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Sample records for absorption measurement technique

  1. Tone-burst technique measures high-intensity sound absorption

    NASA Technical Reports Server (NTRS)

    Powell, J. G.; Van Houten, J. J.

    1971-01-01

    Tone-burst technique, in which narrow-bandwidth, short-duration sonic pulse is propagated down a standing-wave tube, measures sound absorbing capacity of materials used in jet engine noise abatement. Technique eliminates effects of tube losses and yields normal-incidence absorption coefficient of specimen.

  2. Recent improvements in PDS technique for low-absorption measurements

    NASA Astrophysics Data System (ADS)

    Montecchi, Marco; Masetti, Enrico; Emiliani, Gabriele

    1990-08-01

    Photothermal Deflection Spectroscopy (PDS) is a recently developed technique that is finding a useful application in the measurement of low optical absorptance of thin films. Among the noise sources affecting the PDS measurement, probe beam pointing instability and mechanical vibration play a considerable role. In this work an optoelectronic system for the reduction of their influence is described. Moreover, PDS measurements are typically performed keeping the sample immersed in a deflecting liquid; thus measured values of absorptance must be corrected when other surrounding media, as air, are considered. This correction is an easy task for single film coatings. Here the general case of an unknown multiplayer coating is analysed; a range of values containing the true absorptance in air is obtained by theoretical analysis and a practical method to evaluate the absorptance in air is discussed. Finally, deflecting liquids alternative to the commonly used CCI4 have been examined. Useful optical range, thermal diffusivity and "relative deflecting power" of CCI4, CS2, Iso-octane and Aceton are reported.

  3. Measurement of the absorption coefficient using the sound-intensity technique

    NASA Technical Reports Server (NTRS)

    Atwal, M.; Bernhard, R.

    1984-01-01

    The possibility of using the sound intensity technique to measure the absorption coefficient of a material is investigated. This technique measures the absorption coefficient by measuring the intensity incident on the sample and the net intensity reflected by the sample. Results obtained by this technique are compared with the standard techniques of measuring the change in the reverberation time and the standing wave ratio in a tube, thereby, calculating the random incident and the normal incident adsorption coefficient.

  4. Laser induced deflection technique for absolute thin film absorption measurement: optimized concepts and experimental results

    SciTech Connect

    Muehlig, Christian; Kufert, Siegfried; Bublitz, Simon; Speck, Uwe

    2011-03-20

    Using experimental results and numerical simulations, two measuring concepts of the laser induced deflection (LID) technique are introduced and optimized for absolute thin film absorption measurements from deep ultraviolet to IR wavelengths. For transparent optical coatings, a particular probe beam deflection direction allows the absorption measurement with virtually no influence of the substrate absorption, yielding improved accuracy compared to the common techniques of separating bulk and coating absorption. For high-reflection coatings, where substrate absorption contributions are negligible, a different probe beam deflection is chosen to achieve a better signal-to-noise ratio. Various experimental results for the two different measurement concepts are presented.

  5. Measurement of initial absorption of fused silica at 193nm using laser induced deflection technique (LID)

    NASA Astrophysics Data System (ADS)

    Schönfeld, Dörte; Klett, Ursula; Mühlig, Christian; Thomas, Stephan

    2008-01-01

    The ongoing development in microlithography towards further miniaturization of structures creates a strong demand for lens material with nearly ideal optical properties. Beside the highly demanding requirements on homogeneity and stress induced birefringence (SIB), low absorption is a key factor. Even a small absorption is associated with a temperature increase and results in thermally induced local variations of refractive index and SIB. This could affect the achievable resolution of the lithographic process. The total absorption of the material is composed of initial absorption and of absorption induced during irradiation. Thus, the optimization of both improves the lifetime of the material. In principal, it is possible to measure transmission and scattering with a suitable spectrometer assembly and calculate absorption from them. However, owing to the influence of sample surfaces and errors of measurement, these methods usually do not provide satisfactory results for highly light-transmissive fused silica. Therefore, it is most desirable to find a technique that is capable of directly measuring absorption coefficients in the range of (1...10)•10 -4 cm -1 (base 10) directly. We report our first results for fused silica achieved with the LID technique. Besides a fused silica grade designed for 193 nm applications, grades with higher absorption at 193 nm were measured to test the LID technique. A special focus was set on the possibility of measuring initial absorption without the influence of degradation effects.

  6. Absorption measurement of thin films by using photothermal techniques: The influence of thermal properties

    SciTech Connect

    Wu, Z.L.; Kuo, P.K.; Thomas, R.L.; Fan, Z.X.

    1995-12-31

    Photothermal techniques are widely used for measuring optical absorption of thin film coatings. In these applications the calibration of photothermal signal is typically based on the assumption that the thermal properties of the thin film make very little contribution. In this paper we take mirage technique as an example and present a detailed analysis of the influence of thin film thermal properties on absorption measurements. The results show that the traditional calibration method is not valid on surprisingly many situations.

  7. Sensitive and absolute absorption measurements in optical materials and coatings by laser-induced deflection technique

    NASA Astrophysics Data System (ADS)

    Mühlig, Christian; Bublitz, Simon

    2012-12-01

    The laser-induced deflection (LID) technique, a photo-thermal deflection setup with transversal pump-probe-beam arrangement, is applied for sensitive and absolute absorption measurements of optical materials and coatings. Different LID concepts for bulk and transparent coating absorption measurements, respectively, are explained, focusing on providing accurate absorption data with only one measurement and one sample. Furthermore, a new sandwich concept is introduced that allows transferring the LID technique to very small sample geometries and to significantly increase the sensitivity for materials with weak photo-thermal responses. For each of the different concepts, a representative application example is given. Particular emphasis is placed on the importance of the calibration procedure for providing absolute absorption data. The validity of an electrical calibration procedure for the LID setup is proven using specially engineered surface absorbing samples. The electrical calibration procedure is then applied to evaluate two other approaches that use either doped samples or highly absorptive reference samples.

  8. Combined laser calorimetry and photothermal technique for absorption measurement of optical coatings

    SciTech Connect

    Li Bincheng; Blaschke, Holger; Ristau, Detlev

    2006-08-10

    To the best of our knowledge, a combined sensitive technique employing both laser calorimetry and a surface thermal lens scheme for measuring absorption values of optical coatings is presented for the first time. Laser calorimetric and pulsed surface thermal lens signals are simultaneously obtained with a highly reflecting UV coating sample irradiated at 193 nm. The advantages and potential applications of the combined technique and the experimental factors limiting the measurement sensitivity are discussed.

  9. Combined laser calorimetry and photothermal technique for absorption measurement of optical coatings.

    PubMed

    Li, Bincheng; Blaschke, Holger; Ristau, Detlev

    2006-08-10

    To the best of our knowledge, a combined sensitive technique employing both laser calorimetry and a surface thermal lens scheme for measuring absorption values of optical coatings is presented for the first time. Laser calorimetric and pulsed surface thermal lens signals are simultaneously obtained with a highly reflecting UV coating sample irradiated at 193 nm. The advantages and potential applications of the combined technique and the experimental factors limiting the measurement sensitivity are discussed.

  10. Photothermal self-phase-modulation technique for absorption measurements on high-reflective coatings.

    PubMed

    Steinlechner, Jessica; Jensen, Lars; Krüger, Christoph; Lastzka, Nico; Steinlechner, Sebastian; Schnabel, Roman

    2012-03-10

    We propose and demonstrate a new measurement technique for the optical absorption of high-reflection coatings. Our technique is based on photothermal self-phase modulation and exploits the deformation of cavity Airy peaks that occurs due to coating absorption of intracavity light. The mirror whose coating is under investigation needs to be the input mirror of a high-finesse cavity. Our example measurements were performed on a high-reflection SiO2-Ta2O5 coating in a three-mirror ring-cavity setup at a wavelength of 1064 nm. The optical absorption of the coating was determined to be α=(23.9±2.0)·10(-6) per coating. Our result is in excellent agreement with an independently performed laser calorimetry measurement that gave a value of α=(24.4±3.2)·10(-6) per coating. Since the self-phase modulation in our coating-absorption measurement affects mainly the propagation through the cavity input mirror, our measurement result is practically uninfluenced by the optical absorption of the other cavity mirrors.

  11. Differential absorption lidar technique for measurement of the atmospheric pressure profile

    NASA Technical Reports Server (NTRS)

    Korb, C. L.; Weng, C. Y.

    1983-01-01

    A new two-wavelength lidar technique for remotely measuring the pressure profile using the trough absorption region between two strong lines in the oxygen A band is described. The theory of integrated vertical path, differential ranging, and horizontal-path pressure measurements is given, with methods to desensitize and correct for temperature effects. The properties of absorption troughs are described and shown to reduce errors due to laser frequency jitter by up to two orders of magnitude. A general analysis, including laser bandwidth effects, demonstrates that pressure measurements with an integrated-vertical-path technique are typically fifty times more accurate than with a differential ranging technique. Simulations show 0.1-0.3 percent accuracy for ground and Shuttle-based pressure-profile and surface-pressure experiments.

  12. Sandwich concept: enhancement for direct absorption measurements by laser-induced deflection (LID) technique

    NASA Astrophysics Data System (ADS)

    Mühlig, Ch.; Bublitz, S.; Paa, W.

    2012-11-01

    The new sandwich concept for absolute photo-thermal absorption measurements using the laser induced deflection (LID) technique is introduced and tested in comparison to the standard LID concept. The sandwich concept's idea is the decoupling of the optical materials for the pump and probe beams by placing a sample of investigation in between two optical (sandwich) plates. The pump beam is guided through the sample whereas the probe beams are deflected within the sandwich plates by the thermal lens that is generated by heat transfer from the irradiated sample. Electrical simulation and laser experiments reveal that using appropriate optical materials for the sandwich plates, the absorption detection limit for photo-thermally insensitive materials can be lowered by up to two orders of magnitude. Another advantage of the sandwich concept, the shrinking of the currently required minimum sample size, was used to investigate the laser induced absorption change in a Nd:YVO4 crystal at 1030nm. It was found that the absorption in Nd:YVO4 lowers due to the laser irradiation but partially recovers during irradiation breaks. Furthermore, absorption spectroscopy has been performed at two LBO crystals in the wavelength range 410...600nm to study the absorption structure around the SHG wavelengths of common high power lasers based on Neodymium doped laser crystals.

  13. Method and apparatus for measuring butterfat and protein content using microwave absorption techniques

    DOEpatents

    Fryer, Michael O.; Hills, Andrea J.; Morrison, John L.

    2000-01-01

    A self calibrating method and apparatus for measuring butterfat and protein content based on measuring the microwave absorption of a sample of milk at several microwave frequencies. A microwave energy source injects microwave energy into the resonant cavity for absorption and reflection by the sample undergoing evaluation. A sample tube is centrally located in the resonant cavity passing therethrough and exposing the sample to the microwave energy. A portion of the energy is absorbed by the sample while another portion of the microwave energy is reflected back to an evaluation device such as a network analyzer. The frequency at which the reflected radiation is at a minimum within the cavity is combined with the scatter coefficient S.sub.11 as well as a phase change to calculate the butterfat content in the sample. The protein located within the sample may also be calculated in a likewise manner using the frequency, S.sub.11 and phase variables. A differential technique using a second resonant cavity containing a reference standard as a sample will normalize the measurements from the unknown sample and thus be self-calibrating. A shuttered mechanism will switch the microwave excitation between the unknown and the reference cavities. An integrated apparatus for measuring the butterfat content in milk using microwave absorption techniques is also presented.

  14. Development of the laser absorption radiation thermometry technique to measure thermal diffusivity in addition to temperature

    NASA Astrophysics Data System (ADS)

    Levick, Andrew; Lobato, Killian; Edwards, Gordon

    2003-01-01

    A comparative technique based on photothermal radiometry has been developed to measure thermal diffusivity of semi-infinite targets with arbitrary geometry. The technique exploits the principle that the frequency response of the temperature modulation induced by a periodic modulated heating source (in this case a laser spot) scales with thermal diffusivity. To demonstrate this technique, a photothermal radiometer has been developed, which detects modulated thermal radiance at a wavelength of 2 μm due to a small temperature modulation induced on the target surface by a modulated erbium fiber laser of power 1 W. Two frequency responses were measured for platinum and oxidized Inconel 600 targets (the frequency response is a scan of the amplitude of the modulated thermal radiance over laser modulation frequency). Scaling the two responses with respect to frequency gives a ratio of thermal diffusivities Dplatinum/DInconel of 4.45(33) which compares with a literature value of 4.46(50). The aim is to combine this technique with laser absorption radiation thermometry to produce multithermal property instrument for measuring "industrial" targets.

  15. Photoacoustic technique for simultaneous measurements of thermal effusivity and absorptivity of pigments in liquid solution.

    PubMed

    Balderas-López, J A; Díaz-Reyes, J; Zelaya-Angel, O

    2011-12-01

    A photoacoustic (PA) methodology, in the transmission configuration, for simultaneous measurements of thermal effusivity and molar absorption coefficient (absorptivity) for pigments in liquid solution is introduced. The analytical treatment involves a self-normalization procedure for the PA signal, as a function of the modulation frequency, for a strong absorbing material in the thermally thin regime, when the light travels across the sample under study. Two fitted parameters are obtained from the analysis of the self-normalized PA amplitude and phase, one of them proportional to the sample's optical absorption coefficient and from which, taking it for a series of samples at different concentrations, the pigment's absorptivity in liquid solution can be measured, the other one yields the sample's thermal effusivity. Methylene blue's absorptivity in distilled water was measured with this methodology at 658 nm, finding good agreement with the corresponding one reported in the literature.

  16. Spectral fluorescence signature techniques and absorption measurements for continuous monitoring of biofuel-producing microalgae cultures

    NASA Astrophysics Data System (ADS)

    Martín de la Cruz, M. C.; Gonzalez Vilas, L.; Yarovenko, N.; Spyrakos, E.; Torres Palenzuela, J. M.

    2013-08-01

    Biofuel production from microalgae can be both sustainable and economically viable. Particularly in the case of algal growth in wastewater an extra benefit is the removal or biotransformation of pollutants from these types of waters. A continuous monitoring system of the microalgae status and the concentration of different wastewater contaminants could be of great help in the biomass production and the water characterisation. In this study we present a system where spectral fluorescence signature (SFS) techniques are used along with absorption measurements to monitor microalgae cultures in wastewater and other mediums. This system aims to optimise the microalgae production for biofuel applications or other uses and was developed and tested in prototype indoor photo-bioreactors at the University of Vigo. SFS techniques were applied using the fluorescence analyser INSTAND-SCREENER developed by Laser Diagnostic Instruments AS. INSTAND-SCREENER permits wavelength scanning in two modes, one in UV and another in VIS. In parallel, it permits the on-line monitoring and rapid analysis of both water quality and phytoplankton status without prior treatment of the sample. Considering that different contaminants and microalgae features (density, status etc.) have different spectral signatures of fluorescence and absorption properties, it is possible to characterise them developing classification libraries. Several algorithms were used for the classification. The implementation of this system in an outdoor raceway reactor in a Spanish wastewater treatment plant is also discussed. This study was part of the Project EnerBioAlgae (http://www.enerbioalgae.com/), which was funded by the Interreg SUDOE and led by the University of Vigo.

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

    PubMed

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

    2008-03-15

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

  18. Continuous wave laser absorption techniques for gasdynamic measurements in supersonic flows

    NASA Technical Reports Server (NTRS)

    Davidson, David F.; Chang, Albert Y.; Dirosa, Michael D.; Hanson, Ronald K.

    1991-01-01

    Line-of-sight measurements of velocity, temperature, pressure, density, and mass flux were performed in a transient shock tube flow using three laser absorption schemes. All methods employed an intracavity-doubled ring dye laser tuned to an OH transition at 306 nm. In the first scheme, the gas was labeled by 193.3-nm excimer photolysis of H2O, and the passage of the generated OH was detected downstream. In the second method, the laser was tuned at a rate of 3 kHz over the R1(7) and R1(11) line pair, and absorption was simultaneously monitored at 90 and 60 deg with respect to the flow. Velocity was determined from the Doppler shift of the profiles and the temperature from the intensity ratio of the lines. Pressure was determined from both the magnitude of absorption and the collisional broadening. In the third method, the laser wavelength was fixed at a single frequency, and a continuous measurement of velocity and pressure was obtained using the signals from the two beam paths. All methods gave results which compare favorably to calculated values.

  19. Analysis for nonlinear inversion technique developed to estimate depth-distribution of absorption by spatially resolved backscattering measurement

    NASA Astrophysics Data System (ADS)

    Nishida, Kazuhiro; Namita, Takeshi; Kato, Yuji; Shimizu, Koichi

    2015-03-01

    We have proposed a new nonlinear inversion technique to estimate the spatial distribution of the absorption coefficient (μa) in the depth direction of a turbid medium by spatially resolved backscattering measurement. With this technique, we can obtain cross-sectional image of μa as deep as the backscattered light traveled even when the transmitted light through the medium cannot be detected. In this technique, the depth distribution of absorption coefficient is determined by iterative calculation using the spatial path-length distribution (SPD) of traveled photons as a function of source-detector distance. In this calculation, the variance of path-length of many photons in each layer is also required. The SPD and the variance of path-length are obtained by Monte Carlo simulation using a known reduced scattering coefficient (μs'). Therefore, we need to know the μs' of the turbid medium beforehand. We have shown in computer simulation that this technique works well when the μs' is the typical values of mammalian body tissue, or 1.0 /mm. In this study, the accuracy of the μa estimation was analyzed and its dependence on the μs' was clarified quantitatively in various situations expected in practice. 10% deviations in μs' resulted in about 30% error in μa estimation, in average. This suggested that the measurement or the appropriate estimation of μs' is required to utilize the proposed technique effectively. Through this analysis, the effectiveness and the limitation of the newly proposed technique were clarified, and the problems to be solved were identified.

  20. Semi-Empirical Validation of the Cross-Band Relative Absorption Technique for the Measurement of Molecular Mixing Ratios

    NASA Technical Reports Server (NTRS)

    Pliutau, Denis; Prasad, Narasimha S

    2013-01-01

    Studies were performed to carry out semi-empirical validation of a new measurement approach we propose for molecular mixing ratios determination. The approach is based on relative measurements in bands of O2 and other molecules and as such may be best described as cross band relative absorption (CoBRA). . The current validation studies rely upon well verified and established theoretical and experimental databases, satellite data assimilations and modeling codes such as HITRAN, line-by-line radiative transfer model (LBLRTM), and the modern-era retrospective analysis for research and applications (MERRA). The approach holds promise for atmospheric mixing ratio measurements of CO2 and a variety of other molecules currently under investigation for several future satellite lidar missions. One of the advantages of the method is a significant reduction of the temperature sensitivity uncertainties which is illustrated with application to the ASCENDS mission for the measurement of CO2 mixing ratios (XCO2). Additional advantages of the method include the possibility to closely match cross-band weighting function combinations which is harder to achieve using conventional differential absorption techniques and the potential for additional corrections for water vapor and other interferences without using the data from numerical weather prediction (NWP) models.

  1. Measurement of Hydrogen Absorption in Ternary Alloys with Volumetric (Sieverts Loop) Techniques

    SciTech Connect

    Aceves, S.

    2015-10-26

    The Sieverts loop is an inexpensive, robust and reliable methodology for calculating hydrogen absorption in materials [1]. In this approach, we start by storing a sample of the material being tested in the volume Vcell (Figure 1) and initiate the process by producing a high vacuum in the system while the material sample is heated to eliminate (most of) the hydrogen and other impurities previously absorbed. The system typically operates isothermally, with the volume Vref at ambient temperature and the sample at a temperature of interest – high enough to liquefy the alloy for the current application to nuclear fusion.

  2. Optical absorption measurement system

    DOEpatents

    Draggoo, Vaughn G.; Morton, Richard G.; Sawicki, Richard H.; Bissinger, Horst D.

    1989-01-01

    The system of the present invention contemplates a non-intrusive method for measuring the temperature rise of optical elements under high laser power optical loading to determine the absorption coefficient. The method comprises irradiating the optical element with a high average power laser beam, viewing the optical element with an infrared camera to determine the temperature across the optical element and calculating the absorption of the optical element from the temperature.

  3. Pseudorandom Noise Code-Based Technique for Thin Cloud Discrimination with CO2 and O2 Absorption Measurements

    NASA Technical Reports Server (NTRS)

    Campbell, Joel F.; Prasad, Narasimha S.; Flood, Michael A.

    2011-01-01

    NASA Langley Research Center is working on a continuous wave (CW) laser based remote sensing scheme for the detection of CO2 and O2 from space based platforms suitable for ACTIVE SENSING OF CO2 EMISSIONS OVER NIGHTS, DAYS, AND SEASONS (ASCENDS) mission. ASCENDS is a future space-based mission to determine the global distribution of sources and sinks of atmospheric carbon dioxide (CO2). A unique, multi-frequency, intensity modulated CW (IMCW) laser absorption spectrometer (LAS) operating at 1.57 micron for CO2 sensing has been developed. Effective aerosol and cloud discrimination techniques are being investigated in order to determine concentration values with accuracies less than 0.3%. In this paper, we discuss the demonstration of a pseudo noise (PN) code based technique for cloud and aerosol discrimination applications. The possibility of using maximum length (ML)-sequences for range and absorption measurements is investigated. A simple model for accomplishing this objective is formulated, Proof-of-concept experiments carried out using SONAR based LIDAR simulator that was built using simple audio hardware provided promising results for extension into optical wavelengths.

  4. Comparative study on three highly sensitive absorption measurement techniques characterizing lithium niobate over its entire transparent spectral range.

    PubMed

    Leidinger, M; Fieberg, S; Waasem, N; Kühnemann, F; Buse, K; Breunig, I

    2015-08-24

    We employ three highly sensitive spectrometers: a photoacoustic spectrometer, a photothermal common-path interferometer and a whispering-gallery-resonator-based absorption spectrometer, for a comparative study of measuring the absorption coefficient of nominally transparent undoped, congruently grown lithium niobate for ordinarily and extraordinarily polarized light in the wavelength range from 390 to 3800 nm. The absorption coefficient ranges from below 10(-4) cm(-1) up to 2 cm(-1). Furthermore, we measure the absorption at the Urbach tail as well as the multiphonon edge of the material by a standard grating spectrometer and a Fourier-transform infrared spectrometer, providing for the first time an absorption spectrum of the whole transparency window of lithium niobate. The absorption coefficients obtained by the three highly sensitive and independent methods show good agreement.

  5. Applications of the direct photon absorption technique for measuring bone mineral content in vivo. Determination of body composition in vivo

    NASA Technical Reports Server (NTRS)

    Cameron, J. R.

    1972-01-01

    The bone mineral content, BMC, determined by monoenergetic photon absorption technique, of 29 different locations on the long bones and vertebral columns of 24 skeletons was measured. Compressive tests were made on bone from these locations in which the maximum load and maximum stress were measured. Also the ultimate strain, modulus of elasticity and energy absorbed to failure were determined for compact bone from the femoral diaphysis and cancellous bone from the eighth through eleventh thoracic vertebrae. Correlations and predictive relationships between these parameters were examined to investigate the applicability of using the BMC at sites normally measured in vivo, i.e. radius and ulna in estimating the BMC and/or strength of the spine or femoral neck. It was found that the BMC at sites on the same bone were highly correlated r = 0.95 or better; the BMC at sites on different bones were also highly interrelated, r = 0.85. The BMC at various sites on the long bones could be estimated to between 10 and 15 per cent from the BMC of sites on the radius or ulna.

  6. Analysis of diffential absorption lidar technique for measurements of anhydrous hydrogen chloride from solid rocket motors using a deuterium fluoride laser

    NASA Technical Reports Server (NTRS)

    Bair, C. H.; Allario, F.

    1977-01-01

    An active optical technique (differential absorption lidar (DIAL)) for detecting, ranging, and quantifying the concentration of anhydrous HCl contained in the ground cloud emitted by solid rocket motors (SRM) is evaluated. Results are presented of an experiment in which absorption coefficients of HCl were measured for several deuterium fluoride (DF) laser transitions demonstrating for the first time that a close overlap exists between the 2-1 P(3) vibrational transition of the DF laser and the 1-0 P(6) absorption line of HCl, with an absorption coefficient of 5.64 (atm-cm) to the -1 power. These measurements show that the DF laser can be an appropriate radiation source for detecting HCl in a DIAL technique. Development of a mathematical computer model to predict the sensitivity of DIAL for detecting anhydrous HCl in the ground cloud is outlined, and results that assume a commercially available DF laser as the radiation source are presented.

  7. Aerosol Absorption Measurements in MILAGRO.

    NASA Astrophysics Data System (ADS)

    Gaffney, J. S.; Marley, N. A.; Arnott, W. P.; Paredes-Miranda, L.; Barnard, J. C.

    2007-12-01

    to carbonyl- and nitro- functional groups on conjugated and aromatic organic structures (e.g. PAH, and terpene derived products). Using 12-hour fine (0.1-1.0 micron) aerosol samples collected in the field on quartz filters, uv/vis and infrared spectra were obtained in the laboratory using integrating spheres and diffuse reflectance spectroscopy, respectively. An inter-comparison of the "real-time" measurements made by the photo-acoustic, aethalometer and MAAP techniques have been described. In addition, the in situ aethalometer (seven-channel) results are compared with continuous integrating sphere uv-visible spectra to examine the angstrom absorption coefficient variance. These results will be briefly overviewed and the specific posters detailing these results will be highlighted highlighted. This work was performed as part of the Department of Energy's Megacity Aerosol Experiment - Mexico City under the support of the Atmospheric Science Program. "This researchwas supported by the Office of Science (BER), U. S. Department of Energy, Grant No. DE-FG02-07ER64329.

  8. Development of a 2-micron Pulsed Differential Absorption Lidar for Atmospheric CO2 Concentration Measurement by Direct Detection Technique

    NASA Astrophysics Data System (ADS)

    Yu, J.; Singh, U. N.; Petros, M.; Bai, Y.

    2011-12-01

    Researchers at NASA Langley Research Center are developing a 2-micron Pulsed Differential Absorption Lidar instrument for ground and airborne measurements via direct detection method. This instrument will provide an alternate approach to measure atmospheric CO2 concentrations with significant advantages. A high energy pulsed approach provides high-precision measurement capbility by having high signal-to-noise level and unambiguously eliminates the contamination from aerosols and clouds that can bias the IPDA measurement. A key component of the CO2 DIAL system, transceiver, is an existing, airborne ready, robust hardware which can provide 250mJ at 10Hz with double pulse format specifically designed for DIAL instrument. The exact wavelengths of the transceiver are controlled by well defined CW seed laser source to provide the required injection source for generating on-and-off line wavelength pulses sequentially. The compact, rugged, highly reliable transceiver is based on the unique Ho:Tm:YLF high-energy 2-micron pulsed laser technology. All the optical mounts are custom designed and have space heritage. They are designed to be adjustable and lockable and hardened to withstand vibrations that can occur in airborne operation. For the direct detection lidar application, a large primary mirror size is preferred. A 14 inch diameter telescope will be developed for this program. The CO2 DIAL/IPDA system requires many electronic functions to operate. These include diode, RF, seed laser, and PZT drivers; injection seeding detection and control; detector power supplies; and analog inputs to sample various sensors. Under NASA Laser Risk Reduction Program (LRRP), a control unit Compact Laser Electronics (CLE), is developed for the controlling the coherent wind lidar transceiver. Significant modifications and additions are needed to update it for CO2 lidar controls. The data acquisition system was built for ground CO2 measurement demonstration. The software will be updated for

  9. Microwave absorption measurements of melting spherical and nonspherical hydrometeors

    NASA Technical Reports Server (NTRS)

    Hansman, R. J., Jr.

    1986-01-01

    Measurements were made of the absorption behavior of melting and freezing hydrometeors using resonant cavity perturbation techniques at a wavelength of 2.82 cm. Melting ice spheres with equivalent melted diameters between 1.15 and 2.00 mm exhibit a period of strong absorption during melting as predicted by prior theoretical calculations. However, the measured magnitude of the absorption peak exceeds the predicted value. Absorption measuremets of melting oblate and prolate ice ellipsoids also exhibit enhanced absorption during melting.

  10. High temperature measurement of water vapor absorption

    NASA Technical Reports Server (NTRS)

    Keefer, Dennis; Lewis, J. W. L.; Eskridge, Richard

    1985-01-01

    An investigation was undertaken to measure the absorption coefficient, at a wavelength of 10.6 microns, for mixtures of water vapor and a diluent gas at high temperature and pressure. The experimental concept was to create the desired conditions of temperature and pressure in a laser absorption wave, similar to that which would be created in a laser propulsion system. A simplified numerical model was developed to predict the characteristics of the absorption wave and to estimate the laser intensity threshold for initiation. A non-intrusive method for temperature measurement utilizing optical laser-beam deflection (OLD) and optical spark breakdown produced by an excimer laser, was thoroughly investigated and found suitable for the non-equilibrium conditions expected in the wave. Experiments were performed to verify the temperature measurement technique, to screen possible materials for surface initiation of the laser absorption wave and to attempt to initiate an absorption wave using the 1.5 kW carbon dioxide laser. The OLD technique was proven for air and for argon, but spark breakdown could not be produced in helium. It was not possible to initiate a laser absorption wave in mixtures of water and helium or water and argon using the 1.5 kW laser, a result which was consistent with the model prediction.

  11. The continuous measurement of hydrogen chloride in the ambient atmosphere using the dual isotope infrared absorption technique

    NASA Technical Reports Server (NTRS)

    Williams, K. G.

    1974-01-01

    The results of a program to develop a prototype gas filter correlation NDIR analyzer capable of providing the required HCl measurement capability, while maintaining an adequate rejection of any other gases anticipated in the atmosphere are presented. Examples of the performance of the prototype analyzer are presented which show an rms noise equivalent concentration of 0.06 ppm of HCl was achieved while maintaining an electronically determined 10% to 90% time response to gas samples of about 2 seconds. No measureable response was observed to CO2, CO, and H2O while maintaining an adequate rejection of the hydrocarbons, for example CH4 and n-hexane. The experiments were performed which demonstrate that the span stability of the HCl gas filter correlation analyzer is unaffected by the presence of water vapor and which support the belief that the incorporation of a relatively open-volume, multiple path sample cell into the instrument would enable ground station as well as airborne measurements of trace quantities of HCl in the ambient atmosphere to be performed.

  12. A time-resolved single-pass technique for measuring optical absorption coefficients of window materials under 100 GPa shock pressures.

    PubMed

    Li, Jun; Zhou, Xianming; Li, Jiabo

    2008-12-01

    An experimental method was developed to perform time-resolved, single-pass optical absorption measurements and to determine absorption coefficients of window materials under strong shock compression up to approximately 200 GPa. Experimental details are described of (i) a configuration to generate an in situ dynamic, bright, optical source and (ii) a sample assembly with a lithium fluoride plate to essentially eliminate heat transfer from the hot radiator into the specimen and to maintain a constant optical source within the duration of the experiment. Examples of measurements of optical absorption coefficients of several initially transparent single crystal materials at high shock pressures are presented.

  13. Mercury in Environmental and Biological Samples Using Online Combustion with Sequential Atomic Absorption and Fluorescence Measurements: A Direct Comparison of Two Fundamental Techniques in Spectrometry

    ERIC Educational Resources Information Center

    Cizdziel, James V.

    2011-01-01

    In this laboratory experiment, students quantitatively determine the concentration of an element (mercury) in an environmental or biological sample while comparing and contrasting the fundamental techniques of atomic absorption spectrometry (AAS) and atomic fluorescence spectrometry (AFS). A mercury analyzer based on sample combustion,…

  14. Ultrafast transient absorption measurements of heme proteins

    NASA Astrophysics Data System (ADS)

    Ye, Xiong; Demidov, Andrey; Wang, Wei; Christian, James; Champion, Paul

    1998-03-01

    Transient absorption spectra reveal the dynamics and intermediate states of the heme active site after ligand photodissociation, which helps clarify the physical process of ligand dissociation and geminate recombination. To measure the transient absorption spectra, we apply a femtosecond pump-probe technique with frequency resolved detection using a multichannel diode array. The femtosecond pulse output from a regenerative laser amplifier system is split in two; one beam pumps the optical parametric amplifier to produce a tunable wavelength pump pulse, the other beam generates a white light continuum that is varied in time with respect to pump pulse and probe the transient absorbance of the sample. We make a comparative study of myoglobin with different ligands, mutants and pH conditions.

  15. Modeling optical absorption for thermoreflectance measurements

    NASA Astrophysics Data System (ADS)

    Yang, Jia; Ziade, Elbara; Schmidt, Aaron J.

    2016-03-01

    Optical pump-probe techniques based on thermoreflectance, such as time domain thermoreflectance and frequency domain thermoreflectance (FDTR), have been widely used to characterize the thermal conductivity of thin films and the thermal conductance across interfaces. These techniques typically use a transducer layer to absorb the pump light and improve the thermoreflectance signal. The transducer, however, complicates the interpretation of the measured signal because the approximation that all the energy from the pump beam is deposited at the transducer surface is not always accurate. In this paper, we consider the effect of laser absorption in the top layer of a multilayer sample, and derive an analytical solution for the thermoreflectance signal in the diffusion regime based on volumetric heating. We analyze the measurement sensitivity to the pump absorption depth for transducers with different thermal conductivities, and investigate the additional effect of probe laser penetration depth on the measured signal. We validate our model using FDTR measurements on 490 nm thick amorphous silicon films deposited on fused silica and silicon substrates.

  16. Non-Heme Iron Absorption and Utilization from Typical Whole Chinese Diets in Young Chinese Urban Men Measured by a Double-Labeled Stable Isotope Technique

    PubMed Central

    Yang, Lichen; Zhang, Yuhui; Wang, Jun; Huang, Zhengwu; Gou, Lingyan; Wang, Zhilin; Ren, Tongxiang; Piao, Jianhua; Yang, Xiaoguang

    2016-01-01

    Background This study was to observe the non-heme iron absorption and biological utilization from typical whole Chinese diets in young Chinese healthy urban men, and to observe if the iron absorption and utilization could be affected by the staple food patterns of Southern and Northern China. Materials and Methods Twenty-two young urban men aged 18–24 years were recruited and randomly assigned to two groups in which the staple food was rice and steamed buns, respectively. Each subject received 3 meals containing approximately 3.25 mg stable 57FeSO4 (the ratio of 57Fe content in breakfast, lunch and dinner was 1:2:2) daily for 2 consecutive days. In addition, approximately 2.4 mg 58FeSO4 was administered intravenously to each subject at 30–60 min after dinner each day. Blood samples were collected from each subject to measure the enrichment of the 57Fe and 58Fe. Fourteen days after the experimental diet, non-heme iron absorption was assessed by measuring 57Fe incorporation into red blood cells, and absorbed iron utilization was determined according to the red blood cell incorporation of intravenously infused 58Fe SO4. Results Non-heme iron intake values overall, and in the rice and steamed buns groups were 12.8 ±2.1, 11.3±1.3 and 14.3±1.5 mg, respectively; the mean 57Fe absorption rates were 11±7%, 13±7%, and 8±4%, respectively; and the mean infused 58Fe utilization rates were 85±8%, 84±6%, and 85±10%, respectively. There was no significantly difference in the iron intakes, and 57Fe absorption and infused 58Fe utilization rates between rice and steamed buns groups (all P>0.05). Conclusion We present the non-heme iron absorption and utilization rates from typical whole Chinese diets among young Chinese healthy urban men, which was not affected by the representative staple food patterns of Southern and Northern China. This study will provide a basis for the setting of Chinese iron DRIs. PMID:27099954

  17. Atmospheric Measurements by Cavity Enhanced Absorption Spectroscopy

    NASA Astrophysics Data System (ADS)

    Yi, Hongming; Wu, Tao; Coeur-Tourneur, Cécile; Fertein, Eric; Gao, Xiaoming; Zhao, Weixiong; Zhang, Weijun; Chen, Weidong

    2015-04-01

    Since the last decade, atmospheric environmental monitoring has benefited from the development of novel spectroscopic measurement techniques owing to the significant breakthroughs in photonic technology from the UV to the infrared spectral domain [1]. In this presentation, we will overview our recent development and applications of cavity enhanced absorption spectroscopy techniques for in situ optical monitoring of chemically reactive atmospheric species (such as HONO, NO3, NO2, N2O5) in intensive campaigns [2] and/or in smog chamber studies [3]. These field deployments demonstrated that modern photonic technologies (newly emergent light sources combined with high sensitivity spectroscopic techniques) can provide a useful tool to improve our understanding of tropospheric chemical processes which affect climate, air quality, and the spread of pollution. Experimental detail and preliminary results will be presented. Acknowledgements. The financial support from the French Agence Nationale de la Recherche (ANR) under the NexCILAS (ANR-11-NS09-0002) and the CaPPA (ANR-10-LABX-005) contracts is acknowledged. References [1] X. Cui, C. Lengignon, T. Wu, W. Zhao, G. Wysocki, E. Fertein, C. Coeur, A. Cassez,L. Croisé, W. Chen, et al., "Photonic Sensing of the Atmosphere by absorption spectroscopy", J. Quant. Spectrosc. Rad. Transfer 113 (2012) 1300-1316 [2] T. Wu, Q. Zha, W. Chen, Z. XU, T. Wang, X. He, "Development and deployment of a cavity enhanced UV-LED spectrometer for measurements of atmospheric HONO and NO2 in Hong Kong", Atmos. Environ. 95 (2014) 544-551 [3] T. Wu, C. Coeur-Tourneur, G. Dhont,A. Cassez, E. Fertein, X. He, W. Chen,"Application of IBBCEAS to kinetic study of NO3 radical formation from O3 + NO2 reaction in an atmospheric simulation chamber", J. Quant. Spectrosc. Rad. Transfer 133 (2014)199-205

  18. Remote Raman measurement techniques

    NASA Technical Reports Server (NTRS)

    Leonard, D. A.

    1981-01-01

    The use of laser Raman measurement techniques in remote sensing applications is surveyed. A feasibility index is defined as a means to characterize the practicality of a given remote Raman measurement application. Specific applications of Raman scattering to the measurement of atmospheric water vapor profiles, methane plumes from liquid natural gas spills, and subsurface ocean temperature profiles are described. This paper will survey the use of laser Raman measurement techniques in remote sensing applications using as examples specific systems that the Computer Genetics Corporation (CGC) group has developed and engineered.

  19. Novel absorption detection techniques for capillary electrophoresis

    SciTech Connect

    Xue, Yongjun

    1994-07-27

    Capillary electrophoresis (CE) has emerged as one of the most versatile separation methods. However, efficient separation is not sufficient unless coupled to adequate detection. The narrow inner diameter (I.D.) of the capillary column raises a big challenge to detection methods. For UV-vis absorption detection, the concentration sensitivity is only at the μM level. Most commercial CE instruments are equipped with incoherent UV-vis lamps. Low-brightness, instability and inefficient coupling of the light source with the capillary limit the further improvement of UV-vis absorption detection in CE. The goals of this research have been to show the utility of laser-based absorption detection. The approaches involve: on-column double-beam laser absorption detection and its application to the detection of small ions and proteins, and absorption detection with the bubble-shaped flow cell.

  20. Sensorimotor System Measurement Techniques

    PubMed Central

    Riemann, Bryan L.; Myers, Joseph B.; Lephart, Scott M.

    2002-01-01

    Objective: To provide an overview of currently available sensorimotor assessment techniques. Data Sources: We drew information from an extensive review of the scientific literature conducted in the areas of proprioception, neuromuscular control, and motor control measurement. Literature searches were conducted using MEDLINE for the years 1965 to 1999 with the key words proprioception, somatosensory evoked potentials, nerve conduction testing, electromyography, muscle dynamometry, isometric, isokinetic, kinetic, kinematic, posture, equilibrium, balance, stiffness, neuromuscular, sensorimotor, and measurement. Additional sources were collected using the reference lists of identified articles. Data Synthesis: Sensorimotor measurement techniques are discussed with reference to the underlying physiologic mechanisms, influential factors and locations of the variable within the system, clinical research questions, limitations of the measurement technique, and directions for future research. Conclusions/Recommendations: The complex interactions and relationships among the individual components of the sensorimotor system make measuring and analyzing specific characteristics and functions difficult. Additionally, the specific assessment techniques used to measure a variable can influence attained results. Optimizing the application of sensorimotor research to clinical settings can, therefore, be best accomplished through the use of common nomenclature to describe underlying physiologic mechanisms and specific measurement techniques. PMID:16558672

  1. The attribute measurement technique

    SciTech Connect

    Macarthur, Duncan W; Langner, Diana; Smith, Morag; Thron, Jonathan; Razinkov, Sergey; Livke, Alexander

    2010-01-01

    Any verification measurement performed on potentially classified nuclear material must satisfy two seemingly contradictory constraints. First and foremost, no classified information can be released. At the same time, the monitoring party must have confidence in the veracity of the measurement. An information barrier (IB) is included in the measurement system to protect the potentially classified information while allowing sufficient information transfer to occur for the monitoring party to gain confidence that the material being measured is consistent with the host's declarations, concerning that material. The attribute measurement technique incorporates an IB and addresses both concerns by measuring several attributes of the nuclear material and displaying unclassified results through green (indicating that the material does possess the specified attribute) and red (indicating that the material does not possess the specified attribute) lights. The attribute measurement technique has been implemented in the AVNG, an attribute measuring system described in other presentations at this conference. In this presentation, we will discuss four techniques used in the AVNG: (1) the 1B, (2) the attribute measurement technique, (3) the use of open and secure modes to increase confidence in the displayed results, and (4) the joint design as a method for addressing both host and monitor needs.

  2. Differential absorption lidar measurements of atmospheric temperature and pressure profiles

    NASA Technical Reports Server (NTRS)

    Korb, C. L.

    1981-01-01

    The theory and methodology of using differential absorption lidar techniques for the remote measurement of atmospheric pressure profiles, surface pressure, and temperature profiles from ground, air, and space-based platforms are presented. Pressure measurements are effected by means of high resolution measurement of absorption at the edges of the oxygen A band lines where absorption is pressure dependent due to collisional line broadening. Temperature is assessed using measurements of the absorption at the center of the oxygen A band line originating from a quantum state with high ground state energy. The population of the state is temperature dependent, allowing determination of the temperature through the Boltzmann term. The results of simulations of the techniques using Voigt profile and variational analysis are reported for ground-based, airborne, and Shuttle-based systems. Accuracies in the 0.5-1.0 K and 0.1-0.3% range are projected.

  3. Optimization of the steady neutron source technique for absorption cross section measurement by using an 124Sb-Be neutron source

    NASA Astrophysics Data System (ADS)

    Sun, Jing; Gardner, Robin P.

    2004-01-01

    An improved experimental approach has been developed to determine thermal neutron absorption cross sections. It uses an 124Sb-Be neutron source which has an average neutron energy of only about 12 keV. It can be moderated in either a water tank or a paraffin filled box and can be used for aqueous or powder samples. This new design is first optimized by MCNP simulation and then benchmarked and calibrated with experiments to verify the simulations and realize the predicted improved measurement sensitivity and reproducibility. The 124Sb-Be source device is from 1.35 to 1.71 times more sensitive than the previous method based on the use of a 252Cf source.

  4. Novel Diffusivity Measurement Technique

    NASA Technical Reports Server (NTRS)

    Rashidnia, Nasser

    2001-01-01

    A common-path interferometer (CPI) system was developed to measure the diffusivity of liquid pairs. The CPI is an optical technique that can be used to measure changes in the gradient of the refraction index of transparent materials. This system uses a shearing interferometer that shares the same optical path from a laser light source to the final imaging plane. Hence, the molecular diffusion coefficient of liquids can be determined using the physical relations between changes in the optical path length and the liquid phase properties. The data obtained with this interferometer were compared with similar results from other techniques and demonstrated that the instrument is superior in measuring the diffusivity of miscible liquids while keeping the system very compact and robust. CPI can also be used for studies in interface dynamics and other diffusion-dominated-process applications.

  5. Ultrasensitive near-infrared integrated cavity output spectroscopy technique for detection of CO at 1.57 μm: new sensitivity limits for absorption measurements in passive optical cavities

    NASA Astrophysics Data System (ADS)

    Engel, Gregory S.; Drisdell, Walter S.; Keutsch, Frank N.; Moyer, Elisabeth J.; Anderson, James G.

    2006-12-01

    A robust absorption spectrometer using the off-axis integrated cavity output spectroscopy (ICOS) technique in a passive cavity is presented. The observed sensitivity, conceptually the detection threshold for the absorption cross section (cm2) multiplied by the concentration (cm-3) and normalized by the averaging time, is measured to be 1.9×10-12 (1/cm√Hz). This high sensitivity arises from using the optical cavity to amplify the observed path length in the spectrometer while avoiding cavity resonances by careful design of the spot pattern within the cavity. The instrument is ideally suited for routine monitoring of trace gases in the near-infrared region. A spectrum showing ambient carbon monoxide at 1.57 μm is presented.

  6. Integrating Sphere Microscopy for Direct Absorption Measurements of Single Nanostructures

    PubMed Central

    2017-01-01

    Nanoscale materials are promising for optoelectronic devices because their physical dimensions are on the order of the wavelength of light. This leads to a variety of complex optical phenomena that, for instance, enhance absorption and emission. However, quantifying the performance of these nanoscale devices frequently requires measuring absolute absorption at the nanoscale, and remarkably, there is no general method capable of doing so directly. Here, we present such a method based on an integrating sphere but modified to achieve submicron spatial resolution. We explore the limits of this technique by using it to measure spatial and spectral absorptance profiles on a wide variety of nanoscale systems, including different combinations of weakly and strongly absorbing and scattering nanomaterials (Si and GaAs nanowires, Au nanoparticles). This measurement technique provides quantitative information about local optical properties that are crucial for improving any optoelectronic device with nanoscale dimensions or nanoscale surface texturing. PMID:28056171

  7. Integrating Sphere Microscopy for Direct Absorption Measurements of Single Nanostructures.

    PubMed

    Mann, Sander A; Sciacca, Beniamino; Zhang, Yunyan; Wang, Jia; Kontoleta, Evgenia; Liu, Huiyun; Garnett, Erik C

    2017-02-28

    Nanoscale materials are promising for optoelectronic devices because their physical dimensions are on the order of the wavelength of light. This leads to a variety of complex optical phenomena that, for instance, enhance absorption and emission. However, quantifying the performance of these nanoscale devices frequently requires measuring absolute absorption at the nanoscale, and remarkably, there is no general method capable of doing so directly. Here, we present such a method based on an integrating sphere but modified to achieve submicron spatial resolution. We explore the limits of this technique by using it to measure spatial and spectral absorptance profiles on a wide variety of nanoscale systems, including different combinations of weakly and strongly absorbing and scattering nanomaterials (Si and GaAs nanowires, Au nanoparticles). This measurement technique provides quantitative information about local optical properties that are crucial for improving any optoelectronic device with nanoscale dimensions or nanoscale surface texturing.

  8. New analytical technique for carbon dioxide absorption solvents

    SciTech Connect

    Pouryousefi, F.; Idem, R.O.

    2008-02-15

    The densities and refractive indices of two binary systems (water + MEA and water + MDEA) and three ternary systems (water + MEA + CO{sub 2}, water + MDEA + CO{sub 2}, and water + MEA + MDEA) used for carbon dioxide (CO{sub 2}) capture were measured over the range of compositions of the aqueous alkanolamine(s) used for CO{sub 2} absorption at temperatures from 295 to 338 K. Experimental densities were modeled empirically, while the experimental refractive indices were modeled using well-established models from the known values of their pure-component densities and refractive indices. The density and Gladstone-Dale refractive index models were then used to obtain the compositions of unknown samples of the binary and ternary systems by simultaneous solution of the density and refractive index equations. The results from this technique have been compared with HPLC (high-performance liquid chromatography) results, while a third independent technique (acid-base titration) was used to verify the results. The results show that the systems' compositions obtained from the simple and easy-to-use refractive index/density technique were very comparable to the expensive and laborious HPLC/titration techniques, suggesting that the refractive index/density technique can be used to replace existing methods for analysis of fresh or nondegraded, CO{sub 2}-loaded, single and mixed alkanolamine solutions.

  9. Aerodynamic measurement techniques. [laser based diagnostic techniques

    NASA Technical Reports Server (NTRS)

    Hunter, W. W., Jr.

    1976-01-01

    Laser characteristics of intensity, monochromatic, spatial coherence, and temporal coherence were developed to advance laser based diagnostic techniques for aerodynamic related research. Two broad categories of visualization and optical measurements were considered, and three techniques received significant attention. These are holography, laser velocimetry, and Raman scattering. Examples of the quantitative laser velocimeter and Raman scattering measurements of velocity, temperature, and density indicated the potential of these nonintrusive techniques.

  10. Plasma absorption evidence via chirped pulse spectral transmission measurements

    SciTech Connect

    Jedrkiewicz, Ottavia; Minardi, Stefano; Couairon, Arnaud; Jukna, Vytautas; Selva, Marco; Di Trapani, Paolo

    2015-06-08

    This work aims at highlighting the plasma generation dynamics and absorption when a Bessel beam propagates in glass. We developed a simple diagnostics allowing us to retrieve clear indications of the formation of the plasma in the material, thanks to transmission measurements in the angular and wavelength domains. This technique featured by the use of a single chirped pulse having the role of pump and probe simultaneously leads to results showing the plasma nonlinear absorption effect on the trailing part of the pulse, thanks to the spectral-temporal correspondence in the measured signal, which is also confirmed by numerical simulations.

  11. OH measurement by laser light absorption

    NASA Technical Reports Server (NTRS)

    Perner, D.

    1986-01-01

    Since the first attempt to measure atmospheric hydroxyl radicals by optical absorption in 1975 (Perner et al., 1976) this method has been continuously developed further and its major obstacles and limitations are known today. The laser beam needs to be expanded in order to reduce the beam divergence. At the same time the energy density of the laser beam which produces OH via ozone photolysis is reduced to such an extent that the self-produced OH concentration ranges well below the atmospheric value. Atmospheric absorptions should be observed over a wide spectral range so that not only the OH radicals are properly identified by several rotational lines but their absorption can be corrected for interfering absorptions from other air constituents as SO2, CH2O, CS2, etc., which can be identified in a wide spectral range with more confidence. Air turbulence demands fast spectral scanning or probing on and off the absorption line. Energy requirements should be kept small in field operations. In the experiment frequency doubled dye laser pulses at 308 nm are produced. The picosecond light pulses are expected to show a smooth profile (light intensity against wavelength) which will be broadened to the required spectral width according to the uncertainty principle. The pump laser will be an optoacoustically modulated Nd:YAG laser.

  12. Measurements of scattering and absorption in mammalian cell suspensions

    SciTech Connect

    Mourant, J.R.; Johnson, T.M.; Freyer, J.P.

    1996-03-01

    During the past several years a range of spectroscopies, including fluorescence and elastic-scatter spectroscopy, have been investigated for optically based detection of cancer and other tissue pathologies. Both elastic-scatter and fluorescence signals depend, in part, on scattering and absorption properties of the cells in the tissue. Therefore an understanding of the scattering and absorption properties of cells is a necessary prerequisite for understanding and developing these techniques. Cell suspensions provide a simple model with which to begin studying the absorption and scattering properties of cells. In this study we have made preliminary measurements of the scattering and absorption properties of suspensions of mouse mammary carcinoma cells (EMT6) over a broad wavelength range (380 nm to 800 nm).

  13. Pulsed Airborne Lidar Measurements of C02 Column Absorption

    NASA Technical Reports Server (NTRS)

    Abshire, James B.; Riris, Haris; Allan, Graham R.; Weaver, Clark J.; Mao, Jianping; Sun, Xiaoli; Hasselbrack, William E.; Rodriquez, Michael; Browell, Edward V.

    2011-01-01

    We report on airborne lidar measurements of atmospheric CO2 column density for an approach being developed as a candidate for NASA's ASCENDS mission. It uses a pulsed dual-wavelength lidar measurement based on the integrated path differential absorption (IPDA) technique. We demonstrated the approach using the CO2 measurement from aircraft in July and August 2009 over four locations. The results show clear CO2 line shape and absorption signals, which follow the expected changes with aircraft altitude from 3 to 13 km. The 2009 measurements have been analyzed in detail and the results show approx.1 ppm random errors for 8-10 km altitudes and approx.30 sec averaging times. Airborne measurements were also made in 2010 with stronger signals and initial analysis shows approx. 0.3 ppm random errors for 80 sec averaging times for measurements at altitudes> 6 km.

  14. Automation of long-path absorption cell measurements.

    PubMed

    Watkins, W R; Dixon, R G

    1979-01-01

    Recent advances have been made in the operation of long-path absorption cells which make them easier to align and improve the accuracy of measurements made with them. Only one person is required now for routine measurements of low absorption coefficients of atmospheric absorbers. Unique gear designs for the adjustment of the cell mirrors are described which utilize low-torque linear drives and make possible rapid changes in pathlength and precision repositioning of the cell output beam at long pathlengths. Automation of cell operation by the use of remote Selsyn controls is described. Several techniques are discussed for precision optical alignment of long-path absorption cells, including the use of infrared radiation sources. The system accuracy which results from these refinements in operation is included.

  15. Transient Infrared Measurement of Laser Absorption Properties of Porous Materials

    NASA Astrophysics Data System (ADS)

    Marynowicz, Andrzej

    2016-06-01

    The infrared thermography measurements of porous building materials have become more frequent in recent years. Many accompanying techniques for the thermal field generation have been developed, including one based on laser radiation. This work presents a simple optimization technique for estimation of the laser beam absorption for selected porous building materials, namely clinker brick and cement mortar. The transient temperature measurements were performed with the use of infrared camera during laser-induced heating-up of the samples' surfaces. As the results, the absorbed fractions of the incident laser beam together with its shape parameter are reported.

  16. Deconvolution of CPM absorption spectra: A new technique

    NASA Astrophysics Data System (ADS)

    Jensen, Pablo

    1990-12-01

    We have found a new technique for deconvoluting absorption spectra obtained with the constant photocurrent method on hydrogenated amorphous silicon samples. We have shown that our method is simpler and more accurate than those used until now. Finally, examples of spectra deconvolution for one sample after various thermal treatments are provided.

  17. Direct absorption measurements in thin rods and optical fibers

    NASA Astrophysics Data System (ADS)

    Mühlig, Christian; Bublitz, Simon; Lorenz, Martin

    2015-11-01

    We report on the first realization of direct absorption measurements in thin rods and optical fibers using the laser induced deflection (LID) technique. Typically, along the fiber processing chain more or less technology steps are able to introduce additional losses to the starting material. After the final processing, the fibers are commonly characterized regarding losses using the so-called cut-back technique in combination with spectrometers. This, however, only serves for a total loss determination. For optimization of the fiber processing, it would be of great interest to not only distinguish between different loss mechanisms but also have a better understanding of possible causes. For measuring the absorption losses along the fiber processing, a particular concept for the LID technique is introduced and requirements, calibration procedure as well as first results are presented. It allows to measure thin rods, e.g. during preform manufacturing, as well as optical fibers. In addition, the results show the prospects to also apply the new concept to topics like characterizing unwanted absorption after fiber splicing or Bragg grating inscription.

  18. Measurements of scattering and absorption changes in muscle and brain.

    PubMed Central

    Gratton, E; Fantini, S; Franceschini, M A; Gratton, G; Fabiani, M

    1997-01-01

    Non-invasive techniques for the study of human brain function based on changes of the haemoglobin content or on changes of haemoglobin saturation have recently been proposed. Among the new methods, near-infrared transmission measurements may have significant advantages and complement well-established methods such as functional magnetic resonance imaging and positron emission tomography. Near-infrared measurements can be very fast, comparable in speed to electrophysiological measurements, bur are better localized. We will present the demonstration of measurements of millisecond signals due to brain activity in humans following stimulation of the visual cortex. However, major unresolved questions remain about the origin of the signals observed. Optical measurements on exposed cortex in animals show that both the absorption and the scattering coefficient are affected by neural activity. Model calculations show that the signals we detected may originate from rapid changes of the scattering coefficient in a region about 1 to 2 cm below the scalp. We discuss our measurement protocol, which is based on a frequency-domain instrument, and the algorithm to separate the absorption from the scattering contribution in the overall response. Our method produces excellent separation between scattering and absorption in relatively homogeneous masses such as large muscles. The extrapolation of our measurement protocol to a complex structure such as the human head is critically evaluated. PMID:9232861

  19. In vivo absorption spectroscopy for absolute measurement.

    PubMed

    Furukawa, Hiromitsu; Fukuda, Takashi

    2012-10-01

    In in vivo spectroscopy, there are differences between individual subjects in parameters such as tissue scattering and sample concentration. We propose a method that can provide the absolute value of a particular substance concentration, independent of these individual differences. Thus, it is not necessary to use the typical statistical calibration curve, which assumes an average level of scattering and an averaged concentration over individual subjects. This method is expected to greatly reduce the difficulties encountered during in vivo measurements. As an example, for in vivo absorption spectroscopy, the method was applied to the reflectance measurement in retinal vessels to monitor their oxygen saturation levels. This method was then validated by applying it to the tissue phantom under a variety of absorbance values and scattering efficiencies.

  20. Remote Attitude Measurement Techniques.

    DTIC Science & Technology

    1982-12-01

    Engineering , New Jersey Institute of Technology. Published by University Microfilms International- Plibi R92,3 19. KCEY WORDS (Continue on reverse side...of the sensor is expressed in terms of a probabilistic matrix. The engineering considerations for liplementing a Remote Attitude Measure- ment...doctoral research. While in residence at Ft. Monmouth, the author served as the project engineer on an exploratory development model of a state of the art

  1. Measurement of Zinc Absorption From Meals: Comparison of Extrinsi Zinc Labeling and Independent Measurements of Dietary Zinc Absorption

    PubMed Central

    Sheng, Xiao-Yang; Hambidge, K. Michael; Miller, Leland V.; Westcott, Jamie E.; Lei, Sian; Krebs, Nancy F.

    2017-01-01

    Background Extrinsic labeling techniques are typically used to measure fractional absorption of zinc (FAZextrinsic) but none have been adequately evaluated. Objective To compare determination of the quantity of zinc absorbed (TAZextrinsic) using measurements of FAZextrinsic with results of simultaneous determinations of dietary zinc absorbed (TAZmetabolic) that are not dependent on labeling ingested food with an extrinsic tracer (modified metabolic balance technique). Design 70Zn was administered orally with all meals for 6 consecutive days to 21 healthy, free-living adult women consuming a constant diet. 68Zn and 67Zn were administered intravenously. FAZextrinsic was measured using a dual isotope tracer ratio technique and multiplied by dietary zinc to give TAZextrinsic TAZmetabolic was determined by addition of net absorption of zinc and endogenous fecal zinc, the latter determined by an isotope dilution technique. Results TAZextrinsic and TAZmetabolic were 3.0 ± 1.1mg/day and 3.1 ± 1.1 mg/day respectively, paired t-test p = 0.492. The correlation coefficient for TAZextrinsic and TAZmetabolic was 0.91, and for FAZextrinsic and FAZmetabolic was 0.95. A Bland Altman analysis indicated a bias of 0.07, and the limits of agreement of −0.86 to 1.01 for TAZextrinsic and TAZmatabolic Conclusion These results from two independent methods provide reasonable validation of our extrinsic labeling technique for a wide range of composite diets. PMID:20209474

  2. ABSORPTION MEASURE DISTRIBUTION IN Mrk 509

    SciTech Connect

    Adhikari, T. P.; Różańska, A.; Sobolewska, M.; Czerny, B.

    2015-12-20

    In this paper we model the observed absorption measure distribution (AMD) in Mrk 509, which spans three orders of magnitude in ionization level with a single-zone absorber in pressure equilibrium. AMD is usually constructed from observations of narrow absorption lines in radio-quiet active galaxies with warm absorbers. We study the properties of the warm absorber in Mrk 509 using recently published broadband spectral energy distribution observed with different instruments. This spectrum is an input in radiative transfer computations with full photoionization treatment using the titan code. We show that the simplest way to fully reproduce the shape of AMD is to assume that the warm absorber is a single zone under constant total pressure. With this assumption, we found theoretical AMD that matches the observed AMD determined on the basis of the 600 ks reflection grating spectrometer XMM-Newton spectrum of Mrk 509. The softness of the source spectrum and the important role of the free–free emission breaks the usual degeneracy in the ionization state calculations, and the explicit dependence of the depths of AMD dips on density open a new path to the density diagnostic for the warm absorber. In Mrk 509, the implied density is of the order of 10{sup 8} cm{sup −3}.

  3. Helium II level measurement techniques

    NASA Astrophysics Data System (ADS)

    Celik, D.; Hilton, D. K.; Zhang, T.; Van Sciver, S. W.

    2001-05-01

    In this paper, a survey of cryogenic liquid level measurement techniques applicable to superfluid helium (He II) is given. The survey includes both continuous and discrete measurement techniques. A number of different probes and controlling circuits for this purpose have been described in the literature. They fall into one of the following categories: capacitive liquid level gauges, superconducting wire liquid level gauges, thermodynamic (heat transfer-based) liquid level gauges, resistive gauges, ultrasound and transmission line-based level detectors. The present paper reviews these techniques and their suitability for He II service. In addition to these methods, techniques for measuring the total liquid volume and mass gauging are also discussed.

  4. Solar absorptance measurements in space on operational spacecraft

    NASA Astrophysics Data System (ADS)

    Babel, Hank W.; Jones, Cherie A.; Wilkes, Donald R.; Linton, Roger C.

    1995-07-01

    Spacecraft hardware such as radiators requires the maintenance of solar absorptance within tight bounds for their design life. Such hardware is sized in part based on the beginning- and end-of-life absorptance. It has been difficult to make accurate end-of-life determinations based on either ground based data or flight data. The synergistic effect of atomic oxygen, ultraviolet radiation, and contamination has made it difficult to duplicate space exposures in the laboratory. The absorptance of flight exposed samples brought back to earth are not representative of the conditions in space because of changes brought about by exposure to air. This paper proposes to augment the current in-space monitoring techniques with periodic, in- space, direct measurements of the solar absorptance on operational hardware. NASA funded AZ Technology to develop a portable, space-rated device similar to the LPSR-200 portable spectroreflectometer, a space portable spectroreflectometer (SPSR). This instrument is robotically compatible and can be run using spacecraft power or batteries. The instrument also has measurement storage capacity for later retrieval and evaluation. Although extensive development work has already been completed, authorization to build a unit for a flight experiment has not been received. The Russians have expressed an interest in having absorptance measurements made on their MIR I Space Station as part of the NASA/MIR flight experiments. Proposals are currently being made to obtain authorization for the construction and use of SPSR on NASA/MIR flight experiments, to help mitigate potential problems for the International Space Station Alpha (ISSA).

  5. Diode laser absorption tomography using data compression techniques

    NASA Astrophysics Data System (ADS)

    Lindstrom, Chad; Tam, Chung-Jen; Givens, Ryan; Davis, Doug; Williams, Skip

    2008-02-01

    Tunable diode laser absorption spectroscopy (TDLAS) shows promise for in situ monitoring in high-speed flows. However, the dynamic nature of typical flows of supersonic combustors, gas turbine engines and augmenters can also lead to inhomogenities that cannot be captured by a single line-of-sight TDLAS measurement. Instead, multiple measurements varied over several spatial locations need to be made. In the current study, shock train structure in the isolator section of the Research Cell 18 supersonic combustion facility at Wright-Patterson AFB is measured. Although only two view angles are available for measurement, multiple absorption features along with a priori computational fluid dynamics (CFD) simulations enable estimates of two dimensional flow features to be formed. Vector quantization/kmeans data clustering is used to identify key flow features from the temporal history of the raw sinograms. Through the use of multiple absorption features that are measured nearly simultaneously, an approximate two-dimensional image can be formed. This image can be further refined through the use of an optimal set of basis functions that can be derived from a set of CFD simulations that describes the flow shapes.

  6. Molar Absorptivity Measurements in Absorbing Solvents: Impact on Solvent Absorptivity Values.

    PubMed

    Bohman, Ariel; Arnold, Mark A

    2016-10-18

    Molar absorptivity is a fundamental molecular property that quantifies absorption strength as a function of wavelength. Absolute measurements of molar absorptivity demand accounting for all mechanisms of light attenuation, including reflective losses at interfaces associated with the sample. Ideally, such measurements are performed in nonabsorbing solvents and reflective losses can be determined in a straightforward manner from Fresnel equations or effectively accounted for by path length difference methods. At near-infrared wavelengths, however, many solvents, including water, are absorbing which complicates the quantification of reflective losses. Here, generalized equations are developed for calculating absolute molar absorptivities of neat liquids wherein the dependency of reflective loss on absorption properties of the liquid are considered explicitly. The resulting equations are used to characterize sensitivity of absolute molar absorptivity measurements for solvents to the absorption strength of the solvent as well as the path length of the measurement. Methods are derived from these equations to properly account for reflective losses in general and the effectiveness of these methods is demonstrated for absolute molar absorptivity measurements for water over the combination region (5000-4000 cm(-1)) of the near-infrared spectrum. Results indicate that ignoring solvent absorption effects can incorporate wide ranging systematic errors depending upon experimental conditions. As an example, systematic errors range from 0 to 10% for common conditions used in the measurement of absolute molar absorptivity of water over the combination region of the near-infrared spectrum.

  7. Digital Techniques for Laboratory Measurements

    ERIC Educational Resources Information Center

    Dart, S. Leonard

    1975-01-01

    Describes techniques and equipment intended to both improve laboratory measurements and also form a background for more advanced work by introducing the concepts of electronic and digital circuits. (GS)

  8. Atmospheric particulate absorption and black carbon measurement.

    PubMed

    Lindberg, J D; Douglass, R E; Garvey, D M

    1999-04-20

    It is convenient to measure the optical attenuation A of the combination of a layer of atmospheric particulate matter and the quartz fiber filter on which it has been collected. The problem of relating A to the absorption and scattering coefficients k and s of the particulate matter itself is treated as a problem in diffuse reflectance spectroscopy using the KubelkaMunk theory. The results show that although, in general, A is a nonlinear function strongly dependent on both s and k, for a limited range of s and sample thickness d, A can be a practically linear function of k. Fortunately, this range includes that common to atmospheric particulate samples. Furthermore, it is shown that if the filter's reflectance is sufficiently high, A can be nearly independent of s. This is in agreement with experimental and, for the limiting case when the substrate filter reflectance is unity, theoretical results obtained by other researchers. Use of such measurements of A as a means of determining the black carbon mass loading C on a filter is also investigated. It is shown that when the black carbon mass fraction f(c) is high, as it is for samples collected in large urban areas, A is a predictable and practically linear function of C. However, when f(c) is low, as it is for many rural locations, then the slope of the function A(C) is strongly dependent on f(c), leading to possible overestimates of C. This problem can be alleviated by making the measurement of A at near-infrared wavelengths rather than in the visible spectrum.

  9. Ultraviolet absorption: Experiment MA-059. [measurement of atmospheric species concentrations

    NASA Technical Reports Server (NTRS)

    Donahue, T. M.; Hudson, R. D.; Rawlins, W. T.; Anderson, J.; Kaufman, F.; Mcelroy, M. B.

    1977-01-01

    A technique devised to permit the measurement of atmospheric species concentrations is described. This technique involves the application of atomic absorption spectroscopy and the quantitative observation of resonance fluorescence in which atomic or molecular species scatter resonance radiation from a light source into a detector. A beam of atomic oxygen and atomic nitrogen resonance radiation, strong unabsorbable oxygen and nitrogen radiation, and visual radiation was sent from Apollo to Soyuz. The density of atomic oxygen and atomic nitrogen between the two spacecraft was measured by observing the amount of resonance radiation absorbed when the line joining Apollo and Soyuz was perpendicular to their velocity with respect to the ambient atmosphere. Results of postflight analysis of the resonance fluorescence data are discussed.

  10. Measurement of atmospheric precipitable water using a solar radiometer. [water vapor absorption effects

    NASA Technical Reports Server (NTRS)

    Pitts, D. E.; Dillinger, A. E.; Mcallum, W. E.

    1974-01-01

    A technique is described and tested that allows the determination of atmospheric precipitable water from two measurements of solar intensity: one in a water-vapor absorption band and another in a nearby spectral region unaffected by water vapor.

  11. Pseudopotential calculations and photothermal lensing measurements of two-photon absorption in solids

    SciTech Connect

    White, W.T. III

    1985-11-04

    We have studied two-photon absorption in solids theoretically and experimentally. We have shown that it is possible to use accurate band structure techniques to compute two-photon absorption spectra within 15% of measured values in a wide band-gap material, ZnS. The empirical pseudopotential technique that we used is significantly more accurate than previous models of two-photon absorption in zinc blende materials, including present tunneling theories (which are essentially parabolic-band results in disguise) and the nonparabolic-band formalism of Pidgeon et al. and Weiler. The agreement between our predictions and previous measurements allowed us to use ZnS as a reference material in order to validate a technique for measuring two-photon absorption that was previously untried in solids, pulsed dual-beam thermal lensing. With the validated technique, we examined nonlinear absorption in one other crystal (rutile) and in several glasses, including silicates, borosilicates, and one phosphate glass. Initially, we believed that the absorption edges of all the materials were comparable; however, subsequent evidence suggested that the effective band-gap energies of the glasses were above the energy of two photons in our measurement. Therefore, we attribute the nonlinear absorption that we observed in glasses to impurities or defects. The measured nonlinear absorption coefficients were of the order of a few cm/TW in the glasses and of the order of 10 cm/GW in the crystals, four orders of magnitude higher than in glasses. 292 refs.

  12. Differential Absorption Lidar (DIAL) Measurements from Air and Space

    NASA Technical Reports Server (NTRS)

    Browell, E. V.; Ismail, S.; Grant, W. B.

    1998-01-01

    Differential absorption lidar (DIAL) systems have been used for the measurement of ozone, water vapor, and aerosols from aircraft platforms for over 18 years, yielding new insights into atmospheric chemistry, composition, and dynamics in large-scale field experiments conducted all over the world. The successful deployment of the lidar in-space technology experiment (LITE) in September 1994 demonstrated that space-based lidars can also collect valuable information on the global atmosphere. This paper reviews some of the contributions of the NASA Langley Research Center's airborne ozone and water vapor DIAL systems and space-based LITE system to the understanding of the atmosphere and discusses the feasibility and advantages of putting DIAL systems in space for routine atmospheric measurements of ozone and/or water vapor and aerosols and clouds. The technology and applications of the differential absorption lidar (DIAL) technique have progressed significantly since the first DIAL measurements of Schotland, and airborne DIAL measurements of ozone and water vapor are frequently being made in a wide range of field experiments. In addition, plans are underway to develop DIAL systems for use on satellites for continuous global measurements. This paper will highlight the history of airborne lidar and DIAL systems, summarize the major accomplishments of the NASA Langley DIAL program, and discuss specifications and goals for DIAL systems in space.

  13. Broadband absorption spectroscopy by combining frequency-domain and steady-state techniques

    NASA Astrophysics Data System (ADS)

    Berger, Andrew J.; Bevilacqua, Frederic; Jakubowski, Dorota B.; Cerussi, Albert E.; Butler, John A.; Hsiang, D.; Tromberg, Bruce J.

    2001-06-01

    A technique for measuring broadband near-infrared absorption spectra of turbid media is presented using a combination of frequency-domain (FD) and steady-state (SS) reflectance methods. Most of the wavelength coverage is provided by a white-light SS measurement, while the FD data are acquired at a few selected wavelengths. Coefficients of absorption ((mu) a) and reduced scattering ((mu) s') derived from the FD data are used to intensity-calibrate the SS measurements and to estimate (mu) s' at all wavelengths in the spectral window of interest. After these steps are performed, (mu) a can be determined by comparing the SS reflectance values to the predictions of diffusion theory, wavelength by wavelength. We present an application of this method to breast tumor characterization. A case study of a fibroadenoma is shown, where different absorption spectra were found between the normal and the tumor sides.

  14. Measurement of solutes in dialysate using UV absorption

    NASA Astrophysics Data System (ADS)

    Fridolin, Ivo; Magnusson, Martin; Lindberg, Lars-Goeran

    2001-06-01

    The aim of this work was to describe a new method for optical monitoring of solutes in a spent dialysate. The method utilizes UV light absorption employing a commercially available spectrophotometer. Measurements were performed both on collected dialysate samples and on-line. The concentration of several removed solutes and electrolytes in the serum and in the dialysate was determined simultaneously using standard laboratory techniques. During on-line monitoring the spectrophotometer was connected to the fluid outlet of the dialysis machine. On-line measurements during a single hemodialysis session demonstrated a possibility to monitor deviations in the dialysator performance (e.g. dialysator in by-pass). The experimental results indicated a good correlation between UV absorption and several removed solutes (urea, creatinine) in the spent dialysate. The correlation coefficient for urea and creatinine concentrations in the dialysate was very high for every individual treatment. The UV absorbance correlates well to the concentrations of several solutes thought to be uremic toxins. The results indicate that the technique can be used as a continuous, on-line method for monitoring deviations in the dialysator performance and may estimate the removal of the overall toxins. In the future, the new method will be used to evaluate parameters describing delivery of the prescribed treatment dose such as KT/V and Urea Reduction Rate (URR).

  15. Determining the Uncertainty of X-Ray Absorption Measurements

    PubMed Central

    Wojcik, Gary S.

    2004-01-01

    X-ray absorption (or more properly, x-ray attenuation) techniques have been applied to study the moisture movement in and moisture content of materials like cement paste, mortar, and wood. An increase in the number of x-ray counts with time at a location in a specimen may indicate a decrease in moisture content. The uncertainty of measurements from an x-ray absorption system, which must be known to properly interpret the data, is often assumed to be the square root of the number of counts, as in a Poisson process. No detailed studies have heretofore been conducted to determine the uncertainty of x-ray absorption measurements or the effect of averaging data on the uncertainty. In this study, the Poisson estimate was found to adequately approximate normalized root mean square errors (a measure of uncertainty) of counts for point measurements and profile measurements of water specimens. The Poisson estimate, however, was not reliable in approximating the magnitude of the uncertainty when averaging data from paste and mortar specimens. Changes in uncertainty from differing averaging procedures were well-approximated by a Poisson process. The normalized root mean square errors decreased when the x-ray source intensity, integration time, collimator size, and number of scanning repetitions increased. Uncertainties in mean paste and mortar count profiles were kept below 2 % by averaging vertical profiles at horizontal spacings of 1 mm or larger with counts per point above 4000. Maximum normalized root mean square errors did not exceed 10 % in any of the tests conducted. PMID:27366627

  16. Videogrammetric Model Deformation Measurement Technique

    NASA Technical Reports Server (NTRS)

    Burner, A. W.; Liu, Tian-Shu

    2001-01-01

    The theory, methods, and applications of the videogrammetric model deformation (VMD) measurement technique used at NASA for wind tunnel testing are presented. The VMD technique, based on non-topographic photogrammetry, can determine static and dynamic aeroelastic deformation and attitude of a wind-tunnel model. Hardware of the system includes a video-rate CCD camera, a computer with an image acquisition frame grabber board, illumination lights, and retroreflective or painted targets on a wind tunnel model. Custom software includes routines for image acquisition, target-tracking/identification, target centroid calculation, camera calibration, and deformation calculations. Applications of the VMD technique at five large NASA wind tunnels are discussed.

  17. Acoustic absorption measurement of human hair and skin within the audible frequency range.

    PubMed

    Katz, B F

    2000-11-01

    Utilizing the two-microphone impedance tube method, the acoustic absorption of human skin and hair is measured in the frequency range 1-6 kHz. Various locations on a number of human subjects are measured to determine if the presence of bone or an air pocket affects the acoustic absorption of human skin. The absorption coefficient of human hair is also measured. Additional techniques are utilized to minimize errors due to sample mounting methods. Techniques are employed to minimize potential errors in sensor and sample locations. The results of these measurements are compared to relevant historical papers on similar investigations. Results for skin measurements compare well with previous work. Measured hair absorption data do not agree with previous work in the area but do coincide with expected trends, which previous works do not.

  18. Contactless nondestructive measurement of bulk and surface recombination using frequency-modulated free carrier absorption

    NASA Astrophysics Data System (ADS)

    Sanii, F.; Giles, F. P.; Schwartz, R. J.; Gray, J. L.

    1992-03-01

    A measurement procedure is described which allows the contactless measurement of bulk lifetime and surface recombination. The procedure uses the the free-carrier absorption of a long-wavelength laser beam by a modulated free-carrier wave to measure and separate the bulk recombination from the surface recombination. The dependence of the absorption on the modulation frequency is used to accomplish the separation. Limitations of the technique are also discussed.

  19. Measurement of Acoustic Attenuation and Absorption Coefficients using Thermometry

    NASA Astrophysics Data System (ADS)

    Morris, Hugh; Rivens, Ian; Shaw, Adam; ter Haar, Gail

    2007-05-01

    Accurate knowledge of both the attenuation and the absorption coefficient of tissue are required when planning an optimal high intensity focused ultrasound treatment. A novel technique for simple measurement of this parameters has been developed in which a thin-film thermocouple (TFT) is placed between two layers of tissue of different thicknesses. The sample can be rotated about an axis through the junction of the TFT so that it can be insonated from either side leaving the tissue adjacent to the junction unchanged, but changing the overlying thickness. The attenuation and absorption coefficients can be calculated from the heating curves measured in the two orientations. Experiments have been carried out in both tissue mimicking material (TMM) and in ex vivo liver tissue. Weakly focused transducers, resonant at 1.05 MHz, 2.4 MHz and 3.55 MHz were used at free-field spatial peak intensities of 9-14 W/cm2. The temperature rise was measured as a function of time using a TFT. These thermocouples are not subject to the viscous heating artefact that is common to other thermocouple devices and so are advantageous for this purpose. Alignment was achieved with a 3D automated gantry system, which was controlled with specialised software. Timing and data acquisition were also controlled with this software. All experiments were carried out in degassed water. Results for TMM and degassed excised bovine liver are presented.

  20. Measurements of parallel electron velocity distributions using whistler wave absorption

    SciTech Connect

    Thuecks, D. J.; Skiff, F.; Kletzing, C. A.

    2012-08-15

    We describe a diagnostic to measure the parallel electron velocity distribution in a magnetized plasma that is overdense ({omega}{sub pe} > {omega}{sub ce}). This technique utilizes resonant absorption of whistler waves by electrons with velocities parallel to a background magnetic field. The whistler waves were launched and received by a pair of dipole antennas immersed in a cylindrical discharge plasma at two positions along an axial background magnetic field. The whistler wave frequency was swept from somewhat below and up to the electron cyclotron frequency {omega}{sub ce}. As the frequency was swept, the wave was resonantly absorbed by the part of the electron phase space density which was Doppler shifted into resonance according to the relation {omega}-k{sub ||v||} = {omega}{sub ce}. The measured absorption is directly related to the reduced parallel electron distribution function integrated along the wave trajectory. The background theory and initial results from this diagnostic are presented here. Though this diagnostic is best suited to detect tail populations of the parallel electron distribution function, these first results show that this diagnostic is also rather successful in measuring the bulk plasma density and temperature both during the plasma discharge and into the afterglow.

  1. Ultra sound absorption measurements in rock samples at low temperatures

    NASA Technical Reports Server (NTRS)

    Herminghaus, C.; Berckhemer, H.

    1974-01-01

    A new technique, comparable with the reverberation method in room acoustics, is described. It allows Q-measurements at rock samples of arbitrary shape in the frequency range of 50 to 600 kHz in vacuum (.1 mtorr) and at low temperatures (+20 to -180 C). The method was developed in particular to investigate rock samples under lunar conditions. Ultrasound absorption has been measured at volcanics, breccia, gabbros, feldspar and quartz of different grain size and texture yielding the following results: evacuation raises Q mainly through lowering the humidity in the rock. In a dry compact rock, the effect of evacuation is small. With decreasing temperature, Q generally increases. Between +20 and -30 C, Q does not change much. With further decrease of temperature in many cases distinct anomalies appear, where Q becomes frequency dependent.

  2. Development of surface thermal lensing technique in absorption and defect analyses of optical coatings

    NASA Astrophysics Data System (ADS)

    He, Hongbo; Li, Xia; Fan, Shuhai; Shao, Jianda; Zhao, Yuanan; Fan, Zhengxiu

    2005-12-01

    Absorption is one of the main factors which cause damage to optical coatings, under the radiation of high power lasers. Surface thermal lensing (STL) technique was developed into a practical high-sensitivity apparatus for the weak absorption analysis of optical coatings. A 20 W continuous-wave 1064 nm Nd:YAG laser and a 30 mW He-Ne laser were employed as pump source and probe source, respectively. Low noise photoelectrical components and an SR830 DSP lock-in amplifier were used for photo-thermal deformation signal detection. In order to improve sensitivity, the configuration of the apparatus was optimized through choosing appropriate parameters, that including pump beam spot size, chopper frequency, detection distance, waist radius and position of probe beam. Coating samples were mounted on an x-y stage which was driven by high precision stepper motors. Different processes of absorption measurements, including single spot, linear scan and 2-dimension area scan, could be performed manually or automatically under the control of PC program. Various optical coatings were prepared by both electron beam evaporation and ion beam sputtering deposition. High sensitivity was obtained and low to 10 ppb absorption could be measured by surface thermal lensing technique. And a spatial resolution of 25 micron was proved according to the area scanning which traced out the profile of photo-thermal defects inside optical coatings. The system was employed in the analyses of optical absorption, absorption uniformity and defect distribution, and revealed the relationship between laser-induced damage and absorption of optical coatings.

  3. [Measurement and analysis of absorption spectrum of human blood].

    PubMed

    Zhao, Zhi-Min; Xin, Yu-Jun; Wang, Le-Xin; Zhu, Wei-Hua; Zheng, Min; Guo, Xin

    2008-01-01

    The present paper puts forward a method of disease diagnosis by using the technology of spectrum analysis of human blood serum. The generation mechanism of absorption spectrum is explained and the absorption spectra of the normal blood serum and the sick blood serum are listed from the experiments of absorption spectrometry. Though the value of absorbency of the sick blood serum is almost equal to that of the normal blood serum in the most absorption spectra, there are some differences around 278 nm in the absorption spectrum. The absorbency of the blood serum with hyperglycemia is greater than that of the normal blood serum at 285 nm in the spectrum, and besides, there comes a peak shift of absorption with hyperglycemia. In the absorption spectrum of the blood serum with hypercholesterolemia, there is a clear absorption peak at 414 nm. However there is not any peak at that wavelength in the absorption spectrum of the normal blood serum. Through comparing the characters of the spectrum, we can judge if the blood sample is or not, and this blood analysis is a new method for the diagnosis of disease. Compared with other methods of blood measurements, the method of absorption spectrum analysis of blood serum presented in this paper, is more convenient for measurement, simpler for analysis, and easier to popularize.

  4. Measurements of the absorption coefficient of stratospheric aerosols

    NASA Technical Reports Server (NTRS)

    Ogren, J. A.; Ahlquist, N. C.; Clarke, A. D.; Charlson, R. J.

    1981-01-01

    The absorption coefficients of stratospheric aerosols are measured using a variation on the integrating plate method. The technique is based on the decrease in the transparency of a substrate when an absorbing aerosol is deposited on it. A Lambert scatterer is placed behind the substrate to integrate forward scattered light and minimize the effect of scattering on the measurement. The low pressure in the stratosphere is used for the direct impaction of particles onto a narrow strip of opal glass. The eight samples collected had a median value of 4 x 10 to the -9th m with an uncertainty of + or - 5 x 10 to the -9th m. If this absorption is due to graphitic carbon, then its concentration is estimated at about 0.4 ng/cu m, or about 0.25% of the total aerosol mass concentration. Estimates of the aerosol scattering coefficients based on satellite extinction inversions result in an aerosol single-scattering albedo in the range of 0.96-1.0.

  5. Modified Technique For Chemisorption Measurements

    NASA Technical Reports Server (NTRS)

    Schryer, David R.; Brown, Kenneth G.; Schryer, Jacqueline

    1989-01-01

    In measurements of chemisorption of CO on Pt/SnO2 catalyst observed that if small numbers of relatively large volumes of adsorbate gas are passed through sample, very little removal of CO detected. In these cases little or no CO has been chemisorbed on Pt/SnO2. Technique of using large number of small volumes of adsorbate gas to measure chemisorption applicable to many gas/material combinations other than CO on Pt/SnO2. Volume used chosen so that at least 10 percent of adsorbate gas removed during each exposure.

  6. A Method for Eliminating Beam Steering Error for the Modulated Absorption-Emission Thermometry Technique

    DTIC Science & Technology

    2014-01-01

    currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 1. REPORT DATE (DD-MM-YYYY) Jan 2014 2. REPORT TYPE Technical...Paper 3. DATES COVERED (From - To) Jan 2014- June 2014 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER In-House A Method for Eliminating Beam...14194 14. ABSTRACT Modulated absorption-emission thermometry (MAET) is a non-intrusive, radiometric technique for measuring line-of-sight average

  7. A Method for Eliminating Beam Steering Error for the Modulated Absorption-Emission Thermometry Technique

    DTIC Science & Technology

    2015-01-01

    currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 1. REPORT DATE (DD-MM-YYYY) December 2014 2. REPORT TYPE...Briefing Charts 3. DATES COVERED (From - To) December 2014- January 2015 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER N/A A Method for Eliminating...Jan 2015. PA#14562. 14. ABSTRACT Modulated absorption-emission thermometry (MAET) is a non-intrusive, radiometric technique for measuring line-of

  8. Examination of the Measurement of Absorption Using the Reverberant Room Method for Highly Absorptive Acoustic Foam

    NASA Technical Reports Server (NTRS)

    Hughes, William O.; McNelis, Anne M.; Chris Nottoli; Eric Wolfram

    2015-01-01

    The absorption coefficient for material specimens are needed to quantify the expected acoustic performance of that material in its actual usage and environment. The ASTM C423-09a standard, "Standard Test Method for Sound Absorption and Sound Absorption Coefficients by the Reverberant Room Method" is often used to measure the absorption coefficient of material test specimens. This method has its basics in the Sabine formula. Although widely used, the interpretation of these measurements are a topic of interest. For example, in certain cases the measured Sabine absorption coefficients are greater than 1.0 for highly absorptive materials. This is often attributed to the diffraction edge effect phenomenon. An investigative test program to measure the absorption properties of highly absorbent melamine foam has been performed at the Riverbank Acoustical Laboratories. This paper will present and discuss the test results relating to the effect of the test materials' surface area, thickness and edge sealing conditions. A follow-on paper is envisioned that will present and discuss the results relating to the spacing between multiple piece specimens, and the mounting condition of the test specimen.

  9. Absorption coefficient measurements of particle-laden filters using laser heating: Validation with nigrosin

    NASA Astrophysics Data System (ADS)

    Presser, Cary

    2012-05-01

    A laser-heating technique, referred as the laser-driven thermal reactor, was used in conjunction with laser transmissivity measurements to determine the absorption coefficient of particle-laden substrates (e.g., quartz-fiber filters). The novelty of this approach is that it analyzes a wide variety of specific samples (not just filtered samples) and overcomes measurement issues (e.g., absorption enhancement) associated with other filter-based particle absorption techniques. The absorption coefficient was determined for nigrosin-laden, quartz-fiber filters and the effect of the filter on the absorption measurements was estimated when compared to the isolated nigrosin results. The isolated nigrosin absorption coefficient compared favorably with Lorenz-Mie calculations for an idealized polydispersion of spherical particles (based on a measured nigronsin/de-ionized water suspension size distribution) dispersed throughout a volume equivalent to that of the nigrosin-laden filter. To validate the approach, the absorption coefficient of a nigrosin/de-ionized water suspension was in good agreement with results obtained from an ultraviolet/visible spectrometer. In addition, the estimated imaginary part of the refractive index from the Lorenz-Mie calculations compared well with literature values and was used to estimate the absorption coefficient of optically opaque packed nigrosin.

  10. Temperature measurement using ultraviolet laser absorption of carbon dioxide behind shock waves.

    PubMed

    Oehlschlaeger, Matthew A; Davidson, David F; Jeffries, Jay B

    2005-11-01

    A diagnostic for microsecond time-resolved temperature measurements behind shock waves, using ultraviolet laser absorption of vibrationally hot carbon dioxide, is demonstrated. Continuous-wave laser radiation at 244 and 266 nm was employed to probe the spectrally smooth CO2 ultraviolet absorption, and an absorbance ratio technique was used to determine temperature. Measurements behind shock waves in both nonreacting and reacting (ignition) systems were made, and comparisons with isentropic and constant-volume calculations are reported.

  11. A measurement technique for hydroxyacetone

    SciTech Connect

    Klotz, P.J.

    1999-10-04

    Hydroxyacetone (HA) is mainly produced in the atmosphere from oxidation of hydrocarbons of the type, CH{sub 3}(R)C{double{underscore}bond}CH{sub 2}. Tuazon and Atkinson (1990) reported HA yield of 41% from the OH-initiated oxidation of methacrolein in the presence of NOx. Since methacrolein is a major product of isoprene oxidation (Carter and Atkinson, 1996), isoprene, a key biogenic hydrocarbon, is therefore expected to be an important source for HA. Consequently, knowledge of ambient concentration of HA would provide information needed to examine the applicability of isoprene reaction mechanisms developed in laboratory and to assess the contribution of isoprene to photooxidant production. The commonly used GC-FID technique involving cryo-focusing is unsuitable for HA owing to HA's thermal instability. When subjected to a temperature of 100 C for only a few seconds, HA was found to disappear completely. Since HA is highly soluble in water, the authors developed a wet chemical technique similar in principle to the one they reported earlier, namely, derivatization following liquid scrubbing. To increase the sensitivity, they adopted a fluorescence detection scheme based on o-phthaldialdehyde (OPA) chemistry. The technique was deployed in the field during two measurement periods at a NARSTO site located on Long Island, New York. The authors report the principle and the operation of this technique and the results obtained from these field studies.

  12. Assessment of multiphoton absorption in inert gases for the measurement of gas temperatures.

    PubMed

    Bednar, Natalie J; Walewski, Joachim W; Sanders, Scott T

    2006-03-01

    A spatially resolved optical technique to measure gas temperature was assessed. The technique relies on multiphoton absorption in inert gases. In contrast to laser-induced fluorescence, absorption is insensitive to collisional deactivation, and, in contrast to one-photon absorption, multiphoton absorption only occurs around the focus point of a typical laser beam. Multiphoton absorption features both the merits of being insensitive to quenching and of being a spatially resolved technique. In a case study we assessed two-photon absorption in xenon upon exciting the 5p6 1S0-->5p56p[5/2]2 transition in xenon at a wavelength of 256 nm. The amount of light absorbed by xenon is related to the number density of the gas, and if the gas pressure is known then the gas temperature can be inferred from the number density. Two-photon absorbance was measured as a function of xenon number density and was used to validate a theoretical model of the absorption process. We discuss the circumnavigation of experimental challenges in applying this technique and analyze its precision in terms of the inferred gas temperature.

  13. Coal thickness gauge using RRAS techniques, part 1. [radiofrequency resonance absorption

    NASA Technical Reports Server (NTRS)

    Rollwitz, W. L.; King, J. D.

    1978-01-01

    A noncontacting sensor having a measurement range of 0 to 6 in or more, and with an accuracy of 0.5 in or better is needed to control the machinery used in modern coal mining so that the thickness of the coal layer remaining over the rock is maintained within selected bounds. The feasibility of using the radiofrequency resonance absorption (RRAS) techniques of electron magnetic resonance (EMR) and nuclear magnetic resonance (NMR) as the basis of a coal thickness gauge is discussed. The EMR technique was found, by analysis and experiments, to be well suited for this application.

  14. A MEASUREMENT TECHNIQUE FOR HYDROXYACETONE.

    SciTech Connect

    KLOTZ,P.J.

    1999-10-04

    Hydroxyacetone (HA) is mainly produced in the atmosphere from oxidation of hydrocarbons of the type, CH{sub 3}(R)C=CH{sub 2}. Tuazon and Atkinson (1990) reported HA yield of 41% from the OH-initiated oxidation of methacrolein in the presence of NO{sub x}. Since methacrolein is a major product of isoprene oxidation (Carter and Atkinson, 1996), isoprene, a key biogenic hydrocarbon, is therefore expected to be an important source for HA. Consequently, knowledge of ambient concentration of HA would provide information needed to examine the applicability of isoprene reaction mechanisms developed in laboratory and to assess the contribution of isoprene to photooxidant production. The commonly used GC-FID technique involving cryo-focusing is unsuitable for HA owing to HA's thermal instability. When subjected to a temperature of 100 C for only a few seconds, HA was found to disappear completely. Since HA is highly soluble in water (it's Henry's law constant being {approx}2 x 10{sup 4} M atm{sup -1} at 20 C, Zhou and Lee, unpublished data), we developed a wet chemical technique similar in principle to the one we reported earlier (Lee and Zhou, 1993), namely, based on derivatization following liquid scrubbing. To increase the sensitivity, we adopted a fluorescence detection scheme based on o-phthaldialdehyde (OPA) chemistry. The technique was deployed in the field during two measurement periods at a NARSTO site located on Long Island (LI), New York. We report the principle and the operation of this technique and the results obtained from these field studies.

  15. Atmospheric Pre-Corrected Differential Absorption Techniques to Retrieve Columnar Water Vapor: Theory and Simulations

    NASA Technical Reports Server (NTRS)

    Borel, Christoph C.; Schlaepfer, Daniel

    1996-01-01

    Two different approaches exist to retrieve columnar water vapor from imaging spectrometer data: (1) Differential absorption techniques based on: (a) Narrow-Wide (N/W) ratio between overlapping spectrally wide and narrow channels; (b) Continuum Interpolated Band Ratio (CIBR) between a measurement channel and the weighted sum of two reference channels. (2) Non-linear fitting techniques which are based on spectral radiative transfer calculations. The advantage of the first approach is computational speed and of the second, improved retrieval accuracy. Our goal was to improve the accuracy of the first technique using physics based on radiative transfer. Using a modified version of the Duntley equation, we derived an "Atmospheric Pre-corrected Differential Absorption" (APDA) technique and described an iterative scheme to retrieve water vapor on a pixel-by-pixel basis. Next we compared both, the CIBR and the APDA using the Duntley equation for MODTRAN3 computed irradiances, transmissions and path radiance (using the DISORT option). This simulation showed that the CIBR is very sensitive to reflectance effects and that the APDA performs much better. An extensive data set was created with the radiative transfer code 6S over 379 different ground reflectance spectra. The calculated relative water vapor error was reduced significantly for the APDA. The APDA technique had about 8% (vs. over 35% for the CIBR) of the 379 spectra with a relative water vapor error of greater than +5%. The APDA has been applied to 1991 and 1995 AVIRIS scenes which visually demonstrate the improvement over the CIBR technique.

  16. Spectral Measurements of Aerosol Absorption from UV to VISIBLE

    NASA Astrophysics Data System (ADS)

    Krotkov, N. A.; Labow, G.; Herman, J.; Bhartia, P. K.; Slusser, J.; Durham, B.; Janson, G.; Wilson, C.; Disterhoft, P.; Cede, A.; Abuhassan, N.; Eck, T. F.; Holben, B.; Bais, A.; Rapsomanikis, S.

    2007-05-01

    Amount of solar radiation reaching the Earth's surface can be strongly influenced by aerosol absorption. The aerosol absorption optical thickness (AAOT) in the visible and near IR (440 nm- 1020nm) is routinely produced from almucantar measurements made by the CIMEL instruments in the AERONET network. AAOT in the UV (300nm- 368nm) have been derived from the total and diffuse hemispherical flux measurements made by UV- Multifilter Rotating Shadowband Radiometer (UV-MFRSR, Yankee Environmental Systems, Inc.) instruments. However, no direct comparisons between these two methods exist because the CIMEL wavelengths (used in almucantar retrievals) do not overlap with the UV-MFRSR wavelengths. To enable direct comparisons between the two techniques, we have modified our UV-MFRSR, part of USDA UVB Monitoring and Research Network, by replacing standard 300nm filter with 440nm filter used in AERONET network. The instrument has been deployed at Mauna Loa Observatory, at NASA GSFC in Greenbelt, MD (July 2005 - June 2006) and during SCOUT-03 field campaign in Thessaloniki, Greece in July 2006. During these deployments the instrument's calibration was monitored daily using co-located AERONET and BREWER direct sun measurements of aerosol extinction optical thickness (AOT). Between the deployments the instrument was thoroughly calibrated at the NOAA Central UV Calibration Facility in Boulder, Colorado. We find that the UV-MSFRSR instrument is highly susceptible to calibration drifts. However, these drifts can be accurately assessed using AERONET and BREWER direct sun data. After correcting for these calibration changes, the AAOT was inferred by fitting the measurements of global and diffuse atmospheric transmittances with the forward RT model independently at each spectral channel. The AOT data and ancillary measurements of aerosol column particle size distribution and refractive index in the visible wavelengths (by CIMEL sun-sky almucantar inversions), direct -sun column NO2 and

  17. The absorption of ultraviolet light by cell nuclei. A technique for identifying neoplastic change

    SciTech Connect

    Baisden, C.R.; Booker, D.; Wright, R.D. )

    1989-11-01

    A technique for measuring the absorption of 260-nm ultraviolet light by cell nuclei is described. The results of such measurements of normal thyroid epithelial cells and benign and malignant thyroid neoplastic cells demonstrate a progressive increase in absorbance that correlates with the histologic appearance of neoplasia. The possible theoretic basis for this phenomenon is explored. The increased nuclear absorbance observed in neoplastic cells is hypothesized to result from the disruption of hydrogen bonds between the DNA base pairs, which allows unwinding of the double helix and loss of the normal control of mitosis.

  18. A comparison study of linear reconstruction techniques for diffuse optical tomographic imaging of absorption coefficient

    NASA Astrophysics Data System (ADS)

    Gaudette, Richard J.; Brooks, Dana H.; Di Marzio, Charles A.; Kilmer, Misha E.; Miller, Eric L.; Gaudette, Thomas; Boas, David A.

    2000-04-01

    We compare, through simulations, the performance of four linear algorithms for diffuse optical tomographic reconstruction of the three-dimensional distribution of absorption coefficient within a highly scattering medium using the diffuse photon density wave approximation. The simulation geometry consisted of a coplanar array of sources and detectors at the boundary of a half-space medium. The forward solution matrix is both underdetermined, because we estimate many more absorption coefficient voxels than we have measurements, and ill-conditioned, due to the ill-posedness of the inverse problem. We compare two algebraic techniques, ART and SIRT, and two subspace techniques, the truncated SVD and CG algorithms. We compare three-dimensional reconstructions with two-dimensional reconstructions which assume all inhomogeneities are confined to a known horizontal slab, and we consider two `object-based' error metrics in addition to mean square reconstruction error. We include a comparison using simulated data generated using a different FDFD method with the same inversion algorithms to indicate how our conclusions are affected in a somewhat more realistic scenario. Our results show that the subspace techniques are superior to the algebraic techniques in localization of inhomogeneities and estimation of their amplitude, that two-dimensional reconstructions are sensitive to underestimation of the object depth, and that an error measure based on a location parameter can be a useful complement to mean squared error.

  19. In vivo low-coherence spectroscopic measurements of local hemoglobin absorption spectra in human skin

    NASA Astrophysics Data System (ADS)

    Bosschaart, Nienke; Faber, Dirk J.; van Leeuwen, Ton G.; Aalders, Maurice C. G.

    2011-10-01

    Localized spectroscopic measurements of optical properties are invaluable for diagnostic applications that involve layered tissue structures, but conventional spectroscopic techniques lack exact control over the size and depth of the probed tissue volume. We show that low-coherence spectroscopy (LCS) overcomes these limitations by measuring local attenuation and absorption coefficient spectra in layered phantoms. In addition, we demonstrate the first in vivo LCS measurements of the human epidermis and dermis only. From the measured absorption in two distinct regions of the dermal microcirculation, we determine total hemoglobin concentration (3.0+/-0.5 g/l and 7.8+/-1.2 g/l) and oxygen saturation.

  20. In vivo low-coherence spectroscopic measurements of local hemoglobin absorption spectra in human skin.

    PubMed

    Bosschaart, Nienke; Faber, Dirk J; van Leeuwen, Ton G; Aalders, Maurice C G

    2011-10-01

    Localized spectroscopic measurements of optical properties are invaluable for diagnostic applications that involve layered tissue structures, but conventional spectroscopic techniques lack exact control over the size and depth of the probed tissue volume. We show that low-coherence spectroscopy (LCS) overcomes these limitations by measuring local attenuation and absorption coefficient spectra in layered phantoms. In addition, we demonstrate the first in vivo LCS measurements of the human epidermis and dermis only. From the measured absorption in two distinct regions of the dermal microcirculation, we determine total hemoglobin concentration (3.0±0.5 g∕l and 7.8±1.2 g∕l) and oxygen saturation.

  1. Models of filter-based particle light absorption measurements

    NASA Astrophysics Data System (ADS)

    Hamasha, Khadeejeh M.

    Light absorption by aerosol is very important in the visible, near UN, and near I.R region of the electromagnetic spectrum. Aerosol particles in the atmosphere have a great influence on the flux of solar energy, and also impact health in a negative sense when they are breathed into lungs. Aerosol absorption measurements are usually performed by filter-based methods that are derived from the change in light transmission through a filter where particles have been deposited. These methods suffer from interference between light-absorbing and light-scattering aerosol components. The Aethalometer is the most commonly used filter-based instrument for aerosol light absorption measurement. This dissertation describes new understanding of aerosol light absorption obtained by the filter method. The theory uses a multiple scattering model for the combination of filter and particle optics. The theory is evaluated using Aethalometer data from laboratory and ambient measurements in comparison with photoacoustic measurements of aerosol light absorption. Two models were developed to calculate aerosol light absorption coefficients from the Aethalometer data, and were compared to the in-situ aerosol light absorption coefficients. The first is an approximate model and the second is a "full" model. In the approximate model two extreme cases of aerosol optics were used to develop a model-based calibration scheme for the 7-wavelength Aethalometer. These cases include those of very strong scattering aerosols (Ammonium sulfate sample) and very absorbing aerosols (kerosene soot sample). The exponential behavior of light absorption in the strong multiple scattering limit is shown to be the square root of the total absorption optical depth rather than linear with optical depth as is commonly assumed with Beer's law. 2-stream radiative transfer theory was used to develop the full model to calculate the aerosol light absorption coefficients from the Aethalometer data. This comprehensive model

  2. Minute Concentration Measurements of Simple Hydrocarbon Species Using Supercontinuum Laser Absorption Spectroscopy.

    PubMed

    Yoo, Jihyung; Traina, Nicholas; Halloran, Michael; Lee, Tonghun

    2016-06-01

    Minute concentration measurements of simple hydrocarbon gases are demonstrated using near-infrared supercontinuum laser absorption spectroscopy. Absorption-based gas sensors, particularly when combined with optical fiber components, can significantly enhance diagnostic capabilities to unprecedented levels. However, these diagnostic techniques are subject to limitations under certain gas sensing applications where interference and harsh conditions dominate. Supercontinuum laser absorption spectroscopy is a novel laser-based diagnostic technique that can exceed the above-mentioned limitations and provide accurate and quantitative concentration measurement of simple hydrocarbon species while maintaining compatibility with telecommunications-grade optical fiber components. Supercontinuum radiation generated using a highly nonlinear photonic crystal fiber is used to probe rovibrational absorption bands of four hydrocarbon species using full-spectral absorption diagnostics. Absorption spectra of methane (CH4), acetylene (C2H2), and ethylene (C2H4) were measured in the near-infrared spectrum at various pressures and concentrations to determine the accuracy and feasibility of the diagnostic strategy. Absorption spectra of propane (C3H8) were subsequently probed between 1650 nm and 1700 nm, to demonstrate the applicability of the strategy. Measurements agreed very well with simulated spectra generated using the HITRAN database as well as with previous experimental results. Absorption spectra of CH4, C2H2, and C2H4 were then analyzed to determine their respective measurement accuracy and detection limit. Concentration measurements integrated from experimental results were in very good agreement with independent concentration measurements. Calculated detection limits of CH4, C2H2, and C2H4 at room temperature and atmospheric pressure are 0.1%, 0.09%, and 0.17%, respectively.

  3. Active feedback regulation of a Michelson interferometer to achieve zero-background absorption measurements.

    PubMed

    Lundin, Patrik; Guan, Zuguang; Svanberg, Sune

    2011-01-20

    An active phase-controlling scheme based on a proportional-integral-derivative-controlled piezoelectric transducer is presented with the purpose of stabilizing a quasi-zero-background absorption spectrometer. A fiber-based balanced Michelson interferometer is used, and absorption due to a gas sample in one of its arms results in an increased light signal to a detector, which otherwise, thanks to destructive interference, experiences a very low light level. With the presented approach, the sensitivity of already potent absorption measurement techniques, e.g., based on modulation, could be improved even further.

  4. Inferring surface solar absorption from broadband satellite measurements

    NASA Technical Reports Server (NTRS)

    Cess, Robert D.; Vulis, Inna L.

    1989-01-01

    An atmospheric solar radiation model and surface albedo models that include wavelength dependence and surface anisotropy are combined to study the possibility of inferring the surface solar absorption from satellite measurements. The model includes ocean, desert, pasture land, savannah, and bog surface categories. Problems associated with converting narrowband measurements to broadband quantities are discussed, suggesting that it would be easier to infer surface solar absorption from broadband measurements directly. The practice of adopting a linear relationship between planetary and surface albedo to estimate surface albedos from satellite measurements is examined, showing that the linear conversion between broadband planetary and surface albedos is strongly dependent on vegetation type. It is suggested that there is a linear slope-offset relationship between surface and surface-atmosphere solar absorption.

  5. Ozone absorption cross section measurements in the Wulf bands

    NASA Technical Reports Server (NTRS)

    Anderson, Stuart M.; Hupalo, Peter; Mauersberger, Konrad

    1993-01-01

    A tandem dual-beam spectrometer has been developed to determine ozone absorption cross sections for 13 selected wavelengths between 750 and 975 nm at room temperature. The increasingly pronounced structure in this region may interfere with atmospheric trace gas transitions that are useful for remote sensing and complicate the measurement of aerosols. Ozone concentrations were determined by absorption at the common HeNe laser transition near 632.8 nm using the absolute cross section reported previously. The overall accuracy of these room temperature measurements is generally better than 2 percent. A synoptic near-IR spectrum scaled to these measurements is employed for comparison with results of previous studies.

  6. Airborne Measurements of CO2 Column Absorption and Range Using a Pulsed Direct-Detection Integrated Path Differential Absorption Lidar

    NASA Technical Reports Server (NTRS)

    Abshire, James B.; Riris, Haris; Weaver, Clark J.; Mao, Jianping; Allan, Graham R.; Hasselbrack, William E.; Browell, Edward V.

    2013-01-01

    We report on airborne CO2 column absorption measurements made in 2009 with a pulsed direct-detection lidar operating at 1572.33 nm and utilizing the integrated path differential absorption technique. We demonstrated these at different altitudes from an aircraft in July and August in flights over four locations in the central and eastern United States. The results show clear CO2 line shape and absorption signals, which follow the expected changes with aircraft altitude from 3 to 13 km. The lidar measurement statistics were also calculated for each flight as a function of altitude. The optical depth varied nearly linearly with altitude, consistent with calculations based on atmospheric models. The scatter in the optical depth measurements varied with aircraft altitude as expected, and the median measurement precisions for the column varied from 0.9 to 1.2 ppm. The altitude range with the lowest scatter was 810 km, and the majority of measurements for the column within it had precisions between 0.2 and 0.9 ppm.

  7. Atmospheric Water Vapour Differential Absorption Measurements with an Infrared Sounder.

    DTIC Science & Technology

    1982-03-01

    such as amonia . As the differential absorption was only of the order of 2 dB for the above measurements (at 450 m range), the measurements were repeated...frequent(ref.7), and most seriously affect surface based radio frequency sensors and communications systems. Further development and refinement of the

  8. Intestinal adaptation in patients with short bowel syndrome. Measurement by calcium absorption

    SciTech Connect

    Gouttebel, M.C.; Saint Aubert, B.; Colette, C.; Astre, C.; Monnier, L.H.; Joyeux, H. )

    1989-05-01

    Functional adaptation of remaining intestine was evaluated in 30 patients with extensive small bowel resection. Calcium and xylose absorption tests were compared. Calcium absorption was measured by a double-radiotracer technique. Serum xylosemia was measured 2 hr after D-xylose ingestion. Patients were divided into two groups according to the time interval between surgery and evaluation: less (group I) or more (group II) than two years. A statistically significant correlation was found between xylosemia and remaining small bowel length (r = 0.71; P less than 0.001) and between calcium absorption and remaining small bowel length (r = 0.75; P less than 0.001) in group I. A significant correlation was also observed between calcium absorption and time after surgery (r = 0.65; P = 0.001) but not for xylose absorption. Calcium absorption value was significantly increased in group II patients compared with group I patients matched for remaining small bowel length (36.2 +/- 12.5% vs 14.5 +/- 9.1%; P less than 0.001) while no difference was observed between the two groups concerning xylose absorption. These data indicate that intestinal calcium absorption continues to increase for more than two years after a major bowel resection in man. The intestine does not seem to recover all its functions at the same time.

  9. Field measurements involve various techniques

    SciTech Connect

    Moore, D.P.; Byars, H.G. )

    1990-07-30

    A number of field techniques are available to determine the extent of corrosion on production equipment. This article on oil field corrosion explains the use of corrosion coupons, several types of probes, and various inspection techniques, and shows how to monitor iron content in water.

  10. Correction of optical absorption and scattering variations in laser speckle rheology measurements

    PubMed Central

    Hajjarian, Zeinab; Nadkarni, Seemantini K.

    2014-01-01

    Laser Speckle Rheology (LSR) is an optical technique to evaluate the viscoelastic properties by analyzing the temporal fluctuations of backscattered speckle patterns. Variations of optical absorption and reduced scattering coefficients further modulate speckle fluctuations, posing a critical challenge for quantitative evaluation of viscoelasticity. We compare and contrast two different approaches applicable for correcting and isolating the collective influence of absorption and scattering, to accurately measure mechanical properties. Our results indicate that the numerical approach of Monte-Carlo ray tracing (MCRT) reliably compensates for any arbitrary optical variations. When scattering dominates absorption, yet absorption is non-negligible, diffusing wave spectroscopy (DWS) formalisms perform similar to MCRT, superseding other analytical compensation approaches such as Telegrapher equation. The computational convenience of DWS greatly simplifies the extraction of viscoelastic properties from LSR measurements in a number of chemical, industrial, and biomedical applications. PMID:24663983

  11. Correction of optical absorption and scattering variations in Laser Speckle Rheology measurements.

    PubMed

    Hajjarian, Zeinab; Nadkarni, Seemantini K

    2014-03-24

    Laser Speckle Rheology (LSR) is an optical technique to evaluate the viscoelastic properties by analyzing the temporal fluctuations of backscattered speckle patterns. Variations of optical absorption and reduced scattering coefficients further modulate speckle fluctuations, posing a critical challenge for quantitative evaluation of viscoelasticity. We compare and contrast two different approaches applicable for correcting and isolating the collective influence of absorption and scattering, to accurately measure mechanical properties. Our results indicate that the numerical approach of Monte-Carlo ray tracing (MCRT) reliably compensates for any arbitrary optical variations. When scattering dominates absorption, yet absorption is non-negligible, diffusing wave spectroscopy (DWS) formalisms perform similar to MCRT, superseding other analytical compensation approaches such as Telegrapher equation. The computational convenience of DWS greatly simplifies the extraction of viscoelastic properties from LSR measurements in a number of chemical, industrial, and biomedical applications.

  12. Photothermal measurement of absorption and scattering losses in thin films excited by surface plasmons.

    PubMed

    Domené, Esteban A; Balzarotti, Francisco; Bragas, Andrea V; Martínez, Oscar E

    2009-12-15

    We present a novel noncontact, photothermal technique, based on the focus error signal of a commercial CD pickup head that allows direct determination of absorption in thin films. Combined with extinction methods, this technique yields the scattering contribution to the losses. Surface plasmon polaritons are excited using the Kretschmann configuration in thin Au films of varying thickness. By measuring the extinction and absorption simultaneously, it is shown that dielectric constants and thickness retrieval leads to inconsistencies if the model does not account for scattering.

  13. Measurements of Soot Mass Absorption Coefficients from 300 to 660 nm

    NASA Astrophysics Data System (ADS)

    Renbaum-Wolff, Lindsay; Fisher, Al; Helgestad, Taylor; Lambe, Andrew; Sedlacek, Arthur; Smith, Geoffrey; Cappa, Christopher; Davidovits, Paul; Onasch, Timothy; Freedman, Andrew

    2016-04-01

    Soot, a product of incomplete combustion, plays an important role in the earth's climate system through the absorption and scattering of solar radiation. In particular, the assumed mass absorption coefficient (MAC) of soot and its variation with wavelength presents a significant uncertainty in the calculation of radiative forcing in global climate change models. As part of the fourth Boston College/Aerodyne soot properties measurement campaign, we have measured the mass absorption coefficient of soot produced by an inverted methane diffusion flame over a spectral range of 300-660 nm using a variety of optical absorption techniques. Extinction and absorption were measured using a dual cavity ringdown photoacoustic spectrometer (CRD-PAS, UC Davis) at 405 nm and 532 nm. Scattering and extinction were measured using a CAPS PMssa single scattering albedo monitor (Aerodyne) at 630 nm; the absorption coefficient was determined by subtraction. In addition, the absorption coefficients in 8 wavelength bands from 300 to 660 nm were measured using a new broadband photoacoustic absorption monitor (UGA). Soot particle mass was quantified using a centrifugal particle mass analyzer (CPMA, Cambustion), mobility size with a scanning mobility particle sizer (SMPS, TSI) and soot concentration with a CPC (Brechtel). The contribution of doubly charged particles to the sample mass was determined using a Single Particle Soot Photometer (DMT). Over a mass range of 1-8 fg, corresponding to differential mobility diameters of ~150 nm to 550 nm, the value of the soot MAC proved to be independent of mass for all wavelengths. The wavelength dependence of the MAC was best fit to a power law with an Absorption Ångstrom Coefficient slightly greater than 1.

  14. Airborne Carbon Dioxide Laser Absorption Spectrometer for IPDA Measurements of Tropospheric CO2: Recent Results

    NASA Technical Reports Server (NTRS)

    Spiers, Gary D.; Menzies, Robert T.

    2008-01-01

    The National Research Council's decadal survey on Earth Science and Applications from Space[1] recommended the Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) mission for launch in 2013-2016 as a logical follow-on to the Orbiting Carbon Observatory (OCO) which is scheduled for launch in late 2008 [2]. The use of a laser absorption measurement technique provides the required ability to make day and night measurements of CO2 over all latitudes and seasons. As a demonstrator for an approach to meeting the instrument needs for the ASCENDS mission we have developed the airborne Carbon Dioxide Laser Absorption Spectrometer (CO2LAS) which uses the Integrated Path Differential Absorption (IPDA) Spectrometer [3] technique operating in the 2 micron wavelength region.. During 2006 a short engineering checkout flight of the CO2LAS was conducted and the results presented previously [4]. Several short flight campaigns were conducted during 2007 and we report results from these campaigns.

  15. Measurement of incidence angle dependence of solar absorptance

    NASA Astrophysics Data System (ADS)

    Ohnishi, A.; Hayashi, T.

    1983-12-01

    For measuring solar absorptance dependence on incidence angle, an integrating sphere, in which the sample is fixed on the surface of the sphere, and the incident angle for the monochromatic beam on the surface is adjusted by the rotation of the integrating sphere, is proposed. Results for spacecraft materials are presented. Results for aluminized Teflon are 4% better compared with the standard method.

  16. Atmospheric pre-corrected differential absorption techniques to retrieve columnar water vapor: Theory and simulations

    SciTech Connect

    Borel, C.C.; Schlaepfer, D.

    1996-03-01

    Two different approaches exist to retrieve columnar water vapor from imaging spectrometer data: (1) Differential absorption techniques based on: (a) Narrow-Wide (N/W) ratio between overlapping spectrally wide and narrow channels (b) Continuum Interpolated Band Ratio (CIBR) between a measurement channel and the weighted sum of two reference channels; and (2) Non-linear fitting techniques which are based on spectral radiative transfer calculations. The advantage of the first approach is computational speed and of the second, improved retrieval accuracy. Our goal was to improve the accuracy of the first technique using physics based on radiative transfer. Using a modified version of the Duntley equation, we derived an {open_quote}Atmospheric Pre-corrected Differential Absorption{close_quote} (APDA) technique and described an iterative scheme to retrieve water vapor on a pixel-by-pixel basis. Next we compared both, the CIBR and the APDA using the Duntley equation for MODTRAN3 computed irradiances, transmissions and path radiance (using the DISORT option). This simulation showed that the CIBR is very sensitive to reflectance effects and that the APDA performs much better. An extensive data set was created with the radiative transfer code 6S over 379 different ground reflectance spectra. The calculated relative water vapor error was reduced significantly for the APDA. The APDA technique had about 8% (vs. over 35% for the CIBR) of the 379 spectra with a relative water vapor error of greater than {+-}5%. The APDA has been applied to 1991 and 1995 AVIRIS scenes which visually demonstrate the improvement over the CIBR technique.

  17. Quantitative photoacoustic measurement of tissue optical absorption spectrum aided by an optical contrast agent.

    PubMed

    Rajian, Justin Rajesh; Carson, Paul L; Wang, Xueding

    2009-03-16

    In photoacoustic imaging, the intensity of photoacoustic signal induced by optical absorption in biological tissue is proportional to light energy deposition, which is the product of the absorption coefficient and the local light fluence. Because tissue optical properties are highly dependent on the wavelength, the spectrum of the local light fluence at a target tissue beneath the sample surface is different than the spectrum of the incident light fluence. Therefore, quantifying the tissue optical absorption spectrum by using a photoacoustic technique is not feasible without the knowledge of the local light fluence. In this work, a highly accurate photoacoustic measurement of the subsurface tissue optical absorption spectrum has been achieved for the first time by introducing an extrinsic optical contrast agent with known optical properties. From the photoacoustic measurements with and without the contrast agent, a quantified measurement of the chromophore absorption spectrum can be realized in a strongly scattering medium. Experiments on micro-flow vessels containing fresh canine blood buried in phantoms and chicken breast tissues were carried out in a wavelength range from 680 nm to 950 nm. Spectroscopic photoacoustic measurements of both oxygenated and deoxygenated blood specimens presented an improved match with the references when employing this technique.

  18. Absorption of sound in air - High-frequency measurements

    NASA Technical Reports Server (NTRS)

    Bass, H. E.; Shields, F. D.

    1977-01-01

    The absorption of sound in air at frequencies from 4 to 100 kHz in 1/12 octave intervals, for temperatures from 255.4 K (0 F) to 310.9 K (100 F) in 5.5 K (10 F) intervals, and at 10% relative-humidity increments between 0% and saturation has been measured. The values of free-field absorption have been analyzed to determine the relaxation frequency of oxygen for each of the 92 combinations of temperature and relative humidity studied and the results are compared to an empirical expression. The relaxation frequencies of oxygen have been analyzed to determine the microscopic energy-transfer rates.

  19. Pressure Measurements Using an Airborne Differential Absorption Lidar. Part 1; Analysis of the Systematic Error Sources

    NASA Technical Reports Server (NTRS)

    Flamant, Cyrille N.; Schwemmer, Geary K.; Korb, C. Laurence; Evans, Keith D.; Palm, Stephen P.

    1999-01-01

    Remote airborne measurements of the vertical and horizontal structure of the atmospheric pressure field in the lower troposphere are made with an oxygen differential absorption lidar (DIAL). A detailed analysis of this measurement technique is provided which includes corrections for imprecise knowledge of the detector background level, the oxygen absorption fine parameters, and variations in the laser output energy. In addition, we analyze other possible sources of systematic errors including spectral effects related to aerosol and molecular scattering interference by rotational Raman scattering and interference by isotopic oxygen fines.

  20. Cryogenic Thermal Absorptance Measurements on Small-Diameter Stainless Steel Tubing

    NASA Technical Reports Server (NTRS)

    Tuttle, James; Jahromi, Amir; Canavan, Edgar; DiPirro, Michael

    2015-01-01

    The Mid Infrared Instrument (MIRI) on the James Webb Space Telescope includes a mechanical cryocooler which cools its detectors to their 6 Kelvin operating temperature. The coolant gas flows through several meters of small-diameter stainless steel tubing, which is exposed to thermal radiation from its environment. Over much of its length this tubing is gold-plated to minimize the absorption of this radiant heat. In order to confirm that the cryocooler will meet MIRI's requirements, the thermal absorptance of this tubing was measured as a function of its environment temperature. We describe the measurement technique and present the results.

  1. Prediction of absorption coefficients by pulsed laser induced photoacoustic measurements.

    PubMed

    Priya, Mallika; Satish Rao, B S; Ray, Satadru; Mahato, K K

    2014-06-05

    In the current study, a pulsed laser induced photoacoustic spectroscopy setup was designed and developed, aiming its application in clinical diagnostics. The setup was optimized with carbon black samples in water and with various tryptophan concentrations at 281nm excitations. The sensitivity of the setup was estimated by determining minimum detectable concentration of tryptophan in water at the same excitation, and was found to be 0.035mM. The photoacoustic experiments were also performed with various tryptophan concentrations at 281nm excitation for predicting optical absorption coefficients in them and for comparing the outcomes with the spectrophotometrically-determined absorption coefficients for the same samples. Absorption coefficients for a few serum samples, obtained from some healthy female volunteers, were also determined through photoacoustic and spectrophotometric measurements at the same excitations, which showed good agreement between them, indicating its clinical implications.

  2. Towards higher stability of resonant absorption measurements in pulsed plasmas

    SciTech Connect

    Britun, Nikolay; Michiels, Matthieu; Snyders, Rony

    2015-12-15

    Possible ways to increase the reliability of time-resolved particle density measurements in pulsed gaseous discharges using resonant absorption spectroscopy are proposed. A special synchronization, called “dynamic source triggering,” between a gated detector and two pulsed discharges, one representing the discharge of interest and another being used as a reference source, is developed. An internal digital delay generator in the intensified charge coupled device camera, used at the same time as a detector, is utilized for this purpose. According to the proposed scheme, the light pulses from the reference source follow the gates of detector, passing through the discharge of interest only when necessary. This allows for the utilization of short-pulse plasmas as reference sources, which is critical for time-resolved absorption analysis of strongly emitting pulsed discharges. In addition to dynamic source triggering, the reliability of absorption measurements can be further increased using simultaneous detection of spectra relevant for absorption method, which is also demonstrated in this work. The proposed methods are illustrated by the time-resolved measurements of the metal atom density in a high-power impulse magnetron sputtering (HiPIMS) discharge, using either a hollow cathode lamp or another HiPIMS discharge as a pulsed reference source.

  3. Invited Review Article: Imaging techniques for harmonic and multiphoton absorption fluorescence microscopy

    PubMed Central

    Carriles, Ramón; Schafer, Dawn N.; Sheetz, Kraig E.; Field, Jeffrey J.; Cisek, Richard; Barzda, Virginijus; Sylvester, Anne W.; Squier, Jeffrey A.

    2009-01-01

    We review the current state of multiphoton microscopy. In particular, the requirements and limitations associated with high-speed multiphoton imaging are considered. A description of the different scanning technologies such as line scan, multifoci approaches, multidepth microscopy, and novel detection techniques is given. The main nonlinear optical contrast mechanisms employed in microscopy are reviewed, namely, multiphoton excitation fluorescence, second harmonic generation, and third harmonic generation. Techniques for optimizing these nonlinear mechanisms through a careful measurement of the spatial and temporal characteristics of the focal volume are discussed, and a brief summary of photobleaching effects is provided. Finally, we consider three new applications of multiphoton microscopy: nonlinear imaging in microfluidics as applied to chemical analysis and the use of two-photon absorption and self-phase modulation as contrast mechanisms applied to imaging problems in the medical sciences. PMID:19725639

  4. Invited review article: Imaging techniques for harmonic and multiphoton absorption fluorescence microscopy.

    PubMed

    Carriles, Ramón; Schafer, Dawn N; Sheetz, Kraig E; Field, Jeffrey J; Cisek, Richard; Barzda, Virginijus; Sylvester, Anne W; Squier, Jeffrey A

    2009-08-01

    We review the current state of multiphoton microscopy. In particular, the requirements and limitations associated with high-speed multiphoton imaging are considered. A description of the different scanning technologies such as line scan, multifoci approaches, multidepth microscopy, and novel detection techniques is given. The main nonlinear optical contrast mechanisms employed in microscopy are reviewed, namely, multiphoton excitation fluorescence, second harmonic generation, and third harmonic generation. Techniques for optimizing these nonlinear mechanisms through a careful measurement of the spatial and temporal characteristics of the focal volume are discussed, and a brief summary of photobleaching effects is provided. Finally, we consider three new applications of multiphoton microscopy: nonlinear imaging in microfluidics as applied to chemical analysis and the use of two-photon absorption and self-phase modulation as contrast mechanisms applied to imaging problems in the medical sciences.

  5. Low-frequency sound absorption measurements in air

    NASA Technical Reports Server (NTRS)

    Zuckerwar, A. J.; Meredith, R. W.

    1984-01-01

    Thirty sets of sound absorption measurements in air at a pressure of 1 atmosphere are presented at temperatures from 10 C to 50 C, relative humidities from 0 to 100 percent, and frequencies from 10 to 2500 Hz. The measurements were conducted by the method of free decay in a resonant tube having a length of 18.261 m and bore diameter of 0.152 m. Background measurements in a gas consisting of 89.5 percent N2 and 10.5 percent Ar, a mixture which has the same sound velocity as air, permitted the wall and structural losses of the tube to be separated from the constituent absorption, consisting of classical rotational and vibrational absorption, in the air samples. The data were used to evaluate the vibrational relaxation frequencies of N2 and/or O2 for each of the 30 sets of meteorological parameters. Over the full range of humidity, the measured relaxation frequencies of N2 in air lie between those specified by ANSI Standard S1.26-1978 and those measured earlier in binary N2H2O mixtures. The measured relaxation frequencies could be determined only at very low values of humidity, reveal a significant trend away from the ANSI standard, in agreement with a prior investigation.

  6. Absorptance Measurements of Optical Coatings - A Round Robin

    SciTech Connect

    Chow, R; Taylor, J R; Wu, Z L; Boccara, C A; Broulik, U; Commandre, M; DiJon, J; Fleig, C; Giesen, A; Fan, Z X; Kuo, P K; Lalezari, R; Moncur, K; Obramski, H-J; Reicher, D; Ristau, D; Roche, P; Steiger, B; Thomsen, M; von Gunten, M

    2000-10-26

    An international round robin study was conducted on the absorption measurement of laser-quality coatings. Sets of optically coated samples were made by a ''reactive DC magnetron'' sputtering and an ion beam sputtering deposition process. The sample set included a high reflector at 514 nm and a high reflector for the near infrared (1030 to 1318 nm), single layers of silicon dioxide, tantalum pentoxide, and hafnium dioxide. For calibration purposes, a sample metalized with hafnium and an uncoated, superpolished fused silica substrate were also included. The set was sent to laboratory groups for absorptance measurement of these coatings. Whenever possible, each group was to measure a common, central area and another area specifically assigned to the respective group. Specific test protocols were also suggested in regards to the laser exposure time, power density, and surface preparation.

  7. Ozone absorption coefficients' role in Dobson instrument ozone measurement accuracy

    NASA Astrophysics Data System (ADS)

    Basher, R. E.

    1982-11-01

    The differences of 10% or more between the laboratory measurements of UV absorption coefficients by different investigators indicate accuracies that are quite inadequate for current needs in the measurement of atmospheric ozone. The standard band-integrated set of coefficients now used with the Dobson instrument are mutually consistent to about 2%, but their absolute accuracy is still in question. The accurate calculation of band-integrated coefficients must take account of their dependence on source spectral irradiance, atmospheric spectral transmittance, mean ozone temperature, and instrument spectral transmittance. A careful examination shows that Komhyr's (1980) case for an error of about +5% in the standard Dobson AD ozone estimation is subject to large uncertainties and certain lacks of independence. The obvious solution to this accuracy problem lies in better laboratory measurements of ozone absorption.

  8. Scattering error corrections for in situ absorption and attenuation measurements.

    PubMed

    McKee, David; Piskozub, Jacek; Brown, Ian

    2008-11-24

    Monte Carlo simulations are used to establish a weighting function that describes the collection of angular scattering for the WETLabs AC-9 reflecting tube absorption meter. The equivalent weighting function for the AC-9 attenuation sensor is found to be well approximated by a binary step function with photons scattered between zero and the collection half-width angle contributing to the scattering error and photons scattered at larger angles making zero contribution. A new scattering error correction procedure is developed that accounts for scattering collection artifacts in both absorption and attenuation measurements. The new correction method does not assume zero absorption in the near infrared (NIR), does not assume a wavelength independent scattering phase function, but does require simultaneous measurements of spectrally matched particulate backscattering. The new method is based on an iterative approach that assumes that the scattering phase function can be adequately modeled from estimates of particulate backscattering ratio and Fournier-Forand phase functions. It is applied to sets of in situ data representative of clear ocean water, moderately turbid coastal water and highly turbid coastal water. Initial results suggest significantly higher levels of attenuation and absorption than those obtained using previously published scattering error correction procedures. Scattering signals from each correction procedure have similar magnitudes but significant differences in spectral distribution are observed.

  9. Breakwire Technique for Hypervelocity Measurement

    DTIC Science & Technology

    1993-10-01

    R )ATORY DSTO - • ’, - , CCL!’ A ~t1 ror - NTSCRA&Ic ý, I rIC TA8 0 SU .,".o,;"ed...Boom,’ r , a large scale explohing’fl folhflii plat’ \\’einerator. Two techniques were tested, ta dual breakwire method and a single breakwire method. 7...E I ~0.8 U.0.6 0.4 0.2 0 0 4 8 12 16 Time. ps 1.8 Boomer 1: 3 WV 14 0.8 0.6 0.4 0.2 0 o 12 1824 F ~ev position. mm (b) Figure 7: ( a ) Approximate

  10. Measurement Techniques for Clock Jitter

    NASA Technical Reports Server (NTRS)

    Lansdowne, Chatwin; Schlesinger, Adam

    2012-01-01

    NASA is in the process of modernizing its communications infrastructure to accompany the development of a Crew Exploration Vehicle (CEV) to replace the shuttle. With this effort comes the opportunity to infuse more advanced coded modulation techniques, including low-density parity-check (LDPC) codes that offer greater coding gains than the current capability. However, in order to take full advantage of these codes, the ground segment receiver synchronization loops must be able to operate at a lower signal-to-noise ratio (SNR) than supported by equipment currently in use.

  11. Weathering: methods and techniques to measure

    NASA Astrophysics Data System (ADS)

    Lopez-Arce, P.; Zornoza-Indart, A.; Alvarez de Buergo, M.; Fort, R.

    2012-04-01

    Surface recession takes place when weathered material is removed from the rocks. In order to know how fast does weathering and erosion occur, a review of several methods, analyses and destructive and non-destructive techniques to measure weathering of rocks caused by physico-chemical changes that occur in bedrocks due to salt crystallization, freezing-thaw, thermal shock, influence of water, wind, temperature or any type of environmental agent leading to weathering processes and development of soils, in-situ in the field or through experimental works in the laboratory are addressed. From micro-scale to macro-scale, from the surface down to more in depth, several case studies on in-situ monitoring of quantification of decay on soils and rocks from natural landscapes (mountains, cliffs, caves, etc) or from urban environment (foundations or facades of buildings, retaining walls, etc) or laboratory experimental works, such as artificial accelerated ageing tests (a.a.e.e.) or durability tests -in which one or more than one weathering agents are selected to assess the material behaviour in time and in a cyclic way- performed on specimens of these materials are summarised. Discoloration, structural alteration, precipitation of weathering products (mass transfer), and surface recession (mass loss) are all products of weathering processes. Destructive (SEM-EDX, optical microscopy, mercury intrusion porosimetry, drilling resistance measurement, flexural and compression strength) and Non-destructive (spectrophotocolorimetry, 3D optical surface roughness, Schmidt hammer rebound tester, ultrasound velocity propagation, Nuclear Magnetic Resonance NMR, X ray computed micro-tomography or CT-scan, geo-radar differential global positioning systems) techniques and characterization analyses (e.g. water absorption, permeability, open porosity or porosity accessible to water) to assess their morphological, physico-chemical, mechanical and hydric weathering; consolidation products or

  12. Microwave Resonator Measurements of Atmospheric Absorption Coefficients: A Preliminary Design Study

    NASA Technical Reports Server (NTRS)

    Walter, Steven J.; Spilker, Thomas R.

    1995-01-01

    A preliminary design study examined the feasibility of using microwave resonator measurements to improve the accuracy of atmospheric absorption coefficients and refractivity between 18 and 35 GHz. Increased accuracies would improve the capability of water vapor radiometers to correct for radio signal delays caused by Earth's atmosphere. Calibration of delays incurred by radio signals traversing the atmosphere has applications to both deep space tracking and planetary radio science experiments. Currently, the Cassini gravity wave search requires 0.8-1.0% absorption coefficient accuracy. This study examined current atmospheric absorption models and estimated that current model accuracy ranges from 5% to 7%. The refractivity of water vapor is known to 1% accuracy, while the refractivity of many dry gases (oxygen, nitrogen, etc.) are known to better than 0.1%. Improvements to the current generation of models will require that both the functional form and absolute absorption of the water vapor spectrum be calibrated and validated. Several laboratory techniques for measuring atmospheric absorption and refractivity were investigated, including absorption cells, single and multimode rectangular cavity resonators, and Fabry-Perot resonators. Semi-confocal Fabry-Perot resonators were shown to provide the most cost-effective and accurate method of measuring atmospheric gas refractivity. The need for accurate environmental measurement and control was also addressed. A preliminary design for the environmental control and measurement system was developed to aid in identifying significant design issues. The analysis indicated that overall measurement accuracy will be limited by measurement errors and imprecise control of the gas sample's thermodynamic state, thermal expansion and vibration- induced deformation of the resonator structure, and electronic measurement error. The central problem is to identify systematic errors because random errors can be reduced by averaging

  13. Low-level optical absorption phenomena in organic thin films for solar cell applications investigated by highly sensitive photocurrent and photothermal techniques

    NASA Astrophysics Data System (ADS)

    Goris, Ludwig J.; Haenen, Ken; Nesladek, Milos; Poruba, A.; Vanecek, M.; Wagner, P.; Lutsen, Laurence J.; Manca, Jean; Vanderzande, Dirk; De Schepper, Luc

    2004-09-01

    Optical absorption phenomena and in particular sub band gap absorption features are of great importance in the understanding of processes of charge generation and transport in organic pure and composite semiconductor films. To come towards this objective, an alternative and high sensitive spectroscopic approach is introduced to examine the absorption of light in pure and compound organic semiconductors. Because sub band gap absorption features are typically characterized by very low absorption coefficients, it is not possible to resolve them using common transmission and reflection measurements and high sensitive alternatives are needed. Therefore, a combination of photocurrent (Constant Photocurrent Method CPM/Fourier Transform Photocurrent Spectroscopy FT-PS) and photothermal techniques (Photothermal Deflection Spectroscopy PDS) has been used, increasing sensitivity by a factor of thousand, reaching detectable absorption coefficients ((E) down to 0.1 cm-1. In this way, the dynamic range of measurable absorption coefficients is increased by several orders of magnitude compared to transmission/reflection measurements. These techniques have been used here to characterize ground state absorption of thin films of MDMO-PPV, PCBM and a mixture of both materials in a 1:4 ratio, as typically used in a standard active layer in a fully organic solar cell. The spectra reveal defect related absorption phenomena and significant indication of existing interaction in the ground state between both materials, contrary to the widely spread conviction that this is not the case. Experimental details of the techniques and measurement procedures are explained.

  14. Comparison of ozone measurement techniques using aircraft, balloon, and ground-based measurements

    NASA Technical Reports Server (NTRS)

    Briehl, D.; Reck, G. M.

    1977-01-01

    In order to verify the ultraviolet absorption technique used in the Global Atmospheric Sampling Program, two flight experiments were conducted employing several techniques, both in situ and remote, for measuring atmospheric ozone. The first experiment used the NASA CV-990 equipped with an ultraviolet absorption ozone monitor and an ultraviolet spectrophotometer, a balloon ozonesonde, and a Dobson station for determining and comparing the ozone concentration data. A second experiment compared ozone data from an automated sampling system aboard a B-747 with data from a manned system installed on the NASA CV-990 during a cross-country flight with both aircraft following the same flight path separated by 32 kilometers.

  15. Excited State Absorption Measurements In Some Scintillator Dye Solutions

    NASA Astrophysics Data System (ADS)

    Dharamsi, A., N.; Jong, Shawpin; Hassam, A. B.

    1986-11-01

    Time-resolved excited state triplet-triplet absorption spectra were measured for solutions of 2,5 diphenyloxazole (PPO) and 2,1 napthyl, 5 phenyloxazole (aNPO) in several solvents. Concentration quenching effects due to excimer formation in nonaromatic solvents were observed. A numerical analysis of the experimental results yielded the rate constants for intersystem crossing, triplet quenching by 02, triplet self quenching and the formation of excimers.

  16. Apparatus and method for measurement of weak optical absorptions by thermally induced laser pulsing

    DOEpatents

    Cremers, D.A.; Keller, R.A.

    1982-06-08

    The thermal lensing phenomenon is used as the basis for measurement of weak optical absorptions when a cell containing the sample to be investigated is inserted into a normally continuous-wave operation laser-pumped dye laser cavity for which the output coupler is deliberately tilted relative to intracavity circulating laser light, and pulsed laser output ensues, the pulsewidth of which can be rlated to the sample absorptivity by a simple algorithm or calibration curve. A minimum detection limit of less than 10/sup -5/ cm/sup -1/ has been demonstrated using this technique.

  17. Apparatus and method for measurement of weak optical absorptions by thermally induced laser pulsing

    DOEpatents

    Cremers, David A.; Keller, Richard A.

    1985-01-01

    The thermal lensing phenomenon is used as the basis for measurement of weak optical absorptions when a cell containing the sample to be investigated is inserted into a normally continuous-wave operation laser-pumped dye laser cavity for which the output coupler is deliberately tilted relative to intracavity circulating laser light, and pulsed laser output ensues, the pulsewidth of which can be related to the sample absorptivity by a simple algorithm or calibration curve. A minimum detection limit of less than 10.sup.-5 cm.sup.-1 has been demonstrated using this technique.

  18. Apparatus and method for measurement of weak optical absorptions by thermally induced laser pulsing

    DOEpatents

    Cremers, D.A.; Keller, R.A.

    1985-10-01

    The thermal lensing phenomenon is used as the basis for measurement of weak optical absorptions when a cell containing the sample to be investigated is inserted into a normally continuous-wave operation laser-pumped dye laser cavity for which the output coupler is deliberately tilted relative to intracavity circulating laser light, and pulsed laser output ensues, the pulsewidth of which can be related to the sample absorptivity by a simple algorithm or calibration curve. A minimum detection limit of less than 10[sup [minus]5] cm[sup [minus]1] has been demonstrated using this technique. 6 figs.

  19. Interpreting measurements obtained with the cloud absorption radiometer

    NASA Technical Reports Server (NTRS)

    1988-01-01

    The software developed for the analysis of data from the Cloud Absorption Radiometer (CAR) is discussed. The CAR is a multichannel radiometer designed to measure the radiation field in the middle of an optically thick cloud (the diffusion domain). It can also measure the surface albedo and escape function. The instrument currently flies on a C-131A aircraft operated by the University of Washington. Most of this data was collected during the First International satellite cloud climatology project Regional Experiment (FIRE) Marine Stratocumulus Intensive Field Observation program off San Diego during July 1987. Earlier flights of the CAR have also been studied.

  20. Integrated measurements of 222Rn by absorption in Makrofol

    NASA Astrophysics Data System (ADS)

    Pressyanov, Dobromir; Buysse, Jozef; Poffijn, André; Van Deynse, Annick; Meesen, Geert

    2004-01-01

    Recently, a method for long-term 222Rn measurements based on the radon absorption ability and track-etch properties of Makrofol has been proposed. The basic idea is to remove, after exposure, a surface layer, thicker than the range of the α-particles of the 222Rn or 220Rn progenies, and to study the track density of the electrochemically etched tracks at that depth. This paper summarizes the performance of the method under laboratory and field conditions. The effects on the response due to differences in pressure, temperature, humidity, the presence of 220Rn, dust and cigarette smoke in the air have been studied experimentally. The effect of these factors, but the temperature, is either absent, or restricted to about 10% for the very extreme cases. The variation of the response at the studied depth of 83 μm over the temperature interval 15-25°C is ±12% around the 19.5°C value. The field comparison conducted showed an agreement between the method of radon absorption in Makrofol and the conventional diffusion chambers. Therefore, a potential for long-term 222Rn measurements in the human environment by radon absorption in Makrofol or equivalent polycarbonates clearly exists.

  1. The Importance of Optical Pathlength Control for Plasma Absorption Measurements

    NASA Technical Reports Server (NTRS)

    Cruden, Brett A.; Rao, M. V. V. S.; Sharma, Surendra P.; Meyyappan, M.; Partridge, Harry (Technical Monitor)

    2001-01-01

    An inductively coupled GEC Cell with modified viewing ports has been used to measure in-situ absorption in CF4 plasmas via Fourier Transform Infrared Spectroscopy, and the results compared to those obtained in a standard viewport configuration. The viewing ports were modified so that the window boundary is inside, rather than outside, of the GEC cell. Because the absorption obtained is a spatially integrated absorption, measurements made represent an averaging of absorbing species inside and outside of the plasma. This modification is made to reduce this spatial averaging and thus allow a more accurate estimation of neutral species concentrations and temperatures within the plasmas. By reducing this pathlength, we find that the apparent CF4 consumption increases from 65% to 95% and the apparent vibrational temperature of CF4 rises by 50-75 K. The apparent fraction of etch product SiF4 decreases from 4% to 2%. The data suggests that these density changes may be due to significant temperature gradients between the plasma and chamber viewports.

  2. Cavity ring-down spectroscopy (CRDS) system for measuring atmospheric mercury using differential absorption

    NASA Astrophysics Data System (ADS)

    Pierce, A.; Obrist, D.; Moosmuller, H.; Moore, C.

    2012-04-01

    Atmospheric elemental mercury (Hg0) is a globally pervasive element that can be transported and deposited to remote ecosystems where it poses — particularly in its methylated form — harm to many organisms including humans. Current techniques for measurement of atmospheric Hg0 require several liters of sample air and several minutes for each analysis. Fast-response (i.e., 1 second or faster) measurements would improve our ability to understand and track chemical cycling of mercury in the atmosphere, including high frequency Hg0 fluctuations, sources and sinks, and chemical transformation processes. We present theory, design, challenges, and current results of our new prototype sensor based on cavity ring-down spectroscopy (CRDS) for fast-response measurement of Hg0 mass concentrations. CRDS is a direct absorption technique that implements path-lengths of multiple kilometers in a compact absorption cell using high-reflectivity mirrors, thereby improving sensitivity and reducing sample volume compared to conventional absorption spectroscopy. Our sensor includes a frequency-doubled, dye-laser emitting laser pulses tunable from 215 to 280 nm, pumped by a Q-switched, frequency tripled Nd:YAG laser with a pulse repetition rate of 50 Hz. We present how we successfully perform automated wavelength locking and stabilization of the laser to the peak Hg0 absorption line at 253.65 nm using an external isotopically-enriched mercury (202Hg0) cell. An emphasis of this presentation will be on the implementation of differential absorption measurement whereby measurements are alternated between the peak Hg0 absorption wavelength and a nearby wavelength "off" the absorption line. This can be achieved using a piezo electric tuning element that allows for pulse-by-pulse tuning and detuning of the laser "online" and "offline" of the Hg absorption line, and thereby allows for continuous correction of baseline extinction losses. Unexpected challenges with this approach included

  3. Near-IR diode laser absorption for measurement of tropospheric HO2

    NASA Technical Reports Server (NTRS)

    Stanton, Alan C.

    1994-01-01

    The possibility of using tunable lead salt diode lasers in the infrared for measurement of tropospheric HO2 has been frequently considered. Although the sensitivity of diode laser absorption has been improved through the use of high frequency detection techniques, nature has been unkind in that the HO2 absorption cross sections are weak. Even using the most optimistic assumptions about attainable path length and detectable absorbance, measurement of tropospheric HO2 by diode laser absorption in the mid-IR appears marginal. A possible alternative method for measuring HO2 is by absorption at near-infrared wavelengths. Several absorption bands of HO2 occur in the wavelength region between 1.2 and 1.6 micron due to electronic transitions and overtones of the fundamental vibrational modes. InGaAsP diode lasers operate in this wavelength region and can be used for high resolution spectroscopy in a manner analogous to the lead salt lasers. A diode laser system in the near-IR offers some advantages.

  4. Measurement and feature analysis of absorption spectra of four algal species

    NASA Astrophysics Data System (ADS)

    Zhu, Jianhua; Zhou, Hongli; Han, Bing; Li, Tongji

    2016-04-01

    Two methods for particulate pigments (i.e., quantitative filter technique, QFT, and in vivo measurement, InVivo, respectively) and two methods for dissolved pigments (i.e., Acetone Extracts, AceEx, and high-performance liquid chromatography, HPLC, respectively) were used to obtain the optical absorption coefficient spectra for cultures of four typical algal species. Through normalization and analysis of the spectra, it is shown that (1) the four methods are able to measure optical absorption spectra of particulate and/or dissolved pigments; (2) that the optical absorption spectra of particulate and dissolved pigments were consistent in terms of the peak position in the blue wavelength, and the difference of the peak position in the near infrared wavelength was ~10 nm between each other; and (3) that the leveling effect of the absorption spectra of particulate pigments was significant. These four methods can all effectively measure the absorption coefficients of phytoplankton pigments, while each one has its unique advantages in different applications. Therefore, appropriate method should be carefully selected for various application due to their intrinsic difference.

  5. Measurement and feature analysis of absorption spectra of four algal species

    NASA Astrophysics Data System (ADS)

    Zhu, Jianhua; Zhou, Hongli; Han, Bing; Li, Tongji

    2017-03-01

    Two methods for particulate pigments (i.e., quantitative filter technique, QFT, and in vivo measurement, InVivo, respectively) and two methods for dissolved pigments (i.e., Acetone Extracts, AceEx, and high-performance liquid chromatography, HPLC, respectively) were used to obtain the optical absorption coefficient spectra for cultures of four typical algal species. Through normalization and analysis of the spectra, it is shown that (1) the four methods are able to measure optical absorption spectra of particulate and/or dissolved pigments; (2) that the optical absorption spectra of particulate and dissolved pigments were consistent in terms of the peak position in the blue wavelength, and the difference of the peak position in the near infrared wavelength was 10 nm between each other; and (3) that the leveling effect of the absorption spectra of particulate pigments was significant. These four methods can all effectively measure the absorption coefficients of phytoplankton pigments, while each one has its unique advantages in different applications. Therefore, appropriate method should be carefully selected for various application due to their intrinsic difference.

  6. Excited-state absorption measurements of Tm3+-doped crystals

    NASA Astrophysics Data System (ADS)

    Szela, J. W.; Mackenzie, J. I.

    2012-06-01

    High resolution, absolute excited-state absorption (ESA) spectra, at room temperature, from the long-lived 3F4 energy level of several crystals doped with trivalent thulium (Tm3+) ions have been measured employing high-brightness narrowband (FWHM <30 nm) light emitting diodes (LEDs) as a probe wavelength. The aim of this investigation was to determine the strength of ESA channels at wavelengths addressable by commercially available semiconductor laser diodes operating around 630-680 nm. The favourable lifetime of the 3F4 manifold and negligible ground-state absorption (GSA) for the red-wavelength second-step excitation, ensures a direct and efficient route for a dual-wavelength pumping scheme of the thulium ion, which will enable blue-green laser emission from its 1G4 upper-laser level.

  7. Differential absorption and Raman lidar for water vapor profile measurements - A review

    NASA Technical Reports Server (NTRS)

    Grant, William B.

    1991-01-01

    Differential absorption lidar and Raman lidar have been applied to the range-resolved measurements of water vapor density for more than 20 years. Results have been obtained using both lidar techniques that have led to improved understanding of water vapor distributions in the atmosphere. This paper reviews the theory of the measurements, including the sources of systematic and random error; the progress in lidar technology and techniques during that period, including a brief look at some of the lidar systems in development or proposed; and the steps being taken to improve such lidar systems.

  8. Frequency-domain method for measuring spectral properties in multiple-scattering media: methemoglobin absorption spectrum in a tissuelike phantom

    NASA Astrophysics Data System (ADS)

    Fishkin, Joshua B.; So, Peter T. C.; Cerussi, Albert E.; Gratton, Enrico; Fantini, Sergio; Franceschini, Maria Angela

    1995-03-01

    We have measured the optical absorption and scattering coefficient spectra of a multiple-scattering medium (i.e., a biological tissue-simulating phantom comprising a lipid colloid) containing methemoglobin by using frequency-domain techniques. The methemoglobin absorption spectrum determined in the multiple-scattering medium is in excellent agreement with a corrected methemoglobin absorption spectrum obtained from a steady-state spectrophotometer measurement of the optical density of a minimally scattering medium. The determination of the corrected methemoglobin absorption spectrum takes into account the scattering from impurities in the methemoglobin solution containing no lipid colloid. Frequency-domain techniques allow for the separation of the absorbing from the scattering properties of multiple-scattering media, and these techniques thus provide an absolute

  9. A review on creatinine measurement techniques.

    PubMed

    Mohabbati-Kalejahi, Elham; Azimirad, Vahid; Bahrami, Manouchehr; Ganbari, Ahmad

    2012-08-15

    This paper reviews the entire recent global tendency for creatinine measurement. Creatinine biosensors involve complex relationships between biology and micro-mechatronics to which the blood is subjected. Comparison between new and old methods shows that new techniques (e.g. Molecular Imprinted Polymers based algorithms) are better than old methods (e.g. Elisa) in terms of stability and linear range. All methods and their details for serum, plasma, urine and blood samples are surveyed. They are categorized into five main algorithms: optical, electrochemical, impedometrical, Ion Selective Field-Effect Transistor (ISFET) based technique and chromatography. Response time, detection limit, linear range and selectivity of reported sensors are discussed. Potentiometric measurement technique has the lowest response time of 4-10 s and the lowest detection limit of 0.28 nmol L(-1) belongs to chromatographic technique. Comparison between various techniques of measurements indicates that the best selectivity belongs to MIP based and chromatographic techniques.

  10. Studies of cavity enhanced absorption spectroscopy for weak absorption gas measurements

    NASA Astrophysics Data System (ADS)

    Li, Liucheng; Duo, Liping; Gong, Deyu; Ma, Yanhua; Zhang, Zhiguo; Wang, Yuanhu; Zhou, Dongjian; Jin, Yuqi

    2017-01-01

    In order to determine the concentrations of trace amount metastable species in chemical lasers, an off-axis cavity enhanced absorption spectrometer for the detection of weak absorption gases has been built with a noise equivalent absorption sensitivity of 1.6x10-8 cm-1. The absorption spectrum of trace amount gaseous ammonia and water vapor was obtained with a spectral resolution of about 78 MHz. A multiple-line absorption spectroscopic method to determine the temperature of gaseous ammonia has been developed by use of multiple lines of ammonia molecule absorption spectrum.

  11. Aerosol absorption measurement with a sinusoidal phase modulating fiber optic photo thermal interferometer

    NASA Astrophysics Data System (ADS)

    Li, Shuwang; Shao, Shiyong; Mei, Haiping; Rao, Ruizhong

    2016-10-01

    Aerosol light absorption plays an important role in the earth's atmosphere direct and semi-direct radiate forcing, simultaneously, it also has a huge influence on the visibility impairment and laser engineering application. Although various methods have been developed for measuring aerosol light absorption, huge challenge still remains in precision, accuracy and temporal resolution. The main reason is that, as a part of aerosol light extinction, aerosol light absorption always generates synchronously with aerosol light scattering, and unfortunately aerosol light scattering is much stronger in most cases. Here, a novel photo-thermal interferometry is proposed only for aerosol absorption measurement without disturbance from aerosol scattering. The photo-thermal interferometry consists of a sinusoidal phase-modulating single mode fiber-optic interferometer. The thermal dissipation, caused by aerosol energy from photo-thermal conversion when irritated by pump laser through interferometer, is detected. This approach is completely insensitive to aerosol scattering, and the single mode fiber-optic interferometer is compact, low-cost and insensitive to the polarization shading. The theory of this technique is illustrated, followed by the basic structure of the sinusoidal phase-modulating fiber-optic interferometer and demodulation algorithms. Qualitative and quantitative analysis results show that the new photo-thermal interference is a potential approach for aerosol absorption detection and environmental pollution detection.

  12. Liquid crystal quantitative temperature measurement technique

    NASA Astrophysics Data System (ADS)

    Lu, Wei; Wu, Zongshan

    2001-10-01

    Quantitative temperature measurement using wide band thermochromic liquid crystals is an “area” thermal measurement technique. This technique utilizes the feature that liquid crystal changes its reflex light color with variation of temperature and applies an image capturing and processing system to calibrate the characteristic curve of liquid crystal’s color-temperature. Afterwards, the technique uses this curve to measure the distribution of temperature on experimental model. In this paper, firstly, each part of quantitative temperature measurement system using liquid crystal is illustrated and discussed. Then the technique is employed in a long duration hypersonic wind tunnel, and the quantitative result of the heat transfer coefficient along laminar plate is obtained. Additionally, some qualitative results are also given. In the end, comparing the experimental results with reference enthalpy theoretical results, a conclusion of thermal measurement accuracy is drawn.

  13. Research relative to weather radar measurement techniques

    NASA Technical Reports Server (NTRS)

    Smith, Paul L.

    1992-01-01

    Research relative to weather radar measurement techniques, which involves some investigations related to measurement techniques applicable to meteorological radar systems in Thailand, is reported. A major part of the activity was devoted to instruction and discussion with Thai radar engineers, technicians, and meteorologists concerning the basic principles of radar meteorology and applications to specific problems, including measurement of rainfall and detection of wind shear/microburst hazards. Weather radar calibration techniques were also considered during this project. Most of the activity took place during two visits to Thailand, in December 1990 and February 1992.

  14. Estimation of background gas concentration from differential absorption lidar measurements

    NASA Astrophysics Data System (ADS)

    Harris, Peter; Smith, Nadia; Livina, Valerie; Gardiner, Tom; Robinson, Rod; Innocenti, Fabrizio

    2016-10-01

    Approaches are considered to estimate the background concentration level of a target species in the atmosphere from an analysis of the measured data provided by the National Physical Laboratory's differential absorption lidar (DIAL) system. The estimation of the background concentration level is necessary for an accurate quantification of the concentration level of the target species within a plume, which is the quantity of interest. The focus of the paper is on methodologies for estimating the background concentration level and, in particular, contrasting the assumptions about the functional and statistical models that underpin those methodologies. An approach is described to characterise the noise in the recorded signals, which is necessary for a reliable estimate of the background concentration level. Results for measured data provided by a field measurement are presented, and ideas for future work are discussed.

  15. Ground reflectance measurement techniques: a comparison.

    PubMed

    Duggin, M J; Cunia, T

    1983-12-01

    The relative accuracies of reflectance factor measurement methods involving the simultaneous, as compared to the sequential, measurement of irradiance on and radiance reflected from the target are discussed. Data are presented to support a statistical demonstration that the simultaneous measurement technique is the more accurate.

  16. X-ray absorption spectroscopy of Mn doped ZnO thin films prepared by rf sputtering technique

    SciTech Connect

    Yadav, Ashok Kumar; Jha, S. N.; Bhattacharyya, D.; Haque, Sk Maidul; Shukla, Dinesh; Choudhary, Ram Janay

    2015-11-15

    A set of r.f. sputter deposited ZnO thin films prepared with different Mn doping concentrations have been characterised by Extended X-ray Absorption Fine Structure (EXAFS) and X-ray Absorption Near Edge Spectroscopy (XANES) measurements at Zn, Mn and O K edges and at Mn L{sub 2,3} edges apart from long range structural characterisation by Grazing Incident X-ray Diffraction (GIXRD) technique. Magnetic measurements show room temperature ferromagnetism in samples with lower Mn doping which is however, gets destroyed at higher Mn doping concentration. The results of the magnetic measurements have been explained using the local structure information obtained from EXAFS and XANES measurements.

  17. Oscillator strength measurements of atomic absorption lines from stellar spectra

    NASA Astrophysics Data System (ADS)

    Lobel, Alex

    2011-05-01

    Herein we develop a new method to determine oscillator strength values of atomic absorption lines with state-of-the-art detailed spectral synthesis calculations of the optical spectrum of the Sun and of standard spectral reference stars. We update the log(gf) values of 911 neutral lines observed in the KPNO-FTS flux spectrum of the Sun and high-resolution echelle spectra (R = 80 000) of Procyon (F5 IV-V) and Eps Eri (K2 V) observed with large signal-to-noise (S/N) ratios of 2000 using the new Mercator-Hermes spectrograph at La Palma Observatory (Spain). We find for 483 Fe I, 85 Ni I, and 51 Si I absorption lines in the sample a systematic overestimation of the literature log(gf) values with central line depths below 15%. We employ a curve-of-growth analysis technique to test the accuracy of the new oscillator strength values and compare calculated equivalent line widths to the Moore, Minnaert, and Houtgast atlas of the Sun. The online SpectroWeb database at http://spectra.freeshell.org interactively displays the observed and synthetic spectra and provides the new log(gf) values together with important atomic line data. The graphical database is under development for stellar reference spectra of every spectral sub-class observed with large spectral resolution and S/N ratios.

  18. Measurements and Modeling of Aerosol Absorption and Single Scattering Albedo at Ambient Relative Hum

    NASA Technical Reports Server (NTRS)

    Redemann, J.; Russell, P. B.; Hamill, P.

    2000-01-01

    Uncertainties in the aerosol single scattering albedo have been identified to be an important source of errors in current large-scale model estimates of the direct aerosol radiative forcing of climate. A number of investigators have obtained estimates of the single scattering albedo from a variety of remote sensing and in situ measurements during aerosol field experiments. During the Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX, 1996) for example, estimates of the aerosol single scattering albedo were obtained (1) as a best-fit parameter in comparing radiative flux changes measured by airborne pyranometer to those computed from independently measured aerosol properties; (2) from estimates of the aerosol complex index of refraction derived using a combination of airborne sunphotometer, lidar backscatter and in situ size distribution measurements; and (3) from airborne measurements of aerosol scattering and absorption using nephelometers and absorption photometers. In this paper, we briefly compare the results of the latter two methods for two TARFOX case studies, since those techniques provide height-resolved information about the aerosol single scattering albedo. Estimates of the aerosol single scattering albedo from nephelometer and absorption photometer measurements require knowledge of the scattering and absorption humidification (i.e., the increase in these properties in response to an increase in ambient relative humidity), since both measurements are usually carried out at a relative humidity different from the ambient atmosphere. In principle, the scattering humidification factor can be measured, but there is currently no technique widely available to measure the absorption of an aerosol sample as a function of relative humidity. Frequently, for lack of better knowledge, the absorption humidification is assumed to be unity (meaning that there is no change in aerosol absorption due to an increase in ambient relative humidity). This

  19. Measurement of temperature profiles in flames by emission-absorption spectroscopy

    NASA Technical Reports Server (NTRS)

    Simmons, F. S.; Arnold, C. B.; Lindquist, G. H.

    1972-01-01

    An investigation was conducted to explore the use of infrared and ultraviolet emission-absorption spectroscopy for determination of temperature profiles in flames. Spectral radiances and absorptances were measured in the 2.7-micron H2O band and the 3064-A OH band in H2/O2 flames for several temperature profiles which were directly measured by a sodium line-reversal technique. The temperature profiles, determined by inversion of the infrared and ultraviolet spectra, showed an average disagreement with line-reversal measurements of 50 K for the infrared and 200 K for the ultraviolet at a temperature of 2600 K. The reasons for these discrepancies are discussed in some detail.

  20. Resonant tube for measurement of sound absorption in gases at low frequency/pressure ratios

    NASA Technical Reports Server (NTRS)

    Zuckerwar, A. J.; Griffin, W. A.

    1980-01-01

    The paper describes a resonant tube for measuring sound absorption in gases, with specific emphasis on the vibrational relaxation peak of N2, over a range of frequency/pressure ratios from 0.1 to 2500 Hz/atm. The experimental background losses measured in argon agree with the theoretical wall losses except at few isolated frequencies. Rigid cavity terminations, external excitation, and a differential technique of background evaluation were used to minimize spurious contributions to the background losses. Room temperature measurements of sound absorption in binary mixtures of N2-CO2 in which both components are excitable resulted in the maximum frequency/pressure ratio in Hz/atm of 0.063 + 123m for the N2 vibrational relaxation peak, where m is mole percent of added CO2; the maximum ratio for the CO2 peak was 34,500 268m where m is mole percent of added N2.

  1. Measurement of iron absorption from meals contaminated with iron

    SciTech Connect

    Hallberg, L.; Bjoern-Rasmussen, E.

    1981-12-01

    A method is described to measure in vitro the extent of isotopic exchange between the native nonheme food iron and added inorganic reduction to radioiron tracer. The food is digested with pepsin and trypsin in the presence of radioiron. The exchangeability of food iron is calculated from the specific activity in the food and in an extract of bathophenantroline in isoamyl alcohol obtained after digesting this food. The precision and accuracy of the method is illustrated by two kinds of studies, those in which different amounts of contamination iron are added to a meal and those evaluating contamination iron in natural meals. The present method will make it possible to measure validly iron absorption from meals contaminated with unknown amounts of iron of unknown exchangeability with the extrinsic radioiron tracer.

  2. Phase measurement of fast light pulse in electromagnetically induced absorption.

    PubMed

    Lee, Yoon-Seok; Lee, Hee Jung; Moon, Han Seb

    2013-09-23

    We report the phase measurement of a fast light pulse in electromagnetically induced absorption (EIA) of the 5S₁/₂ (F = 2)-5P₃/₂ (F' = 3) transition of ⁸⁷Rb atoms. Using a beat-note interferometer method, a stable measurement without phase dithering of the phase of the probe pulse before and after it has passed through the EIA medium was achieved. Comparing the phases of the light pulse in air and that of the fast light pulse though the EIA medium, the phase of the fast light pulse at EIA resonance was not shifted and maintained to be the same as that of the free-space light pulse. The classical fidelity of the fast light pulse according to the advancement of the group velocity by adjusting the atomic density was estimated to be more than 97%.

  3. Experimental Techniques for Thermodynamic Measurements of Ceramics

    NASA Technical Reports Server (NTRS)

    Jacobson, Nathan S.; Putnam, Robert L.; Navrotsky, Alexandra

    1999-01-01

    Experimental techniques for thermodynamic measurements on ceramic materials are reviewed. For total molar quantities, calorimetry is used. Total enthalpies are determined with combustion calorimetry or solution calorimetry. Heat capacities and entropies are determined with drop calorimetry, differential thermal methods, and adiabatic calorimetry . Three major techniques for determining partial molar quantities are discussed. These are gas equilibration techniques, Knudsen cell methods, and electrochemical techniques. Throughout this report, issues unique to ceramics are emphasized. Ceramic materials encompass a wide range of stabilities and this must be considered. In general data at high temperatures is required and the need for inert container materials presents a particular challenge.

  4. Optical Measurement Technique for Space Column Characterization

    NASA Technical Reports Server (NTRS)

    Barrows, Danny A.; Watson, Judith J.; Burner, Alpheus W.; Phelps, James E.

    2004-01-01

    A simple optical technique for the structural characterization of lightweight space columns is presented. The technique is useful for determining the coefficient of thermal expansion during cool down as well as the induced strain during tension and compression testing. The technique is based upon object-to-image plane scaling and does not require any photogrammetric calibrations or computations. Examples of the measurement of the coefficient of thermal expansion are presented for several lightweight space columns. Examples of strain measured during tension and compression testing are presented along with comparisons to results obtained with Linear Variable Differential Transformer (LVDT) position transducers.

  5. In-flight aeroelastic measurement technique development

    NASA Astrophysics Data System (ADS)

    Burner, Alpheus W.; Lokos, William A.; Barrows, Danny A.

    2003-11-01

    The initial concept and development of a low-cost, adaptable method for the measurement of static and dynamic aeroelastic deformation of aircraft during flight testing is presented. The method is adapted from a proven technique used in wind tunnel testing to measure model deformation, often referred to as the videogrammetric model deformation (or VMD) technique. The requirements for in-flight measurements are compared and contrasted with those for wind tunnel testing. The methodology for the proposed measurements and differences compared with that used for wind tunnel testing is given. Several error sources and their effects are identified. Measurement examples using the new technique, including change in wing twist and deflection as a function of time, from an F/A-18 research aircraft at NASA's Dryden Flight Research Center are presented.

  6. Laser Doppler measurement techniques for spacecraft

    NASA Technical Reports Server (NTRS)

    Kinman, Peter W.; Gagliardi, Robert M.

    1986-01-01

    Two techniques are proposed for using laser links to measure the relative radial velocity of two spacecraft. The first technique determines the relative radial velocity from a measurement of the two-way Doppler shift on a transponded radio-frequency subcarrier. The subcarrier intensity-modulates reciprocating laser beams. The second technique determines the relative radial velocity from a measurement of the two-way Doppler shift on an optical frequency carrier which is transponded between spacecraft using optical Costas loops. The first technique might be used in conjunction with noncoherent optical communications, while the second technique is compatible with coherent optical communications. The first technique simultaneously exploits the diffraction advantage of laser beams and the maturity of radio-frequency phase-locked loop technology. The second technique exploits both the diffraction advantage of laser beams and the large Doppler effect at optical frequencies. The second technique has the potential for greater accuracy; unfortunately, it is more difficult to implement since it involves optical Costas loops.

  7. Techniques For Optical Measurement Of Registration

    NASA Astrophysics Data System (ADS)

    Zych, L. J.; Spadini, G.

    1985-07-01

    This paper discusses an optical technique capable of reliably measuring registration to few hundredths of a micron on virtually any layer. It has overcome the accuracy limitations and the proximity effect error present in other optical techniques. In spite of the recent popularity of highly accurate computerized electrical registration measurements optical registration measurements are still popular and necessary. This is because nonconductive layers, including resist, cannot be measured electrically. A quick optical technique with a high degree of accuracy has been developed and put to use. The measurement is made through a microscope, and a computer pattern recognition follows. It is free of the resolution limits inherent in such structures as optical verniers, which are bound to typically 0.1 microns by the grid size used to make the mask. This method employs a direct optical misalignment measurement between two matching structures and is capable of resolving 0.01 microns. It is also free of the proximity effects which make many verniers and pattern recognition schemes inaccurate. Proper microscope calibration, adjustments, and pattern recognition algorithms are key in making this technique work. The apertures must be accurately aligned and the focus properly adjusted to provide the right image. An HP 9000-226 computer has been custom interfaced to a Leitz microscope and a set of algorithms written. The result is a highly accurate, fast, and user friendly optical measurement system capable of measuring registration on all layers.

  8. Wastewater Sampling Methodologies and Flow Measurement Techniques.

    ERIC Educational Resources Information Center

    Harris, Daniel J.; Keffer, William J.

    This document provides a ready source of information about water/wastewater sampling activities using various commercial sampling and flow measurement devices. The report consolidates the findings and summarizes the activities, experiences, sampling methods, and field measurement techniques conducted by the Environmental Protection Agency (EPA),…

  9. Review of air flow measurement techniques

    SciTech Connect

    McWilliams, Jennifer

    2002-12-01

    Airflow measurement techniques are necessary to determine the most basic of indoor air quality questions: ''Is there enough fresh air to provide a healthy environment for the occupants of the building?'' This paper outlines airflow measurement techniques, but it does not make recommendations for techniques that should be used. The airflows that will be discussed are those within a room or zone, those between rooms or zones, such as through doorways (open or closed) or passive vents, those between the building and outdoors, and those through mechanical air distribution systems. Techniques that are highlighted include particle streak velocimetry, hot wire anemometry, fan pressurization (measuring flow at a given pressure), tracer gas, acoustic methods for leak size determination, the Delta Q test to determine duct leakage flows, and flow hood measurements. Because tracer gas techniques are widely used to measure airflow, this topic is broken down into sections as follows: decay, pulse injection, constant injection, constant concentration, passive sampling, and single and multiple gas measurements for multiple zones.

  10. A quality control technique based on UV-VIS absorption spectroscopy for tequila distillery factories

    NASA Astrophysics Data System (ADS)

    Barbosa Garcia, O.; Ramos Ortiz, G.; Maldonado, J. L.; Pichardo Molina, J.; Meneses Nava, M. A.; Landgrave, Enrique; Cervantes, M. J.

    2006-02-01

    A low cost technique based on the UV-VIS absorption spectroscopy is presented for the quality control of the spirit drink known as tequila. It is shown that such spectra offer enough information to discriminate a given spirit drink from a group of bottled commercial tequilas. The technique was applied to white tequilas. Contrary to the reference analytic methods, such as chromatography, for this technique neither special personal training nor sophisticated instrumentations is required. By using hand-held instrumentation this technique can be applied in situ during the production process.

  11. Detection of water vapour absorption around 363nm in measured atmospheric absorption spectra and its effect on DOAS evaluations

    NASA Astrophysics Data System (ADS)

    Lampel, Johannes; Polyansky, Oleg. L.; Kyuberis, Alexandra A.; Zobov, Nikolai F.; Tennyson, Jonathan; Lodi, Lorenzo; Pöhler, Denis; Frieß, Udo; Platt, Ulrich; Beirle, Steffen; Wagner, Thomas

    2016-04-01

    Water vapour is known to absorb light from the microwave region to the blue part of the visible spectrum at a decreasing magnitude. Ab-initio approaches to model individual absorption lines of the gaseous water molecule predict absorption lines until its dissociation limit at 243 nm. We present first evidence of water vapour absorption at 363 nm from field measurements based on the POKAZATEL absorption line list by Polyansky et al. (2016) using data from Multi-Axis differential optical absorption spectroscopy (MAX-DOAS) and Longpath (LP)-DOAS measurements. The predicted absorptions contribute significantly to the observed optical depths with up to 2 × 10-3. Their magnitude correlates well (R2 = 0.89) to simultaneously measured well-established water vapour absorptions in the blue spectral range from 452-499 nm, but is underestimated by a factor of 2.6 ± 0.6 in the ab-initio model. At a spectral resolution of 0.5nm this leads to a maximum absorption cross-section value of 5.4 × 10-27 cm2/molec at 362.3nm. The results are independent of the employed cross-section data to compensate for the overlayed absorption of the oxygen dimer O4. The newly found absorption can have a significant impact on the spectral retrieval of absorbing trace-gas species in the spectral range around 363 nm. Its effect on the spectral analysis of O4, HONO and OClO are discussed.

  12. Elementary reaction rate measurements at high temperatures by tunable-laser flash-absorption

    SciTech Connect

    Hessler, J.P.

    1993-12-01

    The major objective of this program is to measure thermal rate coefficients and branching ratios of elementary reactions. To perform these measurements, the authors constructed an ultrahigh-purity shock tube to generate temperatures between 1000 and 5500 K. The tunable-laser flash-absorption technique is used to measure the rate of change of the concentration of species which absorb below 50,000 cm{sup {minus}1} e.g.: OH, CH, and CH{sub 3}. This technique is being extended into the vacuum-ultraviolet spectral region where one can measure atomic species e.g.: H, D, C, O, and N; and diatomic species e.g.: O{sub 2}, CO, and OH.

  13. Atmospheric Pre-Corrected Differential Absorption Techniques to Retrieve Columnar Water Vapor: Application to AVIRIS 91/95 Data

    NASA Technical Reports Server (NTRS)

    Schlaepfer, Daniel; Borel, Christoph C.; Keller, Johannes; Itten, Klaus I.

    1996-01-01

    Water vapor is one of the main forces for weather development as well as for mesoscale air transport processes. The monitoring of water vapor is therefore an important aim in remote sensing of the atmosphere. Current operational systems for water vapor detection use primarily the emission in the thermal infrared (AVHRR, GOES, ATSR, Meteosat) or in the microwave radiation bands (DMSP). The disadvantage of current satellite systems is either a coarse spatial (horizontal) resolution ranging from one to tens of kilometers or a limited insight into the lower atmosphere. Imaging spectrometry on the other hand measures total column water vapor contents at a high spatial horizontal resolution and has therefore the potential of filling these gaps. The sensors of the AVIRIS instrument are capable of acquiring hyperspectral data in 224 bands located in the visible and near infrared at 10 nm resolution. This data includes the information on constituents of the earth's surface as well as of the atmosphere. The optical measurement of water vapor can be performed using sensor channels located in bands or lines of the absorption spectrum. The AVIRIS sensor has been used to retrieve water vapor and with less accuracy carbon dioxide, oxygen and ozone. To retrieve the water vapor amount, the so called differential absorption technique has been applied. The goal of this technique is to eliminate background factors by taking a ratio between channels within the absorption band and others besides the band. Various ratioing methods on the basis of different channels and calculation techniques were developed. The influence of a trace gas of interest on the radiance at the sensor level is usually simulated by using radiative transfer codes. In this study, the spectral transmittance and radiance are calculated by MODTRAN3 simulations with the new DISORT option. The objective of this work is to test the best performing differential absorption techniques for imaging spectrometry of

  14. Aerosol absorption measurement at SWIR with water vapor interference using a differential photoacoustic spectrometer.

    PubMed

    Zhu, Wenyue; Liu, Qiang; Wu, Yi

    2015-09-07

    Atmospheric aerosol plays an important role in atmospheric radiation balance through absorbing and scattering the solar radiation, which changes local weather and global climate. Accurate measurement is highly requested to estimate the radiative effects and climate effects of atmospheric aerosol. Photoacoustic spectroscopy (PAS) technique, which observes the aerosols on their natural suspended state and is insensitive to light scattering, is commonly recognized as one of the best candidates to measure the optical absorption coefficient (OAC) of aerosols. In the present work, a method of measuring aerosol OAC at the wavelength where could also be absorbed by water vapor was proposed and corresponding measurements of the absorption properties of the atmospheric aerosol at the short wave infrared (SWIR, 1342 nm) wavelength were carried out. The spectrometer was made up of two high performance homemade photoacoustic cells. To improve the sensitivity, several methods were presented to control the noise derived from gas flow and vibration from the sampling pump. Calibration of the OAC and properties of the system were also studied in detail. Using the established PAS instrument, measurement of the optical absorption properties of the atmospheric aerosol were carried out in laboratory and field environment.

  15. Coherent differential absorption lidar for combined measurement of wind and trace atmospheric gases

    NASA Astrophysics Data System (ADS)

    Koch, Grady James

    A lidar system was developed for making combined range-resolved measurements of wind speed and direction, water vapor concentration, and carbon dioxide concentration in the atmosphere. This lidar combines the coherent Doppler technique for wind detection and the differential absorption lidar (DIAL) technique to provide a multifunctional capability. DIAL and coherent lidars have traditionally been thought of and implemented as separate instruments, but the research reported here has shown a demonstration of combining the coherent and DIAL techniques into a single instrument using solid-state lasers. The lasers used are of Ho:Tm:YLF, which operates at a wavelength of 2 mum. This wavelength is a further advantage to the lidar, as this wavelength offers a much higher level of eyesafety than shorter wavelengths conventionally used for DIAL. Two generations are lidars are described, with the first design making combined measurement of wind and water vapor. Wind speed measurements are shown of a precision better than 1 m/s, making it useful for many meteorological applications. Water vapor concentration measurements were of 86% accuracy, requiring improvement for scientific applications. This preliminary experiment revealed the largest source of error in concentration measurement to be a lack of stability in the wavelength of the laser. This problem was solved by implementing a means to precisely control the continuous-wave laser that injection seeds a pulsed laser. The finely tunable Ho:Tm:YLF laser was stabilized to absorption lines of both carbon dioxide and water vapor using a wavelength modulation technique. Long-term stabilization to within 13.5 MHz of absorption line center is shown, representing the first frequency-stabilized laser at or within 500 run of 2mum wavelength. Results are presented on injection seeding a pulsed Ho:Tm:YLF laser to impart the tunability and stabilization to the pulsed laser output. The stabilized laser system was incorporated into a

  16. Pressure Measurement in Supersonic Air Flow by Differential Absorptive Laser-Induced Thermal Acoustics

    NASA Technical Reports Server (NTRS)

    Hart, Roger C.; Herring, Gregory C.; Balla, Robert J.

    2007-01-01

    Nonintrusive, off-body flow barometry in Mach-2 airflow has been demonstrated in a large-scale supersonic wind tunnel using seedless laser-induced thermal acoustics (LITA). The static pressure of the gas flow is determined with a novel differential absorption measurement of the ultrasonic sound produced by the LITA pump process. Simultaneously, stream-wise velocity and static gas temperature of the same spatially-resolved sample volume were measured with this nonresonant time-averaged LITA technique. Mach number, temperature and pressure have 0.2%, 0.4%, and 4% rms agreement, respectively, in comparison with known free-stream conditions.

  17. Pressure measurement in supersonic air flow by differential absorptive laser-induced thermal acoustics.

    PubMed

    Hart, Roger C; Herring, G C; Balla, R Jeffrey

    2007-06-15

    Nonintrusive, off-body flow barometry in Mach 2 airflow has been demonstrated in a large-scale supersonic wind tunnel using seedless laser-induced thermal acoustics (LITA). The static pressure of the gas flow is determined with a novel differential absorption measurement of the ultrasonic sound produced by the LITA pump process. Simultaneously, the streamwise velocity and static gas temperature of the same spatially resolved sample volume were measured with this nonresonant time-averaged LITA technique. Mach number, temperature, and pressure have 0.2%, 0.4%, and 4% rms agreement, respectively, in comparison with known free-stream conditions.

  18. Cavity-enhanced measurements of hydrogen peroxide absorption cross sections from 353 to 410 nm.

    PubMed

    Kahan, Tara F; Washenfelder, Rebecca A; Vaida, Veronica; Brown, Steven S

    2012-06-21

    We report near-ultraviolet and visible absorption cross sections of hydrogen peroxide (H(2)O(2)) using incoherent broad-band cavity-enhanced absorption spectroscopy (IBBCEAS), a recently developed, high-sensitivity technique. The measurements reported here span the range of 353-410 nm and extend published electronic absorption cross sections by 60 nm to absorption cross sections below 1 × 10(-23) cm(2) molecule(-1). We have calculated photolysis rate constants for H(2)O(2) in the lower troposphere at a range of solar zenith angles by combining the new measurements with previously reported data at wavelengths shorter than 350 nm. We predict that photolysis at wavelengths longer than those included in the current JPL recommendation may account for up to 28% of the total hydroxyl radical (OH) production from H(2)O(2) photolysis under some conditions. Loss of H(2)O(2) via photolysis may be of the same order of magnitude as reaction with OH and dry deposition in the lower atmosphere; these processes have very different impacts on HO(x) loss and regeneration.

  19. Diffuse reflectance spectroscopy as a tool to measure the absorption coefficient in skin: system calibration.

    PubMed

    Karsten, A E; Singh, A; Karsten, P A; Braun, M W H

    2013-02-01

    An individualised laser skin treatment may enhance the treatment and reduces risks and side-effects. The optical properties (absorption and scattering coefficients) are important parameters in the propagation of laser light in skin tissue. The differences in the melanin content of different skin phototypes influence the absorption of the light. The absorption coefficient at the treatment wavelength for an individual can be determined by diffuse reflectance spectroscopy, using a probe containing seven fibres. Six of the fibres deliver the light to the measurement site and the central fibre collects the diffused reflected light. This is an in vivo technique, offering benefits for near-real-time results. Such a probe, with an effective wavelength band from 450 to 800 nm, was used to calibrate skin-simulating phantoms consisting of intralipid and ink. The calibration constants were used to calculate the absorption coefficients from the diffuse reflectance measurements of three volunteers (skin phototypes, II, IV and V) for sun-exposed and non-exposed areas on the arm.

  20. Infrared Spectroscopy of Explosives Residues: Measurement Techniques and Spectral Analysis

    SciTech Connect

    Phillips, Mark C.; Bernacki, Bruce E.

    2015-03-11

    Infrared laser spectroscopy of explosives is a promising technique for standoff and non-contact detection applications. However, the interpretation of spectra obtained in typical standoff measurement configurations presents numerous challenges. Understanding the variability in observed spectra from explosives residues and particles is crucial for design and implementation of detection algorithms with high detection confidence and low false alarm probability. We discuss a series of infrared spectroscopic techniques applied toward measuring and interpreting the reflectance spectra obtained from explosives particles and residues. These techniques utilize the high spectral radiance, broad tuning range, rapid wavelength tuning, high scan reproducibility, and low noise of an external cavity quantum cascade laser (ECQCL) system developed at Pacific Northwest National Laboratory. The ECQCL source permits measurements in configurations which would be either impractical or overly time-consuming with broadband, incoherent infrared sources, and enables a combination of rapid measurement speed and high detection sensitivity. The spectroscopic methods employed include standoff hyperspectral reflectance imaging, quantitative measurements of diffuse reflectance spectra, reflection-absorption infrared spectroscopy, microscopic imaging and spectroscopy, and nano-scale imaging and spectroscopy. Measurements of explosives particles and residues reveal important factors affecting observed reflectance spectra, including measurement geometry, substrate on which the explosives are deposited, and morphological effects such as particle shape, size, orientation, and crystal structure.

  1. Solar Cell Calibration and Measurement Techniques

    NASA Technical Reports Server (NTRS)

    Bailey, Sheila; Brinker, Dave; Curtis, Henry; Jenkins, Phillip; Scheiman, Dave

    2004-01-01

    The increasing complexity of space solar cells and the increasing international markets for both cells and arrays has resulted in workshops jointly sponsored by NASDA, ESA and NASA. These workshops are designed to obtain international agreement on standardized values for the AMO spectrum and constant, recommend laboratory measurement practices and establish a set of protocols for international comparison of laboratory measurements. A working draft of an ISO standard, WD15387, "Requirements for Measurement and Calibration Procedures for Space Solar Cells" was discussed with a focus on the scope of the document, a definition of primary standard cell, and required error analysis for all measurement techniques. Working groups addressed the issues of Air Mass Zero (AMO) solar constant and spectrum, laboratory measurement techniques, and te international round robin methodology. A summary is presented of the current state of each area and the formulation of the ISO document.

  2. Solar Cell Calibration and Measurement Techniques

    NASA Technical Reports Server (NTRS)

    Bailey, Sheila; Brinker, Dave; Curtis, Henry; Jenkins, Phillip; Scheiman, Dave

    1997-01-01

    The increasing complexity of space solar cells and the increasing international markets for both cells and arrays has resulted in workshops jointly sponsored by NASDA, ESA and NASA. These workshops are designed to obtain international agreement on standardized values for the AMO spectrum and constant, recommend laboratory measurement practices and establish a set of protocols for international comparison of laboratory measurements. A working draft of an ISO standard, WDI 5387, 'Requirements for Measurement and Calibration Procedures for Space Solar Cells' was discussed with a focus on the scope of the document, a definition of primary standard cell, and required error analysis for all measurement techniques. Working groups addressed the issues of Air Mass Zero (AMO) solar constant and spectrum, laboratory measurement techniques, and the international round robin methodology. A summary is presented of the current state of each area and the formulation of the ISO document.

  3. Radionuclide counting technique for measuring wind velocity

    SciTech Connect

    Singh, J.J.; Khandelwal, G.S.

    1981-12-01

    A technique for measuring wind velocities of meteorological interest is described. It is based on inverse-square-law variation of the counting rates as the radioactive source-to-counter distance is changed by wind drag on the source ball. Results of a feasibility study using a weak bismuth 207 radiation source and three Geiger-Muller radiation counters are reported. The use of the technique is not restricted to Martian or Mars-like environments. A description of the apparatus, typical results, and frequency response characteristics are included. A discussion of a double-pendulum arrangement is presented. Measurements reported herein indicate that the proposed technique may be suitable for measuring wind speeds up to 100 m/sec, which are either steady or whose rates of fluctuation are less than 1 kHz.

  4. An intercomparison of five ammonia measurement techniques

    NASA Technical Reports Server (NTRS)

    Williams, E. J.; Sandholm, S. T.; Bradshaw, J. D.; Schendel, J. S.; Langford, A. O.; Quinn, P. K.; Lebel, P. J.; Vay, S. A.; Roberts, P. D.; Norton, R. B.

    1992-01-01

    Results obtained from five techniques for measuring gas-phase ammonia at low concentration in the atmosphere are compared. These methods are: (1) a photofragmentation/laser-induced fluorescence (PF/LIF) instrument; (2) a molybdenum oxide annular denuder sampling/chemiluminescence detection technique; (3) a tungsten oxide denuder sampling/chemiluminescence detection system; (4) a citric-acid-coated denuder sampling/ion chromatographic analysis (CAD/IC) method; and (5) an oxalic-acid-coated filter pack sampling/colorimetric analysis method. It was found that two of the techniques, the PF/LIF and the CAD/IC methods, measured approximately 90 percent of the calculated ammonia added in the spiking tests and agreed very well with each other in the ambient measurements.

  5. Is There a Common Correction for Biases in Historic Filter-Based Aerosol Absorption Measurements?

    NASA Astrophysics Data System (ADS)

    McComiskey, A. C.; Jefferson, A.; Dubey, M. K.; Aiken, A. C.; Fast, J. D.; Flynn, C. J.; Kassianov, E.

    2014-12-01

    Improved characterization of aerosol absorption is a pressing need for improving estimates of climate forcing by aerosols. Measurements of aerosol absorption are difficult to make with the accuracy and precision demanded by climate science. While several different approaches have been employed and new techniques have emerged, none can yet be considered a true 'gold standard'. Instruments that use filter-based methods have been the most widely used and are the basis of historic records. However, several studies using direct photoacoustic techniques have shown that filter-based measurements can be biased relative to these direct measurements. It has been demonstrated that this bias depends strongly on aerosol chemical composition, specifically concentration of organic mass. The wealth of information in the extensive set of historical filter-based data demands that this bias be diagnosed and corrected. A correction is critical for proper evaluation and development of chemical transport models, improved retrievals from remote sensing measurements, and integrating aerosol absorption surface and sub-orbital in situ measurements with knowledge gained from these other approaches. We have performed an intercomparison of absorption coefficients from a photoacoustic and two filter-based instruments with co-located organic mass concentrations from continuous, half-hourly averaged measurements over six months at a remote, continental site in the US (ARM SGP). The results show a bias in the filter-based measurements with organic concentration that is consistent with previous studies. Previous results come from controlled lab studies or field campaigns where absorption coefficients and organic concentrations are high and may represent aerosol close to the source. The current study is important in that these quantities are much lower and the aerosol likely more aged, representing a larger portion of the global conditions, yet shows a similar bias. This site provides other measures

  6. X-ray absorption fine structure measurement with a 9 V electric battery x-ray emitter

    SciTech Connect

    Mitsuya, Shota; Ishii, Hideshi; Kawai, Jun; Tanaka, Keiichi

    2006-09-25

    X-ray absorption spectral analysis is a well known technique for analyzing the chemical environment of an element in a specimen. It has been believed that high intensity and monochromatized x rays such as the synchrotron radiation are required for an x-ray absorption experiment. In the present study, however, we demonstrate that the x-ray absorption spectral measurement of transition metal foils with an energy resolution of 10 eV is possible with a combination of a 9 V dry electric battery pyroelectric x-ray generator and a superconducting microcalorimeter.

  7. Absorption/transmission measurements of PSAP particle-laden filters from the Biomass Burning Observation Project (BBOP) field campaign

    SciTech Connect

    Presser, Cary; Nazarian, Ashot; Conny, Joseph M.; Chand, Duli; Sedlacek, Arthur; Hubbe, John M.

    2016-12-02

    Absorptivity measurements with a laser-heating approach, referred to as the laser-driven thermal reactor (LDTR), were carried out in the infrared and applied at ambient (laboratory) nonreacting conditions to particle-laden filters from a three-wavelength (visible) particle/soot absorption photometer (PSAP). Here, the particles were obtained during the Biomass Burning Observation Project (BBOP) field campaign. The focus of this study was to determine the particle absorption coefficient from field-campaign filter samples using the LDTR approach, and compare results with other commercially available instrumentation (in this case with the PSAP, which has been compared with numerous other optical techniques).

  8. Contact sponge water absorption test implemented for in situ measures

    NASA Astrophysics Data System (ADS)

    Gaggero, Laura; Scrivano, Simona

    2016-04-01

    The contact sponge method is a non-destructive in-situ methodology used to estimate a water uptake coefficient. The procedure, unlike other in-situ measurement was proven to be directly comparable to the water uptake laboratory measurements, and was registered as UNI 11432:2011. The UNI Normal procedure requires to use a sponge with known density, soaked in water, weighed, placed on the material for 1 minute (UNI 11432, 2011; Pardini & Tiano, 2004), then weighed again. Difficulties arise in operating on test samples or on materials with porosity varied for decay. While carrying on the test, fluctuations in the bearing of the environmental parameters were negligible, but not the pressure applied to the surface, that induced the release of different water amounts towards the material. For this reason we designed a metal piece of the same diameter of the plate carrying the sponge, to be screwed at the tip of a pocket penetrometer. With this instrument the sponge was kept in contact with the surface for 1 minute applying two different loads, at first pushed with 0.3 kg/cm2 in order to press the sponge, but not its holder, against the surface. Then, a load of 1.1 kg/ cm2 was applied, still avoiding deviating the load to the sponge holder. We applied both the current and our implemented method to determine the water absorption by contact sponge on 5 fresh rock types (4 limestones: Fine - and Coarse grained Pietra di Vicenza, Rosso Verona, Breccia Aurora, and the silicoclastic Macigno sandstone). The results show that 1) the current methodology imply manual skill and experience to produce a coherent set of data; the variable involved are in fact not only the imposed pressure but also the compression mechanics. 2) The control on the applied pressure allowed reproducible measurements. Moreover, 3) the use of a thicker sponge enabled to apply the method even on rougher surfaces, as the device holding the sponge is not in contact with the tested object. Finally, 4) the

  9. Near simultaneous measurements of NO2 and NO3 over tropics by ground-based absorption spectroscopy

    NASA Technical Reports Server (NTRS)

    Lal, M.; Chakrabarty, D. K.; Sidhu, J. S.; Das, S. R.

    1994-01-01

    The present study concentrates on measurements of NO2 and NO3. NO2 has been measured during twilight period using zenith sky absorption spectrometric technique in the 436 to 448 nm region. NO3 has been measured during night time using direct moon as a source of light in the 655 to 667 nm region. These measurements have been taken at low latitude station, Ahmedabad (23 deg N, 76 deg E), India for the past two years.

  10. Method for improving terahertz band absorption spectrum measurement accuracy using noncontact sample thickness measurement.

    PubMed

    Li, Zhi; Zhang, Zhaohui; Zhao, Xiaoyan; Su, Haixia; Yan, Fang; Zhang, Han

    2012-07-10

    The terahertz absorption spectrum has a complex nonlinear relationship with sample thickness, which is normally measured mechanically with limited accuracy. As a result, the terahertz absorption spectrum is usually determined incorrectly. In this paper, an iterative algorithm is proposed to accurately determine sample thickness. This algorithm is independent of the initial value used and results in convergent calculations. Precision in sample thickness can be improved up to 0.1 μm. A more precise absorption spectrum can then be extracted. By comparing the proposed method with the traditional method based on mechanical thickness measurements, quantitative analysis experiments on a three-component amino acid mixture shows that the global error decreased from 0.0338 to 0.0301.

  11. Measuring Food Intake and Nutrient Absorption in Caenorhabditis elegans.

    PubMed

    Gomez-Amaro, Rafael L; Valentine, Elizabeth R; Carretero, Maria; LeBoeuf, Sarah E; Rangaraju, Sunitha; Broaddus, Caroline D; Solis, Gregory M; Williamson, James R; Petrascheck, Michael

    2015-06-01

    Caenorhabditis elegans has emerged as a powerful model to study the genetics of feeding, food-related behaviors, and metabolism. Despite the many advantages of C. elegans as a model organism, direct measurement of its bacterial food intake remains challenging. Here, we describe two complementary methods that measure the food intake of C. elegans. The first method is a microtiter plate-based bacterial clearing assay that measures food intake by quantifying the change in the optical density of bacteria over time. The second method, termed pulse feeding, measures the absorption of food by tracking de novo protein synthesis using a novel metabolic pulse-labeling strategy. Using the bacterial clearance assay, we compare the bacterial food intake of various C. elegans strains and show that long-lived eat mutants eat substantially more than previous estimates. To demonstrate the applicability of the pulse-feeding assay, we compare the assimilation of food for two C. elegans strains in response to serotonin. We show that serotonin-increased feeding leads to increased protein synthesis in a SER-7-dependent manner, including proteins known to promote aging. Protein content in the food has recently emerged as critical factor in determining how food composition affects aging and health. The pulse-feeding assay, by measuring de novo protein synthesis, represents an ideal method to unequivocally establish how the composition of food dictates protein synthesis. In combination, these two assays provide new and powerful tools for C. elegans research to investigate feeding and how food intake affects the proteome and thus the physiology and health of an organism.

  12. Quantitative measurement of endogenous amino acid absorption in unanaesthetized pigs.

    PubMed

    Rerat, A; Vaissade, P; Vaugelade, P

    1988-06-01

    The present experiment was carried out with 11 pigs (mean body weight: 53.9 +/- 1.3 kg) fitted with permanent catheters in the portal vein and carotid artery and with an electromagnetic flow probe around the portal vein. They were each subjected to 2 or 3 trials at 3 to 4-day intervals. During each trial the animals received after a previous fasting of 20 h a given amount of a protein-free diet (200 to 1200 g). The blood was collected either continuously for a quantitative determination of amino nitrogen, reducing sugars, urea and ammonia (number of meals 12, mean intake: 727 +/- 60 g) or discontinuously every 30 min between 0 and 8 h after the meal for amino acid analysis (number of meals 8; mean intake 709 +/- 105 g). A rather constant appearance (2 g/h) of amino acids in the portal blood was observed throughout the postprandial period. The intestinal absorption of each amino acid was however variable and represented between 10 and 50% of the daily requirements of the animal during the measuring period (8 h). Glutamine and to a less extent glutamic acid were exceptions as they were taken up by the gut wall from the arterial blood. There was also a marked synthesis of ornithine and citrulline by the latter. Because of the low blood level of urea, there were no apparent exchanges of urea between the blood and the intestine; in contrast, the ammonia absorption represented about 70% of that observed after ingestion of normal protein diets. Most amino acids are largely taken up by the liver and peripheral tissues, but in the case of alanine the syntheses exceed the uptake.

  13. Decay Heat Measurements Using Total Absorption Gamma-ray Spectroscopy

    NASA Astrophysics Data System (ADS)

    Rice, S.; Valencia, E.; Algora, A.; Taín, J. L.; Regan, P. H.; Podolyák, Z.; Agramunt, J.; Gelletly, W.; Nichols, A. L.

    2012-09-01

    A knowledge of the decay heat emitted by thermal neutron-irradiated nuclear fuel is an important factor in ensuring safe reactor design and operation, spent fuel removal from the core, and subsequent storage prior to and after reprocessing, and waste disposal. Decay heat can be readily calculated from the nuclear decay properties of the fission products, actinides and their decay products as generated within the irradiated fuel. Much of the information comes from experiments performed with HPGe detectors, which often underestimate the beta feeding to states at high excitation energies. This inability to detect high-energy gamma emissions effectively results in the derivation of decay schemes that suffer from the pandemonium effect, although such a serious problem can be avoided through application of total absorption γ-ray spectroscopy (TAS). The beta decay of key radionuclei produced as a consequence of the neutron-induced fission of 235U and 239Pu are being re-assessed by means of this spectroscopic technique. A brief synopsis is given of the Valencia-Surrey (BaF2) TAS detector, and their method of operation, calibration and spectral analysis.

  14. Instrumentation for Combined Dispersion and Absorption Measurements in the VUV.

    PubMed

    Banfield, F P; Huber, M C; Parkinson, W H; Tubbs, E F

    1973-06-01

    When the hook method that measures anomalous dispersion is combined with photoelectric photometry, a particularly powerful tool results. An apparatus that combines these techniques over a wavelength range extending into the vacuum ultraviolet has been constructed and used chiefly on the iron-group elements. It consists of hydrogen-discharge light source, a Mach-Zehnder interferormeter, a high temperature furnace, a stigmatic spectrograph, and a photoelectric photometer.

  15. Mucosal Wave Measurement and Visualization Techniques

    PubMed Central

    Krausert, Christopher R.; Olszewski, Aleksandra E.; Taylor, Lindsay N.; McMurray, James S.; Dailey, Seth H.; Jiang, Jack J.

    2010-01-01

    Organized vibration of the vocal folds is critical to high quality voice production. When the vocal folds oscillate, the superficial tissue of the vocal fold is displaced in a wave-like fashion, creating the so called “mucosal wave”. Because the mucosal wave is dependent on vocal fold structure, physical alterations of that structure cause mucosal wave abnormalities. Visualization and quantification of mucosal wave properties have become useful parameters in diagnosing and managing vocal fold pathology. Mucosal wave measurement provides information about vocal fold characteristics that cannot be determined with other assessment techniques. Here, we discuss the benefits, disadvantages, and clinical applicability of the different mucosal wave measurement techniques, such as electroglottography (EGG), photoglottography (PGG), and ultrasound and visualization techniques that include videokymography (VKG), stroboscopy, and high-speed digital imaging (HSDI). The various techniques and their specific uses are reviewed with the intention of helping researchers and clinicians choose a method for a given situation and understand its limitations as well as its potential applications. Recent applications of these techniques for quantitative assessment demonstrate that additional research must be conducted to realize the full potential of these tools. Evaluations of existing research and recommendations for future research are given to promote both the quantitative study of the mucosal wave through accurate and standardized measurement of mucosal wave parameters and the development of reliable methods with which physicians can diagnose vocal disorders. PMID:20471798

  16. Spectrum sensing of trace C(2)H(2) detection in differential optical absorption spectroscopy technique.

    PubMed

    Chen, Xi; Dong, Xiaopeng

    2014-09-10

    An improved algorithm for trace C(2)H(2) detection is presented in this paper. The trace concentration is accurately calculated by focusing on the absorption spectrum from the frequency domain perspective. The advantage of the absorption spectroscopy frequency domain algorithm is its anti-interference capability. First, the influence of the background noise on the minimum detectable concentration is greatly reduced. Second, the time-consuming preprocess of spectra calibration in the differential optical absorption spectroscopy technique is skipped. Experimental results showed the detection limit of 50 ppm is achieved at a lightpath length of 0.2 m. This algorithm can be used in real-time spectrum analysis with high accuracy.

  17. Research relative to weather radar measurement techniques

    NASA Technical Reports Server (NTRS)

    Smith, Paul L.

    1992-01-01

    This grant provides for some investigations related to weather radar measurement techniques applicable to meteorological radar systems in Thailand. Quality data are needed from those systems to support TRMM and other scientific investigations. Activities carried out during a trip to the radar facilities at Phuket are described.

  18. Characterization of a laser-produced plasma using the technique of point-projection absorption spectroscopy

    SciTech Connect

    O'Neill, D.M.; Lewis, C.L.S.; Neely, D.; Davidson, S.J. ); Rose, S.J. ); Lee, R.W. )

    1991-08-15

    The technique of point-projection spectroscopy has been shown to be applicable to the study of expanding aluminum plasmas generated by {similar to}80 ps laser pulses incident on massive, aluminum stripe targets of {similar to}125 {mu}m width. Targets were irradiated at an intensity of 2.5{plus minus}0.5{times}10{sup 13} W/cm{sup 2} in a line focus geometry and under conditions similar to those of interest in x-ray laser schemes. Hydrogenic and heliumlike aluminum resonance lines were observed in absorption using a quasicontinuous uranium backlighter plasma. Using a pentaerythrital Bragg crystal as the dispersive element, a resolving power of {similar to}3500 was achieved with spatial resolution at the 5-{mu}m level in frame times of the order of 100 ps. Reduction of the data for times up to 150 ps after the peak of the incident laser pulse produced estimates of the temperature and ion densities present, as a function of space and time. The one-dimensional Lagrangian hydrodynamic code MEDUSA coupled to the atomic physics non-local-thermodynamic-equilibrium ionized material package was used to simulate the experiment in planar geometry and has been shown to be consistent with the measurements.

  19. Advanced IMCW Lidar Techniques for ASCENDS CO2 Column Measurements

    NASA Astrophysics Data System (ADS)

    Campbell, Joel; lin, bing; nehrir, amin; harrison, fenton; obland, michael

    2015-04-01

    Global atmospheric carbon dioxide (CO2) measurements for the NASA Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) space mission are critical for improving our understanding of global CO2 sources and sinks. Advanced Intensity-Modulated Continuous-Wave (IM-CW) lidar techniques are investigated as a means of facilitating CO2 measurements from space to meet the ASCENDS measurement requirements. In recent numerical, laboratory and flight experiments we have successfully used the Binary Phase Shift Keying (BPSK) modulation technique to uniquely discriminate surface lidar returns from intermediate aerosol and cloud contamination. We demonstrate the utility of BPSK to eliminate sidelobes in the range profile as a means of making Integrated Path Differential Absorption (IPDA) column CO2 measurements in the presence of optically thin clouds, thereby eliminating the need to correct for sidelobe bias errors caused by the clouds. Furthermore, high accuracy and precision ranging to the surface as well as to the top of intermediate cloud layers, which is a requirement for the inversion of column CO2 number density measurements to column CO2 mixing ratios, has been demonstrated using new hyperfine interpolation techniques that takes advantage of the periodicity of the modulation waveforms. This approach works well for both BPSK and linear swept-frequency modulation techniques. The BPSK technique under investigation has excellent auto-correlation properties while possessing a finite bandwidth. A comparison of BPSK and linear swept-frequency is also discussed in this paper. These results are extended to include Richardson-Lucy deconvolution techniques to extend the resolution of the lidar beyond that implied by limit of the bandwidth of the modulation.

  20. [In situ temperature measurement by absorption spectroscopy based on time division multiplexing technology].

    PubMed

    Lou, Nan-zheng; Li, Ning; Weng, Chun-sheng

    2012-05-01

    Tunable diode laser absorption spectroscopy (TDLAS) technology is a kind of high sensitivity, high selectivity of non contacting gas in situ measurement technique. In the present paper, in situ gas temperature measurement of an open environment was achieved by means of direct scanning multiple characteristic lines of H2O and combined with least-squares algorithm. Through the use of HITRAN spectral database, the boundary effect on the gas temperature and concentration measurements was discussed in detail, and results showed that the combination of scanning multiple characteristic lines and least-squares algorithm can effectively reduce the boundary effect on the gas temperature measurements under the open environment. Experiments using time division multiplexing technology to simultaneously scan 7444.36, 7185.60, 7182.95 and 7447.48 cm(-1), the four characteristic H2O lines, the gas temperature of tubular furnace in the range of 573-973 K was measured under different conditions. The maximum temperature difference between absorption spectrum measurement and thermocouple signal was less than 52.4 K, and the maximum relative error of temperature measurement was 6.8%.

  1. High accuracy radiation efficiency measurement techniques

    NASA Technical Reports Server (NTRS)

    Kozakoff, D. J.; Schuchardt, J. M.

    1981-01-01

    The relatively large antenna subarrays (tens of meters) to be used in the Solar Power Satellite, and the desire to accurately quantify antenna performance, dictate the requirement for specialized measurement techniques. The error contributors associated with both far-field and near-field antenna measurement concepts were quantified. As a result, instrumentation configurations with measurement accuracy potential were identified. In every case, advances in the state of the art of associated electronics were found to be required. Relative cost trade-offs between a candidate far-field elevated antenna range and near-field facility were also performed.

  2. Evanescent wave absorption measurements of corroded materials using ATR and optical fibers

    NASA Astrophysics Data System (ADS)

    Namkung, Juock; Hoke, Mike; Schwartz, Andy

    2011-06-01

    The purpose of this research effort is to develop an in-situ corrosion sensing capability. The technique will permit detection of corrosion on and within aircraft structures. This includes component junctions that are susceptible to corrosion but which are not accessible for visual inspection. The prototype experimental configuration we are developing includes long wave infrared transmitting optical fiber probes interfaced with a Fourier Transform Infrared (FTIR) interferometer for evanescent wave absorption spectroscopic measurements. The mature and fielded technique will allow periodic remote sensing for detection of corrosion and for general onboard aircraft structural health monitoring. An experimental setup using an Attenuated Total Reflection (ATR) crystal integrated with an FTIR spectrometer has been assembled. Naturally occurring corrosion including Aluminum Hydroxide [Al(OH)3] is one of the main corrosion products of aluminum the principle structural metal of aircraft. Absorption spectra of our model corrosion product, pure Al(OH)3, have been collected with this ATR/FTIR experimental setup. The Al(OH)3spectra serve as reference spectral signatures. The spectra of corrosion samples from a simulated corrosion process have been collected and compared with the reference Al(OH)3 spectra. Also absorption spectra of naturally occurring corrosion collected from a fielded corroded aircraft part have been obtained and compared with the spectra from the simulated corrosion.

  3. Unsteady measurement techniques for turbomachinery flows

    NASA Astrophysics Data System (ADS)

    Jaffa, Nicholas Andrew

    Accurate unsteady measurements are required for studying the flows in high speed turbomachines, which rely on the interaction between rotating and stationary components. Using statistics of phase locked ensembles simplifies the problem, but accurate frequency response in the 10-100 kHz range significantly limits the applicable techniques. This research advances the state of the art for phase resolved measurement techniques using for high speed turbomachinery flows focusing on the following areas: development, validation, and uncertainty quantification. Four methods were developed and implemented: an unsteady total pressure probe, the multiple overheat hot-wire method, the slanted hot-wire method, and the phase peak yaw hot-wire method. These methods allow for the entire phase locked average flow field to be measured (temperature, pressure, and velocity components, swirl angle, etc.). No trusted reference measurement or representative canonical flow exists for comparison of the phase resolved quantities, making validation challenging. Five different validation exercises were performed to increase the confidence and explore the range of applicability. These exercises relied on checking for consistency with expected flow features, comparing independent measurements, and cross validation with CFD. The combined uncertainties for the measurements were quantified using uncertainty estimates from investigations into the elemental error sources. The frequency response uncertainty of constant temperature hot-wire system was investigated using a novel method of illuminating the wire with a laser pulse. The uncertainty analysis provided estimates for the uncertainty in the measurements as well as showing the sensitivity to various sources of error.

  4. Ultrasonic techniques for aircraft ice accretion measurement

    NASA Technical Reports Server (NTRS)

    Hansman, R. John, Jr.; Kirby, Mark S.; Lichtenfelts, Fred

    1990-01-01

    Results of tests to measure ice growth in natural (flight) and artificial (icing wind tunnel) icing conditions are presented. Ice thickness is measured using an ultrasonic pulse-echo technique. Two icing regimes, wet and dry ice growth, are identified and the unique ultrasonic signal characteristics associated with these different types of ice growth are described. Ultrasonic measurements of ice growth on cylinders and airfoils exposed to artificial and natural icing conditions are presented. An accuracy of plus or minus 0.5 mm is achieved for ice thickness measurement using the pulse-echo technique. The performance of two-probe type ice detectors is compared to the surface mounted ultrasonic system. The ultrasonically measured ice accretion rates and ice surface condition (wet or dry) are used to compare the heat transfer characteristics for flight and icing wind tunnel environments. In general the heat transfer coefficient is inferred to be higher in the wind tunnel environment, not likely due to higher freestream turbulence levels. Finally, preliminary results of tests to measure ice growth on airfoil using an array of ultrasonic transducers are described. Ice profiles obtained during flight in natural icing conditions are shown and compared with mechanical and stereo image measurements.

  5. Measurements of Absorbing Aerosols Using in Situ and Remote Sensing Techniques

    NASA Astrophysics Data System (ADS)

    Martins, J. V.; Martins, J. V.; Kaufman, Y.; Artaxo, P.; Andrea, C.; Yamasoe, M.; Remer, L.

    2001-12-01

    Reliable measurements of light absorption by aerosol particles are essential for an accurate assessment of the climate radiative forcing by aerosol particles. Depending on the absorption properties, the radiative forcing of the aerosols may change from a cooling to a heating effect. New techniques for the remote sensing of aerosol absorption over land and ocean are developed and applied in combination with in situ measurements for validation and addition of complementary information. Spectral measurements show the effects of aerosols on absorption of light from the UV to the near infrared. Depending on particle size and structure, there is a significant absorption component that must be accounted for the radiative forcing in the near infrared. Remote sensing results from MODIS and from the CLAMS field experiment, as well as in situ validation data will be discussed.

  6. Financial volatility: Issues and measuring techniques

    NASA Astrophysics Data System (ADS)

    Daly, Kevin

    2008-04-01

    This paper explains in non-technical terms various techniques used to measure volatility ranging from time invariant measures to time variant measures. It is shown that a weakness of the former measures arises from the underlying assumption that volatility is considered to be constant over time. This observation has led researchers to develop time variant measures based on the assumption that volatility changes over time. The introduction of the original ARCH model by Engle has spawned an ever increasing variety of models such as GARCH, EGARCH, NARCH, ARCH-M MARCH and the Taylor-Schwert model. The degree of sophistication employed in developing these models is discussed in detail as are the models characteristics used to capture the underlying economic and financial time series data including volatility clustering, leverage effects and the persistence of volatility itself. A feature of these more elaborate models is that they generally obtain a better fit to the data in-sample.

  7. Pulsed thrust measurements using electromagnetic calibration techniques

    SciTech Connect

    Tang Haibin; Shi Chenbo; Zhang Xin'ai; Zhang Zun; Cheng Jiao

    2011-03-15

    A thrust stand for accurately measuring impulse bits, which ranged from 10-1000 {mu}N s using a noncontact electromagnetic calibration technique is described. In particular, a permanent magnet structure was designed to produce a uniform magnetic field, and a multiturn coil was made to produce a calibration force less than 10 mN. The electromagnetic calibration force for pulsed thrust measurements was linear to the coil current and changed less than 2.5% when the distance between the coil and magnet changed 6 mm. A pulsed plasma thruster was first tested on the thrust stand, and afterward five single impulse bits were measured to give a 310 {mu}N s average impulse bit. Uncertainty of the measured impulse bit was analyzed to evaluate the quality of the measurement and was found to be 10 {mu}N s with 95% credibility.

  8. Airborne intercomparison of nitric oxide measurement techniques

    NASA Technical Reports Server (NTRS)

    Hoell, James M., Jr.; Gregory, Gerald L.; Mcdougal, David S.; Torres, Arnold L.; Davis, Douglas D.

    1987-01-01

    Results from an airborne intercomparison of techniques to measure tropospheric levels of nitric oxide (NO) are discussed. The intercomparison was part of the National Aeronautics and Space Administration's Global Tropospheric Experiment and was conducted during missions flown in the fall of 1983 and spring of 1984. Instruments intercompared included a laser-induced fluorescence (LIF) system and two chemiluminescence instruments (CL). NO mixing ratios from below 5 pptv (parts per trillion by volume) to greater than 100 pptv were reported, with the majority less than 20 pptv. Good correlation was observed between the measurements reported by the CL and LIF techniques. The general level of agreement observed for the ensemble of measurements obtained during the two missions provides the basis from which one can conclude that equally 'valid' measurements of background levels of NO can be expected from either CL or LIF instruments. At the same time the periods of disagreement that were observed between the CL and LIF instruments as well as between the two CL instruments highlight the difficulty of obtaining reliable measurements with NO mixing ratios in the 5-20 pptv range and emphasize the vigilance that should be maintained in future NO measurements.

  9. An intercomparison of nitric oxide measurement techniques

    NASA Technical Reports Server (NTRS)

    Hoell, J. M., Jr.; Gregory, G. L.; Mcdougal, D. S.; Carroll, M. A.; Mcfarland, M.; Ridley, B. A.; Davis, D. D.; Bradshaw, J.; Rodgers, M. O.; Torres, A. L.

    1985-01-01

    Results from an intercomparison of techniques to measure tropospheric levels of nitric oxide (NO) are discussed. The intercomparison was part of the National Aeronautics and Space Administration's Global Tropospheric Experiment and was conducted at Wallops Island, VA, in July 1983. Instruments intercompared included a laser-induced fluorescence system and two chemiluminescence instruments. The intercomparisons were performed with ambient air at NO mixing ratios ranging from 10 to 60 pptv and NO-enriched ambient air at mixing ratios from 20 to 170 pptv. All instruments sampled from a common manifold. The techniques exhibited a high degree of correlation among themselves and with changes in the NO mixing ratio. Agreement among the three techniques was placed at approximately + or - 30 percent. Within this level of agreement, no artifacts or species interferences were identified.

  10. Measurement Techniques for Cellular Biomechanics In Vitro

    PubMed Central

    Addae-Mensah, Kweku A; Wikswo, John P

    2014-01-01

    Living cells and tissues experience mechanical forces in their physiological environments that are known to affect many cellular processes. Also of importance are the mechanical properties of cells, as well as the microforces generated by cellular processes themselves in their microenvironments. The difficulty associated with studying these phenomena in vivo has led to alternatives such as using in vitro models. The need for experimental techniques for investigating cellular biomechanics and mechanobiology in vitro has fueled an evolution in the technology used in these studies. Particularly noteworthy are some of the new biomicroelectromechanical systems (BioMEMs) devices and techniques that have been introduced to the field. We describe some of the cellular micromechanical techniques and methods that have been developed for in vitro studies, and provide summaries of the ranges of measured values of various biomechanical quantities. We also briefly address some of our experiences in using these methods and include modifications we have introduced in order to improve them. PMID:18445766

  11. Improved self-absorption correction for extended x-ray absorption fine-structure measurements

    SciTech Connect

    Booth, C.H.; Bridges, F.

    2003-06-04

    Extended x-ray absorption fine-structure (EXAFS) data collected in the fluorescence mode are susceptible to an apparent amplitude reduction due to the self-absorption of the fluorescing photon by the sample before it reaches a detector. Previous treatments have made the simplifying assumption that the effect of the EXAFS on the correction term is negligible, and that the samples are in the thick limit. We present a nearly exact treatment that can be applied for any sample thickness or concentration, and retains the EXAFS oscillations in the correction term.

  12. Techniques for measurement of thoracoabdominal asynchrony

    NASA Technical Reports Server (NTRS)

    Prisk, G. Kim; Hammer, J.; Newth, Christopher J L.

    2002-01-01

    Respiratory motion measured by respiratory inductance plethysmography often deviates from the sinusoidal pattern assumed in the traditional Lissajous figure (loop) analysis used to determine thoraco-abdominal asynchrony, or phase angle phi. We investigated six different time-domain methods of measuring phi, using simulated data with sinusoidal and triangular waveforms, phase shifts of 0-135 degrees, and 10% noise. The techniques were then used on data from 11 lightly anesthetized rhesus monkeys (Macaca mulatta; 7.6 +/- 0.8 kg; 5.7 +/- 0.5 years old), instrumented with a respiratory inductive plethysmograph, and subjected to increasing levels of inspiratory resistive loading ranging from 5-1,000 cmH(2)O. L(-1). sec(-1).The best results were obtained from cross-correlation and maximum linear correlation, with errors less than approximately 5 degrees from the actual phase angle in the simulated data. The worst performance was produced by the loop analysis, which in some cases was in error by more than 30 degrees. Compared to correlation, other analysis techniques performed at an intermediate level. Maximum linear correlation and cross-correlation produced similar results on the data collected from monkeys (SD of the difference, 4.1 degrees ) but all other techniques had a high SD of the difference compared to the correlation techniques.We conclude that phase angles are best measured using cross-correlation or maximum linear correlation, techniques that are independent of waveform shape, and robust in the presence of noise. Copyright 2002 Wiley-Liss, Inc.

  13. Phase Retrieval Techniques In Coordinates Measurement

    SciTech Connect

    Harizanova, J. I.; Stoykova, E. V.; Sainov, V. C.

    2007-04-23

    A precise pattern projection profilometry for three-dimensional shape measurements with different methods of fringe generation is presented. The application of phase-shifting algorithm along with two-spacing illumination allow for phase retrieval and estimation of relative and absolute coordinates of the tested samples. The following experimental approaches for fringe generation are investigated: interferometric approach based on a classical Michelson interferometer, digital computation with a DMD projection and light modulation by a sinusoidal phase grating. The theoretical background, experimental results as well as comparison of the applied generation methods are analyzed. The obtained outcomes successfully display the applicability of this technique for surface profile measurement. The application of the proposed techniques for remote, non-destructive in-situ inspection of real objects from cultural heritage is discussed.

  14. Surface Wear Measurement Using Optical Correlation Technique

    NASA Astrophysics Data System (ADS)

    Acinger, Kresimir

    1983-12-01

    The coherent optical correlation technique was applied for measuring the surface wear of a tappet (part of car engine), worn by friction with the camshaft. It was found that maximum correlation intensity decays exponentially with the number of wear cycles (i.e. camshaft revolutions). Tappets of the same make have an identical rate of correlation decay. Tappets of different makes have different rates of correlation decay which are in agreement with observed long term wear.

  15. Investigation of a noncontact strain measurement technique

    SciTech Connect

    Damiano, B.; Talarico, L.J.

    1996-05-01

    The goal of this project was to investigate the feasibility of a new noncontact technique for directly and continuously monitoring peak strain in rotating components. The technique utilizes the unique strain-sensitive magnetic material properties of transformation Induced Plasticity (TRIP) steel alloys to measure strain. These alloys are weakly magnetic when unstrained but become strongly ferromagnetic after mechanical deformation. A computer study was performed to determine whether the strain-induced change in the magnetic material properties of a TRIP steel gage bonded to a rotating component would cause significant perturbations in the magnetic flux of a stationary electromagnet. The effects of strain level, distance between the rotating component and the stationary electromagnet, and motion-induced eddy currents on flux perturbation magnitude were investigated. The calculated results indicate that a TRIP steel strain sensing element can cause a significant perturbation in the magnetic flux of a stationary electromagnet. The magnetic flux perturbation magnitude was found to be inversely proportional to the distance between the magnet face and the TRIP steel element and directly proportional to the TRIP steel strain level. The effect of motion-induced eddy currents on the magnetic flux was found to be negligible. It appears that the technique can be successfully applied to measure peak strain in rotating components; however, the sensitivity of the magnetic flux perturbation magnitude to the distance between the strain sensing element and the electromagnet may require making an independent proximity measurement.

  16. In situ Gas Temperature Measurements by UV-Absorption Spectroscopy

    NASA Astrophysics Data System (ADS)

    Fateev, A.; Clausen, S.

    2009-02-01

    The absorption spectrum of the NO A2Σ+ ← X2Πγ-system can be used for in situ evaluation of gas temperature. Experiments were performed with a newly developed atmospheric-pressure high-temperature flow gas cell at highly uniform and stable gas temperatures over a 0.533 m path in the range from 23 °C to 1,500 °C. The gas temperature was evaluated (1) from the analysis of the structure of selected NO high-resolution γ-absorption bands and (2) from the analysis of vibrational distribution in the NO γ-absorption system in the (211-238) nm spectral range. The accuracy of both methods is discussed. Validation of the classical Lambert-Beer law has been demonstrated at NO concentrations up to 500 ppm and gas temperatures up to 1,500 °C over an optical absorption path length of 0.533 m.

  17. Recent Pulsed Airborne Lidar measurements of Atmospheric CO2 Column Absorption to 13 km altitudes

    NASA Astrophysics Data System (ADS)

    Abshire, J. B.; Riris, H.; Allan, G. R.; Weaver, C. J.; Mao, J.; Hasselbrack, W.; Sun, X.; Rodriguez, M. R.

    2010-12-01

    We have developed a lidar technique for measuring atmospheric CO2 concentrations as a candidate for NASA’s ASCENDS mission. It uses pulsed laser transmitters to simultaneously measure a CO2 absorption line in the 1570 nm band, O2 extinction in the Oxygen A-band and surface height and backscatter. The lidar measures the energy and time of flight of the laser echoes reflected from the atmosphere and surface. The lasers step in wavelength across the CO2 line and an O2 line pair during the measurement. The receiver uses a telescope and photon counting detectors, and measures the time resolved backscatter of the laser echoes. Signal processing is used to isolate the laser echo signals from the surface, estimate their range, and reject laser photons scattered in the atmosphere. The gas extinction and column densities for the CO2 and O2 gases are estimated via the IPDA technique. We developed a lidar to demonstrate the CO2 measurement from aricraft. The lidar steps the pulsed laser’s wavelength across a selected CO2 line with 20 or 30 steps per scan. The line scan rate is 450 Hz and laser pulse widths are 1 usec. The time resolved laser backscatter is collected by a 20 cm telescope, detected by a photomultiplier and is recorded by a photon counting system. During July and August 2009 we made 5 two hour long flights while installed on the NASA Glenn Lear-25 aircraft. We measured the atmospheric CO2 absorption and line shapes using the 1572.33 nm CO2 line. Measurements were made at stepped altitudes from 3-13 km over a variety of surfaces in Nebraska, Illinois, the SGP ARM site, and near and over the Chesapeake Bay. Strong laser signals and clear line shapes were observed at all altitudes, and some measurements were made through thin clouds. The Oklahoma and east coast flights were coordinated with the NASA LaRC/ITT CO2 lidar on their UC-12 aircraft, a LaRC in-situ CO2 sensor, and the Oklahoma flights also included a JPL CO2 lidar on a Twin Otter aircraft. Ed Browell

  18. Advanced Sine Wave Modulation of Continuous Wave Laser System for Atmospheric CO2 Differential Absorption Measurements

    NASA Technical Reports Server (NTRS)

    Campbell, Joel F.; Lin, Bing; Nehrir, Amin R.

    2014-01-01

    NASA Langley Research Center in collaboration with ITT Exelis have been experimenting with Continuous Wave (CW) laser absorption spectrometer (LAS) as a means of performing atmospheric CO2 column measurements from space to support the Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) mission.Because range resolving Intensity Modulated (IM) CW lidar techniques presented here rely on matched filter correlations, autocorrelation properties without side lobes or other artifacts are highly desirable since the autocorrelation function is critical for the measurements of lidar return powers, laser path lengths, and CO2 column amounts. In this paper modulation techniques are investigated that improve autocorrelation properties. The modulation techniques investigated in this paper include sine waves modulated by maximum length (ML) sequences in various hardware configurations. A CW lidar system using sine waves modulated by ML pseudo random noise codes is described, which uses a time shifting approach to separate channels and make multiple, simultaneous online/offline differential absorption measurements. Unlike the pure ML sequence, this technique is useful in hardware that is band pass filtered as the IM sine wave carrier shifts the main power band. Both amplitude and Phase Shift Keying (PSK) modulated IM carriers are investigated that exibit perfect autocorrelation properties down to one cycle per code bit. In addition, a method is presented to bandwidth limit the ML sequence based on a Gaussian filter implemented in terms of Jacobi theta functions that does not seriously degrade the resolution or introduce side lobes as a means of reducing aliasing and IM carrier bandwidth.

  19. Total ozone and aerosol optical depths inferred from radiometric measurements in the Chappuis absorption band

    SciTech Connect

    Flittner, D.E.; Herman, B.M.; Thome, K.J.; Simpson, J.M.; Reagan, J.A. )

    1993-04-15

    A second-derivative smoothing technique, commonly used in inversion work, is applied to the problem of inferring total columnar ozone amounts and aerosol optical depths. The application is unique in that the unknowns (i.e., total columnar ozone and aerosol optical depth) may be solved for directly without employing standard inversion methods. It is shown, however, that by employing inversion constraints, better solutions are normally obtained. The current method requires radiometric measurements of total optical depth through the Chappuis ozone band. It assumes no a priori shape for the aerosol optical depth versus wavelength profile and makes no assumptions about the ozone amount. Thus, the method is quite versatile and able to deal with varying total ozone and various aerosol size distributions. The technique is applied first in simulation, then to 119 days of measurements taken in Tucson, Arizona, that are compared to TOMS values for the same dates. The technique is also applied to two measurements taken at Mauna Loa, Hawaii, for which Dobson ozone values are available in addition to the TOMS values, and the results agree to within 15%. It is also shown through simulations that additional information can be obtained from measurements outside the Chappuis band. This approach reduces the bias and spread of the estimates total ozone and is unique in that it uses measurements from both the Chappuis and Huggins absorption bands. 12 refs., 6 figs., 2 tabs.

  20. A DGT technique for plutonium bioavailability measurements.

    PubMed

    Cusnir, Ruslan; Steinmann, Philipp; Bochud, François; Froidevaux, Pascal

    2014-09-16

    The toxicity of heavy metals in natural waters is strongly dependent on the local chemical environment. Assessing the bioavailability of radionuclides predicts the toxic effects to aquatic biota. The technique of diffusive gradients in thin films (DGT) is largely exploited for bioavailability measurements of trace metals in waters. However, it has not been applied for plutonium speciation measurements yet. This study investigates the use of DGT technique for plutonium bioavailability measurements in chemically different environments. We used a diffusion cell to determine the diffusion coefficients (D) of plutonium in polyacrylamide (PAM) gel and found D in the range of 2.06-2.29 × 10(-6) cm(2) s(-1). It ranged between 1.10 and 2.03 × 10(-6) cm(2) s(-1) in the presence of fulvic acid and in natural waters with low DOM. In the presence of 20 ppm of humic acid of an organic-rich soil, plutonium diffusion was hindered by a factor of 5, with a diffusion coefficient of 0.50 × 10(-6) cm(2) s(-1). We also tested commercially available DGT devices with Chelex resin for plutonium bioavailability measurements in laboratory conditions and the diffusion coefficients agreed with those from the diffusion cell experiments. These findings show that the DGT methodology can be used to investigate the bioaccumulation of the labile plutonium fraction in aquatic biota.

  1. A new kind of gear measurement technique

    NASA Astrophysics Data System (ADS)

    Zhaolong, Zhang; Tongnian, Huang; Shanglian, Huang; Deyuan, Kang; Hong, Wang; Rongan, Duan; Lu, Xu

    1997-07-01

    A new method of gear measurement is introduced in this paper. It is based on the traditional gear single-flank measurement, but it uses a special master gear with three kinds of measuring tooth and a tranmission tooth. The first kind of measurement tooth has a projective involute which is used as a reference. When it is engaged in mesh with the tooth of the workpiece, the deviation of transmission reflects the involute profile error of the workpiece. When a projective helix on the second kind of measurement tooth is meshed with the tooth of the workpiece the lead error can be obtained. Because the third kind of measurement tooth is the same as that used by a traditional single-flank tester, the tangential composite error can be easily obtained. The transmission tooth - whose thickness is reduced - is used to make the contact ratio less than one. When the new master gear is meshed with the workpiece for several turns the pitch error of the latter can be measured. Experimental results using equipment based on the new technique have shown that the method is feasible and efficient.

  2. Vitamin A equivalency and apparent absorption of beta-carotene in ileostomy subjects using a dual-isotope dilution technique.

    PubMed

    Van Loo-Bouwman, Carolien A; Naber, Ton H J; van Breemen, Richard B; Zhu, Dongwei; Dicke, Heleen; Siebelink, Els; Hulshof, Paul J M; Russel, Frans G M; Schaafsma, Gertjan; West, Clive E

    2010-06-01

    The objective was to quantify the vitamin A equivalency of beta-carotene in two diets using a dual-isotope dilution technique and the apparent beta-carotene absorption as measured by the oral-faecal balance technique. Seventeen healthy adults with an ileostomy completed the 4-week diet-controlled, cross-over intervention study. Each subject followed both diets for 2 weeks: a diet containing vegetables low in beta-carotene content with supplemental beta-carotene in salad dressing oil ('oil diet'; mean beta-carotene intake 3.1 mg/d) and a diet containing vegetables and fruits high in beta-carotene content ('mixed diet'; mean beta-carotene intake 7.6 mg/d). Daily each subject consumed a mean of 190 microg [13C10]beta-carotene and 195 microg [13C10]retinyl palmitate in oil capsules. The vitamin A equivalency of beta-carotene was calculated as the dose-corrected ratio of [13C5]retinol to [13C10]retinol in serum. Apparent absorption of beta-carotene was determined with oral-faecal balance. Isotopic data quantified a vitamin A equivalency of [13C10]beta-carotene in oil of 3.6:1 (95 % CI 2.8, 4.6) regardless of dietary matrices differences. The apparent absorption of (labelled and dietary) beta-carotene from the 'oil diet' (30 %) was 1.9-fold higher than from the 'mixed diet' (16 %). This extrinsic labelling technique can measure precisely the vitamin A equivalency of beta-carotene in oil capsules, but it does not represent the effect of different dietary matrices.

  3. Optical techniques for measurement of high temperatures

    SciTech Connect

    Veligdan, J.T.

    1991-10-25

    The availability of instrumentation to measure the high outlet gas temperature of a particle bed reactor is a topic of some concern. There are a number of possible techniques with advantages and disadvantages. In order to provide some baseline choice of instrumentation, a review has been conducted of these various technologies. This report summarizes the results of this review for a group of technologies loosely defined as optical techniques (excluding optical pyrometry). The review has concentrated on a number of questions for each technology investigated. These are: (1) Description of the technology, (2) Anticipated sensitivity and accuracy, (3) Requirements for implementation, (4) Necessary development time and costs, (5) Advantages and disadvantages of the technology. Each of these areas was considered for a technology and a large number of technologies were considered in a review of the literature. Based upon this review it was found that a large number of methods exist to measure temperatures in excess of 2000 K. None of the methods found were ideal. Four methods, however, appeared to warrant further consideration: opto-mechanical expansion thermometry, surface Raman spectroscopy, gas-phase Raman spectroscopy and coherent anti-Stokes Raman spectroscopy (CARS). These techniques will be discussed further in this document.

  4. [Clinical use of pain measurement techniques].

    PubMed

    Arendt-Nielsen, Lars

    2002-03-25

    The increased knowledge about pain has lead to the suggestion of a mechanism-based classification of pain, and hence mechanism-based therapy. The implementation of this classification is unlikely to occur in the near future, but the concept as such emphasises the importance of a better understanding of the origin of pain before treatment is initiated. The basis for developing and applying such an approach in the future is accessibility to pain assessment techniques, which are able to measure and quantify patients' responses to pain. Experimental clinical research includes a number of techniques to assess the excitability of the pain system and the manifestations related to central sensitisation and neuroplasticity. This can now be applied for mechanism-based diagnosis and related targeted treatment. As the new generation analgesics with new sites of action are developed, a mechanisms-based approach could, it is hoped, lead to more rational management of pain in the future.

  5. Thermoluminescence measurement technique using millisecond temperature pulses.

    PubMed

    Manfred, Michael E; Gabriel, Nicholas T; Yukihara, Eduardo G; Talghader, Joseph J

    2010-06-01

    A measurement technique, pulsed thermoluminescence, is described which uses short thermal pulses to excite trapped carriers leading to radiative recombination. The pulses are obtained using microstructures with approximately 500 micros thermal time constants. The technique has many of the advantages of pulsed optically stimulated luminescence without the need for optical sources and filters to isolate the luminescent signal. Charge carrier traps in alpha-Al(2)O(3):C particles on microheaters were filled using 205 nm light. Temperature pulses of 10 and 50 ms were applied to the heaters and compared with a standard thermoluminescence curve taken at a ramp rate of 5 K s(-1). This produced curves of intensity verses temperature similar to standard thermoluminescence except shifted to higher temperatures. The luminescence of single particles was read multiple times with negligible loss of population. The lower limit of the duration of useful pulses appears to be limited by particle size and thermal contact between the particle and heater.

  6. Infrared radiometric technique in temperature measurement

    NASA Technical Reports Server (NTRS)

    Glazer, S.; Madding, R.

    1988-01-01

    One class of commercially available imaging infrared radiometers using cooled detectors is sensitive to radiation over the 3 to 12 micron wavelength band. Spectral filters can tailor instrument sensitivity to specific regions where the target exhibits optimum radiance. The broadband spectral response coupled with real time two-dimensional imaging and emittance/background temperature corrections make the instruments useful for remote measurement of surface temperatures from -20 C to +1500 C. Commonly used radiometric techniques and assumptions are discussed, and performance specifications for a typical modern commercial instrument are presented. The potential usefulness of an imaging infrared radiometer in space laboratories is highlighted through examples of research, nondestructive evaluation, safety, and routine maintenance applications. Future improvements in instrument design and application of the radiometric technique are discussed.

  7. Measurement of urinary mercury excretion by atomic absorption in health and disease

    PubMed Central

    Taylor, Andrew; Marks, Vincent

    1973-01-01

    Taylor, A., and Marks, V. (1973).British Journal of Industrial Medicine,30, 293-296. Measurement of urinary excretion by atomic absorption in health and disease. Excretion of mercury was measured by a cold-vapour atomic absorption technique on samples of urine from five groups of people having varying exposure to mercury. Serial investigations of up to 14 days were carried out on eight subjects to determine the temporal relationship between exposure and excretion. Subjects with no exposure excreted 0-10 μg mercury per gramme creatinine. Similar values were found in laboratory staff and men assembling hollow cathode lamps. Excretion of mercury by dental workers was significantly increased. No correlation between exposure and excretion of mercury was seen in the subjects investigated. The significance of measuring urinary excretion in the detection of mercury intoxication is discussed. The suggestion is made that urinary mercury excretion of more than 20 μg/g creatinine or 40 μg mercury per 24 hours should be considered evidence of recent or remote exposure to mercury. It is concluded that measurement of urinary mercury excretion is important in revealing those persons who may ultimately develop symptoms of toxicity. PMID:4723792

  8. Flight Acoustics Measurement Techniques and Applications

    NASA Technical Reports Server (NTRS)

    Preisser, J. S.; Marcolini, M. A.

    1998-01-01

    Careful consideration must be given to data acquisition and analysis techniques in the design of experiments for the measurement of noise generated by flight vehicles. Although noise measurement locations and data reduction procedures are specified for aircraft certification by FAA and ICAO directives, for example, there are virtually no established procedures for aircraft noise measurement for other purposes. To optimize the quality and quantity of information obtained in a flight acoustics experiment, microphone layout, data acquisition, and analysis must be tailored to the specific test objective. This paper will review flight acoustics technology at NASA Langley Research Center developed over the past decade. In particular, the paper will focus on flight experiments performed for three diverse objectives: (1) research applications, such as noise prediction code validation, (2) noise impact modeling, and (3) noise abatement flight procedures. To best achieve these diverse objectives, different deployments of microphone systems on the ground are required, and different data analysis techniques are needed. In all cases, accurate positioning of the aircraft synchronized in time with the data recording is necessary. However, there are some restrictions on flight operations unique to each case for the methods to properly work.

  9. THE EFFECT OF 3HE ON LOW PRESSURE HYDRIDE ABSORPTION MEASUREMENTS WITH TRITIUM

    SciTech Connect

    Staack, G.; Klein, J.

    2011-01-20

    Absorption isotherm data exists for a wide variety of hydrogen-metal systems. When working with high purity gases, appropriately sized equipment, and hydrides with equilibrium pressures above several hundred Pa, data collection is relatively straightforward. Special consideration must be given to experiments involving low equilibrium pressure hydrides, as even sub-ppm levels of gas impurities can generate partial pressures many times greater than the equilibrium pressures to be measured. Tritium absorption experiments are further complicated by the continuous generation of helium-3. The time required to transfer and absorb a known quantity of tritium onto a sample ultimately limits the minimum pressure range that can be studied using the standard technique. Equations are presented which show the pressure of helium-3 in a sample cell based on the amount of tritium to be absorbed, the sample cell volume and temperature, and the decay time of tritium. Sample calculations for zirconium show that at 300 C, the estimated helium-3 pressure in the cell will be equal to the hydrogen absorption pressure after only milliseconds of tritium decay. An alternate method is presented that permits the collection of equilibrium data at pressures orders of magnitude lower than possible using a direct approach.

  10. International Congress on Acoustic Intensity Measurement: Measurement Techniques and Applications, 2nd, Senlis, France, September 23-26, 1985, Proceedings

    NASA Astrophysics Data System (ADS)

    Recent developments in acoustic-intensity measurement are discussed in reviews and reports of theoretical and experimental investigations. Instrumentation, vector acoustics, sound radiation, intensity in the presence of flow, intensity in structures, sound power, source localization, impedance, absorption, and transmission are the fields covered by the contributions. Specific topics addressed include microphone configurations for intensity probes, the rotational structure of intensity fields, acoustic intensity and numerical simulation, sound-power measurement in the presence of background noise, and techniques for measuring the absorption coefficient of acoustic materials. Graphs, drawings, diagrams, tables of numerical data, and photographs of test setups are provided.

  11. Measurements of the Absorption by Auditorium SEATING—A Model Study

    NASA Astrophysics Data System (ADS)

    BARRON, M.; COLEMAN, S.

    2001-01-01

    One of several problems with seat absorption is that only small numbers of seats can be tested in standard reverberation chambers. One method proposed for reverberation chamber measurements involves extrapolation when the absorption coefficient results are applied to actual auditoria. Model seat measurements in an effectively large model reverberation chamber have allowed the validity of this extrapolation to be checked. The alternative barrier method for reverberation chamber measurements was also tested and the two methods were compared. The effect on the absorption of row-row spacing as well as absorption by small numbers of seating rows was also investigated with model seats.

  12. Iris as a reflector for differential absorption low-coherence interferometry to measure glucose level in the anterior chamber

    NASA Astrophysics Data System (ADS)

    Zhou, Yong; Zeng, Nan; Ji, Yanhong; Li, Yao; Dai, Xiangsong; Li, Peng; Duan, Lian; Ma, Hui; He, Yonghong

    2011-01-01

    We present a method of glucose concentration detection in the anterior chamber with a differential absorption optical low-coherent interferometry (LCI) technique. Back-reflected light from the iris, passing through the anterior chamber twice, was selectively obtained with the LCI technique. Two light sources, one centered within (1625 nm) and the other centered outside (1310 nm) of a glucose absorption band were used for differential absorption measurement. In the eye model and pig eye experiments, we obtained a resolution glucose level of 26.8 mg/dL and 69.6 mg/dL, respectively. This method has a potential application for noninvasive detection of glucose concentration in aqueous humor, which is related to the glucose concentration in blood.

  13. On the errors in measuring the particle density by the light absorption method

    SciTech Connect

    Ochkin, V. N.

    2015-04-15

    The accuracy of absorption measurements of the density of particles in a given quantum state as a function of the light absorption coefficient is analyzed. Errors caused by the finite accuracy in measuring the intensity of the light passing through a medium in the presence of different types of noise in the recorded signal are considered. Optimal values of the absorption coefficient and the factors capable of multiplying errors when deviating from these values are determined.

  14. Viscosity measurement techniques in Dissipative Particle Dynamics

    NASA Astrophysics Data System (ADS)

    Boromand, Arman; Jamali, Safa; Maia, Joao M.

    2015-11-01

    In this study two main groups of viscosity measurement techniques are used to measure the viscosity of a simple fluid using Dissipative Particle Dynamics, DPD. In the first method, a microscopic definition of the pressure tensor is used in equilibrium and out of equilibrium to measure the zero-shear viscosity and shear viscosity, respectively. In the second method, a periodic Poiseuille flow and start-up transient shear flow is used and the shear viscosity is obtained from the velocity profiles by a numerical fitting procedure. Using the standard Lees-Edward boundary condition for DPD will result in incorrect velocity profiles at high values of the dissipative parameter. Although this issue was partially addressed in Chatterjee (2007), in this work we present further modifications (Lagrangian approach) to the original LE boundary condition (Eulerian approach) that will fix the deviation from the desired shear rate at high values of the dissipative parameter and decrease the noise to signal ratios in stress measurement while increases the accessible low shear rate window. Also, the thermostat effect of the dissipative and random forces is coupled to the dynamic response of the system and affects the transport properties like the viscosity and diffusion coefficient. We investigated thoroughly the dependency of viscosity measured by both Eulerian and Lagrangian methodologies, as well as numerical fitting procedures and found that all the methods are in quantitative agreement.

  15. Inference of the microwave absorption coefficient from stray radiation measurements in Wendelstein 7-X

    NASA Astrophysics Data System (ADS)

    Moseev, D.; Laqua, H. P.; Marsen, S.; Marushchenko, N.; Stange, T.; Braune, H.; Gellert, F.; Hirsch, M.; Hoefel, U.; Knauer, J.; Oosterbeek, J. W.; Turkin, Y.; The Wendelstein 7-X Team

    2017-03-01

    The efficiency of electron cyclotron heating is determined by the microwave absorption of the plasma. Good microwave absorption is also crucial for the machine safety. In this paper we present a method of evaluating the microwave absorption coefficient from stray radiation measurements. The discussed method is computationally simple and can be applied potentially in real time. Evolution of the second harmonic extraordinary mode (X2) microwave absorption coefficient in Wendelstein 7-X during the start-up phase is presented, as well as an estimate of the absorption coefficient for the second harmonic ordinary mode (O2) wave.

  16. A new technique for measuring ionospheric temperature

    NASA Astrophysics Data System (ADS)

    Archer, William Edward

    The lower ionosphere is a region of immense electrical energy inflow from space, yet to date there are no direct (in-situ) measurements of the consequent Joule (frictional) heating, partly because of the lack of appropriate instrumentation. This thesis presents a new technique for measuring ion temperature from a sub-orbital sounding rocket using a new type of ion detector, the suprathermal ion imager (SII). Simulations of the SII instrument show that 2-dimensional count-rate distributions binned according to detector azimuth are sensitive to the ratio of ram speed to thermal speed, or Mach number. Analysis of data from the JOULE-II rocket mission show a significant increase in thermal speed at the peak of the Joule heating region as expected, and even higher but unexplained temperatures at lower altitudes.

  17. Techniques for Measuring Surface Potentials in Space

    NASA Technical Reports Server (NTRS)

    Minow, Joseph I.; Parker, Linda Neergaard

    2015-01-01

    Materials exposed to the space plasma environment charge to a net potential relative to the ambient plasma. The charging process is due to differential currents to the material surface that results in a net surface charge density. While this process is termed "spacecraft surface charging" when applied to aerospace hardware, it also applies to the surfaces of astronomical objects in direct contact with the space plasma environment including a number of planetary bodies, asteroids, and dust particles. The ability to measure surface potentials is important to many techniques used in conducting fundamental heliospheric science, spacecraft engineering operations, and space technology development activities. This presentation provides a survey of current technologies used to measure surface potentials of spacecraft and planetary bodies with examples of their application to space science and technology programs.

  18. Measurement of Physicians' Performance Using Existing Techniques

    PubMed Central

    Sanazaro, Paul J.

    1980-01-01

    Existing techniques permit objective and valid measurement of limited elements of physicians' performance. These limited aspects, however, are of considerable importance to patients. The basic components of performance in medicine and surgery can be defined and used as the basis of organized programs for such evaluation. Interhospital comparisons can provide an effective impetus for assessing and improving performance of individual staff members when this is indicated. Professional auspices are needed for the development and application of methods that can provide continuing assurance that the clinical activity of physicians corresponds to contemporary standards. A system of incentives should be provided to physicians to promote their participation in voluntary programs of self-assessment. The incentives should be in the form of performance assessment credits, comparable in definition to continuing medical education credits, but granted for participation in an accredited program that objectively measures physicians' performance against national standards of the respective specialty. PMID:7222656

  19. Acoustic Absorption Measurements for Characterization of Gas Mixing

    DTIC Science & Technology

    2007-11-02

    of the box (Gas A). Gas B is humidified by passing the same grade CO2 through a bubbler. The humidity of the gas is varied by mixing the relative...the accuracy with which the “mixedness profile” can be inverted. 1Bhatia, A., Ultrasonic Absorption, Dover Publications: New York, 1967. 2

  20. Measuring techniques in induced polarisation imaging

    NASA Astrophysics Data System (ADS)

    Dahlin, Torleif; Leroux, Virginie; Nissen, Johan

    2002-06-01

    Multi-electrode geoelectrical imaging has become very popular and is used for many different purposes. For some of these, the inclusion of IP data would be desirable as it would allow the interpreter to distinguish between, e.g. sand formations with saltwater infiltration and clay formations or help delineate landfills. However, present-day IP measuring techniques require the use of nonpolarisable potential electrodes and special wire layout and are thus cumbersome and expensive. In this paper, we suggest making IP measurements with multi-electrode cables and just one set of steel electrodes. The polarisation potentials on the potential electrodes are corrected for by subtracting the polarisation potential measured when no primary current and no IP signal are present. Test measurements indicate that the polarisation potentials vary slowly and that the correction procedure is feasible. At two sites in southern Sweden, we have compared measurements with only stainless steel electrodes and measurements with both stainless steel and Pb-PbCl nonpolarisable electrodes using one or two sets of multicore cables, respectively. Almost no difference between the two data sets was observed. At one site, the charge-up effect on the potential electrodes was not important, while at the other site, the correction procedure was crucial. Though only two sites have been studied so far, it seems that time-domain IP imaging measurements can be taken with only steel electrodes and ordinary multicore cables. Coupling in the multicore cables has not presented any problems at the investigated sites where grounding resistances were moderate, making the coupling effect small. High grounding resistance sites have not yet been investigated.

  1. Differential absorption lidar measurements of atmospheric water vapor using a pseudonoise code modulated AlGaAs laser. Thesis

    NASA Technical Reports Server (NTRS)

    Rall, Jonathan A. R.

    1994-01-01

    Lidar measurements using pseudonoise code modulated AlGaAs lasers are reported. Horizontal path lidar measurements were made at night to terrestrial targets at ranges of 5 and 13 km with 35 mW of average power and integration times of one second. Cloud and aerosol lidar measurements were made to thin cirrus clouds at 13 km altitude with Rayleigh (molecular) backscatter evident up to 9 km. Average transmitter power was 35 mW and measurement integration time was 20 minutes. An AlGaAs laser was used to characterize spectral properties of water vapor absorption lines at 811.617, 816.024, and 815.769 nm in a multipass absorption cell using derivative spectroscopy techniques. Frequency locking of an AlGaAs laser to a water vapor absorption line was achieved with a laser center frequency stability measured to better than one-fifth of the water vapor Doppler linewidth over several minutes. Differential absorption lidar measurements of atmospheric water vapor were made in both integrated path and range-resolved modes using an externally modulated AlGaAs laser. Mean water vapor number density was estimated from both integrated path and range-resolved DIAL measurements and agreed with measured humidity values to within 6.5 percent and 20 percent, respectively. Error sources were identified and their effects on estimates of water vapor number density calculated.

  2. Uncertainty analysis technique for OMEGA Dante measurements.

    PubMed

    May, M J; Widmann, K; Sorce, C; Park, H-S; Schneider, M

    2010-10-01

    The Dante is an 18 channel x-ray filtered diode array which records the spectrally and temporally resolved radiation flux from various targets (e.g., hohlraums, etc.) at x-ray energies between 50 eV and 10 keV. It is a main diagnostic installed on the OMEGA laser facility at the Laboratory for Laser Energetics, University of Rochester. The absolute flux is determined from the photometric calibration of the x-ray diodes, filters and mirrors, and an unfold algorithm. Understanding the errors on this absolute measurement is critical for understanding hohlraum energetic physics. We present a new method for quantifying the uncertainties on the determined flux using a Monte Carlo parameter variation technique. This technique combines the uncertainties in both the unfold algorithm and the error from the absolute calibration of each channel into a one sigma Gaussian error function. One thousand test voltage sets are created using these error functions and processed by the unfold algorithm to produce individual spectra and fluxes. Statistical methods are applied to the resultant set of fluxes to estimate error bars on the measurements.

  3. Measurement technique developments for LBE flows

    NASA Astrophysics Data System (ADS)

    Buchenau, D.; Eckert, S.; Gerbeth, G.; Stieglitz, R.; Dierckx, M.

    2011-08-01

    We report on the development of measurement techniques for flows in lead-bismuth eutectic alloys (LBE). This paper covers the test results of newly developed contactless flow rate sensors as well as the development and test of the LIDAR technique for operational free surface level detection. The flow rate sensors are based on the flow-induced disturbance of an externally applied AC magnetic field which manifests itself by a modified amplitude or a modified phase of the AC field. Another concept of a force-free contactless flow meter uses a single cylindrical permanent magnet. The electromagnetic torque on the magnet caused by the liquid metal flow sets the magnet into rotation. The operation of those sensors has been demonstrated at liquid metal test loops for which comparative flow rate measurements are available, as well as at the LBE loops THESYS at KIT and WEBEXPIR at SCK-CEN. For the level detection a commercial LIDAR system was successfully tested at the WEBEXPIR facility in Mol and the THEADES loop in Karlsruhe.

  4. Reporting NETD: why measurement techniques matter

    NASA Astrophysics Data System (ADS)

    Rogers, Ryan K.; Edwards, W. Derrik; Waddle, Caleb E.; Dobbins, Christopher L.; Wood, Sam B.

    2014-05-01

    For over 30 years, the U.S. Army Aviation and Missile Research, Development, and Engineering Center (AMRDEC) has specialized in characterizing the performance of infrared (IR) imaging systems in the laboratory and field. In the late 90's, AMRDEC developed the Automated IR Sensor Test Facility (AISTF) which allowed efficient deployment testing of aviation and missile IR sensor systems. More recently, AMRDEC has tested many uncooled infrared (UCIR) sensor systems that have size, weight, power, and cost (SWAPC) benefits for certain fielded U.S. Army imaging systems. To compensate for relatively poor detector sensitivities, most UCIR systems operate with very fast focal ratio or F-number (f/#) optics. AMRDEC has recently found that measuring the Noise Equivalent Temperature Difference (NETD) with traditional techniques used with cooled infrared systems produce biased results when applied to systems with faster f/# values or obscurations. Additionally, in order to compare these camera cores or sensor systems to one another, it is imperative to scale the NETD values for f/#, focus distance, and waveband differences accurately. This paper will outline proper measurement techniques to report UCIR camera core and system-level NETD, as well as demonstrate methods to scale the metric for these differences.

  5. absorption sensor for sensitive temperature and species measurements in high-temperature gases

    NASA Astrophysics Data System (ADS)

    Spearrin, R. M.; Ren, W.; Jeffries, J. B.; Hanson, R. K.

    2014-09-01

    A continuous-wave laser absorption diagnostic, based on the infrared CO2 bands near 4.2 and 2.7 μm, was developed for sensitive temperature and concentration measurements in high-temperature gas systems using fixed-wavelength methods. Transitions in the respective R-branches of both the fundamental υ 3 band (~2,350 cm-1) and combination υ 1 + υ 3 band (~3,610 cm-1) were chosen based on absorption line-strength, spectral isolation, and temperature sensitivity. The R(76) line near 2,390.52 cm-1 was selected for sensitive CO2 concentration measurements, and a detection limit of <5 ppm was achieved in shock tube kinetics experiments (~1,300 K). A cross-band, two-line thermometry technique was also established utilizing the R(96) line near 2,395.14 cm-1, paired with the R(28) line near 3,633.08 cm-1. This combination yields high temperature sensitivity (ΔE" = 3,305 cm-1) and expanded range compared with previous intra-band CO2 sensors. Thermometry performance was validated in a shock tube over a range of temperatures (600-1,800 K) important for combustion. Measured temperature accuracy was demonstrated to be better than 1 % over the entire range of conditions, with a standard error of ~0.5 % and µs temporal resolution.

  6. Low-energy neutron flux measurement using a resonance absorption filter surrounding a lithium glass scintillator

    NASA Astrophysics Data System (ADS)

    Ghal-Eh, N.; Koohi-Fayegh, R.; Hamidi, S.

    2007-06-01

    The resonance absorption filter technique has been used to determine the thermal/epithermal neutron flux. The main idea in this technique is to use an element with a high and essentially singular resonance in the neutron absorption cross section as a filter surrounding a miniature-type lithium glass scintillator. The count with and without the filter surrounding the detector gives the number of resonance-energy neutrons. Some preliminary results and a comparison with the MCNP code are shown.

  7. A new direct absorption measurement for high precision and accurate measurement of water vapor in the UT/LS

    NASA Astrophysics Data System (ADS)

    Sargent, M. R.; Sayres, D. S.; Smith, J. B.; Anderson, J.

    2011-12-01

    Highly accurate and precise water vapor measurements in the upper troposphere and lower stratosphere are critical to understanding the climate feedbacks of water vapor and clouds in that region. However, the continued disagreement among water vapor measurements (~1 - 2 ppmv) are too large to constrain the role of different hydration and dehydration mechanisms operating in the UT/LS, with model validation dependent upon which dataset is chosen. In response to these issues, we present a new instrument for measurement of water vapor in the UT/LS that was flown during the April 2011 MACPEX mission out of Houston, TX. The dual axis instrument combines the heritage and validated accuracy of the Harvard Lyman-alpha instrument with a newly designed direct IR absorption instrument, the Harvard Herriott Hygrometer (HHH). The Lyman-alpha detection axis has flown aboard NASA's WB-57 and ER2 aircraft since 1994, and provides a requisite link between the new HHH instrument and the long history of Harvard water vapor measurements. The instrument utilizes the highly sensitive Lyman-alpha photo-fragment fluorescence detection method; its accuracy has been demonstrated though rigorous laboratory calibrations and in situ diagnostic procedures. The Harvard Herriott Hygrometer employs a fiber coupled near-IR laser with state-of-the-art electronics to measure water vapor via direct absorption in a spherical Herriott cell of 10 cm length. The instrument demonstrated in-flight precision of 0.1 ppmv (1-sec, 1-sigma) at mixing ratios as low as 5 ppmv with accuracies of 10% based on careful laboratory calibrations and in-flight performance. We present a description of the measurement technique along with our methodology for calibration and details of the measurement uncertainties. The simultaneous utilization of radically different measurement techniques in a single duct in the new Harvard Water Vapor (HWV) instrument allows for the constraint of systematic errors inherent in each technique

  8. Helium-flow measurement using ultrasonic technique

    SciTech Connect

    Sondericker, J.H.

    1983-01-01

    While designing cryogenic instrumentation for the Colliding Beam Accelerator (CBA) helium-distribution system it became clear that accurate measurement of mass flow of helium which varied in temperature from room to sub-cooled conditions would be difficult. Conventional venturi flow meters full scale differential pressure signal would decrease by more than an order of magnitude during cooldown causing unacceptable error at operating temperature. At sub-cooled temperatures, helium would be pumped around cooling loops by an efficient, low head pressure circulating compressor. Additional pressure drop meant more pump work was necessary to compress the fluid resulting in a higher outlet temperature. The ideal mass flowmeter for this application was one which did not add pressure drop to the system, functioned over the entire temperature range, has high resolution and delivers accurate mass flow measurement data. Ultrasonic flow measurement techniques used successfully by the process industry, seemed to meet all the necessary requirements. An extensive search for a supplier of such a device found that none of the commercial stock flowmeters were adaptable to cryogenic service so the development of the instrument was undertaken by the CBA Cryogenic Control and Instrumentation Engineering Group at BNL.

  9. Stark effect spectrophone for continuous absorption spectra monitoring. [a technique for gas analysis

    NASA Technical Reports Server (NTRS)

    Kavaya, M. J. (Inventor)

    1981-01-01

    A Stark effect spectrophone using a pulsed or continuous wave laser having a beam with one or more absorption lines of a constituent of an unknown gas is described. The laser beam is directed through windows of a closed cell while the unknown gas to be modified flows continuously through the cell between electric field plates disposed in the cell on opposite sides of the beam path through the cell. When the beam is pulsed, energy absorbed by the gas increases at each point along the beam path according to the spectral lines of the constituents of the gas for the particular field strengths at those points. The pressure measurement at each point during each pulse of energy yields a plot of absorption as a function of electric field for simultaneous detection of the gas constituents. Provision for signal averaging and modulation is included.

  10. An instrumented pendulum system for measuring energy absorption during fracture insult to large animal joints in vivo.

    PubMed

    Diestelmeier, B W; Rudert, M J; Tochigi, Y; Baer, T E; Fredericks, D C; Brown, T D

    2014-06-01

    For systematic laboratory studies of bone fractures in general and intra-articular fractures in particular, it is often necessary to control for injury severity. Quantitatively, a parameter of primary interest in that regard is the energy absorbed during the injury event. For this purpose, a novel technique has been developed to measure energy absorption in experimental impaction. The specific application is for fracture insult to porcine hock (tibiotalar) joints in vivo, for which illustrative intra-operative data are reported. The instrumentation allowed for the measurement of the delivered kinetic energy and of the energy passed through the specimen during impaction. The energy absorbed by the specimen was calculated as the difference between those two values. A foam specimen validation study was first performed to compare the energy absorption measurements from the pendulum instrumentation versus the work of indentation performed by an MTS machine. Following validation, the pendulum apparatus was used to measure the energy absorbed during intra-articular fractures created in 14 minipig hock joints in vivo. The foam validation study showed close correspondence between the pendulum-measured energy absorption and MTS-performed work of indentation. In the survival animal series, the energy delivered ranged from 31.5 to 48.3 Js (41.3±4.0, mean±s.d.) and the proportion of energy absorbed to energy delivered ranged from 44.2% to 64.7% (53.6%±4.5%). The foam validation results support the reliability of the energy absorption measure provided by the instrumented pendulum system. Given that a very substantial proportion of delivered energy passed--unabsorbed--through the specimens, the energy absorption measure provided by this novel technique arguably provides better characterization of injury severity than is provided simply by energy delivery.

  11. Measurement of high viscosity with laser induced surface deformation technique

    SciTech Connect

    Yoshitake, Y.; Mitani, S.; Sakai, K.; Takagi, K.

    2005-01-15

    A technique for viscosity measurement was developed based on the principle of laser-induced surface deformation. Light incident into liquids increases its momentum due to the difference in refractive index and gives the surface an upward force as a reaction. The plane surface thus swells up and deforms, and the shape is determined so that the force is balanced with the surface tension and the gravity. On sudden laser irradiation, the deformation inevitably accompanies a viscous flow and exhibits a relaxational behavior with a delay time, which gives the viscosity. Theoretical prediction of the step-response function was given that takes surface tension waves excited by the laser into consideration. Nd-yttritium-aluminum-garnet laser with 0.6 W output was focused to {approx}200 {mu}m beam waist and used for the pumping. The deformation process was observed sensitively with another probe laser illuminating the activated area. This system was tested with the standard liquids for viscosity ranging from 1 to 10{sup 6} cSt. The results demonstrated the validity of this technique, though a correction for the inertia effect was needed in the range lower than 10 cSt. Further, effect of the thermal expansion by a slight optical absorption was discussed. This technique is especially useful at high viscosities since the measurement takes only a few seconds even in the specimen with 10{sup 6} cSt. Besides the rapidity, it has a great advantage of a noncontact feature and is appropriate for measuring the liquids that strongly dislike contamination. It has also potential applications in industries, measurement of liquids isolated in a production line, for instance.

  12. Erosive Burning Study Utilizing Ultrasonic Measurement Techniques

    NASA Technical Reports Server (NTRS)

    Furfaro, James A.

    2003-01-01

    A 6-segment subscale motor was developed to generate a range of internal environments from which multiple propellants could be characterized for erosive burning. The motor test bed was designed to provide a high Mach number, high mass flux environment. Propellant regression rates were monitored for each segment utilizing ultrasonic measurement techniques. These data were obtained for three propellants RSRM, ETM- 03, and Castor@ IVA, which span two propellant types, PBAN (polybutadiene acrylonitrile) and HTPB (hydroxyl terminated polybutadiene). The characterization of these propellants indicates a remarkably similar erosive burning response to the induced flow environment. Propellant burnrates for each type had a conventional response with respect to pressure up to a bulk flow velocity threshold. Each propellant, however, had a unique threshold at which it would experience an increase in observed propellant burn rate. Above the observed threshold each propellant again demonstrated a similar enhanced burn rate response corresponding to the local flow environment.

  13. Exospheric hydrogen density estimates from absorption dips in GOES solar irradiance measurements

    NASA Astrophysics Data System (ADS)

    Machol, J. L.; Loto'aniu, P. T. M.; Snow, M. A.; Viereck, R. A.; Woodraska, D.; Jones, A. R.; Bailey, J. J.; Gruntman, M.; Redmon, R. J.

    2015-12-01

    We use extreme ultraviolet (EUV) measurements of solar irradiance from GOES satellites to derive daily hydrogen (H) density distributions of the terrestrial upper atmosphere. GOES satellites are in geostationary orbit and measure solar irradiance in a wavelength band around the Lyman-alpha line. When the satellite is on the night-side of the Earth looking through the atmosphere at the Sun, the irradiance exhibits absorption/scattering loss. Using these daily dips in the measured irradiance, we can estimate a simple hydrogen density distribution for the exosphere based on the integrated scattering loss along the line of sight towards the Sun. We show preliminary results from this technique and compare the derived exospheric H density distributions with other data sets for different solar, geomagnetic and atmospheric conditions. The GOES observations will be available for many years into the future and so potentially can provide continuous monitoring of exospheric H density for use in full atmospheric models. These measurements may also provide a means to validate, calibrate and improve other exospheric models. Improved models will help with the understanding of the solar-upper atmospheric coupling and the decay of the ions in the magnetospheric ring current during geomagnetic storms. Long-term observations of trends can be used to monitor impacts of climate change and improved satellite drag models will help satellite operator adjust satellite orbits during geomagnetic storms. We discuss planned improvements to this technique.

  14. Airborne 2-Micron Double-Pulsed Integrated Path Differential Absorption Lidar for Column CO2 Measurement

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Yu, Jirong; Petros, Mulugeta; Refaat, Tamer F.; Remus, Ruben G.; Fay, James J.; Reithmaier, Karl

    2014-01-01

    Double-pulse 2-micron lasers have been demonstrated with energy as high as 600 millijouls and up to 10 Hz repetition rate. The two laser pulses are separated by 200 microseconds and can be tuned and locked separately. Applying double-pulse laser in DIAL system enhances the CO2 measurement capability by increasing the overlap of the sampled volume between the on-line and off-line. To avoid detection complicity, integrated path differential absorption (IPDA) lidar provides higher signal-to-noise ratio measurement compared to conventional range-resolved DIAL. Rather than weak atmospheric scattering returns, IPDA rely on the much stronger hard target returns that is best suited for airborne platforms. In addition, the IPDA technique measures the total integrated column content from the instrument to the hard target but with weighting that can be tuned by the transmitter. Therefore, the transmitter could be tuned to weight the column measurement to the surface for optimum CO2 interaction studies or up to the free troposphere for optimum transport studies. Currently, NASA LaRC is developing and integrating a double-Pulsed 2-micron direct detection IPDA lidar for CO2 column measurement from an airborne platform. The presentation will describe the development of the 2-micron IPDA lidar system and present the airborne measurement of column CO2 and will compare to in-situ measurement for various ground target of different reflectivity.

  15. Airborne 2-micron double-pulsed integrated path differential absorption lidar for column CO2 measurement

    NASA Astrophysics Data System (ADS)

    Singh, Upendra N.; Yu, Jirong; Petros, Mulugeta; Refaat, Tamer F.; Remus, Ruben G.; Fay, James J.; Reithmaier, Karl

    2014-10-01

    Double-pulse 2-micron lasers have been demonstrated with energy as high as 600 mJ and up to 10 Hz repetition rate. The two laser pulses are separated by 200 µs and can be tuned and locked separately. Applying double-pulse laser in DIAL system enhances the CO2 measurement capability by increasing the overlap of the sampled volume between the on-line and off-line. To avoid detection complicity, integrated path differential absorption (IPDA) lidar provides higher signal-to-noise ratio measurement compared to conventional range-resolved DIAL. Rather than weak atmospheric scattering returns, IPDA rely on the much stronger hard target returns that is best suited for airborne platforms. In addition, the IPDA technique measures the total integrated column content from the instrument to the hard target but with weighting that can be tuned by the transmitter. Therefore, the transmitter could be tuned to weight the column measurement to the surface for optimum CO2 interaction studies or up to the free troposphere for optimum transport studies. Currently, NASA LaRC is developing and integrating a double-Pulsed 2-µm direct detection IPDA lidar for CO2 column measurement from an airborne platform. The presentation will describe the development of the 2-μm IPDA lidar system and present the airborne measurement of column CO2 and will compare to in-situ measurement for various ground target of different reflectivity.

  16. Made-to-measure galaxy modelling utilising absorption line strength data

    NASA Astrophysics Data System (ADS)

    Long, R. J.

    2016-12-01

    We enhance the Syer & Tremaine made-to-measure (M2M) particle method of stellar dynamical modelling to model simultaneously both kinematic data and absorption line strength data, thus creating a ‘chemo-M2M’ modelling scheme. We apply the enhanced method to four galaxies (NGC 1248, NGC 3838, NGC 4452, NGC 4551) observed using the SAURON integral-field spectrograph as part of the ATLAS3D programme. We are able to reproduce successfully the 2D line strength data achieving mean χ2 per bin values of ≈ 1 with > 95% of particles having converged weights. Because M2M uses a 3D particle system, we are also able to examine the underlying 3D line strength distributions. The extent to which these distributions are plausible representations of real galaxies requires further consideration. Overall, we consider the modelling exercise to be a promising first step in developing a ‘chemo-M2M’ modelling system and in understanding some of the issues to be addressed. While the made-to-measure techniques developed have been applied to absorption line strength data, they are in fact general and may be of value in modelling other aspects of galaxies.

  17. Z-Scan Measurement of the Nonlinear Absorption of a Thin Gold Film

    NASA Technical Reports Server (NTRS)

    Smith, David D.; Yoon, Youngkwon; Boyd, Robert W.; Campbell, Joseph K.; Baker, Lane A.; Crooks, Richard M.; George, Michael

    1999-01-01

    We have used the z-scan technique at a wavelength (532 nm) near the transmission window of bulk gold to measure the nonlinear absorption coefficient of continuous approximately 50-Angstrom-thick gold films, deposited onto surface-modified quartz substrates. For highly absorbing media such as metals, we demonstrate that determination of either the real or imaginary part of the third-order susceptibility requires a measurement of both nonlinear absorption and nonlinear refraction, i.e. both open- and closed-aperture z-scans must be performed. Closed-aperture z-scans did not yield a sufficient signal for the determination of the nonlinear refraction. However, open-aperture z-scans yielded values ranging from Beta = 1.9 x 10(exp -3) to 5.3 x 10(exp -3) cm/W in good agreement with predictions which ascribe the nonlinear response to a Fermi smearing mechanism. We note that the sign of the nonlinearity is reversed from that of gold nanoparticle composites, in accordance with the predictions of mean field theories.

  18. NO_2 Trace Measurements by Optical-Feedback Cavity-Enhanced Absorption Spectroscopy

    NASA Astrophysics Data System (ADS)

    Ventrillard-Courtillot, I.; Desbois, Th.; Foldes, T.; Romanini, D.

    2009-06-01

    In order to reach the sub-ppb NO_2 detection level required for environmental applications in remote areas, we develop a spectrometer based on a technique introduced a few years ago, named Optical-Feedback Cavity-Enhanced Absorption Spectroscopy (OF-CEAS) [1]. It allows very sensitive and selective measurements, together with the realization of compact and robust set-ups as was subsequently demonstrated during measurements campaigns in harsh environments [2]. OF-CEAS benefits from the optical feedback to efficiently inject a cw-laser in a V-shaped high finesse cavity (typically 10 000). Cavity-enhanced absorption spectra are acquired on a small spectral region (˜1 cm^{-1}) that enables selective and quantitative measurements at a fast acquisition rate with a detection limit of several 10^{-10} cm^{-1} as reported in this work. Spectra are obtained with high spectral definition (150 MHz highly precisely spaced data points) and are self calibrated by cavity rind-down measurements regularly performed (typically every second). NO_2 measurements are performed with a commercial extended cavity diode laser around 411 nm, spectral region where intense electronic transitions occur. We will describe the set-up developed for in-situ measurements allowing real time concentration measurements at typically 5 Hz; and then report on the measurements performed with calibrated NO_2 reference samples to evaluate the linearity of the apparatus. The minimum detectable absorption loss is estimated by considering the standard deviation of the residual of one spectrum. We achieved 2x10^{-10} cm^{-1} for a single spectrum recorded in less than 100 ms at 100 mbar. It leads to a potential detection limit of 3x10^8 molecules/cm^3, corresponding to about 150 pptv at this pressure. [1] J. Morville, S. Kassi, M. Chenevier, and D. Romanini, Appl. Phys. B, 80, 1027 (2005). [2] D. Romanini, M. Chenevrier, S. Kassi, M. Schmidt, C. Valant, M. Ramonet, J. Lopez, and H.-J. Jost, Appl. Phys. B, 83, 659

  19. EDITORIAL: Measurement techniques for multiphase flows Measurement techniques for multiphase flows

    NASA Astrophysics Data System (ADS)

    Okamoto, Koji; Murai, Yuichi

    2009-11-01

    Research on multiphase flows is very important for industrial applications, including power stations, vehicles, engines, food processing and so on. Multiphase flows originally have nonlinear features because of multiphase systems. The interaction between the phases plays a very interesting role in the flows. The nonlinear interaction causes the multiphase flows to be very complicated. Therefore techniques for measuring multiphase flows are very useful in helping to understand the nonlinear phenomena. The state-of-the-art measurement techniques were presented and discussed at the sixth International Symposium on Measurement Techniques for Multiphase Flows (ISMTMF2008) held in Okinawa, Japan, on 15-17 December 2008. This special feature of Measurement Science and Technology includes selected papers from ISMTMF2008. Okinawa has a long history as the Ryukyus Kingdom. China, Japan and many western Pacific countries have had cultural and economic exchanges through Okinawa for over 1000 years. Much technical and scientific information was exchanged at the symposium in Okinawa. The proceedings of ISMTMF2008 apart from these special featured papers were published in Journal of Physics: Conference Series vol. 147 (2009). We would like to express special thanks to all the contributors to the symposium and this special feature. This special feature will be a milestone in measurement techniques for multiphase flows.

  20. Biomass Burning Aerosol Absorption Measurements with MODIS Using the Critical Reflectance Method

    NASA Technical Reports Server (NTRS)

    Zhu, Li; Martins, Vanderlei J.; Remer, Lorraine A.

    2010-01-01

    This research uses the critical reflectance technique, a space-based remote sensing method, to measure the spatial distribution of aerosol absorption properties over land. Choosing two regions dominated by biomass burning aerosols, a series of sensitivity studies were undertaken to analyze the potential limitations of this method for the type of aerosol to be encountered in the selected study areas, and to show that the retrieved results are relatively insensitive to uncertainties in the assumptions used in the retrieval of smoke aerosol. The critical reflectance technique is then applied to Moderate Resolution Imaging Spectrometer (MODIS) data to retrieve the spectral aerosol single scattering albedo (SSA) in South African and South American 35 biomass burning events. The retrieved results were validated with collocated Aerosol Robotic Network (AERONET) retrievals. One standard deviation of mean MODIS retrievals match AERONET products to within 0.03, the magnitude of the AERONET uncertainty. The overlap of the two retrievals increases to 88%, allowing for measurement variance in the MODIS retrievals as well. The ensemble average of MODIS-derived SSA for the Amazon forest station is 0.92 at 670 nm, and 0.84-0.89 for the southern African savanna stations. The critical reflectance technique allows evaluation of the spatial variability of SSA, and shows that SSA in South America exhibits higher spatial variation than in South Africa. The accuracy of the retrieved aerosol SSA from MODIS data indicates that this product can help to better understand 44 how aerosols affect the regional and global climate.

  1. High-resolution OH LIF velocity measurement technique for high-speed reacting flows

    NASA Technical Reports Server (NTRS)

    Klavuhn, K. G.; Gauba, G.; Mcdaniel, J. C.

    1992-01-01

    A nonintrusive optical technique was developed for the quantitative study of velocity fields in steady, high-speed, reacting flows. A narrow-linewidth laser source was tuned through an isolated OH absorption line to measure the Doppler-shifted linecenter frequency relative to an iodine reference line. A counterpropagating beam approach was used to eliminate collisional impact shift effects. Pointwise measurements of velocity were made in a unique reacting underexpanded jet facility as an extensive calibration of the technique over a wide range of flow conditions. The extension of the technique to planar measurements is also discussed.

  2. New autocorrelation technique for the IR FEL optical pulse width measurements

    SciTech Connect

    Amirmadhi, F.; Brau, K.A.; Becker, C.

    1995-12-31

    We have developed a new technique for the autocorrelation measurement of optical pulse width at the Vanderbilt University FEL center. This method is based on nonlinear absorption and transmission characteristics of semiconductors such as Ge, Te and InAs suitable for the wavelength range from 2 to over 6 microns. This approach, aside being simple and low cost, removes the phase matching condition that is generally required for the standard frequency doubling technique and covers a greater wavelength range per nonlinear material. In this paper we will describe the apparatus, explain the principal mechanism involved and compare data which have been acquired with both frequency doubling and two-photon absorption.

  3. Spatially resolved absolute diffuse reflectance measurements for noninvasive determination of the optical scattering and absorption coefficients of biological tissue

    NASA Astrophysics Data System (ADS)

    Kienle, Alwin; Lilge, Lothar; Patterson, Michael S.; Hibst, Raimund; Steiner, Rudolf; Wilson, Brian C.

    1996-05-01

    The absorption and transport scattering coefficients of biological tissues determine the radial dependence of the diffuse reflectance that is due to a point source. A system is described for making remote measurements of spatially resolved absolute diffuse reflectance and hence noninvasive, noncontact estimates of the tissue optical properties. The system incorporated a laser source and a CCD camera. Deflection of the incident beam into the camera allowed characterization of the source for absolute reflectance measurements. It is shown that an often used solution of the diffusion equation cannot be applied for these measurements. Instead, a neural network, trained on the results of Monte Carlo simulations, was used to estimate the absorption and scattering coefficients from the reflectance data. Tests on tissue-simulating phantoms with transport scattering coefficients between 0.5 and 2.0 mm-1 and absorption coefficients between 0.002 and 0.1 mm -1 showed the rms errors of this technique to be 2.6% for the transport scattering coefficient and 14% for the absorption coefficients. The optical properties of bovine muscle, adipose, and liver tissue, as well as chicken muscle (breast), were also measured ex vivo at 633 and 751 nm. For muscle tissue it was found that the Monte Carlo simulation did not agree with experimental measurements of reflectance at distances less than 2 mm from the incident beam. Carlo, neural network.

  4. Differential Absorption Measurements of Atmospheric Water Vapor with a Coherent Lidar at 2050.532 nm

    NASA Technical Reports Server (NTRS)

    Koch, Grady J.; Dharamsi, Amin; Davis, Richard E.; Petros, Mulugeta; McCarthy, John C.

    1999-01-01

    Wind and water vapor are two major factors driving the Earth's atmospheric circulation, and direct measurement of these factors is needed for better understanding of basic atmospheric science, weather forecasting, and climate studies. Coherent lidar has proved to be a valuable tool for Doppler profiling of wind fields, and differential absorption lidar (DIAL) has shown its effectiveness in profiling water vapor. These two lidar techniques are generally considered distinctly different, but this paper explores an experimental combination of the Doppler and DIAL techniques for measuring both wind and water vapor with an eye-safe wavelength based on a solid-state laser material. Researchers have analyzed and demonstrated coherent DIAL water vapor measurements at 10 micrometers wavelength based on CO2 lasers. The hope of the research presented here is that the 2 gm wavelength in a holmium or thulium-based laser may offer smaller packaging and more rugged operation that the CO2-based approach. Researchers have extensively modeled 2 um coherent lasers for water vapor profiling, but no published demonstration is known. Studies have also been made, and results published on the Doppler portion, of a Nd:YAG-based coherent DIAL operating at 1.12 micrometers. Eye-safety of the 1.12 micrometer wavelength may be a concern, whereas the longer 2 micrometer and 10 micrometer systems allow a high level of eyesafety.

  5. Differential Absorption Lidar to Measure Subhourly Variation of Tropospheric Ozone Profiles

    NASA Technical Reports Server (NTRS)

    Kuang, Shi; Burris, John F.; Newchurch, Michael J.; Johnson, Steve; Long, Stephania

    2011-01-01

    A tropospheric ozone Differential Absorption Lidar system, developed jointly by The University of Alabama in Huntsville and the National Aeronautics and Space Administration, is making regular observations of ozone vertical distributions between 1 and 8 km with two receivers under both daytime and nighttime conditions using lasers at 285 and 291 nm. This paper describes the lidar system and analysis technique with some measurement examples. An iterative aerosol correction procedure reduces the retrieval error arising from differential aerosol backscatter in the lower troposphere. Lidar observations with coincident ozonesonde flights demonstrate that the retrieval accuracy ranges from better than 10% below 4 km to better than 20% below 8 km with 750-m vertical resolution and 10-min 17 temporal integration.

  6. Differential Absorption Lidar to Measure Sub-Hourly Variation of Tropospheric Ozone Profiles

    NASA Technical Reports Server (NTRS)

    Kuang, Shi; Burris, John F.; Newchurch, Michael J.; Johnson, Steve; Long, Stephanie

    2009-01-01

    A tropospheric ozone Differential Absorption Lidar (DIAL) system, developed jointly by the University of Alabama at Huntsville and NASA, is making regular observations of ozone vertical distributions between 1 and 8 km with two receivers under both daytime and nighttime conditions using lasers at 285 and 291 nm. This paper describes the lidar system and analysis technique with some measurement examples. An iterative aerosol correction procedure reduces the retrieval error arising from differential aerosol backscatter in the lower troposphere. Lidar observations with coincident ozonesonde flights demonstrate that the retrieval accuracy ranges from better than 10% below 4 km to better than 20% below 8 km with 750-m vertical resolution and 10-min temporal integration

  7. Direct measurements of nonlinear absorption and refraction in solutions of phthalocyanines

    NASA Technical Reports Server (NTRS)

    Wei, T. H.; Hagan, D. J.; Sence, M. J.; Van Stryland, E. W.; Perry, J. W.; Coulter, D. R.

    1992-01-01

    Direct measurements are reported of the excited singlet-state absorption cross section and the associated nonlinear refractive cross section using picosecond pulses at 532 nm in solutions of phthalocyanine and naphthalocyanine dyes. By monitoring the transmittance and far-field spatial beam distortion for different pulsewidths in the picosecond regime, it is shown that both the nonlinear absorption and refraction are fluence (energy-per-unit-area) rather than irradiance dependent. Thus, excited-state absorption is the dominant nonlinear absorption process, and the observed nonlinear refraction is also due to real population excitation.

  8. Investigation of potential of differential absorption Lidar techniques for remote sensing of atmospheric pollutants

    NASA Technical Reports Server (NTRS)

    Butler, C. F.; Shipley, S. T.; Allen, R. J.

    1981-01-01

    The NASA multipurpose differential absorption lidar (DIAL) system uses two high conversion efficiency dye lasers which are optically pumped by two frequency-doubled Nd:YAG lasers mounted rigidly on a supporting structure that also contains the transmitter, receiver, and data system. The DIAL system hardware design and data acquisition system are described. Timing diagrams, logic diagrams, and schematics, and the theory of operation of the control electronics are presented. Success in obtaining remote measurements of ozone profiles with an airborne systems is reported and results are analyzed.

  9. Tunable diode laser measurements of HO2NO2 absorption coefficients near 12.5 microns

    NASA Technical Reports Server (NTRS)

    May, R. D.; Molina, L. T.; Webster, C. R.

    1988-01-01

    A tunable diode laser spectrometer has been used to measure absorption coefficients of peroxynitric acid (HO2NO2) near the 803/cm Q branch. HO2NO2 concentrations in a low-pressure flowing gas mixture were determined from chemical titration procedures and UV absorption spectroscopy. The diode laser measured absorption coefficients, at a spectral resolution of better than 0.001/cm, are about 10 percent larger than previous Fourier transform infrared measurements made at a spectral resolution of 0.06/cm.

  10. Probing local structure of pyrochlore lead zinc niobate with synchrotron x-ray absorption spectroscopy technique

    NASA Astrophysics Data System (ADS)

    Kanchiang, Kanokwan; Pramchu, Sittichain; Yimnirun, Rattikorn; Pakawanit, Phakkhananan; Ananta, Supon; Laosiritaworn, Yongyut

    2013-08-01

    Local structure of lead zinc niobate (PZN) ceramic, synthesized via B-site oxide precursor route in atmospheric pressure, was investigated using synchrotron x-ray absorption spectroscopy (XAS) technique. The x-ray absorption near-edge structure (XANES) simulation was first carried out. The XANES simulation results indicate that the PZN ceramic is in pyrochlore phase having Zn2+ substituted on Nb5+ site. Afterwards, the extended x-ray absorption fine structure (EXAFS) analysis was performed to extract the bond length information between Zn2+ and its neighboring atoms. From the EXAFS fitting, the bond length between Zn2+ and Pb2+ in the pyrochlore phase was found to be longer than the previously reported bond length in the perovskite phase. Further, with the radial distribution information of Zn2+'s neighboring atoms, the formation energies along the precursor-to-pyrochlore and precursor-to-perovskite reaction paths were calculated using the density functional theory (DFT). The calculated results show that the formation energy of the perovskite phase is noticeably higher than that of the pyrochlore phase, which is influenced by the presence of energetic Pb2+ lone pair, as the perovskite phase has shorter Zn2+ to Pb2+ bonding. This therefore suggests the steric hindrance of Pb2+ lone pair and the mutual interactions between Pb2+ lone pair and Zn2+ are main causes of the instability of lead zinc niobate in the perovskite structure and confirm the efficacy of XAS and DFT analysis in revealing local structural details of complex pyrochlore materials.

  11. Modified Sagnac interferometer for contact-free length measurement of a direct absorption cell.

    PubMed

    Elandaloussi, Hadj; Rouillé, Christian; Marie-Jeanne, Patrick; Janssen, Christof

    2016-03-10

    Accurate path length measurements in absorption cells are recurrent requirements in quantitative molecular absorption spectroscopy. A new twin path laser interferometer for length measurements in a simple direct path absorption geometry is presented, along with a full uncertainty budget. The path in an absorption cell is determined by measuring the optical path length change due to the diminution of the refractive index when the cell originally filled with nitrogen gas is evacuated. The performance of the instrument based on a stabilized HeNe laser is verified by comparison with the results of direct mechanical length measurements of a roughly 45 mm long, specially designed absorption cell. Due to a resolution of about 1/300 of a HeNe fringe, an expanded (coverage factor k=2) uncertainty of 16 μm in the length measurement is achieved, providing an expanded relative uncertainty of 3.6·10⁻⁴ for the length of our test absorption cell. This value is about 8 times lower than what has been reported previously. The instrument will be useful for precision measurements of absorption cross sections of strong absorbers which require short light paths, such as ozone, halogen oxides, sulfur dioxide, and volatile organic compounds in the UV.

  12. Broad band nonlinear optical absorption measurements of the laser dye IR26 using white light continuum Z-scan

    NASA Astrophysics Data System (ADS)

    Dey, Soumyodeep; Bongu, Sudhakara Reddy; Bisht, Prem Ballabh

    2017-03-01

    We study the nonlinear optical response of a standard dye IR26 using the Z-scan technique, but with the white light continuum. The continuum source of wavelength from 450 nm to 1650 nm has been generated from the photonic crystal fiber on pumping with 772 nm of Ti:Sapphire oscillator. The use of broadband incident pulse enables us to probe saturable absorption (SA) and reverse saturable absorption (RSA) over the large spectral range with a single Z-scan measurement. The system shows SA in the resonant region while it turns to RSA in the non-resonant regions. The low saturation intensity of the dye can be explained based on the simultaneous excitation from ground states to various higher energy levels with the help of composite energy level diagram. The cumulative effects of excited state absorption and thermal induced nonlinear optical effects are responsible for the observed RSA.

  13. Spatially resolved measurements of nitrogen dioxide in an urban environment using concurrent multi-axis differential optical absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Leigh, R. J.; Corlett, G. K.; Frieß, U.; Monks, P. S.

    2006-12-01

    A novel system using the technique of concurrent multi-axis differential optical absorption spectroscopy system has been developed and applied to the measurement of nitrogen dioxide in an urban environment. Using five fixed telescopes, slant columns of nitrogen dioxide, ozone, water vapour, and the oxygen dimer, O4, are simultaneously retrieved in five vertically separated viewing directions. The application of this remote sensing technique in the urban environment is explored. Through, the application of several simplifying assumptions a tropospheric concentration of NO2 is derived and compared with an urban background in-situ chemiluminescence detector. The remote sensing and in-situ techniques show good agreement. Owing to the high time resolution of the measurements, the ability to image and quantify plumes within the urban environment is demonstrated. The CMAX-DOAS measurements provide a useful measure of overall NO2 concentrations on a city-wide scale.

  14. Quantitative infrared absorption cross sections of isoprene for atmospheric measurements

    SciTech Connect

    Brauer, Carolyn S.; Blake, Thomas A.; Guenther, Alex B.; Sharpe, Steven W.; Sams, Robert L.; Johnson, Timothy J.

    2014-11-19

    The OH- and O3- initiated oxidations of isoprene, which is one of the primary volatile organic compounds produced by vegetation, are a major source of atmospheric formaldehyde and other oxygenated organics, yet little quantitative IR data exists for isoprene. We thus report absorption coefficients and integrated band intensities for isoprene in the 600 - 6500 cm-1 region. The pressure-broadened (1 atmosphere N2) spectra were recorded at 278, 298 and 323 K in a 19.96 cm path length cell at 0.112 cm-1 resolution, using a Bruker 66V FTIR. Composite spectra are derived from a minimum of seven pressures at each temperature.

  15. Donnan membrane technique (DMT) for anion measurement.

    PubMed

    Vega, Flora Alonso; Weng, Liping; Temminghoff, Erwin J M; Van Riemsdijk, Willem H

    2010-04-01

    Donnan membrane technique (DMT) is developed and tested for determination of free anion concentrations. Time needed to reach the Donnan membrane equilibrium depends on type of ions and the background. The Donnan membrane equilibrium is reached in 1 day for Cl(-), 1-2 days for NO(3)(-), 1-4 days for SO(4)(2-) and SeO(4)(2-), and 1-14 days for H(2)PO(4)(-) in a background of 2-200 mM KCl or K(2)SO(4). The strongest effect of ionic strength on equilibrium time is found for H(2)PO(4)(-), followed by SO(4)(2-) and SeO(4)(2-), and then by Cl(-) and NO(3)(-). The negatively charged organic particles of fulvic and humic acids do not pass the membrane. Two approaches for the measurement of different anion species of the same element, such as SeO(4)(2-) and HSeO(3)(-), using DMT are proposed and tested. These two approaches are based on transport kinetics or response to ionic strength difference. A transport model that was developed previously for cation DMT is applied in this work to analyze the rate-limiting step in the anion DMT. In the absence of mobile/labile complexes, transport tends to be controlled by diffusion in solution at a low ionic strength, whereas at a higher ionic strength, diffusion in the membrane starts to control the transport.

  16. Evaluation of iron-containing carbon nanotubes by near edge X-ray absorption technique

    NASA Astrophysics Data System (ADS)

    Osorio, A. G.; Bergmann, C. P.

    2015-10-01

    The synthesis of carbon nanotubes (CNTs) via Chemical Vapor Deposition method with ferrocene results in CNTs filled with Fe-containing nanoparticles. The present work proposes a novel route to characterize the Fe phases in CNTs inherent to the synthesis process. CNTs were synthesized and, afterwards, the CNTs were heat treated at 1000 °C for 20 min in an inert atmosphere during a thermogravimetric experiment. X-Ray Absorption Spectroscopy (XAS) experiments were performed on the CNTs before and after the heat treatment and, also, during the heat treatment, e.g., in situ tests were performed while several Near-Edge X-Ray Absorption (XANES) spectra were collected during the heating of the samples. The XAS technique was successfully applied to evaluate the phases encapsulated by CNTs. Phase transformations of the Fe-based nanoparticles were also observed from iron carbide to metallic iron when the in situ experiments were performed. Results also indicated that the applied synthesis method guarantees that Fe phases are not oxidize. In addition, the results show that heat treatment under inert atmosphere can control which phase remains encapsulated by the CNTs.

  17. Hemodynamic measurements in rat brain combining diffuse near-infrared absorption and correlation spectroscopies

    NASA Astrophysics Data System (ADS)

    Yu, Guoqiang; Durduran, Turgut; Furuya, Daisuke; Greenberg, Joel H.; Yodh, Arjun G.

    2002-09-01

    Measurement of concentration, oxygenation, and flow characteristics of blood cells can reveal information about tissue metabolism and functional heterogeneity. An instrument has been built that combines two near-infrared diffuse optical techniques to simultaneously monitor blood flow, blood volume and blood oxygen saturation. Diffuse correlation spectroscopy (DCS) monitors blood flow by measuring the optical phase shifts caused by moving blood cells, while diffuse photon density wave (DPDW) spectroscopy measured tissue absorption and scattering. The modularized design of the instrument provides the instrument great flexibility for trading off the temporal, spectral and spatial resolution by selecting the number of source-detector pairs and wavelengths. The frame acquisition rate of the current instrument is 0.2 Hz with 3l (wavelengths) x 15s (source positions) x 4d (detectors) for DPDW measurement in the frequency domain, and 1λ x 3s; x 9d for DCS. Higher frame acquisition rate could be achieved by reducing the spatial resolution, for example, 2 Hz with 3λ x 1s x 4d for DPDW and 1l x 1s x 9d for DCS. The unique non-contact probe mounted on the back of a camera allows non-contact measurement that avoids potentially altering blood flow. We used this instrument to monitor in vivo the hemodynamic responses in rat brain during KCl induced cortical spreading depression (CSD).

  18. Error analysis of Raman differential absorption lidar ozone measurements in ice clouds.

    PubMed

    Reichardt, J

    2000-11-20

    A formalism for the error treatment of lidar ozone measurements with the Raman differential absorption lidar technique is presented. In the presence of clouds wavelength-dependent multiple scattering and cloud-particle extinction are the main sources of systematic errors in ozone measurements and necessitate a correction of the measured ozone profiles. Model calculations are performed to describe the influence of cirrus and polar stratospheric clouds on the ozone. It is found that it is sufficient to account for cloud-particle scattering and Rayleigh scattering in and above the cloud; boundary-layer aerosols and the atmospheric column below the cloud can be neglected for the ozone correction. Furthermore, if the extinction coefficient of the cloud is ?0.1 km(-1), the effect in the cloud is proportional to the effective particle extinction and to a particle correction function determined in the limit of negligible molecular scattering. The particle correction function depends on the scattering behavior of the cloud particles, the cloud geometric structure, and the lidar system parameters. Because of the differential extinction of light that has undergone one or more small-angle scattering processes within the cloud, the cloud effect on ozone extends to altitudes above the cloud. The various influencing parameters imply that the particle-related ozone correction has to be calculated for each individual measurement. Examples of ozone measurements in cirrus clouds are discussed.

  19. Microbial Sulfate Reduction Measured by an Automated Electrical Impedance Technique

    NASA Technical Reports Server (NTRS)

    Oremland, R. S.; Silverman, M. P.

    1979-01-01

    Electrical impedance measurements are used to investigate the rates of sulfate reduction by pure cultures of and sediments containing sulfur-reducing bacteria. Changes in the electrical impedance ratios of pure cultures of Desulfovibrio aestuarii and samples of reduced sediments from San Francisco Bay were measured by a Bactometer 32, and sulfate reduction was followed by measuring the incorporation of (S-35) sulfate into metal sulfides. The growth of the bacteria in pure culture is found to result in an increase of 0.2200 in the impedance ratio within 24 h, accompanied by increases in protein, ATP, sulfide and absorptance at 660 nm, all of which are inhibited by the addition of molybdate. Similar responses were observed in the sediments, although impedance ratio responses were not completely inhibited upon the addition of molybdate, due to the presence of nonsulfate-respiring microorganisms. Experiments conducted with sterile media and autoclaved sediments indicate that the presence of H2S together with iron is responsible for the impedance effect, and sulfate reduction rates ranging between 0.85 and 1.78 mmol/l per day are estimated for the sediments by the impedance technique.

  20. Understanding refraction contrast using a comparison of absorption and refraction computed tomographic techniques

    NASA Astrophysics Data System (ADS)

    Wiebe, S.; Rhoades, G.; Wei, Z.; Rosenberg, A.; Belev, G.; Chapman, D.

    2013-05-01

    Refraction x-ray contrast is an imaging modality used primarily in a research setting at synchrotron facilities, which have a biomedical imaging research program. The most common method for exploiting refraction contrast is by using a technique called Diffraction Enhanced Imaging (DEI). The DEI apparatus allows the detection of refraction between two materials and produces a unique ''edge enhanced'' contrast appearance, very different from the traditional absorption x-ray imaging used in clinical radiology. In this paper we aim to explain the features of x-ray refraction contrast as a typical clinical radiologist would understand. Then a discussion regarding what needs to be considered in the interpretation of the refraction image takes place. Finally we present a discussion about the limitations of planar refraction imaging and the potential of DEI Computed Tomography. This is an original work that has not been submitted to any other source for publication. The authors have no commercial interests or conflicts of interest to disclose.

  1. Using broadband absorption spectroscopy to measure concentration of sulfur dioxide

    NASA Astrophysics Data System (ADS)

    Wang, H. S.; Zhang, Y. G.; Wu, S. H.; Lou, X. T.; Zhang, Z. G.; Qin, Y. K.

    2010-09-01

    A linear relationship between concentration of sulfur dioxide (SO2) and optical parameter (OP) is established using the Beer-Lambert law. The SO2 measuring system is set up to measure the concentration of sulfur dioxide in the wavelength range 275-315 nm. Experimental results indicate that the detection limit of the sulfur dioxide measuring system is below 0.2 ppm per meter of path length, and the measurement precision is better than ±1%. The proposed SO2 measuring method features limited interference from other gases and dust, and high stability and short response time.

  2. NONLINEAR-APPROXIMATION TECHNIQUE FOR DETERMINING VERTICAL OZONE-CONCENTRATION PROFILES WITH A DIFFERENTIAL-ABSORPTION LIDAR

    EPA Science Inventory

    A new technique is presented for the retrieval of ozone concentration profiles from backscattered signals obtained by a multi-wavelength differential-absorption lidar (DIAL). The technique makes it possible to reduce erroneous local fluctuations induced in the ozone-concentration...

  3. Tunable diode laser absorption sensor for temperature and velocity measurements of O2 in air flows

    NASA Technical Reports Server (NTRS)

    Philippe, L. C.; Hanson, R. K.

    1991-01-01

    A fast and nonintrusive velocity and temperature diagnostic based on oxygen absorption is presented. The system uses a GaAlAs tunable diode laser, ramped and modulated in wavelength at high frequency. Detection is performed at twice the modulating frequency, leading to second harmonic absorption lineshapes. Velocity is inferred from the wavelength shift of the absorption line center due to the Doppler effect. Temperature is determined by comparing experimental and calculated lineshapes. Capabilities of the technique for studies of transient high-speed flows are demonstrated in shock tube experiments. Good agreement is obtained with predicted temperatures and velocities when pressure-induced shifts are accounted for.

  4. Remote-Sensing Technique for Determination of the Volume Absorption Coefficient of Turbid Water

    NASA Astrophysics Data System (ADS)

    Sydor, Michael; Arnone, Robert A.; Gould, Richard W., Jr.; Terrie, Gregory E.; Ladner, Sherwin D.; Wood, Christoper G.

    1998-07-01

    We use remote-sensing reflectance from particulate R rs to determine the volume absorption coefficient a of turbid water in the 400 700-nm spectral region. The calculated and measured values of a ( ) show good agreement for 0 . 5 a 10 (m 1 ). To determine R rs from a particulate, we needed to make corrections for remote-sensing reflectance owing to surface roughness S rs . We determined the average spectral distribution of S rs from the difference in total remote-sensing reflectance measured with and without polarization. The spectral shape of S rs showed an excellent fit to theoretical formulas for glare based on Rayleigh and aerosol scattering from the atmosphere.

  5. Cyclotron-absorption measurement of the runaway-electron distribution in a tokamak

    SciTech Connect

    Zvonkov, A.V.; Suvorov, E.V.; Timofeev, A.V.; Fraiman, A.A.

    1983-03-01

    The distribution function of runaway electrons in a tokamak can be determined in the slightly relativistic region from measurements of the absorption coefficient corresponding to electron cyclotron waves. The plasma should be probed in the vertical direction.

  6. Comparing and assessing different measurement techniques for mercury in coal systhesis gas

    SciTech Connect

    Maxwell, D.P.; Richardson, C.F.

    1995-11-01

    Three mercury measurement techniques were performed on synthesis gas streams before and after an amine-based sulfur removal system. The syngas was sampled using (1) gas impingers containing a nitric acid-hydrogen peroxide solution, (2) coconut-based charcoal sorbent, and (3) an on-line atomic absorption spectrophotometer equipped with a gold amalgamation trap and cold vapor cell. Various impinger solutions were applied upstream of the gold amalgamation trap to remove hydrogen sulfide and isolate oxidized and elemental species of mercury. The results from these three techniques are compared to provide an assessment of these measurement techniques in reducing gas atmospheres.

  7. Spectroscopic Measurement Techniques for Aerospace Flows

    NASA Technical Reports Server (NTRS)

    Danehy, Paul M.; Bathel, Brett F.; Johansen, Craig T.; Cutler, Andrew D.; Hurley, Samantha

    2014-01-01

    The conditions that characterize aerospace flows are so varied, that a single diagnostic technique is not sufficient for its measurement. Fluid dynamists use knowledge of similarity to help categorize and focus on different flow conditions. For example, the Reynolds number represents the ratio of inertial to viscous forces in a flow. When the velocity scales, length scales, and gas density are large and the magnitude of the molecular viscosity is low, the Reynolds number becomes large. This corresponds to large scale vehicles (e.g Airbus A380), fast moving objects (e.g. artillery projectiles), vehicles in dense fluids (e.g. submarine in water), or flows with low dynamic viscosity (e.g. skydiver in air). In each of these cases, the inertial forces dominate viscous forces, and unsteady turbulent fluctuations in the flow variables are observed. In contrast, flows with small length scales (e.g. dispersion of micro-particles in a solid rocket nozzle), slow moving objects (e.g. micro aerial vehicles), flows with low density gases (e.g. atmospheric re-entry), or fluids with a large magnitude of viscosity (e.g. engine coolant flow), all have low Reynolds numbers. In these cases, viscous forces become very important and often the flows can be steady and laminar. The Mach number, which is the ratio of the velocity to the speed of sound in the medium, also helps to differentiate types of flows. At very low Mach numbers, acoustic waves travel much faster than the object, and the flow can be assumed to be incompressible (e.g. Cessna 172 aircraft). As the object speed approaches the speed of sound, the gas density can become variable (e.g. flow over wing of Learjet 85). When the object speed is higher than the speed of sound (Ma > 1), the presences of shock waves and other gas dynamic features can become important to the vehicle performance (e.g. SR-71 Blackbird). In the hypersonic flow regime (Ma > 5), large changes in temperature begin to affect flow properties, causing real

  8. Quantitative infrared absorption cross sections of isoprene for atmospheric measurements

    DOE PAGES

    Brauer, C. S.; Blake, T. A.; Guenther, A. B.; ...

    2014-11-19

    Isoprene (C5H8, 2-methyl-1,3-butadiene) is a volatile organic compound (VOC) and is one of the primary contributors to annual global VOC emissions. Isoprene is produced primarily by vegetation as well as anthropogenic sources, and its OH- and O3-initiated oxidations are a major source of atmospheric oxygenated organics. Few quantitative infrared studies have been reported for isoprene, limiting the ability to quantify isoprene emissions via remote or in situ infrared detection. We thus report absorption cross sections and integrated band intensities for isoprene in the 600–6500 cm-1 region. The pressure-broadened (1 atmosphere N2) spectra were recorded at 278, 298, and 323 Kmore » in a 19.94 cm path-length cell at 0.112 cm-1 resolution, using a Bruker IFS 66v/S Fourier transform infrared (FTIR) spectrometer. Composite spectra are derived from a minimum of seven isoprene sample pressures, each at one of three temperatures, and the number densities are normalized to 296 K and 1 atm.« less

  9. Determination of mercury in an assortment of dietary supplements using an inexpensive combustion atomic absorption spectrometry technique.

    PubMed

    Levine, Keith E; Levine, Michael A; Weber, Frank X; Hu, Ye; Perlmutter, Jason; Grohse, Peter M

    2005-01-01

    The concentrations of mercury in forty, commercially available dietary supplements, were determined using a new, inexpensive analysis technique. The method involves thermal decomposition, amalgamation, and detection of mercury by atomic absorption spectrometry with an analysis time of approximately six minutes per sample. The primary cost savings from this approach is that labor-intensive sample digestion is not required prior to analysis, further automating the analytical procedure. As a result, manufacturers and regulatory agencies concerned with monitoring lot-to-lot product quality may find this approach an attractive alternative to the more classical acid-decomposition, cold vapor atomic absorption methodology. Dietary supplement samples analyzed included astragalus, calcium, chromium picolinate, echinacea, ephedra, fish oil, ginger, ginkgo biloba, ginseng, goldenseal, guggul, senna, St John's wort, and yohimbe products. Quality control samples analyzed with the dietary supplements indicated a high level of method accuracy and precision. Ten replicate preparations of a standard reference material (NIST 1573a, tomato leaves) were analyzed, and the average mercury recovery was 109% (2.0% RSD). The method quantitation limit was 0.3 ng, which corresponded to 1.5 ng/g sample. The highest found mercury concentration (123 ng/g) was measured in a concentrated salmon oil sample. When taken as directed by an adult, this product would result in an approximate mercury ingestion of 7 mug per week.

  10. Determination of Mercury in an Assortment of Dietary Supplements Using an Inexpensive Combustion Atomic Absorption Spectrometry Technique

    PubMed Central

    Levine, Michael A.; Weber, Frank X.; Hu, Ye; Perlmutter, Jason; Grohse, Peter M.

    2005-01-01

    The concentrations of mercury in forty, commercially available dietary supplements, were determined using a new, inexpensive analysis technique. The method involves thermal decomposition, amalgamation, and detection of mercury by atomic absorption spectrometry with an analysis time of approximately six minutes per sample. The primary cost savings from this approach is that labor-intensive sample digestion is not required prior to analysis, further automating the analytical procedure. As a result, manufacturers and regulatory agencies concerned with monitoring lot-to-lot product quality may find this approach an attractive alternative to the more classical acid-decomposition, cold vapor atomic absorption methodology. Dietary supplement samples analyzed included astragalus, calcium, chromium picolinate, echinacea, ephedra, fish oil, ginger, ginkgo biloba, ginseng, goldenseal, guggul, senna, St John's wort, and yohimbe products. Quality control samples analyzed with the dietary supplements indicated a high level of method accuracy and precision. Ten replicate preparations of a standard reference material (NIST 1573a, tomato leaves) were analyzed, and the average mercury recovery was 109% (2.0% RSD). The method quantitation limit was 0.3 ng, which corresponded to 1.5 ng/g sample. The highest found mercury concentration (123 ng/g) was measured in a concentrated salmon oil sample. When taken as directed by an adult, this product would result in an approximate mercury ingestion of 7 μg per week. PMID:18924735

  11. Shock tube measurements of the optical absorption of triatomic carbon, C3

    NASA Technical Reports Server (NTRS)

    Jones, J. J.

    1977-01-01

    The spectral absorption of C3 has been measured in a shock tube using a test gas mixture of acetylene diluted with argon. The absorption of a pulsed xenon light source was measured by means of eight photomultiplier channels to a spectrograph and an accompanying drum camera. The postshock test gas temperature and pressure were varied over the range 3300-4300 K and 0.36 to 2.13 atmospheres, respectively. The results showed appreciable absorption from C3 for the wavelength range 300 to 540 nanometers. The computed electronic oscillator strength varied from 0.12 to 0.06 as a function of temperature.

  12. Mass specific optical absorption coefficients of mineral dust components measured by a multi wavelength photoacoustic spectrometer

    NASA Astrophysics Data System (ADS)

    Utry, N.; Ajtai, T.; Pintér, M.; Tombácz, E.; Illés, E.; Bozóki, Z.; Szabó, G.

    2014-09-01

    Mass specific optical absorption coefficients of various mineral dust components including silicate clays (illite, kaolin and bentonite), oxides (quartz, hematite and rutile), and carbonate (limestone) were determined at wavelengths of 1064, 532, 355 and 266 nm. These values were calculated from aerosol optical absorption coefficients measured by a multi-wavelength photoacoustic (PA) instrument, the mass concentration and the number size distribution of the generated aerosol samples as well as the size transfer functions of the measuring instruments. These results are expected to have considerable importance in global radiative forcing calculations. They can also serve as reference for validating calculated wavelength dependent imaginary parts (κ) of complex refractive indices which up to now have been typically deduced from bulk phase measurements by using indirect measurement methods. Accordingly, the presented comparison of the measured and calculated aerosol optical absorption spectra revealed the strong need for standardized sample preparation and measurement methodology in case of bulk phase measurements.

  13. Technique for measuring atomic recoil frequency using coherence functions

    NASA Astrophysics Data System (ADS)

    Beattie, S.; Barrett, B.; Chan, I.; Mok, C.; Yavin, I.; Kumarakrishnan, A.

    2009-02-01

    We have developed a technique for measuring the atomic recoil frequency using a single-state echo-type atom interferometer that manipulates laser-cooled atoms in the ground state. The interferometer relies on momentum-state interference due to two standing-wave pulses that produce density gratings. The interference is modified by applying a third standing-wave pulse during the interferometer pulse sequence. As a result, the grating contrast exhibits periodic revivals at the atomic recoil frequency ωr as a function of the time at which the third pulse is applied, allowing ωr to be measured easily and precisely. The contrast is accurately described by a coherence function, which is the Fourier transform of the momentum distribution, produced by the third pulse and by the theory of echo formation. If the third pulse is a traveling wave, loss of grating contrast is observed, an effect also described by a coherence function. The decay of the grating contrast as a function of continuous-wave light intensity is used to infer the cross section for photon absorption.

  14. Simple system for measuring tritium Ad/absorption using a 2. pi. counter and thermal desorption spectrometer

    SciTech Connect

    Miyake, H.; Matsuyama, M.; Watanabe, K. ); Cowgill, D.F. )

    1992-03-01

    In this paper, the authors develop a simple system using tritium tracer and thermal desorption techniques to measure the tritium adsorption and/or absorption on/in a material having typical surface conditions: namely, not cleaned surface. The tritium counting devices used were a 2{pi} counter and conventional proportional counter. With this system, the amounts of ad/absorption could be measured without exposing the samples to air after exposing them to tritium gas. The overall efficiency (F) of the 2{pi} counter was described at F = exp({minus}2.64h), where h is the distance from the sample to the detector. Ad/absorption measurements were carried out for several materials used for fabricating conventional vacuum systems. The results were, in the order of decreasing amounts of ad/absorption, as (fiber reinforced plastics(FRP)) {gt} (nickel(Ni), molybdenum disulfide(MoS{sub 2})) {gt} (stainless steel (SS304), iron(Fe), aluminum alloy(A2219)) {gt} (boron nitride(h-BN), silicon carbide (SiC), SS304 passivated by anodic oxidation layers(ASS) and that by boron nitride segregation layers (BSS)). The relative amounts were abut 100 for Ni and 0.1 for ASS and BSS, being normalized to Fe = 1.

  15. Measurement of Carbon Dioxide Column via Space Borne Laser Absorption

    NASA Technical Reports Server (NTRS)

    Heaps, WIlliam S.

    2007-01-01

    In order to better understand the budget of carbon dioxide in the Earth's atmosphere it is necessary to develop a global high precision understanding of the carbon dioxide column. In order to uncover the 'missing sink that is responsible for the large discrepancies in the budget as we presently understand it calculation has indicated that measurement accuracy on the order of 1 ppm is necessary. Because typical column average CO2 has now reached 380 ppm this represents a precision on the order of .25% for these column measurements. No species has ever been measured from space at such a precision. In recognition of the importance of understanding the CO2 budget in order to evaluate its impact on global warming the National Research Council in its decadal survey report to NASA recommended planning for a laser based total CO2 mapping mission in the near future. The extreme measurement accuracy requirements on this mission places very strong requirements on the laser system used for the measurement. This work presents an analysis of the characteristics necessary in a laser system used to make this measurement. Consideration is given to the temperature dependence, pressure broadening, and pressure shift of the CO2 lines themselves and how these impact the laser system characteristics Several systems for meeting these requirements that are under investigation at various institutions in the US as well as Europe will be discussed.

  16. Formation and microwave absorption of barium and strontium ferrite prepared by sol-gel technique

    NASA Astrophysics Data System (ADS)

    Sürig, C.; Hempel, K. A.; Bonnenberg, D.

    1993-11-01

    Ba and Sr ferrites are prepared by sol-gel technique with different Fe/Ba(Sr) ratios in the starting materials. Magnetization, coercive, and anisotropy field strength are determined depending on the heat treatment of the gel and the iron/barium(strontium) ratio in the starting material. A two-step heat treatment is used to prepare single-domain powders with high magnetization. These powders prepared by sol-gel technique show single-domain behavior with specific magnetization σS=649 A cm2/g and coercive field strength HcM=402 kA/m in the case of Ba ferrite and σS=695 A cm2/g and HcM=416 kA/m for Sr the ferrite. Al-substituted ferrites with high anisotropy field strengths are prepared additionally. Ferromagnetic resonance absorption is used to determine the anisotropy field strength and to investigate the formation process of the hexaferrite phase during the heat treatment. The beginning of hexaferrite formation occurs at annealing temperatures below 700 °C.

  17. Measurement of Two-Photon Absorption Cross Section of Metal Ions by a Mass Sedimentation Approach

    PubMed Central

    Ma, Zhuo-Chen; Chen, Qi-Dai; Han, Bing; Liu, Xue-Qing; Song, Jun-Feng; Sun, Hong-Bo

    2015-01-01

    The photo-reduction of metal ions in solution induced by femtosecond laser is an important and novel method for fabricating three-dimensional metal microstructures. However, the nonlinear absorption cross section of metal ions remains unknown because its measurement is difficult. In the present study, a method based on Two-Photon Excited Sedimentation (TPES) is proposed to measure the two-photon absorption cross section (TPACS) of metal ions in solution. The power-squared dependence of the amount of sediment on the excitation intensity was confirmed, revealing that 800 nm femtosecond laser induced reduction of metal ions was a two photon absorption process. We believe that the proposed method may be applied to measure the TPACS of several metal ions, thereby opening a new avenue towards future analysis of two-photon absorption materials. PMID:26657990

  18. Method and apparatus for background signal reduction in opto-acoustic absorption measurement

    NASA Technical Reports Server (NTRS)

    Rosengren, L. G. (Inventor)

    1976-01-01

    The sensitivity of an opto-acoustic absorption detector is increased to make it possible to measure trace amounts of constituent gases. A second beam radiation path is created through the sample cell identical to a first path except as to length, alternating the beam through the two paths and minimizing the detected pressure difference for the two paths while the beam wavelength is tuned away from the absorption lines of the sample. Then with the beam wavelength tuned to the absorption line of any constituent of interest, the pressure difference is a measure of trace amounts of the constituent. The same improved detector may also be used for measuring the absorption coefficient of known concentrations of absorbing gases.

  19. Re-Evaluation of Dust Radiative Forcing Using Remote Measurements of Dust Absorption

    NASA Technical Reports Server (NTRS)

    Kaufman, Yoram J.; Tanre, Didier; Karnieli, Arnon; Remer, Lorraine A.

    1998-01-01

    Spectral remote observations of dust properties from space and from the ground creates a powerful tool for determination of dust absorption of solar radiation with an unprecedented accuracy. Absorption is a key component in understanding dust impact on climate. We use Landsat spaceborne measurements at 0.47 to 2.2 microns over Senegal with ground based sunphotometers to find that Saharan dust absorption of solar radiation is two to four times smaller than in models. Though dust absorbs in the blue, almost no absorption was found for wavelengths greater 0.6 microns. The new finding increases by 50% recent estimated solar radiative forcing by dust and decreases the estimated dust heating of the lower troposphere. Dust transported from Asia shows slightly higher absorption probably due to the presence of black carbon from populated regions. Large scale application of this method to satellite data from the Earth Observing System can reduce significantly the uncertainty in the dust radiative effects.

  20. Broadband Lidar Technique for Precision CO2 Measurement

    NASA Technical Reports Server (NTRS)

    Heaps, William S.

    2008-01-01

    Presented are preliminary experimental results, sensitivity measurements and discuss our new CO2 lidar system under development. The system is employing an erbium-doped fiber amplifier (EDFA), superluminescent light emitting diode (SLED) as a source and our previously developed Fabry-Perot interferometer subsystem as a detector part. Global measurement of carbon dioxide column with the aim of discovering and quantifying unknown sources and sinks has been a high priority for the last decade. The goal of Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) mission is to significantly enhance the understanding of the role of CO2 in the global carbon cycle. The National Academy of Sciences recommended in its decadal survey that NASA put in orbit a CO2 lidar to satisfy this long standing need. Existing passive sensors suffer from two shortcomings. Their measurement precision can be compromised by the path length uncertainties arising from scattering within the atmosphere. Also passive sensors using sunlight cannot observe the column at night. Both of these difficulties can be ameliorated by lidar techniques. Lidar systems present their own set of problems however. Temperature changes in the atmosphere alter the cross section for individual CO2 absorption features while the different atmospheric pressures encountered passing through the atmosphere broaden the absorption lines. Currently proposed lidars require multiple lasers operating at multiple wavelengths simultaneously in order to untangle these effects. The current goal is to develop an ultra precise, inexpensive new lidar system for precise column measurements of CO2 changes in the lower atmosphere that uses a Fabry-Perot interferometer based system as the detector portion of the instrument and replaces the narrow band laser commonly used in lidars with the newly available high power SLED as the source. This approach reduces the number of individual lasers used in the system from three or more

  1. Improvement in Suppression of Pulsed Nd:YAG Laser Light With Iodine Absorption Cells for Filtered Rayleigh Scattering Measurements

    NASA Technical Reports Server (NTRS)

    Seasholtz, Richard G.; Buggele, Alvin E

    1997-01-01

    Filtered Rayleigh scattering using iodine absorption cells is an effective technique for obtaining density, temperature, and velocity measurements in high speed confined flows. By tuning a single frequency laser to a strong iodine absorption line, stray scattered laser light can be greatly suppressed. For example, the minimum transmission predicted by an iodine absorption model calculation is less than 10(exp -5) at the 18788.44/cm line using a 200 mm absorption cell containing iodine vapor at 0.46 T. Measurements obtained by other researches using a CW Nd:YAG laser agree with the model calculations. However, measurements made by us and by others using Q-switched, injection-seeded, frequency doubled Nd:YAG lasers only show minimum transmission of about 3 x 10(exp -3). This greatly reduces the applicability of the filtered Rayleigh scattering technique using these lasers in experiments having large amounts of stray scattered laser light. The purposes of the present study are to characterize the spectrum of the excess light transmitted by the iodine cell and to make changes to the laser to reduce the transmitted laser light. Transmission data as a function of laser frequency for the iodine absorption line at 18788.44/cm are presented. A planar mirror Fabry-Perot interferometer was used to characterize the frequency spectrum of the light passed through the cell. Measurements taken with the laser tuned to the center of the iodine absorption line show the light transmitted through the iodine cell to have a component with a bandwidth of about 40 GHz. This is probably caused by other modes in the laser that exist in spite of the single frequency injection beam. A second broadband component was also observed, possibly caused by the laser flash lamps or by fluorescence. An intracavity etalon was installed in the laser oscillator cavity to suppress the 40 GHz component. Measurements taken with the etalon tuned to the injection frequency showed a reduction in the transmitted

  2. Development of a cavity enhanced absorption spectrometer for airborne measurements of CH4 and CO2

    NASA Astrophysics Data System (ADS)

    O'Shea, S. J.; Bauguitte, S. J.-B.; Gallagher, M. W.; Lowry, D.; Percival, C. J.

    2013-01-01

    High-resolution CH4 and CO2 measurements were made onboard the FAAM BAe 146 UK atmospheric research aircraft during a number of field campaigns. The system was based on an infrared spectrometer using the cavity enhanced absorption spectroscopy technique. Correction functions to convert the mole fractions retrieved from the spectroscopy to dry air mole fractions were derived using laboratory experiments and over a 3 month period showed good stability. Long-term performance of the system was monitored using WMO traceable calibration gases. During the first year of operation (29 flights) analysis of the system's in-flight calibrations suggest that its measurements are accurate to -0.07 ppbv (1 σ precision at 1 Hz = 2.48 ppbv) for CH4 and -0.06 ppmv (1 σ precision at 1 Hz = 0.66 ppmv) for CO2. The system was found to be very robust, no major motion or altitude dependency could be detected in the measurements. An inter-comparison between whole air samples that were analysed post-flight for CH4 and CO2 by cavity ring down spectroscopy showed a mean difference between the two techniques of -2.4 ppbv (1 σ = 2.3 ppbv) for CH4 and -0.22 ppmv (1 σ = 0.45 ppmv) for CO2. In September 2012, the system was used to sample biomass burning plumes in Brazil as part of the SAMBBA project (South American biomass burning analysis). From these and simultaneous CO measurements, emission factors for savannah fires were calculated. These were found to be 2.2 ± 0.2 g (kg dry matter)-1 for CH4 and 1710 ± 171 g (kg dry matter)-1 for CO2, which are in excellent agreement with previous estimates in the literature.

  3. Measurement of aluminum in neuronal tissues using electrothermal atomization atomic absorption spectrophotometry

    SciTech Connect

    Pierson, K.B.; Evenson, M.A.

    1986-07-01

    Studies characterizing aluminum complexes isolated from neuronal tissues require accurate and precise techniques for aluminum measurement. A solution of 0.01 M nitric acid containing 0.2% Triton X-100 was the optimal diluent for aluminum measurement under the experimental conditions used. Three National Bureau of Standards Standard Reference Materials (SRM) were digested, and the aluminum concentration of each was measured with a Perkin-Elmer 503 atomic absorption spectrophotometer equipped with a Perkin-Elmer HGA 2100 controller. The calculated detection limit of aluminum was 120 pg using 15-..mu..L sample injections (8 ..mu..g/L). Aluminum concentrations present in citrus leaves (SRM 1572), pine needles (SRM 1575), and tomato leaves (SRM 1573) were 100 +- 12 (certified value, 92 +- 15), 522 +- 45 (certified value, 454 +- 30), and 1273 +- 112 (provisional value, 1200) ..mu..g/g, respectively. The within- and between-day precision had coefficients of variation for citrus leaves, pine needles, and tomato leaves of 18 and 12%, 6.3 and 8.6%, and 3.7 and 8.7%, respectively. Aluminum absorbance was enhanced at high pH values and by zinc.

  4. Measurement of the Spectral Absorption of Liquid Water in Melting Snow With an Imaging Spectrometer

    NASA Technical Reports Server (NTRS)

    Green, Robert O.; Dozier, Jeff

    1995-01-01

    Melting of the snowpack is a critical parameter that drives aspects of the hydrology in regions of the Earth where snow accumulates seasonally. New techniques for measurement of snow melt over regional scales offer the potential to improve monitoring and modeling of snow-driven hydrological processes. In this paper we present the results of measuring the spectral absorption of liquid water in a melting snowpack with the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS). AVIRIS data were acquired over Mammoth Mountain, in east central California on 21 May 1994 at 18:35 UTC. The air temperature at 2926 m on Mammoth Mountain at site A was measured at 15-minute intervals during the day preceding the AVIRIS data acquisition. At this elevation. the air temperature did not drop below freezing the night of the May 20 and had risen to 6 degrees Celsius by the time of the overflight on May 21. These temperature conditions support the presence of melting snow at the surface as the AVIRIS data were acquired.

  5. Measurement of the spectral absorption of liquid water in melting snow with an imaging spectrometer

    NASA Technical Reports Server (NTRS)

    Green, Robert O.; Dozier, Jeff

    1995-01-01

    Melting of the snowpack is a critical parameter that drives aspects of the hydrology in regions of the earth where snow accumulates seasonally. New techniques for measurement of snow melt over regional scales offer the potential to improve monitoring and modeling of snow-driven hydrological processes. We present the results of measuring the spectral absorption of liquid water in a melting snowpack with the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS). AVIRIS data were acquired over Mammoth Mountain, in east central California on 21 May 1994 at 18:35 UTC. The air temperature at 2926 m on Mammoth Mountain at site A was measured at 15-minute intervals during the day preceding the AVIRIS data acquisition. At this elevation, the air temperature did not drop below freezing the night of May 20 and had risen to 6 degrees Celsius by the time of the overflight on May 21. These temperature conditions support the presence of melting snow at the surface as the AVIRIS data were acquired.

  6. Comparison of atmospheric nitrous acid measurements by annular denuder and differential optical absorption systems

    NASA Astrophysics Data System (ADS)

    Appel, B. R.; Winer, A. M.; Tokiwa, Y.; Biermann, H. W.

    As part of the Southern California Air Quality Study (SCAQS), nitrous acid (HONO) measurements were made at Long Beach, CA during the period 11 November-12 December 1987, using two distinctly different techniqes. One of these, the annular denuder method (ADM), used two denuders in tandem, coated with an alkaline medium to obtain 4- or 6-h integrated measurements. A small FEP Tefloncoated glass cyclone preceded the denuders to exclude coarse particles while minimizing loss or artifactual formation of HONO. Nitrite recoveries from the rear denuder were used to correct for sampling artifacts. In the second method, 15 min average HONO concentrations were measured with a differential optical absorption spectrometer (DOAS) coupled to a 25 m basepath, open multiple reflection system operated at a total optical path of 800 m. Period-averaged HONO concentrations from the two techniques were highly correlated ( r = 0.94), with DOAS results averaging about 10% higher. However, ADM results were biased high at low HONO concentrations. HONO and NO concentrations showed a significant, positive correlation ( r = 0.8), consistent with a common emission source (e.g. auto exhaust) for the two pollutants.

  7. Wheatstone bridge technique for magnetostriction measurements.

    PubMed

    Sullivan, M

    1980-03-01

    A basic Wheatstone bridge, with additional electronic instrumentation, has been used in the measurement of magnetostriction. This method allows a resolution of approximately 10% on measurements of magnetostrictions less than 0.75 parts per million.

  8. Pulsed Lidar Measurements of Atmospheric CO2 Column Absorption in the ASCENDS 2011 Airborne Campaign

    NASA Technical Reports Server (NTRS)

    Abshire, James B.; Riris, Haris; Allan, Graham R.; Ramanathan, Anand; Hasselbrack, William E.; Mao, Jianping; Weaver, Clark; Browell, Edward V.

    2012-01-01

    We have previously demonstrated an efficient pulsed, wavelength-resolved IPDA lidar technique for measuring the tropospheric CO2 concentrations as a candidate for NASA's ASCENDS mission. Our team participated in the 2010 ASCENDS airborne campaigns we flew airborne version of the CO2 and O2 lidar on the NASA DC-8. The CO2 lidar measures the atmospheric backscatter profiles and shape of the 1572.33 nm absorption line using 250 mW average laser power, 30 wavelength samples per scan and 300 scans per second. Most flights had 5-6 altitude steps to greater than 12 km, and clear CO2 line shapes were observed at all altitudes. Our post-flight analysis estimated the Iidar range and pulse energies at each wavelength every second. We then solved for the best-fit CO2 absorption line shape, and calculated the Differential Optical Depth (DOD) at the line peak. We compared these to CO2 DODs calculated from spectroscopy based on HITRAN 2008 and the conditions from airborne in-situ readings. Analysis of the 2010 measurements over the Pacific Ocean and Lamont OK shows the expected -linear change of the peak DOD with altitude. For measurements at altitudes greater than 6 km the random errors were approximately 0.3 ppm for 80 sec averaging times. After the 2010 flights we improved the airborne lidar's scan uniformity, calibration and receiver sensitivity. Our team participated in the seven ASCENDS science flights during late July and August 2011. These flights were made over a wide variety of surface and cloud conditions near the US, including over the central valley of California, over several mountain ranges, over both broken and solid stratus cloud deck over the Pacific Ocean, snow patches on mountain tops, over thin and broken clouds above the US Southwest and Iowa, and over forests near the WLEF tower in Wisconsin. Analyses show the retrievals of lidar range and CO2 column absorption, as wen as estimates of CO2 mixing ratio worked well when measuring over topography with rapidly

  9. Pulsed Lidar Measurements of Atmospheric CO2 Column Absorption in the ASCENDS 2011 Airborne Campaign

    NASA Astrophysics Data System (ADS)

    Abshire, J. B.; Riris, H.; Allan, G. R.; Ramanathan, A.; Hasselbrack, W.; Mao, J.; Weaver, C. J.; Browell, E. V.

    2012-12-01

    We have previously demonstrated an efficient pulsed, wavelength-resolved IPDA lidar technique for measuring the tropospheric CO2 concentrations as a candidate for NASA's ASCENDS mission. Our team participated in the 2010 ASCENDS airborne campaigns we flew airborne version of the CO2 and O2 lidar on the NASA DC-8. The CO2 lidar measures the atmospheric backscatter profiles and shape of the 1572.33 nm absorption line using 250 mW average laser power, 30 wavelength samples per scan and 300 scans per second. Most flights had 5-6 altitude steps to > 12 km, and clear CO2 line shapes were observed at all altitudes. Our post-flight analysis estimated the lidar range and pulse energies at each wavelength every second. We then solved for the best-fit CO2 absorption line shape, and calculated the Differential Optical Depth (DOD) at the line peak. We compared these to CO2 DODs calculated from spectroscopy based on HITRAN 2008 and the conditions from airborne in-situ readings. Analysis of the 2010 measurements over the Pacific Ocean and Lamont OK shows the expected ~linear change of the peak DOD with altitude. For measurements at altitudes > 6 km the random errors were ~ 0.3 ppm for 80 sec averaging times. After the 2010 flights we improved the airborne lidar's scan uniformity, calibration and receiver sensitivity. Our team participated in the seven ASCENDS science flights during late July and August 2011. These flights were made over a wide variety of surface and cloud conditions near the US, including over the central valley of California, over several mountain ranges, over both broken and solid stratus cloud deck over the Pacific Ocean, snow patches on mountain tops, over thin and broken clouds above the US Southwest and Iowa, and over forests near the WLEF tower in Wisconsin. Analyses show the retrievals of lidar range and CO2 column absorption, as well as estimates of CO2 mixing ratio worked well when measuring over topography with rapidly changing height and reflectivity

  10. Method for measuring changes in light absorption of highly scattering media

    DOEpatents

    Bigio, Irving J.; Johnson, Tamara M.; Mourant, Judith R.

    2002-01-01

    The noninvasive measurement of variations in absorption that are due to changes in concentrations of biochemically relevant compounds in tissue is important in many clinical settings. One problem with such measurements is that the pathlength traveled by the collected light through the tissue depends on the scattering properties of the tissue. It is demonstrated, using both Monte Carlo simulations and experimental measurements, that for an appropriate separation between light-delivery and light-collection fibers, the pathlength of the collected photons is insensitive to scattering parameters for the range of parameters typically found in tissue. This is important for developing rapid, noninvasive, inexpensive, and accurate methods for measuring absorption changes in tissue.

  11. In Situ Measurements of Aerosol Mass Concentration and Spectral Absorption in Xianghe, SE of Beijing, China

    NASA Astrophysics Data System (ADS)

    Chaudhry, Z.; Martins, V.; Li, Z.

    2005-12-01

    China's rapid industrialization over the last few decades has affected air quality in many regions of China, and even the regional climate. As a part of the EAST-AIRE (East Asian Study of Tropospheric Aerosols: an International Regional Experiment) study, Nuclepore filters were collected in two size ranges (PM10 and PM2.5) at 12 hour intervals since January 2005 at Xianghe, about 70 km southeast of Beijing. Each filter was analyzed for mass concentration, aerosol scattering and absorption efficiencies. Mass concentrations during the winter months (January-March) ranged from 9 to 459 μg/m3 in the coarse mode with an average concentration of 122 μg/m3, and from 11 to 203 μg/m3 in the fine mode with an average concentration of 45 μg/m3. While some of the extreme values are likely linked to local emissions, regional air pollution episodes also played important roles. Absorption efficiency measurements at 550 nm show very high values compared to measurements performed in the United States during the CLAMS experiment. The spectral mass absorption efficiency was measured from 350 to 2500 nm and shows large differences between the absorption properties of soil dust, black carbon, and organic aerosols. The strong spectral differences observed can be related to differences in refractive indices from the several collected species and particle size effects. The absorption properties from aerosols measured in China show large absorption efficiencies, compared to aerosols measured in the US, possibly linked to different technology practices used in these countries. For organic plus black carbon aerosols, where the refractive index seems to be relatively constant, the absorption efficiency spectral dependence for fine mode aerosols falls between 1/λ and 1/λ2. The coarse mode absorption shows much less spectral dependence.

  12. Vibrational relaxation of the bending mode of shock-heated CO2 by laser-absorption measurements.

    NASA Technical Reports Server (NTRS)

    Eckstrom, D. J.; Bershader, D.

    1972-01-01

    Study of the vibrational relaxation characteristics of shock-heated CO2 using a tuned CO2 laser absorption technique. Absorption-coefficient histories were obtained for a single rotational state in each of the -10 0- and -02 0- levels over the temperature range from 500 to 2000 K, and for 21 rotational states of the -10 0- level at 1000 K. These histories have been combined with translational-rotational temperature histories based on interferometer measurements to calculate vibrational relaxation times for the bending mode. The results verify the mutual equilibrium of the bending and symmetric-stretch modes due to Fermi resonance. The bending mode relaxation times are approximately 10% shorter than predicted from interferometer results using the ratio of specific heats. Furthermore, relaxation times based on measurements of different rotational states at 1000 K show a variation with quantum number J, indicating a possible rotational nonequilibrium during the vibration relaxation process.

  13. The feasibility of water vapor sounding of the cloudy boundary layer using a differential absorption radar technique

    NASA Astrophysics Data System (ADS)

    Lebsock, M. D.; Suzuki, K.; Millan, L. F.; Kalmus, P. M.

    2015-06-01

    The feasibility of Differential Absorption Radar (DAR) for the spaceborne remote profiling of water vapor within the cloudy boundary layer is assessed by applying a radar instrument simulator to Large Eddy Simulations (LES). Frequencies near the 183 GHz water vapor absorption line attenuate too strongly to penetrate the large vapor concentrations that are ubiquitous in the boundary layer. However it is shown that lower frequencies between 140 and 170 GHz in the water vapor absorption continuum and on the wings of the absorption line, which are attenuated less efficiently than those near the line center, still have sufficient spectral variation of gaseous attenuation to perform sounding. The high resolution LES allow for assessment of the potential uncertainty in the method due to natural variability in thermodynamic and dynamic variables on scales smaller than the instrument field of view. The (160, 170) GHz frequency pair is suggested to best maximize signal for vapor profiling while minimizing noise due to undesired spectral variation in the target extinction properties. Precision in the derived water vapor is quantified as a function of the range resolution and the instrument precision. Assuming an observational spatial scale of 500 m vertical and 750 m Full Width at Half Maximum (FWHM) horizontal, measurement precision better that 1 g m-3 is achievable for stratocumulus scenes and 3 g m-3 for cumulus scenes given precision in radar reflectivity of 0.16 dBZ. Expected precision in the Column Water Vapor (CWV) is achievable between 0.5 and 2 kg m-2 on these same spatial scales. Sampling efficiency is quantified as a function of radar sensitivity. Mean biases in CWV due to natural variability in the target extinction properties do not exceed 0.25 kg m-2. Potential biases due to uncertainty in the temperature and pressure profile are negligible relative to those resulting from natural variability. Assuming a -35 dBZ minimum detectable signal, 40 % (21.9 %) of

  14. The feasibility of water vapor sounding of the cloudy boundary layer using a differential absorption radar technique

    NASA Astrophysics Data System (ADS)

    Lebsock, M. D.; Suzuki, K.; Millán, L. F.; Kalmus, P. M.

    2015-09-01

    The feasibility of differential absorption radar (DAR) for the spaceborne remote profiling of water vapor within the cloudy boundary layer is assessed by applying a radar instrument simulator to large eddy simulations (LES). Frequencies near the 183 GHz water vapor absorption line attenuate too strongly to penetrate the large vapor concentrations that are ubiquitous in the boundary layer. However it is shown that lower frequencies between 140 and 170 GHz in the water vapor absorption continuum and on the wings of the absorption line, which are attenuated less efficiently than those near the line center, still have sufficient spectral variation of gaseous attenuation to perform sounding. The high resolution LES allow for assessment of the potential uncertainty in the method due to natural variability in thermodynamic and dynamic variables on scales smaller than the instrument field of view. The (160, 170) GHz frequency pair is suggested to best maximize signal for vapor profiling while minimizing noise due to undesired spectral variation in the target extinction properties. Precision in the derived water vapor is quantified as a function of the range resolution and the instrument precision. Assuming an observational spatial scale of 500 m vertical and 750 m full width at half maximum (FWHM) horizontal, measurement precision better that 1 g m-3 is achievable for stratocumulus scenes and 3 g m-3 for cumulus scenes given precision in radar reflectivity of 0.16 dBZ. Expected precision in the column water vapor (CWV) is achievable between 0.5 and 2 kg m-2 on these same spatial scales. Sampling efficiency is quantified as a function of radar sensitivity. Mean biases in CWV due to natural variability in the target extinction properties do not exceed 0.25 kg m-2. Potential biases due to uncertainty in the temperature and pressure profile are negligible relative to those resulting from natural variability. Assuming a -35 dBZ minimum detectable signal, 40 %(21.9 %) of

  15. Saharan Dust: Particle Size Distributions and Light Absorption From Measurements During PRIDE and AEROCE

    NASA Astrophysics Data System (ADS)

    Savoie, D. L.; Maring, H. B.

    2001-12-01

    variability of the dust size distribution and the uncertainties associated with the sample analyses, we could not positively identify any significant differences between the size distributions at Izana and those at Puerto Rico for particle sizes less than about 6 or 7 um. Our measured dust size distributions at both locations show a broad peak that is flat topped from 3.5 to 8.5 um diameter. dV/dlogD decreases sharply above this range, but with a much gentler slope toward smaller particles. This size distribution is consistent with the TEOM total mass concentrations at both Puerto Rico and Izana. Mie estimates of the Saharan dust absorbance based on our measured size distributions and a previously reported dust refractive index yield a dust light absorption efficiency of 0.08 to 0.09 m2/g at 565 nm. Comparable Saharan dust specific absorbances at 565 nm were obtained from the diffuse reflectance technique for samples collected at Izana and Puerto Rico as well as at Barbados and Miami. Notably, the specific absorbance for dust derived from the PSAP measurements during PRIDE were more than a factor of two lower. In contrast, our previous results have shown that the PSAP and diffuse reflectance techniques yield nearly identical results for absorbing aerosols that are dominated by black, submicron particles, i.e. soot.

  16. Measuring Cognitive Ability with the Overclaiming Technique

    ERIC Educational Resources Information Center

    Paulhus, Delroy L.; Harms, P. D.

    2004-01-01

    The overclaiming technique requires respondents to rate their familiarity with a list of general knowledge items (persons, places, things). Because 20[percent] of the items are foils (i.e., do not exist), the response pattern can be analyzed with signal detection methods to yield the accuracy and bias scores for each respondent. In Study 1, the…

  17. WVR-GPS comparison measurements and calibration of the 20-32 GHz tropospheric water vapor absorption model.

    SciTech Connect

    Keihm, S. J.; Bar-Server, Y.; Liljegren, J. C.; Environmental Research; NASA

    2002-06-01

    Collocated measurements of opacity (from water vapor radiometer brightness temperatures) and wet path delay (from ground-based tracking of global positioning satellites) are used to constrain the model of atmospheric water vapor absorption in the 20-32 GHz band. A differential approach is presented in which the slope of opacity-versus-wet delay data is used as the absorption model constraint. This technique minimizes the effects of radiometric calibration errors and oxygen model uncertainties in the derivation of a best-fit vapor absorption model. A total of approximately five months of data was obtained from two experiment sites. At the Cloud and Radiation Testbed (CART) site near Lamont, Oklahoma, three independent water vapor radiometers (WVRs) provided near-continuous opacity measurements over the interval July-September 1998. At the NASA/Goldstone tracking station in the California desert two WVRs; obtained opacity data over the September-October 1997 interval. At both sites a Global Positioning Satellite (GPS) receiver and surface barometer obtained the data required for deriving the zenith wet delays over the same time frames. Measured values of the opacity-versus-wet delay slope parameter were obtained at four WVR frequencies (20.7, 22.2, 23.8, and 31.4 GHz) and compared with predictions of four candidate absorption models referenced in the literature. With one exception, all three models provide agreement within 5% of the opacity-versus-wet delay slope measurements at all WVR frequencies at both sites. One model provides agreement for all channels at both sites to the 2-3% level. This absorption model accuracy level represents a significant improvement over that attainable using radiosondes.

  18. Differential Absorption Measurements of Carbon Dioxide for Carbon Sequestration Site Monitoring Using a Temperature Tunable Diode Laser

    NASA Astrophysics Data System (ADS)

    Humphries, S. D.; Nehrir, A. R.; Repasky, K. S.; Carlsten, J. L.; Spangler, L. H.; Dobeck, L. M.; Shaw, J. A.

    2007-12-01

    Carbon capture and sequestration in geologic formations provides a method to remove carbon dioxide (CO2) from entering the Earth's atmosphere. An important issue for the successful storage of CO2 is the ability to monitor geologic sequestration sites for leakage to verify site integrity. A differential absorption measurement instrument based on a continuous wave (cw) temperature tunable distributed feedback (DFB) laser has been developed for measuring atmospheric concentrations of CO2. The tunable DFB laser is capable of tuning across two CO2 absorption features at 2003.50 nm and 2004.02 nm. The measured normalized transmission through the atmosphere is then related to the atmospheric concentration of CO2 through the line strength and normalized line width associated with each absorption feature. A description of this instrument will be presented including the instrument design, operation, and performance characteristics. A field site for testing the performance of CO2 detection instruments and techniques has been developed by the Zero Emissions Research Technology (ZERT) group at Montana State University. The field site allows a controlled flow rate of CO2 to be released underground through a 100 m long horizontal pipe placed below the water table. Two release experiments were performed this past summer with flow rates of 0.1 and 0.3 tons CO2/day. The first release experiment lasted ten days while the second release lasted seven days. Measurements taken with the differential absorption instrument over the horizontal well during these release experiments showed an increase of greater than 300 parts per million (ppm) over the background CO2 concentration. These results indicate the capabilities of the above ground differential absorption instrument for carbon sequestration site monitoring.

  19. [Gas Concentration Measurement Based on the Integral Value of Absorptance Spectrum].

    PubMed

    Liu, Hui-jun; Tao, Shao-hua; Yang, Bing-chu; Deng, Hong-gui

    2015-12-01

    The absorptance spectrum of a gas is the basis for the qualitative and quantitative analysis of the gas by the law of the Lambert-Beer. The integral value of the absorptance spectrum is an important parameter to describe the characteristics of the gas absorption. Based on the measured absorptance spectrum of a gas, we collected the required data from the database of HIT-RAN, and chose one of the spectral lines and calculated the integral value of the absorptance spectrum in the frequency domain, and then substituted the integral value into Lambert-Beer's law to obtain the concentration of the detected gas. By calculating the integral value of the absorptance spectrum we can avoid the more complicated calculation of the spectral line function and a series of standard gases for calibration, so the gas concentration measurement will be simpler and faster. We studied the changing trends of the integral values of the absorptance spectrums versus temperature. Since temperature variation would cause the corresponding variation in pressure, we studied the changing trends of the integral values of the absorptance spectrums versus both the pressure not changed with temperature and changed with the temperature variation. Based on the two cases, we found that the integral values of the absorptance spectrums both would firstly increase, then decrease, and finally stabilize with temperature increasing, but the ranges of specific changing trend were different in the two cases. In the experiments, we found that the relative errors of the integrated values of the absorptance spectrum were much higher than 1% and still increased with temperature when we only considered the change of temperature and completely ignored the pressure affected by the temperature variation, and the relative errors of the integrated values of the absorptance spectrum were almost constant at about only 1% when we considered that the pressure were affected by the temperature variation. As the integral value

  20. Dynamics of laser-driven proton acceleration exhibited by measured laser absorptivity and reflectivity

    PubMed Central

    Bin, J. H.; Allinger, K.; Khrennikov, K.; Karsch, S.; Bolton, P. R.; Schreiber, J.

    2017-01-01

    Proton acceleration from nanometer thin foils with intense laser pulses is investigated experimentally. We analyzed the laser absorptivity by parallel monitoring of laser transmissivity and reflectivity with different laser intensities when moving the targets along the laser axis. A direct correlation between laser absorptivity and maximum proton energy is observed. Experimental results are interpreted in analytical estimation, exhibiting a coexistence of plasma expansion and light-sail form of radiation pressure acceleration (RPA-LS) mechanisms during the entire proton acceleration process based on the measured laser absorptivity and reflectivity. PMID:28272471

  1. Deriving brown carbon from multiwavelength absorption measurements: Method and application to AERONET and Aethalometer observations

    SciTech Connect

    Wang, X.; Heald, C. L.; Sedlacek, A.; de Sa, S. S.; Martin, S. T.; Alexander, M. L.; Watson, T. B.; Aiken, A. C.; Springston, S. R.; Artaxo, P.

    2016-10-13

    The radiative impact of organic aerosols (OA) is a large source of uncertainty in estimating the global direct radiative effect (DRE) of aerosols. This radiative impact includes not only light scattering but also light absorption from a subclass of OA referred to as brown carbon (BrC). However the absorption properties of BrC are poorly understood leading to large uncertainties in modelling studies. To obtain observational constraints from measurements, a simple Absorption Ångström Exponent (AAE) method is often used to separate the contribution of BrC absorption from that of black carbon (BC). However, this attribution method is based on assumptions regarding the spectral dependence of BC that are often violated in the ambient atmosphere. Here we develop a new method that decreases the uncertainties associated with estimating BrC absorption. By applying this method to multi-wavelength absorption aerosol optical depth (AAOD) measurements at AERONET sites worldwide and surface aerosol absorption measurements at multiple ambient sites, we estimate that BrC globally contributes 6-40% of the absorption at 440nm. We find that the mass absorption coefficient of OA (OA-MAC) is positively correlated with BC/OA mass ratio. Based on the variability of BC properties and BC/OA emission ratio, we estimate a range of 0.05-1.2 m2/g for OA-MAC at 440nm. Using the combination of AERONET and OMI UV absorption observations we estimate that the AAE388/440nm for BrC is generally ~4 world-wide, with a smaller value in Europe (< 2). Our analyses of two surface sites (Cape Cod, to the southeast of Boston, and the GoAmazon2014/5 T3 site, to the west of Manaus, Brazil) reveal no significant relationship between BrC absorptivity and photochemical aging in typical urban influenced conditions. However, the absorption of BrC measured during the biomass burning season near Manaus is found to decrease with photochemical aging with a lifetime of ~1 day. This lifetime is

  2. Deriving brown carbon from multiwavelength absorption measurements: Method and application to AERONET and Aethalometer observations

    DOE PAGES

    Wang, X.; Heald, C. L.; Sedlacek, A.; ...

    2016-10-13

    The radiative impact of organic aerosols (OA) is a large source of uncertainty in estimating the global direct radiative effect (DRE) of aerosols. This radiative impact includes not only light scattering but also light absorption from a subclass of OA referred to as brown carbon (BrC). However the absorption properties of BrC are poorly understood leading to large uncertainties in modelling studies. To obtain observational constraints from measurements, a simple Absorption Ångström Exponent (AAE) method is often used to separate the contribution of BrC absorption from that of black carbon (BC). However, this attribution method is based on assumptions regardingmore » the spectral dependence of BC that are often violated in the ambient atmosphere. Here we develop a new method that decreases the uncertainties associated with estimating BrC absorption. By applying this method to multi-wavelength absorption aerosol optical depth (AAOD) measurements at AERONET sites worldwide and surface aerosol absorption measurements at multiple ambient sites, we estimate that BrC globally contributes 6-40% of the absorption at 440nm. We find that the mass absorption coefficient of OA (OA-MAC) is positively correlated with BC/OA mass ratio. Based on the variability of BC properties and BC/OA emission ratio, we estimate a range of 0.05-1.2 m2/g for OA-MAC at 440nm. Using the combination of AERONET and OMI UV absorption observations we estimate that the AAE388/440nm for BrC is generally ~4 world-wide, with a smaller value in Europe (< 2). Our analyses of two surface sites (Cape Cod, to the southeast of Boston, and the GoAmazon2014/5 T3 site, to the west of Manaus, Brazil) reveal no significant relationship between BrC absorptivity and photochemical aging in typical urban influenced conditions. However, the absorption of BrC measured during the biomass burning season near Manaus is found to decrease with photochemical aging with a lifetime of ~1 day. This lifetime is comparable to

  3. Dynamics of laser-driven proton acceleration exhibited by measured laser absorptivity and reflectivity

    NASA Astrophysics Data System (ADS)

    Bin, J. H.; Allinger, K.; Khrennikov, K.; Karsch, S.; Bolton, P. R.; Schreiber, J.

    2017-03-01

    Proton acceleration from nanometer thin foils with intense laser pulses is investigated experimentally. We analyzed the laser absorptivity by parallel monitoring of laser transmissivity and reflectivity with different laser intensities when moving the targets along the laser axis. A direct correlation between laser absorptivity and maximum proton energy is observed. Experimental results are interpreted in analytical estimation, exhibiting a coexistence of plasma expansion and light-sail form of radiation pressure acceleration (RPA-LS) mechanisms during the entire proton acceleration process based on the measured laser absorptivity and reflectivity.

  4. Optoacoustic measurements of water vapor absorption at selected CO laser wavelengths in the 5-micron region

    NASA Technical Reports Server (NTRS)

    Menzies, R. T.; Shumate, M. S.

    1976-01-01

    Measurements of water vapor absorption were taken with a resonant optoacoustical detector (cylindrical pyrex detector, two BaF2 windows fitted into end plates at slight tilt to suppress Fabry-Perot resonances), for lack of confidence in existing spectral tabular data for the 5-7 micron region, as line shapes in the wing regions of water vapor lines are difficult to characterize. The measurements are required for air pollution studies using a CO laser, to find the differential absorption at the wavelengths in question due to atmospheric constituents other than water vapor. The design and performance of the optoacoustical detector are presented. Effects of absorption by ambient NO are considered, and the fixed-frequency discretely tunable CO laser is found suitable for monitoring urban NO concentrations in a fairly dry climate, using the water vapor absorption data obtained in the study.

  5. Measurements of Cs absorption and retention in man

    SciTech Connect

    Henrichs, H.; Paretzke, H.G.; Voigt, G.; Berg, D. )

    1989-10-01

    One of the consequences of the Chernobyl reactor accident in 1986 was a comparatively high contamination of foodstuffs in Southern Federal Republic of Germany. In order to test radioecological models predicting the radiological consequences of such accidents, several thousand measurements were performed to determine Cs body burdens in members of the public. For the interpretation of these data and as a contribution to the improvement of the available database on the biokinetics of Cs isotopes in humans, we followed a small group of volunteers after their consumption of highly contaminated venison. Intakes, excretion rates and total body activities were measured during a period of more than 200 d. The data obtained were evaluated in terms of a compartment model to derive gastrointestinal uptakes, biological half-lives and dose conversion factors. The resulting uptake factors range from 65-90%, the half-lives of the long-term retention from 45 to 200 d. The majority of the resulting dose conversion factors lie below the values recommended by the ICRP, showing that the ICRP model is a reasonable and safe description of the Cs biokinetics in our study group, while the great variability of the results shows that it is not an accurate representation of the individual Cs retention.

  6. Broadband spectroscopy with external cavity quantum cascade lasers beyond conventional absorption measurements.

    PubMed

    Lambrecht, Armin; Pfeifer, Marcel; Konz, Werner; Herbst, Johannes; Axtmann, Felix

    2014-05-07

    Laser spectroscopy is a powerful tool for analyzing small molecules, i.e. in the gas phase. In the mid-infrared spectral region quantum cascade lasers (QCLs) have been established as the most frequently used laser radiation source. Spectroscopy of larger molecules in the gas phase, of complex mixtures, and analysis in the liquid phase requires a broader tuning range and is thus still the domain of Fourier transform infrared (FTIR) spectroscopy. However, the development of tunable external cavity (EC) QCLs is starting to change this situation. The main advantage of QCLs is their high spectral emission power that is enhanced by a factor of 10(4) compared with thermal light sources. Obviously, transmission measurements with EC-QCLs in strongly absorbing samples are feasible, which can hardly be measured by FTIR due to detector noise limitations. We show that the high power of EC-QCLs facilitates spectroscopy beyond simple absorption measurements. Starting from QCL experiments with liquid samples, we show results of fiber evanescent field analysis (FEFA) to detect pesticides in drinking water. FEFA is a special case of attenuated total reflection spectroscopy. Furthermore, powerful CW EC-QCLs enable fast vibrational circular dichroism (VCD) spectroscopy of chiral molecules in the liquid phase - a technique which is very time consuming with standard FTIR equipment. We present results obtained for the chiral compound 1,1'-bi-2-naphthol (BINOL). Finally, powerful CW EC-QCLs enable the application of laser photothermal emission spectroscopy (LPTES). We demonstrate this for a narrowband and broadband absorber in the gas phase. All three techniques have great potential for MIR process analytical applications.

  7. Absorption edge subtraction imaging for volumetric measurement in an animal model of malignant brain tumor

    NASA Astrophysics Data System (ADS)

    Rigley, S.; Rigon, L.; Ataelmannan, K.; Chapman, D.; Doucette, R.; Griebel, R.; Juurlink, B.; Arfelli, F.; Menk, R.-H.; Tromba, G.; Barroso, R. C.; Beveridge, T.; Lewis, R.; Pavlov, K.; Siu, K.; Hall, C.; Schültke, E.

    2005-08-01

    The goal of this project is to determine the feasibility of utilizing colloidal gold as a marker for C6 glioblastoma cells implanted into rat brain as an appropriate model for volumetric measurements of tumors using absorption edge subtraction (AES). Phase sensitive X-ray imaging is combined with KES to give good soft tissue contrast. Current methods for volumetric measurements of implanted C6 glioblastoma tumors in rat brains using MRI technology are inadequate due to the small size of the tumor (2.5-4 mm in diameter) and the thickness of the MRI slice (1-1.5 mm). Previously, our group has shown that AES detection of colloidal gold labeled C6 glioblastoma cells implanted into a rat brains may be feasible. The long-term goal for this project is to establish a method, which would allow the researcher to monitor the development of a tumor over time. Most importantly, this technique should allow researchers to accurately determine the potency of a treatment on the size and growth rate for a C6 implanted tumors. In addition, we plan to challenge the hypothesis that tumors of the glioma type do not metastasize outside of the brain. A sensitive technique for the detection of C6 cells, such as that using colloidal gold and AES/DEI, should enable researchers to detect C6 cells, which have metastasized and migrated to different areas of the body. The ability to detect implanted C6 cells followed by the development of the tumor, the possible migration of the cells and the ability to accurately measure the effects of treatments on the volume of the tumor would be of the utmost importance to brain tumor research.

  8. A simple technique for individual picosecond laser pulse duration measurements

    NASA Technical Reports Server (NTRS)

    Smith, W. L.; Bechtel, J. H.

    1976-01-01

    We describe here a simple nonlinear optic technique for the measurement of the duration of individual picosecond pulses. The accuracy and relative simplicity of the technique increase with the number of pulses measured. An experimental test of the basis of the technique is described.

  9. A Wireless Fluid-Level Measurement Technique

    NASA Technical Reports Server (NTRS)

    Woodard, Stanley E.; Taylor, Bryant D.

    2006-01-01

    This paper presents the application of a recently developed wireless measurement acquisition system to fluid-level measurement. This type of fluid-level measurement system alleviates many shortcomings of fluid-level measurement methods currently being used, including limited applicability of any one fluid-level sensor design. Measurement acquisition shortcomings include the necessity for power to be supplied to each sensor and for the measurement to be extracted from each sensor via a physical connection to the sensor. Another shortcoming is existing measurement systems require that a data channel and signal conditioning electronics be dedicated to each sensor. Use of wires results in other shortcomings such as logistics needed to add or replace sensors, weight, potential for electrical arcing and wire degradations. The fluid level sensor design is a simple passive inductor-capacitor circuit that is not subject to mechanical failure that is possible when float and lever-arm systems are used. Methods are presented for using the sensor in caustic, acidic or cryogenic fluids. Oscillating magnetic fields are used to power the sensor. Once electrically excited, the sensor produces a magnetic field response. The response frequency corresponds to the amount to fluid within the capacitor s electric field. The sensor design can be modified for measuring the level of any fluid or fluent substance that can be stored in a non-conductive reservoir. The interrogation method for discerning changes in the sensor response frequency is also presented.

  10. A Simple Technique for High Resistance Measurement

    ERIC Educational Resources Information Center

    Aguilar, Horacio Munguia; Landin, Ramon Ochoa

    2012-01-01

    A simple electronic system for the measurement of high values of resistance is shown. This system allows the measurement of resistance in the range of a few megohm up to 10[superscript 9] [omega]. We have used this system for the evaluation of CdS thin film resistance, but other practical uses in the basic physics laboratory are presented.…

  11. Time-domain flicker measurement technique

    NASA Astrophysics Data System (ADS)

    Miseli, Joseph

    1999-04-01

    The visibility of flicker on a display depends upon many factors, including the observer's sensitivity to flicker. Whenever flicker is observed, it is probably undesirable and often unacceptable. Much has been written about flicker, its perception, and its variability. Methods have been presented to the industry that use frequency domain analysis of measured flicker response. Here we prose an alternate method to quantify flicker in the time domain, just as people see it, and we will try to understand how the measurements relate to what people see. Both the frequency domain and time domain flicker measurements can be found in the Video Electronics Standards Association Flat Panel Display Measurements Standard. An attempt is made to compare the two methods and show how the simpler measurement can be employed for many display technologies.

  12. Effect of Water Vapor Absorption on Measurements of Atmospheric Nitrate Radical by LP-DOAS

    NASA Astrophysics Data System (ADS)

    Li, Su-wen; Liu, Wen-qing; Xie, Pin-hua; Yang, Yi-jun; Chen, De-bao; Li, Zheng

    2008-10-01

    During the measurement of atmospheric nitrate radical by long-path differential optical absorption spec-troscopy, water vapor strong absorption could affect the measurement of nitrate radical and detection limits of system. Under the tropospheric condition, the optical density of water vapor absorption is non-linearly dependent on column density. An effective method was developed to eliminate the effect of water vapor absorption. Reference spectra of water vapor based on the daytime atmospheric absorption spectra, when fitted together with change of cross section with water vapor column densities, gave a more accurate fitting of water vapor absorptions, thus its effect on the measurements of nitrate radical could be restricted to a minimum and detection limits of system reached 3.6 ppt. The modified method was applied during an intensive field campaign in the Pearl River Delta, China. The NO3 concentration in polluted air masses varied from 3.6 ppt to 82.5 ppt with an average level of 23.6±1.8 ppt.

  13. Development of techniques for measuring pilot workload

    NASA Technical Reports Server (NTRS)

    Spyker, D. A.; Stackhouse, S. P.; Khalafalla, A. S.; Mclane, R. C.

    1971-01-01

    An objective method of assessing information workload based on physiological measurements was developed. Information workload, or reserve capacity, was measured using a visual discrimination secondary task and subjective rating of task difficulty. The primary task was two axis (pitch and roll) tracking, and the independent variables in this study were aircraft pitch dynamics and wind gust disturbances. The study was structured to provide: (1) a sensitive, nonloading measure of reserve capacity, and (2) an unencumbering reliable measurement of the psychophysiological state. From these, a measured workload index (MWI) and physiological workload index (PWI) were extracted. An important measure of the success of this study was the degree to which the MWI and PWI agreed across the 243 randomly-presented, four-minute trials (9 subjects X 9 tasks X 3 replications). The electrophysiological data collected included vectorcardiogaram, respiration, electromyogram, skin impedance, and electroencephalogram. Special computer programs were created for the analysis of each physiological variable. The digital data base then consisted of 82 physiological features for each of the 243 trials. A prediction of workload based on physiological observations was formulated as a simultaneous least-squares prediction problem. A best subset of 10 features was chosen to predict the three measures of reserve capacity. The cannonical correlation coefficient was .754 with a chi squared value of 91.3 which allows rejection of the null hypothesis with p of .995.

  14. Shock-Tube Measurement of Acetone Dissociation Using Cavity-Enhanced Absorption Spectroscopy of CO.

    PubMed

    Wang, Shengkai; Sun, Kai; Davidson, David F; Jeffries, Jay B; Hanson, Ronald K

    2015-07-16

    A direct measurement for the rate constant of the acetone dissociation reaction (CH3COCH3 = CH3CO + CH3) was conducted behind reflected shock wave, utilizing a sub-ppm sensitivity CO diagnostic achieved by cavity-enhanced absorption spectroscopy (CEAS). The current experiment eliminated the influence from secondary reactions and temperature change by investigating the clean pyrolysis of <20 ppm acetone in argon. For the first time, the acetone dissociation rate constant (k1) was directly measured over 5.5 orders of magnitude with a high degree of accuracy: k1 (1004-1494 K, 1.6 atm) = 4.39 × 10(55) T(-11.394) exp(-52 140K/T) ± 24% s(-1). This result was seen to agree with most previous studies and has bridged the gap between their temperature and pressure conditions. The current work also served as an example demonstration of the potential of using the CEAS technique in shock-tube kinetics studies.

  15. Excitation ahead of shock fronts in krypton measured by single line laser absorption

    NASA Astrophysics Data System (ADS)

    Boetticher, W.; Kilpin, D.

    1984-12-01

    The absorption of single-mode radiation (from a dye laser tuned to 587.25 and 557.18 nm) by Kr in front of shock waves with Mach numbers 12-21 in a 50-mm-diameter 4.4-m-long free-position driver shock tube at preshock pressures 0.7-2.7 kPa is measured to determine the number densities of the metastable 5s(1 1/2)2 and 5s(1 1/2)1 precursor states (1s5 and 1s4 in Paschen notation, respectively). The measurement technique and calculations follow those of Ernst (1982). The results are presented in tables and graphs and characterized in comparison with previous findings. The time constant of the exponential rise of the precursor is found to be about 8 microsec, and the concentration of 1s5 + 1s4 for Mach 20 is calculated as about 10 ppm, in agreement (to within a factor of 5) with model predictions for Ar and Xe.

  16. Technique for measuring gas conversion factors

    NASA Technical Reports Server (NTRS)

    Singh, J. J.; Sprinkle, D. R. (Inventor)

    1985-01-01

    A method for determining hydrocarbon conversion factors for a flowmeter. A mixture of air, O2 and C sub x H sub y is burned and the partial paressure of O2 in the resulting gas is forced to equal the partial pressure of O2 in air. The flowrate of O2 flowing into the mixture is measured by flowmeter and the flowrate of C sub x H sub y flowing into the mixture is measured by the flowmeter conversion factor is to be determined. These measured values are used to calculate the conversion factor.

  17. New technique for oil backstreaming contamination measurements

    NASA Technical Reports Server (NTRS)

    Alterovitz, S. A.; Speier, H. J.; Sieg, R. M.; Drotos, M. N.; Dunning, J. E.

    1992-01-01

    The backstreaming contamination in the Space Power Facility, Ohio, was measured using small size clean silicon wafers as contamination sensors placed at all measurement sites. Two ellipsometric models were developed to measure the oil film with the contamination film refractive index of DC 705: a continuous, homogeneous film and islands of oil with the islands varying in coverage fraction and height. The island model improved the ellipsometric analysis quality parameter by up to two orders of magnitude. The continuous film model overestimated the oil volume by about 50 percent.

  18. Apparatus and techniques for measuring bedload

    USGS Publications Warehouse

    Hubbell, David Wellington

    1964-01-01

    The need for accurate determinations of the total sediment discharge of particles of bedload size has prompted this investigation of available and possible measuring apparatus and procedures. The accuracy of measurements of sediment discharge made with trap-type samplers is affected by the variability of sampler efficiency, by the oscillatory variation of bedload discharge, and by sampler placement. Equations that were developed for determining total discharge from measured bedioad discharge and measured suspended-sediment discharge are simplest if the bedload apparatus measures only the true bedload. Early bedload samplers are generally unsatisfactory. Recently developed or suggested apparatus include various improved samplers of the pressure-difference type, a pumping sampler, a magnetic sampler, acoustical instruments that measure the magnitude of the sound of particle collisions, an ultrasonic bedload sampler designed to measure and integrate electronically the concentration and velocity, and a tiltmeter designed to measure the total sediment discharge from the ground tilt that results from the passage of flow. All the pressure-difference samplers are improvements over early samplers, but none are void of the inherent shortcomings of trap-type apparatus; probably the Sphinx (Dutch) and VUV (Hungarian) samplers are the most satisfactory. The acoustical instruments are capable of measuring only the relative discharge. The ultrasonic sampler and the tiltmeter are not adequate without further development. Some new possible apparatus and means for measuring or aiding in measuring bedload discharge are small pit samplers, ultrasonic sounders, pressure transducers, and photography. A small pit sampler for measuring bedload discharge was designed to provide self-placement and portability ; however, its practicability and efficiency are undetermined. Exploratory films show that by using slowmotion photography the discharge of particles larger than about pea size can be

  19. Analysis of Pulsed Lidar Measurements of Atmospheric CO2 Column Absorption During the ASCENDS 2009-2011 Airborne Campaigns

    NASA Technical Reports Server (NTRS)

    Abshire, J. B.; Weaver, C. J.; Riris, H.; Mao, J.; Sun, X; Allan, G. R.; Hasselbrack, W. E.; Browell, E. V.

    2012-01-01

    We have developed a pulsed lidar technique for measuring the tropospheric CO2 concentrations as a candidate for NASA's ASCENDS mission and have demonstrated the CO2 and O2 measurements from aircraft. Our technique uses two pulsed lasers allowing simultaneous measurement of a single CO2 absorption line near 1572 nm, O2 extinction in the Oxygen A-band, surface height and backscatter profile. The lasers are stepped in wavelength across the CO2 line and an O2 line doublet during the measurement. The column densities for the CO2 and O2 are estimated from the differential optical depths (DOD) of the scanned absorption lines via the IPDA technique. For the 2009 ASCENDS campaign we flew the CO2 lidar on a Lear-25 aircraft, and measured the absorption line shapes of the CO2 line using 20 wavelength samples per scan. Measurements were made at stepped altitudes from 3 to 12.6 km over the Lamont OK, central Illinois, North Carolina, and over the Virginia Eastern Shore. Although the received signal energies were weaker than expected for ASCENDS, clear CO2 line shapes were observed at all altitudes. Most flights had 5-6 altitude steps with 200-300 seconds of recorded measurements per step. We averaged every 10 seconds of measurements and used a cross-correlation approach to estimate the range to the scattering surface and the echo pulse energy at each wavelength. We then solved for the best-fit CO2 absorption line shape, and calculated the DOD of the fitted CO2 line, and computed its statistics at the various altitude steps. We compared them to CO2 optical depths calculated from spectroscopy based on HITRAN 2008 and the column number densities calculated from the airborne in-situ readings. The 2009 measurements have been analyzed and they were similar on all flights. The results show clear CO2 line shape and absorption signals, which follow the expected changes with aircraft altitude from 3 to 13 km. They showed the expected nearly the linear dependence of DOD vs altitude. The

  20. [Development of a photoacoustic spectroscopy system for the measurement of absorption coefficient of atmospheric aerosols].

    PubMed

    Liu, Qiang; Niu, Ming-Sheng; Wang, Gui-Shi; Cao, Zhen-Song; Liu, Kun; Chen, Wei-Dong; Gao, Xiao-Ming

    2013-07-01

    In the present paper, the authors focus on the effect of the resonance frequency shift due to the changes in temperature and humidity on the PA signal, present several methods to control the noise derived form gas flow and vibration from the sampling pump. Based on the efforts mentioned above, a detection limit of 1.4 x 10(-8) W x cm(-1) x Hz(-1/2) was achieved for the measurement of atmospheric aerosols absorption coefficient. During the experiments, the PA cell was calibrated with the absorption of standard NO2 gas at 532 nm and the atmospheric aerosols were measured continuously. The measurement results show that the PAS is suitable for the real-time measurement of the absorption coefficient of atmospheric aerosols in their natural suspended state.

  1. Vacuum Ultraviolet Absorption Measurements of Atomic Oxygen in a Shock Tube

    NASA Technical Reports Server (NTRS)

    Meyer, Scott Andrew

    1995-01-01

    The absorption of vacuum ultraviolet light by atomic oxygen has been measured in the Electric Arc-driven Shock Tube (EAST) Facility at NASA-Ames Research Center. This investigation demonstrates the instrumentation required to determine atomic oxygen concentrations from absorption measurements in impulse facilities. A shock wave dissociates molecular oxygen, producing a high temperature sample of atomic oxygen in the shock tube. A probe beam is generated with a Raman-shifted ArF excimer laser. By suitable tuning of the laser, absorption is measured over a range of wavelengths in the region of the atomic line at 130.49 nm. The line shape function is determined from measurements at atomic oxygen densities of 3x10(exp 17) and 9x10(exp 17) cm(exp -3). The broadening coefficient for resonance interactions is deduced from this data, and this value is in accord with available theoretical models.

  2. Vacuum Ultraviolet Absorption Measurements of Atomic Oxygen in a Shock Tube

    NASA Technical Reports Server (NTRS)

    Meyer, Scott Andrew

    1995-01-01

    The absorption of vacuum ultraviolet light by atomic oxygen has been measured in the Electric Arc-driven Shock Tube (EAST) Facility at NASA-Ames Research Center. This investigation demonstrates the instrumentation required to determine atomic oxygen concentrations from absorption measurements in impulse facilities. A shock wave dissociates molecular oxygen, producing a high temperature sample of atomic oxygen in the shock tube. A probe beam is generated with a Raman-shifted ArF excimer laser. By suitable tuning of the laser, absorption is measured over a range of wavelengths in the region of the atomic line at 130.49 nm. The line shape function is determined from measurements at atomic oxygen densities of 3 x 10(exp 17) and 9 x 10(exp 17) cm(exp -3). The broadening coefficient for resonance interactions is deduced from this data, and this value is in accord with available theoretical models.

  3. Vacuum Ultraviolet Absorption Measurements of Atomic Oxygen in a Shock Tube

    NASA Technical Reports Server (NTRS)

    Meyer, Scott Andrew

    1995-01-01

    The absorption of vacuum ultraviolet light by atomic oxygen has been measured in the Electric Arc-driven Shock Tube (EAST) Facility at NASA-Ames Research Center. This investigation demonstrates the instrumentation required to determine atomic oxygen concentrations from absorption measurements in impulse facilities. A shock wave dissociates molecular oxygen, producing a high temperature sample of atomic oxygen in the shock tube. A probe beam is generated with a Raman-shifted ArF excimer laser. By suitable tuning of the laser, absorption is measured over a range of wavelengths in the region of the atomic line at 130.49 nm. The line shape function is determined from measurements at atomic oxygen densities of 3 x 10(exp 17) and 9 x 10(exp 17)/cu cm. The broadening coefficient for resonance interactions is deduced from this data, and this value is in accord with available theoretical models.

  4. An indoor test campaign of the tomography long path differential optical absorption spectroscopy technique.

    PubMed

    Mettendorf, K U; Hartl, A; Pundt, I

    2006-02-01

    In this study we validate the two-dimensional long path DOAS tomography measurement technique by means of an indoor experiment with well-known concentration distributions. The experiment was conducted over an area of 10 m x 15 m using one and two cylindrical polycarbonate containers of diameter 2 m, respectively, filled with NO2. The setup was realized with three of the multibeam instruments recently developed by Pundt and Mettendorf (Appl. Opt., 2005, in press), which allow the simultaneous measurement along at least four light paths each. The configuration consisted of twelve simultaneous light beams, 39 horizontal light paths in total, and 18 different cylinder positions inside the field. It was found that for the discretization and inversion technique shown here reconstructions of the concentration distributions from experimental data agree well with simulated reconstructions. In order to draw conclusions for atmospheric applications, numerical studies including instrumental errors were carried out. It was found that with the presented measurement setup it is possible to measure and reconstruct one or two NO2 plumes of 600 m diameter and average concentrations above 4.2 ppbv each, on a scale of 13.5 km2. Theoretical investigations show that it should be possible to localize and quantify 600 m diameter plumes of SO2 > 1.5 ppbv, H2CO > 6.3 ppbv, HONO > 3.2 ppbv, and ozone > 46.2 ppbv. Larger plumes can be measured with higher precision.

  5. A Plutonium Storage Container Pressure Measurement Technique

    SciTech Connect

    Grim, T.J.

    2002-05-10

    Plutonium oxide and metal awaiting final disposition are currently stored at the Savannah River Site in crimp sealed food pack cans. Surveillances to ensure continued safe storage of the cans include periodic lid deflection measurements using a mechanical device.

  6. Effect of nonlinear absorption on electric field applied lead chloride by Z-scan technique

    SciTech Connect

    Rejeena, I.; Lillibai,; Nampoori, V. P. N.; Radhakrishnan, P.; Rahimkutty, M. H.

    2014-10-15

    The preparation, spectral response and optical nonlinearity of gel grown lead chloride single crystals subjected to electric field of 20V using parallel plate arrangements have been investigated. Optical band gap of the samples were determined using linear absorption spectra. Open aperture z-scan was employed for the determination of nonlinear absorption coefficient of PbCl{sub 2} solution. The normalized transmittance curve exhibits a valley shows reverse saturable absorption. The non linear absorption at different input fluences were recorded using a single Gaussian laser beam in tight focus geometry. The RSA nature of the sample makes it suitable for optical limiting applications.

  7. Pulsed Lidar Measurements of Atmospheric CO2 Column Absorption and Range During the ASCENDS 2009-2011 Airborne Campaigns

    NASA Technical Reports Server (NTRS)

    Abshire, J. B.; Weaver, C. J.; Riris, H.; Mao, J.; Sun, X.; Allan, G. R.; Hasselbrack, W. E.; Browell, E. V.

    2012-01-01

    We have developed a pulsed lidar technique for measuring the tropospheric CO2 concentrations as a candidate for NASA's ASCENDS mission and have demonstrated the CO2 and O2 measurements from aircraft. Our technique uses two pulsed lasers allowing simultaneous measurement of a single CO2 absorption line near 1572 nm, O2 extinction in the Oxygen A-band, surface height and backscatter profile. The lasers are stepped in wavelength across the CO2 line and an O2 line doublet during the measurement. The column densities for the CO2 and O2 are estimated from the differential optical depths (DOD) of the scanned absorption lines via the IPDA technique. For the 2009 ASCENDS campaign we flew the CO2 lidar only on a Lear-25 aircraft, and measured the absorption line shapes of the CO2 line using 20 wavelength samples per scan. Measurements were made at stepped altitudes from 3 to 12.6 km over the Lamont OK, central Illinois, North Carolina, and over the Virginia Eastern Shore. Although the received signal energies were weaker than expected for ASCENDS, clear C02 line shapes were observed at all altitudes. Most flights had 5-6 altitude steps with 200-300 seconds of recorded measurements per step. We averaged every 10 seconds of measurements and used a cross-correlation approach to estimate the range to the scattering surface and the echo pulse energy at each wavelength. We then solved for the best-fit CO2 absorption line shape, and calculated the DOD of the fitted CO2 line, and computed its statistics at the various altitude steps. We compared them to CO2 optical depths calculated from spectroscopy based on HITRAN 2008 and the column number densities calculated from the airborne in-situ readings. The 2009 measurements have been analyzed in detail and they were similar on all flights. The results show clear CO2 line shape and absorption signals, which follow the expected changes with aircraft altitude from 3 to 13 km. They showed the expected nearly the linear dependence of DOD vs

  8. Centrifugal techniques for measuring saturated hydraulic conductivity

    USGS Publications Warehouse

    Nimmo, John R.; Mello, Karen A.

    1991-01-01

    Centrifugal force is an alternative to large pressure gradients for the measurement of low values of saturated hydraulic conductivity (Ksat). With a head of water above a porous medium in a centrifuge bucket, both constant-head and falling-head measurements are practical at forces up to at least 1800 times normal gravity. Darcy's law applied to the known centrifugal potential leads to simple formulas for Ksat that are analogous to those used in the standard gravity-driven constant- and falling-head methods. Both centrifugal methods were tested on several fine-textured samples of soil and ceramic with Ksat between about 10−10 and 10−9 m/s. The results were compared to falling-head gravity measurements. The comparison shows most measurements agreeing to within 20% for a given sample, much of the variation probably resulting from run-to-run changes in sample structure. The falling-head centrifuge method proved to be especially simple in design and operation and was more accurate than the constant-head method. With modified apparatus, Ksat measurements less than 10−10 m/s should be attainable.

  9. A 2-Micron Pulsed Integrated Path Differential Absorption Lidar Development For Atmospheric CO2 Concentration Measurements

    NASA Technical Reports Server (NTRS)

    Yu, Jirong; Petros, Mulugeta; Reithmaier, Karl; Bai, Yingxin; Trieu, Bo C.; Refaat, Tamer F.; Kavaya, Michael J.; Singh, Upendra N.

    2012-01-01

    A 2-micron pulsed, Integrated Path Differential Absorption (IPDA) lidar instrument for ground and airborne atmospheric CO2 concentration measurements via direct detection method is being developed at NASA Langley Research Center. This instrument will provide an alternate approach to measure atmospheric CO2 concentrations with significant advantages. A high energy pulsed approach provides high-precision measurement capability by having high signal-to-noise level and unambiguously eliminates the contamination from aerosols and clouds that can bias the IPDA measurement.

  10. [Research on the NO2 mean concentration measurement with target differential optical absorption spectroscopy technology].

    PubMed

    Liu, Jin; Si, Fu-Qi; Zhou, Hai-Jin; Zhao, Min-Jie; Dou, Ke; Liu, Wen-Qing

    2013-04-01

    A new monitoring method of NO2 concentration near ground with the target difference absorption spectrum technology (Target DOAS) is introduced in the present paper. This method is based on the passive difference absorption spectrum technology. The instrument collects solar reflection spectrum of remote objectives, such as wall of building and mountain, and a specific reference spectrum is chosen to subtract the influence of trace gases from the target to atmospheric top, then integrated concentration of NO2 along the path between the target and instrument can be calculated through the differential absorption spectra inversion algorithm. Since the distance between the instrument and target is given, the mean concentration of NO2 can be derived. With developed Target DOAS instrument, NO2 concentration measurement was carried out in Hefei. And comparison was made between the target DOAS and long path difference absorption spectrometer. Good consistency was presented, proving the feasibility of this method.

  11. Measurements of the infrared absorption cross-sections of HCFC-141b (CH3CFCl2)

    NASA Astrophysics Data System (ADS)

    Le Bris, Karine; McDowell, James; Strong, Kimberly

    2012-10-01

    Detection of atmospheric trace gases by optical remote sensing techniques relies on the availability of molecular absorption spectra over a range of relevant temperatures. Absorption cross-sections of a pure vapour of the hydrochlorofluorocarbon HCFC-141b are reported at a resolution of 0.02 cm-1 for a range of temperatures between 223 and 283 K and a spectral range of 570-3100 cm-1. The integrated intensities of the nine main harmonic bands compare well with the data available from previous experimental studies and with theoretical calculations by ab initio and density functional theories.

  12. Model measurements for new accelerating techniques

    SciTech Connect

    Aronson, S.; Haseroth, H.; Knott, J.; Willis, W.

    1988-06-01

    We summarize the work carried out for the past two years, concerning some different ways for achieving high-field gradients, particularly in view of future linear lepton colliders. These studies and measurements on low power models concern the switched power principle and multifrequency excitation of resonant cavities. 15 refs., 12 figs.

  13. Amplitude Frequency Response Measurement: A Simple Technique

    ERIC Educational Resources Information Center

    Satish, L.; Vora, S. C.

    2010-01-01

    A simple method is described to combine a modern function generator and a digital oscilloscope to configure a setup that can directly measure the amplitude frequency response of a system. This is achieved by synchronously triggering both instruments, with the function generator operated in the "Linear-Sweep" frequency mode, while the oscilloscope…

  14. Photo-acoustic measurements of gas and aerosol absorption with diode lasers.

    PubMed

    Ponomarev, Yu N

    2004-12-01

    The results of designing multipurpose high-sensitive photo-acoustic (PA) detectors and their application to high-resolution diode laser spectroscopy of molecular gases, gas analysis, and aerosol absorption measurements are summarized in this paper. The hardware and software of the diode laser spectrometer with a Helmholtz resonant PA detector providing an absorption sensitivity limit of better than 10(-7)Wm(-1)Hz(-1/2) are described. A procedure is proposed for an experiment involving the measurements of the rotational structure of hot vibrational bands of molecules. The results of the application of the nonresonant PA cell with temporal resolution of signals to measurements of weak nonresonant absorption of gases and soot aerosols are presented, and the possibility of creating a broad-band PA laser diode aerosol-meter is discussed.

  15. Measurement of transient gas flow parameters by diode laser absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Bolshov, M. A.; Kuritsyn, Yu A.; Liger, V. V.; Mironenko, V. R.; Nadezhdinskii, A. I.; Ponurovskii, Ya Ya; Leonov, S. B.; Yarantsev, D. A.

    2015-04-01

    An absorption spectrometer based on diode lasers is developed for measuring two-dimension maps of temperature and water vapour concentration distributions in the combustion zones of two mixing supersonic flows of fuel and oxidiser in the single run regime. The method of measuring parameters of hot combustion zones is based on detection of transient spectra of water vapour absorption. The design of the spectrometer considerably reduces the influence of water vapour absorption along the path of a sensing laser beam outside the burning chamber. The optical scheme is developed, capable of matching measurement results in different runs of mixture burning. A new algorithm is suggested for obtaining information about the mixture temperature by constructing the correlation functions of the experimental spectrum with those simulated from databases. A two-dimensional map of temperature distribution in a test chamber is obtained for the first time under the conditions of plasma-induced combusion of the ethylene - air mixture.

  16. Large antenna measurement and compensation techniques

    NASA Technical Reports Server (NTRS)

    Rahmatsamii, Y.

    1989-01-01

    Antennas in the range of 20 meters or larger will be an integral part of future satellite communication and scientific payloads. In order to commercially use these large, low sidelobe and multiple-beam antennas, a high level of confidence must be established as to their performance in the 0-g and space environment. It is also desirable to compensate for slowly varying surface distortions which could results from thermal effects. An overview of recent advances in performing rf measurements on large antennas is presented with emphasis given to the application of a space-based far-field range utilizing the Space Shuttle. The concept of surface distortion compensation is discussed by providing numerical and measurement results.

  17. A differential absorption technique to estimate atmospheric total water vapor amounts

    NASA Technical Reports Server (NTRS)

    Frouin, Robert; Middleton, Elizabeth

    1990-01-01

    Vertically integrated water-vapor amounts can be remotely determined by measuring the solar radiance reflected by the earth's surface with satellites or aircraft-based instruments. The technique is based on the method by Fowle (1912, 1913) and utilizes the 0.940-micron water-vapor band to retrieve total-water-vapor data that is independent of surface reflectance properties and other atmospheric constituents. A channel combination is proposed to provide more accurate results, the SE-590 spectrometer is used to verify the data, and the effects of atmospheric photon backscattering is examined. The spectrometer and radiosonde data confirm the accuracy of using a narrow and a wide channel centered on the same wavelength to determine water vapor amounts. The technique is suitable for cloudless conditions and can contribute to atmospheric corrections of land-surface parameters.

  18. Thyroglobulin measurement. Techniques, clinical benefits, and pitfalls.

    PubMed

    Spencer, C A; Wang, C C

    1995-12-01

    The validity and reliability of serum Tg measurements is central to accurate diagnosis and cost-effective management of patients with differentiated thyroid carcinoma. Serum Tg is one of the most difficult biochemical tests for a laboratory to maintain at a high level of precision and reliability across the long clinical sampling interval typically employed when monitoring this condition. Physicians should be aware that the diagnostic value of serum Tg measurement is method-dependent, and that intermethod differences still approach 30% even after methods have been standardized on the new CBR reference preparation. This dictates that, ideally, serial serum Tg measurements in a patient should always be made in the same laboratory by the same method. Physicians need to consider a number of factors before selecting a laboratory to perform Tg measurements in patients with differentiated thyroid carcinoma. These factors include assay sensitivity, as judged by the discrimination between lower limit of the euthyroid range and the functional sensitivity limit, as well as assay specificity, especially with respect to serum TgAb interference. laboratories should use a sensitive TgAb immunoassay (not hemagglutination) to prescreen sera for TgAb and report the TgAb level if positive. Furthermore, it is the laboratory's responsibility to advise physicians fully about any change in Tg method as well as the direction of TgAb interference expected with that method. When TgAb is present, the serum Tg level should be a measure of the total (free and TgAb-bound) serum Tg level. Typically, IMA methods underestimate the serum total Tg level, especially when serum TSH is suppressed, whereas RIA methods tend to overestimate the serum total Tg level. The interpretation of a serum Tg level in a TgAb-positive patient should be made with caution and with consideration to any changes in TgAb levels. Serial TgAb monitoring of TgAb-positive patients may provide a physician with additional

  19. Extinction measurement of dense media by an optical coherence tomography technique

    NASA Astrophysics Data System (ADS)

    Ago, Tomoki; Iwai, Toshiaki; Yokota, Ryoko

    2016-10-01

    The optical coherence tomography will make progress as the next stage toward a spectroscopic analysis technique. The spectroscopic analysis is based on the Beer-Lambert law. The absorption and scattering coefficients even for the dense medium can be measured by the Beer-Lambert law because the OCT can detect only the light keeping the coherency which propagated rectilinearly and retro-reflected from scatters. This study is concerned with the quantitative verification of Beer-Lambert law in the OCT imaging.

  20. Nitrous Acid: Intercomparison of techniques and Implications of measurements for photochemistry

    NASA Astrophysics Data System (ADS)

    Pinto, J. P.; Dibb, J. E.; Stutz, J.; Tsai, J.; Ren, X.; Wood, E. C.; Zhang, R.; Lee, B.; Levy, M. E.; Rappenglueck, B.; Lefer, B. L.; Oakes, M. M.; Olaguer, E.

    2013-12-01

    Because of the importance of HONO as a radical reservoir, consistent and accurate measurements of its concentration are needed. As part of the SHARP (Study of Houston Atmospheric Radical Precursors), time series of HONO were obtained by six different measurement techniques on the roof of the Moody Tower (MT) at the University of Houston. Techniques used were long path differential optical absorption spectroscopy (DOAS), stripping coil- (UVVIS) absorption photometry (SC-AP), long-path absorption photometry (LOPAP), mist chamber/ ion chromatography (MC-IC), quantum cascade-tunable infrared laser differential absorption spectroscopy (QC-TILDAS) and ion drift -chemical ionization mass spectrometry (ID-CIMS). Various combinations of techniques were in operation during the period from 15 April through 31 May 2009. This study comparing methods is unique in that it compares several techniques entirely at ambient conditions in a polluted atmosphere. All instruments recorded a similar diurnal pattern of HONO concentrations with higher median and mean values during the night and lower values during the day throughout the entire measurement period. Highest values were observed in the final two weeks of the campaign. The MC-IC, SC-AP, and QC-TILDAS, and to a lesser extent the DOAS, tracked each other most closely. Largest differences between pairs of measurements were evident during the day for concentrations < ~100 ppt. Above ~ 200 ppt, concentrations from the SC-AP, MC-IC and QC-TILDAS converged to within about 20%, with slightly larger discrepancies when DOAS was considered. Relationships between HONO and other gas phase and aerosol species will also be considered.

  1. A photophonic instrument concept to measure atmospheric aerosol absorption. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Engle, C. D.

    1982-01-01

    A laboratory model of an instrument to measure the absorption of atmospheric aerosols was designed, built, and tested. The design was based on the photophonic phenomenon discovered by Bell and an acoustic resonator developed by Helmholtz. Experiments were done to show ways the signal amplitude could be improved and the noise reduced and to confirm the instrument was sensitive enough to be practical. The research was undertaken to develop concepts which show promise of being improvements on the instruments that are presently used to measure the absorption of the Sun's radiation by the Earth's atmospheric aerosols.

  2. Intersubband infrared absorption in Ge(x)Si(1-x)/Si superlattice by photocurrent measurement

    NASA Technical Reports Server (NTRS)

    Karunasiri, R. P. G.; Park, J. S.; Wang, K. L.; Cheng, Li-Jen

    1990-01-01

    The intersubband IR absorption of holes in a Ge(x)Si(1-x)/Si superlattice is observed for the first time. In the experiment, the photocurrent is measured as a function of applied bias which is used to inject holes to the minibands of the superlattice. Two peaks in the photocurrent as a function of bias across the device are observed due to intersubband absorption between the ground to the first and the first of the second light hole minibands. The polarization dependence measurement is used to study the nature of the transitions and is in good agreement with the selection rules.

  3. Mid-infrared carbon monoxide detection system using differential absorption spectroscopy technique

    NASA Astrophysics Data System (ADS)

    Dong, Ming; Sui, Yue; Li, Guo-lin; Zheng, Chuan-tao; Chen, Mei-mei; Wang, Yi-ding

    2015-11-01

    A differential carbon monoxide (CO) concentration sensing device using a self-fabricated spherical mirror (e.g. light-collector) and a multi-pass gas-chamber is presented in this paper. Single-source dual-channel detection method is adopted to suppress the interferences from light source, optical path and environmental changes. Detection principle of the device is described, and both the optical part and the electrical part are developed. Experiments are carried out to evaluate the sensing performance on CO concentration. The results indicate that at 1.013×105 Pa and 298 K, the limit of detection (LoD) is about 11.5 mg/m3 with an absorption length of 40 cm. As the gas concentration gets larger than 115 mg/m3 (1.013×105 Pa, 298 K), the relative detection error falls into the range of -1.7%—+1.9%. Based on 12 h long-term measurement on the 115 mg/m3 and 1 150 mg/m3 CO samples, the maximum detection errors are about 0.9% and 5.5%, respectively. Due to the low cost and competitive characteristics, the proposed device shows potential applications in CO detection in the circumstances of coal-mine production and environmental protection.

  4. Algorithm development for intensity modulated continuous wave laser absorption spectrometry in atmospheric CO2 measurements

    NASA Astrophysics Data System (ADS)

    Lin, B.; Harrison, F. W.; Browell, E. V.; Dobler, J. T.; Bryant, R. B.

    2011-12-01

    Currently, NASA Langley Research Center (LaRC) and ITT are jointly developing algorithms for demonstration of range discrimination using ITT's laser absorption spectrometer (LAS), which is being evaluated for the future NASA Active Sensing of CO2 Emissions during Nights, Days, and Seasons (ASCENDS) mission. The objective of this Decadal Survey mission is to measure atmospheric column CO2 mixing ratios (XCO2) for improved determination of atmospheric carbon sources and sinks. Intensity Modulated Continuous Wave (IM-CW) techniques are used in this LAS approach. The LAS is designed to simultaneously measure CO2 and O2 columns, and these measurements are used to determine the required XCO2 column. The LAS measurements are enabled by the multi-channel operation of the instrument at 1.57 and 1.26-um for CO2 and O2, respectively. The algorithm development for the IM-CW techniques of the multi-channel LAS is focused on addressing key retrieval issues such as surface signal detection, thin cloud and/or aerosol layer rejection, vertical atmospheric range resolution, and optimizing the size of the measurement footprint. With these considerations, the modulation algorithm needs to maintain high enough signal-to-noise ratio (SNR) so that the mission scientific goals can be reached. A basic selection of the modulation algorithms that make XCO2 measurement and thin cloud rejection possible is the stepped frequency modulation scheme and a similar scheme of swept sine modulation. The differences between these two schemes for thin cloud rejection are small, assuming the proper selection of parameters is made. The stepped frequency approach is only a quantified version of swept sine method for the frequencies used. Swept sine scheme is a very common modulation technique for range discrimination, while the consideration of the stepped frequency scheme is based on the history of the rolling-tone modulation used in the instrument in previous successful column CO2 measurements. The

  5. Measurement uncertainty analysis techniques applied to PV performance measurements

    SciTech Connect

    Wells, C.

    1992-10-01

    The purpose of this presentation is to provide a brief introduction to measurement uncertainty analysis, outline how it is done, and illustrate uncertainty analysis with examples drawn from the PV field, with particular emphasis toward its use in PV performance measurements. The uncertainty information we know and state concerning a PV performance measurement or a module test result determines, to a significant extent, the value and quality of that result. What is measurement uncertainty analysis It is an outgrowth of what has commonly been called error analysis. But uncertainty analysis, a more recent development, gives greater insight into measurement processes and tests, experiments, or calibration results. Uncertainty analysis gives us an estimate of the I interval about a measured value or an experiment's final result within which we believe the true value of that quantity will lie. Why should we take the time to perform an uncertainty analysis A rigorous measurement uncertainty analysis: Increases the credibility and value of research results; allows comparisons of results from different labs; helps improve experiment design and identifies where changes are needed to achieve stated objectives (through use of the pre-test analysis); plays a significant role in validating measurements and experimental results, and in demonstrating (through the post-test analysis) that valid data have been acquired; reduces the risk of making erroneous decisions; demonstrates quality assurance and quality control measures have been accomplished; define Valid Data as data having known and documented paths of: Origin, including theory; measurements; traceability to measurement standards; computations; uncertainty analysis of results.

  6. Airborne differential absorption lidar system for measurements of atmospheric water vapor and aerosols.

    PubMed

    Higdon, N S; Browell, E V; Ponsardin, P; Grossmann, B E; Butler, C F; Chyba, T H; Mayo, M N; Allen, R J; Heuser, A W; Grant, W B; Ismail, S; Mayor, S D; Carter, A F

    1994-09-20

    An airborne differential absorption lidar (DIAL) system has been developed at the NASA Langley Research Center for remote measurements of atmospheric water vapor (H(2)O) and aerosols. A solid-state alexandrite laser with a 1-pm linewidth and > 99.85% spectral purity was used as the on-line transmitter. Solid-state avalanche photodiode detector technology has replaced photomultiplier tubes in the receiver system, providing an average increase by a factor of 1.5-2.5 in the signal-to-noise ratio of the H(2)O measurement. By incorporating advanced diagnostic and data-acquisition instrumentation into other subsystems, we achieved additional improvements in system operational reliability and measurement accuracy. Laboratory spectroscopic measurements of H(2)O absorption-line parameters were perfo med to reduce the uncertainties in our knowledge of the absorption cross sections. Line-center H(2)O absorption cross sections were determined, with errors of 3-6%, for more than 120 lines in the 720-nm region. Flight tests of the system were conducted during 1989-1991 on the NASA Wallops Flight Facility Electra aircraft, and extensive intercomparison measurements were performed with dew-point hygrometers and H(2)O radiosondes. The H(2)O distributions measured with the DIAL system differed by ≤ 10% from the profiles determined with the in situ probes in a variety of atmospheric conditions.

  7. Airborne differential absorption lidar system for measurements of atmospheric water vapor and aerosols

    NASA Technical Reports Server (NTRS)

    Carter, Arlen F.; Allen, Robert J.; Mayo, M. Neale; Butler, Carolyn F.; Grossman, Benoist E.; Ismail, Syed; Grant, William B.; Browell, Edward V.; Higdon, Noah S.; Mayor, Shane D.; Ponsardin, Patrick; Hueser, Alene W.

    1994-01-01

    An airborne differential absorption lidar (DIAL) system has been developed at the NASA Langley Research Center for remote measurements of atmospheric water vapor (H2O) and aerosols. A solid-state alexandrite laser with a 1-pm linewidth and greater than 99.85% spectral purity was used as the on-line transmitter. Solid-state avalanche photodiode detector technology has replaced photomultiplier tubes in the receiver system, providing an average increase by a factor of 1.5-2.5 in the signal-to-noise ratio of the H2O measurement. By incorporating advanced diagnostic and data-acquisition instrumentation into other subsystems, we achieved additional improvements in system operational reliability and measurement accuracy. Laboratory spectroscopic measurements of H2O absorption-line parameters were performed to reduce the uncertainties in our knowledge of the absorption cross sections. Line-center H2O absorption cross sections were determined, with errors of 3-6%, for more than 120 lines in the 720-nm region. Flight tests of the system were conducted during 1989-1991 on the NASA Wallops Flight Facility Electra aircraft, and extensive intercomparison measurements were performed with dew-point hygrometers and H2O radiosondes. The H2O distributions measured with the DIAL system differed by less than 10% from the profiles determined with the in situ probes in a variety of atmospheric conditions.

  8. Identification and correction of analog-to-digital-converter nonlinearities and their implications for differential absorption lidar measurements.

    PubMed

    Langford, A O

    1995-12-20

    Differential absorption lidar (DIAL) is a powerful remote-sensing technique widely used to probe the spatial and temporal distribution of ozone and other gaseous atmospheric trace constituents. Although conceptually simple, the DIAL technique presents many challenging and often subtle technical difficulties that can limit its useful range and accuracy. One potentially serious source of error for many DIAL experiments is nonlinearity in the analog-to-digital converters used to capture lidar return signals. The impact of digitizer nonlinearity on DIAL measurements is examined, and a simple and inexpensive low-frequency dithering technique that significantly reduces the effects of ADC nonlinearity in DIAL and other applications in which the signal is repetitively averaged is described.

  9. A benchmarking method to measure dietary absorption efficiency of chemicals by fish.

    PubMed

    Xiao, Ruiyang; Adolfsson-Erici, Margaretha; Åkerman, Gun; McLachlan, Michael S; MacLeod, Matthew

    2013-12-01

    Understanding the dietary absorption efficiency of chemicals in the gastrointestinal tract of fish is important from both a scientific and a regulatory point of view. However, reported fish absorption efficiencies for well-studied chemicals are highly variable. In the present study, the authors developed and exploited an internal chemical benchmarking method that has the potential to reduce uncertainty and variability and, thus, to improve the precision of measurements of fish absorption efficiency. The authors applied the benchmarking method to measure the gross absorption efficiency for 15 chemicals with a wide range of physicochemical properties and structures. They selected 2,2',5,6'-tetrachlorobiphenyl (PCB53) and decabromodiphenyl ethane as absorbable and nonabsorbable benchmarks, respectively. Quantities of chemicals determined in fish were benchmarked to the fraction of PCB53 recovered in fish, and quantities of chemicals determined in feces were benchmarked to the fraction of decabromodiphenyl ethane recovered in feces. The performance of the benchmarking procedure was evaluated based on the recovery of the test chemicals and precision of absorption efficiency from repeated tests. Benchmarking did not improve the precision of the measurements; after benchmarking, however, the median recovery for 15 chemicals was 106%, and variability of recoveries was reduced compared with before benchmarking, suggesting that benchmarking could account for incomplete extraction of chemical in fish and incomplete collection of feces from different tests.

  10. Two-step tomographic reconstructions of temperature and species concentration in a flame based on laser absorption measurements with a rotation platform

    NASA Astrophysics Data System (ADS)

    Xia, Huihui; Kan, Ruifeng; Xu, Zhenyu; He, Yabai; Liu, Jianguo; Chen, Bing; Yang, Chenguang; Yao, Lu; Wei, Min; Zhang, Guangle

    2017-03-01

    We present a system for accurate tomographic reconstruction of the combustion temperature and H2O vapor concentration of a flame based on laser absorption measurements, in combination with an innovative two-step algebraic reconstruction technique. A total of 11 collimated laser beams generated from outputs of fiber-coupled diode lasers formed a two-dimensional 5 × 6 orthogonal beam grids and measured at two H2O absorption transitions (7154.354/7154.353 cm-1 and 7467.769 cm-1). The measurement system was designed on a rotation platform to achieve a two-folder improvement in spatial resolution. Numerical simulation showed that the proposed two-step algebraic reconstruction technique for temperature and concentration, respectively, greatly improved the reconstruction accuracy of species concentration when compared with a traditional calculation. Experimental results demonstrated the good performances of the measurement system and the two-step reconstruction technique for applications such as flame monitoring and combustion diagnosis.

  11. Tear film measurement by optical reflectometry technique.

    PubMed

    Lu, Hui; Wang, Michael R; Wang, Jianhua; Shen, Meixiao

    2014-02-01

    Evaluation of tear film is performed by an optical reflectometer system with alignment guided by a galvanometer scanner. The reflectometer system utilizes optical fibers to deliver illumination light to the tear film and collect the film reflectance as a function of wavelength. Film thickness is determined by best fitting the reflectance-wavelength curve. The spectral reflectance acquisition time is 15 ms, fast enough for detecting film thickness changes. Fast beam alignment of 1 s is achieved by the galvanometer scanner. The reflectometer was first used to evaluate artificial tear film on a model eye with and without a contact lens. The film thickness and thinning rate have been successfully quantified with the minimum measured thickness of about 0.3 μm. Tear films in human eyes, with and without a contact lens, have also been evaluated. A high-contrast spectral reflectance signal from the precontact lens tear film is clearly observed, and the thinning dynamics have been easily recorded from 3.69 to 1.31 μm with lipid layer thickness variation in the range of 41 to 67 nm. The accuracy of the measurement is better than ±0.58% of the film thickness at an estimated tear film refractive index error of ±0.001. The fiber-based reflectometer system is compact and easy to handle.

  12. Remote measurement of corrosion using ultrasonic techniques

    SciTech Connect

    Garcia, K.M.; Porter, A.M.

    1995-02-01

    Supercritical water oxidation (SCWO) technology has the potential of meeting the US Department of Energy`s treatment requirements for mixed radioactive waste. A major technical constraint of the SCWO process is corrosion. Safe operation of a pilot plant requires monitoring of the corrosion rate of the materials of construction. A method is needed for measurement of the corrosion rate taking place during operation. One approach is to directly measure the change in wall thickness or growth of oxide layer at critical points in the SCWO process. In FY-93, a brief survey of the industry was performed to evaluate nondestructive evaluation (NDE) methods for remote corrosion monitoring in supercritical vessels. As a result of this survey, it was determined that ultrasonic testing (UT) methods would be the most cost-effective and suitable method of achieving this. Therefore, the objective for FY-94 was to prove the feasibility of using UT to monitor corrosion of supercritical vessels remotely during operation without removal of the insulation.

  13. Tear film measurement by optical reflectometry technique

    PubMed Central

    Lu, Hui; Wang, Michael R.; Wang, Jianhua; Shen, Meixiao

    2014-01-01

    Abstract. Evaluation of tear film is performed by an optical reflectometer system with alignment guided by a galvanometer scanner. The reflectometer system utilizes optical fibers to deliver illumination light to the tear film and collect the film reflectance as a function of wavelength. Film thickness is determined by best fitting the reflectance-wavelength curve. The spectral reflectance acquisition time is 15 ms, fast enough for detecting film thickness changes. Fast beam alignment of 1 s is achieved by the galvanometer scanner. The reflectometer was first used to evaluate artificial tear film on a model eye with and without a contact lens. The film thickness and thinning rate have been successfully quantified with the minimum measured thickness of about 0.3 μm. Tear films in human eyes, with and without a contact lens, have also been evaluated. A high-contrast spectral reflectance signal from the precontact lens tear film is clearly observed, and the thinning dynamics have been easily recorded from 3.69 to 1.31 μm with lipid layer thickness variation in the range of 41 to 67 nm. The accuracy of the measurement is better than ±0.58% of the film thickness at an estimated tear film refractive index error of ±0.001. The fiber-based reflectometer system is compact and easy to handle. PMID:24500519

  14. Deriving brown carbon from multiwavelength absorption measurements: method and application to AERONET and Aethalometer observations

    NASA Astrophysics Data System (ADS)

    Wang, Xuan; Heald, Colette L.; Sedlacek, Arthur J.; de Sá, Suzane S.; Martin, Scot T.; Lizabeth Alexander, M.; Watson, Thomas B.; Aiken, Allison C.; Springston, Stephen R.; Artaxo, Paulo

    2016-10-01

    The radiative impact of organic aerosols (OA) is a large source of uncertainty in estimating the global direct radiative effect (DRE) of aerosols. This radiative impact includes not only light scattering but also light absorption from a subclass of OA referred to as brown carbon (BrC). However, the absorption properties of BrC are poorly understood, leading to large uncertainties in modeling studies. To obtain observational constraints from measurements, a simple absorption Ångström exponent (AAE) method is often used to separate the contribution of BrC absorption from that of black carbon (BC). However, this attribution method is based on assumptions regarding the spectral dependence of BC that are often violated in the ambient atmosphere. Here we develop a new AAE method which improves upon previous approaches by using the information from the wavelength-dependent measurements themselves and by allowing for an atmospherically relevant range of BC properties, rather than fixing these at a single assumed value. We note that constraints on BC optical properties and mixing state would help further improve this method. We apply this method to multiwavelength absorption aerosol optical depth (AAOD) measurements at AERONET sites worldwide and surface aerosol absorption measurements at multiple ambient sites. We estimate that BrC globally contributes up to 40 % of the seasonally averaged absorption at 440 nm. We find that the mass absorption coefficient of OA (OA-MAC) is positively correlated with the BC / OA mass ratio. Based on the variability in BC properties and BC / OA emission ratio, we estimate a range of 0.05-1.5 m2 g-1 for OA-MAC at 440 nm. Using the combination of AERONET and OMI UV absorption observations we estimate that the AAE388/440 nm for BrC is generally ˜ 4 worldwide, with a smaller value in Europe (< 2). Our analyses of observations at two surface sites (Cape Cod, to the southeast of Boston, and the GoAmazon2014/5 T3 site, to the west of

  15. Ultra Narrowband Optical Filters for Water Vapor Differential Absorption Lidar (DIAL) Atmospheric Measurements

    NASA Technical Reports Server (NTRS)

    Stenholm, Ingrid; DeYoung, Russell J.

    2001-01-01

    Differential absorption lidar (DIAL) systems are being deployed to make vertical profile measurements of atmospheric water vapor from ground and airborne platforms. One goal of this work is to improve the technology of such DIAL systems that they could be deployed on space-based platforms. Since background radiation reduces system performance, it is important to reduce it. One way to reduce it is to narrow the bandwidth of the optical receiver system. However, since the DIAL technique uses two or more wavelengths, in this case separated by 0.1 nm, a fixed-wavelength narrowband filter that would encompass both wavelengths would be broader than required for each line, approximately 0.02 nm. The approach employed in this project is to use a pair of tunable narrowband reflective fiber Bragg gratings. The Bragg gratings are germanium-doped silica core fiber that is exposed to ultraviolet radiation to produce index-of-refraction changes along the length of the fiber. The gratings can be tuned by stretching. The backscattered laser radiation is transmitted through an optical circulator to the gratings, reflected back to the optical circulator by one of the gratings, and then sent to a photodiode. The filter reflectivities were >90 percent, and the overall system efficiency was 30 percent.

  16. Precise methane absorption measurements in the 1.64 μm spectral region for the MERLIN mission.

    PubMed

    Delahaye, T; Maxwell, S E; Reed, Z D; Lin, H; Hodges, J T; Sung, K; Devi, V M; Warneke, T; Spietz, P; Tran, H

    2016-06-27

    In this article we describe a high-precision laboratory measurement targeting the R(6) manifold of the 2ν3 band of (12)CH4. Accurate physical models of this absorption spectrum will be required by the Franco-German, Methane Remote Sensing LIDAR (MERLIN) space mission for retrievals of atmospheric methane. The analysis uses the Hartmann-Tran profile for modeling line shape and also includes line-mixing effects. To this end, six high-resolution and high signal-to-noise absorption spectra of air-broadened methane were recorded using a frequency-stabilized cavity ring-down spectroscopy apparatus. Sample conditions corresponded to room temperature and spanned total sample pressures of 40 hPa - 1013 hPa with methane molar fractions between 1 μmol mol(-1) and 12 μmol mol(-1). All spectroscopic model parameters were simultaneously adjusted in a multispectrum nonlinear least-squares fit to the six measured spectra. Comparison of the fitted model to the measured spectra reveals the ability to calculate the room-temperature, methane absorption coefficient to better than 0.1% at the on-line position of the MERLIN mission. This is the first time that such fidelity has been reached in modeling methane absorption in the investigated spectral region, fulfilling the accuracy requirements of the MERLIN mission. We also found excellent agreement when comparing the present results with measurements obtained over different pressure conditions and using other laboratory techniques. Finally, we also evaluated the impact of these new spectral parameters on atmospheric transmissions spectra calculations.

  17. Precise methane absorption measurements in the 1.64 μm spectral region for the MERLIN mission

    NASA Astrophysics Data System (ADS)

    Delahaye, T.; Maxwell, S. E.; Reed, Z. D.; Lin, H.; Hodges, J. T.; Sung, K.; Devi, V. M.; Warneke, T.; Spietz, P.; Tran, H.

    2016-06-01

    In this article we describe a high-precision laboratory measurement targeting the R(6) manifold of the 2ν3 band of 12CH4. High-fidelity modeling of this absorption spectrum for atmospheric temperature and pressure conditions will be required by the Franco-German, Methane Remote Sensing LIDAR (MERLIN) space mission for retrievals of atmospheric methane. The analysis uses the Hartmann-Tran profile for modeling line shape and also includes line-mixing effects. To this end, six high-resolution and high signal-to-noise ratio absorption spectra of air-broadened methane were recorded using a frequency-stabilized cavity ring-down spectroscopy apparatus. Sample conditions corresponded to room temperature and spanned total sample pressures of 40 hPa-1013 hPa with methane molar fractions between 1 µmol mol-1 and 12 µmol mol-1. All spectroscopic model parameters were simultaneously adjusted in a multispectrum nonlinear least squares fit to the six measured spectra. Comparison of the fitted model to the measured spectra reveals the ability to calculate the room temperature, methane absorption coefficient to better than 0.1% at the online position of the MERLIN mission. This is the first time that such fidelity has been reached in modeling methane absorption in the investigated spectral region, fulfilling the accuracy requirements of the MERLIN mission. We also found excellent agreement when comparing the present results with measurements obtained over different pressure conditions and using other laboratory techniques. Finally, we also evaluated the impact of these new spectral parameters on atmospheric transmissions spectra calculations.

  18. Sixport technique for phase measurement of guided optical fields

    NASA Astrophysics Data System (ADS)

    Molina-Fernandez, I.; Ortega-Moñux, A.; Halir, R.; Wangüemert-Pérez, J. G.; Perez-Lara, P.

    2010-04-01

    This paper introduces the sixport technique for precise amplitude and phase measurement of guided optical fields. The main theoretical advances in this topic are reviewed and recent experimental measurements of a Silicon on Insulator sixport PLC reflectometer are presented.

  19. Energy harvesting in high voltage measuring techniques

    NASA Astrophysics Data System (ADS)

    Żyłka, Pawel; Doliński, Marcin

    2016-02-01

    The paper discusses selected problems related to application of energy harvesting (that is, generating electricity from surplus energy present in the environment) to supply autonomous ultra-low-power measurement systems applicable in high voltage engineering. As a practical example of such implementation a laboratory model of a remote temperature sensor is presented, which is self-powered by heat generated in a current-carrying busbar in HV- switchgear. Presented system exploits a thermoelectric harvester based on a passively cooled Peltier module supplying micro-power low-voltage dc-dc converter driving energy-efficient temperature sensor, microcontroller and a fibre-optic transmitter. Performance of the model in laboratory simulated conditions are presented and discussed.

  20. Developments in Methods for Measuring the Intestinal Absorption of Nanoparticle-Bound Drugs

    PubMed Central

    Liu, Wei; Pan, Hao; Zhang, Caiyun; Zhao, Liling; Zhao, Ruixia; Zhu, Yongtao; Pan, Weisan

    2016-01-01

    With the rapid development of nanotechnology, novel drug delivery systems comprising orally administered nanoparticles (NPs) have been paid increasing attention in recent years. The bioavailability of orally administered drugs has significant influence on drug efficacy and therapeutic dosage, and it is therefore imperative that the intestinal absorption of oral NPs be investigated. This review examines the various literature on the oral absorption of polymeric NPs, and provides an overview of the intestinal absorption models that have been developed for the study of oral nanoparticles. Three major categories of models including a total of eight measurement methods are described in detail (in vitro: dialysis bag, rat gut sac, Ussing chamber, cell culture model; in situ: intestinal perfusion, intestinal loops, intestinal vascular cannulation; in vivo: the blood/urine drug concentration method), and the advantages and disadvantages of each method are contrasted and elucidated. In general, in vitro and in situ methods are relatively convenient but lack accuracy, while the in vivo method is troublesome but can provide a true reflection of drug absorption in vivo. This review summarizes the development of intestinal absorption experiments in recent years and provides a reference for the systematic study of the intestinal absorption of nanoparticle-bound drugs. PMID:27455239

  1. Developments in Methods for Measuring the Intestinal Absorption of Nanoparticle-Bound Drugs.

    PubMed

    Liu, Wei; Pan, Hao; Zhang, Caiyun; Zhao, Liling; Zhao, Ruixia; Zhu, Yongtao; Pan, Weisan

    2016-07-21

    With the rapid development of nanotechnology, novel drug delivery systems comprising orally administered nanoparticles (NPs) have been paid increasing attention in recent years. The bioavailability of orally administered drugs has significant influence on drug efficacy and therapeutic dosage, and it is therefore imperative that the intestinal absorption of oral NPs be investigated. This review examines the various literature on the oral absorption of polymeric NPs, and provides an overview of the intestinal absorption models that have been developed for the study of oral nanoparticles. Three major categories of models including a total of eight measurement methods are described in detail (in vitro: dialysis bag, rat gut sac, Ussing chamber, cell culture model; in situ: intestinal perfusion, intestinal loops, intestinal vascular cannulation; in vivo: the blood/urine drug concentration method), and the advantages and disadvantages of each method are contrasted and elucidated. In general, in vitro and in situ methods are relatively convenient but lack accuracy, while the in vivo method is troublesome but can provide a true reflection of drug absorption in vivo. This review summarizes the development of intestinal absorption experiments in recent years and provides a reference for the systematic study of the intestinal absorption of nanoparticle-bound drugs.

  2. Measurement uncertainty analysis techniques applied to PV performance measurements

    SciTech Connect

    Wells, C

    1992-10-01

    The purpose of this presentation is to provide a brief introduction to measurement uncertainty analysis, outline how it is done, and illustrate uncertainty analysis with examples drawn from the PV field, with particular emphasis toward its use in PV performance measurements. The uncertainty information we know and state concerning a PV performance measurement or a module test result determines, to a significant extent, the value and quality of that result. What is measurement uncertainty analysis? It is an outgrowth of what has commonly been called error analysis. But uncertainty analysis, a more recent development, gives greater insight into measurement processes and tests, experiments, or calibration results. Uncertainty analysis gives us an estimate of the I interval about a measured value or an experiment`s final result within which we believe the true value of that quantity will lie. Why should we take the time to perform an uncertainty analysis? A rigorous measurement uncertainty analysis: Increases the credibility and value of research results; allows comparisons of results from different labs; helps improve experiment design and identifies where changes are needed to achieve stated objectives (through use of the pre-test analysis); plays a significant role in validating measurements and experimental results, and in demonstrating (through the post-test analysis) that valid data have been acquired; reduces the risk of making erroneous decisions; demonstrates quality assurance and quality control measures have been accomplished; define Valid Data as data having known and documented paths of: Origin, including theory; measurements; traceability to measurement standards; computations; uncertainty analysis of results.

  3. Measurement of the depolarization ratio of Rayleigh scattering at absorption bands

    NASA Astrophysics Data System (ADS)

    Anglister, J.; Steinberg, I. Z.

    1981-01-01

    Measurements of the depolarization ratio ρv of light scattered by the pigments lycopene and β-carotene at the red part of their absorption bands yielded values which are very close to the theoretical value 1/3 of a fully anisotropic molecular polarizability, i.e., that due to an electric dipole moment. Measurements of ρv at the blue edge of the visible absorption band of pinacyanol chloride yielded a value of 0.75 at 472.2 nm, which is the maximum value that a depolarization ratio can assume, and is attained if the average molecular polarizability is zero. This is possible only if the diagonalized polarizability tensor has at least one negative element to counterbalance the positive ones. A negative refractive index at the blue edge of the absorption band is thus experimentally demonstrated.

  4. Experimental determination of the self-absorption factor for MTR plates by passive gamma spectrometric measurement

    NASA Astrophysics Data System (ADS)

    Berndt, R.; Mortreau, P.

    2011-07-01

    The measurement of the absolute activity or the mass of radioactive substances by gamma spectrometry needs to include a correction for the radiation absorption inside the source volume, the so-called self-absorption factor. It depends on geometry and material composition of the source, the detector geometry and on the geometrical arrangement of source and gamma radiation detector; it can be calculated if full information about all that is available. This article however describes how to determine the self-absorption factor from measurements if the radiation sources are plates of uranium fuel with typical parameters of nuclear fuel for MTR reactors and without using detail information on the source geometry, thus allowing easy inspection without relying on - potentially falsified - declarations on the internal properties of the fuel objects and without calculation.

  5. Differences in molar absorptivity of 4-NP with the reaction solution and apparatus affect ALP measurement.

    PubMed

    Huang, W F; Yang, M Q; Zeng, J; Li, L Z; Cheng, G R

    1997-11-01

    We examined the differences in molar absorptivity of 4-NP obtained using different kits for ALP measurement and different instruments. The apparent molar absorptivity of 4-NP in the same reaction solution determined by six different instruments was 15.98, 16.72, 16.06, 17.00, 16.27, 17.62 and that using four different reaction solution kits for ALP with the same instrument was 16.90, 17.38, 17.72, 16.11. We measured ALP in three serum samples with six instruments using the same kit and in twelve serum samples with the same instrument using four kits. ALP activities measured using the same molar absorptivity value differed with the instrument(p < 0.01). However, those measured using the apparent molar absorptivity value for each instrument revealed no significant differences(p > 0.05). In conclusion, we suggest that standard material should be contained in each kit for enzyme measurement and the apparent epsilon for each kit and instrument should be obtained to minimize the systematic error caused by using the same epsilon in different laboratories.

  6. Sensitivity analysis of differential absorption lidar measurements in the mid-infrared region.

    PubMed

    Ambrico, P F; Amodeo, A; Di Girolamo, P; Spinelli, N

    2000-12-20

    The availability of new laser sources that are tunable in the IR spectral region opens new perspectives for differential absorption lidar (DIAL) measurements. A region of particular interest is located in the near IR, where some of the atmospheric pollutants have absorption lines that permit monitoring of emissions from industrial plants and in urban areas. In DIAL measurements, the absorption lines for the species to be measured must be carefully chosen to prevent interference from other molecules, to minimize the dependence of the absorption cross section on temperature, and to optimize the measurements with respect to the optical depth. We analyze the influence of these factors and discuss a set of criteria for selecting the best pairs of wavelengths (lambda(on) and lambda(off)) to be used in DIAL measurements of several molecular species (HCl, CO, CO(2), NO(2), CH(4), H(2)O, and O(2)). Moreover, a sensitivity study has been carried out for selected lines in three different regimes: clean air, urban polluted air, and emission from an incinerator stack.

  7. Improved And Quality Assessed Emission And Absorption Line Measurements In Sloan Digital Sky Survey Galaxies

    NASA Astrophysics Data System (ADS)

    Oh, Kyuseok; Sarzi, M.; Schawinski, K.; Yi, S. K.

    2011-01-01

    We have established a new database of absorption and emission line measurements from the Sloan Digital Sky Survey 7th data release for the galaxies within a redshift of 0.2. This work used publicly available codes, pPXF(penalized pixel-fitting) and GANDALF(gas and absorption line fitting), to achieve robust spectral fits and reliable measurements. The absorption line strengths measured by SDSS pipeline are seriously contaminated by emission fill-in. We effectively separate emission lines from absorption lines. For instance, this work successfully extract [NI] doublet from Mgb and it leads to more realistic result of alpha enhancement on late-type galaxies compared to the previous database. Besides accurately measuring line strengths, the database will be provided with new parameters that are indicative of line strength measurement quality. Users can build a subset of database optimal for their studies using specific cuts in the fitting quality parameters as well as empirical signal-to-noise. Applying these parameters, we found galaxies with dramatically broad line regions among the galaxies with poor fitting quality parameters. We applied a new continuum finding prescriptions to newly identified BLRs and they turned out to be Seyfert I nuclei.

  8. A measurement plan of gas concentration and temperature distribution reconstruction based on the tunable diode laser absorption tomography

    NASA Astrophysics Data System (ADS)

    Liu, Zhao-ran; Jin, Xing; Wang, Guang-yu; Song, Jun-ling

    2014-11-01

    Based on the tunable diode laser absorption tomography, gas concentration and temperature two-dimensional distribution reconstruction is realized using algebraic iterative reconstruction technique (ART). A measurement plan is proposed based on the beam splitting lens, and the corresponding beam arrangement is put forward. The beam splitting lenses are used in the plan to making one laser beam cross the measurement area repeatedly. Thus can raise the utilization ratio of laser beam and simplify the structure of measurement platform. A model for H2O vapor concentration and temperature distribution is assumed, and numerical simulation is utilized using two absorption transitions. The feasibility of the measurement plan is proved by the simulation experiment. The influences of initial beam angle, the number of beams and grids on the reconstructed results are analyzed numerically. A concept of phantom description method using in simulation experiments is proposed in order to getting closer to the real experiments. The phantom description method is used in the numerical simulation to evaluating concentration and temperature field reconstruction. Through this method, expected data is sampled from initial data, and reconstructed result is obtained by interpolation. The influence of random errors in projections on distribution reconstruction is also analyzed. The measurement plan can reconstruct the gas concentration and temperature distribution with a simplified measurement platform using beam splitting lenses. The feasibility of the phantom description method is also proved by the simulation experiment.

  9. Acoustic measuring techniques for suspended sediment

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

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

  10. Optical fiber sensor technique for strain measurement

    DOEpatents

    Butler, Michael A.; Ginley, David S.

    1989-01-01

    Laser light from a common source is split and conveyed through two similar optical fibers and emitted at their respective ends to form an interference pattern, one of the optical fibers having a portion thereof subjected to a strain. Changes in the strain cause changes in the optical path length of the strain fiber, and generate corresponding changes in the interference pattern. The interference pattern is received and transduced into signals representative of fringe shifts corresponding to changes in the strain experienced by the strained one of the optical fibers. These signals are then processed to evaluate strain as a function of time, typical examples of the application of the apparatus including electrodeposition of a metallic film on a conductive surface provided on the outside of the optical fiber being strained, so that strains generated in the optical fiber during the course of the electrodeposition are measurable as a function of time. In one aspect of the invention, signals relating to the fringe shift are stored for subsequent processing and analysis, whereas in another aspect of the invention the signals are processed for real-time display of the strain changes under study.

  11. Water vapour foreign-continuum absorption in near-infrared windows from laboratory measurements.

    PubMed

    Ptashnik, Igor V; McPheat, Robert A; Shine, Keith P; Smith, Kevin M; Williams, R Gary

    2012-06-13

    For a long time, it has been believed that atmospheric absorption of radiation within wavelength regions of relatively high infrared transmittance (so-called 'windows') was dominated by the water vapour self-continuum, that is, spectrally smooth absorption caused by H(2)O--H(2)O pair interaction. Absorption due to the foreign continuum (i.e. caused mostly by H(2)O--N(2) bimolecular absorption in the Earth's atmosphere) was considered to be negligible in the windows. We report new retrievals of the water vapour foreign continuum from high-resolution laboratory measurements at temperatures between 350 and 430 K in four near-infrared windows between 1.1 and 5 μm (9000-2000 cm(-1)). Our results indicate that the foreign continuum in these windows has a very weak temperature dependence and is typically between one and two orders of magnitude stronger than that given in representations of the continuum currently used in many climate and weather prediction models. This indicates that absorption owing to the foreign continuum may be comparable to the self-continuum under atmospheric conditions in the investigated windows. The calculated global-average clear-sky atmospheric absorption of solar radiation is increased by approximately 0.46 W m(-2) (or 0.6% of the total clear-sky absorption) by using these new measurements when compared with calculations applying the widely used MTCKD (Mlawer-Tobin-Clough-Kneizys-Davies) foreign-continuum model.

  12. Prediction of Human intestinal absorption of compounds using artificial intelligence techniques.

    PubMed

    Kumar, Rajnish; Sharma, Anju; Siddiqui, Mohammed Haris; Tiwari, Rajesh Kumar

    2017-04-04

    Information about Pharmacokinetics of compounds is an essential component of drug design and development. Modeling the pharmacokinetic properties require identification of the factors effecting absorption, distribution, metabolism and excretion of compounds. There have been continuous attempts in the prediction of absorption of compounds using various Artificial intelligence methods in the effort to reduce the attrition rate of drug candidates entering to preclinical and clinical trials. Currently, there are large numbers of individual predictive models available for absorption using machine learning approaches. In current work, we are presenting a comprehensive study of prediction of absorption. Six Artificial intelligence methods namely, Support vector machine, k- nearest neighbor, Probabilistic neural network, Artificial neural network, Partial least square and Linear discriminant analysis were used for prediction of absorption of compounds with prediction accuracy of 91.54%, 88.33%, 84.30%, 86.51%, 79.07% and 80.08% respectively. Comparative analysis of all the six prediction models suggested that Support vector machine with Radial basis function based kernel is comparatively better for binary classification of compounds using human intestinal absorption and may be useful at preliminary stages of drug design and development.

  13. O absorption measurements in an engineering-scale high-pressure coal gasifier

    NASA Astrophysics Data System (ADS)

    Sun, Kai; Sur, Ritobrata; Jeffries, Jay B.; Hanson, Ronald K.; Clark, Tommy; Anthony, Justin; Machovec, Scott; Northington, John

    2014-10-01

    A real-time, in situ water vapor (H2O) sensor using a tunable diode laser near 1,352 nm was developed to continuously monitor water vapor in the synthesis gas of an engineering-scale high-pressure coal gasifier. Wavelength-scanned wavelength-modulation spectroscopy with second harmonic detection (WMS-2 f) was used to determine the absorption magnitude. The 1 f-normalized, WMS-2 f signal (WMS-2 f/1 f) was insensitive to non-absorption transmission losses including beam steering and light scattering by the particulate in the synthesis gas. A fitting strategy was used to simultaneously determine the water vapor mole fraction and the collisional-broadening width of the transition from the scanned 1 f-normalized WMS-2 f waveform at pressures up to 15 atm, which can be used for large absorbance values. This strategy is analogous to the fitting strategy for wavelength-scanned direct absorption measurements. In a test campaign at the US National Carbon Capture Center, the sensor demonstrated a water vapor detection limit of ~800 ppm (25 Hz bandwidth) at conditions with more than 99.99 % non-absorption transmission losses. Successful unattended monitoring was demonstrated over a 435 h period. Strong correlations between the sensor measurements and transient gasifier operation conditions were observed, demonstrating the capability of laser absorption to monitor the gasification process.

  14. Atmospheric Solar Absorption measurements in the lowest 3-km of the atmosphere with small UAVs

    NASA Astrophysics Data System (ADS)

    Ramana, M. V.; Ramanathan, V.; Roberts, G.; Corrigan, C.; Nguyen, H. V.; McFarquhar, G.

    2007-12-01

    This paper reports unique measurements of atmospheric solar absorption and heating rates in the visible (0.4- 0.7 Ým) and broadband (0.3-2.8 Ým) spectral regions using vertically stacked multiple light weight autonomous unmanned aerial vehicles (UAVs) during the Maldives autonomous UAV campaign (MAC). The UAVs and ground based remote sensing instruments determined most of the parameters required for calculating the albedo and vertical distribution of solar fluxes. Measured fluxes have been compared with those derived from a Monte-Carlo radiative transfer algorithm which can incorporate both gaseous and aerosol components. The analysis focuses on a cloud-free day when the air was polluted due to long range transport from India, and the mean aerosol optical depth (AOD) was 0.31 and mean single scattering albedo was 0.92. The UAV measured absorption AOD was 0.019 which agreed within 20% of the value of 0.024 reported by a ground based instrument. The observed and simulated solar absorption agreed within 5% above 1.0 km and aerosol absorption accounted for 30% to 50% of the absorption depending upon the altitude and solar zenith angle. Thus there was no need to invoke anomalous or excess absorption or unknown physics in clear skies, provided we account for aerosol black carbon. The diurnal mean absorption values for altitudes between 0.5 and 3.0 km msl were observed to be 41¡Ó3 Wm-2 (1.5 K/day) in the broadband region and 8¡Ó2 Wm-2 (0.3 K/day) in the visible region. Future investigations into the atmospheric absorption in cloudy skies will characterize the spatial and temporal variation of the cloudy atmosphere in sufficient detail to simulate the vertical distribution of net solar fluxes to permit comparison with the collected radiative observations. This next phase will utilize 4 stacked UAVs to observe the extended cloud decks off the coast of California. A combination of observations and models will then be used to assess if the amount of solar absorption

  15. Supersonic Mass Flux Measurements via Tunable Diode Laser Absorption and Non-Uniform Flow Modeling

    NASA Technical Reports Server (NTRS)

    Chang, Leyen S.; Strand, Christopher L.; Jeffries, Jay B.; Hanson, Ronald K.; Diskin, Glenn S.; Gaffney, Richard L.; Capriotti, Diego P.

    2011-01-01

    Measurements of mass flux are obtained in a vitiated supersonic ground test facility using a sensor based on line-of-sight (LOS) diode laser absorption of water vapor. Mass flux is determined from the product of measured velocity and density. The relative Doppler shift of an absorption transition for beams directed upstream and downstream in the flow is used to measure velocity. Temperature is determined from the ratio of absorption signals of two transitions (lambda(sub 1)=1349 nm and lambda(sub 2)=1341.5 nm) and is coupled with a facility pressure measurement to obtain density. The sensor exploits wavelength-modulation spectroscopy with second-harmonic detection (WMS-2f) for large signal-to-noise ratios and normalization with the 1f signal for rejection of non-absorption related transmission fluctuations. The sensor line-of-sight is translated both vertically and horizontally across the test section for spatially-resolved measurements. Time-resolved measurements of mass flux are used to assess the stability of flow conditions produced by the facility. Measurements of mass flux are within 1.5% of the value obtained using a facility predictive code. The distortion of the WMS lineshape caused by boundary layers along the laser line-of-sight is examined and the subsequent effect on the measured velocity is discussed. A method for correcting measured velocities for flow non-uniformities is introduced and application of this correction brings measured velocities within 4 m/s of the predicted value in a 1630 m/s flow.

  16. Uranyl ion: A convenient standard for transient molar absorption coefficient measurements

    SciTech Connect

    Bakac, A.; Burrows, H.D.

    1997-12-01

    Transient absorption spectra of an aqueous solution of uranyl sulfate have been measured in the ultraviolet and visible spectra. The excited uranyl ion may be a convenient standard for actinometry and photoacoustic calorimetry. (AIP) {copyright} {ital 1997} {ital Society for Applied Spectroscopy}

  17. Developing and Validating Field Measurement Scales for Absorptive Capacity and Experienced Community of Practice

    ERIC Educational Resources Information Center

    Cadiz, David; Sawyer, John E.; Griffith, Terri L.

    2009-01-01

    Research on knowledge transfer in organizations has been hampered by the lack of tools yielding valid scores for studying critical constructs in concert. The authors developed survey measures of absorptive capacity (the ability to transform new knowledge into usable knowledge) and experienced community of practice (the extent to which a person is…

  18. A balloon ozone measurement utilizing an optical absorption cell and an ejector air sampler

    NASA Technical Reports Server (NTRS)

    Hilsenrath, E.; Ashenfelter, T. E.

    1976-01-01

    Stratospheric ozone was measured from a balloon utilizing an ultraviolet absorption cell. The ambient air was sampled by means of an aspirator attached to the output end of the optical cell. A nominal ozone distribution was obtained from 16 km to the float altitude of 38 km.

  19. Optimal frequency selection of multi-channel O2-band different absorption barometric radar for air pressure measurements

    NASA Astrophysics Data System (ADS)

    Lin, Bing; Min, Qilong

    2017-02-01

    Through theoretical analysis, optimal selection of frequencies for O2 differential absorption radar systems on air pressure field measurements is achieved. The required differential absorption optical depth between a radar frequency pair is 0.5. With this required value and other considerations on water vapor absorption and the contamination of radio wave transmission, frequency pairs of present considered radar system are obtained. Significant impacts on general design of differential absorption remote sensing systems are expected from current results.

  20. Simulations of an airborne laser absorption spectrometer for atmospheric CO2 measurements

    NASA Astrophysics Data System (ADS)

    Lin, B.; Ismail, S.; Harrison, F. W.; Browell, E. V.; Dobler, J. T.; Refaat, T.; Kooi, S. A.

    2012-12-01

    Atmospheric column amount of carbon dioxide (CO2), a major greenhouse gas of the atmosphere, has significantly increased from a preindustrial value of about 280 parts per million (ppm) to more than 390 ppm at present. Our knowledge about the spatiotemporal change and variability of the greenhouse gas, however, is limited. Thus, a near-term space mission of the Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) is crucial to increase our understanding of global sources and sinks of CO2. Currently, NASA Langley Research Center (LaRC) and ITT Exelis are jointly developing and testing an airborne laser absorption spectrometer (LAS) as a prototype instrument for the mission. To assess the space capability of accurate atmospheric CO2 measurements, accurate modeling of the instrument and practical evaluation of space applications are the keys for the success of the ASCENDS mission. This study discusses the simulations of the performance of the airborne instrument and its CO2 measurements. The LAS is a multi-wavelength spectrometer operating on a 1.57 um CO2 absorption line. The Intensity-Modulated Continuous-Wave (IM-CW) approach is implemented in the instrument. To reach accurate CO2 measurements, transmitted signals are monitored internally as reference channels. A model of this kind of instrument includes all major components of the spectrometer, such as modulation generator, fiber amplifier, telescope, detector, transimpedance amplifier, matched filter, and other signal processors. The characteristics of these components are based on actual laboratory tests, product specifications, and general understanding of the functionality of the components. For simulations of atmospheric CO2 measurements, environmental conditions related to surface reflection, atmospheric CO2 and H2O profiles, thin clouds, and aerosol layers, are introduced into the model. Furthermore, all major noise sources such as those from detectors, background radiation, speckle, and

  1. Cesium oscillator strengths measured with a multiple-path-length absorption cell

    NASA Technical Reports Server (NTRS)

    Exton, R. J.

    1976-01-01

    Absorption-oscillator-strength measurements for the principal series in cesium were measured using a multiple-path-length cell. The optical arrangement included a movable transverse path for checking the uniformity of the alkali density along the length of the cell and which also allowed strength measurements to be made simultaneously on both strong and weak lines. The strengths measured on the first 10 doublets indicate an increasing trend in the doublet ratio. The individual line strengths are in close agreement with the high resolution measurements of Pichler (1974) and with the calculations of Norcross (1973).

  2. A numerical study of a method for measuring the effective in situ sound absorption coefficient.

    PubMed

    Kuipers, Erwin R; Wijnant, Ysbrand H; de Boer, André

    2012-09-01

    The accuracy of a method [Wijnant et al., Proc. of ISMA 31, Leuven, Belgium (2010), Vol. 31] for measurement of the effective area-averaged in situ sound absorption coefficient is investigated. Based on a local plane wave assumption, this method can be applied to sound fields for which a model is not available. Investigations were carried out by means of finite element simulations for a typical case. The results show that the method is a promising method for determining the effective area-averaged in situ sound absorption coefficient in complex sound fields.

  3. Error Reduction Methods for Integrated-path Differential-absorption Lidar Measurements

    NASA Technical Reports Server (NTRS)

    Chen, Jeffrey R.; Numata, Kenji; Wu, Stewart T.

    2012-01-01

    We report new modeling and error reduction methods for differential-absorption optical-depth (DAOD) measurements of atmospheric constituents using direct-detection integrated-path differential-absorption lidars. Errors from laser frequency noise are quantified in terms of the line center fluctuation and spectral line shape of the laser pulses, revealing relationships verified experimentally. A significant DAOD bias is removed by introducing a correction factor. Errors from surface height and reflectance variations can be reduced to tolerable levels by incorporating altimetry knowledge and "log after averaging", or by pointing the laser and receiver to a fixed surface spot during each wavelength cycle to shorten the time of "averaging before log".

  4. Measurement of optical absorption coefficient of bio-tissue at 532nm wavelength

    NASA Astrophysics Data System (ADS)

    Huang, Chuyun; Li, Zhengjia; Yao, Yucheng; He, Yanyan

    2007-05-01

    Laser technology has succeeded in medical application. High power 532nm laser has applied in prostate ablation and other clinic application. To understand optical property of bio-tissue at 532nm wavelength, a method of monitoring surface temperature was used to measure absorption coefficient of gall-stone, porcine liver and canine prostate. The absorption coefficient of gall-stone is about 62cm -1 at 532nm wavelength, and those of porcine liver and canine prostate are about 13cm -1 and 5.4cm -1, respectively. These results help to understand the optical property of bio-tissue and offer theoretic reference for optical dosimetry in clinic application.

  5. Improved measurement of the neutron absorption cross section for very low velocities

    NASA Astrophysics Data System (ADS)

    Schroffenegger, J.; Fierlinger, P.; Hollering, A.; Geltenbort, P.; Lauer, T.; Rauch, H.; Zechlau, T.

    2016-01-01

    The absorption cross section of natural Gd and isotopic enriched 157Gd for ultra-cold neutrons (UCN) as a function of the velocity has been measured within a time-of-flight-experiment. Particular attention is paid to small velocities in the region of a few m/s. This is intended to determine the validity of the 1 / v-law governing absorption cross sections in this region and the resulting divergence at v = 0. The experiment does not show any significant violation of 1 / v for v > 3 m /s.

  6. Assimilation of real-time riometer measurements into models of 30 MHz polar cap absorption

    NASA Astrophysics Data System (ADS)

    Rogers, Neil Christopher; Honary, Farideh

    2015-04-01

    Space weather events may adversely affect high frequency (HF) radio propagation, hence the ability to provide nowcasting and forecasting of HF radio absorption is key for industries that rely on HF communications. This paper presents methods of assimilating 30 MHz radio absorption measurements into two types of ionospheric polar cap absorption (PCA) model to improve their performance as nowcasting tools. Type 1 models calculate absorption as m times the square root of the flux of solar protons above an energy threshold, Et. Measurements from 14 riometers during 94 solar proton events (1995-2010) are assimilated by optimising the day and night values of m by linear regression. Further non-linear optimisations are demonstrated in which parameters such as Et are also optimised and additional terms characterise local time and seasonal variations. These optimisations reduce RMS errors by up to 36%. Type 2 models incorporate altitude profiles of electron and neutral densities and electron temperatures. Here the scale height of the effective recombination coefficient profile in the D-region is optimised by regression. Furthermore, two published models of the rigidity cut-off latitude (CL) are assessed by comparison with riometer measurements. A small improvement in performance is observed by introducing a 3-h lag in the geomagnetic index Kp in the CL models. Assimilating data from a single riometer in the polar cap reduces RMS errors below 1 dB with less than 0.2 dB bias. However, many high-latitude riometers now provide absorption measurements in near-real time and we demonstrate how these data may be assimilated by fitting a low-order spherical harmonic function to both the measurements and a PCA model with optimised parameters.

  7. Differential Optical Absorption Spectroscopy (DOAS) using Targets: SO2 and NO2 Measurements in Montevideo City

    NASA Astrophysics Data System (ADS)

    Louban, Ilia; Píriz, Gustavo; Platt, Ulrich; Frins, Erna

    2008-04-01

    SO2 and NO2 were remotely measured in a main street of Montevideo city using Multiaxis-Differential Optical Absorption Spectroscopy (MAX-DOAS) combined with on-field selected targets. Target-based measurements are the basis of a new experimental procedure called Topographic Target Light scattering-DOAS (TOTAL-DOAS) that provides a well define absorption path to measure the near surface distribution of trace gases in the boundary layer. It combines the measurement principles of the long-path DOAS and zenith-scattered sunlight DOAS, within the near UV and VIS spectral range. We give a general description of the procedure and present first results of the 2006 campaign at Montevideo.

  8. Calculation of UV attenuation and colored dissolved organic matter absorption spectra from measurements of ocean color

    NASA Astrophysics Data System (ADS)

    Johannessen, S. C.; Miller, W. L.; Cullen, J. J.

    2003-09-01

    The absorption of ultraviolet and visible radiation by colored or chromophoric dissolved organic matter (CDOM) drives much of marine photochemistry. It also affects the penetration of ultraviolet radiation (UV) into the water column and can confound remote estimates of chlorophyll concentration. Measurements of ocean color from satellites can be used to predict UV attenuation and CDOM absorption spectra from relationships between visible reflectance, UV attenuation, and absorption by CDOM. Samples were taken from the Bering Sea and from the Mid-Atlantic Bight, and water types ranged from turbid, inshore waters to the Gulf Stream. We determined the following relationships between in situ visible radiance reflectance, Lu/Ed (λ) (sr-1), and diffuse attenuation of UV, Kd(λ) (m-1): Kd(323nm) = 0.781[Lu/Ed(412)/Lu/Ed(555)]-1.07; Kd(338nm) = 0.604[Lu/Ed(412)/Lu/Ed(555)]-1.12; Kd(380 nm) = 0.302[Lu/Ed(412)/Lu/Ed(555)]-1.24. Consistent with published observations, these empirical relationships predict that the spectral slope coefficient of CDOM absorption increases as diffuse attenuation of UV decreases. Excluding samples from turbid bays, the ratio of the CDOM absorption coefficient to Kd is 0.90 at 323 nm, 0.86 at 338 nm, and 0.97 at 380 nm. We applied these relationships to SeaWiFS images of normalized water-leaving radiance to calculate the CDOM absorption and UV attenuation in the Mid-Atlantic Bight in May, July, and August 1998. The images showed a decrease in UV attenuation from May to August of approximately 50%. We also produced images of the areal distribution of the spectral slope coefficient of CDOM absorption in the Georgia Bight. The spectral slope coefficient increased offshore and changed with season.

  9. Testing and Measurement Techniques in Heat Transfer and Combustion.

    DTIC Science & Technology

    1980-09-01

    TURBULENT FLAMES USING THE L2F TECHNIQUE by H.Eickboff and R.Schodl II VELOCITY MEASUREMENT TECHNIQUES IN LIQUID SPRAYS USING LASER DOPPLER VELOCIMETRY by...developed a pyrometer capable of measuring the mean and variance of the fluctuation temperatures in a hot gas stream. Laser -Optical-Velocimetry The...combustion system a temperature P.D.P. has to be built up from a number of measurements . The turbulent environments also dictate the use of broadband laser

  10. Imaging of droplets and vapor distributions in a diesel fuel spray by means of a laser absorption-scattering technique.

    PubMed

    Zhang, Y Y; Yoshizaki, T; Nishida, K

    2000-11-20

    The droplets and vapor distributions in a fuel spray were imaged by a dual-wavelength laser absorption-scattering technique. 1,3-dimethylnaphthalene, which has physical properties similar to those of Diesel fuel, strongly absorbs the ultraviolet light near the fourth harmonic (266 nm) of a Nd:YAG laser but is nearly transparent to the visible light near the second harmonic (532 nm) of a Nd:YAG laser. Therefore, droplets and vapor distributions in a Diesel spray can be visualized by an imaging system that uses a Nd:YAG laser as the incident light and 1,3-dimethylnaphthalene as the test fuel. For a quantitative application consideration, the absorption coefficients of dimethylnapthalene vapor at different temperatures and pressures were examined with an optical spectrometer. The findings of this study suggest that this imaging technique has great promise for simultaneously obtaining quantitative information of droplet density and vapor concentration in Diesel fuel spray.

  11. Pulsed Airborne Lidar Measurements of Atmospheric CO2 Column Absorption and Line Shapes from 3-13 km Altitudes

    NASA Technical Reports Server (NTRS)

    Abshire, James; Riris, Haris; Allan, Graham; Weaver, Clark; Mao, Jianping; Sun, Xiaoli; Hasselbrack, William

    2010-01-01

    We have developed a pulsed lidar technique for measuring the tropospheric CO2 concentrations as a candidate for NASA's planned ASCENDS space mission. Our technique uses two pulsed laser transmitters allowing simultaneous measurement of a CO2 absorption line in the 1570 nm band, O2 extinction in the Oxygen A-band and surface height and backscatter. The lidar measures the energy and time of flight of the laser echoes reflected from the atmosphere and surface. The lasers are rapidly and precisely stepped in wavelength across the CO2 line and an O2 line region during the measurement. The direct detection receiver uses a telescope and photon counting detectors, and measures the background light and energies of the laser echoes from the surface along with scattering from any aerosols in the path. The gas extinction and column densities for the CO2 and O2 gases are estimated from the ratio of the on- and off- line signals via the DIAL technique. Time gating is used to isolate the laser echo signals from the surface, and to reject laser photons scattered in the atmosphere. The time of flight of the laser pulses are also used to estimate the height of the scattering surface and to identify cases of mixed cloud and ground scattering. We have developed an airborne lidar to demonstrate the CO2 measurement from the NASA Glenn Lear-25 aircraft. The airborne lidar steps the pulsed laser's wavelength across the selected CO2 line with 20 steps per scan. The line scan rate is 450 Hz, the laser pulse widths are 1 usec, and laser pulse energy is 24 uJ. The time resolved laser backscatter is collected by a 20 cm telescope, detected by a photomultiplier and is recorded by a photon counting system. We made initial airborne measurements on flights during fall 2008. Laser backscatter and absorption measurements were made over a variety of land and water surfaces and through thin clouds. The atmospheric CO2 column measurements using the 1572.33 nm CO2 lines. Two flights were made above the

  12. A method for measuring magnetic fields in sunspots using Zeeman-broadened absorption lines

    NASA Astrophysics Data System (ADS)

    Oostra, Benjamin

    2017-04-01

    We present measurements of magnetic fields in several sunspots using high-resolution spectra obtained with the ESPARTACO spectrograph at the Universidad de los Andes, with the aim to explore experimental possibilities for students. Because the Zeeman line splitting is smaller than the line width, our work only observes broadened absorption lines. This broadening, however, can be measured and suitably modeled, giving realistic quantitative results.

  13. Retrieval of Black Carbon Absorption from Proposed Satellite Measurements Over the Ocean Glint

    NASA Technical Reports Server (NTRS)

    Kaufman, Y. J.; Matins, J. V.; Remer, L. A.; Schoeberl, M. R.; Yamasoe, M. A.; Lau, William K. M. (Technical Monitor)

    2001-01-01

    Haze and air pollution includes many chemicals that together form small particles suspended in the air called aerosols. One of the main ingredients found to affect climate and human health is Black Carbon. Black particles emitted from engines that do not burn the fuel completely, e.g. old trucks. Black carbon absorption of sunlight emerges as one of the key components of man-made forcing of climate. However, global characterization of black carbon emissions, distribution and pathways in which it can affect the amount of solar radiation absorbed by the atmosphere is very uncertain. A new method is proposed to measure sunlight absorption by fine aerosol particles containing black carbon over the ocean glint from a satellite mission designed for this purpose. The satellite will scan the same spot over the ocean in the glint plane and a plane 40 degrees off-glint a minute apart, collecting measurements of the reflected light across the solar spectrum. First the dark ocean off the glint is used to derive aerosol properties. Then the black carbon absorption is derived prop the attenuation of the bright glint by the aerosol layer. Such measurements if realized in a proposed future mission - COBRA are expected to produce global monthly climatology of black carbon absorption with high accuracy (110 to 15%) that can show their effect on climate.

  14. Measurement of the absorption rate of carbon dioxide into aqueous diethanolamine

    SciTech Connect

    Rowley, R.L.; Adams, M.E.; Marshall, T.L.; Oscarson, J.L.; Wilding, W.V.; Anderson, D.J.

    1998-05-01

    Aqueous alkanolamine solutions are commonly used in natural gas sweetening processes to remove the acid gases CO{sub 2} and H{sub 2}S. Absorption rates of gaseous CO{sub 2} into aqueous diethanolamine (DEA) solutions were measured in a quiescent, inverted-tube diffusiometer by monitoring the rate of pressure drop. The absorption rate was found to be insensitive to the diffusion coefficient of CO{sub 2} in solution but very sensitive to the diffusion rate of bicarbonate, protonated DEA, and carbamate ions. Evidence also suggested that chemical reaction equilibrium is rapid relative to diffusion. The diffusion coefficient of DEA in water was also measured using a Taylor dispersion apparatus. A numerical model was developed and used to regress diffusion coefficients of bicarbonate, carbamate, and protonated amine from measured absorption rates. CO{sub 2} absorption rates and diffusion coefficients of bicarbonate, carbamate, and protonated DEA were obtained at 298.2 K and 318.2 K in solutions containing 20, 35, and 50 mass % DEA in water.

  15. Wind measurements: Trimethyl aluminum (TMA) chemical release technique

    NASA Astrophysics Data System (ADS)

    Larsen, M. F.

    2013-11-01

    Chemical release techniques have been used since the earliest days of sounding rocket measurements in the upper atmosphere. The measurements require no telemetry or other complicated electronics and the mechanical systems are relatively simple and very robust. The technique was therefore used early on when more complicated measurement techniques were difficult to implement. Chemical release techniques have remained important, however, even as rocket payloads have become more complex. In particular, the tracer measurements remain important as one of the primary techniques for obtaining neutral wind measurements in the upper mesosphere and thermosphere. Various metal vapor tracers have been used for wind measurements in the upper atmosphere, but the most widely used tracer has become trimethyl aluminum (TMA), which has been used in hundreds of rocket launches since the 1960's. The advantages of TMA include the chemiluminescence produced by the tracer, which makes wind measurements possible at any time during the night, and the fact that the tracer is a liquid, which makes it possible to control both the timing and duration of the release more accurately. An overview of the TMA wind measurement technique is presented, including the design of TMA release hardware and recent results from TMA measurements.

  16. Analysis of Pulsed Airborne Lidar Measurements of Atmospheric CO2 Column Absorption from 3-13 km Altitudes

    NASA Technical Reports Server (NTRS)

    Abshire, James B.; Weaver, Clark J.; Riris, Haris; Mao, Jianping; Sun, Xiaoli; Allan, Graham R.; Hasselbrack, William; Browell, Edward V.

    2011-01-01

    We have developed a pulsed lidar technique for measuring the tropospheric CO2 concentrations as a candidate for NASA's ASCENDS space mission [1]. It uses two pulsed laser transmitters allowing simultaneous measurement of a CO2 absorption line in the 1575 nm band, O2 extinction in the Oxygen A-band, surface height and backscatter profile. The lasers are precisely stepped in wavelength across the CO2 line and an O2 line region during the measurement. The direct detection receiver measures the energies of the laser echoes from the surface along with the range profile of scattering in the path. The column densities for the CO2 and O2 gases are estimated from the ratio of the on- and off-line signals via the integrated path differential absorption (IPDA) technique. The time of flight of the laser pulses is used to estimate the height of the scattering surface and to reject laser photons scattered in the atmosphere. We developed an airborne lidar to demonstrate an early version of the CO2 measurement from the NASA Glenn Lear-25 aircraft. The airborne lidar stepped the pulsed laser's wavelength across the selected CO2 line with 20 wavelength steps per scan. The line scan rate is 450 Hz, the laser pulse widths are 1 usec, and laser pulse energy is 24 uJ. The time resolved laser backscatter is collected by a 20 cm telescope, detected by a NIR photomultiplier and is recorded on every other reading by a photon counting system [2]. During August 2009 we made a series of 2.5 hour long flights and measured the atmospheric CO2 absorption and line shapes using the 1572.33 nm CO2 line. Measurements were made at stepped altitudes from 3-13 km over locations in the US, including the SGP ARM site in Oklahoma, central Illinois, north-eastern North Carolina, and over the Chesapeake Bay and the eastern shore of Virginia. Although the received signal energies were weaker than expected for ASCENDS, clear CO2 line shapes were observed at all altitudes, and some measurements were made

  17. Comparison of techniques for measurement of ambient levels of hydrogen peroxide

    SciTech Connect

    Kleindienst, T.E.; Shepson, P.B.; Hodges, D.N.; Nero, C.M.; Arnts, R.R.; Dasgupta, P.K.; Hwang, H.; Kok, G.L.; Lind, J.A.; Lazrus, A.L.; Mackay, G.I.

    1988-01-01

    A study was conducted to measure hydrogen peroxide from three sources: (1) zero air in the presence and absence of common interferences, (2) steady-state irradiations of hydrocarbon/NO/sub x/ mixtures, and (3) ambient air. The techniques employed for measuring H/sub 2/O/sub 2/ included infrared absorption from a diode laser, fluorescence from an enzymatically produced complex, and chemiluminescence from reaction with luminol. The measurements were conducted simultaneously from a common manifold. Four systems, each of which utilized one of the above techniques, were compared with respect to sensitivity, selectivity, and dynamic range in measuring H/sub 2/O/sub 2/ concentrations ranging from 0.062 to 128 ppbv. For pure samples measured in zero air, agreement of 14-23% was achieved when compared to standard values. In these examples, there was no indication of interferences for an H/sub 2/O/sub 2/ level of 6 ppbv except in the luminol technique where a negative interference was caused by SO/sub 2/. Agreement among techniques was much worse for measurement of H/sub 2/O/sub 2/ produced in the photochemical mixtures. In these mixtures, significant concentrations of organic peroxide were also measured by the enzymatic techniques.

  18. Measurement Techniques for Data Recording and High Temperature Measurement

    DTIC Science & Technology

    2010-10-01

    location. These fiber optic cables convey the infrared data produced by the fireball or other thermal event to a separate array of physically...for Data Recording and High Temperature Measurement 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT ... infrared data produced by the fireball or other thermal event to a separate array of physically protected NIR photo detectors whose data signals are

  19. Inferring brown carbon content from UV aerosol absorption measurements during biomass burning season

    NASA Astrophysics Data System (ADS)

    Mok, J.; Krotkov, N. A.; Arola, A. T.; Torres, O.; Jethva, H. T.; Andrade, M.; Labow, G. J.; Eck, T. F.; Li, Z.; Dickerson, R. R.; Stenchikov, G. L.; Osipov, S.

    2015-12-01

    Measuring spectral dependence of light absorption by colored organic or "brown" carbon (BrC) is important, because of its effects on photolysis rates of ozone and surface ultraviolet (UV) radiation. Enhanced UV spectral absorption by BrC can in turn be exploited for simultaneous retrievals of BrC and black carbon (BC) column amounts in field campaigns. We present an innovative ground-based retrieval of BC and BrC volume fractions and their mass absorption efficiencies during the biomass burning season in Santa Cruz, Bolivia in September-October 2007. Our method combines retrieval of BC volume fraction using AERONET inversion in visible wavelengths with the inversion of total BC+BrC absorption (i.e., column effective imaginary refractive index, kmeas) using Diffuse/Direct irradiance measurements in UV wavelengths. First, we retrieve BrC volume fraction by fitting kmeas at 368nm using Maxwell-Garnett (MG) mixing rules assuming: (1) flat spectral dependence of kBC, (2) known value of kBrC at 368nm from laboratory absorption measurements or smoke chamber experiments, and (3) known BC volume fraction from AERONET inversion. Next, we derive kBrC in short UVB wavelengths by fitting kmeas at 305nm, 311nm, 317nm, 325nm, and 332nm using MG mixing rules and fixed volume fractions of BC and BrC. Our retrievals show larger than expected spectral dependence of kBrC in UVB wavelengths, implying reduced surface UVB irradiance and inhibited photolysis rates of surface ozone destruction. We use a one-dimensional chemical box model to show that the observed strong wavelength dependence of BrC absorption leads to inhibited photolysis of ozone to O(1D), a loss mechanism, while having little impact or even accelerating photolysis of NO2, an ozone production mechanism. Although BC only absorption in biomass burning aerosols is important for climate radiative forcing in the visible wavelengths, additional absorption by BrC is important because of its impact on surface UVB radiation

  20. Pulsed Airborne Lidar Measurements of Atmospheric CO2 Column Absorption and Line Shapes from 3-13 km Altitudes

    NASA Technical Reports Server (NTRS)

    Abshire, J. B.; Riris, H.; Allan, G. R.; Weaver, C.; Hasselbrack, W.; Sun, X.

    2009-01-01

    We have developed a lidar technique for measuring the tropospheric C02 concentrations as a candidate for NASA's planned ASCENDS mission. Our technique uses two pulsed laser transmitters allowing simultaneous measurement of a C02 absorption line in the 1570 nm band, 02 extinction in the Oxygen A-band and surface height and backscatter. The lidar measures the energy and time of flight of the laser echoes reflected from the atmosphere and surface. The lasers are stepped in wavelength across the C02 line and an 02 line region during the measurement. The receiver uses a telescope and photon counting detectors, and measures the background light and energies of the laser echoes from the surface along with scattering from any aerosols in the path. The gas extinction and column densities for the C02 and 02 gases are estimated from the ratio of the on- and off- line signals via the DIAL technique. Time gating is used to isolate the laser echo signals from the surface, and to reject laser photons scattered in the atmosphere. We have developed an airborne lidar to demonstrate the C02 measurement from the NASA Glenn Lear 25 aircraft. The airborne lidar steps the pulsed laser's wavelength across a selected C02 line with 20 steps per scan. The line scan rate is 450 Hz and laser pulse widths are I usec. The time resolved laser backscatter is collected by a 20 cm telescope, detected by a photomultiplier and is recorded by a photon counting system. We made initial airborne measurements on flights during October and December 2008. Laser backscatter and absorption measurements were made over a variety of land and water surfaces and through thin and broken clouds. Atmospheric C02 column measurements using the 1571.4, 1572.02 and 1572.33 nm C02 lines. Two flights were made above the DOE SGP ARM site at altitudes from 3-8 km. These nights were coordinated with DOE investigators who Hew an in-situ C02 sensor on a Cessna aircraft under the path. The increasing C02 line absorptions with

  1. Pulsed Airborne Lidar measurements of Atmospheric CO2 Column Absorption and Line Shapes from 3-13 km altitudes

    NASA Astrophysics Data System (ADS)

    Abshire, J. B.; Riris, H.; Allan, G. R.; Weaver, C. J.; Hasselbrack, W. E.; Sun, X.

    2009-12-01

    We have developed a lidar technique for measuring the tropospheric CO2 concentrations as a candidate for NASA’s planned ASCENDS mission. Our technique uses two pulsed laser transmitters allowing simultaneous measurement of a CO2 absorption line in the 1570 nm band, O2 extinction in the Oxygen A-band and surface height and backscatter. The lidar measures the energy and time of flight of the laser echoes reflected from the atmosphere and surface. The lasers are stepped in wavelength across the CO2 line and an O2 line region during the measurement. The receiver uses a telescope and photon counting detectors, and measures the background light and energies of the laser echoes from the surface along with scattering from any aerosols in the path. The gas extinction and column densities for the CO2 and O2 gases are estimated from the ratio of the on- and off- line signals via the DIAL technique. Time gating is used to isolate the laser echo signals from the surface, and to reject laser photons scattered in the atmosphere. We have developed an airborne lidar to demonstrate the CO2 measurement from the NASA Glenn Lear-25 aircraft. The airborne lidar steps the pulsed laser’s wavelength across a selected CO2 line with 20 steps per scan. The line scan rate is 450 Hz, laser pulse energy is 25 uJ and laser pulse widths are 1 usec. The time resolved laser backscatter is collected by a 20 cm telescope, detected by a photomultiplier and is recorded by a photon counting system. We made initial airborne measurements on flights during October and December 2008. Laser backscatter and absorption measurements were made over a variety of land and water surfaces and through thin and broken clouds. Atmospheric CO2 column measurements using the 1571.4, 1572.02 and 1572.33 nm CO2 lines. Two flights were made above the DOE SGP ARM site at altitudes from 3-8 km. These flights were coordinated with DOE investigators who flew an in-situ CO2 sensor on a Cessna aircraft under the path. The

  2. Development of an alkali chloride vapour-generating apparatus for calibration of ultraviolet absorption measurements

    NASA Astrophysics Data System (ADS)

    Leffler, T.; Brackmann, C.; Berg, M.; Aldén, M.; Li, Z. S.

    2017-02-01

    A novel design of alkali chloride vapour-generating cell has been developed, which can serve as a calibration cell for quantitative ultraviolet absorption concentration measurements and meticulous spectral investigations of alkali compounds. The calibration cell was designed to provide alkali vapour of well-controlled concentrations and temperatures, and consisted of a sealed quartz cell measuring 0.4 m in length with a temperature-controlled reservoir containing solid alkali salt. The cell was placed in a furnace and the alkali vapours generated from the reservoir have direct access to the measuring chamber. Investigations of potassium chloride (KCl) were made on sublimated vapour at temperatures 650, 700, 750, 780, and 800 °C while the reservoir temperature was kept 50 °C lower to avoid condensation. The cell provides stable KCl vapour pressures, and the furnace provides a homogenous temperature profile along the cell. KCl vapour pressures are well characterised and conform the base for determination of the KCl concentration in the cell. The alkali chloride levels matched the concentration range of the absorption setup and indicated a previously employed calibration method to overestimate KCl concentrations. The KCl absorption cross sections for wavelengths λ =197.6 nm and λ =246.2 nm were calculated to be 3.4 × 10-17 and 2.9 × 10-17 cm2/molecule, respectively. The absorption cross section spectra did not show any structural differences with increasing temperature, which could indicate influence of dimers or significant changes of the population in the KCl vibrational states. The KCl absorption cross sections thus did not show any temperature dependence in the temperature region of 700-800 °C. Moreover, the applicability of the calibration cell for measurement of other alkali chlorides and hydroxides is discussed.

  3. Comparison of techniques for measurement of ambient levels of hydrogen peroxide (journal version)

    SciTech Connect

    Kleindienst, T.E.; Shepson, P.B.; Hodges, D.N.; Nero, C.M.; Arnts, R.R.

    1987-01-01

    A study measured hydrogen peroxide (H/sub 2/O/sub 2/) from three sources: (1) zero air in the presence and absence of common interferences; (2) steady-state irradiations of hydrocarbon/NOX mixtures; and (3) ambient air. The techniques employed for measuring H/sub 2/O/sub 2/ included infrared absorption from a diode laser, fluorescence from an enzymatically produced complex, and chemiluminescence from reaction with luminol. Four systems, each of which utilized one of the above techniques, were compared with respect to sensitivity, selectivity, and dynamic range in measuring H/sub 2/O/sub 2/ concentrations ranging from 0.062 to 128 ppbv. There was no indication of interferences for an H/sub 2/O/sub 2/ level of 6 ppbv except in the luminol technique, where a negative interference was caused by SO/sub 2/. Agreement among techniques was much worse for measurement of H/sub 2/O/sub 2/ produced in the photochemical mixtures. Significant concentrations of organic peroxide were measured by the enzymatic technique. During ambient monitoring, the techniques employed showed quantitative agreement.

  4. Bias and uncertainty in the absorption emission measurement of atomic sodium density in the SSME exit plane

    NASA Technical Reports Server (NTRS)

    Bauman, Leslie E.

    1990-01-01

    The measurement of atomic sodium concentration in the TTB 019 firing of April 1990 is significant in that it represents the first measurement of density at the exit plane of the space shuttle main engine. The knowledge of the sodium density, combined with the certainty that the exit plane of the plume is optically thin at the sodium D-line wavelengths, provides essential information for evaluation of diagnostic techniques using sodium atoms, such as resonant Doppler velocimetry for temperature, pressure, and velocity through high resolution fluorescent lineshape analysis. The technique used for the sodium atom line transmission (SALT) measurements is that of resonant absorption emission using a hollow cathode lamp as the reference source. Through the use of two-dimensional kinetic (TDK) predictions of temperature and density for the flight engine case and radiative transfer calculations, this line-of-sight spectrally integrated transmission indicates a sodium atom concentration, i.e., mole fraction, of 0.91e-10. The subject of this paper is the assumptions and measurement uncertainties tied into the calculation. Because of the narrow shape of the source emission, the uncertainties in the absorption profile could introduce considerable bias in the measurement. The following were investigated: (1) the inclusion of hyperfine splitting of the D-lines in the calculation; (2) the use of the flight engine predictions of plume temperature and density versus those for the large throat engine; (3) the assumption of a Gaussian, i.e., Doppler, distribution for the source radiance with a temperature of 400 K; (4) the use of atomic collisional shift and width values for the work by Jongerius; and (5) a Doppler shift for a 7 degree outward velocity vector at the plume edge. Also included in the study was the bias introduced by an uncertainty in the measurement of the D1/D2 line ratio in the source.

  5. A theoretical study of a two-wavelength lidar technique for the measurement of atmospheric temperature profiles

    NASA Technical Reports Server (NTRS)

    Korb, C. L.; Weng, C. Y.

    1982-01-01

    The theory of differential absorption lidar measurements for lines with a Voigt profile is given and applied to a two-wavelength technique for measuring the atmospheric temperature profile using a high J line in the oxygen A band. Explicit expressions for the temperature and pressure dependence of the absorption coefficient are developed for lines with a Voigt profile. An iteration procedure for calculating the temperature for narrow laser bandwidths is described which has an accuracy better than 0.2 K for bandwidths less than 0.01/cm. To reduce the errors in lidar measurements due to uncertainties in pressure, a method for estimating the pressure from the temperature profile is described. A procedure for extending the differential absorption technique to the case of finite laser bandwidth with good accuracy is also described. Simulation results show that a knowledge of the laser frequency is needed to 0.005/cm for accurate temperature measurements. Evaluation of the sensitivity for both ground- and Shuttle-based measurements shows accuracies generally better than 1 K. This technique allows up to an order of magnitude improvement in sensitivity compared to other differential absorption lidar techniques.

  6. Quantitative measurement of hydroxyl radical (OH) concentration in premixed flat flame by combining laser-induced fluorescence and direct absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Chen, Shuang; Su, Tie; Li, Zhong-Shan; Bai, Han-Chen; Yan, Bo; Yang, Fu-Rong

    2016-10-01

    An accurate and reasonable technique combining direct absorption spectroscopy and laser-induced fluorescence (LIF) methods is developed to quantitatively measure the concentrations of hydroxyl in CH4/air flat laminar flame. In our approach, particular attention is paid to the linear laser-induced fluorescence and absorption processes, and experimental details as well. Through measuring the temperature, LIF signal distribution and integrated absorption, spatially absolute OH concentrations profiles are successfully resolved. These experimental results are then compared with the numerical simulation. It is proved that the good quality of the results implies that this method is suitable for calibrating the OH-PLIF measurement in a practical combustor. Project supported by the National Natural Science Foundation of China (Grant No. 11272338), the Science and Technology on Scramjet Key Laboratory Funding, China (Grant No. STSKFKT 2013004), and the China Scholarship Council.

  7. Broadband cavity-enhanced absorption spectroscopy in the ultraviolet spectral region for measurements of nitrogen dioxide and formaldehyde

    NASA Astrophysics Data System (ADS)

    Washenfelder, R. A.; Attwood, A. R.; Flores, J. M.; Zarzana, K. J.; Rudich, Y.; Brown, S. S.

    2016-01-01

    Formaldehyde (CH2O) is the most abundant aldehyde in the atmosphere, and it strongly affects photochemistry through its photolysis. We describe simultaneous measurements of CH2O and nitrogen dioxide (NO2) using broadband cavity-enhanced absorption spectroscopy in the ultraviolet spectral region. The light source consists of a continuous-wave diode laser focused into a Xenon bulb to produce a plasma that emits high-intensity, broadband light. The plasma discharge is optically filtered and coupled into a 1 m optical cavity. The reflectivity of the cavity mirrors is 0.99930 ± 0.00003 (1- reflectivity = 700 ppm loss) at 338 nm, as determined from the known Rayleigh scattering of He and zero air. This mirror reflectivity corresponds to an effective path length of 1.43 km within the 1 m cell. We measure the cavity output over the 315-350 nm spectral region using a grating monochromator and charge-coupled device array detector. We use published reference spectra with spectral fitting software to simultaneously retrieve CH2O and NO2 concentrations. Independent measurements of NO2 standard additions by broadband cavity-enhanced absorption spectroscopy and cavity ring-down spectroscopy agree within 2 % (slope for linear fit = 1.02 ± 0.03 with r2 = 0.998). Standard additions of CH2O measured by broadband cavity-enhanced absorption spectroscopy and calculated based on flow dilution are also well correlated, with r2 = 0.9998. During constant mixed additions of NO2 and CH2O, the 30 s measurement precisions (1σ) of the current configuration were 140 and 210 pptv, respectively. The current 1 min detection limit for extinction measurements at 315-350 nm provides sufficient sensitivity for measurement of trace gases in laboratory experiments and ground-based field experiments. Additionally, the instrument provides highly accurate, spectroscopically based trace gas detection that may complement higher precision techniques based on non

  8. An X-ray Absorption Edge Detector for High-Resolution Measurement of Undulator Effective K-Parameter

    SciTech Connect

    Yang, B.; Galayda, J.N.; /SLAC

    2007-03-07

    The spectrum of angle-integrated undulator radiation displays a sharp edge at every harmonic photon energy. A technique utilizing this feature to measure minute changes in K-parameters of an undulator in a free-electron laser has been proposed. To date, this technique requires the use of crystal monochromators as bandpass filters whose energy centroid depends on the incident angle of the x-ray beam. In this work we propose to use the absorption edge of an appropriate element as an energy-selective detector whose response is truly independent of the angle of the x-ray beam, and hence independent of electron beam direction and emittance. We will discuss the basic design concept of the detection system and illustrate its projected performance with computer simulations.

  9. Highly sensitive absorption measurements in lithium niobate using whispering gallery resonators

    NASA Astrophysics Data System (ADS)

    Leidinger, Markus; Buse, Karsten; Breunig, Ingo

    2015-02-01

    The absorption coefficient of undoped, congruently grown lithium niobate (LiNbO3) for ordinarily and extraordinarily polarized light is measured in the wavelength range from 390 to 2600 nm using whispering gallery resonators (WGRs). These monolithic cavities guide light by total internal reflection. Their high Q-factor provides several hundred meters of propagation for the coupled light in millimetre size resonators allowing for the measurement of absorption coefficients below 10-2 cm-1, where standard methods such as Fourier-transform or grating spectroscopy meet their limit. In this work the lowest measured value is 10-4 cm-1 at 1700 nm wavelength. Furthermore, the known OH- overtone at 1470 nm wavelength can be resolved clearly.

  10. Ultraviolet-absorption photometer for measurement of ozone on a rocket-boosted payload

    NASA Astrophysics Data System (ADS)

    Sen, B.; Sheldon, W. R.; Benbrook, J. R.

    1996-10-01

    We developed a rocket payload to perform in situ measurements of atmospheric ozone at the University of Houston. The ozone detector is a dual-beam UV-absorption photometer that uses the 253.7-nm radiation from a low-pressure mercury-vapor lamp to illuminate two identical absorption chambers. We describe the design features and the operation of the instrument. The fundamental resolution of the photometer is shown to be 2.7 10 15 molecules m 3 . We present the ozone profile measured during parachute descent following boosted ascent to 60 km by a Nike Orion rocket. The uncertainty in the measurement of this ozone profile is estimated to be 8.2 .

  11. Results of measurement of radio wave absorption in the ionosphere by the AI method

    NASA Technical Reports Server (NTRS)

    Korinevskaya, N. A.

    1972-01-01

    Median noon absorption values for each month from 1964 through 1967, the diurnal variations of absorption on the regular world days, and the seasonal variations of absorption are given. The dependence of the absorption coefficient on sunspot number is analyzed.

  12. Measurement of acetaldehyde in exhaled breath using a laser absorption spectrometer

    NASA Astrophysics Data System (ADS)

    Kamat, Pratyuma C.; Roller, Chad B.; Namjou, Khosrow; Jeffers, James D.; Faramarzalian, Ali; Salas, Rodolfo; McCann, Patrick J.

    2007-07-01

    A high-resolution liquid-nitrogen-free mid-infrared tunable diode laser absorption spectroscopy (TDLAS) system was used to perform real-time measurement of acetaldehyde concentrations in human exhaled breath following ingestion of an alcoholic beverage. Acetaldehyde absorption features were measured near 5.79 μm (1727 cm-1) using a IV-VI semiconductor laser, a 100 m long path optical gas cell, and second- harmonic detection coupled with wavelength modulation. Acetaldehyde levels were measured with a minimum detection limit of 80 ppb for 5 s integration time. The variations in exhaled acetaldehyde levels over time were analyzed prior to and following ingestion of two different amounts of white wine. A method to calibrate acetaldehyde measurements internally using water vapor absorption lines was investigated to eliminate the need for system calibration with gas standards. The potential of a TDLAS system to be used as a noninvasive clinical tool for measurements of large volatile compounds with possible applications in cancer detection is demonstrated.

  13. Temperature sensitivity of differential absorption lidar measurements of water vapor in the 720-nm region

    NASA Technical Reports Server (NTRS)

    Browell, Edward V.; Ismail, Syed; Grossmann, Benoist E.

    1991-01-01

    Recently measured properties of water vapor (H2O) absorption lines have been used in calculations to evalute the temperature sensitivity of differential absorption lidar (Dial) H2O measurements. This paper estimates the temperature sensitivity of H2O lines in the 717-733-nm region for both H2O mixing ratio and number density measurements, and discusses the influence of the H2O line ground state energies E-double-prime, the H2O absorption linewidths, the linewidth temperature dependence parameter, and the atmospheric temperature and pressure variations with altitude and location on the temperature sensitivity calculations. Line parameters and temperature sensitivity calculations for 67 H2O lines in the 720-nm band are given which can be directly used in field experiments. Water vapor lines with E-double-prime values in the 100-300/cm range were found to be optimum for Dial measurements of H2O number densities, while E-double-prime values in the 250-500/cm range were found to be optimum for H2O mixing ratio measurements.

  14. Resonance lamp absorption technique for simultaneous determination of the OH concentration and temperature at 10 spatial positions in combustion environments

    NASA Technical Reports Server (NTRS)

    Shirinzadeh, B.; Gregory, Ray W.

    1994-01-01

    A rugged, easy to implement, line-of-sight absorption instrument which utilizes a low pressure water vapor microwave discharge cell as the light source, has been developed to make simultaneous measurements of the OH concentration and temperature at 10 spatial positions. The design, theory, and capability of the instrument are discussed. Results of the measurements obtained on a methane/air flat flame burner are compared with those obtained using a single-frequency, tunable dye laser system.

  15. Refinement of the ice absorption spectrum in the visible using radiance profile measurements in Antarctic snow

    NASA Astrophysics Data System (ADS)

    Picard, Ghislain; Libois, Quentin; Arnaud, Laurent

    2016-11-01

    Ice is a highly transparent material in the visible. According to the most widely used database (IA2008; Warren and Brandt, 2008), the ice absorption coefficient reaches values lower than 10-3 m-1 around 400 nm. These values were obtained from a vertical profile of spectral radiance measured in a single snow layer at Dome C in Antarctica. We reproduced this experiment using an optical fiber inserted in the snow to record 56 profiles from which 70 homogeneous layers were identified. Applying the same estimation method on every layer yields 70 ice absorption spectra. They present a significant variability but absorption coefficients are overall larger than IA2008 by 1 order of magnitude at 400-450 nm. We devised another estimation method based on Bayesian inference that treats all the profiles simultaneously. It reduces the statistical variability and confirms the higher absorption, around 2 × 10-2 m-1 near the minimum at 440 nm. We explore potential instrumental artifacts by developing a 3-D radiative transfer model able to explicitly account for the presence of the fiber in the snow. The simulation shows that the radiance profile is indeed perturbed by the fiber intrusion, but the error on the ice absorption estimate is not larger than a factor of 2. This is insufficient to explain the difference between our new estimate and IA2008. The same conclusion applies regarding the plausible contamination by black carbon or dust, concentrations reported in the literature are insufficient. Considering the large number of profiles acquired for this study and other estimates from the Antarctic Muon and Neutrino Detector Array (AMANDA), we nevertheless estimate that ice absorption values around 10-2 m-1 at the minimum are more likely than under 10-3 m-1. A new estimate in the range 400-600 nm is provided for future modeling of snow, cloud, and sea-ice optical properties. Most importantly, we recommend that modeling studies take into account the large uncertainty of the ice

  16. Temperature and multi-species measurements by supercontinuum absorption spectroscopy for IC engine applications.

    PubMed

    Werblinski, Thomas; Engel, Sascha R; Engelbrecht, Rainer; Zigan, Lars; Will, Stefan

    2013-06-03

    The first supercontinuum (SC) absorption spectroscopy measurements showing the feasibility of quantitative temperature evaluation are presented to the best of the authors' knowledge. Temperature and multi-species measurements were carried out at a detection rate of ~2 MHz in a high-temperature flow cell within a temperature range from 450 K to 750 K at 0.22 MPa, representing conditions during the suction and compression stroke in an internal combustion (IC) engine. The broadband SC pulses were temporally dispersed into fast wavelength sweeps, covering the overtone absorption bands 2ν(1), 2ν(3), ν(1) + ν(3) of H2O and 3ν(3) of CO2 in the near-infrared region from 1330 nm to 1500 nm. The temperature information is inferred from the peak ratio of a temperature sensitive (1362.42 nm) and insensitive (1418.91 nm) absorption feature in the ν(1) + ν(3) overtone bands of water. The experimental results are in very good agreement with theoretical intensity ratios calculated from absorption spectra based on HiTran data.

  17. Quantitative gas sensing by backscatter-absorption measurements of a pseudorandom code modulated lambda ~ 8-microm quantum cascade laser.

    PubMed

    Gittins, C M; Wetjen, E T; Gmachl, C; Capasso, F; Hutchinson, A L; Sivco, D L; Baillargeon, J N; Cho, A Y

    2000-08-15

    We have demonstrated quantitative chemical vapor detection with a multimode quantum cascade (QC) laser. Experiments incorporated pseudorandom code (PRC) modulation of the laser intensity to permit sensitive absorption measurements of isopropanol vapor at 8.0micro . The demonstration shows the practicality of one technical approach for implementing low-peak-power QC lasers in the transmitter portion of a differential absorption lidar (DIAL) system. With a 31-chip, 300-ns/chip PRC sequence, the measured isopropanol detection limit was 12 parts in 10(6) by volume times meters (~3x10(-3) absorption) for a simple backscatter-absorption measurement configuration.

  18. In vivo measurement of the absorption of strontium in the rumen and small intestine of sheep as an index of calcium absorption capacity.

    PubMed

    Hyde, Michelle L; Fraser, David R

    2014-09-14

    In the present study, a method was developed for determining the alimentary tract Ca absorption capacity of ruminant animals by measuring the absorption rate of Sr after the administration of an oral dose of strontium chloride acting as a tracer analogue of Ca. A close correlation between the absorption rates of the two tracers was observed upon simultaneous administration of an oral dose of stable Sr and radioactive calcium (r 0·98). The Ca absorption capacity of the rumen and small intestine was determined separately by either directing the solution into the rumen or by diverting it into the post-ruminal tract by vasopressin-induced closure of the ruminoreticular groove. The animals were treated with 1α-hydroxyvitamin D3 administered via subcutaneously implanted mini-osmotic pumps. The effect of elevated plasma 1,25-dihydroxycholecalciferol concentrations on the Ca absorption capacity of the alimentary tract was then determined. An increased rate of Sr absorption was observed in both the rumen and small intestine of sheep after treatment, although it is unclear whether the rumen possesses the same vitamin D-dependent Ca absorption pathway as the small intestine.

  19. Towards simultaneous measurements of electronic and structural properties in ultra-fast x-ray free electron laser absorption spectroscopy experiments

    SciTech Connect

    Gaudin, J.; Fourment, C.; Cho, B. I.; Engelhorn, K.; Galtier, E.; Harmand, M.; Leguay, P. M.; Lee, H. J.; Nagler, B.; Nakatsutsumi, M.; Ozkan, C.; Störmer, M.; Toleikis, S.; Tschentscher, Th.; Heimann, P. A.; Dorchies, F.

    2014-04-17

    The rapidly growing ultrafast science with X-ray lasers unveils atomic scale processes with unprecedented time resolution bringing the so called “molecular movie” within reach. X-ray absorption spectroscopy is one of the most powerful x-ray techniques providing both local atomic order and electronic structure when coupled with ad-hoc theory. Collecting absorption spectra within few x-ray pulses is possible only in a dispersive setup. We demonstrate ultrafast time-resolved measurements of the LIII-edge x-ray absorption near-edge spectra of irreversibly laser excited Molybdenum using an average of only few x-ray pulses with a signal to noise ratio limited only by the saturation level of the detector. The simplicity of the experimental set-up makes this technique versatile and applicable for a wide range of pump-probe experiments, particularly in the case of non-reversible processes.

  20. Towards simultaneous measurements of electronic and structural properties in ultra-fast x-ray free electron laser absorption spectroscopy experiments

    DOE PAGES

    Gaudin, J.; Fourment, C.; Cho, B. I.; ...

    2014-04-17

    The rapidly growing ultrafast science with X-ray lasers unveils atomic scale processes with unprecedented time resolution bringing the so called “molecular movie” within reach. X-ray absorption spectroscopy is one of the most powerful x-ray techniques providing both local atomic order and electronic structure when coupled with ad-hoc theory. Collecting absorption spectra within few x-ray pulses is possible only in a dispersive setup. We demonstrate ultrafast time-resolved measurements of the LIII-edge x-ray absorption near-edge spectra of irreversibly laser excited Molybdenum using an average of only few x-ray pulses with a signal to noise ratio limited only by the saturation level ofmore » the detector. The simplicity of the experimental set-up makes this technique versatile and applicable for a wide range of pump-probe experiments, particularly in the case of non-reversible processes.« less

  1. High repetition rate laser produced soft x-ray source for ultrafast x-ray absorption near edge structure measurements.

    PubMed

    Fourmaux, S; Lecherbourg, L; Harmand, M; Servol, M; Kieffer, J C

    2007-11-01

    Recent progress in high intensity ultrafast laser systems provides the opportunity to produce laser plasma x-ray sources exhibiting broad spectrum and high average x-ray flux that are well adapted to x-ray absorption measurements. In this paper, the development of a laser based x-ray absorption near edge structure (XANES) beamline exhibiting high repetition rate by using the Advanced Laser Light Source (ALLS) facility 100 Hz laser system (100 mJ, 35 fs at 800 nm) is presented. This system is based on a broadband tantalum solid target soft x-ray source and a grazing incidence grating spectrometer in the 1-5 nm wavelength range. To demonstrate the high potential of this laser based XANES technique in condensed matter physics, material science, or biology, measurements realized with several samples are presented: VO2 vanadium L edge, Si3N4 nitrogen K edge, and BPDA/PPD polyimide carbon K edge. The characteristics of this laser based beamline are discussed in terms of brightness, signal to noise ratio, and compared to conventional synchrotron broadband x-ray sources which allow achieving similar measurements. Apart from the very compact size and the relative low cost, the main advantages of such a laser based soft x-ray source are the picosecond pulse duration and the perfect synchronization between this x-ray probe and a laser pulse excitation which open the way to the realization of time resolved x-ray absorption measurements with picosecond range time resolution to study the dynamics of ultrafast processes and phase transition.

  2. Measuring Speed Using a Computer--Several Techniques.

    ERIC Educational Resources Information Center

    Pearce, Jon M.

    1988-01-01

    Introduces three different techniques to facilitate the measurement of speed and the associated kinematics and dynamics using a computer. Discusses sensing techniques using optical or ultrasonic sensors, interfacing with a computer, software routines for the interfaces, and other applications. Provides circuit diagrams, pictures, and a program to…

  3. Calibration technique for the neutron surface moisture measurement system

    SciTech Connect

    Watson, W.T.; Shreve, D.C.

    1996-01-01

    A technique for calibrating the response of a surface neutron moisture measurement probe to material moisture concentration has been devised. Tests to ensure that the probe will function in the expected in-tank operating environment are also outlined.

  4. Non-Contact Electrical Conductivity Measurement Technique for Molten Metals

    NASA Technical Reports Server (NTRS)

    Rhim, W. K.; Ishikawa, T.

    1998-01-01

    A non-contact technique of measuring the electrical conductivity (or resistivity) of conducting liquids while they are levitated by the high temperature electrostatic levitator in a high vacuum is reported.

  5. Turbine engine hot-part temperature measurement techniques

    SciTech Connect

    Jackson, A.G.; Prufert, M.B. )

    1992-07-01

    The paper identifies altitude test facility techniques for nonintrusive acquisition of hot-part temperatures using IR radiance measurements. The techniques discussed are applicable for turbojet and low-bypass turbofan engines. Constraints limiting IR measurements in the altitude ground test facility are discussed. Methods for evaluating altitude ground test data are outlined including review of predictive capabilities which enable the determination of the influence of turbine engine hot-part temperatures on IR emissions. 7 refs.

  6. Computed tomography measurement of gaseous fuel concentration by infrared laser light absorption

    NASA Astrophysics Data System (ADS)

    Kawazoe, Hiromitsu; Inagaki, Kazuhisa; Emi, Y.; Yoshino, Fumio

    1997-11-01

    A system to measure gaseous hydrocarbon distributions was devised, which is based on IR light absorption by C-H stretch mode of vibration and computed tomography method. It is called IR-CT method in the paper. Affection of laser light power fluctuation was diminished by monitoring source light intensity by the second IR light detector. Calibration test for methane fuel was carried out to convert spatial data of line absorption coefficient into quantitative methane concentration. This system was applied to three flow fields. The first is methane flow with lifted flame which is generated by a gourd-shaped fuel nozzle. Feasibility of the IR-CT method was confirmed through the measurement. The second application is combustion field with diffusion flame. Calibration to determine absorptivity was undertaken, and measured line absorption coefficient was converted spatial fuel concentration using corresponding temperature data. The last case is modeled in cylinder gas flow of internal combustion engine, where gaseous methane was led to the intake valve in steady flow state. The fuel gas flow simulates behavior of gaseous gasoline which is evaporated at intake valve tulip. Computed tomography measurement of inner flow is essentially difficult because of existence of surrounding wall. In this experiment, IR laser beam was led to planed portion by IR light fiber. It is found that fuel convection by airflow takes great part in air-fuel mixture formation and the developed IR-CT system to measure fuel concentration is useful to analyze air-fuel mixture formation process and to develop new combustors.

  7. Assessment of recent advances in measurement techniques for atmospheric carbon dioxide and methane observations

    NASA Astrophysics Data System (ADS)

    Zellweger, Christoph; Emmenegger, Lukas; Firdaus, Mohd; Hatakka, Juha; Heimann, Martin; Kozlova, Elena; Spain, T. Gerard; Steinbacher, Martin; van der Schoot, Marcel V.; Buchmann, Brigitte

    2016-09-01

    Until recently, atmospheric carbon dioxide (CO2) and methane (CH4) measurements were made almost exclusively using nondispersive infrared (NDIR) absorption and gas chromatography with flame ionisation detection (GC/FID) techniques, respectively. Recently, commercially available instruments based on spectroscopic techniques such as cavity ring-down spectroscopy (CRDS), off-axis integrated cavity output spectroscopy (OA-ICOS) and Fourier transform infrared (FTIR) spectroscopy have become more widely available and affordable. This resulted in a widespread use of these techniques at many measurement stations. This paper is focused on the comparison between a CRDS "travelling instrument" that has been used during performance audits within the Global Atmosphere Watch (GAW) programme of the World Meteorological Organization (WMO) with instruments incorporating other, more traditional techniques for measuring CO2 and CH4 (NDIR and GC/FID). We demonstrate that CRDS instruments and likely other spectroscopic techniques are suitable for WMO/GAW stations and allow a smooth continuation of historic CO2 and CH4 time series. Moreover, the analysis of the audit results indicates that the spectroscopic techniques have a number of advantages over the traditional methods which will lead to the improved accuracy of atmospheric CO2 and CH4 measurements.

  8. Impact of atmospheric state uncertainties on retrieved XCO2 columns from laser differential absorption spectroscopy measurements

    NASA Astrophysics Data System (ADS)

    Zaccheo, T. Scott; Pernini, Timothy; Snell, Hilary E.; Browell, Edward V.

    2014-01-01

    This work assesses the impact of uncertainties in atmospheric state knowledge on retrievals of carbon dioxide column amounts (XCO2) from laser differential absorption spectroscopy (LAS) measurements. LAS estimates of XCO2 columns are normally derived not only from differential absorption observations but also from measured or prior knowledge of atmospheric state that includes temperature, moisture, and pressure along the viewing path. In the case of global space-based monitoring systems, it is often difficult if not impossible to provide collocated in situ measurements of atmospheric state for all observations, so retrievals often rely on collocated remote-sensed data or values derived from numerical weather prediction (NWP) models to describe the atmospheric state. A radiative transfer-based simulation framework, combined with representative global upper-air observations and matched NWP profiles, was used to assess the impact of model differences on estimates of column CO2 and O2 concentrations. These analyses focus on characterizing these errors for LAS measurements of CO2 in the 1.57-μm region and of O2 in the 1.27-μm region. The results provide a set of signal-to-noise metrics that characterize the errors in retrieved values associated with uncertainties in atmospheric state and provide a method for selecting optimal differential absorption line pairs to minimize the impact of these noise terms.

  9. Cavity ring-down spectrometer for high-fidelity molecular absorption measurements

    NASA Astrophysics Data System (ADS)

    Lin, H.; Reed, Z. D.; Sironneau, V. T.; Hodges, J. T.

    2015-08-01

    We present a cavity ring-down spectrometer which was developed for near-infrared measurements of laser absorption by atmospheric greenhouse gases. This system has several important attributes that make it possible to conduct broad spectral surveys and to determine line-by-line parameters with wide dynamic range, and high spectral resolution, sensitivity and accuracy. We demonstrate a noise-equivalent absorption coefficient of 4×10-12 cm-1 Hz-1/2 and a signal-to-noise ratio of 1.5×106:1 in an absorption spectrum of carbon monoxide. We also present high-resolution measurements of trace methane in air spanning more than 1.2 THz and having a frequency axing with an uncertainty less than 100 kHz. Finally, we discuss how this system enables stringent tests of advanced line shape models. To illustrate, we measured an air-broadened carbon dioxide transition over a wide pressure range and analyzed these data with a multi-spectrum fit of the partially correlated, quadratic speed-dependent Nelkin-Ghatak profile. We obtained a quality-of-fit parameter in the multispectrum fit equal to 36,000, thus quantifying small-but-measurable limitations of the model profile. This analysis showed that the line shape depends upon collisional narrowing, speed dependent effects and partial correlations between velocity- and phase-changing collisions.

  10. Optical fiber technique for in-reactor mechanical properties measurement

    SciTech Connect

    Schley, R. S.; Hurley, D. H.; Hua, Z. A.

    2013-01-25

    In-reactor measurement of material properties is required for a better understanding of radiation effects on materials. We present an optical fiber based technique for measuring changes in elastic properties which involves exciting and measuring flexural vibrations in a thin cantilever beam. By exciting the beam and measuring the resonant frequency, changes in the modulus of elasticity can be monitored. The technique is demonstrated by monitoring the elastic property changes of a beam fabricated from copper, as the copper undergoes recrystallization at elevated temperature.

  11. Novel phase measurement technique of the heterodyne laser interferometer

    SciTech Connect

    Choi, Hyunseung; Park, Kyihwan; La, Jongpil

    2005-09-15

    This article describes a novel phase measurement technique to increase the measurement velocity compared to the previous arc-tangent method in the heterodyne laser interferometer. The proposed method can reduce the calculation load because the pulse width modulation signal has a linear relation between the phase difference, while the nonlinear function such as arc tangent is required to demodulate the sinusoidal interferent signal. The brief analysis and measurement scheme of the system, and the experimental result using a Zeeman-stabilized He-Ne laser are presented. They demonstrate that the proposed phase measurement technique is proven to be three times faster and more robust than previous arc-tangent method.

  12. Optical Fiber Technique for In-Reactor Mechanical Properties Measurement

    SciTech Connect

    Robert S. Schley; Zilong Hua; David H. Hurley; Heng Ban

    2012-07-01

    In-reactor measurement of material properties is required for a better understanding of radiation effects on materials. We present an optical fiber based technique for measuring changes in elastic properties which involves exciting and measuring flexural vibrations in a thin cantilever beam. By exciting the beam and measuring the natural frequency, changes in the modulus of elasticity can be monitored. The technique is demonstrated by monitoring the elastic property changes of a beam fabricated from copper, as the copper undergoes recrystallization at elevated temperature.

  13. Optical fiber technique for in-reactor mechanical properties measurement

    NASA Astrophysics Data System (ADS)

    Schley, R. S.; Hurley, D. H.; Hua, Z. A.

    2013-01-01

    In-reactor measurement of material properties is required for a better understanding of radiation effects on materials. We present an optical fiber based technique for measuring changes in elastic properties which involves exciting and measuring flexural vibrations in a thin cantilever beam. By exciting the beam and measuring the resonant frequency, changes in the modulus of elasticity can be monitored. The technique is demonstrated by monitoring the elastic property changes of a beam fabricated from copper, as the copper undergoes recrystallization at elevated temperature.

  14. New Active Optical Technique Developed for Measuring Low-Earth-Orbit Atomic Oxygen Erosion of Polymers

    NASA Technical Reports Server (NTRS)

    Banks, Bruce A.; deGroh, Kim K.; Demko, Rikako

    2003-01-01

    Polymers such as polyimide Kapton (DuPont) and Teflon FEP (DuPont, fluorinated ethylene propylene) are commonly used spacecraft materials because of desirable properties such as flexibility, low density, and in the case of FEP, a low solar absorptance and high thermal emittance. Polymers on the exterior of spacecraft in the low-Earth-orbit (LEO) environment are exposed to energetic atomic oxygen. Atomic oxygen reaction with polymers causes erosion, which is a threat to spacecraft performance and durability. It is, therefore, important to understand the atomic oxygen erosion yield E (the volume loss per incident oxygen atom) of polymers being considered in spacecraft design. The most common technique for determining E is a passive technique based on mass-loss measurements of samples exposed to LEO atomic oxygen during a space flight experiment. There are certain disadvantages to this technique. First, because it is passive, data are not obtained until after the flight is completed. Also, obtaining the preflight and postflight mass measurements is complicated by the fact that many polymers absorb water and, therefore, the mass change due to water absorption can affect the E data. This is particularly true for experiments that receive low atomic oxygen exposures or for samples that have a very low E. An active atomic oxygen erosion technique based on optical measurements has been developed that has certain advantages over the mass-loss technique. This in situ technique can simultaneously provide the erosion yield data on orbit and the atomic oxygen exposure fluence, which is needed for erosion yield determination. In the optical technique, either sunlight or artificial light can be used to measure the erosion of semitransparent or opaque polymers as a result of atomic oxygen attack. The technique is simple and adaptable to a rather wide range of polymers, providing that they have a sufficiently high optical absorption coefficient. If one covers a photodiode with a

  15. Measuring absorption coefficient of scattering liquids using a tube inside an integrating sphere.

    PubMed

    Villanueva, Yolanda; Veenstra, Colin; Steenbergen, Wiendelt

    2016-04-10

    A method for measuring the absorption coefficient μa of absorbing and scattering liquid samples is presented. The sample is injected into a small transparent tube mounted through an integrating sphere. Two models for determining the absorption coefficient using the relative optical output signal are described and validated using aqueous ink absorbers of 0.5 vol.% (0.3  mm-1a<1.55  mm-1) and 1.0 vol.% (1.0  mm-1a<4.0  mm-1) concentrations with 1 vol.% (μs'≈1.4  mm-1) and 10 vol.% (μs'≈14  mm-1) Intralipid dilutions. The low concentrations give μa and μs values, which are comparable with those of biological tissues. One model assumes a uniform light distribution within the sample, which is valid for low absorption. Another model considers light attenuation that obeys Lambert-Beer's law, which may be used for relatively high absorption. Measurements with low and high scattering samples are done for the wavelength range of 400-900 nm. Measured spectra of purely absorbing samples are within 15% agreement with measurements using standard transmission spectrophotometry. For 0.5 vol.% ink absorbers and at wavelengths below 700 nm, measured μa values are higher for samples with low scattering and lower for those with high scattering. At wavelengths above 700 nm, measured μa values do not vary significantly with amount of scattering. For 1.0 vol.% ink absorbers, measured spectra do not change with low scattering. These results indicate that the method can be used for measuring absorption spectra of scattering liquid samples with optical properties similar to biological absorbers, particularly at wavelengths above 700 nm, which is difficult to accomplish with standard transmission spectrophotometry.

  16. Autocorrelation measurement of femtosecond laser pulses based on two-photon absorption in GaP photodiode

    SciTech Connect

    Chong, E. Z.; Watson, T. F.; Festy, F.

    2014-08-11

    Semiconductor materials which exhibit two-photon absorption characteristic within a spectral region of interest can be useful in building an ultra-compact interferometric autocorrelator. In this paper, we report on the evidence of a nonlinear absorption process in GaP photodiodes which was exploited to measure the temporal profile of femtosecond Ti:sapphire laser pulses with a tunable peak wavelength above 680 nm. The two-photon mediated conductivity measurements were performed at an average laser power of less than a few tenths of milliwatts. Its suitability as a single detector in a broadband autocorrelator setup was assessed by investigating the nonlinear spectral sensitivity bandwidth of a GaP photodiode. The highly favourable nonlinear response was found to cover the entire tuning range of our Ti:sapphire laser and can potentially be extended to wavelengths below 680 nm. We also demonstrated the flexibility of GaP in determining the optimum compensation value of the group delay dispersion required to restore the positively chirped pulses inherent in our experimental optical system to the shortest pulse width possible. With the rise in the popularity of nonlinear microscopy, the broad two-photon response of GaP and the simplicity of this technique can provide an alternative way of measuring the excitation laser pulse duration at the focal point of any microscopy systems.

  17. Autocorrelation measurement of femtosecond laser pulses based on two-photon absorption in GaP photodiode

    NASA Astrophysics Data System (ADS)

    Chong, E. Z.; Watson, T. F.; Festy, F.

    2014-08-01

    Semiconductor materials which exhibit two-photon absorption characteristic within a spectral region of interest can be useful in building an ultra-compact interferometric autocorrelator. In this paper, we report on the evidence of a nonlinear absorption process in GaP photodiodes which was exploited to measure the temporal profile of femtosecond Ti:sapphire laser pulses with a tunable peak wavelength above 680 nm. The two-photon mediated conductivity measurements were performed at an average laser power of less than a few tenths of milliwatts. Its suitability as a single detector in a broadband autocorrelator setup was assessed by investigating the nonlinear spectral sensitivity bandwidth of a GaP photodiode. The highly favourable nonlinear response was found to cover the entire tuning range of our Ti:sapphire laser and can potentially be extended to wavelengths below 680 nm. We also demonstrated the flexibility of GaP in determining the optimum compensation value of the group delay dispersion required to restore the positively chirped pulses inherent in our experimental optical system to the shortest pulse width possible. With the rise in the popularity of nonlinear microscopy, the broad two-photon response of GaP and the simplicity of this technique can provide an alternative way of measuring the excitation laser pulse duration at the focal point of any microscopy systems.

  18. Accurate measurement of the specific absorption rate using a suitable adiabatic magnetothermal setup

    NASA Astrophysics Data System (ADS)

    Natividad, Eva; Castro, Miguel; Mediano, Arturo

    2008-03-01

    Accurate measurements of the specific absorption rate (SAR) of solids and fluids were obtained by a calorimetric method, using a special-purpose setup working under adiabatic conditions. Unlike in current nonadiabatic setups, the weak heat exchange with the surroundings allowed a straightforward determination of temperature increments, avoiding the usual initial-time approximations. The measurements performed on a commercial magnetite aqueous ferrofluid revealed a good reproducibility (4%). Also, the measurements on a copper sample allowed comparison between experimental and theoretical values: adiabatic conditions gave SAR values only 3% higher than the theoretical ones, while the typical nonadiabatic method underestimated SAR by 21%.

  19. Time-resolved postdischarge absolute silicon monoxide density measurement by resonant absorption spectroscopy in a nonthermal atmospheric plasma

    SciTech Connect

    Motret, Olivier; Coursimault, Fabien; Pouvesle, Jean-Michel

    2006-11-01

    In this study we present the technique of resonant absorption spectroscopy diagnostic developed to estimate the density of silicon monoxide (SiO) molecules during the postdischarge of an atmospheric dielectric barrier discharge plasma. The ultraviolet (0,0) rovibrational band of the SiO(A {sup 1}{pi}-X {sup 1}{sigma}{sup +}) electronic transition was investigated. Effective values of absorption coefficient and absorption cross section for the rotational transitions under consideration were calculated. The SiO concentration was estimated by comparison between experimental and computed spectra. The self-absorption in the probe reactor was taken into account in the computed spectra.

  20. Atmospheric absorption versus deep ultraviolet (pre-)resonance in Raman lidar measurements

    NASA Astrophysics Data System (ADS)

    Hallen, Hans D.; Willitsford, Adam H.; Neely, Ryan R.; Chadwick, C. Todd; Philbrick, C. Russell

    2016-05-01

    The Raman scattering of several liquids and solid materials has been investigated near the deep ultraviolet absorption features corresponding to the electron energy states of the chemical species present. It is found to provide significant enhancement, but is always accompanied by absorption due to that or other species along the path. We investigate this trade-off for water vapor, although the results for liquid water and ice will be quantitatively very similar. An optical parametric oscillator (OPO) was pumped by the third harmonic of a Nd:YAG laser, and the output frequency doubled to generate a tunable excitation beam in the 215-600 nm range. We use the tunable laser excitation beam to investigate pre-resonance and resonance Raman spectroscopy near an absorption band of ice. A significant enhancement in the Raman signal was observed. The A-term of the Raman scattering tensor, which describes the pre-resonant enhancement of the spectra, is also used to find the primary observed intensities as a function of incident beam energy, although a wide resonance structure near the final-state-effect related absorption in ice is also found. The results suggest that use of pre-resonant or resonant Raman LIDAR could increase the sensitivity to improve spatial and temporal resolution of atmospheric water vapor measurements. However, these shorter wavelengths also exhibit higher ozone absorption. These opposing effects are modeled using MODTRAN for several configurations relevant for studies of boundary layer water and in the vicinity of clouds. Such data could be used in studies of the measurement of energy flow at the water-air and cloud-air interface, and may help with understanding some of the major uncertainties in current global climate models.

  1. Atmospheric solar absorption measurements in the 9-11 micron region using a diode laser heterodyne spectrometer

    NASA Technical Reports Server (NTRS)

    Harward, C. N.; Hoell, J. M., Jr.

    1980-01-01

    A tunable diode laser heterodyne radiometer was developed for ground based measurements of atmospheric solar absorption spectra in the 9 to 12 micron spectral range. The performance and operating characteristics of this tunable infrared heterodyne radiometer (TIHR) is discussed along with recently measured heterodyne solar absorption spectra in the 10 to 11 micron spectral region.

  2. Measurement and calculation of the sound absorption coefficient of pine wood charcoal

    NASA Astrophysics Data System (ADS)

    Suh, Jae Gap; Baik, Kyung min; Kim, Yong Tae; Jung, Sung Soo

    2013-10-01

    Although charcoal has been widely utilized for physical therapy and as a deodorant, water purifier, etc. due to its porous features, research on its role as a sound-absorbing material is rarely found. Thus, the sound absorption coefficients of pine wood charcoal were measured using an impedance tube and were compared with the theoretical predictions in the frequency range of 500˜ 5000 Hz. The theory developed in the current study only considers the lowest possible mode propagating along the air channels of the charcoal and shows good agreements with the measurements. As the frequency is increased, the sound absorption coefficients of pine wood charcoals also increase, but are lower than those of other commonly-used sound-absorbing materials.

  3. Specific absorption rate determination of magnetic nanoparticles through hyperthermia measurements in non-adiabatic conditions

    NASA Astrophysics Data System (ADS)

    Coïsson, M.; Barrera, G.; Celegato, F.; Martino, L.; Vinai, F.; Martino, P.; Ferraro, G.; Tiberto, P.

    2016-10-01

    An experimental setup for magnetic hyperthermia operating in non-adiabatic conditions is described. A thermodynamic model that takes into account the heat exchanged by the sample with the surrounding environment is developed. A suitable calibration procedure is proposed that allows the experimental validation of the model. Specific absorption rate can then be accurately determined just from the measurement of the sample temperature at the equilibrium steady state. The setup and the measurement procedure represent a simplification with respect to other systems requiring calorimeters or crucial corrections for heat flow. Two families of magnetic nanoparticles, one superparamagnetic and one characterised by larger sizes and static hysteresis, have been characterised as a function of field intensity, and specific absorption rate and intrinsic loss power have been obtained.

  4. Novel approach for non-invasive glucose sensing using vibrational contrast CD absorption measurements (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Yakovlev, Vladislav V.; Tovar, Carlos; Hokr, Brett; Petrov, Georgi I.

    2016-03-01

    Noninvasive glucose sensing is a Holy Grail of diabetes mellitus management. Unfortunately, despite a number of innovative concepts and a long history of continuous instrumental improvements, the problem remains largely unsolved. Here we propose and experimentally demonstrate the first successful implementation of a novel strategy based on vibrational overtone circular dichroism absorption measurements. Such an approach uses a short-wavelength infrared excitation (1000-2000 nm), which takes the advantage of lower light scattering and intrinsic chemical contrast provided by the chemical structure of D-glucose molecule. We model the propagation of circular polarized light in scattering medium using Monte Carlo simulations to show the feasibility of such approach in turbid medium and demonstrate the proof of principle using optical detection. We also investigate the possibility of using ultrasound detection through circular dichroism absorption measurements to achieve simple and sensitive glucose monitoring.

  5. VO2+ ions in zinc lead borate glasses studied by EPR and optical absorption techniques.

    PubMed

    Prakash, P Giri; Rao, J Lakshmana

    2005-09-01

    Electron paramagnetic resonance (EPR) and optical absorption spectra of vanadyl ions in zinc lead borate (ZnO-PbO-B2O3) glass system have been studied. EPR spectra of all the glass samples exhibit resonance signals characteristic of VO2+ ions. The values of spin-Hamiltonian parameters indicate that the VO2+ ions in zinc lead borate glasses were present in octahedral sites with tetragonal compression and belong to C4V symmetry. The spin-Hamiltonian parameters g and A are found to be independent of V2O5 content and temperature but changing with ZnO content. The decrease in Deltag( parallel)/Deltag( perpendicular) value with increase in ZnO content indicates that the symmetry around VO2+ ions is more octahedral. The decrease in intensity of EPR signal above 10 mol% of V2O5 is attributed to a fall in the ratio of the number of V4+ ions (N4) to the number of V5+ ions (N5). The number of spins (N) participating in resonance was calculated as a function of temperature for VO2+ doped zinc lead borate glass sample and the activation energy was calculated. From the EPR data, the paramagnetic susceptibility was calculated at various temperatures and the Curie constant was evaluated from the 1/chi-T graph. The optical absorption spectra show single absorption band due to VO2+ ions in tetragonally distorted octahedral sites.

  6. Advanced Intensity-Modulation Continuous-Wave Lidar Techniques for Column CO2 Measurements

    NASA Astrophysics Data System (ADS)

    Campbell, J. F.; Lin, B.; Nehrir, A. R.; Harrison, F. W.; Obland, M. D.; Ismail, S.; Meadows, B.; Browell, E. V.

    2014-12-01

    Global atmospheric carbon dioxide (CO2) measurements for the NASA Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) space mission are critical for improving our understanding of global CO2 sources and sinks. Advanced Intensity-Modulated Continuous-Wave (IM-CW) lidar techniques are investigated as a means of facilitating CO2 measurements from space to meet the ASCENDS measurement requirements. In recent numerical, laboratory and flight experiments we have successfully used the Binary Phase Shift Keying (BPSK) modulation technique to uniquely discriminate surface lidar returns from intermediate aerosol and cloud contamination. We demonstrate the utility of BPSK to eliminate sidelobes in the range profile as a means of making Integrated Path Differential Absorption (IPDA) column CO2 measurements in the presence of optically thin clouds, thereby eliminating the need to correct for sidelobe bias errors caused by the clouds. Furthermore, high accuracy and precision ranging to the surface as well as to the top of intermediate cloud layers, which is a requirement for the inversion of column CO2 number density measurements to column CO2 mixing ratios, has been demonstrated using new hyperfine interpolation techniques that takes advantage of the periodicity of the modulation waveforms. This approach works well for both BPSK and linear swept-frequency modulation techniques. The BPSK technique under investigation has excellent auto-correlation properties while possessing a finite bandwidth. A comparison of BPSK and linear swept-frequency is also discussed in this paper.

  7. Transmittance ratio constrained retrieval technique for lidar cirrus measurements.

    PubMed

    Su, Jia; McCormick, M Patrick; Liu, Zhaoyan; Lee, Robert B; Leavor, Kevin R; Lei, Liqiao

    2012-05-01

    This letter describes a lidar retrieval technique that uses the transmittance ratio as a constraint to determine an average lidar ratio as well as extinction and backscatter coefficients of transparent cirrus clouds. The cloud transmittance ratio is directly obtained from two adjacent elastic lidar backscatter signals. The technique can be applied to cirrus measurements where neither the molecular scattering dominant signals above and below the cloud layer are found nor cloudfree reference profiles are available. The technique has been tested with simulated lidar signals and applied to backscatter lidar measurements at Hampton University, Hampton, Virginia.

  8. Error reduction techniques for measuring long synchrotron mirrors

    SciTech Connect

    Irick, S.

    1998-07-01

    Many instruments and techniques are used for measuring long mirror surfaces. A Fizeau interferometer may be used to measure mirrors much longer than the interferometer aperture size by using grazing incidence at the mirror surface and analyzing the light reflected from a flat end mirror. Advantages of this technique are data acquisition speed and use of a common instrument. Disadvantages are reduced sampling interval, uncertainty of tangential position, and sagittal/tangential aspect ratio other than unity. Also, deep aspheric surfaces cannot be measured on a Fizeau interferometer without a specially made fringe nulling holographic plate. Other scanning instruments have been developed for measuring height, slope, or curvature profiles of the surface, but lack accuracy for very long scans required for X-ray synchrotron mirrors. The Long Trace Profiler (LTP) was developed specifically for long x-ray mirror measurement, and still outperforms other instruments, especially for aspheres. Thus, this paper focuses on error reduction techniques for the LTP.

  9. New radiosonde techniques to measure radiation profiles through the atmosphere

    NASA Astrophysics Data System (ADS)

    Kräuchi, Andreas; Philipona, Rolf; Romanens, Gonzague; Levrat, Gilbert

    2013-04-01

    Solar and thermal radiation fluxes are usually measured at Earth's surface and at the top of the atmosphere. Here we show radiosonde techniques that allow measuring radiation flux profiles and the radiation budget from the Earth's surface to above 30 km in the stratosphere. During two-hour flights solar shortwave and thermal longwave irradiance, downward and upward, is measured with four individual sensors at one-second resolution, along with standard PTU radiosonde profiles. Daytime and nighttime shortwave and longwave radiation measurements, and 24 hours surface measurements, allow determining radiation budget- and total net radiation profiles through the atmosphere. We use a double balloon technique to prevent pendulum motion during the ascent and to keep the sonde as horizontal as possible. New techniques using auto controlled airplanes are now investigated to retrieve the sonde after release at a certain altitude and to land it if possible at the launch station.

  10. Analysis of algebraic reconstruction technique for accurate imaging of gas temperature and concentration based on tunable diode laser absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Hui-Hui, Xia; Rui-Feng, Kan; Jian-Guo, Liu; Zhen-Yu, Xu; Ya-Bai, He

    2016-06-01

    An improved algebraic reconstruction technique (ART) combined with tunable diode laser absorption spectroscopy(TDLAS) is presented in this paper for determining two-dimensional (2D) distribution of H2O concentration and temperature in a simulated combustion flame. This work aims to simulate the reconstruction of spectroscopic measurements by a multi-view parallel-beam scanning geometry and analyze the effects of projection rays on reconstruction accuracy. It finally proves that reconstruction quality dramatically increases with the number of projection rays increasing until more than 180 for 20 × 20 grid, and after that point, the number of projection rays has little influence on reconstruction accuracy. It is clear that the temperature reconstruction results are more accurate than the water vapor concentration obtained by the traditional concentration calculation method. In the present study an innovative way to reduce the error of concentration reconstruction and improve the reconstruction quality greatly is also proposed, and the capability of this new method is evaluated by using appropriate assessment parameters. By using this new approach, not only the concentration reconstruction accuracy is greatly improved, but also a suitable parallel-beam arrangement is put forward for high reconstruction accuracy and simplicity of experimental validation. Finally, a bimodal structure of the combustion region is assumed to demonstrate the robustness and universality of the proposed method. Numerical investigation indicates that the proposed TDLAS tomographic algorithm is capable of detecting accurate temperature and concentration profiles. This feasible formula for reconstruction research is expected to resolve several key issues in practical combustion devices. Project supported by the Young Scientists Fund of the National Natural Science Foundation of China (Grant No. 61205151), the National Key Scientific Instrument and Equipment Development Project of China (Grant

  11. Absorption spectroscopy characterization measurements of a laser-produced Na atomic beam

    SciTech Connect

    Ching, C.H.; Bailey, J.E.; Lake, P.W.; Filuk, A.B.; Adams, R.G.; McKenney, J.

    1997-01-01

    A pulsed Na atomic beam source developed for spectroscopic diagnosis of a high-power ion diode is described. The goal is to produce a {approximately}10{sup 12}-cm{sup {minus}3}-density Na atomic beam that can be injected into the diode acceleration gap to measure electric and magnetic fields from the Stark and Zeeman effects through laser-induced fluorescence or absorption spectroscopy. A {approximately}10 ns full width at half-maximum (FWHM), 1.06 {mu}m, 0.6 J/cm{sup 2} laser incident through a glass slide heats a Na-bearing thin film, creating a plasma that generates a sodium vapor plume. A {approximately}1 {mu}s FWHM dye laser beam tuned to 5890 {Angstrom} is used for absorption measurement of the NaI resonant doublet by viewing parallel to the film surface. The dye laser light is coupled through a fiber to a spectrograph with a time-integrated charge-coupled-device camera. A two-dimensional mapping of the Na vapor density is obtained through absorption measurements at different spatial locations. Time-of-flight and Doppler broadening of the absorption with {approximately}0.1 {Angstrom} spectral resolution indicate that the Na neutral vapor temperature is about 0.5{endash}2 eV. Laser-induced fluorescence from {approximately}1{times}10{sup 12} cm{sup {minus}3} NaI 3s-3p lines observed with a streaked spectrograph provides a signal level sufficient for {approximately}{plus_minus}0.06 {Angstrom} wavelength shift measurements in a mock-up of an ion diode experiment. {copyright} {ital 1997 American Institute of Physics.}

  12. Absorption spectroscopy characterization measurements of a laser-produced Na atomic beam

    SciTech Connect

    Ching, C.H.; Bailey, J.E.; Lake, P.W.; Filuk, A.B.; Adams, R.G.; McKenney, J.

    1996-06-01

    This work describes a pulsed Na atomic beam source developed for spectroscopic diagnosis of a high-power ion diode on the Particle Beam Fusion Accelerator II. The goal is to produce a {approximately} 10{sup 12}-cm{sup {minus}3}-density Na atomic beam that can be injected into the diode acceleration gap to measure electric and magnetic fields from the Stark and Zeeman effects through laser-induced-fluorescence or absorption spectroscopy. A {approximately} 10 ns fwhm, 1.06 {micro}m, 0.6 J/cm{sup 2} laser incident through a glass slide heats a Na-bearing thin film, creating a plasma that generates a sodium vapor plume. A {approximately} 1 {micro}sec fwhm dye laser beam tuned to 5,890 {angstrom} is used for absorption measurement of the Na I resonant doublet by viewing parallel to the film surface. The dye laser light is coupled through a fiber to a spectrograph with a time-integrated CCD camera. A two-dimensional mapping of the Na vapor density is obtained through absorption measurements at different spatial locations. Time-of-flight and Doppler broadening of the absorption with {approximately} 0.1 {angstrom} spectral resolution indicate that the Na neutral vapor temperature is about 0.5 to 2 eV. Laser-induced-fluorescence from {approximately} 1 {times} 10{sup 12}-cm{sup {minus}3} Na I 3s-3p lines observed with a streaked spectrograph provides a signal level sufficient for {approximately} 0.06 {angstrom} wavelength shift measurements in a mock-up of an ion diode experiment.

  13. Measurements of scattering and absorption properties of surface aerosols at a semi-arid site, Anantapur

    NASA Astrophysics Data System (ADS)

    Rama Gopal, K.; Balakrishnaiah, G.; Arafath, S. Md.; Raja Obul Reddy, K.; Siva Kumar Reddy, N.; Pavan Kumari, S.; Raghavendra Kumar, K.; Chakradhar Rao, T.; Lokeswara Reddy, T.; Reddy, R. R.; Nazeer Hussain, S.; Vasudeva Reddy, M.; Suresh Babu, S.; Mallikarjuna Reddy, P.

    2017-01-01

    Aerosol optical properties are continuously measured at a semi-arid station, Anantapur from June 2012 to May 2013 which describes the impact of surface aerosols on climate change over the region. Scattering coefficient (σsct) and absorption coefficient (σabs) are obtained from integrating Nephelometer and Aethalometer, respectively. Also, the single scattering albedo (ω0), Scattering/absorption Ångström exponents were examined during the period of study. Diurnal variations of σsct and σabs show a bi-peak pattern with two maxima and one minimum in a day. The largest values of σsct and σabs are obtained in winter while the lowest values are measured in monsoon. From the measurements σsct550 and σabs550 are found to be 110 ± 12.23 Mm- 1 and 33 ± 5.2 Mm- 1, respectively during the study period. An analysis of the ω0 suggests that there is a more absorbing fraction in the particle composition over the measurement site. The ω0 obtained in the surface boundary layer of Anantapur is below the critical value of 0.86 that determines the shift from cooling to warming. A relationship between scattering/absorption coefficients and scattering/absorption Ångström exponent and single scattering albedo is further examined. In order to understand the origins of the air masses in the study region, we performed seven-day back trajectory analyses based on the NOAA HYSPLIT model. These trajectories were computed at several altitudes (3000 m, 1500 m, and 500 m) for June 2012 and May 2013. These results put in evidence the need of efforts to reduce absorbing particles (black carbon) emissions to avoid the possible warming that would result from the reductions of the cooling aerosol only.

  14. Measurement of optical absorption by calorimetry and analysis of a solar collector

    NASA Astrophysics Data System (ADS)

    Allen, L. C.; Wallace, J.; Deutscher, G.; Lindenfeld, P.

    1988-01-01

    An apparatus is described for the measurement of absorptance, emittance, and selectivity. It can be used to illustrate the relative importance of heat losses by radiation, conduction, and convection in a solar collector, as well as the effects of selectivity and of full or partial evacuation on the efficiency. The apparatus can be constructed in a reasonably well-equipped departmental machine shop, and is suitable for projects or experiments by advanced undergraduate students.

  15. Optical measurements of absorption changes in two-layered diffusive media

    NASA Astrophysics Data System (ADS)

    Fabbri, Francesco; Sassaroli, Angelo; Henry, Michael E.; Fantini, Sergio

    2004-04-01

    We have used Monte Carlo simulations for a two-layered diffusive medium to investigate the effect of a superficial layer on the measurement of absorption variations from optical diffuse reflectance data processed by using: (a) a multidistance, frequency-domain method based on diffusion theory for a semi-infinite homogeneous medium; (b) a differential-pathlength-factor method based on a modified Lambert-Beer law for a homogeneous medium and (c) a two-distance, partial-pathlength method based on a modified Lambert-Beer law for a two-layered medium. Methods (a) and (b) lead to a single value for the absorption variation, whereas method (c) yields absorption variations for each layer. In the simulations, the optical coefficients of the medium were representative of those of biological tissue in the near-infrared. The thickness of the first layer was in the range 0.3-1.4 cm, and the source-detector distances were in the range 1-5 cm, which is typical of near-infrared diffuse reflectance measurements in tissue. The simulations have shown that (1) method (a) is mostly sensitive to absorption changes in the underlying layer, provided that the thickness of the superficial layer is ~0.6 cm or less; (2) method (b) is significantly affected by absorption changes in the superficial layer and (3) method (c) yields the absorption changes for both layers with a relatively good accuracy of ~4% for the superficial layer and ~10% for the underlying layer (provided that the absorption changes are less than 20-30% of the baseline value). We have applied all three methods of data analysis to near-infrared data collected on the forehead of a human subject during electroconvulsive therapy. Our results suggest that the multidistance method (a) and the two-distance partial-pathlength method (c) may better decouple the contributions to the optical signals that originate in deeper tissue (brain) from those that originate in more superficial tissue layers.

  16. Absorption of Solar Radiation by Clouds: A Second Look at Irradiance Measurements

    NASA Technical Reports Server (NTRS)

    Tsay, Si-Chee; King, Michael D.; Cahalan, Robert F.; Lau, William K.-M. (Technical Monitor)

    2001-01-01

    A decade ago, Stephens and Tsay provided an overview of the subject of absorption of solar radiation by clouds in the earth's atmosphere. They summarized the available evidence that pointed to disagreements between theoretical and observed values of cloud absorption (and reflection). At that time, a theoretician's approach (assuming perfect flux measurements) was adopted to test the model uncertainty under various hypotheses, such as the omitted large drops, excess absorbing aerosols, enhanced water vapor continuum absorption, and cloud inhomogeneity. Since then, several advances in theoretical work have been made, but a satisfactory answer for the discrepancy is still lacking. Now, we offer an experimentalist's approach (focusing on field, not laboratory) to examine the observational uncertainty under numerous field factors, such as the temperature dependence, attitude control, and sampling strategy in the spatial and spectral domain. Examples from recent field campaigns have pointed out that these sources of error may be responsible for the unacceptable level of uncertainty (e.g., as large as 20 W/square m). We give examples of each, discuss their contribution to overall uncertainty in shortwave absorption, and suggest a coordinated approach to their solution.

  17. A Precise Calibration Technique for Measuring High Gas Temperatures

    NASA Technical Reports Server (NTRS)

    Gokoglu, Suleyman A.; Schultz, Donald F.

    2000-01-01

    A technique was developed for direct measurement of gas temperatures in the range of 2050 K 2700 K with improved accuracy and reproducibility. The technique utilized the low-emittance of certain fibrous materials, and the uncertainty of the technique was United by the uncertainty in the melting points of the materials, i.e., +/-15 K. The materials were pure, thin, metal-oxide fibers whose diameters varied from 60 microns to 400 microns in the experiments. The sharp increase in the emittance of the fibers upon melting was utilized as indication of reaching a known gas temperature. The accuracy of the technique was confirmed by both calculated low emittance values of transparent fibers, of order 0.01, up to a few degrees below their melting point and by the fiber-diameter independence of the results. This melting-point temperature was approached by increments not larger than 4 K, which was accomplished by controlled increases of reactant flow rates in hydrogen-air and/or hydrogen-oxygen flames. As examples of the applications of the technique, the gas-temperature measurements were used: (a) for assessing the uncertainty in inferring gas temperatures from thermocouple measurements, and (b) for calibrating an IR camera to measure gas temperatures. The technique offers an excellent calibration reference for other gas-temperature measurement methods to improve their accuracy and reliably extending their temperature range of applicability.

  18. A Precise Calibration Technique for Measuring High Gas Temperatures

    NASA Technical Reports Server (NTRS)

    Gokoglu, Suleyman A.; Schultz, Donald F.

    1999-01-01

    A technique was developed for direct measurement of gas temperatures in the range of 2050 K - 2700 K with improved accuracy and reproducibility. The technique utilized the low-emittance of certain fibrous Materials, and the uncertainty of the technique was limited by the uncertainty in the melting points of the materials, i.e., +/- 15 K. The materials were pure, thin, metal-oxide fibers whose diameters varied from 60 mm to 400 mm in the experiments. The sharp increase in the emittance of the fibers upon melting was utilized as indication of reaching a known gas temperature. The accuracy of the technique was confirmed by both calculated low emittance values of transparent fibers, of order 0.01, up to a few degrees below their melting point and by the fiber-diameter independence of the results. This melting-point temperature was approached by increments not larger than 4 K, which was accomplished by controlled increases of reactant flow rates in hydrogen-air and/or hydrogen- oxygen flames. As examples of the applications of the technique, the gas-temperature measurements were used (a) for assessing the uncertainty in infering gas temperatures from thermocouple measurements, and (b) for calibrating an IR camera to measure gas temperatures. The technique offers an excellent calibration reference for other gas-temperature measurement methods to improve their accuracy and reliably extending their temperature range of applicability.

  19. Measurement of transient gas flow parameters by diode laser absorption spectroscopy

    SciTech Connect

    Bolshov, M A; Kuritsyn, Yu A; Liger, V V; Mironenko, V R; Nadezhdinskii, A I; Ponurovskii, Ya Ya; Leonov, S B; Yarantsev, D A

    2015-04-30

    An absorption spectrometer based on diode lasers is developed for measuring two-dimension maps of temperature and water vapour concentration distributions in the combustion zones of two mixing supersonic flows of fuel and oxidiser in the single run regime. The method of measuring parameters of hot combustion zones is based on detection of transient spectra of water vapour absorption. The design of the spectrometer considerably reduces the influence of water vapour absorption along the path of a sensing laser beam outside the burning chamber. The optical scheme is developed, capable of matching measurement results in different runs of mixture burning. A new algorithm is suggested for obtaining information about the mixture temperature by constructing the correlation functions of the experimental spectrum with those simulated from databases. A two-dimensional map of temperature distribution in a test chamber is obtained for the first time under the conditions of plasma-induced combusion of the ethylene – air mixture. (laser applications and other topics in quantum electronics)

  20. Percutaneous permeation measurement of topical phthalocyanine by photoacoustic technique

    NASA Astrophysics Data System (ADS)

    Silva, Emanoel P. O.; Barja, Paulo R.; Cardoso, Luiz E.; Beltrame, Milton

    2012-11-01

    This investigation have studied photoacoustic (PA) technique to percutaneous permeation of topical hydroxy-(29H,31H-phthalocyaninate) aluminum (PcAlOH) on pig ear skin. The PcAlOH was incorporated in an emulsion (O/W) (1 mg/dl) with assessed stability parameters of: pH, short and long term stability tests (in the several conditions). The skin was prepared through a heat separation technique, and with a scalpel, the outer skin of the cartilage was removed. The skins were then cut into 4 cm2 pieces and treated with sodium bromide 2 mol/L for 6 h at 37 °C. The epidermis layer was washed with purified water, dried, and stored under reduced pressure until use. The skin permeation kinetics was determined by photoacoustic technique in an open photoacoustic cell. Short (after preparation) and long-term stability tests showed no phase separation. The emulsion developed pH 7.6 and after incorporating the pH was unchanged. The typical times for percutaneous permeation of the emulsion base and emulsion + PcAlOH were 182 (±6) and 438 (±3) s, respectively. This study indicated that the formulations containing PcAlOH have stabile characteristics and show promising results in absorption into the skin. The presence of the photosensitive agent in the formulation contributed significantly to the greater absorption time than observed in the base formulation. The used photoacoustic technical to examine the penetration kinetics of PcAlOH in pig ear skin was adequate and may be employed in the determination of the percutaneous permeation of phthalocyanines.

  1. A Near-Infrared Spectrometer to Measure Zodiacal Light Absorption Spectrum

    NASA Technical Reports Server (NTRS)

    Kutyrev, A. S.; Arendt, R.; Dwek, E.; Kimble, R.; Moseley, S. H.; Rapchun, D.; Silverberg, R. F.

    2010-01-01

    We have developed a high throughput infrared spectrometer for zodiacal light fraunhofer lines measurements. The instrument is based on a cryogenic dual silicon Fabry-Perot etalon which is designed to achieve high signal to noise Fraunhofer line profile measurements. Very large aperture silicon Fabry-Perot etalons and fast camera optics make these measurements possible. The results of the absorption line profile measurements will provide a model free measure of the zodiacal Light intensity in the near infrared. The knowledge of the zodiacal light brightness is crucial for accurate subtraction of zodiacal light foreground for accurate measure of the extragalactic background light after the subtraction of zodiacal light foreground. We present the final design of the instrument and the first results of its performance.

  2. Techniques for Measuring Low Earth Orbital Atomic Oxygen Erosion of Polymers

    NASA Technical Reports Server (NTRS)

    deGroh, Kim K.; Banks, Bruce A.; Demko, Rikako

    2002-01-01

    Polymers such as polyimide Kapton and Teflon FEP (fluorinated ethylene propylene) are commonly used spacecraft materials due to their desirable properties such as flexibility, low density, and in the case of FEP, a low solar absorptance and high thermal emittance. Polymers on the exterior of spacecraft in the low Earth orbit (LEO) environment are exposed to energetic atomic oxygen. Atomic oxygen reaction with polymers causes erosion, which is a threat to spacecraft durability. It is therefore important to understand the atomic oxygen erosion yield (E, the volume loss per incident oxygen atom) of polymers being considered in spacecraft design. The most common technique for determining E is through mass loss measurements. For limited duration exposure experiments, such as shuttle experiments, where the atomic oxygen fluence is often so low that mass loss measurements can not produce acceptable uncertainties, recession measurements based on atomic force microscopy analyses can be used. Equally necessary to knowing the mass loss or recession depth for determining the erosion yield of polymers is the knowledge of the atomic oxygen fluence that the polymers were exposed to in space. This paper discusses the procedures and relevant issues for mass loss and recession depth measurements for passive atomic oxygen erosion yield characterization of polymers, along with techniques for active atomic oxygen fluence and erosion characterization. One active atomic oxygen erosion technique discussed is a new technique based on optical measurements. Details including the use of both semi-transparent and opaque polymers for active erosion measurement are reviewed.

  3. Blower-door techniques for measuring interzonal leakage

    SciTech Connect

    Hult, Erin L.; Sherman, Max H.; Walker, Iain

    2013-01-01

    Abstract The standard blower door test methods, such as ASTM E779, describe how to use a single blower door to determine the total leakage of a single-zone structure such as a detached single-family home. There are no standard test methods for measuring interzonal leakage in a two-zone or multi-zone building envelope such as might be encountered in with an attached garage or in a multifamily building. Some practitioners have been using techniques that involve making multiple measurements with a single blower door as well as combined measurements using multiple blower doors. Even for just two zones there are dozens of combinations of one-door and two-door test protocols that could conceivably be used to determine the interzonal air tightness. We examined many of these two-zone configurations using both simulation and measured data to estimate the accuracy and precision of each technique for realistic measurement scenarios. We also considered the impact of taking measurements at a single pressure versus over multiple pressures. We compared the various techniques and evaluated them for specific uses. Some techniques work better in one leakage regime; some are more sensitive to wind and other noise; some are more suited to determining only a subset of the leakage values. This paper makes recommendations on which techniques to use or not use for various cases and provides data that could be used to develop future test methods.

  4. Development of a Ground-Based Differential Absorption Lidar for High Accurate Measurements of Vertical CO2 Concentration Profiles

    NASA Astrophysics Data System (ADS)

    Nagasawa, Chikao; Abo, Makoto; Shibata, Yasukuni; Nagai, Tomohiro; Nakazato, Masahisa; Sakai, Tetsu; Tsukamoto, Makoto; Sakaizawa, Daisuku

    2010-05-01

    High-accurate vertical carbon dioxide (CO2) profiles are highly desirable in the inverse method to improve quantification and understanding of the global sink and source of CO2, and also global climate change. We have developed a ground based 1.6μm differential absorption lidar (DIAL) to achieve high accurate measurements of vertical CO2 profiles in the atmosphere. The DIAL system is constructed from the optical parametric oscillation(OPO) transmitter and the direct detection receiving system that included a near-infrared photomultiplier tube operating at photon counting mode. The primitive DIAL measurement was achieved successfully the vertical CO2 profile up to 7 km altitude with an error less than 1.0 % by integration time of 50 minutes and vertical resolution of 150m. We are developing the next generation 1.6 μm DIAL that can measure simultaneously the vertical CO2 concentration, temperature and pressure profiles in the atmosphere. The output laser of the OPO is 20mJ at a 500 Hz repetition rate and a 600mm diameter telescope is employed for this measurement. A very narrow interference filter (0.5nm FWHM) is used for daytime measurement. As the spectra of absorption lines of any molecules are influenced basically by the temperature and pressure in the atmosphere, it is important to measure them simultaneously so that the better accuracy of the DIAL measurement may be realized. Moreover, the value of the retrieved CO2 concentration will be improved remarkably by processing the iteration assignment of CO2 concentration, temperature and pressure, which measured by DIAL techniques. This work was financially supported by the Japan EOS Promotion Program by the MEXT Japan and System Development Program for Advanced Measurement and Analysis by the JST. Reference D. Sakaizawa, C. Nagasawa, T. Nagai, M. Abo, Y. Shibata, H. Nagai, M. Nakazato, and T. Sakai, Development of a 1.6μm differential absorption lidar with a quasi-phase-matching optical parametric oscillator and

  5. Optical skin friction measurement technique in hypersonic wind tunnel

    NASA Astrophysics Data System (ADS)

    Chen, Xing; Yao, Dapeng; Wen, Shuai; Pan, Junjie

    2016-10-01

    Shear-sensitive liquid-crystal coatings (SSLCCs) have an optical characteristic that they are sensitive to the applied shear stress. Based on this, a novel technique is developed to measure the applied shear stress of the model surface regarding both its magnitude and direction in hypersonic flow. The system of optical skin friction measurement are built in China Academy of Aerospace Aerodynamics (CAAA). A series of experiments of hypersonic vehicle is performed in wind tunnel of CAAA. Global skin friction distribution of the model which shows complicated flow structures is discussed, and a brief mechanism analysis and an evaluation on optical measurement technique have been made.

  6. Optical fiber sensing of corroded materials with evanescent wave absorption measurements

    NASA Astrophysics Data System (ADS)

    Namkung, Juock; Schwartz, Andy

    2012-06-01

    This research effort is to demonstrate a remote sensing method using optical fibers with a Fourier Transform Infrared (FTIR) interferometer as an evanescent wave spectroscopic technique. In addition to the usual advantages of optical fiber sensors, such as small size and weight, optical fibers can be embedded in aircraft structures in locations where humidity and corrosion can accumulate but cannot be directly observed. A fiber-optic-FTIR experimental setup, including several samples of field corroded materials, has been assembled to spectrally detect Aluminum Hydroxide [Al(OH)3] which is one of the major components of aluminum corrosion. Absorption spectra of Al(OH)3 have been collected using an Attenuated Total Reflection (ATR) crystal as a reference spectral signature. The absorption spectra of samples from a simulated corrosion process and from the field corroded structures have been collected and compared with the reference Al(OH)3 spectra. Chalcogenide optical fibers are used for remote sensing purposes to detect corrosion. Two distinctive absorption peaks, attributable to aluminum hydroxide, are noticed from the simulated corrosion and from the field corroded structures.

  7. First fusion proton measurements in TEXTOR plasmas using activation technique

    SciTech Connect

    Bonheure, G.; Wassenhove, G. Van; Mlynar, J.; Hult, M.; Gonzalez de Orduna, R.; Lutter, G.; Vermaercke, P.; Huber, A.; Schweer, B.; Esser, G.; Biel, W.

    2012-10-15

    MeV particle loss measurements from fusion plasmas, in particular alpha particles, remain difficult in large fusion devices and further R and D is needed for ITER. This paper describes the first attempt to measure 3 MeV escaping fusion protons emitted from TEXTOR tokamak plasmas using activation technique. This technique was successfully demonstrated, initially, in 2006 on the JET tokamak. An ion camera equipped with a collimator and several types of activation detectors was installed inside the TEXTOR vacuum vessel to perform these measurements. After irradiation, the detectors were analyzed using ultra low level gamma-ray spectrometry at the HADES underground laboratory. 3 MeV escaping fusion protons were detected in larger number -{approx}6 times more - compared to earlier measurements using this technique on JET. Another major progress was the reduction of the cooling time by a factor of 50, which made possible to detect radionuclides with half-life of less than 90 min.

  8. First fusion proton measurements in TEXTOR plasmas using activation technique.

    PubMed

    Bonheure, G; Mlynar, J; Van Wassenhove, G; Hult, M; González de Orduña, R; Lutter, G; Vermaercke, P; Huber, A; Schweer, B; Esser, G; Biel, W

    2012-10-01

    MeV particle loss measurements from fusion plasmas, in particular alpha particles, remain difficult in large fusion devices and further R&D is needed for ITER. This paper describes the first attempt to measure 3 MeV escaping fusion protons emitted from TEXTOR tokamak plasmas using activation technique. This technique was successfully demonstrated, initially, in 2006 on the JET tokamak. An ion camera equipped with a collimator and several types of activation detectors was installed inside the TEXTOR vacuum vessel to perform these measurements. After irradiation, the detectors were analyzed using ultra low level gamma-ray spectrometry at the HADES underground laboratory. 3 MeV escaping fusion protons were detected in larger number -~6 times more--compared to earlier measurements using this technique on JET. Another major progress was the reduction of the cooling time by a factor of 50, which made possible to detect radionuclides with half-life of less than 90 min.

  9. Videogrammetric Model Deformation Measurement Technique for Wind Tunnel Applications

    NASA Technical Reports Server (NTRS)

    Barrows, Danny A.

    2006-01-01

    Videogrammetric measurement technique developments at NASA Langley were driven largely by the need to quantify model deformation at the National Transonic Facility (NTF). This paper summarizes recent wind tunnel applications and issues at the NTF and other NASA Langley facilities including the Transonic Dynamics Tunnel, 31-Inch Mach 10 Tunnel, 8-Ft high Temperature Tunnel, and the 20-Ft Vertical Spin Tunnel. In addition, several adaptations of wind tunnel techniques to non-wind tunnel applications are summarized. These applications include wing deformation measurements on vehicles in flight, determining aerodynamic loads based on optical elastic deformation measurements, measurements on ultra-lightweight and inflatable space structures, and the use of an object-to-image plane scaling technique to support NASA s Space Exploration program.

  10. Water stable isotope measurements of Antarctic samples by means of IRMS and WS-CRDS techniques

    NASA Astrophysics Data System (ADS)

    Michelini, Marzia; Bonazza, Mattia; Braida, Martina; Flora, Onelio; Dreossi, Giuliano; Stenni, Barbara

    2010-05-01

    In the last years in the scientific community there has been an increasing interest for the application of stable isotope techniques to several environmental problems such as drinking water safeguarding, groundwater management, climate change, soils and paleoclimate studies etc. For example, the water stable isotopes, being natural tracers of the hydrological cycle, have been extensively used as tools to characterize regional aquifers and to reconstruct past temperature changes from polar ice cores. Here the need for improvements in analytical techniques: the high request for information calls for technologies that can offer a great quantity of analyses in short times and with low costs. Furthermore, sometimes it is difficult to obtain big amount of samples (as is the case for Antarctic ice cores or interstitial water) preventing the possibility to replicate the analyses. Here, we present oxygen and hydrogen measurements performed on water samples covering a big range of isotopic values (from very negative antarctic precipitation to mid-latitude precipitation values) carried out with both the conventional Isotope Ratio Mass Spectrometry (IRMS) technique and with a new method based on laser absorption techniques, the Wavelenght Scanned Cavity Ringdown Spectroscopy (WS-CRDS). This study is focusing on improving the precision of the measurements carried out with WS-CRDS in order to extensively apply this method to Antarctic ice core paleoclimate studies. The WS-CRDS is a variation of the CRDS developed in 1988 by O'Keef and Deacon. In CRDS a pulse of light goes through a box with high reflective inner surfaces; when there is no sample in the box the light beam doesn't find any obstacle in its path, but the reflectivity of the walls is not perfect so eventually there will be an absorption of the light beam; when the sample is injected in the box there is absorption and the difference between the time of absorption without and with sample is proportional to the quantity

  11. NO2 measurements in Hong Kong using LED based long path differential optical absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Chan, K. L.; Pöhler, D.; Kuhlmann, G.; Hartl, A.; Platt, U.; Wenig, M. O.

    2012-05-01

    In this study we present the first long term measurements of atmospheric nitrogen dioxide (NO2) using a LED based Long Path Differential Optical Absorption Spectroscopy (LP-DOAS) instrument. This instrument is measuring continuously in Hong Kong since December 2009, first in a setup with a 550 m absorption path and then with a 3820 m path at about 30 m to 50 m above street level. The instrument is using a high power blue light LED with peak intensity at 450 nm coupled into the telescope using a Y-fibre bundle. The LP-DOAS instrument measures NO2 levels in the Kowloon Tong and Mongkok district of Hong Kong and we compare the measurement results to mixing ratios reported by monitoring stations operated by the Hong Kong Environmental Protection Department in that area. Hourly averages of coinciding measurements are in reasonable agreement (R = 0.74). Furthermore, we used the long-term data set to validate the Ozone Monitoring Instrument (OMI) NO2 data product. Monthly averaged LP-DOAS and OMI measurements correlate well (R = 0.84) when comparing the data for the OMI overpass time. We analyzed weekly patterns in both data sets and found that the LP-DOAS detects a clear weekly cycle with a reduction on weekends during rush hour peaks, whereas OMI is not able to observe this weekly cycle due to its fix overpass time (13:30-14:30 LT - local time).

  12. Atmospheric extinction in solar tower plants: the Absorption and Broadband Correction for MOR measurements

    NASA Astrophysics Data System (ADS)

    Hanrieder, N.; Wilbert, S.; Pitz-Paal, R.; Emde, C.; Gasteiger, J.; Mayer, B.; Polo, J.

    2015-05-01

    Losses of reflected Direct Normal Irradiance due to atmospheric extinction in concentrating solar tower plants can vary significantly with site and time. The losses of the direct normal irradiance between the heliostat field and receiver in a solar tower plant are mainly caused by atmospheric scattering and absorption by aerosol and water vapor concentration in the atmospheric boundary layer. Due to a high aerosol particle number, radiation losses can be significantly larger in desert environments compared to the standard atmospheric conditions which are usually considered in raytracing or plant optimization tools. Information about on-site atmospheric extinction is only rarely available. To measure these radiation losses, two different commercially available instruments were tested and more than 19 months of measurements were collected at the Plataforma Solar de Almería and compared. Both instruments are primarily used to determine the meteorological optical range (MOR). The Vaisala FS11 scatterometer is based on a monochromatic near-infrared light source emission and measures the strength of scattering processes in a small air volume mainly caused by aerosol particles. The Optec LPV4 long-path visibility transmissometer determines the monochromatic attenuation between a light-emitting diode (LED) light source at 532 nm and a receiver and therefore also accounts for absorption processes. As the broadband solar attenuation is of interest for solar resource assessment for Concentrating Solar Power (CSP), a correction procedure for these two instruments is developed and tested. This procedure includes a spectral correction of both instruments from monochromatic to broadband attenuation. That means the attenuation is corrected for the actual, time-dependent by the collector reflected solar spectrum. Further, an absorption correction for the Vaisala FS11 scatterometer is implemented. To optimize the Absorption and Broadband Correction (ABC) procedure, additional

  13. [The ways of harmonization of clinical laboratory measurement techniques].

    PubMed

    Miller, W G; Myers, G L; Gantzer, M L; Kahn, S E; Schönbrunner, E R; Thienpont, L M; Bunk, D M; Christenson, R H; Eckfeldt, J H; Stanley, G L; Nubling, C M; Sturgeon, C M

    2013-02-01

    The results of implementation of different clinical laboratory techniques are to be equal in clinically significant limits to be optimally applied in diagnostics of diseases and treatment of patients. When the results of laboratory tests are not standardized and harmonized for the very same clinical assay the results can be expressed by unmatched numbers. Unfortunately, in some handbooks the values are presented based on the results of application of specific laboratory techniques without considering possibility or likelihood of differences between various techniques. When this is a case, accumulation of data of diferent clinical research studies and working out of clinical handbooks on this basis will be inconsistent. Inadequate understanding of issue that the results of laboratory tests are not standardized and harmonized can lead to incorrect clinical, financial, managerial or technical decisions. The standardization of clinical laboratory techniques was applied to many measurands related to primary referent techniques (standard specimen of pure substance) or/and developed referent measurement techniques. However, harmonization of clinical laboratory techniques for those measurands which are not related any developed measurement techniques is quite problematic due to inadequate determination of measurand, its inadequate analytical specificity, insufficient attention to commutability of referent materials and poor systematic approach to harmonization. To overcome these issues an infrastructure is to be developed to support systematic approach to identification and prioritization of measurands which are to be harmonized on the basis of clinical importance and technical applicability. The management of technical implementation harmonization process for specific measurands.

  14. Model Deformation Measurement Technique NASA Langley HSR Experiences

    NASA Technical Reports Server (NTRS)

    Burner, A. W.; Wahls, R. A.; Owens, L. R.; Goad, W. K.

    1999-01-01

    Model deformation measurement techniques have been investigated and developed at NASA's Langley Research Center. The current technique is based upon a single video camera photogrammetric determination of two dimensional coordinates of wing targets with a fixed (and known) third dimensional coordinate, namely the spanwise location. Variations of this technique have been used to measure wing twist and bending at a few selected spanwise locations near the wing tip on HSR models at the National Transonic Facility, the Transonic Dynamics Tunnel, and the Unitary Plan Wind Tunnel. Automated measurements have been made at both the Transonic Dynamics Tunnel and at Unitary Plan Wind Tunnel during the past year. Automated measurements were made for the first time at the NTF during the recently completed HSR Reference H Test 78 in early 1996. A major problem in automation for the NTF has been the need for high contrast targets which do not exceed the stringent surface finish requirements. The advantages and limitations (including targeting) of the technique as well as the rationale for selection of this particular technique are discussed. Wing twist examples from the HSR Reference H model are presented to illustrate the run-to-run and test-to-test repeatability of the technique in air mode at the NTF. Examples of wing twist in cryogenic nitrogen mode at the NTF are also presented.

  15. Fluorescence measurements for evaluating the application of multivariate analysis techniques to optically thick environments.

    SciTech Connect

    Reichardt, Thomas A.; Timlin, Jerilyn Ann; Jones, Howland D. T.; Sickafoose, Shane M.; Schmitt, Randal L.

    2010-09-01

    Laser-induced fluorescence measurements of cuvette-contained laser dye mixtures are made for evaluation of multivariate analysis techniques to optically thick environments. Nine mixtures of Coumarin 500 and Rhodamine 610 are analyzed, as well as the pure dyes. For each sample, the cuvette is positioned on a two-axis translation stage to allow the interrogation at different spatial locations, allowing the examination of both primary (absorption of the laser light) and secondary (absorption of the fluorescence) inner filter effects. In addition to these expected inner filter effects, we find evidence that a portion of the absorbed fluorescence is re-emitted. A total of 688 spectra are acquired for the evaluation of multivariate analysis approaches to account for nonlinear effects.

  16. High quality x-ray absorption spectroscopy measurements with long energy range at high pressure using diamond anvil cell

    SciTech Connect

    Hong, X.; Newville, M.; Prakapenka, V.B.; Rivers, M.L.; Sutton, S.R.

    2009-07-31

    We describe an approach for acquiring high quality x-ray absorption fine structure (XAFS) spectroscopy spectra with wide energy range at high pressure using diamond anvil cell (DAC). Overcoming the serious interference of diamond Bragg peaks is essential for combining XAFS and DAC techniques in high pressure research, yet an effective method to obtain accurate XAFS spectrum free from DAC induced glitches has been lacking. It was found that these glitches, whose energy positions are very sensitive to the relative orientation between DAC and incident x-ray beam, can be effectively eliminated using an iterative algorithm based on repeated measurements over a small angular range of DAC orientation, e.g., within {+-}3{sup o} relative to the x-ray beam direction. Demonstration XAFS spectra are reported for rutile-type GeO{sub 2} recorded by traditional ambient pressure and high pressure DAC methods, showing similar quality at 440 eV above the absorption edge. Accurate XAFS spectra of GeO{sub 2} glass were obtained at high pressure up to 53 GPa, providing important insight into the structural polymorphism of GeO{sub 2} glass at high pressure. This method is expected be applicable for in situ XAFS measurements using a diamond anvil cell up to ultrahigh pressures.

  17. Model studies of laser absorption computed tomography for remote air pollution measurement

    NASA Technical Reports Server (NTRS)

    Wolfe, D. C., Jr.; Byer, R. L.

    1982-01-01

    Model studies of the potential of laser absorption-computed tomography are presented which demonstrate the possibility of sensitive remote atmospheric pollutant measurements, over kilometer-sized areas, with two-dimensional resolution, at modest laser source powers. An analysis of this tomographic reconstruction process as a function of measurement SNR, laser power, range, and system geometry, shows that the system is able to yield two-dimensional maps of pollutant concentrations at ranges and resolutions superior to those attainable with existing, direct-detection laser radars.

  18. Note: Measurement of saturable absorption by intense vacuum ultraviolet free electron laser using fluorescent material.

    PubMed

    Inubushi, Y; Yoneda, H; Higashiya, A; Ishikawa, T; Kimura, H; Kumagai, T; Morimoto, S; Nagasono, M; Ohashi, H; Sato, F; Tanaka, T; Togashi, T; Tono, K; Yabashi, M; Yamaguchi, Y; Kodama, R

    2010-03-01

    Advances in free electron lasers (FELs) which generate high energy photons are expected to open novel nonlinear optics in the x-ray and vacuum ultraviolet (VUV) regions. In this paper, we report a new method for performing VUV-FEL focusing experiments. A VUV-FEL was focused with Kirkpatrick-Baez optics on a multilayer target, which contains fused silica as a fluorescent material. By measuring the fluorescence, a 5.6x4.9 microm(2) focal spot was observed in situ. Fluorescence was used to measure the saturable absorption of VUV pulses in the tin layer. The transmission increases nonlinearly higher with increasing laser intensity.

  19. [Measurement of trace elements in blood serum by atomic absorption spectroscopy with electrothermal atomization].

    PubMed

    Rogul'skiĭ, Iu V; Danil'chenko, S N; Lushpa, A P; Sukhodub, L F

    1997-09-01

    Describes a method for measuring trace elements Cr, Mn, Co, Fe, Cu, Zn, and Mo in the blood serum using non-flame atomization (KAC 120.1 complex). Optimal conditions for preparing the samples were defined, temperature regimens for analysis of each element selected, and original software permitting automated assays created. The method permits analysis making use of the minimal samples: 0.1 ml per 10 parallel measurements, which is 100 times less than needed for atomic absorption spectroscopy with flame atomization of liquid samples. Metrological characteristics of the method are assessed.

  20. Development of a Pulsed 2-Micron Integrated Path Differential Absorption Lidar for CO2 Measurement

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Yu, Jirong; Petros, Mulugeta; Refaat, Tamer; Refaat, Tamer

    2013-01-01

    Atmospheric carbon dioxide (CO2) is an important greenhouse gas that significantly contributes to the carbon cycle and global radiation budget on Earth. Active remote sensing of CO2 is important to address several limitations that contend with passive sensors. A 2-micron double-pulsed, Integrated Path Differential Absorption (IPDA) lidar instrument for ground and airborne atmospheric CO2 concentration measurements via direct detection method is being developed at NASA Langley Research Center. This active remote sensing instrument will provide an alternate approach of measuring atmospheric CO2 concentrations with significant advantages. A high energy pulsed approach provides high-precision measurement capability by having high signal-to-noise ratio level and unambiguously eliminates the contamination from aerosols and clouds that can bias the IPDA measurement. Commercial, on the shelf, components are implemented for the detection system. Instrument integration will be presented in this paper as well as a background for CO2 measurement at NASA Langley research Center