14CO2 and other trace gases, and periodic aircraft sampling of greenhouse gases and meteorological conditions. Eddy covariance and radiative flux are measured at four of the tower sites, and a scanning Doppler lidar was installed in April 2013; both are used to quantify key boundary layer meteorological properties and evaluate model performance. Additionally, a total carbon column observing network (TCCON) column remote sensing station was deployed August - December 2012. The data from the towers, TCCON, and aircraft measurements are being used in an inverse-modeling approach to yield estimates of the urban area flux at 1 km2 resolution. Very high space/time resolution estimates of fossil fuel carbon emissions (Hestia project) offer state-of-the-art "bottom up" emissions estimates for the city and its surroundings. Here we present an overview of the progress from INFLUX, with a focus on tower-based results. With this high density of urban tower-based greenhouse gas measurements, we will quantify horizontal and vertical spatial patterns in atmospheric mole fractions of CO2, CO, and CH4 in Indianapolis. The consistency of the observed horizontal gradients with that expected based on differences in land-cover contributions according to footprint analysis will be evaluated. The ability to correctly model transport and mixing in the atmospheric boundary layer, responsible for carrying greenhouse gases from their source to the point of measurement, is essential. Thus we investigate differences between the modeled and observed sensible heat flux, latent heat flux, air temperature, and wind speed.

Miles, Natasha; Lauvaux, Thomas; Davis, Kenneth; Richardson, Scott; Sarmiento, Daniel; Sweeney, Colm; Karion, Anna; Hardesty, Robert Michael; Turnbull, Jocelyn; Iraci, Laura; Gurney, Kevin; Razlivanov, Igor; Obiminda Cambaliza, Maria; Shepson, Paul; Whetstone, James

2014-05-01

319

Measurements of Correlation-Enhanced Collision Rates  

E-print Network

modified by an equilibrium correlation factor g(), depending only on the correla- tion parameter e2 /a and temperature T, giving thermal ve- locity v (T/m)1/2, distance of closest approach b e2/T, and interparticle the nuclear reaction rate in dense correlated plasmas such as in giant planet interiors, brown dwarfs

California at San Diego, University of

320

Field intercomparison of two optical analyzers for CH4 eddy covariance flux measurements  

NASA Astrophysics Data System (ADS)

Fast response optical analyzers based on laser absorption spectroscopy are the preferred tools to measure field-scale mixing ratios and fluxes of a range of trace gases. Several state-of-the-art instruments have become commercially available and are gaining in popularity. This paper aims for a critical field evaluation and intercomparison of two compact, cryogen-free and fast response instruments: a quantum cascade laser based absorption spectrometer from Aerodyne Research, Inc., and an off-axis integrated cavity output spectrometer from Los Gatos Research, Inc. In this paper, both analyzers are characterized with respect to precision, accuracy, response time and also their sensitivity to water vapour. The instruments were tested in a field campaign to assess their behaviour under various meteorological conditions. The instrument's suitability for eddy covariance flux measurements was evaluated by applying an artificial flux of CH4 generated above a managed grassland with otherwise very low methane exchange. This allowed an independent verification of the flux measurements accuracy, including the overall eddy covariance setup and data treatment. The retrieved fluxes were in good agreement with the known artificial emission flux, which is more than satisfactory, given that the analyzers were attached to separate sonic anemometers placed on individual eddy towers with different data acquisition systems but similar data treatment that are specific to the best practice used by the involved research teams.

Tuzson, B.; Hiller, R. V.; Zeyer, K.; Eugster, W.; Neftel, A.; Ammann, C.; Emmenegger, L.

2010-11-01

321

Silicate weathering rates and solute fluxes along an erosional gradient, Middle Fork of the Feather River, CA  

NASA Astrophysics Data System (ADS)

Over geologic timescales, the weathering of silicate rocks has helped to maintain a mostly habitable planet, and it is clear that understanding rates of chemical weathering is key to accurately interpreting past changes in climate and seawater chemistry. However, the mechanisms that drive changes in weathering rates through time are incompletely described. By more closely examining the interplay between variables which control weathering, including fluid residence time, dissolution kinetics, and thermodynamic constraints, we would like to gain a more detailed understanding of these mechanisms. For example, the rate of mineral dissolution is controlled by the flux of water, the availability of fresh mineral surfaces and the proximity to thermodynamic equilibrium between the dissolving and secondary phases-once the soil or ground water reaches equilibrium, increasing mineral availability would not result in an increase in solute flux. Thus, the residence time of water and the departure from thermodynamic equilibrium are anticipated to be important controls on weathering fluxes. To gain a better understanding of the relative importance of these variables, we have studied the chemical and physical composition of solids and waters from three soil-mantled hillslope transects with different erosion rates within a tributary basin of the Middle Fork Feather River, CA. Overall, lower water contents are found in areas with higher erosion rates, and at the high erosion rate transect the solute compositions suggest that water is mostly bypassing the saprolite layer. In the solute chemistry, there is a clear trend of increasing concentration with depth for non-biologically cycled weathering components (Na, Si, etc). Other elements, such as Ca, Mg, K and Al show elevated concentrations in the surface horizons due to strong biological cycling. Calculated mineral saturation indices show that deeper waters are saturated with respect to K-feldspar and kaolinite, and slightly undersaturated with respect to albite. In general, the solute concentrations at the base of the soil profiles are similar across the three different erosion rates, indicating that the waters have reacted to a similar extent on all three transects despite widely varying moisture content, infiltration fluxes, steepness, grain size and clay content in the soils. Total chemical denudation rates (based on solute fluxes) vary across the transects according to water fluxes. This detailed study of hillslopes with different erosion rates suggests that thermodynamic equilibrium, water residence time and water flux are likely important controls on global weathering rates, even in active tectonic environments.

Kouba, C. M.; Rosen, V.; Maher, K.; Mayer, K.; Yoo, K.; Weinman, B. A.; Hurst, M. D.; Mudd, S. M.; Attal, M.

2011-12-01

322

Results of measuring the fluxes of solar energetic particles and methods of their interpretation  

NASA Astrophysics Data System (ADS)

Reliability and credibility of the results of measurements of the fluxes of protons and heavy ions of solar energetic particles, carried out with various experimental methods, are studied, as well as the methods of description of obtained data with various model functions of energy spectra. We analyze the results of measuring the fluxes of heavy ions of solar cosmic rays with the use of solid-state track detectors in the experiments Astro (April 1981, Salyut-6 spacecraft) and Platan-3 (1988-1989, Mir orbital station) and compare them with the results of experiments VLET and CRT made onboard the IMP-8 satellite. Special emphasis is made on the analysis of results obtained with instruments SIS and ULEIS ( ACE), and of results of measuring the fluxes of helium ions by the instrument EPEAD on GOES satellites. We also discuss the problem of fitting experimental data about SCR fluxes by different functions of energy (momentum, velocity) of particles. Such an approximation is a basis for interpreting the results of measurements. Numerous systematic errors are revealed that are typical for the results of measurements of the fluxes of SCR particles, performed with different instruments onboard Earth-orbiting satellites and other space vehicles.

Baranov, D. G.; Gagarin, Yu. F.; Dergachev, V. A.; Nymmik, R. A.; Panasyuk, M. I.

2011-12-01

323

Airborne Flux Measurements of BVOCs above Californian Oak Forests: Experimental Investigation of Surface and Entrainment Fluxes, OH Densities, and Damkohler Numbers  

E-print Network

layer above land, where typical length scales of 0.5­3 km were observed. Flux divergence of isoprene flux measurements of conserved tracers (e.g., heat, water) have demonstrated their use- fulness spectrometric methods have recently allowed investiga- tion of urban anthropogenic NMVOC emissions based

Cohen, Ronald C.

324

Ammonia fluxes for beech forest in the leaf fall transition period - measurements and modeling  

NASA Astrophysics Data System (ADS)

Deposition of atmospheric reactive nitrogen represents uncertainties for the prediction of future greenhouse gas exchange between land surfaces and the atmosphere. This is because the mechanisms describing nutritional effects are not well developed in climate and ecosystems models. Improving the understanding of biochemical feed-back mechanisms in the climate system and quantifying the magnitude of the NH3 flux in the biosphere-atmosphere system is therefore essential. In particular, more knowledge of the bi-directional ammonia (NH3) exchange between natural ecosystems and the atmosphere is needed. We investigated the NH3 exchange for deciduous forests in relation to leaf fall by studying the atmospheric NH3 fluxes throughout a 25 days period during autumn 2010 (21 October - 14 November) for the Danish beech (Fagus sylvatica) forest, Lille Bøgeskov. Vegetation status was observed using plant area index (PAI) and leaf area index (LAI). The atmospheric NH3 fluxes were measured using the relaxed eddy accumulation (REA) method and compared to NH3 denuder measurements. Model calculations were obtained using the Danish Ammonia MOdelling System (DAMOS). We found that 57.7% of the fluxes measured showed emission and 19.5% deposition. The mean NH3 flux was 0.087±0.19 ?g NH3-N m-2 s-1. Measurements indicate a clear tendency of the flux going from negative (deposition) to positive (emission) fluxes of up to 0.96±0.40 ?g NH3-N m-2 s-1 throughout the measurement period. In the leaf fall period (23 October - 8 November) the measured atmospheric NH3 concentration was increasing in relation to the increasing forest NH3 flux. The mean NH3 concentration was well simulated in DAMOS before leaf fall, but was underestimated following leaf fall. The results indicate that there is a missing contribution to atmospheric NH3 concentration from vegetative surfaces related to leaf fall of a relatively large magnitude in the model. This points to the need for representing forest leaf fall and associated NH3 emissions in chemical transport models when the focus is N-deposition to forest ecosystems. Despite the large uncertainties associated with the results obtained in this study due to the assessment techniques as well as the limited dataset, the results must be considered as a good start for a better understanding of the processes related to natural emissions of NH3 and for quantifying the NH3 emission flux and the total biosphere-atmosphere net flux.

Hansen, K.; Sørensen, L.; Hertel, O.; Geels, C.; Skjøth, C. A.; Jensen, B.; Boegh, E.

2012-12-01

325

Vadose Zone Infiltration Rates from Sr isotope Measurements  

NASA Astrophysics Data System (ADS)

Predicting infiltration rates and recharge through the vadose zone in arid regions is difficult and hence developing methods for the measurement of infiltration rates is important. We have been investigating the use of Sr isotope measurements for determining infiltration at the 200 Area plateau on the Hanford reservation in central Washington. In this context, infiltration affects the transport of contaminants to the water table as well as recharge of the groundwater system. Using Sr isotopes for this purpose requires drill core and water samples from the vadose zone, although leaches of the cores can substitute for water samples. Complementary information, including some constraints on regional recharge, can also be obtained using water samples from groundwater monitoring wells. The VZ method is based on the fact that the Sr isotope ratio of soil water just below the surface is often set by dissolution of aeolian material including carbonate, and this ratio is different from the average value in the deeper underlying vadose zone rock matrix. As water infiltrates, the Sr isotopic composition of the water changes toward the rock values as a result of Sr released from the rocks by weathering reactions. The rate of change with depth of the Sr isotope ratio of the vadose zone water is a function ultimately of q/R; the ratio of the infiltration flux (q) to the bulk rock weathering rate (R). Where it is possible to evaluate R, q can be estimated. As data accumulate it may be possible to improve the calibration of the method. At Hanford the vadose zone rock material is mostly unconsolidated sand, silt, and gravel of broadly granitic composition, which constitute the Hanford and Ringold formations. Annual precipitation is about 160 mm/yr. Drilling and coring of a ca. 70m hole to the water table in 1999 as part of the Hanford groundwater monitoring program, in a relatively undisturbed area of the site, allowed us to generate a unique Sr isotope data set. The Sr isotope ratios of distilled water rinses of the subsurface sediments change systematically with depth and correspond to q/R of 10 to 20 km. Using an estimate for R from studies of soil chronosequences we obtain a value for q of about 20 mm/yr. Depending on the retardation of Sr in the system, this value may represent an average over the past few hundred years or as much as the past few thousand years. The deduced value is likely to be somewhat high, but it compares reasonably well to qualitative estimates based on O and D isotopes. It does not agree with chloride mass balance estimates from nearby sites, which are 1000x lower.

Maher, K.; Maher, K.; DePaolo, D. J.; DePaolo, D. J.; Conrad, M.

2001-12-01

326

Rates of insulin secretion in INS-1 cells are enhanced by coupling to anaplerosis and Kreb's cycle flux independent of ATP synthesis  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer We studied media effects on mechanisms of insulin secretion of INS-1 cells. Black-Right-Pointing-Pointer Insulin secretion was higher in DMEM than KRB despite identical ATP synthesis rates. Black-Right-Pointing-Pointer Insulin secretion rates correlated with rates of anaplerosis and TCA cycle. Black-Right-Pointing-Pointer Mitochondria metabolism and substrate cycles augment secretion signal of ATP. -- Abstract: Mechanistic models of glucose stimulated insulin secretion (GSIS) established in minimal media in vitro, may not accurately describe the complexity of coupling metabolism with insulin secretion that occurs in vivo. As a first approximation, we have evaluated metabolic pathways in a typical growth media, DMEM as a surrogate in vivo medium, for comparison to metabolic fluxes observed under the typical experimental conditions using the simple salt-buffer of KRB. Changes in metabolism in response to glucose and amino acids and coupling to insulin secretion were measured in INS-1 832/13 cells. Media effects on mitochondrial function and the coupling efficiency of oxidative phosphorylation were determined by fluorometrically measured oxygen consumption rates (OCRs) combined with {sup 31}P NMR measured rates of ATP synthesis. Substrate preferences and pathways into the TCA cycle, and the synthesis of mitochondrial 2nd messengers by anaplerosis were determined by {sup 13}C NMR isotopomer analysis of the fate of [U-{sup 13}C] glucose metabolism. Despite similar incremental increases in insulin secretion, the changes of OCR in response to increasing glucose from 2.5 to 15 mM were blunted in DMEM relative to KRB. Basal and stimulated rates of insulin secretion rates were consistently higher in DMEM, while ATP synthesis rates were identical in both DMEM and KRB, suggesting greater mitochondrial uncoupling in DMEM. The relative rates of anaplerosis, and hence synthesis and export of 2nd messengers from the mitochondria were found to be similar in DMEM to those in KRB. And, the correlation of total PC flux with insulin secretion rates in DMEM was found to be congruous with the correlation in KRB. Together, these results suggest that signaling mechanisms associated with both TCA cycle flux and with anaplerotic flux, but not ATP production, may be responsible for the enhanced rates of insulin secretion in more complex, and physiologically-relevant media.

Cline, Gary W., E-mail: gary.cline@yale.edu [The Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06520 (United States); Department of Surgery, University of Minnesota-Twin Cities, Minneapolis, MN 55455 (United States); Pongratz, Rebecca L.; Zhao, Xiaojian [The Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06520 (United States)] [The Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06520 (United States); Papas, Klearchos K. [Department of Surgery, University of Minnesota-Twin Cities, Minneapolis, MN 55455 (United States)] [Department of Surgery, University of Minnesota-Twin Cities, Minneapolis, MN 55455 (United States)

2011-11-11

327

Measurement of surface radiation fluxes and cloud optical properties during the 1994 Arctic Ocean Section  

NASA Astrophysics Data System (ADS)

During a voyage to the north pole from Alaska by the icebreakers USCGC Polar Sea and Canadian CGC Louis S. St.-Laurent (the 1994 Arctic Ocean Section, July 24 to September 3) an atmospheric radiation and remote sensing experiment measured downwelling shortwave and longwave radiation reaching the sea ice surface. The experiment included a Fourier transform infrared (FTIR) spectroradiometer which measured zenith radiance at 1 cm-1 resolution in the middle infrared wavelength range 5-20 ?m, an Eppley pyranometer measuring most of the downwelling shortwave flux (0.28-2.80 ?m), an Eppley pyranometer measuring the downwelling near-infrared flux (0.78-2.80 ?m), and an Eppley pyrgeometer measuring the downwelling longwave flux. In conjunction with a discrete-ordinates radiative transfer model, the FTIR emission spectra are used to estimate 8-12 ?m cloud emissivity and effective radius of the cloud droplet size distribution. The broadband shortwave flux measurements are used to estimate shortwave cloud scattering optical depth. Most of the FTIR emission spectra recorded under overcast skies are consistent with cloud effective radius in the range 10-12 ?m, but 27% of the spectra are more consistent with the range 4-6 ?m, suggesting an occasional continental aerosol influence to Arctic cloud microphysics. The average daily shortwave cloud-scattering optical depth ranged from 2 to 46, which is similar to a range inferred from radiometer data recorded at Barrow, Alaska, during the same season. The downwelling shortwave flux measurements and estimates of net surface flux are generally consistent with a four-decade Russian climatology but also suggest that the frequency of cloud cover sampled during the 1994 Arctic Ocean Section was somewhat larger than the climatological average. These radiation measurement data from the 1994 Arctic Ocean Section should be useful for examining the treatment of atmospheric radiation and surface energy input in Arctic climate model simulations.

Lubin, Dan; Simpson, A. Sabrina

1997-02-01

328

Measurement of turbulent water vapor fluxes using a lightweight unmanned aerial vehicle system  

NASA Astrophysics Data System (ADS)

We present here the first application of a lightweight unmanned aerial vehicle (UAV) system designed to measure turbulent properties and vertical latent heat fluxes (?E). Such measurements are crucial to improve our understanding of linkages between surface moisture supply and boundary layer clouds and phenomena such as atmospheric rivers. The application of UAVs allows for measurements on spatial scales complimentary to satellite, aircraft, and tower derived fluxes. Key system components are: a turbulent gust probe; a fast response water vapor sensor; an inertial navigation system (INS) coupled to global positioning system (GPS); and a 100 Hz data logging system. We present measurements made in the continental boundary layer at the National Aeronautics and Space Administration (NASA) Dryden Research Flight Facility located in the Mojave Desert. Two flights consisting of several horizontal straight flux run legs up to ten kilometers in length and between 330 and 930 m above ground level (m a.g.l.) are compared to measurement from a surface tower. Surface measured ?E ranged from -53 W m-2 to 41 W m-2, and the application of a Butterworth High Pass Filter (HPF) to the datasets improved agreement to within +/-12 W m-2 for 86% of flux runs, by removing improperly sampled low frequency flux contributions. This result, along with power and co-spectral comparisons and consideration of the differing spatial scales indicates the system is able to resolve vertical fluxes for the measurement conditions encountered. Challenges remain, and the outcome of these measurements will be used to inform future sampling strategies and further system development.

Thomas, R. M.; Lehmann, K.; Nguyen, H.; Jackson, D. L.; Wolfe, D.; Ramanathan, V.

2012-01-01

329

Feed rate measuring method and system  

DOEpatents

A system and method are provided for establishing the feed rate of a workpiece along a feed path with respect to a machine device. First and second sensors each having first and second sensing electrodes which are electrically isolated from the workpiece are positioned above, and in proximity to the desired surfaces of the workpiece along a feed path. An electric field is developed between the first and second sensing electrodes of each sensor and capacitance signals are developed which are indicative of the contour of the workpiece. First and second image signals representative of the contour of the workpiece along the feed path are developed by an image processor. The time delay between corresponding portions of the first and second image signals are then used to determine the feed rate based upon the separation of the first and second sensors and the amount of time between corresponding portions of the first and second image signals. 18 figs.

Novak, J.L.; Wiczer, J.J.

1995-12-05

330

Feed rate measuring method and system  

DOEpatents

A system and method are provided for establishing the feed rate of a workpiece along a feed path with respect to a machine device. First and second sensors each having first and second sensing electrodes which are electrically isolated from the workpiece are positioned above, and in proximity to the desired surfaces of the workpiece along a feed path. An electric field is developed between the first and second sensing electrodes of each sensor and capacitance signals are developed which are indicative of the contour of the workpiece. First and second image signals representative of the contour of the workpiece along the feed path are developed by an image processor. The time delay between corresponding portions of the first and second image signals are then used to determine the feed rate based upon the separation of the first and second sensors and the amount of time between corresponding portions of the first and second image signals.

Novak, James L. (Albuquerque, NM); Wiczer, James J. (Albuquerque, NM)

1995-01-01

331

Measurements of ammonia concentrations, fluxes and dry deposition velocities to a spruce forest 1991–1995  

Microsoft Academic Search

The dry deposition velocities and fluxes of ammonia have been estimated from measurements of the vertical gradient of ammonia and micrometeorology above a spruce forest in western Jutland, Denmark. Measurements have been made in seven periods, each lasting about one week and covering all seasons and different meteorological situations. Different deposition characteristics were observed, depending on the ammonia concentration and

Helle Vibeke Andersen; Mads F. Hovmand; Poul Hummelshøj; Niels Otto Jensen

1999-01-01

332

Measurement of 2D vector magnetic properties under the distorted flux density conditions  

Microsoft Academic Search

Under distorted flux density condition, it is very difficult to evaluate the field intensity, because there is no criterion for the measurement. In the linear approximation, the measured field intensity waveform (MFI) is compared with the linear synthesis of field intensity waveform (LSFI) in each frequency, and it is shown that they are not in good agreement at higher induction.

Shinya Urata; Takashi Todaka; Masato Enokizono; Yoshitaka Maeda; Hiroyasu Shimoji

2006-01-01

333

Airborne Measurements of Methane Fluxes over Mid-Latitude and Sub-Arctic Wetlands  

NASA Astrophysics Data System (ADS)

For a quantification of the natural GHG budget of the atmosphere the emission of methane from the vast arctic wetlands need to be assessed accurately. The conventional methods of flux measurements made by closed chambers and eddy towers need to be upscaled, introducing a potentially large source of uncertainty, due to the heterogeneity of the emitting sources at the surface. In order to obtain a large area coverage and thus a higher spacial representativeness we performed airborne measurements of methane fluxes over mid-latitude and sub-arctic wetlands, for flight legs of tens of kilometres length. We installed a fast trace gas analyser, a Los Gatos RMT200, in the research aircraft Polar 5, together with the noseboom mounted turbulence sensor package. Measurement flights have been carried out in June 2011 over wetlands in Germany and in northern Finland in a convectively mixed boundary layer. Reference data have been optained at the surface by tower mounted eddy correlation measurements. A spectral analysis of the first measurements shows that the system is well suitable to measure the vertical flux of methane from natural surfaces transported by the dominating eddies in the convective boundary layer. Our flux measurements compare well to those obtained at the surface. On the high-frequency end of the spectrum the measurement accuracy is not sufficient to resolve the inertial subrange.

Hartmann, J.; Sachs, T.

2012-04-01

334

Flux measurements of alkali atoms diffusing via multiple surface scattering in a silanated glass tube  

Microsoft Academic Search

Alkali atoms that are diffusing away from a source via multiple surface scattering in a nonstick coated glass tube are monitored by laser fluorescence. Densities are measured by fluorescence intensity and weak-field absorption, and small asymmetries in the line shape provide a measurement of the flux. Average velocities as small as 0.3% of the thermal velocity can be resolved using

Michael A Waxman; Tyler Morgus; Alan D Streater

2002-01-01

335

MEASUREMENTS OF MOLTEN STEEL/FLUX INTERFACE PHENOMENA IN THIN SLAB CASTING  

E-print Network

MEASUREMENTS OF MOLTEN STEEL/FLUX INTERFACE PHENOMENA IN THIN SLAB CASTING By Joseph W. Shaver B trials investigating meniscus behavior and defects in thin-slab casting were conducted at Nucor Steel of the steel. Metal level and meniscus measurements were made during ordinary casting operation. Nailboards

Thomas, Brian G.

336

DESIGN AND IMPLEMENTATION OF A TRANSPORTABLE SYSTEM FOR DIRECT MEASUREMENT OF DRY DEPOSITION FLUXES  

EPA Science Inventory

Dry deposition of air pollutants is expensive and difficult to measure. icks et al. (1985) proposed the dry deposition inferential model determines dry deposition fluxes as the product of a measured concentration and a modeled deposition velocity. eposition velocity is calculated...

337

Shortwave Flux from Satellite-Measured Radiance: A Theoretical Study over Marine Boundary Layer Clouds  

Microsoft Academic Search

Earth radiation budget measurements, important to climate monitoring and to validating climate models, require that radiances measured by satellite instruments be converted to hemispherical flux. This paper examines that problem theoretically, using inhomogeneous cloud models constructed from Landsat scenes of marine boundary layer clouds. The spherical harmonics discrete ordinates method (SHDOM) code is applied to the model scenes to compute

L. H. Chambers; B. A. Wielicki; N. G. Loeb

2001-01-01

338

Estimating Parameters of a Forest Ecosystem C Model Using Multiple Stock and Flux Measurements as Joint Constraints  

NASA Astrophysics Data System (ADS)

We report on efforts to constrain a modified version of the DALEC model using data from the spruce-dominated Howland Forest AmeriFlux site (central Maine, USA). Eight years of data, including continuous eddy covariance measurements of forest-atmosphere CO2 fluxes (NEE, net ecosystem exchange), periodic chamber measurements of soil respiratory fluxes, and ancillary ecological measurements -leaf area index, litterfall, and woody biomass increment-were used to calibrate (1997-2000 data) and test (2001-2004 data) the model. We placed special emphasis on characterizing the uncertainties in each data stream. Data-model fusion was conducted as a series of experiments in which different data were used in combination with the ecosystem-scale CO2 fluxes to constrain the model parameters. Parameters were optimized using a Monte Carlo approach based on the Metropolis algorithm, which permitted us to characterize the joint distribution of the 12 model parameters conditional on the data and uncertainties. From the posterior distributions of the parameters, we characterized the uncertainty in model predictions. The degree to which the different data streams successfully constrained the model was highly variable and depended on the parameter and pool or flux in question. Incorporation of all constraints resulted in the greatest reduction in both parameter and model prediction uncertainty. Of the additional data used as constraints, woody biomass increment measurements were most effective in reducing uncertainties in multiple parameters. Leaf area index and litterfall measurements provided highly specific information that reduced uncertainties in the amount of foliage and the rate at which it turns over, but did not contribute to substantial reductions in other model states or parameters. Even when all constraints were used simultaneously, initial values of the wood, soil organic matter, fine roots, and litter C pools were poorly constrained, and large uncertainties remained in the partitioning of ecosystem respiration to autotrophic and heterotrophic components. Although the observations and model predictions were consistent (within estimated uncertainties), we were not able to reproduce the patterns of interannual variation as seen, for example, in annual estimates of net C sequestration derived from gap-filled eddy covariance measurements. However, an advantage of using multiple constraints was that the test period model predictions were greatly improved, compared to when only the eddy covariance measurements were used to constrain the model (e.g., tower measurements: NEE mean, -200 g C m-2 over the 4 year period; model, constrained only with fluxes: NEE mean, -75 g C m-2; model, constrained with all data: NEE mean, -190 g C m-2).

Richardson, A. D.; Williams, M.; Moore, D. J.; Hollinger, D. Y.; Davidson, E. A.; Dail, B.; Scott, N. A.

2009-12-01

339

A prolegomena to precision measurements of reactor neutrino flux  

NASA Astrophysics Data System (ADS)

The standard model of particle physics has been very successful in describing the Strong, Weak and Electromagnetic interactions of fundamental particles over a wide range of energies. However, recent experimental evidence of lepton flavor violation has been shown in the oscillation of massive neutrinos. These observations are a strong indication that the standard model treatment for the weak interactions of fundamental particles is incomplete. We can incorporate these new observations into our existing framework by generalizing the standard model: allowing neutrinos to acquire mass. The Daya Bay experiment plans to determine the last undetermined mixing angle in the leptonic mixing matrix, theta13, by studying the anomalous disappearance of reactor antineutrinos at baselines up to 2 km. The sensitivity of the Daya Bay experiment to low energy reactor neutrinos is possible because of a newly developed Gadolinium loaded liquid scintillator (GdLS), which acts as both a target and detection medium for neutrino induced inverse beta decays. The research and development informing the experimental design are discussed, with particular emphasis on the measured optical properties of GdLS. These results are necessary for understanding the signal and background event reconstruction when the experiment comes online in 2012. The projected sensitivity to theta13 and the status of detector construction as of March 2010 are discussed.

Goett, Johnny

340

Heart Rate Variability Measures and Models  

E-print Network

We focus on various measures of the fluctuations of the sequence of intervals between beats of the human heart, and how such fluctuations can be used to assess the presence or likelihood of cardiovascular disease. We examine sixteen such measures and their suitability for correctly classifying heartbeat records of various lengths as normal or revealing the presence of cardiac dysfunction, particularly congestive heart failure. Using receiver-operating-characteristic analysis we demonstrate that scale-dependent measures prove substantially superior to scale-independent ones. The wavelet-transform standard deviation at a scale near 32 heartbeat intervals, and its spectral counterpart near 1/32 cycles/interval, turn out to provide reliable results using heartbeat records just minutes long. We further establish for all subjects that the human heartbeat has an underlying stochastic origin rather than arising from a chaotic attractor. Finally, we develop a mathematical point process that emulates the human heartbea...

Teich, M C; Jost, B M; Vibe-Rheymer, K; Heneghan, C; Teich, Malvin C.; Lowen, Steven B.; Jost, Bradley M.; Vibe-Rheymer, Karin; Heneghan, Conor

2001-01-01

341

A literature overview of micrometeorological CH4 and N2O flux measurements in terrestrial ecosystems  

NASA Astrophysics Data System (ADS)

The use of micrometeorological (MM) techniques for methane (CH4) and nitrous oxide (N2O) flux measurements in terrestrial ecosystems is increasing and a general outline which summarizes key results is needed. This work provides an overview of the current status of global flux measurements of CH4 and N2O by MM techniques in terrestrial ecosystems. Published studies were grouped into four main terrestrial land cover categories and the reported flux ranges, the consistency of different MM approaches over the same ecosystem types, the variability of the MM technique performances as regards the flux detection limit and environmental conditions, were analysed. Furthermore, the issue of the comparability between MM and soil chambers measurements was evaluated. The existing dataset, although temporally and spatially limited, shows that CH4 and N2O fluxes are extremely variable in both time and space with mean fluxes spanning within interquartile ranges of 1.33 ÷ 5.45, 11.02 ÷ 68.48, 5.38 ÷ 29.28, 13.87·103 ÷ 47.60·103 nmol CH4 m-2 s-1 in forest, wetlands, croplands and artificial lands respectively, and of 0.09 ÷ 0.42, 0.24 ÷ 1.47, 9.13 ÷ 20.89 nmol N2O m-2 s-1 in forest, croplands and artificial lands (no published works were found for wetlands). When environmental conditions were comparable, a general agreement of flux ranges was found within each ecosystem type, in particular when estimates were based on accurate footprint analysis. Exceptions were mainly related to site-specific aspects or to particular measurement periods. Not all the measurement set-ups were suitable for all ecosystems, environmental conditions, turbulence characteristics and flux intensity, however the latest technological improvements make the detection of fluxes feasible virtually in all ecosystems. MM studies of CH4 and N2O fluxes were unevenly distributed around the globe and, in particular, were lacking in sensitive areas like Africa, South America and Central Asia.

Nicolini, Giacomo; Castaldi, Simona; Fratini, Gerardo; Valentini, Riccardo

2013-12-01

342

Eddy-Covariance Flux Measurements in the Complex Terrain of an Alpine Valley in Switzerland  

NASA Astrophysics Data System (ADS)

We measured the surface energy budget of an Alpine grassland in highly complex terrain to explore possibilities and limitations for application of the eddy-covariance technique, also for CO2 flux measurements, at such non-ideal locations. This paper focuses on the influence of complex terrain on the turbulent energy measurements of a characteristic high Alpine grassland on Crap Alv (Alp Weissenstein) in the Swiss Alps during the growing season 2006. Measurements were carried out on a topographic terrace with a slope of 25? inclination. Flux data quality is assessed via the closure of the energy budget and the quality flag method used within the CarboEurope project. During 93% of the time the wind direction was along the main valley axis (43% upvalley and 50% downvalley directions). During the transition times of the typical twice daily wind direction changes in a mountain valley the fraction of high and good quality flux data reached a minimum of ?50%, whereas during the early afternoon ?70% of all records yielded good to highest quality (CarboEurope flags 0 and 1). The overall energy budget closure was 74 ± 2%. An angular correction for the shortwave energy input to the slope improved the energy budget closure slightly to 82 ± 2% for afternoon conditions. In the daily total, the measured turbulent energy fluxes are only underestimated by around 8% of net radiation. In summary, our results suggest that it is possible to yield realistic energy flux measurements under such conditions. We thus argue that the Crap Alv site and similar topographically complex locations with short-statured vegetation should be well suited also for CO2 flux measurements.

Hiller, Rebecca; Zeeman, Matthias J.; Eugster, Werner

2008-06-01

343

Progressive addition lenses—measurements and ratings  

Microsoft Academic Search

BackgroundThis study is a followup to a previous study in which the optics of several progressive addition lens (PALs) designs were measured and analyzed. The objective was to provide information about various PAL designs to enable eye care practitioners to select designs based on the particular viewing requirements of the patient.

Jim Sheedy; Raymond F. Hardy; John R. Hayes

2006-01-01

344

Airborne flux measurements of trace species in an Arctic boundary layer  

NASA Technical Reports Server (NTRS)

In situ airborne flux values for O3, CO, an CH4 over selected wetlands of Alaska are reported, and airborne CH4 flux measurements are presented for the first time. The source/sink distribution over the Yukon-Kuskokwim Delta (YKD) is qualitatively correlated with surface vegetation type. The CH4 source strength over the YKD ranged from 25 to 85 mg/sq m/d. A spatially averaged, seasonally adjusted source strength of 51 mg/sq m/d was established for the YKD. Indirect CH4 flux estimates obtained over the Alaskan North Slope indicate a much lower source strength. The global CH4 emission from tundra are estimated to be 44 Tg/a at an upper limit. Airborne CO flux measurements over the YKD indicate low negative flux values over the coastal areas, while some positive fluxes were observed in the inland sparsely forested regions. An inspection of the cospectrum of CO with vertical velocity for sample runs in coastal areas indicate the possibility of in situ photochemical destruction/production of CO.

Ritter, John A.; Barrick, John D. W.; Sachse, Glen W.; Gregory, Gerald L.; Woerner, Mary A.; Watson, Catherine E.; Hill, Gerald F.; Collins, James E., Jr.

1992-01-01

345

Leak rate measurements and detection systems  

SciTech Connect

A research program is under way to evaluate and develop improve leak detection systems. The primary focus of the work has been on acoustic emission detection of leaks. Leaks from artificial flaws, laboratory-generated IGSCCs and thermal fatigue cracks, and field-induced intergranular stress corrosion cracks (IGSCCs) from reactor piping have been examined. The effects of pressure, temperature, and leak rate and geometry on the acoustic signature are under study. The use of cross-correlation techniques for leak location and pattern recognition and autocorrelation for source discrimination is also being considered.

Kupperman, D.; Shack, W.J.; Claytor, T.

1983-10-01

346

In situ determination and laboratory measurements of Cu fluxes in two dam sediments using DGT  

NASA Astrophysics Data System (ADS)

The technique of diffusion gradients in thin films (DGT) accumulates labile metals on a chelex resin after their diffusive transport through a hydrogel. DGT is capable to measure in-situ fluxes of metals in sediments, in response to the perturbation induced. Porewater concentration is lowered, but depending on the sediment, metal sorbed to particulate matter can either exchange with solution to maintain its concentration or not. We measured Cu fluxes in the sediments of two dams, in the field with an on-site DGT insertion technique and at the laboratory. Some experiments were also performed to measure directly fluxes in their porewaters after extraction. Results of experiments and calculations using the DIFS model allowed us to discriminate between both aquatic systems in their ability to sustain metal concentration in porewaters. The possibility of resupply was demonstrated for one sediment but particulate metal in the other sediment appeared tightly bound and not subject to release.

Roulier, J.-L.; Motte, B.

2003-05-01

347

Rotation Rate of Saturn's Magnetosphere using CAPS Plasma Measurements  

NASA Astrophysics Data System (ADS)

the rotation rate of Saturn's magnetosphere using a 3D velocity moment technique being developed at Goddard which is similar to the 2D version used by Sittler et al. (2005) [1] for SOI and similar to that used by Thomsen et al. (2010). This technique allows one to nearly cover the full energy range of the CAPS IMS from 1 V ? E/Q < 50 kV. Since our technique maps the observations into a local inertial frame, it does work during roll maneuvers. We make comparisons with the bi-Maxwellian fitting technique developed by Wilson et al. (2008) [2] and the similar velocity moment technique by Thomsen et al. (2010) [3]. We concentrate our analysis when ion composition data is available, which is used to weight the non-compositional data, referred to as singles data, to separate H+, H2+ and water group ions (W+) from each other. The chosen periods have high enough telemetry rates (4 kbps or higher) so that coincidence ion data, similar to that used by Sittler et al. (2005) [1] for SOI is available. The ion data set is especially valuable for measuring flow velocities for protons, which are more difficult to derive using singles data within the inner magnetosphere, where the signal is dominated by heavy ions (i.e., proton peak merges with W+ peak as low energy shoulder). Our technique uses a flux function, which is zero in the proper plasma flow frame, to estimate fluid parameter uncertainties. The comparisons investigate the experimental errors and potential for systematic errors in the analyses, including ours. The rolls provide the best data set when it comes to getting 4PI coverage of the plasma but are more susceptible to time aliasing effects. In the future we will then make comparisons with magnetic field observations, Saturn ionosphere conductivities as presently known and the field aligned currents necessary for the planet to enforce corotation of the rotating plasma.

Sittler, E.; Cooper, J.; Hartle, R.; Simpson, D.; Johnson, R.; Thomsen, M.; Arridge, C.

2011-10-01

348

Measuring Transpiration to Regulate Winter Irrigation Rates  

SciTech Connect

Periodic transpiration (monthly sums) in a young loblolly pine plantation between ages 3 and 6 was measured using thermal dissipation probes. Fertilization and fertilization with irrigation were better than irrigation alone in increasing transpiration of young loblolly pines during winter months, apparently because of increased leaf area in fertilized trees. Irrigation alone did not significantly increase transpiration compared with the non-fertilized and non-irrigated control plots.

Samuelson, Lisa [Auburn University] [Auburn University

2006-11-08

349

Heart Rate Variability: Measures and Models  

E-print Network

We focus on various measures of the fluctuations of the sequence of intervals between beats of the human heart, and how such fluctuations can be used to assess the presence or likelihood of cardiovascular disease. We examine sixteen such measures and their suitability for correctly classifying heartbeat records of various lengths as normal or revealing the presence of cardiac dysfunction, particularly congestive heart failure. Using receiver-operating-characteristic analysis we demonstrate that scale-dependent measures prove substantially superior to scale-independent ones. The wavelet-transform standard deviation at a scale near 32 heartbeat intervals, and its spectral counterpart near 1/32 cycles/interval, turn out to provide reliable results using heartbeat records just minutes long. We further establish for all subjects that the human heartbeat has an underlying stochastic origin rather than arising from a chaotic attractor. Finally, we develop a mathematical point process that emulates the human heartbeat time series for both normal subjects and heart-failure patients.

Malvin C. Teich; Steven B. Lowen; Bradley M. Jost; Karin Vibe-Rheymer; Conor Heneghan

2000-08-07

350

What Do Ratings of Infant Temperament Really Measure?  

ERIC Educational Resources Information Center

As data on the reliability and validity of ratings of infant temperament have accumulated, researchers have begun to ask what caregiver ratings really measure. An argument has been made that ratings of social behavior are less a reflection of enduring individual differences than a measure of rater characteristics and error variance. This study…

MacPhee, David

351

The exchange of acetaldehyde between plants and the atmosphere: Stable carbon isotope and flux measurements  

NASA Astrophysics Data System (ADS)

The exchange of acetaldehyde between plant canopies and the atmosphere may significantly influence regional atmospheric chemistry and plant metabolism. While plants are known to both produce and consume acetaldehyde, the exchange of this compound with forested ecosystems is complicated by physical, biological, and chemical processes that range from being poorly understood to completely unknown. This precludes a quantitative understanding of acetaldehyde exchange rates between the atmosphere and the biosphere. In this study, the processes controlling the exchange of acetaldehyde with plant canopies was investigated using concentration, flux, and natural abundance 13C measurements of gas phase acetaldehyde from individual plants, soils, and entire ecosystems. Although previously only considered important in anoxic tissues, it was discovered that acetaldehyde is produced and consumed in leaves through ethanolic fermentation coupled to the pyruvate dehydrogenase bypass system under normal aerobic conditions. These coupled pathways determine the acetaldehyde compensation point, a major factor controlling its exchange with the atmosphere. Carbon isotope analysis suggests a new pathway for acetaldehyde production from plants under stress involving the peroxidation of membrane fatty acids. This pathway may be a major source of acetaldehyde to the atmosphere from plants under biotic and abiotic stresses. Plant stomata were found to be the dominant pathway for the exchange of acetaldehyde with the atmosphere with stomatal conductance influencing both emission and uptake fluxes. In addition, increasing temperature and solar radiation was found to increase the compensation point by increasing the rates of acetaldehyde production relative to consumption. Under ambient conditions, bare soil was neutral to the exchange of acetaldehyde while senescing and decaying leaves were found to be strong source of acetaldehyde to the atmosphere due to increased decomposition processes and the loss of biological sink(s). Vertical concentration profiles and within-canopy turbulence characterization allowed for the estimation of fine scale source/sink profiles of acetaldehyde in forested ecosystems in Michigan, California, and North Carolina. The different vertical and temporal acetaldehyde exchange patterns between the sites were well described using a simple canopy exchange model based on the results from the process based branch studies. We find that net ecosystem acetaldehyde emission rates are inversely related to foliage density by influencing the extinction of sunlight in a plant canopy. While high foliage density canopies can effectively mitigate regional air pollution by behaving as a net sink of atmospheric acetaldehyde, lower density canopies may aggravate it by acting as a net source.

Jardine, Kolby Jeremiah

352

DRPEER: A Motif in the Extracellular Vestibule Conferring High Ca2 Flux Rates in NMDA Receptor Channels  

Microsoft Academic Search

The high flux rate of Ca 2 through NMDA receptor (NMDAR) channels is critical for their biological function and may depend on aC a 2 binding site in the extracellular vestibule. We screened substitutions of hydrophilic residues exposed in the vestibule and identified a cluster of charged residues and a proline, the DRPEER motif, positioned C terminal to M3, that

Junryo Watanabe; Christine Beck; Thomas Kuner; Louis S. Premkumar; Lonnie P. Wollmuth

353

Measuring Fluxes with Better Certainty without a Need for Density Corrections or Pressure Term  

NASA Astrophysics Data System (ADS)

Eddy Covariance flux measurements using gas analyzers of an enclosed design rely on the covariance between instantaneous vertical wind speed and instantaneous output of gas mixing ratio, such that density data are corrected on-the-fly using instantaneous water vapor, temperature and pressure measurements in the cell, collected and aligned with CO2 or other gas of interest. This approach implicitly accounts for the effects of fluctuations in water vapor, temperature and pressure on the density of the gas of interest. Therefore no sensible heat or latent heat portions of Webb-Pearman-Leuning density corrections (WPL) are required, and the pressure term, which is usually neglected in traditional WPL implementation, is accounted for in these mixing ratio-based measurements. A somewhat similar way of calculating fluxes has been used frequently with traditional closed-path analyzers, with some assumptions: (i) slow temperature measurements were used to convert from density to mixing ratio, assuming fast fluctuations of the air temperature to be fully attenuated in the long intake tube; (ii) slow pressure measurements were used, assuming negligible instantaneous pressure fluctuations. Nine field experiments were conducted in a wide range of environmental conditions from Florida to Alaska using an enclosed CO2/H2O gas analyzer. These experiments presented an opportunity to verify the performance of the mixing ratio approach, and examine the differences from traditional density-based measurements. Results indicate that the mixing ratio-based approach helps to minimize or eliminate a number of uncertainties associated with traditional density-based approach, including: (i) uncertainties associated with correcting the product of fast covariances of gas density using sensible and latent heat flux calculated over half-hour or an hour; (ii) uncertainties in the magnitudes of the sensible and latent heat fluxes used in correcting gas flux; (iii) bias in long-term accumulated CO2 flux due to the neglected pressure term. The latest findings on the importance of fast temperature and pressure measurements for CO2 flux on hourly and long-term scales for open-path, closed-path and enclosed designs are discussed. Fundamental differences between gas density and gas mixing ratio for flux measurements are also examined.

Burba, G.; Nakai, T.; Schmidt, A.; Scott, R.; Kathilankal, J.; Fratini, G.; Hanson, C.; Law, B.; McDermitt, D.; Eckles, R.

2012-04-01

354

Aircraft measurement of pollutant fluxes across the borders of eastern Germany  

NASA Astrophysics Data System (ADS)

We performed a research flight along the western and eastern border of eastern Germany to estimate the transboundary flux of pollution gases during a synoptic weather situation with westerly to southwesterly winds. A dolphin flight pattern was applied to sample the boundary layer as representatively as possible while screening the vertical structure of the lower troposphore. Transboundary flux intensities were calculated using concentrations and wind vectors as measured by the aircraft. A detailed error analysis was performed to estimate two types of uncertainties in the transboundary flux measurement. The error originating from inaccuracies in meteorological and chemical measurements was estimated to be in the range 15-35% (one standard deviation). The error originating from the unrepresentativeness of the data collected on the flight path is estimated to be smaller by factors between 2 and 3. Transboundary fluxes at the eastern side of eastern Germany were different from those at the western side at a high level of confidence (>95%). Transboundary fluxes were greater on the eastern side by a factor of 12 for SO 2 and by a factor of 2.9 for NO y. For SO 2, the transboundary fluxes in the Ekman layer (EL) and inversion layer (IL) were greater than those of lower free troposphere (LFT) on both sides, whereas for NO y and O 3 higher LFT wind speeds compensated higher EL and IL mixing ratios. A compilation of all available data on pollutant gas export from eastern Germany reveals a very heterogeneous data set. Computed average fluxes, however, show good agreement with estimates of pollutant gas emissions from eastern Germany, based on energy consumption.

Klemm, Otto; Schaller, Eberhard

355

Measurement characteristics of the ultrasound heart rate monitor  

Microsoft Academic Search

It was reported that the measurement error of the fetal heart rate variability (FHRV), which was obtained by a ultrasound heart rate monitor with the Doppler signal, was large even if the auto-correlation technique was used. Nevertheless, fetal heart rate monitoring by the ultrasound heart rate monitor is necessary to determine the status of the fetus because an invasive test

Y. Noguchi; H. Mamune; S. Sugimoto; J. Yoshida; H. Sasa; H. Kobayashi; M. Kobayashi

1994-01-01

356

Modeling magnetic fields measured by surface probes embedded in a cylindrical flux conserver.  

PubMed

Calculating magnetic fields at the surface of a flux conserver, perfect conductor, for displaced plasma currents is useful for understanding modes of a Z-pinch. The magnetic fields measured at the flux conserver are a sum of the magnetic fields from the plasma current and the eddy currents which form in the walls to keep the flux constant. While the magnetic field at the wall from the plasma current alone is easily calculated using the Biot-Savart law, finding the eddy currents in the flux conserver which satisfy the boundary conditions can be a tedious process. A simple method of calculating the surface magnetic field for a given Z-pinch displacement off-axis is derived for a cylindrical flux conserver. This relationship does not require the explicit calculation of the eddy currents, saving time when analyzing surface magnetic probe measurements. Analytic expressions can be used to describe the surface magnetic field which increase the understanding of the magnetic probe measurements. PMID:17411182

Golingo, R P

2007-03-01

357

Denitrification in the Upper Mississippi River: Rates, controls, and contribution to nitrate flux  

USGS Publications Warehouse

We evaluated patterns of denitrification and factors effecting denitrification in the upper Mississippi River. Measurements were taken over 2 years, during which river discharge ranged from record flooding to base flow conditions. Over the period of study, average denitrification enzyme activity was highest in backwater lakes and lowest in the main channel. Throughout the study reach, highest denitrification enzyme activity occurred during fall and lowest occurred in winter. Rates during spring floods (2001) were only slightly higher than during the preceding winter. Mean unamended denitrification rates ranged from 0.02 (fall 2001 in backwaters) to 0.40 ??g N??cm -2??h-1 (spring 2001 in backwaters). Laboratory experiments showed that denitrification rates increased significantly with addition of NO3- regardless of sediment C content, while rates increased little with addition of labile C (glucose). Denitrification in this reach of the upper Mississippi River appears to be NO3- limited throughout the growing season and the delivery of NO 3- is strongly controlled by river discharge and hydrologie connectivity across the floodplain. We estimate that denitrification removes 6939 t N??year-1 or 6.9% of the total annual NO 3- input to the reach. Hydrologic connectivity and resultant NO3- delivery to high-C sediments is a critical determinant of reach-scale processing of N in this floodplain system.

Richardson, W.B.; Strauss, E.A.; Bartsch, L.A.; Monroe, E.M.; Cavanaugh, J.C.; Vingum, L.; Soballe, D.M.

2004-01-01

358

Eddy covariance flux measurements of ammonia by electron transfer reaction-mass spectrometry  

NASA Astrophysics Data System (ADS)

A system for fast ammonia (NH3) measurements based on a commercial Proton Transfer Reaction-Mass Spectrometer is presented. It uses electron transfer reaction (eTR) as ionisation pathway and features a drift tube of polyetheretherketone (PEEK) and silica-coated steel. Heating the instrumental inlet and the drift tube to 180° C enabled an effective time resolution of ~1 s and made it possible to apply the eTR-MS for eddy covariance (EC) measurements. EC fluxes of NH3 were measured over two agricultural fields in Oensingen, Switzerland, following fertilisations with cattle slurry. Air was aspirated close to a sonic anemometer at a flow of 100 STP L min-1 and was directed through a 23 m long 1/2" PFA tube heated to 150°C to an air-conditioned trailer where the eTR-MS sub-sampled from the large bypass stream. This setup minimised damping of fast NH3 concentration changes between the sampling point and the actual measurement. High-frequency attenuation loss of the NH3 fluxes of 20 to 40% was quantified and corrected for using an empirical ogive method. The instrumental NH3 background signal showed a minor interference with H2O which was characterised in the laboratory. The resulting correction of the NH3 flux after slurry spreading was less than 1‰. The flux detection limit of the EC system was about 5 ng m-2 s-1 while the accuracy of individual flux measurements was estimated 16% for the high-flux regime during these experiments. The NH3 emissions after broad spreading of the slurry showed an initial maximum of 150 ?g m2 s-1 with a fast decline in the following hours.

Sintermann, J.; Spirig, C.; Jordan, A.; Kuhn, U.; Ammann, C.; Neftel, A.

2010-11-01

359

Eddy covariance flux measurements of ammonia by high temperature chemical ionisation mass spectrometry  

NASA Astrophysics Data System (ADS)

A system for fast ammonia (NH3) measurements with chemical ionisation mass spectrometry (CIMS) based on a commercial Proton Transfer Reaction-Mass Spectrometer (PTR-MS) is presented. It uses electron transfer reaction as ionisation pathway and features a drift tube of polyetheretherketone (PEEK) and silica-coated steel. Heating the instrumental inlet and the drift tube to 180 °C enabled an effective time resolution of ~1 s and made it possible to apply the instrument for eddy covariance (EC) measurements. EC fluxes of NH3 were measured over two agricultural fields in Oensingen, Switzerland, following fertilisations with cattle slurry. Air was aspirated close to a sonic anemometer at a flow of 100 STP L min-1 and was directed through a 23 m long 1/2" PFA tube heated to 150 °C to an air-conditioned trailer where the gas was sub-sampled from the large bypass stream. This setup minimised damping of fast NH3 concentration changes between the sampling point and the actual measurement. High-frequency attenuation loss of the NH3 fluxes of 20 to 40% was quantified and corrected for using an empirical ogive method. The instrumental NH3 background signal showed a minor interference with H2O which was characterised in the laboratory. The resulting correction of the NH3 flux after slurry spreading was less than 1‰. The flux detection limit of the EC system was about 5 ng m-2 s-1 while the accuracy of individual flux measurements was estimated 16% for the high-flux regime during these experiments. The NH3 emissions after broad spreading of the slurry showed an initial maximum of 150 ?g m-2 s-1 with a fast decline in the following hours.

Sintermann, J.; Spirig, C.; Jordan, A.; Kuhn, U.; Ammann, C.; Neftel, A.

2011-03-01

360

Measuring Task-related Changes in Heart Rate Variability  

Microsoft Academic Search

Small beat-to-beat differences in heart rate are the result of dynamic control of the cardiovascular system by the sympathetic and parasympathetic nervous systems. Heart rate variability (HRV) has been positively correlated with both mental and physical health. While many studies measure HRV under rest conditions, few have measured HRV during stressful situations. We describe an experimental protocol designed to measure

Ziev B. Moses; Linda J. Luecken; James C. Eason

2007-01-01

361

Measuring rates of outdoor airflow into HVAC systems  

SciTech Connect

During the last few years, new technologies have been introduced for measuring the flow rates of outside air into HVAC systems. This document describes one particular technology for measuring these airflows, a system and a related protocol developed to evaluate this and similar measurement technologies under conditions without wind, and the results of our evaluations. We conclude that the measurement technology evaluated can provide a reasonably accurate measurement of OA flow rate over a broad range of flow, without significantly increasing airflow resistance.

Fisk, William J.; Faulkner, David; Sullivan, Douglas P.; Delp, Woody

2002-10-01

362

Nano-engineering the boiling surface for optimal heat transfer rate and critical heat flux  

E-print Network

The effects on pool boiling characteristics such as critical heat flux and the heat transfer coefficient of different surface characteristics such as surface wettability, roughness, morphology, and porosity are not well ...

Phillips, Bren Andrew

2011-01-01

363

Marine particle dynamics : sinking velocities, size distributions, fluxes, and microbial degradation rates  

E-print Network

The sinking flux of particulate matter into the ocean interior is an oceanographic phenomenon that fuels much of the metabolic demand of the subsurface ocean and affects the distribution of carbon and other elements ...

McDonnell, Andrew M. P

2011-01-01

364

Using Airborne Microwave Remotely Sensed Root-Zone Soil Moisture and Flux Measurements to Improve Regional Predictions of Carbon Fluxes in a Terrestrial Biosphere Model  

NASA Astrophysics Data System (ADS)

North American ecosystems are critical components of the global carbon cycle, exchanging large amounts of carbon dioxide and other gases with the atmosphere. Net ecosystem exchange (NEE) of CO2 between atmosphere and ecosystems quantifies these carbon fluxes, but current continental-scale estimates contain high levels of uncertainty. Root-zone soil moisture (RZSM) and its spatial and temporal heterogeneity influences NEE and improved estimates can help reduce uncertainty in NEE estimates. We used the RZSM measurements from the Airborne Microwave Observatory of Subcanopy and Subsurface (AirMOSS) mission, and the carbon, water and energy fluxes observed by the eddy-covariance flux towers to constrain the Ecosystem Demography Model 2.2 (ED2.2) to improve its predictions of carbon fluxes. The parameters of the ED2.2 model were first optimized at seven flux tower sites in North America, which represent six different biomes, by constraining the model against a suite of flux measurements and forest inventory measurements through a Bayesian Markov-Chain Monte Carlo framework. We further applied the AirMOSS RZSM products to constrain the ED2.2 model to achieve better estimates of regional NEE. Evaluation against flux tower measurements and forest dynamics measurements shows that the constrained ED2.2 model produces improved predictions of monthly to annual carbon fluxes. The remote sensing based RZSM can further help improve the spatial patterns and temporal variations of model NEE. The results demonstrate that model-data fusion can substantially improve model performance and highlight the important role of RZSM in regulating the spatial and temporal heterogeneities of carbon fluxes.

Zhang, K.; Antonarakis, A. S.; Medvigy, D.; Burgin, M. S.; Crow, W. T.; Milak, S.; Jaruwatanadilok, S.; Truong-Loi, M.; Moghaddam, M.; Saatchi, S. S.; Cuenca, R. H.; Moorcroft, P. R.

2013-12-01

365

VOC fluxes over a Boreal forest estimated from tethered balloon measurements  

NASA Astrophysics Data System (ADS)

Some volatile organic compounds (VOCs) emitted by plants have the potential to significantly contribute to aerosol concentrations through secondary organic aerosol formation. We measured biogenic VOCs at Hyytiälä (FIN), a site where particle formation events have frequently been observed throughout the last years. As these events are postulated to occur on a spatially large scale, we aimed to study biogenic VOC fluxes at landscape scale. By means of a tethered balloon, ambient concentrations of isoprene and terpenes were measured at heights between 50 m and 1 km above ground. Average concentrations of isoprene and terpenes (with a-pinene, D3-carene and limonene as dominating components) in the planetary boundary layer (PBL) were 13 and 33 ppt, respectively. We used a budget approach and a mixed layer gradient technique to derive surface flux estimates from these measurements. Total terpene fluxes (midday) during August 2001 ranged between 100 and 500 ugC/m2/h, isoprene emissions were below 50 ugC/m2/h. A particle trajectory model and detailed land-use data close to the site were used to perform a footprint analysis for the BVOC measurements on the balloon. Fluxes as derived from these techniques are representative for areas of the order of tens to hundreds of square kilometers, but reliable estimates require averaging over a number of measurements, mainly a consequence of spatial heterogeneity in emissions in that region.

Spirig, C.; Guenther, A.; Greenberg, J.

2003-04-01

366

High CO2 emissions through porous media: Transport mechanisms and implications for flux measurement and fractionation  

USGS Publications Warehouse

Diffuse emissions of CO2 are known to be large around some volcanoes and hydrothermal areas. Accumulation-chamber measurements of CO2 flux are increasingly used to estimate the total magmatic or metamorphic CO2 released from such areas. To assess the performance of accumulation chamber systems at fluxes one to three orders of magnitude higher than normally encountered in soil respiration studies, a test system was constructed in the laboratory where known fluxes could be maintained through dry sand. Steady-state gas concentration profiles and fractionation effects observed in the 30-cm sand column nearly match those predicted by the Stefan-Maxwell equations, indicating that the test system was functioning successfully as a uniform porous medium. Eight groups of investigators tested their accumulation chamber equipment, all configured with continuous infrared gas analyzers (IRGA), in this system. Over a flux range of ~ 200-12,000 g m-2 day-1, 90% of their 203 flux measurements were 0-25% lower than the imposed flux with a mean difference of - 12.5%. Although this difference would seem to be within the range of acceptability for many geologic investigations, some potential sources for larger errors were discovered. A steady-state pressure gradient of -20 Pa/m was measured in the sand column at a flux of 11,200 g m-2 day-1. The derived permeability (50 darcies) was used in the dusty-gas model (DGM) of transport to quantify various diffusive and viscous flux components. These calculations were used to demonstrate that accumulation chambers, in addition to reducing the underlying diffusive gradient, severely disrupt the steady-state pressure gradient. The resultant diversion of the net gas flow is probably responsible for the systematically low flux measurements. It was also shown that the fractionating effects of a viscous CO2 efflux against a diffusive influx of air will have a major impact on some important geochemical indicators, such as N2/Ar, ??15N-N2, and 4He/22Ne. Published by Elsevier Science B.V.

Evans, W. C.; Sorey, M. L.; Kennedy, B. M.; Stonestrom, D. A.; Rogie, J. D.; Shuster, D. L.

2001-01-01

367

Eddy covariance flux measurements of ammonia with eTR-MS  

NASA Astrophysics Data System (ADS)

Micrometerological flux measurements of ammonia (NH3) are very difficult due to the stickiness of the NH3 molecule to all surfaces. Only recently, sensitive and fast responding instruments became available that opened the posibility to perform an Eddy Covariance approach to measure NH3 fluxes. Norman et al. (2006, 2007) showed that a modified commercial Proton Transfer Reaction-Mass Spectrometer from IONICON using charged oxygen molecules instead of protons reliably measured concentrations, but had too strong damping within the drift tube and the inlet lines for EC flux measurements. In the mean time a new smaller drift tube became available that can be heated up to 180°C. With this configuration the response time was below 1 sec. Heating also the whole inlet line to temperature above 100°C enabled NH3 EC flux measurements. The performance of the system was tested during two fertilization events (organic manure and urea application) at the Oensingen grassland site in Switzerland. The measured fluxes were in good agreement with an Aerodynamic Gradient approach and showed a similar dynamic range. The sensitivity of the eTR-MS systems seems to be in the same order of magnitude as state of the art gradient systems. References: Norman, M., Wisthaler, A., and Hansel, A. (2007). O2+ as primary reagent ion in the PTR-MS instrument: Detection of gas-phase ammonia, International Journal of Mass Spectrometry 265, 382-387. Norman, M., Spirig, C., Wolff, V., Trebs, I., Flechard, C., Wisthaler, A., Schnitzhofer, R., Hansel, A., and Neftel, A.: Intercomparison of ammonia measurement techniques at an intensively managed grassland site (Oensingen, Switzerland), Atmospheric Chemistry and Physics, 9, 2635-2645, 2009.

Sintermann, Jörg; Kuhn, Uwe; Neftel, Albrecht

2010-05-01

368

Regional inversion of CO2 ecosystem fluxes from atmospheric measurements: reliability of the uncertainty estimates  

NASA Astrophysics Data System (ADS)

The Bayesian framework of CO2 flux inversions permits estimates of the retrieved flux uncertainties. Here, the reliability of these theoretical estimates is studied through a comparison against the misfits between the inverted fluxes and independent measurements of the CO2 Net Ecosystem Exchange (NEE) made by the eddy covariance technique at local (few hectares) scale. Regional inversions at 0.5° resolution are applied for the western European domain where ~ 50 eddy covariance sites are operated. These inversions are conducted for the period 2002-2007. They use a mesoscale atmospheric transport model, a prior estimate of the NEE from a terrestrial ecosystem model and rely on the variational assimilation of in situ continuous measurements of CO2 atmospheric mole fractions. Averaged over monthly periods and over the whole domain, the misfits are in good agreement with the theoretical uncertainties for prior and inverted NEE, and pass the chi-square test for the variance at the 30% and 5% significance levels respectively, despite the scale mismatch and the independence between the prior (respectively inverted) NEE and the flux measurements. The theoretical uncertainty reduction for the monthly NEE at the measurement sites is 53% while the inversion decreases the standard deviation of the misfits by 38%. These results build confidence in the NEE estimates at the European/monthly scales and in their theoretical uncertainty from the regional inverse modelling system. However, the uncertainties at the monthly (respectively annual) scale remain larger than the amplitude of the inter-annual variability of monthly (respectively annual) fluxes, so that this study does not engender confidence in the inter-annual variations. The uncertainties at the monthly scale are significantly smaller than the seasonal variations. The seasonal cycle of the inverted fluxes is thus reliable. In particular, the CO2 sink period over the European continent likely ends later than represented by the prior ecosystem model.

Broquet, G.; Chevallier, F.; Bréon, F.-M.; Kadygrov, N.; Alemanno, M.; Apadula, F.; Hammer, S.; Haszpra, L.; Meinhardt, F.; Morguí, J. A.; Necki, J.; Piacentino, S.; Ramonet, M.; Schmidt, M.; Thompson, R. L.; Vermeulen, A. T.; Yver, C.; Ciais, P.

2013-09-01

369

Regional inversion of CO2 ecosystem fluxes from atmospheric measurements: reliability of the uncertainty estimates  

NASA Astrophysics Data System (ADS)

The Bayesian framework of CO2 flux inversions permits estimates of the retrieved flux uncertainties. Here, the reliability of these theoretical estimates is studied through a comparison against the misfits between the inverted fluxes and independent measurements of the CO2 Net Ecosystem Exchange (NEE) made by the eddy covariance technique at local (few hectares) scale. Regional inversions at 0.5° resolution are applied for the western European domain where ~ 50 eddy covariance sites are operated. These inversions are conducted for a 6-yr period (2002-2007). They use a mesoscale atmospheric transport model, a prior estimate of the NEE from a terrestrial ecosystem model and rely on the variational assimilation of in situ continuous measurements of CO2 atmospheric mole fractions. The misfits averaged over monthly periods and over the whole domain, are in good agreement with the theoretical uncertainties for prior (respectively inverted) NEE, with positive chi-square tests for the variance at the 2% (respectively 20%) significance levels, despite the scale mismatch and the independence between the prior (respectively inverted) NEE and the flux measurements. The theoretical uncertainty reduction for the monthly NEE at the measurement sites is 53% while the inversion actually decreases the standard deviation of the misfits by as much as 38%. These results build confidence in the NEE estimates at the European/monthly scales and in their theoretical uncertainty from the regional inverse modeling system. However, the uncertainties at the monthly (respectively annual) scale remain larger than the amplitude of the inter-annual variability of monthly (respectively annual) fluxes, so that there is a low confidence in the inter-annual variations. The uncertainties at the monthly scale are significantly smaller than the seasonal variations. The seasonal cycle of the inverted fluxes is thus reliable. In particular, the CO2 sink period over the European continent likely ends later than represented by the ecosystem model.

Broquet, G.; Chevallier, F.; Bréon, F.-M.; Alemanno, M.; Apadula, F.; Hammer, S.; Haszpra, L.; Meinhardt, F.; Necki, J.; Piacentino, S.; Ramonet, M.; Schmidt, M.; Thompson, R. L.; Vermeulen, A. T.; Yver, C.; Ciais, P.

2013-03-01

370

Shortwave Flux from Satellite-Measured Radiance: A Theoretical Study over Marine Boundary Layer Clouds.  

NASA Astrophysics Data System (ADS)

Earth radiation budget measurements, important to climate monitoring and to validating climate models, require that radiances measured by satellite instruments be converted to hemispherical flux. This paper examines that problem theoretically, using inhomogeneous cloud models constructed from Landsat scenes of marine boundary layer clouds. The spherical harmonics discrete ordinates method (SHDOM) code is applied to the model scenes to compute full two-dimensional radiation fields, which then simulate measured radiances. Inversion to flux is performed by several different methods, including plane-parallel table lookup and empirical angular distribution models with three different ways of determining scene identification, to examine error sources and relative magnitudes. Using a simple plane-parallel table lookup results in unacceptably large flux bias errors of 11%-60%, depending on the orbital viewing geometry. This bias can be substantially reduced, to no more than 6%, by using empirical angular distribution models. Further improvement, to no more than 2% flux bias error, is obtained if known biases in optical-depth retrievals are taken into account when building the angular models. Last, the bias can be further reduced to a fraction of a percent using scene identification based on multiple views of the same area. There are limits, however, to the reduction in the instantaneous error with this approach. Trends in the flux error are also identified, in particular an equator-to-pole trend in the flux bias. Given the importance of satellite measurements for determining heat transport from equator to pole, this consistent bias should be kept in mind, and efforts should be made to reduce it in the future.

Chambers, L. H.; Wielicki, B. A.; Loeb, N. G.

2001-12-01

371

Measuring the flux at the interface of coal-tar impacted sediment and river water near a former MGP site.  

PubMed

Determining water movement through contaminated sediment is critical for characterizing transport of chemicals from the sediment to the overlying water. Field studies to characterize the water flow across the sediment-water interface within a river adjacent to a former manufactured gas plant site were conducted. For this purpose, a new design of an interfacial flow meter was developed and tested. The in situ components of the system consisted of: a cylinder with an interfacial area of 2342 cm2; a dome attached to the cylinder; and a flow tube that allows water to flow from inside the dome to the river at the rate equal to the specific discharge across the sediment-water boundary. A 'heat-pulse' method was used to measure flow by heating the center of the flow tube for a brief time period and measuring the temperature profile within the tube over time. The system was calibrated to measure volumetric flux in the range 1.5-4.0 cm d(-1), however using a flow-addition method, the measurement of lower velocities also was accomplished, and calibration at higher fluxes is possible. From the groundwater flow at the interface of the coal-tar impacted sediment and information on the sediment pore water concentrations of several PAHs (poly-cyclic aromatic hydrocarbons), the mass flux of these PAHs to the river were estimated. Information on PAH mass flux at the sediment-water interface is useful for site assessment, including the evaluation of remediation alternatives and longer term site characterization. PMID:17382368

Hyun, Seunghun; Jafvert, Chad T; Jenkinson, Byron; Enfield, Carl; Johnson, Brian

2007-06-01

372

Heat flux measurement from thermal infrared imagery in low-flux fumarolic zones: Example of the Ty fault (La Soufrière de Guadeloupe)  

NASA Astrophysics Data System (ADS)

Monitoring the geothermal flux of a dormant volcano is necessary both for hazard assessment and for studying hydrothermal systems. Heat from a magma body located at depth is transported by steam to the surface, where it is expelled in fumaroles if the heat flow exceeds 500 W/m2. If the heat flow is lower than 500 W/m2, steam mainly condensates in the soil close to surface and produces a thermal anomaly detectable at the surface. In this study, we propose a method to quantify low heat fluxes from temperature anomalies measured at the surface by a thermal infrared camera. Once corrected from the atmospheric and surface effects, thermal infrared images are used to compute (1) the excess of radiative flux, (2) the excess of sensible flux and (3) the steam flux from the soil to the atmosphere. These calculations require measurements of atmospheric parameters (temperature, wind velocity and humidity) and estimations of surface parameters (roughness and emissivity). This method has been tested on a low-flux fumarolic zone of the Soufrière volcano (Guadeloupe Island — Lesser Antilles), and compared to a flux estimation realized from the thermal gradient measurements into the soil. The two methods show a good agreement and a similar precision (267 ± 46 W/m2 for the thermal infrared method, and 275 ± 50 W/m2 for the vertical temperature gradient method), if surface roughness is well calibrated.

Gaudin, Damien; Beauducel, François; Allemand, Pascal; Delacourt, Christophe; Finizola, Anthony

2013-11-01

373

Seasonal variability in gaseous mercury fluxes measured in a high-elevation meadow  

NASA Astrophysics Data System (ADS)

Seasonal patterns of atmospheric mercury (Hg) fluxes measured over vegetated terrestrial systems can provide insight into the underlying process controlling emission and deposition of Hg to vegetated surfaces. Gaseous elemental Hg fluxes were measured for week-long periods in each season (spring, summer, fall, and winter) over an uncontaminated high-elevation wetland meadow in Shenandoah National Park, Virginia using micrometeorological methods. Mean net deposition was observed in the spring (-4.8 ng m -2 h -1), emission in the summer (2.5 ng m -2 h -1), near zero flux in the fall (0.3 ng m -2 h -1), and emission in the winter (4.1 ng m -2 h -1). Nighttime deposition (when stomata are closed) and the poor correlation between Hg fluxes and canopy conductance during periods of active vegetation growth suggest that stomatal processes are not the dominant mechanism for ecosystem-level GEM exchange at this site. The strong springtime deposition relative to summer implies that young vegetation is better at scavenging Hg, with the highest deposition occurring at night possibly via a cuticular pathway. These results suggest that spring is a period of GEM deposition while other seasons exhibit net emission, emphasizing the importance of capturing GEM flux seasonality when determining total Hg budgets.

Converse, A. D.; Riscassi, A. L.; Scanlon, T. M.

2010-06-01

374

Surface Measurements of Oxygen, Carbon Dioxide and Water Vapor Fluxes Using AN Automated Chamber System  

NASA Astrophysics Data System (ADS)

The various soil respiration measurements that are available depend on measuring the emitted CO2 flux as organic carbon is respired aerobically. Comparative studies among the four well known methods (the open-flow infra-red gas analyzer method; the closed chamber method; the dynamic closed chamber method; and the alkali absorption method) under field conditions and laboratory experiments show differences. The discrepancies observed in these methods under field conditions could be evaluated by incorporating O2