Science.gov

Sample records for absorbed blackbody model

  1. Radiative cooling of solar absorbers using a visibly transparent photonic crystal thermal blackbody

    PubMed Central

    Zhu, Linxiao; Raman, Aaswath P.; Fan, Shanhui

    2015-01-01

    A solar absorber, under the sun, is heated up by sunlight. In many applications, including solar cells and outdoor structures, the absorption of sunlight is intrinsic for either operational or aesthetic considerations, but the resulting heating is undesirable. Because a solar absorber by necessity faces the sky, it also naturally has radiative access to the coldness of the universe. Therefore, in these applications it would be very attractive to directly use the sky as a heat sink while preserving solar absorption properties. Here we experimentally demonstrate a visibly transparent thermal blackbody, based on a silica photonic crystal. When placed on a silicon absorber under sunlight, such a blackbody preserves or even slightly enhances sunlight absorption, but reduces the temperature of the underlying silicon absorber by as much as 13 °C due to radiative cooling. Our work shows that the concept of radiative cooling can be used in combination with the utilization of sunlight, enabling new technological capabilities. PMID:26392542

  2. Radiative cooling of solar absorbers using a visibly transparent photonic crystal thermal blackbody.

    PubMed

    Zhu, Linxiao; Raman, Aaswath P; Fan, Shanhui

    2015-10-06

    A solar absorber, under the sun, is heated up by sunlight. In many applications, including solar cells and outdoor structures, the absorption of sunlight is intrinsic for either operational or aesthetic considerations, but the resulting heating is undesirable. Because a solar absorber by necessity faces the sky, it also naturally has radiative access to the coldness of the universe. Therefore, in these applications it would be very attractive to directly use the sky as a heat sink while preserving solar absorption properties. Here we experimentally demonstrate a visibly transparent thermal blackbody, based on a silica photonic crystal. When placed on a silicon absorber under sunlight, such a blackbody preserves or even slightly enhances sunlight absorption, but reduces the temperature of the underlying silicon absorber by as much as 13 °C due to radiative cooling. Our work shows that the concept of radiative cooling can be used in combination with the utilization of sunlight, enabling new technological capabilities.

  3. Variable Temperature Blackbodies via Variable Conductance: Thermal Design, Modelling and Testing

    NASA Astrophysics Data System (ADS)

    Melzack, N.; Jones, E.; Peters, D. M.; Hurley, J. G.; Watkins, R. E. J.; Fok, S.; Sawyer, C.; Marchetaux, G.; Acreman, A.; Winkler, R.; Lowe, D.; Theocharous, T.; Montag, V.; Gibbs, D.; Pearce, A. B.; Bishop, G.; Newman, E.; Keen, S.; Stokes, J.; Pearce, A.; Stamper, R.; Cantell-Hynes, A.

    2017-02-01

    This paper presents the overall design for large (˜ 400 mm aperture) reference blackbody cavities currently under development at the Science and Technology Facilities Council Rutherford Appleton Laboratory Space Department (STFC RAL Space), in collaboration with the National Physical Laboratory (NPL). These blackbodies are designed to operate in vacuum over a temperature range from 160 K to 370 K, with an additional capability to operate at ˜ 100 K as a point of near-zero radiance. This is a challenging problem for a single blackbody. The novel thermal design presented in this paper enables one target that can physically achieve and operate successfully at both thermal extremes, whilst also meeting stringent temperature gradient requirements. The overall blackbody design is based upon a helium gas-gap heat switch and modified to allow for variable thermal conductance. The blackbody design consists of three main concentric cylinder components—an inner cavity (aluminium alloy), a radiation shield (aluminium) and an outer liquid nitrogen (LN2) jacket (stainless steel). The internal surface of the cavity is the effective radiating surface. There is a helium gas interspace surrounding the radiation shield and enclosed by the LN2 jacket and the inner cavity. The blackbodies are now at a mature stage of development. In this paper, the overall design, focusing upon the thermal design solution, is detailed. This paper will also concern the full-scale prototype breadboard model, for which results on thermal stability, spatial gradients and other sensitivities will be presented.

  4. Blackbody radiation: rosetta stone of heat bath models

    NASA Astrophysics Data System (ADS)

    O'Connell, R. F.

    2007-06-01

    The radiation field can be regarded as a collection of independent harmonic oscillators and, as such, constitutes a heat bath. Moreover, the known form of its interaction with charged particles provides a "rosetta stone" for deciding on and interpreting the correct interaction for the more general case of a quantum particle in an external potential and coupled to an arbitrary heat bath. In particular, combining QED with the machinery of stochastic physics, enables the usual scope of applications to be widened. We discuss blackbody radiation effects on: the equation of motion of a radiating electron (obtaining an equation of motion which is free from runaway solutions), anomalous diffusion, the spreading of a Gaussian wave packet, and decoherence effects due to zero-point oscillations. In addition, utilizing a formula we obtained for the free energy of an oscillator in a heat bath, enables us to determine all the quantum thermodynamic functions of interest (particularly in the areas of quantum information and nanophysics where small systems are involved) and from which we obtain temperature dependent Lamb shifts, quantum effects on the entropy at low temperature and implications for Nernst's law.

  5. Black-body radiation, emissivity, and absorptivity

    NASA Astrophysics Data System (ADS)

    Strojnik, M.; Scholl, M. K.; Garcia-Torales, G.

    2016-09-01

    We review theoretical considerations that give rise to the blackbody radiation inside a cavity with completely absorbing walls at a specific temperature. We examine the applicability of this model to the experimentally observed properties of radiation sources. We assess relevance of emissivity and its far-reaching implications. We examine its changing nature and measurement challenges

  6. Lasant Materials for Blackbody-Pumped Lasers

    NASA Technical Reports Server (NTRS)

    Deyoung, R. J. (Editor); Chen, K. Y. (Editor)

    1985-01-01

    Blackbody-pumped solar lasers are proposed to convert sunlight into laser power to provide future space power and propulsion needs. There are two classes of blackbody-pumped lasers. The direct cavity-pumped system in which the lasant molecule is vibrationally excited by the absorption of blackbody radiation and laser, all within the blackbody cavity. The other system is the transfer blackbody-pumped laser in which an absorbing molecule is first excited within the blackbody cavity, then transferred into a laser cavity when an appropriate lasant molecule is mixed. Collisional transfer of vibrational excitation from the absorbing to the lasing molecule results in laser emission. A workshop was held at NASA Langley Research Center to investigate new lasant materials for both of these blackbody systems. Emphasis was placed on the physics of molecular systems which would be appropriate for blackbody-pumped lasers.

  7. Vibrational excitation of CO by blackbody radiation

    NASA Astrophysics Data System (ADS)

    Arriola, L.; Wilson, J. W.

    1985-09-01

    Lasers excited by blackbody radiation are of interest for power beaming applications in space. In such a system sunlight is collected and focused into a blackbody cavity, heating it to approximately 2000 K. An appropriate absorbing molecule is vibrationally heated but not translationally heated when passed through the blackbody cavity. The vibrationally excited gas is then mixed with a lasant resulting in laser emission. The number density of CO molecules within a blackbody radiation field of a given temperature and pressure is calculated. Such calculations show the degree of excitation achievable, under ideal conditions, from blackbody pumping.

  8. A Simple Geometrical Model for Calculation of the Effective Emissivity in Blackbody Cylindrical Cavities

    NASA Astrophysics Data System (ADS)

    De Lucas, Javier

    2015-03-01

    A simple geometrical model for calculating the effective emissivity in blackbody cylindrical cavities has been developed. The back ray tracing technique and the Monte Carlo method have been employed, making use of a suitable set of coordinates and auxiliary planes. In these planes, the trajectories of individual photons in the successive reflections between the cavity points are followed in detail. The theoretical model is implemented by using simple numerical tools, programmed in Microsoft Visual Basic for Application and Excel. The algorithm is applied to isothermal and non-isothermal diffuse cylindrical cavities with a lid; however, the basic geometrical structure can be generalized to a cylindro-conical shape and specular reflection. Additionally, the numerical algorithm and the program source code can be used, with minor changes, for determining the distribution of the cavity points, where photon absorption takes place. This distribution could be applied to the study of the influence of thermal gradients on the effective emissivity profiles, for example. Validation is performed by analyzing the convergence of the Monte Carlo method as a function of the number of trials and by comparison with published results of different authors.

  9. High-temperature miniature blackbody radiation sources.

    PubMed

    Chernin, S M

    1997-03-01

    Various high-temperature blackbody sources for quantitative energy measurements in the IR spectral region are developed. Techniques that ensure a stable operation of the sources at high temperatures are described. The developed blackbody models with maximum temperatures of 2000, 2500, and 3000 K can also operate at other temperatures. Graphite is used as a material for radiators. These blackbodies can be used successfully in radiometric measurements in UV and visible spectral ranges. Blackbodies as high-brightness sources may find wide application in solving the problems of multipass spectroscopy. The blackbody sources developed as rocket engineering has progressed have remained outside the knowledge of foreign scientists.

  10. Illuminating the Blackbody

    ERIC Educational Resources Information Center

    Lehoucq, Roland

    2011-01-01

    The blackbody is one of the first topics the students face at the beginning of their studies on modern physics. The usual framework supposes that a blackbody emits radiation in a 3D space in the form of massless bosons (photons). This paper investigates the blackbody radiation in a more general context in order to discuss the physical hypotheses…

  11. A Blackbody Is Not a Blackbox

    ERIC Educational Resources Information Center

    Smerlak, Matteo

    2011-01-01

    We discuss carefully the "blackbody approximation", stressing what it is (a limit case of radiative transfer), and what it is not (the assumption that the body is perfectly absorbing, namely "black"). Furthermore, we derive the Planck spectrum without enclosing the field in a box, as is done in most textbooks. Although convenient, this trick…

  12. A blackbody is not a blackbox

    NASA Astrophysics Data System (ADS)

    Smerlak, Matteo

    2011-09-01

    We discuss carefully the blackbody approximation, stressing what it is (a limit case of radiative transfer), and what it is not (the assumption that the body is perfectly absorbing, namely black). Furthermore, we derive the Planck spectrum without enclosing the field in a box, as is done in most textbooks. Although convenient, this trick conceals the nature of the idealization expressed in the concept of a blackbody: first, the most obvious examples of approximate blackbodies, stars, are definitely not enclosed in boxes; second, the Planck spectrum is continuous, while the stationary modes of radiation in a box are discrete. Our derivation, although technically less elementary, is conceptually more consistent, and brings the opportunity to introduce to advanced undergraduate and graduate students the important concept of the local density of states via the resolvent formalism.

  13. Blackbody Radiation from Isolated Neptunes

    NASA Astrophysics Data System (ADS)

    Ginzburg, Sivan; Sari, Re'em; Loeb, Abraham

    2016-05-01

    Recent analyses of the orbits of some Kuiper belt objects hypothesize the presence of an undiscovered Neptune-size planet at a very large separation from the Sun. The energy budget of Neptunes on such distant orbits is dominated by the internal heat released by their cooling rather than solar irradiation (making them effectively “isolated”). The blackbody radiation that these planets emit as they cool may provide the means for their detection. Here, we use an analytical toy model to study the cooling and radiation of isolated Neptunes. This model can translate a detection (or a null detection) to a constraint on the size and composition of the hypothesized “Planet Nine.” Specifically, the thick gas atmosphere of Neptune-like planets serves as an insulating blanket that slows down their cooling. Therefore, a measurement of the blackbody temperature, {T}{{eff}}˜ 50 {{K}}, at which a Neptune emits, can be used to estimate the mass of its atmosphere, {M}{{atm}}. Explicitly, we find the relation {T}{{eff}}\\propto {M}{{atm}}1/12. Despite this weak relation, a measurement of the flux at the Wien tail can constrain the atmospheric mass, at least to within a factor of a few, and provide useful limits to possible formation scenarios of these planets. Finally, we constrain the size and composition of Planet Nine by combining our model with the null results of recent all-sky surveys.

  14. Vibration absorber modeling for handheld machine tool

    NASA Astrophysics Data System (ADS)

    Abdullah, Mohd Azman; Mustafa, Mohd Muhyiddin; Jamil, Jazli Firdaus; Salim, Mohd Azli; Ramli, Faiz Redza

    2015-05-01

    Handheld machine tools produce continuous vibration to the users during operation. This vibration causes harmful effects to the health of users for repeated operations in a long period of time. In this paper, a dynamic vibration absorber (DVA) is designed and modeled to reduce the vibration generated by the handheld machine tool. Several designs and models of vibration absorbers with various stiffness properties are simulated, tested and optimized in order to diminish the vibration. Ordinary differential equation is used to derive and formulate the vibration phenomena in the machine tool with and without the DVA. The final transfer function of the DVA is later analyzed using commercial available mathematical software. The DVA with optimum properties of mass and stiffness is developed and applied on the actual handheld machine tool. The performance of the DVA is experimentally tested and validated by the final result of vibration reduction.

  15. Conversion of blackbody radiation into laser energy

    NASA Astrophysics Data System (ADS)

    McInville, R. M.; Hassan, H. A.

    1982-06-01

    By employing detailed kinetic models, three concepts which utilize a blackbody cavity for the conversion of solar energy into laser energy using a CO2 lasant are analyzed and compared. In the first, the blackbody radiation is used to excite flowing CO2 directly. The second and third employ a mixing laser concept with CO and N2 being the donor gases. The CO is optically pumped while thermal heating excites the N2. Blackbody temperatures ranging from 1500 deg K - 2500 deg K are considered. Based on calculated laser power output per unit flow rate of CO2, it appears that the N2-CO2 mixing laser is the most attractive system.

  16. Microwave blackbodies for spaceborne receivers

    NASA Technical Reports Server (NTRS)

    Stacey, J. M.

    1985-01-01

    The properties of microwave blackbody targets are explained as they apply to the calibration of spaceborne receivers. Also described are several practicable, blackbody targets used to test and calibrate receivers in the laboratory and in the thermal vacuum chamber. Problems with the precision and the accuracy of blackbody targets, and blackbody target design concepts that overcome some of the accuracy limitations present in existing target designs, are presented. The principle of the Brewster angle blackbody target is described where the blackbody is applied as a fixed-temperature test target in the laboratory and as a variable-temperature target in the thermal vacuum chamber. The reflectivity of a Brewster angle target is measured in the laboratory. From this measurement, the emissivity of the target is calculated. Radiatively cooled thermal suspensions are discussed as the coolants of blackbody targets and waveguide terminations that function as calibration devices in spaceborne receivers. Examples are given for the design of radiatively cooled thermal suspensions. Corrugated-horn antennas used to observe the cosmic background and to provide a cold-calibration source for spaceborne receivers are described.

  17. Modelling and validation of electromechanical shock absorbers

    NASA Astrophysics Data System (ADS)

    Tonoli, Andrea; Amati, Nicola; Girardello Detoni, Joaquim; Galluzzi, Renato; Gasparin, Enrico

    2013-08-01

    Electromechanical vehicle suspension systems represent a promising substitute to conventional hydraulic solutions. However, the design of electromechanical devices that are able to supply high damping forces without exceeding geometric dimension and mass constraints is a difficult task. All these challenges meet in off-road vehicle suspension systems, where the power density of the dampers is a crucial parameter. In this context, the present paper outlines a particular shock absorber configuration where a suitable electric machine and a transmission mechanism are utilised to meet off-road vehicle requirements. A dynamic model is used to represent the device. Subsequently, experimental tests are performed on an actual prototype to verify the functionality of the damper and validate the proposed model.

  18. Lorentz transformation of blackbody radiation.

    PubMed

    Ford, G W; O'Connell, R F

    2013-10-01

    We present a simple calculation of the Lorentz transformation of the spectral distribution of blackbody radiation at temperature T. Here we emphasize that T is the temperature in the blackbody rest frame and does not change. We thus avoid the confused and confusing question of how temperature transforms. We show by explicit calculation that at zero temperature the spectral distribution is invariant. At finite temperature we find the well-known result familiar in discussions of the 2.7 K cosmic radiation.

  19. Blackbody Theory for Hyperbolic Materials.

    PubMed

    Biehs, Svend-Age; Lang, Slawa; Petrov, Alexander Yu; Eich, Manfred; Ben-Abdallah, Philippe

    2015-10-23

    The blackbody theory is revisited in the case of thermal electromagnetic fields inside uniaxial anisotropic media in thermal equilibrium with a heat bath. When these media are hyperbolic, we show that the spectral energy density of these fields radically differs from that predicted by Planck's blackbody theory and that the maximum of the spectral energy density determined by Wien's law is redshifted. Finally, we derive the Stefan-Boltzmann law for hyperbolic media which becomes a quadratic function of the heat bath temperature.

  20. A shock absorber model for structure-borne noise analyses

    NASA Astrophysics Data System (ADS)

    Benaziz, Marouane; Nacivet, Samuel; Thouverez, Fabrice

    2015-08-01

    Shock absorbers are often responsible for undesirable structure-borne noise in cars. The early numerical prediction of this noise in the automobile development process can save time and money and yet remains a challenge for industry. In this paper, a new approach to predicting shock absorber structure-borne noise is proposed; it consists in modelling the shock absorber and including the main nonlinear phenomena responsible for discontinuities in the response. The model set forth herein features: compressible fluid behaviour, nonlinear flow rate-pressure relations, valve mechanical equations and rubber mounts. The piston, base valve and complete shock absorber model are compared with experimental results. Sensitivity of the shock absorber response is evaluated and the most important parameters are classified. The response envelope is also computed. This shock absorber model is able to accurately reproduce local nonlinear phenomena and improves our state of knowledge on potential noise sources within the shock absorber.

  1. Microscopic modeling of nitride intersubband absorbance

    NASA Astrophysics Data System (ADS)

    Montano, Ines; Allerman, A. A.; Wierer, J. J.; Moseley, M.; Skogen, E. J.; Tauke-Pedretti, A.; Vawter, G. A.

    III-nitride intersubband structures have recently attracted much interest because of their potential for a wide variety of applications ranging from electro-optical modulators to terahertz quantum cascade lasers. To overcome present simulation limitations we have developed a microscopic absorbance simulator for nitride intersubband devices. Our simulator calculates the band structure of nitride intersubband systems using a fully coupled 8x8 k.p Hamiltonian and determines the material response of a single period in a density-matrix-formalism by solving the Heisenberg equation including many-body and dephasing contributions. After calculating the polarization due to intersubband transitions in a single period, the resulting absorbance of a superlattice structure including radiative coupling between the different periods is determined using a non-local Green's-function formalism. As a result our simulator allows us to predict intersubband absorbance of superlattice structures with microscopically determined lineshapes and linewidths accounting for both many-body and correlation contributions. This work is funded by Sandia National Laboratories Laboratory Directed Research and Development program. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin.

  2. Blackbody comparator for thermocouple calibration

    SciTech Connect

    Ojanen, M.; Hahtela, O. M.; Heinonen, M.

    2013-09-11

    MIKES is developing a measurement set-up for calibrating thermocouples in the temperature range 960 °C - 1500 °C. The calibration method is based on direct comparison of thermocouples and radiation thermometers. We have designed a graphite blackbody comparator cell, which is operated in a horizontal single-zone tube furnace. The cell includes two blackbody cavities for radiation temperature measurements. The cavities have openings on opposite sides of the cell, allowing simultaneous measurement with two radiation thermometers. The design of the comparator allows three thermocouples to be calibrated simultaneously. The thermocouples to be calibrated are inserted in thermometer wells around one of the measurement cavities. We characterize the blackbody comparator in terms of repeatability, temperature distribution and emissivity. Finally, we validate the uncertainty analysis by comparing calibration results obtained for type B and S thermocouples to the calibration results reported by Technical Research Institute of Sweden (SP), and MIKES. The agreement in the temperature range 1000 °C - 1500 °C is within 0.90 °C, the average deviation being 0.17 °C.

  3. Exergy of Blackbody Radiation and Monochromatic Photon

    NASA Astrophysics Data System (ADS)

    Zhou, Zhijun; Shan, Shiquan; Chen, Liping; Zhang, Yanwei

    2017-04-01

    The study of radiation exergy has important significance for solar energy and high-temperature engineering. In this paper, several exergy expressions of blackbody radiation were discussed and the differences between Petela's expression of exergy and two other expressions were analyzed. Considering that radiant energy and thermal energy are different, the radiation machine model was established; furthermore, the validity of Petela's formula was indicated by this model. Based on the concept of radiation equivalent temperature, the integral form expression of monochromatic photon exergy was put forward by establishing the infinite-staged Carnot heat engine model. At the same time, an approximate relation between equivalent temperature and radiation wavelength was given. The error of this relation is negligible when calculating the exergy of blackbody radiation within the temperature range of the engineering field. Finally, the monochromatic photon entropy was discussed by considering the infinite-staged Carnot heat engine model, and an expression of photon entropy with integral form was given. The monochromatic photon entropy and exergy proposed in our paper satisfy the thermodynamic relation and can reflect the differences between radiant energy and thermal energy.

  4. Resonant circuit model for efficient metamaterial absorber.

    PubMed

    Sellier, Alexandre; Teperik, Tatiana V; de Lustrac, André

    2013-11-04

    The resonant absorption in a planar metamaterial is studied theoretically. We present a simple physical model describing this phenomenon in terms of equivalent resonant circuit. We discuss the role of radiative and dissipative damping of resonant mode supported by a metamaterial in the formation of absorption spectra. We show that the results of rigorous calculations of Maxwell equations can be fully retrieved with simple model describing the system in terms of equivalent resonant circuit. This simple model allows us to explain the total absorption effect observed in the system on a common physical ground by referring it to the impedance matching condition at the resonance.

  5. Blackbody cavity radiometer has rapid response

    NASA Technical Reports Server (NTRS)

    Haley, F. C.

    1966-01-01

    Fast response, spectrally linear standard detector in the form of a blackbody cavity radiometer calibrates rapidly responding photodetectors against a calibrated standard detector. A power amplifier with maximum available gain reduces error signal without stability loss. It may be used as a blackbody radiator by manipulation of the bridge variable arm.

  6. mbb_emcee: Modified Blackbody MCMC

    NASA Astrophysics Data System (ADS)

    Conley, Alexander

    2016-02-01

    Mbb_emcee fits modified blackbodies to photometry data using an affine invariant MCMC. It has large number of options which, for example, allow computation of the IR luminosity or dustmass as part of the fit. Carrying out a fit produces a HDF5 output file containing the results, which can either be read directly, or read back into a mbb_results object for analysis. Upper and lower limits can be imposed as well as Gaussian priors on the model parameters. These additions are useful for analyzing poorly constrained data. In addition to standard Python packages scipy, numpy, and cython, mbb_emcee requires emcee (ascl:1303.002), Astropy (ascl:1304.002), h5py, and for unit tests, nose.

  7. Scaling blackbody laser to high powers

    NASA Technical Reports Server (NTRS)

    Deyoung, R. J.

    1985-01-01

    Lasers pumped by solar heated blackbody cavities have potential for multimegawatt power beaming in space. There are two basic types of blackbody lasers; cavity pumped and transfer system. The transfer system is judged to be more readily scalable to high power. In this system, either N2 or CO is heated by the blackbody cavity then transferred into the laser cavity where CO2 is injected. The N2-CO2 system was demonstrated, but probably has lower efficiency than the CO-CO system. The characteristics of potential transfer laser systems are outlined.

  8. Experimental and Numerical Characterization of a Steady-State Cylindrical Blackbody Cavity at 1100 Degrees Celsius

    NASA Technical Reports Server (NTRS)

    Horn, Thomas J.; Abdelmessih, Amanie N.

    2000-01-01

    A blackbody calibration furnace at the NASA Dryden Flight Research Center is used to calibrate heat flux gages. These gages are for measuring the aerodynamic heat flux on hypersonic flight vehicle surfaces. The blackbody is a graphite tube with a midplane partition which divides the tube into two compartments (dual cavities). Electrical resistance heating is used to heat the graphite tube. This heating and the boundary conditions imposed on the graphite tube result in temperature gradients along the walls of the blackbody cavity. This paper describes measurements made during steady-state operation and development of finite-difference thermal models of the blockbody furnace at 1100 C. Two configurations were studied, one with the blackbody outer surface insulated and the other without insulation. The dominant modes of heat transfer were identified for each configuration and the effect of variations in material properties and electric current that was passed through the blackbody were quantified.

  9. Anisotropy of the cosmic blackbody radiation

    NASA Technical Reports Server (NTRS)

    Wilkinson, D. T.

    1986-01-01

    The universe is filled with thermal radiation having a current temperature of 2.75 K. Originating in the very early universe, this radiation furnishes strong evidence that the Big Bang cosmology best describes our expanding universe from an incredibly hot, compacted early stage until now. The model can be used to extrapolate our physics backward in time to predict events whose effects might be observable in the 2.75 K radiation today. The spectrum and isotropy are being studied with sophisticated microwave radiometers on the ground, in balloons, and in satellites. The results are as predicted by the simple theory: the spectrum is that of a blackbody (to a few percent) and the radiation is isotropic (to 0.01 percent) except for a local effect due to our motion through the radiation. However, a problem is emerging. Primordial fluctuations in the mass density, which later became the great clusters of galaxies that we see today, should have left an imprint on the 2.75 K radiation - bumpiness on the sky at angular scales of about 10 arc minutes. They have not been seen.

  10. Anisotropy of the cosmic blackbody radiation.

    PubMed

    Wilkinson, D T

    1986-06-20

    The universe is filled with thermal radiation having a current temperature of 2.75 K. Originating in the very early universe, this radiation furnishes strong evidence that the Big Bang cosmology best describes our expanding universe from an incredibly hot, compacted early stage until now. The model can be used to extrapolate our physics backward in time to predict events whose effects might be observable in the 2.75 K radiation today. The spectrum and isotropy are being studied with sophisticated microwave radiometers on the ground, in balloons, and in satellites. The results are as predicted by the simple theory: the spectrum is that of a blackbody (to a few percent) and the radiation is isotropic (to 0.01 percent) except for a local effect due to our motion through the radiation. However, a problem is emerging. Primordial fluctuations in the mass density, which later became the great clusters of galaxies that we see today, should have left an imprint on the 2.75 K radiation-bumpiness on the sky at angular scales of about 10 arc minutes. They have not yet been seen.

  11. Soft versus hard X-ray emission in active galactic nuclei: partial-covering and warm-plus-cold absorber models

    NASA Astrophysics Data System (ADS)

    Ceballos, M. T.; Barcons, X.

    1996-09-01

    We analyse the ROSAT Position Sensitive Proportional Counter (PSPC) hardness ratio and the 0.5-2-keV to 2-10-keV flux ratio of 65 active galactic nuclei (AGN) for which there are both ROSAT archival observations available and 2-10-keV fluxes, mostly from the HEAO-1 MC-LASS survey. We conclude that the simplest spectral model for the AGN that can accommodate the variety of X-ray colours obtained is a standard power law (with energy spectral index alpha~0.9) plus a ~0.1-keV blackbody, both of which are partially absorbed. In our sample, type 1 AGN require an absorbing column around 10^22 cm^-2 with covering fractions between 20 and 100 per cent, while type 2 AGN display larger columns and ~100 per cent coverage. This simple model also provides a good link between soft and hard AGN X-ray luminosity functions and source counts. We also consider a warm absorber as an alternative model to partial covering and find that the presence of gas in two phases (ionized and neutral) is required.

  12. Material Model Evaluation of a Composite Honeycomb Energy Absorber

    NASA Technical Reports Server (NTRS)

    Jackson, Karen E.; Annett, Martin S.; Fasanella, Edwin L.; Polanco, Michael A.

    2012-01-01

    A study was conducted to evaluate four different material models in predicting the dynamic crushing response of solid-element-based models of a composite honeycomb energy absorber, designated the Deployable Energy Absorber (DEA). Dynamic crush tests of three DEA components were simulated using the nonlinear, explicit transient dynamic code, LS-DYNA . In addition, a full-scale crash test of an MD-500 helicopter, retrofitted with DEA blocks, was simulated. The four material models used to represent the DEA included: *MAT_CRUSHABLE_FOAM (Mat 63), *MAT_HONEYCOMB (Mat 26), *MAT_SIMPLIFIED_RUBBER/FOAM (Mat 181), and *MAT_TRANSVERSELY_ANISOTROPIC_CRUSHABLE_FOAM (Mat 142). Test-analysis calibration metrics included simple percentage error comparisons of initial peak acceleration, sustained crush stress, and peak compaction acceleration of the DEA components. In addition, the Roadside Safety Verification and Validation Program (RSVVP) was used to assess similarities and differences between the experimental and analytical curves for the full-scale crash test.

  13. On the parameters of absorbing layers for shallow water models

    NASA Astrophysics Data System (ADS)

    Modave, Axel; Deleersnijder, Éric; Delhez, Éric J. M.

    2010-02-01

    Absorbing/sponge layers used as boundary conditions for ocean/marine models are examined in the context of the shallow water equations with the aim to minimize the reflection of outgoing waves at the boundary of the computational domain. The optimization of the absorption coefficient is not an issue in continuous models, for the reflection coefficient of outgoing waves can then be made as small as we please by increasing the absorption coefficient. The optimization of the parameters of absorbing layers is therefore a purely discrete problem. A balance must be found between the efficient damping of outgoing waves and the limited spatial resolution with which the resulting spatial gradients must be described. Using a one-dimensional model as a test case, the performances of various spatial distributions of the absorption coefficient are compared. Two shifted hyperbolic distributions of the absorption coefficient are derived from theoretical considerations for a pure propagative and a pure advective problems. These distribution show good performances. Their free parameter has a well-defined interpretation and can therefore be determined on a physical basis. The properties of the two shifted hyperbolas are illustrated using the classical two-dimensional problems of the collapse of a Gaussian-shaped mound of water and of its advection by a mean current. The good behavior of the resulting boundary scheme remains when a full non-linear dynamics is taken into account.

  14. Reanalysis of high-resolution XMM-Newton data of V2491 Cygni using models of collisionally ionized hot absorbers

    NASA Astrophysics Data System (ADS)

    Balman, Ş.; Gamsızkan, Ç.

    2017-02-01

    Aims: We model spectral absorption features in data of the high-resolution XMM-Newton Reflection Grating Spectrometer. Methods: We performed X-ray spectral analysis and modeling using the SRON software SPEX version 2.05.04. Results: We present a reanalysis of data obtained with the XMM-Newton Reflection Grating Spectrometer of the classical nova V2491 Cyg from two different pointings, 40 d and 50 d after outburst. We aim to model absorption components in the high-resolution spectra independently of the continuum model. To model the complex absorption, we used hot collisionally ionized (in equilibrium) absorber models along with interstellar absorption (of gas and dust origin separately) that we discuss in the light of observations. For an adequate approximation and to facilitate the fitting procedures, we used a blackbody model for the continuum. We find blackbody temperatures in the range 61-91 eV (slightly variable over the two observations) that yield a white dwarf (WD) mass of 1.15-1.3 M⊙ assuming this range is the maximum temperature achieved during the H-burning phase. Our fits model the ionized absorption features simultaneously, thus calculating a global velocity shift for the absorption component in the data originating from the nova wind and/or ejecta as a result of collisionally ionized hot absorption. We derive two different hot-absorber components from our fits with blueshifts yielding 2900-3800 km s-1 for the first (day 40) and 2600-3600 km s-1 for the second observation 50 days after outburst that are consistent with ejecta or wind speeds. The two collisionally ionized hot-absorption components have temperatures kT1 ≃ 1.0-3.6 keV and kT2 ≃ 0.4-0.87 keV with rms velocities σv1 872 km s-1 and σv2 56 km s-1. These are consistent with shock temperatures in the X-ray wavelengths. V2491 Cyg shows signature of H-burning with underabundant carbon C/C⊙ = 0.3-0.5, and enhanced nitrogen N/N⊙ = 5-7 and oxygen O/O⊙ = 16-43. The high oxygen

  15. Modeling the Effect of Polychromatic Light in Quantitative Absorbance Spectroscopy

    ERIC Educational Resources Information Center

    Smith, Rachel; Cantrell, Kevin

    2007-01-01

    Laboratory experiment is conducted to give the students practical experience with the principles of electronic absorbance spectroscopy. This straightforward approach creates a powerful tool for exploring many of the aspects of quantitative absorbance spectroscopy.

  16. Frequency Integrated Radiation Models for Absorbing and Scattering Media

    NASA Technical Reports Server (NTRS)

    Ripoll, J. F.; Wray, A. A.

    2004-01-01

    The objective of this work is to contribute to the simplification of existing radiation models used in complex emitting, absorbing, scattering media. The application in view is the computation of flows occurring in such complex media, such as certain stellar interiors or combusting gases. In these problems, especially when scattering is present, the complexity of the radiative transfer leads to a high numerical cost, which is often avoided by simply neglecting it. The complexity lies partly in the strong dependence of the spectral coefficients on frequency. Models are then needed to capture the effects of the radiation when one cannot afford to directly solve for it. In this work, the frequency dependence will be modeled and integrated out in order retain only the average effects. A frequency-integrated radiative transfer equation (RTE) will be derived.

  17. Numerical study of persistence in models with absorbing states

    NASA Astrophysics Data System (ADS)

    Albano, Ezequiel V.; Muñoz, Miguel A.

    2001-03-01

    Extensive Monte Carlo simulations are performed in order to evaluate both the local (θl) and global (θg) persistence exponents in the Ziff-Gulari-Barshad (ZGB) [Phys. Rev. Lett. 56, 2553 (1986)] irreversible reaction model. At the second-order irreversible phase transition (IPT) we find that both the local and the global persistence exhibit power-law behavior with a crossover between two different time regimes. On the other hand, at the ZGB first-order IPT, active sites are short lived and the persistence decays more abruptly; it is not clear whether it shows power-law behavior or not. In order to analyze universality issues, we have also studied another model with absorbing states, the contact process, and evaluated the local persistence exponent in dimensions from 1 to 4. A striking apparent superuniversality is reported: the local persistence exponent seems to coincide in both one- and two-dimensional systems. Some other aspects of persistence in systems with absorbing states are also analyzed.

  18. Numerical study of persistence in models with absorbing states.

    PubMed

    Albano, E V; Muñoz, M A

    2001-03-01

    Extensive Monte Carlo simulations are performed in order to evaluate both the local (straight theta(l)) and global (straight theta(g)) persistence exponents in the Ziff-Gulari-Barshad (ZGB) [Phys. Rev. Lett. 56, 2553 (1986)] irreversible reaction model. At the second-order irreversible phase transition (IPT) we find that both the local and the global persistence exhibit power-law behavior with a crossover between two different time regimes. On the other hand, at the ZGB first-order IPT, active sites are short lived and the persistence decays more abruptly; it is not clear whether it shows power-law behavior or not. In order to analyze universality issues, we have also studied another model with absorbing states, the contact process, and evaluated the local persistence exponent in dimensions from 1 to 4. A striking apparent superuniversality is reported: the local persistence exponent seems to coincide in both one- and two-dimensional systems. Some other aspects of persistence in systems with absorbing states are also analyzed.

  19. Absorbed Dose and Dose Equivalent Calculations for Modeling Effective Dose

    NASA Technical Reports Server (NTRS)

    Welton, Andrew; Lee, Kerry

    2010-01-01

    While in orbit, Astronauts are exposed to a much higher dose of ionizing radiation than when on the ground. It is important to model how shielding designs on spacecraft reduce radiation effective dose pre-flight, and determine whether or not a danger to humans is presented. However, in order to calculate effective dose, dose equivalent calculations are needed. Dose equivalent takes into account an absorbed dose of radiation and the biological effectiveness of ionizing radiation. This is important in preventing long-term, stochastic radiation effects in humans spending time in space. Monte carlo simulations run with the particle transport code FLUKA, give absorbed and equivalent dose data for relevant shielding. The shielding geometry used in the dose calculations is a layered slab design, consisting of aluminum, polyethylene, and water. Water is used to simulate the soft tissues that compose the human body. The results obtained will provide information on how the shielding performs with many thicknesses of each material in the slab. This allows them to be directly applicable to modern spacecraft shielding geometries.

  20. Blackbody Radiation from an Incandescent Lamp

    ERIC Educational Resources Information Center

    Ribeiro, C. I.

    2014-01-01

    In this article we propose an activity aimed at introductory students to help them understand the Stefan-Boltzmann and Wien's displacement laws. It only requires simple materials that are available at any school: an incandescent lamp, a variable dc energy supply, and a computer to run an interactive simulation of the blackbody spectrum.…

  1. Circuit modeling of graphene absorber in terahertz band

    NASA Astrophysics Data System (ADS)

    Taghvaee, Hamid Reza; Nasari, Hadiseh; Abrishamian, Mohammad Sadegh

    2017-01-01

    Here we develop and extend a transmission line method (TLM) to analyze the performance of graphene assisted metamaterial (GM) devices working in the terahertz (THz) band. We demonstrate that a circuit model can be presented for different parts of the device including graphene and also the patterned metallic sheet by analyzing the distribution of surface induced current. In pursuit of evaluating the efficiency and accuracy of our proposed method, we compare its results, obtained from an easy to implement MATLAB code for a typical GM absorber with those obtained from full wave simulations. The excellence of the proposed method in terms of computation time (showing more than 3 orders of magnitude reduction in run time) and memory resource besides producing results with acceptable agreement with the results of full wave simulation (with an error less than 5%) versus incident angle, dielectric thickness and chemical potential, nominates it as a promising approach to simulate other graphene-based devices.

  2. Traffic model with an absorbing-state phase transition

    NASA Astrophysics Data System (ADS)

    Iannini, M. L. L.; Dickman, Ronald

    2017-02-01

    We consider a modified Nagel-Schreckenberg (NS) model in which drivers do not decelerate if their speed is smaller than the headway (number of empty sites to the car ahead). (In the original NS model, such a reduction in speed occurs with probability p , independent of the headway, as long as the current speed is greater than zero.) In the modified model the free-flow state (with all vehicles traveling at the maximum speed, vmax) is absorbing for densities ρ smaller than a critical value ρc=1 /(vmax+2 ) . The phase diagram in the ρ -p plane is reentrant: for densities in the range ρc ,<<ρ <ρc , both small and large values of p favor free flow, while for intermediate values, a nonzero fraction of vehicles have speeds model. Our results suggest an unexpected connection between traffic models and stochastic sandpiles.

  3. Nonlinear modeling of magnetorheological energy absorbers under impact conditions

    NASA Astrophysics Data System (ADS)

    Mao, Min; Hu, Wei; Choi, Young-Tai; Wereley, Norman M.; Browne, Alan L.; Ulicny, John; Johnson, Nancy

    2013-11-01

    Magnetorheological energy absorbers (MREAs) provide adaptive vibration and shock mitigation capabilities to accommodate varying payloads, vibration spectra, and shock pulses, as well as other environmental factors. A key performance metric is the dynamic range, which is defined as the ratio of the force at maximum field to the force in the absence of field. The off-state force is typically assumed to increase linearly with speed, but at the higher shaft speeds occurring in impact events, the off-state damping exhibits nonlinear velocity squared damping effects. To improve understanding of MREA behavior under high-speed impact conditions, this study focuses on nonlinear MREA models that can more accurately predict MREA dynamic behavior for nominal impact speeds of up to 6 m s-1. Three models were examined in this study. First, a nonlinear Bingham-plastic (BP) model incorporating Darcy friction and fluid inertia (Unsteady-BP) was formulated where the force is proportional to the velocity. Second, a Bingham-plastic model incorporating minor loss factors and fluid inertia (Unsteady-BPM) to better account for high-speed behavior was formulated. Third, a hydromechanical (HM) analysis was developed to account for fluid compressibility and inertia as well as minor loss factors. These models were validated using drop test data obtained using the drop tower facility at GM R&D Center for nominal drop speeds of up to 6 m s-1.

  4. Nonlinear dynamic model for magnetically-tunable Galfenol vibration absorbers

    NASA Astrophysics Data System (ADS)

    Scheidler, Justin J.; Dapino, Marcelo J.

    2013-03-01

    This paper presents a single degree of freedom model for the nonlinear vibration of a metal-matrix composite manufactured by ultrasonic additive manufacturing that contains seamlessly embedded magnetostrictive Galfenol alloys (FeGa). The model is valid under arbitrary stress and magnetic field. Changes in the composite's natural frequency are quantified to assess its performance as a semi-active vibration absorber. The effects of Galfenol volume fraction and location within the composite on natural frequency are quantified. The bandwidth over which the composite's natural frequency can be tuned with a bias magnetic field is studied for varying displacement excitation amplitudes. The natural frequency is tunable for all excitation amplitudes considered, but the maximum tunability occurs below an excitation amplitude threshold of 1 × 10-6 m for the composite geometry considered. Natural frequency shifts between 6% and 50% are found as the Galfenol volume fraction varies from 25% to 100% when Galfenol is located at the composite neutral axis. At a modest 25% Galfenol by volume, the model shows that up to 15% shifts in composite resonance are possible through magnetic bias field modulation if Galfenol is embedded away from the composite midplane. As the Galfenol volume fraction and distance between Galfenol and composite midplane are increased, linear and quadratic increases in tunability result, respectively.

  5. Center frequency formulation of the blackbody radiation spectrum

    NASA Astrophysics Data System (ADS)

    Plendl, Johannes N.; Plendl, Hans S.

    1989-11-01

    A center frequency law of blackbody radiation is derived using the analogy between the blackbody radiation curve and the corresponding resonance curve. The formula is then used to calculate the Stefan-Boltzmann radiation constant, which is in better agreement with the best available experimentally determined values than the value derived from Planck's blackbody formula.

  6. Atomic clocks with suppressed blackbody radiation shift.

    PubMed

    Yudin, V I; Taichenachev, A V; Okhapkin, M V; Bagayev, S N; Tamm, Chr; Peik, E; Huntemann, N; Mehlstäubler, T E; Riehle, F

    2011-07-15

    We develop a concept of atomic clocks where the blackbody radiation shift and its fluctuations can be suppressed by 1-3 orders of magnitude independent of the environmental temperature. The suppression is based on the fact that in a system with two accessible clock transitions (with frequencies ν1 and ν2) which are exposed to the same thermal environment, there exists a "synthetic" frequency ν(syn) ∝ (ν1 - ε12ν2) largely immune to the blackbody radiation shift. For example, in the case of 171Yb+ it is possible to create a synthetic-frequency-based clock in which the fractional blackbody radiation shift can be suppressed to the level of 10(-18) in a broad interval near room temperature (300±15  K). We also propose a realization of our method with the use of an optical frequency comb generator stabilized to both frequencies ν1 and ν2, where the frequency ν(syn) is generated as one of the components of the comb spectrum.

  7. Characteristic Model of a Shock Absorber in an Unmanned Ground Vehicle

    NASA Astrophysics Data System (ADS)

    Danko, Ján; Milesich, Tomáš; Bugár, Martin; Madarás, Juraj

    2012-12-01

    The paper deals with mathematical models for the shock absorber of an unmanned ground vehicle. The possibility of mathematically modeling the shock absorber is discussed. Specific types of mathematical models are described and the experimental measurement of a shock absorber is made. For modeling the characteristics of the shock absorber the modified Bouc-Wen model (Spencer model) is selected. From the mathematical model, a simulation model in Matlab/Simulink is created. The identification of the Spencer model parameters is performed and force-velocity and force-displacement characteristics of the shock absorber of an unmanned ground vehicle is made. In the conclusions, the simulated characteristics are verified and evaluated by the measured characteristics.

  8. A robust absorbing layer method for anisotropic seismic wave modeling

    SciTech Connect

    Métivier, L.; Brossier, R.; Labbé, S.; Operto, S.; Virieux, J.

    2014-12-15

    When applied to wave propagation modeling in anisotropic media, Perfectly Matched Layers (PML) exhibit instabilities. Incoming waves are amplified instead of being absorbed. Overcoming this difficulty is crucial as in many seismic imaging applications, accounting accurately for the subsurface anisotropy is mandatory. In this study, we present the SMART layer method as an alternative to PML approach. This method is based on the decomposition of the wavefield into components propagating inward and outward the domain of interest. Only outgoing components are damped. We show that for elastic and acoustic wave propagation in Transverse Isotropic media, the SMART layer is unconditionally dissipative: no amplification of the wavefield is possible. The SMART layers are not perfectly matched, therefore less accurate than conventional PML. However, a reasonable increase of the layer size yields an accuracy similar to PML. Finally, we illustrate that the selective damping strategy on which is based the SMART method can prevent the generation of spurious S-waves by embedding the source in a small zone where only S-waves are damped.

  9. Modeling a semiconductor laser with an intracavity atomic absorber

    SciTech Connect

    Masoller, C.; Vilaseca, R.; Oria, M.

    2009-07-15

    The dynamics of a semiconductor laser with an intracavity atomic absorber is studied numerically. The study is motivated by the experiments of Barbosa et al. [Opt. Lett. 32, 1869 (2007)], using a semiconductor junction as an active medium, with its output face being antireflection coated, and a cell containing cesium vapor placed in a cavity that was closed by a diffraction grating (DG). The DG allowed scanning the lasing frequency across the D{sub 2} line in the Cs spectrum, and different regimes such as frequency bistability or dynamic instability were observed depending on the operating conditions. Here we propose a rate-equation model that takes into account the dispersive losses and the dispersive refractive index change in the laser cavity caused by the presence of the Cs vapor cell. These effects are described through a modification of the complex susceptibility. The numerical results are found to be in qualitative good agreement with some of the observations; however, some discrepancies are also noticed, which can be attributed to multi-longitudinal-mode emission in the experiments. The simulations clearly show the relevant role of the Lamb dips and crossover resonances, which arise on top of the Doppler-broadened D{sub 2} line in the Cs spectrum, and are due to the forward and backward intracavity fields interacting resonantly with the Cs atoms. When the laser frequency is locked in a dip, a reduction in the frequency noise and of the intensity noise is demonstrated.

  10. A New Approach to Blackbody Radiation

    NASA Astrophysics Data System (ADS)

    Cahill, M. E.

    2003-12-01

    The current model of blackbody radiation, due to Planck, Bose & Einstein (PBE theory), has been remarkably accurate and valuable in Astronomy & Physics. It is possible to make several improvements in the treatment of the radiation which agree well with PBE theory for most of the energy range but which differ at the low and high energy ends of the distribution. First it is possible to obtain an explicit microcanonical distribution for the radiation. The distribution has the form dn = kN(1-x)3N-4x2dx, k-1= int ∑ 01 (1-x) 3N-4x2dx, x=\\varepsilon)/(E) where E is the total energy, \\varepsilon is the energy of interest, x is a unitless energy, N is the total number of photons and dn is the number of photons with energy x in range dx. The parameter N is not deternimed by the microcanonical method. It is also possible to determine an improved most probable distribution based on BE statistics using photon populations of cells in 6 dimensional phase space. This requires not using the Stirling approximation in the derivation since a finite total number of photons implies that most of the cells in an infinite phase space will be empty. The cell size, phase space number density, phase space volume element, the thermodynamic permutability and the number of cells in an element are given by C = Ω h3, ρ ' = C(dn)/(dw), dw=V4π p2dp, ln(P) = ∫ ln (Ω -1+ρ')/(Ω -1) (ρ' dC, dC = (dw)/(C) The distribution follows from making the permutability a maximum for arbitrary variations in photon number density with fixed total energy δ (ln(P)-β E) = 0 ==> D(Ω -1+ρ ') - D(ρ ') = ɛ , D(x) = (dln(x!))/(dx), ɛ = β ǎrepsilon The distributions differ from PBE for they have energy cutoffs (indicated by a c subscript) and for large N ǎrepsilonc ˜ lnN, ǎrepsilonc' = γ +D(Ω -1) ˜ lnΩ showing that the cells have N Planck bins. The distributions differ from each other because there is no infinite photon density at 0 energy in the more fundamental microcanonical distribution. If

  11. Modeling of Liquid Film along Absorber Cylinders in an Absorption Chiller

    NASA Astrophysics Data System (ADS)

    Suzuki, Hiroshi; Yamanaka, Tomofumi; Nagamoto, Wataru; Sugiyama, Takahide

    A two-dimensional liquid film model of LiBr solution falling along absorber cylinders has been studied to obtain boundary conditions for computing vapor flow in the absorber-evaporator of an absorption chiller. The model was established based on the assumptions that LiBr concentration and temperature profiles in the liquid film obey the third order polynomial expressions. It was indicated that mass flux and absorbed heat on the liquid surface can be calculated with simple numerical computations on the present analytical model. The overall heat transfer coefficient and total absorbed mass per second calculated with the present liquid film model was compared with experimental data for validation. The results calculated with the present model showed good agreement with the experimental data. Then, it was concluded the present model was useful enough for determining surface conditions on the LiBr liquid film around absorber cylinders.

  12. Performance verification of the Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS) on-board blackbody calibration system

    NASA Astrophysics Data System (ADS)

    Best, Fred A.; Revercomb, Henry E.; Tobin, David C.; Knuteson, Robert O.; Taylor, Joseph K.; Thielman, Donald J.; Adler, Douglas P.; Werner, Mark W.; Ellington, Scott D.; Elwell, John D.; Scott, Deron K.; Cantwell, Gregory W.; Bingham, Gail E.; Smith, William L.

    2006-12-01

    The NASA New Millennium Program's Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS) instrument was designed to provide enormous advances in water vapor, wind, temperature, and trace gas profiling from geostationary orbit. The top-level instrument calibration requirement is to measure brightness temperature to better than 1 K (3 sigma) over a broad range of atmospheric brightness temperatures, with a reproducibility of +/-0.2 K. For the onboard calibration approach used by GIFTS that employs two internal blackbody sources (290 K and 255 K) plus a space view sequenced at regular programmable intervals, this instrument level requirement places tight requirements on the blackbody temperature uncertainty (0.1 K) and emissivity uncertainty (0.001). The blackbody references are cavities that follow the UW Atmospheric Emitted Radiance Interferometer (AERI) design, scaled to the GIFTS beam size. The engineering model blackbody system was completed and fully calibrated at the University of Wisconsin and delivered for integration into the GIFTS Engineering Development Unit (EDU) at the Utah State Space Dynamics Laboratory. This paper presents a detailed description of the methodology used to establish the required temperature and emissivity performance, with emphasis on the traceability to NIST standards. In addition, blackbody temperature data are presented from the GIFTS EDU thermal vacuum tests that indicate excellent temperature stability. The delivered on-board blackbody calibration system exceeds performance goals - the cavity spectral emissivity is better than 0.998 with an absolute uncertainty of less than 0.001, and the absolute blackbody temperature uncertainty is better than 0.06 K.

  13. SETI at the cosmic blackbody radiation peak

    NASA Astrophysics Data System (ADS)

    Vallee, J. P.

    1990-11-01

    Roughly two-thirds of the past 50 SETI studies have concentrated in or near the 'Water Hole' frequencies (between 18 cm and 21 cm wave-length), with no success so far. Gott (1982) proposed an alternative, namely to look at the frequency where the peak of the 2.735 K Cosmic Blackbody Radiation (CBR) is located. An update is presented here on what little has been done so far there, and on what could be done in the 1990s with current receiver technology.

  14. Irradiance from stars based on blackbody theory

    NASA Technical Reports Server (NTRS)

    Jacobs, W. A.

    1984-01-01

    A computer program which calculates a theoretical backbody curve for a star when given only the star's temperature and visual magnitude is presented. The program was written to produce approximate stellar spectra to be used in the design of the Space Telescope Fine Guidance System (FGS). In addition to the blackbody curve, the program calculates the number of photons tht would be received by the Space Telescope per 25 MSEC interval in wavelength increments of 0.2 microns. The equations used for the computations work best for stars that emit primarily in the range of near infrared to ultraviolet.

  15. Blackbody radiation shifts in optical atomic clocks.

    PubMed

    Safronova, Marianna; Kozlov, Mikhail; Clark, Charles

    2012-03-01

    A review of recent theoretical calculations of blackbody radiation (BBR) shifts in optical atomic clocks is presented. We summarize previous results for monovalent ions that were obtained by a relativistic all-order single-double method, where all single and double excitations of the Dirac- Fock wave function are included to all orders of perturbation theory. A recently developed method for accurate calculations of BBR shifts in divalent atoms is then presented. This approach combines the relativistic all-order method and the configuration interaction method, which provides for accurate treatment of correlation corrections in atoms with two valence electrons. Calculations of the BBR shifts in B+, Al+, and In+ have enabled us to reduce the present fractional uncertainties in the frequencies of their clock transitions as measured at room temperature: to 4 × 10-19 for Al+ and 10-18 for B+ and In+. These uncertainties approach recent estimates of the limits of precision of currently proposed optical atomic clocks. We discuss directions of future theoretical developments for reducing clock uncertainties resulting from blackbody radiation shifts.

  16. Numerical modeling of incline plate LiBr absorber

    NASA Astrophysics Data System (ADS)

    Karami, Shahram; Farhanieh, Bijan

    2011-03-01

    Among major components of LiBr-H2O absorption chillers is the absorber, which has a direct effect on the chillier size and whose characteristics have significant effects on the overall efficiency of absorption machines. In this article, heat and mass transfer process in absorption of refrigerant vapor into a lithium bromide solution of water-cooled incline plate absorber in the Reynolds number range of 5 < Re < 150 is performed numerically. The boundary layer assumptions are used for the mass, momentum and energy transport equations and the fully implicit finite difference method is employed to solve the governing equations. Dependence of lithium bromide aqueous properties to the temperature and concentration is employed as well as dependence of film thickness to vapor absorption. An analysis for linear distribution of wall temperature condition carries out to investigate the reliability of the present numerical method through comparing with previous investigation. The effect of plate angle on heat and mass transfer parameters is investigated and the results show that absorption mass flux and heat and mass transfer coefficient increase as the angle of the plate increase. The main parameters of absorber design, namely Nusselt and Sherwood numbers, are correlated as a function of Reynolds Number and the plate angle.

  17. Superspace Cavity QED Blackbody Equilibrium Modes Delineating CMBR Emission and Non-Doppler Redshift Absorption

    NASA Astrophysics Data System (ADS)

    Amoroso, Richard

    2004-05-01

    A blackbody equilibrium cavity QED theory for CMBR as emission and non-Doppler redshift as absorption is formulated utilizing an advanced form of Einstein's steady state cosmology. This Continuous State Universe (CSU) is based on a highly ordered periodic superspace that includes an energy dependent spacetime metric. The formalism for the superspace is derived by extending the Wheeler-Feynman absorber theory of radiation to the topology of the 12D periodic superspace. A fundamental least unit contains a core of Dirac spherical rotation with an inherent continuous compactification and dimensional reduction. It is shown formally that parameters of this cosmology demonstrate blackbody equilibrium conditions compatible with modes of emission and absorption suitable for describing CMBR and non-Doppler redshift.

  18. Freshwater DOM quantity and quality from a two-component model of UV absorbance

    USGS Publications Warehouse

    Carter, Heather T.; Tipping, Edward; Koprivnjak, Jean-Francois; Miller, Matthew P.; Cookson, Brenda; Hamilton-Taylor, John

    2012-01-01

    We present a model that considers UV-absorbing dissolved organic matter (DOM) to consist of two components (A and B), each with a distinct and constant spectrum. Component A absorbs UV light strongly, and is therefore presumed to possess aromatic chromophores and hydrophobic character, whereas B absorbs weakly and can be assumed hydrophilic. We parameterised the model with dissolved organic carbon concentrations [DOC] and corresponding UV spectra for c. 1700 filtered surface water samples from North America and the United Kingdom, by optimising extinction coefficients for A and B, together with a small constant concentration of non-absorbing DOM (0.80 mg DOC L-1). Good unbiased predictions of [DOC] from absorbance data at 270 and 350 nm were obtained (r2 = 0.98), the sum of squared residuals in [DOC] being reduced by 66% compared to a regression model fitted to absorbance at 270 nm alone. The parameterised model can use measured optical absorbance values at any pair of suitable wavelengths to calculate both [DOC] and the relative amounts of A and B in a water sample, i.e. measures of quantity and quality. Blind prediction of [DOC] was satisfactory for 9 of 11 independent data sets (181 of 213 individual samples).

  19. Bistable limit cycles in a model for a laser with a saturable absorber

    SciTech Connect

    Antoranz, J.C.; Bonilla, L.L.; Gea, J.; Velarde, M.G.

    1982-07-05

    Sufficiently long population decay times and sufficiently short dipole decay times in a single-mode model for a laser with saturable absorber permit coexistence of soft-excited oscillations and Q switching (hard-mode sustained relaxation oscillations).

  20. Vacuum Processing Technique for Development of Primary Standard Blackbodies

    PubMed Central

    Navarro, M.; Bruce, S. S.; Johnson, B. Carol; Murthy, A. V.; Saunders, R. D.

    1999-01-01

    Blackbody sources with nearly unity emittance that are in equilibrium with a pure freezing metal such as gold, silver, or copper are used as primary standard sources in the International Temperature Scale of 1990 (ITS-90). Recently, a facility using radio-frequency induction heating for melting and filling the blackbody crucible with the freeze metal under vacuum conditions was developed at the National Institute of Standards and Technology (NIST). The blackbody development under a vacuum environment eliminated the possibility of contamination of the freeze metal during the process. The induction heating, compared to a resistively heated convection oven, provided faster heating of crucible and resulted in shorter turn-around time of about 7 h to manufacture a blackbody. This paper describes the new facility and its application to the development of fixed-point blackbodies.

  1. Comparison of Blackbody Sources for Low-Temperature IR Calibration

    NASA Astrophysics Data System (ADS)

    Ljungblad, S.; Holmsten, M.; Josefson, L. E.; Klason, P.

    2015-12-01

    Radiation thermometers are traditionally mostly used in high-temperature applications. They are, however, becoming more common in different applications at room temperature or below, in applications such as monitoring frozen food and evaluating heat leakage in buildings. To measure temperature accurately with a pyrometer, calibration is essential. A problem with traditional, commercially available, blackbody sources is that ice is often formed on the surface when measuring temperatures below 0°C. This is due to the humidity of the surrounding air and, as ice does not have the same emissivity as the blackbody source, it biases the measurements. An alternative to a traditional blackbody source has been tested by SP Technical Research Institute of Sweden. The objective is to find a cost-efficient method of calibrating pyrometers by comparison at the level of accuracy required for the intended use. A disc-shaped blackbody with a surface pyramid pattern is placed in a climatic chamber with an opening for field of view of the pyrometer. The temperature of the climatic chamber is measured with two platinum resistance thermometers in the air in the vicinity of the disc. As a rule, frost will form only if the deposition surface is colder than the surrounding air, and, as this is not the case when the air of the climatic chamber is cooled, there should be no frost or ice formed on the blackbody surface. To test the disc-shaped blackbody source, a blackbody cavity immersed in a conventional stirred liquid bath was used as a reference blackbody source. Two different pyrometers were calibrated by comparison using the two different blackbody sources, and the results were compared. The results of the measurements show that the disc works as intended and is suitable as a blackbody radiation source.

  2. Propagation of partially coherent twisted anisotropic Gaussian Schell-model beams in dispersive and absorbing media.

    PubMed

    Cai, Yangjian; Lin, Qiang; Ge, Di

    2002-10-01

    By adopting a new tensor method, we derived an analytical propagation formula for the cross-spectral density of partially coherent twisted anisotropic Gaussian Schell-model (GSM) beams through dispersive and absorbing media. Using the derived formula, we studied the evolution properties and spectrum properties of twisted anisotropic GSM beams in dispersive and absorbing media. The results show that the dispersive and absorbing media have strong influences on the propagation properties of twisted anisotropic GSM beams and their spectrum evolution. Our method provides a simple and convenient way to study the propagation of twisted anisotropic GSM beams in media with complex refractive index.

  3. Compton scattering of blackbody photons by relativistic electrons

    NASA Astrophysics Data System (ADS)

    Zdziarski, Andrzej A.; Pjanka, Patryk

    2013-12-01

    We present simple and accurate analytical formulas for the rates of Compton scattering by relativistic electrons integrated over the energy distribution of blackbody seed photons. Both anisotropic scattering, in which blackbody photons arriving from one direction are scattered by an anisotropic electron distribution into another direction, and scattering of isotropic seed photons are considered. Compton scattering by relativistic electrons off blackbody photons from either stars or cosmic microwave background takes place, in particular, in microquasars, colliding-wind binaries, supernova remnants, interstellar medium and the vicinity of the Sun.

  4. Exact research on the theory of the blackbody thermal radiation

    PubMed Central

    Yang, Xin; Wei, Bing

    2016-01-01

    After studying the normalized Planck equation in depth, a brand-new type of spectrum curves of blackbody thermal radiation is given. Two important parameters of the new type curves, namely relative width RWη and symmetric factor RSFη, are defined. The paper points out that the experimental verification of the parameters has three significant applications: (1) Giving a method to measure temperature by detecting the radiation wavelength. (2) Determining the blackbody grade. (3) The temperature obtained from the law of the blackbody thermal radiation can be used as a criterion. PMID:27876795

  5. Development and application of a thermoelectric cooler extended area blackbody

    NASA Astrophysics Data System (ADS)

    Zhang, Ya-zhou; Sun, Xian-zhong; Lei, Hao; Zhang, Jin

    2016-11-01

    Calibration is important to the application of infrared camera. For improving low temperature infrared measurement accuracy. A small extend blackbody is specially designed to meeting the requirement of low temperature calibration. The temperature range of blackbody is 5° 90° with effective radiation area 150mm×150mm.The design adopts thermoelectric cooler as driver and chooses the PID temperature control algorithm. By testing the stability, emissivity and uniformity of blackbody, the design is proved quiet practical, which meets the needs of infrared camera, spectrometer and other measuring equipment in low temperature calibration.

  6. Determining the integrated cavity emissivity of blackbody furnaces

    NASA Astrophysics Data System (ADS)

    Wu, Quansheng; Chen, Yinghang; Chu, Zaixiang; Li, Bijuan

    1989-06-01

    An apparatus has been constructed for determining the integrated cavity emissivity of blackbody furnace simulators near 500 K and for calibrating infrared detectors. A difference-ratio method is described for measuring the radiant emission characteristics of the simulator by using a high-quality heat-pipe blackbody as a standard radiant source operated at 500 K and a water-immersed cavity as a reference source operated at a lower temperature. It is verified that the total uncertainties of the method are less than 0.6% for determining the integrated cavity emissivity and 0.5% for determining irradiance from the 500-K standard blackbody on the detectors.

  7. Exact research on the theory of the blackbody thermal radiation

    NASA Astrophysics Data System (ADS)

    Yang, Xin; Wei, Bing

    2016-11-01

    After studying the normalized Planck equation in depth, a brand-new type of spectrum curves of blackbody thermal radiation is given. Two important parameters of the new type curves, namely relative width RWη and symmetric factor RSFη, are defined. The paper points out that the experimental verification of the parameters has three significant applications: (1) Giving a method to measure temperature by detecting the radiation wavelength. (2) Determining the blackbody grade. (3) The temperature obtained from the law of the blackbody thermal radiation can be used as a criterion.

  8. DISCOVERY OF SMOOTHLY EVOLVING BLACKBODIES IN THE EARLY AFTERGLOW OF GRB 090618: EVIDENCE FOR A SPINE–SHEATH JET?

    SciTech Connect

    Basak, Rupal; Rao, A. R. E-mail: arrao@tifr.res.in

    2015-10-20

    GRB 090618 is a bright gamma-ray burst (GRB) with multiple pulses. It shows evidence of thermal emission in the initial pulses as well as in the early afterglow phase. Because high-resolution spectral data from the Swift/X-ray Telescope (XRT) are available for the early afterglow, we investigate the shape and evolution of the thermal component in this phase using data from the Swift/Burst Alert Telescope (BAT), the Swift/XRT, and the Fermi/Gamma-ray Burst Monitor detectors. An independent fit to the BAT and XRT data reveals two correlated blackbodies with monotonically decreasing temperatures. Hence, we investigated the combined data with a model consisting of two blackbodies and a power law (2BBPL), a model suggested for several bright GRBs. We elicit the following interesting features of the 2BBPL model: (1) the same model is applicable from the peak of the last pulse in the prompt emission to the afterglow emission, (2) the ratio of temperatures and the fluxes of the two blackbodies remains constant throughout the observations, (3) the blackbody temperatures and fluxes show a monotonic decrease with time, with the BB fluxes dropping about a factor of two faster than that of the power-law (PL) emission, and (4) attributing the blackbody emission to photospheric emissions, we find that the photospheric radii increase very slowly with time, and the lower-temperature blackbody shows a larger emitting radius than that of the higher-temperature blackbody. We find some evidence that the underlying shape of the nonthermal emission is a cutoff power law rather than a PL. We sketch a spine–sheath jet model to explain our observations.

  9. Wideband filter radiometers for blackbody temperature measurements

    NASA Astrophysics Data System (ADS)

    Boivin, L. P.; Bamber, C.; Gaertner, A. A.; Gerson, R. K.; Woods, D. J.; Woolliams, E. R.

    2010-10-01

    The use of high-temperature blackbody (HTBB) radiators to realize primary spectral irradiance scales requires that the operating temperature of the HTBB be accurately determined. We have developed five filter radiometers (FRs) to measure the temperature of the National Research Council of Canada's HTBB. The FRs are designed to minimize sensitivity to ambient temperature fluctuations. They incorporate air-spaced colored glass filters and a Si photodiode detector that are housed in a cell whose temperature is controlled to ±0.1°C by means of annular thermoelectric elements at the front and rear of the cell. These wideband filter radiometers operate in four different wavelength bands. The spectral responsivity measurements were performed in an underfill geometry for a power-mode calibration that is traceable to NRC's cryogenic radiometer. The spectral temperature sensitivity of each of these FRs has been measured. The apertures for these FRs were cold-formed by swaging machine-cut apertures onto precision dowel pins. A description of the filter radiometer design, fabrication and testing, together with a detailed uncertainty analysis, is presented. We derive the equations that relate the spectral irradiance measured by the FRs to the spectral radiance and temperature of the HTBB, and deal specifically with the change of index of refraction over the path of the radiation from the interior of the HTBB to the FRs. We believe these equations are more accurate than recently published derivations. Our measurements of the operating temperature of our HTBB working at temperatures near 2500 K, 2700 K and 2900 K, together with measurements using a pyrometer, show agreement between the five filter radiometers and with the pyrometer to within the estimated uncertainties.

  10. Blackbody Infrared Radiative Dissociation of Protonated Oligosaccharides

    NASA Astrophysics Data System (ADS)

    Fentabil, Messele A.; Daneshfar, Rambod; Kitova, Elena N.; Klassen, John S.

    2011-12-01

    The dissociation pathways, kinetics, and energetics of protonated oligosaccharides in the gas phase were investigated using blackbody infrared radiative dissociation (BIRD). Time-resolved BIRD measurements were performed on singly protonated ions of cellohexaose (Cel6), which is composed of β-(1 → 4)-linked glucopyranose rings, and five malto-oligosaccharides (Malx, where x = 4-8), which are composed of α-(1 → 4)-linked glucopyranose units. At the temperatures investigated (85-160 °C), the oligosaccharides dissociate at the glycosidic linkages or by the loss of a water molecule to produce B- or Y-type ions. The Y ions dissociate to smaller Y or B ions, while the B ions yield exclusively smaller B ions. The sequential loss of water molecules from the smallest B ions (B1 and B2) also occurs. Rate constants for dissociation of the protonated oligosaccharides and the corresponding Arrhenius activation parameters (Ea and A) were determined. The Ea and A-factors measured for protonated Malx (x > 4) are indistinguishable within error (~19 kcal mol-1, 1010 s-1), which is consistent with the ions being in the rapid energy exchange limit. In contrast, the Arrhenius parameters for protonated Cel6 (24 kcal mol-1, 1012 s-1) are significantly larger. These results indicate that both the energy and entropy changes associated with the glycosidic bond cleavage are sensitive to the anomeric configuration. Based on the results of this study, it is proposed that formation of B and Y ions occurs through a common dissociation mechanism, with the position of the proton establishing whether a B or Y ion is formed upon glycosidic bond cleavage.

  11. MODIS On-board Blackbody Performance

    NASA Technical Reports Server (NTRS)

    Xiong, Xiaoxiong; Chen, N.; Wu, A.; Wenny, B.; Dodd, J.

    2008-01-01

    Currently, there are two MODIS instruments operated on-orbit: one on-board the Terra spacecraft launched in December 1999 and the other on-board the Aqua spacecraft launched in May 2002. MODIS is a scanning radiometer that has 16 thermal emissive bands (TEBs) in the MWIR and LWIR regions. The remaining spectral bands are in the VISINIR and SWIR regions. The TEBs have a total of 160 detectors (10 detectors per band), which are calibrated on-orbit using an on-board blackbody (BB). MODIS TEB calibration is performed via a quadratic algorithm with its linear calibration coefficients updated on a scan-by-scan basis using each detector's response to the BB. The offset and nonlinear terms of the quadratic calibration equation are stored in a look-up table (LUT). The LUT parameters are derived from pre-launch calibration and updated on-orbit from BB observations, as needed. Typically, the BB is set at a fixed temperature. Periodically, a warm-up and cool-down activity is performed, which enables the BB temperature to be varied from instrument ambient up to 315K. The temperature of the BB is measured each scan using 12 thermistors, which were fully characterized pre-launch with reference to the NIST temperature scale. This paper describes MODIS on-board BB operational activities and performance. The TEB detector response (short-term stability and long-term changes) and noise characterization results derived from BB observations and their impact on the TEB calibration uncertainty are also presented.

  12. Overview and future direction for blackbody solar-pumped lasers

    NASA Technical Reports Server (NTRS)

    Deyoung, R. J.

    1988-01-01

    A review of solar-pumped blackbody lasers is given which addresses their present status and suggests future research directions. The blackbody laser concept is one system proposed to scale to multimegawatt power levels for space-to-space power transmissions for such applications as onboard spacecraft electrical or propulsion needs. Among the critical technical issues are the scalability to high powers and the laser wavelength which impacts the transmission optics size as well as the laser-to-electric converter at the receiver. Because present blackbody solar-pumped lasers will have laser wavelengths longer than 4 microns, simple photovoltaic converters cannot be used, and transmission optics will be large. Thus, future blackbody laser systems should emphasize near visible laser wavelengths.

  13. z ~ 6 metal-line absorbers as a probe of galactic feedback models

    NASA Astrophysics Data System (ADS)

    Keating, Laura C.; Puchwein, Ewald; Haehnelt, Martin G.; Bird, Simeon; Bolton, James S.

    2017-03-01

    Observations of metal absorption lines in the spectra of QSOs out to z > 6 are providing an important probe into the enrichment and ionization state of the intergalactic medium (IGM) at the tail end of reionization. Using simulations with four different feedback models, including the Illustris and Sherwood simulations, we investigate how the overall incidence rate and equivalent width distribution of metal-line absorbers varies with the galactic wind scheme. The low-ionization absorbers are reasonably insensitive to the feedback implementation, with all models reasonably close to the observed incidence rate of O i absorbers. However, all of our models struggle to reproduce the observations of C iv, which is probing overdensities close to the mean at z ~ 6, suggesting that the metals are not being transported out into the IGM efficiently enough in these simulations.

  14. Synthesis of Numerical Methods for Modeling Wave Energy Converter-Point Absorbers: Preprint

    SciTech Connect

    Li, Y.; Yu, Y. H.

    2012-05-01

    During the past few decades, wave energy has received significant attention among all ocean energy formats. Industry has proposed hundreds of prototypes such as an oscillating water column, a point absorber, an overtopping system, and a bottom-hinged system. In particular, many researchers have focused on modeling the floating-point absorber as the technology to extract wave energy. Several modeling methods have been used such as the analytical method, the boundary-integral equation method, the Navier-Stokes equations method, and the empirical method. However, no standardized method has been decided. To assist the development of wave energy conversion technologies, this report reviews the methods for modeling the floating-point absorber.

  15. On the linear elastic, isotropic modeling of poroelastic distributed vibration absorbers at low frequencies

    NASA Astrophysics Data System (ADS)

    Harne, R. L.

    2013-07-01

    Several past works have considered a passive vibration absorber device utilizing distributed mass and spring layers. The thickness of the poroelastic foam spring and the area density of the mass layer are modified to achieve a target natural frequency of the device while the foam itself provides adequate dissipation of energy as the mass dynamically compresses it at resonance. A model of the device earlier developed is briefly reviewed and validated by new experiments. The dependence of the absorber natural frequency and damping on the poroelastic spring thickness is observed in detail and is found to be consistent with past work on poroelastic material elastic characteristics outside of the linear dynamic regime. The results set a practical limit on the applicability of linearity assumptions in the present modeling of the distributed poroelastic vibration absorbers and thus determine a design parameter range for which the computationally efficient model is accurate.

  16. A MODEL FOR FINE PARTICLE AGGLOMERATION IN CIRCULATING FLUIDIZED BED ABSORBERS

    EPA Science Inventory

    A model for fine particle agglomeration in circulating fluidized bed absorbers (CFBAS) has been developed. It can model the influence of different factors on agglomeration, such as the geometry of CFBAs, superficial gas velocity, initial particle size distribution, and type of ag...

  17. NEW APPROACHES: A closer look at Planck's blackbody equation

    NASA Astrophysics Data System (ADS)

    Lawson, Duncan

    1997-09-01

    The spectral distribution of blackbody radiation is given by Planck's blackbody equation. This can be integrated across the complete spectrum to obtain the total blackbody emissive power (the Stefan - Boltzmann law). In some circumstances we shall want to investigate behaviour only in a band of the spectrum. For example, rare earth oxides which are commonly used in thermophotovoltaic devices typically emit significantly only in a single narrow band. The complexity of Planck's blackbody equation is such that it appears to require significant computing prowess to be able to obtain useful results. In a recent paper in this journal, Jain (1996) calculated the emissive power of the visible region using the high-powered mathematical software package Mathematica. The requirement of advanced numerical techniques and/or a powerful piece of software limit the range of students who can study spectral blackbody effects. However, by taking a closer look at Planck's equation we find that it is possible to learn much about spectral blackbody effects (including all of Jain's results) by careful use of mathematical techniques covered in A-level and a spreadsheet (or other simple computational tool). This opens a study of Planck's equation to all undergraduates.

  18. Modeling and validation of polyurethane based passive underwater acoustic absorber.

    PubMed

    Jayakumari, V G; Shamsudeen, Rahna K; Ramesh, R; Mukundan, T

    2011-08-01

    The acoustic behavior of an acoustically transparent polyurethane and an interpenetrating polymer network of polyurethane with polydimethyl siloxane were studied using dynamic mechanical analysis, finite element modeling, and experimental evaluation of acoustic properties in a water-filled pulse tube setup. Dynamic mechanical measurements in the temperature range -50 °C to +70 °C were carried out, and the data were used for time temperature superposition to generate material behavior at high frequencies. These inputs were used for modeling the acoustic behavior of these materials using ATILA, which is a commercial finite element code, capable of computing transmission and reflection characteristics of materials. From this data, absorption characteristics were computed. The results were compared with the experimental results obtained using a water-filled pulse tube facility.

  19. Multiscale Modelling of Small Molecules Absorbed in Zeolite-4A

    NASA Astrophysics Data System (ADS)

    Modine, N. A.; Chandross, Michael; Jaramillo, Eugenio

    2003-03-01

    Confinement within the nanoscale pores of a zeolite strongly modifies the physical and chemical behavior of small molecules such as water, ammonia, and carbon dioxide. Realistic modeling of such phenomena requires simultaneously capturing the detailed behavior of chemical bonds and the possibility of collective dynamics occurring in a complex unit cell (672 atoms in the case of Zeolite-4A). Classical simulations alone cannot reliably model the breaking and formation of chemical bonds, while quantum methods alone are incapable of treating the extended length and time scales characteristic of complex dynamics. Therefore, we have taken a mixed quantum/classical approach. We report our progress in developing an efficient algorithm for embedding a small region treated with density functional theory within a larger system represented by classical potentials. We discuss interesting initial results for the behavior of water and ammonia in Zeolite-4A. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under contract DE- AC04-94AL85000.

  20. Modelling of TES X-ray Microcalorimeters with a Novel Absorber Design

    NASA Technical Reports Server (NTRS)

    Iyomoto, Naoko; Bandler, Simon; Brefosky, Regis; Brown, Ari; Chervenak, James; Figueroa-Feliciano, Enectali; Finkbeiner, Frederick; Kelley, Richard; Kilbourne, Caroline; Lindeman, Mark; Porter, Frederick; Saab, Tarek; Sadleir, Jack; Smith, Stephen

    2007-01-01

    Our development of a novel x-ray absorber design that has enabled the incorporation of high-conductivity electroplated gold into our absorbers has yielded devices that not only have achieved breakthrough performance at 6 keV, but also are extraordinarily well modelled. We have determined device parameters that reproduce complex impedance curves and noise spectra throughout transition. Observed pulse heights, decay time and baseline energy resolution were in good agreement with simulated results using the same parameters. In the presentation, we will show these results in detail and we will also show highlights of the characterization of our gold/bismuth-absorber devices. We will discuss possible improvement of our current devices and expected performance of future devices using the modelling results.

  1. A mathematical model of the nine-month pregnant woman for calculating specific absorbed fractions

    SciTech Connect

    Watson, E.E.; Stabin, M.G.

    1986-01-01

    Existing models that allow calculation of internal doses from radionuclide intakes by both men and women are based on a mathematical model of Reference Man. No attempt has been made to allow for the changing geometric relationships that occur during pregnancy which would affect the doses to the mother's organs and to the fetus. As pregnancy progresses, many of the mother's abdominal organs are repositioned, and their shapes may be somewhat changed. Estimation of specific absorbed fractions requires that existing mathematical models be modified to accommodate these changes. Specific absorbed fractions for Reference Woman at three, six, and nine months of pregnancy should be sufficient for estimating the doses to the pregnant woman and the fetus. This report describes a model for the pregnant woman at nine months. An enlarged uterus was incorporated into a model for Reference Woman. Several abdominal organs as well as the exterior of the trunk were modified to accommodate the new uterus. This model will allow calculation of specific absorbed fractions for the fetus from photon emitters in maternal organs. Specific absorbed fractions for the repositioned maternal organs from other organs can also be calculated. 14 refs., 2 figs.

  2. Spatial heterogeneity in vegetation canopies and remote sensing of absorbed photosynthetically active radiation - A modeling study

    NASA Technical Reports Server (NTRS)

    Asrar, G.; Myneni, R. B.; Choudhury, B. J.

    1992-01-01

    A 3D radiative transfer model is used to investigate the relationship between spectral indices and fraction of absorbed photosynthetically active radiation (PAR) in horizontally heterogeneous vegetation canopies. Canopy reflection at optical wavelengths and PAR absorption are simulated. Data obtained indicate that the leaf area index of a canopy is less of an instructive parameter than the ground cover and clump leaf area index for these canopies. It is found that the relationship between the normalized difference vegetation index and fraction of absorbed PAR is almost linear and independent of spatial heterogeneity.

  3. Blackbody radiation sources for the IR spectral range

    SciTech Connect

    Ogarev, S. A.; Morozova, S. P.; Katysheva, A. A.; Lisiansky, B. E.; Samoylov, M. L.

    2013-09-11

    Metrological radiometric facilities for optoelectronic instruments calibration utilize in terms of standards as radiation detectors in a form of cryogenic radiometers (CR), so as radiation sources. However in practice, there are no CR working within IR spectral range. An alternative way of radiometric calibration in middle and far IR ranges is to develop a parametric series of standard radiation sources - blackbody (BB) models. The paper describes some of BBs developed at VNIIOFI for the last time [1] from cryogenic (80 K to 200 K), to low (about 200 K to 400 K) and medium (400 K to 700 K) temperature regions for calibration of the IR instruments under cryogenic-vacuum conditions. These BBs are presented by models of both types: variable-temperature and based on fixed points of Ga or In. BBs are characterized with high temperature uniformity and stability. Copper and aluminum alloys are used as the radiation cavity materials. The required value of emissivity ε{sub λ} is achieved by using different black coatings. Low-temperature and cryogenic BBs are based on the principles of indirect multi-zone electric heating (with heat isolation from LN2 cooling loop, or by using an external liquid thermostat with circulating heat-transfer agent. The principles of operation, design and test results of BBs are described.

  4. Isotropic photon drag: Analytic expressions for velocity (3D) and position (1D) with applications to blackbody friction

    NASA Astrophysics Data System (ADS)

    West, Joseph

    2014-03-01

    The motion of objects traveling at relativistic speeds and subject only to isotropic photon drag (blackbody friction as a special case) is modeled. The objects are assumed to be perfectly absorbing. Analytic expressions for velocity and position as a function of time for objects subject to photon drag are obtained for the case in which the photons are constrained to one-dimensional motion. If the object is also assumed to be a perfect emitter of energy, analytic expressions are found for time as a function of velocity of the body for photons constrained to one-dimensional motion, and for a full three-dimensional isotropic photon background. The derivations are carried out entirely from the point of view of a reference frame at rest relative to the isotropic photon field, so that no changes of reference frame are involved. The results for the three-dimensional model do not agree with work by previous authors, and this discrepancy is discussed. The derivations are suitable for use in the undergraduate classroom. Example cases for a light sail and a micron-sized sand grain are examined for interactions with the cosmic background radiation, assuming a temperature of 3000 K, the temperature at the time the universe became transparent, and it is found that relativistic speeds would decay on a time scale of years.

  5. Photon and electron absorbed fractions calculated from a new tomographic rat model

    NASA Astrophysics Data System (ADS)

    Peixoto, P. H. R.; Vieira, J. W.; Yoriyaz, H.; Lima, F. R. A.

    2008-10-01

    This paper describes the development of a tomographic model of a rat developed using CT images of an adult male Wistar rat for radiation transport studies. It also presents calculations of absorbed fractions (AFs) under internal photon and electron sources using this rat model and the Monte Carlo code MCNP. All data related to the developed phantom were made available for the scientific community as well as the MCNP inputs prepared for AF calculations in that phantom and also all estimated AF values, which could be used to obtain absorbed dose estimates—following the MIRD methodology—in rats similar in size to the presently developed model. Comparison between the rat model developed in this study and that published by Stabin et al (2006 J. Nucl. Med. 47 655) for a 248 g Sprague-Dawley rat, as well as between the estimated AF values for both models, has been presented.

  6. Modeling X-ray Absorbers in AGNs with MHD-Driven Accretion-Disk Winds

    NASA Astrophysics Data System (ADS)

    Fukumura, Keigo; Kazanas, D.; Shrader, C. R.; Tombesi, F.; Contopoulos, J.; Behar, E.

    2013-04-01

    We have proposed a systematic view of the observed X-ray absorbers, namely warm absorbers (WAs) in soft X-ray and highly-ionized ultra-fast outflows (UFOs), in the context of magnetically-driven accretion-disk wind models. While potentially complicated by variability and thermal instability in these energetic outflows, in this simplistic model we have calculated 2D kinematic field as well as density and ionization structure of the wind with density profile of 1/r corresponding to a constant column distribution per decade of ionization parameter. In particular we show semi-analytically that the inner layer of the disk-wind manifests itself as the strongly-ionized fast outflows while the outer layer is identified as the moderately-ionized absorbers. The computed characteristics of these two apparently distinct absorbers are consistent with X-ray data (i.e. a factor of ~100 difference in column and ionization parameters as well as low wind velocity vs. near-relativistic flow). With the predicted contour curves for these wind parameters one can constrain allowed regions for the presence of WAs and UFOs.The model further implies that the UFO's gas pressure is comparable to that of the observed radio jet in 3C111 suggesting that the magnetized disk-wind with density profile of 1/r is a viable agent to help sustain such a self-collimated jet at small radii.

  7. Design, manufacture, and calibration of infrared radiometric blackbody sources

    SciTech Connect

    Byrd, D.A.; Michaud, F.D.; Bender, S.C.

    1996-04-01

    A Radiometric Calibration Station (RCS) is being assembled at the Los Alamos National Laboratories (LANL) which will allow for calibration of sensors with detector arrays having spectral capability from about 0.4-15 {mu}m. The configuration of the LANL RCS. Two blackbody sources have been designed to cover the spectral range from about 3-15 {mu}m, operating at temperatures ranging from about 180-350 K within a vacuum environment. The sources are designed to present a uniform spectral radiance over a large area to the sensor unit under test. The thermal uniformity requirement of the blackbody cavities has been one of the key factors of the design, requiring less than 50 mK variation over the entire blackbody surface to attain effective emissivity values of about 0.999. Once the two units are built and verified to the level of about 100 mK at LANL, they will be sent to the National Institute of Standards and Technology (NIST), where at least a factor of two improvement will be calibrated into the blackbody control system. The physical size of these assemblies will require modifications of the existing NIST Low Background Infrared (LBIR) Facility. LANL has constructed a bolt-on addition to the LBIR facility that will allow calibration of our large aperture sources. Methodology for attaining the two blackbody sources at calibrated levels of performance equivalent to present state of the art will be explained in the following.

  8. Liposomogenic UV Absorbers are Water-Resistant on Pig Skin-A Model Study With Relevance for Sunscreens.

    PubMed

    Herzog, Bernd; Hüglin, Dietmar; Luther, Helmut

    2017-02-01

    An important property of sunscreens is their water resistance after the application on human skin. In this work, the hypothesis that UV absorber molecules which are able to form liposomes, so-called liposomogenic UV absorbers, show better water resistance on a pig skin model than UV-absorbing molecules lacking this ability was tested. The assumption behind is that molecules which can form liposomes are able to integrate into the stratum corneum lipids of the skin. Three different liposomogenic UV absorbers were synthesized and their behavior investigated, leading to the confirmation of the hypothesis. With one of the liposomogenic UV absorbers, it was possible to show the integration of the UV absorber molecules into the bilayers of another liposome consisting of phosphatidylcholine, supporting the assumption that liposomogenic UV absorbers exhibit improved water resistance because they integrate into the skin lipids.

  9. CMB all-scale blackbody distortions induced by linearizing temperature

    NASA Astrophysics Data System (ADS)

    Notari, Alessio; Quartin, Miguel

    2016-08-01

    Cosmic microwave background (CMB) experiments, such as WMAP and Planck, measure intensity anisotropies and build maps using a linearized formula for relating them to the temperature blackbody fluctuations. However, this procedure also generates a signal in the maps in the form of y -type distortions which is degenerate with the thermal Sunyaev Zel'dovich (tSZ) effect. These are small effects that arise at second order in the temperature fluctuations not from primordial physics but from such a limitation of the map-making procedure. They constitute a contaminant for measurements of our peculiar velocity, the tSZ and primordial y -distortions. They can nevertheless be well modeled and accounted for. We show that the distortions arise from a leakage of the CMB dipole into the y -channel which couples to all multipoles, mostly affecting the range ℓ≲400 . This should be visible in Planck's y -maps with an estimated signal-to-noise ratio of about 12. We note however that such frequency-dependent terms carry no new information on the nature of the CMB dipole. This implies that the real significance of Planck's Doppler coupling measurements is actually lower than reported by the collaboration. Finally, we quantify the level of contamination in tSZ and primordial y -type distortions and show that it is above the sensitivity of proposed next-generation CMB experiments.

  10. Active-absorbing-state phase transition beyond directed percolation: a class of exactly solvable models.

    PubMed

    Basu, Urna; Mohanty, P K

    2009-04-01

    We introduce and solve a model of hardcore particles on a one-dimensional periodic lattice which undergoes an active-absorbing-state phase transition at finite density. In this model, an occupied site is defined to be active if its left neighbor is occupied and the right neighbor is vacant. Particles from such active sites hop stochastically to their right. We show that both the density of active sites and the survival probability vanish as the particle density is decreased below half. The critical exponents and spatial correlations of the model are calculated exactly using the matrix product ansatz. Exact analytical study of several variations of the model reveals that these nonequilibrium phase transitions belong to a new universality class different from the generic active-absorbing-state phase transition, namely, directed percolation.

  11. Thermodynamic properties of the blackbody radiation: A Kaniadakis approach

    NASA Astrophysics Data System (ADS)

    Lourek, Imene; Tribeche, Mouloud

    2017-02-01

    The thermodynamic properties of the blackbody radiation are revisited, for the first time, within the theoretical framework of the κ-statistics introduced by Kaniadakis. Using the κ-counterpart of the Bose-Einstein distribution, generalized expressions for the free energy, the entropy, the specific heat, and the pressure are obtained. All quantities are shown to recover their standard expressions in the limit κ → 0. The reexamination of the thermodynamic properties of the blackbody radiation shows that it emits more energy with an increase of the value of | κ | in comparison with the standard Planck radiation law. Moreover, the effects of the deformed Kaniadakis statistics are shown to be more appreciable for high temperatures. Our results could be used as a theoretical support for experimental studies implying blackbody radiation such as the study of microwave background radiation.

  12. Modelling a point absorbing wave energy converter by the equivalent electric circuit theory: A feasibility study

    NASA Astrophysics Data System (ADS)

    Hai, Ling; Svensson, Olle; Isberg, Jan; Leijon, Mats

    2015-04-01

    There is a need to have a reliable tool to quickly assess wave energy converters (WECs). This paper explores whether it is possible to apply the equivalent electric circuit theory as an evaluation tool for point absorbing WEC system modelling. The circuits were developed starting from the force analysis, in which the hydrodynamic, mechanical, and electrical parameters were expressed by electrical components. A methodology on how to determine the parameters for electrical components has been explained. It is found that by using a multimeter, forces in the connection line and the absorbed electric power can be simulated and read directly from the electric circuit model. Finally, the circuit model has been validated against the full scale offshore experiment. The results indicated that the captured power could be predicted rather accurately and the line force could be estimated accurately near the designed working condition of the WEC.

  13. Validation of a Blackbody Comparator-Based System for Thermocouple Calibration

    NASA Astrophysics Data System (ADS)

    Ojanen, M.; Hahtela, O.; Heinonen, M.

    2014-04-01

    A blackbody comparator for thermocouple calibration in the temperature range from to has previously been developed at the Centre for Metrology and Accreditation (MIKES). The calibration system is based on direct comparison of thermocouples and a radiation thermometer. In this article, the blackbody comparator is exploited by comparing an absolute calibrated irradiance mode filter radiometer and a linear pyrometer calibrated according to the International Temperature Scale of 1990 (ITS-90) to each other in the temperature range from to . The results of the comparison are in agreement within uncertainties (). Furthermore, thermal gradients in the blackbody comparator are studied by means of numerical simulation, as the gradients were found to be the major source of uncertainty in previous work. A thermal model was constructed with COMSOL software, and the radial and longitudinal gradients were studied in the comparator. The results of the modeling are in agreement with the uncertainty determination carried out in previous work, but the gradients still remain a significant uncertainty contribution. The validation of the calibration system was completed by comparing calibration results obtained with the system for a Pt/Pd thermocouple to calibration results reported by the National Physical Laboratory (NPL), UK. The results of the comparison agree within the expanded uncertainty () of the comparison.

  14. Noise-induced absorbing phase transition in a model of opinion formation

    NASA Astrophysics Data System (ADS)

    Vieira, Allan R.; Crokidakis, Nuno

    2016-08-01

    In this work we study a 3-state (+1, -1, 0) opinion model in the presence of noise and disorder. We consider pairwise competitive interactions, with a fraction p of those interactions being negative (disorder). Moreover, there is a noise q that represents the probability of an individual spontaneously change his opinion to the neutral state. Our aim is to study how the increase/decrease of the fraction of neutral agents affects the critical behavior of the system and the evolution of opinions. We derive analytical expressions for the order parameter of the model, as well as for the stationary fraction of each opinion, and we show that there are distinct phase transitions. One is the usual ferro-paramagnetic transition, that is in the Ising universality class. In addition, there are para-absorbing and ferro-absorbing transitions, presenting the directed percolation universality class. Our results are complemented by numerical simulations.

  15. Measurement of high-temperature spectral emissivity using integral blackbody approach

    NASA Astrophysics Data System (ADS)

    Pan, Yijie; Dong, Wei; Lin, Hong; Yuan, Zundong; Bloembergen, Pieter

    2016-11-01

    Spectral emissivity is one of the most critical thermophysical properties of a material for heat design and analysis. Especially in the traditional radiation thermometry, normal spectral emissivity is very important. We developed a prototype instrument based upon an integral blackbody method to measure material's spectral emissivity at elevated temperatures. An optimized commercial variable-high-temperature blackbody, a high speed linear actuator, a linear pyrometer, and an in-house designed synchronization circuit was used to implemented the system. A sample was placed in a crucible at the bottom of the blackbody furnace, by which the sample and the tube formed a simulated reference blackbody which had an effective total emissivity greater than 0.985. During the measurement, a pneumatic cylinder pushed a graphite rode and then the sample crucible to the cold opening within hundreds of microseconds. The linear pyrometer was used to monitor the brightness temperature of the sample surface, and the corresponding opto-converted voltage was fed and recorded by a digital multimeter. To evaluate the temperature drop of the sample along the pushing process, a physical model was proposed. The tube was discretized into several isothermal cylindrical rings, and the temperature of each ring was measurement. View factors between sample and rings were utilized. Then, the actual surface temperature of the sample at the end opening was obtained. Taking advantages of the above measured voltage signal and the calculated actual temperature, normal spectral emissivity under the that temperature point was obtained. Graphite sample at 1300°C was measured to prove the validity of the method.

  16. Effect of Insertion of a Heat Flux Gage into a High Temperature Cylindrical Blackbody Cavity on the Gage

    NASA Technical Reports Server (NTRS)

    Abdelmessih, Amanie N.; Horn, Thomas J.

    2007-01-01

    Detailed transient thermal models have been developed to simulate a heat flux gage calibration process capable of generating high heat flux levels. These heat flux levels are of interest to the reciprocating and gas turbine engine industries as well as the aerospace industry. The transient models are based on existing, experimentally validated steady state models of a cylindrical blackbody calibration system. The steady state models were modified to include insertion of a heat flux gage into the hot zone of the calibration system, time-varying electrical current that passes through the resistance heated blackbody, and the resulting heating of the heat flux gage. Heat fluxes computed using detailed transient models were compared to experimental measurements. The calculated and measured transient heat fluxes agreed to within 2 percent, indicating that the models had captured the physical phenomena in the transient calibration. The predicted and measured transient heat fluxes were also compared for two different blackbody configurations. The effect of convection on the blackbody extension was evaluated and found to be a minor factor.

  17. High temperature blackbody BB2000/40 for calibration of radiation thermometers and thermocouple

    SciTech Connect

    Ogarev, S. A.; Khlevnoy, B. B.; Samoylov, M. L.; Puzanov, A. V.

    2013-09-11

    The cavity-type high temperature blackbody (HTBB) models of BB3200/3500 series are the most spread among metrological institutes worldwide as sources for radiometry and radiation thermometry, due to their ultra high working temperatures, high emissivity and stability. The materials of radiating cavities are graphite, pyrolytic graphite (PG) and their combination. The paper describes BB2000/40 blackbody with graphite-tube cavity that was developed for calibration of radiation thermometers at SCEI (Singapore). The peculiarity of BB2000/40 is a possibility to use it, besides calibration of pyrometers, as an instrument for thermocouples calibration. Operating within the temperature range from 900 °C to 2000 °C, the blackbody has a wide cavity opening of 40 mm. Emissivity of the cavity, with PG heater rings replaced partly by graphite elements, was estimated as 0.998 ± 0.0015 in the spectral range from 350 nm to 2000 nm. The uniformity along the cavity axis, accounting for 10 °C, was measured using a B-type thermocouple at 1500 °C. The BB2000/40, if necessary, can be easily modified, by replacing the graphite radiator with a set of PG rings, to be able to reach temperatures as high as 3200 °C. The HTBB utilizes an optical feedback system which allows temperature stabilization within 0.1 °C. This rear-view feedback allows the whole HTBB aperture to be used for measurements.

  18. Absorbing-sphere model for calculating ion-ion recombination total cross sections.

    NASA Technical Reports Server (NTRS)

    Olson, R. E.

    1972-01-01

    An 'absorbing-sphere' model based on the Landau-Zener method is set up for calculating the upper limit thermal energy (300 K) reaction rate and the energy dependence of the total cross sections. The crucial parameter needed for the calculation is the electron detachment energy for the outer electron on the anion. It is found that the cross sections increase with decreasing electron detachment energy.

  19. Transient vibration analytical modeling and suppressing for vibration absorber system under impulse excitation

    NASA Astrophysics Data System (ADS)

    Wang, Xi; Yang, Bintang; Yu, Hu; Gao, Yulong

    2017-04-01

    The impulse excitation of mechanism causes transient vibration. In order to achieve adaptive transient vibration control, a method which can exactly model the response need to be proposed. This paper presents an analytical model to obtain the response of the primary system attached with dynamic vibration absorber (DVA) under impulse excitation. The impulse excitation which can be divided into single-impulse excitation and multi-impulse excitation is simplified as sinusoidal wave to establish the analytical model. To decouple the differential governing equations, a transform matrix is applied to convert the response from the physical coordinate to model coordinate. Therefore, the analytical response in the physical coordinate can be obtained by inverse transformation. The numerical Runge-Kutta method and experimental tests have demonstrated the effectiveness of the analytical model proposed. The wavelet of the response indicates that the transient vibration consists of components with multiple frequencies, and it shows that the modeling results coincide with the experiments. The optimizing simulations based on genetic algorithm and experimental tests demonstrate that the transient vibration of the primary system can be decreased by changing the stiffness of the DVA. The results presented in this paper are the foundations for us to develop the adaptive transient vibration absorber in the future.

  20. Reactive decontamination of absorbing thin film polymer coatings: model development and parameter determination

    NASA Astrophysics Data System (ADS)

    Varady, Mark; Mantooth, Brent; Pearl, Thomas; Willis, Matthew

    2014-03-01

    A continuum model of reactive decontamination in absorbing polymeric thin film substrates exposed to the chemical warfare agent O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothioate (known as VX) was developed to assess the performance of various decontaminants. Experiments were performed in conjunction with an inverse analysis method to obtain the necessary model parameters. The experiments involved contaminating a substrate with a fixed VX exposure, applying a decontaminant, followed by a time-resolved, liquid phase extraction of the absorbing substrate to measure the residual contaminant by chromatography. Decontamination model parameters were uniquely determined using the Levenberg-Marquardt nonlinear least squares fitting technique to best fit the experimental time evolution of extracted mass. The model was implemented numerically in both a 2D axisymmetric finite element program and a 1D finite difference code, and it was found that the more computationally efficient 1D implementation was sufficiently accurate. The resulting decontamination model provides an accurate quantification of contaminant concentration profile in the material, which is necessary to assess exposure hazards.

  1. Effects of scattering and absorbing medium in the fluorescence conversion efficiency of physical tissue models

    NASA Astrophysics Data System (ADS)

    Anand, Suresh; Sujatha, N.

    2015-03-01

    Auto-fluorescence spectroscopy based on spectral line shape and intensity has been in use as a promising technique for detecting varying degrees of tissue malignancy. Tissue is a turbid medium with multi-layered structure constituting of different fluorophores, absorbers and scattering molecules. Tumor progression in tissues is ac- companied by varying degrees of biochemical and morphological changes. These include changes in nuclear size and density, epithelial thickness and increase in the hemoglobin (Hb) concentration associated with changes in metabolic activity. These variations in overall tissue scattering and absorption properties in turn modulate the fluorescence spectrum emitted and derived from tissues. Estimation of fluorescence conversion efficiency in the turbid tissue needs to take into account these effects of absorption and scattering in order to be evolved as a parameter for tissue discrimination. In this study, we set to investigate the factors affecting tissue fluorescence conversion efficiency by making use of physical models of the tissue. Liquid tissue models were prepared with different concentrations of absorbing and scattering media to simulate biological tissues of various degrees of malignancy. The results indicate that emitted fluorescence from the tissue model is subjected to variations by multiple scattering events and absorption. The fluorescence conversion efficiency of the models were derived and correlated to the experimental results with possible diagnostic significance.

  2. Modeling and characterization of extremely thin absorber (eta) solar cells based on ZnO nanowires.

    PubMed

    Mora-Seró, Iván; Giménez, Sixto; Fabregat-Santiago, Francisco; Azaceta, Eneko; Tena-Zaera, Ramón; Bisquert, Juan

    2011-04-21

    Extremely thin absorber (eta)-solar cells based on ZnO nanowires sensitized with a thin layer of CdSe have been prepared, using CuSCN as hole transporting material. Samples with significantly different photovoltaic performance have been analyzed and a general model of their behavior was obtained. We have used impedance spectroscopy to model the device discriminating the series resistance, the role of the hole conducting material CuSCN, and the interface process. Correlating the impedance analysis with the microstructural properties of the solar cell interfaces, a good description of the solar cell performance is obtained. The use of thick CdSe layers leads to high recombination resistances, increasing the open circuit voltage of the devices. However, there is an increase of the internal recombination in thick light absorbing layers that also inhibit a good penetration of CuSCN, reducing the photocurrent. The model will play an important role on the optimization of these devices. This analysis could have important implications for the modeling and optimization of all-solid devices using a sensitizing configuration.

  3. A Comparison of Model Calculation and Measurement of Absorbed Dose for Proton Irradiation. Chapter 5

    NASA Technical Reports Server (NTRS)

    Zapp, N.; Semones, E.; Saganti, P.; Cucinotta, F.

    2003-01-01

    With the increase in the amount of time spent EVA that is necessary to complete the construction and subsequent maintenance of ISS, it will become increasingly important for ground support personnel to accurately characterize the radiation exposures incurred by EVA crewmembers. Since exposure measurements cannot be taken within the organs of interest, it is necessary to estimate these exposures by calculation. To validate the methods and tools used to develop these estimates, it is necessary to model experiments performed in a controlled environment. This work is such an effort. A human phantom was outfitted with detector equipment and then placed in American EMU and Orlan-M EVA space suits. The suited phantom was irradiated at the LLUPTF with proton beams of known energies. Absorbed dose measurements were made by the spaceflight operational dosimetrist from JSC at multiple sites in the skin, eye, brain, stomach, and small intestine locations in the phantom. These exposures are then modeled using the BRYNTRN radiation transport code developed at the NASA Langley Research Center, and the CAM (computerized anatomical male) human geometry model of Billings and Yucker. Comparisons of absorbed dose calculations with measurements show excellent agreement. This suggests that there is reason to be confident in the ability of both the transport code and the human body model to estimate proton exposure in ground-based laboratory experiments.

  4. Modeling of light absorbing particles in atmosphere, snow and ice in the Arctic

    NASA Astrophysics Data System (ADS)

    Sobhani, N.; Kulkarni, S.; Carmichael, G. R.

    2015-12-01

    Long-range transport of atmospheric particles from mid-latitude sources to the Arctic is the main contributor to the Arctic aerosol loadings and deposition. Black Carbon (BC), Brown Carbon (BrC) and dust are considered of great climatic importance and are the main absorbers of sunlight in the atmosphere. Furthermore, wet and dry deposition of light absorbing particles (LAPs) on snow and ice cause reduction of snow and ice albedo. LAPs have significant radiative forcing and effect on snow albedo. There are high uncertainties in estimating radiative forcing of LAPs. We studied the potential effect of LAPs from different emission source regions and sectors on snow albedo in the Arctic. The transport pathway of LAPs to the Arctic is studies for different high pollution episodes. In this study a modeling framework including Weather Research and Forecasting Model (WRF) and the University of Iowa's Sulfur Transport and dEpostion model(STEM) is used to predict the transport of LAPs from different geographical sources and sectors (i.e. transportation, residential, industry, biomass burning and power) to the Arctic. For assessing the effect of LAP deposition on snow single-layer simulator of the SNow, Ice, and Aerosol Radiation (SNICAR-Online) model was used to derive snow albedo values for snow albedo reduction causes by BC deposition. To evaluate the simulated values we compared the BC concentration in snow with observed values from previous studies including Doherty et al. 2010.

  5. Blackbody radiation shift in ^87Rb frequency standard

    NASA Astrophysics Data System (ADS)

    Safronova, Marianna; Safronova, U. I.

    2010-03-01

    The operation of atomic clocks is generally carried out at room temperature, whereas the definition of the second refers to the clock transition in an atom at absolute zero. This implies that the clock transition frequency should be corrected in practice for the effect of finite temperature of which the leading contributor is the blackbody radiation (BBR) shift. Experimental measurements of the BBR shifts are difficult. In this work, we have calculated the blackbody radiation shift of the ground-state hyperfine microwave transition in ^87Rb using the relativistic all-order method and evaluated the accuracy of our final value. Particular care is taken to accurately account for the contributions from highly-excited states. Various Rb atomic properties, including E1, E2, and E3 ground state polarizabilities, np and nd E1 polarizabilities, and hyperfine constants are also calculated. The results are compared with experiment and other theory where available.

  6. Rydberg atom spectroscopy enabled by blackbody radiation ionization

    SciTech Connect

    Lu Xiaoxu; Sun Yuan; Metcalf, Harold

    2011-09-15

    We have excited helium atoms from their metastable 2 {sup 3} S state to Rydberg states in the range 13blackbody radiation. Multiple tests confirm this attribution as the cause of ionization. For example, by heating the plates we observe the expected signal increases. Our experiments reinforce previous work where the interaction between Rydberg atoms and room temperature blackbody radiation is important for experiments.

  7. Active vibration absorber for the CSI evolutionary model - Design and experimental results. [Controls Structures Interaction

    NASA Technical Reports Server (NTRS)

    Bruner, Anne M.; Belvin, W. Keith; Horta, Lucas G.; Juang, Jer-Nan

    1991-01-01

    The development of control of large flexible structures technology must include practical demonstrations to aid in the understanding and characterization of controlled structures in space. To support this effort, a testbed facility has been developed to study practical implementation of new control technologies under realistic conditions. The paper discusses the design of a second order, acceleration feedback controller which acts as an active vibration absorber. This controller provides guaranteed stability margins for collocated sensor/actuator pairs in the absence of sensor/actuator dynamics and computational time delay. Experimental results in the presence of these factors are presented and discussed. The robustness of this design under model uncertainty is demonstrated.

  8. Blackbody absorption efficiencies for six lamp pumped Nd laser materials

    NASA Technical Reports Server (NTRS)

    Cross, Patricia L.; Barnes, Norman P.; Skolaut, Milton W., Jr.; Storm, Mark E.

    1990-01-01

    Utilizing high resolution spectra, the absorption efficiencies for six Nd laser materials were calculated as functions of the effective blackbody temperature of the lamp and laser crystal size. The six materials were Nd:YAG, Nd:YLF, Nd:Q-98 Glass, Nd:YVO4, Nd:BEL, and Nd:Cr:GSGG. Under the guidelines of this study, Nd:Cr:GSGG's absorption efficiency is twice the absorption efficiency of any of the other laser materials.

  9. ELECTRON ABSORBED FRACTIONS IN AN IMAGE-BASED MICROSCOPIC SKELETAL DOSIMETRY MODEL OF CHINESE ADULT MALE.

    PubMed

    Gao, Shenshen; Ren, Li; Qiu, Rui; Wu, Zhen; Li, Chunyan; Li, Junli

    2017-01-10

    Based on the Chinese reference adult male voxel model, a set of microscopic skeletal models of Chinese adult male is constructed through the processes of computed tomography (CT) imaging, bone coring, micro-CT imaging, image segmentation, merging into macroscopic bone model and implementation in Geant4. At the step of image segmentation, a new bone endosteum (BE) segmentation method is realized by sampling. The set of model contains 32 spongiosa samples with voxel size of 19 μm cubes. The microscopic spongiosa bone data for Chinese adult male are provided. Electron absorbed fractions in red bone marrow (RBM) and BE are calculated. Source tissues include the bone marrow (red and yellow), trabecular bone (surfaces and volumes) and cortical bone (surfaces and volumes). Target tissues include RBM and BE. Electron energies range from 10 keV to 10 MeV. Additionally, comparison of the result with other investigations is provided.

  10. A new compact fixed-point blackbody furnace

    SciTech Connect

    Hiraka, K.; Oikawa, H.; Shimizu, T.; Kadoya, S.; Kobayashi, T.; Yamada, Y.; Ishii, J.

    2013-09-11

    More and more NMIs are realizing their primary scale themselves with fixed-point blackbodies as their reference standard. However, commercially available fixed-point blackbody furnaces of sufficient quality are not always easy to obtain. CHINO Corp. and NMIJ, AIST jointly developed a new compact fixed-point blackbody furnace. The new furnace has such features as 1) improved temperature uniformity when compared to previous products, enabling better plateau quality, 2) adoption of the hybrid fixed-point cell structure with internal insulation to improve robustness and thereby to extend lifetime, 3) easily ejectable and replaceable heater unit and fixed-point cell design, leading to reduced maintenance cost, 4) interchangeability among multiple fixed points from In to Cu points. The replaceable cell feature facilitates long term maintenance of the scale through management of a group of fixed-point cells of the same type. The compact furnace is easily transportable and therefore can also function as a traveling standard for disseminating the radiation temperature scale, and for maintaining the scale at the secondary level and industrial calibration laboratories. It is expected that the furnace will play a key role of the traveling standard in the anticipated APMP supplementary comparison of the radiation thermometry scale.

  11. Quantum driven dissipative parametric oscillator in a blackbody radiation field

    SciTech Connect

    Pachón, Leonardo A.; Brumer, Paul

    2014-01-15

    We consider the general open system problem of a charged quantum oscillator confined in a harmonic trap, whose frequency can be arbitrarily modulated in time, that interacts with both an incoherent quantized (blackbody) radiation field and with an arbitrary coherent laser field. We assume that the oscillator is initially in thermodynamic equilibrium with its environment, a non-factorized initial density matrix of the system and the environment, and that at t = 0 the modulation of the frequency, the coupling to the incoherent and the coherent radiation are switched on. The subsequent dynamics, induced by the presence of the blackbody radiation, the laser field, and the frequency modulation, is studied in the framework of the influence functional approach. This approach allows incorporating, in analytic closed formulae, the non-Markovian character of the oscillator-environment interaction at any temperature as well the non-Markovian character of the blackbody radiation and its zero-point fluctuations. Expressions for the time evolution of the covariance matrix elements of the quantum fluctuations and the reduced density-operator are obtained.

  12. Solid state saturable absorbers for Q-switching at 1 and 1.3μm: investigation and modeling

    NASA Astrophysics Data System (ADS)

    Šulc, Jan; Arátor, Pavel; Jelínková, Helena; Nejezchleb, Karel; Škoda, Václav; Kokta, Milan R.

    2008-02-01

    Yttrium and Lutecium garnets (YAG and LuAG) doped by Chromium or Vanadium ions (Cr 4+ or V 3+) were investigated as saturable absorbers potentially useful for passive Q-switching at wavelengths 1 μm and/or 1.3 μm. For comparison also color center saturable absorber LiF:F - II and Cobalt doped spinel (Co:MALO) were studied. Firstly, low power absorption spectra were recorded for all samples. Next, absorbers transmission in dependence on incident energy/power density was measured using the z-scan method. Crystals Cr:YAG, Cr:LuAG, V:YAG, and LiF:F - II were tested at wavelength 1064 nm. Therefore Alexandrite laser pumped Q-switched Nd:YAG laser was used as a radiation source (pulse length 6.9 ns, energy up to 1.5 mJ). Crystals V:YAG, V:LuAG, and Co:MALO were tested at wavelength 1338 nm. So diode pumped Nd:YAG/V:YAG microchip laser was used as a radiation source (pulse length 6.2 ns, energy up to 0.1 mJ). Using measured data fitting, and by their comparison with numerical model of a "thick" saturable absorber transmission for Q-switched Gaussian laser beam, following parameters were estimated: saturable absorber initial transmission T 0, saturation energy density w s, ground state absorption cross-section σ GSA, saturated absorber transmission T s, excited state absorption cross-section σ ESA, ratio γ = σ GSA/σ ESA, and absorbing ions density. For V:YAG crystal, a polarization dependence of T s was also investigated. With the help of rate equation numerical solution, an impact of saturable absorber parameters on generated Q-switched pulse properties was studied in plane wave approximation. Selected saturable absorbers were also investigated as a Q-switch and results were compared with the model.

  13. Mechanical device for determining the stiffness and the viscous friction coefficient of shock absorber elements modelled by bond graph

    NASA Astrophysics Data System (ADS)

    Ibănescu, R.; Ibănescu, M.

    2016-11-01

    The present paper presents a mechanical device for the assessment of the fundamental parameters of a shock absorber: the spring stiffness and the viscous friction coefficient, without disassembling the absorber. The device produces an oscillatory motion of the shock absorber and can measure its amplitude and angular velocities. The dynamic model of the system, consisting of the mechanical device and the shock absorber, is performed by using the bond- graph method. Based on this model, the motion equations are obtained, which by integration lead to the motion law. The two previously mentioned parameters are determined by using this law and the measured values of two amplitudes and of their corresponding angular velocities. They result as solutions of a system of two non-linear algebraic equations.

  14. Active vibration absorber for CSI evolutionary model: Design and experimental results

    NASA Technical Reports Server (NTRS)

    Bruner, Anne M.; Belvin, W. Keith; Horta, Lucas G.; Juang, Jer-Nan

    1991-01-01

    The development of control of large flexible structures technology must include practical demonstration to aid in the understanding and characterization of controlled structures in space. To support this effort, a testbed facility was developed to study practical implementation of new control technologies under realistic conditions. The design is discussed of a second order, acceleration feedback controller which acts as an active vibration absorber. This controller provides guaranteed stability margins for collocated sensor/actuator pairs in the absence of sensor/actuator dynamics and computational time delay. The primary performance objective considered is damping augmentation of the first nine structural modes. Comparison of experimental and predicted closed loop damping is presented, including test and simulation time histories for open and closed loop cases. Although the simulation and test results are not in full agreement, robustness of this design under model uncertainty is demonstrated. The basic advantage of this second order controller design is that the stability of the controller is model independent.

  15. Comparison of Primary Models to Predict Microbial Growth by the Plate Count and Absorbance Methods.

    PubMed

    Pla, María-Leonor; Oltra, Sandra; Esteban, María-Dolores; Andreu, Santiago; Palop, Alfredo

    2015-01-01

    The selection of a primary model to describe microbial growth in predictive food microbiology often appears to be subjective. The objective of this research was to check the performance of different mathematical models in predicting growth parameters, both by absorbance and plate count methods. For this purpose, growth curves of three different microorganisms (Bacillus cereus, Listeria monocytogenes, and Escherichia coli) grown under the same conditions, but with different initial concentrations each, were analysed. When measuring the microbial growth of each microorganism by optical density, almost all models provided quite high goodness of fit (r(2) > 0.93) for all growth curves. The growth rate remained approximately constant for all growth curves of each microorganism, when considering one growth model, but differences were found among models. Three-phase linear model provided the lowest variation for growth rate values for all three microorganisms. Baranyi model gave a variation marginally higher, despite a much better overall fitting. When measuring the microbial growth by plate count, similar results were obtained. These results provide insight into predictive microbiology and will help food microbiologists and researchers to choose the proper primary growth predictive model.

  16. Comparison of Primary Models to Predict Microbial Growth by the Plate Count and Absorbance Methods

    PubMed Central

    Pla, María-Leonor; Oltra, Sandra; Esteban, María-Dolores; Andreu, Santiago; Palop, Alfredo

    2015-01-01

    The selection of a primary model to describe microbial growth in predictive food microbiology often appears to be subjective. The objective of this research was to check the performance of different mathematical models in predicting growth parameters, both by absorbance and plate count methods. For this purpose, growth curves of three different microorganisms (Bacillus cereus, Listeria monocytogenes, and Escherichia coli) grown under the same conditions, but with different initial concentrations each, were analysed. When measuring the microbial growth of each microorganism by optical density, almost all models provided quite high goodness of fit (r2 > 0.93) for all growth curves. The growth rate remained approximately constant for all growth curves of each microorganism, when considering one growth model, but differences were found among models. Three-phase linear model provided the lowest variation for growth rate values for all three microorganisms. Baranyi model gave a variation marginally higher, despite a much better overall fitting. When measuring the microbial growth by plate count, similar results were obtained. These results provide insight into predictive microbiology and will help food microbiologists and researchers to choose the proper primary growth predictive model. PMID:26539483

  17. Modeling electron dynamics coupled to continuum states in finite volumes with absorbing boundaries

    NASA Astrophysics Data System (ADS)

    De Giovannini, Umberto; Larsen, Ask Hjorth; Rubio, Angel

    2015-03-01

    Absorbing boundaries are frequently employed in real-time propagation of the Schrödinger equation to remove spurious reflections and efficiently emulate outgoing boundary conditions. These conditions are a fundamental ingredient for the calculation of observables involving infinitely extended continuum states in finite volumes. In the literature, several boundary absorbers have been proposed. They mostly fall into three main families: mask function absorbers, complex absorbing potentials, and exterior complex-scaled potentials. To date none of the proposed absorbers is perfect, and all present a certain degree of reflections. Characterization of such reflections is thus a critical task with strong implications for time-dependent simulations of atoms and molecules. We introduce a method to evaluate the reflection properties of a given absorber and present a comparison of selected samples for each family of absorbers. Further, we discuss the connections between members of each family and show how the same reflection curves can be obtained with very different absorption schemes.

  18. Modeling the distribution of Mg II absorbers around galaxies using background galaxies and quasars

    SciTech Connect

    Bordoloi, R.; Lilly, S. J.; Kacprzak, G. G.; Churchill, C. W.

    2014-04-01

    We present joint constraints on the distribution of Mg II absorption around high redshift galaxies obtained by combining two orthogonal probes, the integrated Mg II absorption seen in stacked background galaxy spectra and the distribution of parent galaxies of individual strong Mg II systems as seen in the spectra of background quasars. We present a suite of models that can be used to predict, for different two- and three-dimensional distributions, how the projected Mg II absorption will depend on a galaxy's apparent inclination, the impact parameter b and the azimuthal angle between the projected vector to the line of sight and the projected minor axis. In general, we find that variations in the absorption strength with azimuthal angles provide much stronger constraints on the intrinsic geometry of the Mg II absorption than the dependence on the inclination of the galaxies. In addition to the clear azimuthal dependence in the integrated Mg II absorption that we reported earlier in Bordoloi et al., we show that strong equivalent width Mg II absorbers (W{sub r} (2796) ≥ 0.3 Å) are also asymmetrically distributed in azimuth around their host galaxies: 72% of the absorbers in Kacprzak et al., and 100% of the close-in absorbers within 35 kpc of the center of their host galaxies, are located within 50° of the host galaxy's projected semi minor axis. It is shown that either composite models consisting of a simple bipolar component plus a spherical or disk component, or a single highly softened bipolar distribution, can well represent the azimuthal dependencies observed in both the stacked spectrum and quasar absorption-line data sets within 40 kpc. Simultaneously fitting both data sets, we find that in the composite model the bipolar cone has an opening angle of ∼100° (i.e., confined to within 50° of the disk axis) and contains about two-thirds of the total Mg II absorption in the system. The single softened cone model has an exponential fall off with azimuthal

  19. Size-dependent fluorescence of bioaerosols: Mathematical model using fluorescing and absorbing molecules in bacteria

    NASA Astrophysics Data System (ADS)

    Hill, Steven C.; Williamson, Chatt C.; Doughty, David C.; Pan, Yong-Le; Santarpia, Joshua L.; Hill, Hanna H.

    2015-05-01

    This paper uses a mathematical model of fluorescent biological particles composed of bacteria and/or proteins (mostly as in Hill et al., 2013 [23]) to investigate the size-dependence of the total fluorescence emitted in all directions. The model applies to particles which have negligible reabsorption of fluorescence within the particle. The specific particles modeled here are composed of ovalbumin and of a generic Bacillus. The particles need not be spherical, and in some cases need not be homogeneous. However, the results calculated in this paper are for spherical homogeneous particles. Light absorbing and fluorescing molecules included in the model are amino acids, nucleic acids, and several coenzymes. Here the excitation wavelength is 266 nm. The emission range, 300 to 370 nm, encompasses the fluorescence of tryptophan. The fluorescence cross section (CF) is calculated and compared with one set of published measured values. We investigate power law (Ady) approximations to CF, where d is diameter, and A and y are parameters adjusted to fit the data, and examine how y varies with d and composition, including the fraction as water. The particle's fluorescence efficiency (QF=CF/geometric-cross-section) can be written for homogeneous particles as QabsRF, where Qabs is the absorption efficiency, and RF, the fraction of the absorbed light emitted as fluorescence, is independent of size and shape. When QF is plotted vs. mid or mi(mr-1)d, where m=mr+imi is the complex refractive index, the plots for different fractions of water in the particle tend to overlap.

  20. Size-dependent fluorescence of bioaerosols: Mathematical model using fluorescing and absorbing molecules in bacteria

    SciTech Connect

    Hill, Steven C.; Williamson, Chatt C.; Doughty, David C.; Pan, Yong-Le; Santarpia, Joshua L.; Hill, Hanna H.

    2015-02-02

    This paper uses a mathematical model of fluorescent biological particles composed of bacteria and/or proteins (mostly as in Hill et al., 2013 [23]) to investigate the size-dependence of the total fluorescence emitted in all directions. The model applies to particles which have negligible reabsorption of fluorescence within the particle. The specific particles modeled here are composed of ovalbumin and of a generic Bacillus. The particles need not be spherical, and in some cases need not be homogeneous. However, the results calculated in this paper are for spherical homogeneous particles. Light absorbing and fluorescing molecules included in the model are amino acids, nucleic acids, and several coenzymes. Here the excitation wavelength is 266 nm. The emission range, 300 to 370 nm, encompasses the fluorescence of tryptophan. The fluorescence cross section (CF) is calculated and compared with one set of published measured values. We investigate power law (Ady) approximations to CF, where d is diameter, and A and y are parameters adjusted to fit the data, and examine how y varies with d and composition, including the fraction as water. The particle's fluorescence efficiency (QF=CF/geometric-cross-section) can be written for homogeneous particles as QabsRF, where Qabs is the absorption efficiency, and RF, the fraction of the absorbed light emitted as fluorescence, is independent of size and shape. When QF is plotted vs. mid or mi(mr-1)d, where m=mr+imi is the complex refractive index, the plots for different fractions of water in the particle tend to overlap.

  1. Size-dependent fluorescence of bioaerosols: Mathematical model using fluorescing and absorbing molecules in bacteria

    DOE PAGES

    Hill, Steven C.; Williamson, Chatt C.; Doughty, David C.; ...

    2015-02-02

    This paper uses a mathematical model of fluorescent biological particles composed of bacteria and/or proteins (mostly as in Hill et al., 2013 [23]) to investigate the size-dependence of the total fluorescence emitted in all directions. The model applies to particles which have negligible reabsorption of fluorescence within the particle. The specific particles modeled here are composed of ovalbumin and of a generic Bacillus. The particles need not be spherical, and in some cases need not be homogeneous. However, the results calculated in this paper are for spherical homogeneous particles. Light absorbing and fluorescing molecules included in the model are aminomore » acids, nucleic acids, and several coenzymes. Here the excitation wavelength is 266 nm. The emission range, 300 to 370 nm, encompasses the fluorescence of tryptophan. The fluorescence cross section (CF) is calculated and compared with one set of published measured values. We investigate power law (Ady) approximations to CF, where d is diameter, and A and y are parameters adjusted to fit the data, and examine how y varies with d and composition, including the fraction as water. The particle's fluorescence efficiency (QF=CF/geometric-cross-section) can be written for homogeneous particles as QabsRF, where Qabs is the absorption efficiency, and RF, the fraction of the absorbed light emitted as fluorescence, is independent of size and shape. When QF is plotted vs. mid or mi(mr-1)d, where m=mr+imi is the complex refractive index, the plots for different fractions of water in the particle tend to overlap.« less

  2. Evaluation of absorbed doses in voxel-based and simplified models for small animals.

    PubMed

    Mohammadi, Akram; Kinase, Sakae; Saito, Kimiaki

    2012-07-01

    Internal dosimetry in non-human biota is desirable from the viewpoint of radiation protection of the environment. The International Commission on Radiological Protection (ICRP) proposed Reference Animals and Plants using simplified models, such as ellipsoids and spheres and calculated absorbed fractions (AFs) for whole bodies. In this study, photon and electron AFs in whole bodies of voxel-based rat and frog models have been calculated and compared with AFs in the reference models. It was found that the voxel-based and the reference frog (or rat) models can be consistent for the whole-body AFs within a discrepancy of 25%, as the source was uniformly distributed in the whole body. The specific absorbed fractions (SAFs) and S values were also evaluated in whole bodies and all organs of the voxel-based frog and rat models as the source was distributed in the whole body or skeleton. The results demonstrated that the whole-body SAFs reflect SAFs of all individual organs as the source was uniformly distributed per mass within the whole body by about 30% uncertainties with exceptions for body contour (up to -40%) for both electrons and photons due to enhanced radiation leakages, and for the skeleton for photons only (up to +185%) due to differences in the mass attenuation coefficients. For nuclides such as (90)Y and (90)Sr, which were concentrated in the skeleton, there were large differences between S values in the whole body and those in individual organs, however the whole-body S values for the reference models with the whole body as the source were remarkably similar to those for the voxel-based models with the skeleton as the source, within about 4 and 0.3%, respectively. It can be stated that whole-body SAFs or S values in simplified models without internal organs are not sufficient for accurate internal dosimetry because they do not reflect SAFs or S values of all individual organs as the source was not distributed uniformly in whole body. Thus, voxel-based models

  3. A history of slide rules for blackbody radiation computations

    NASA Astrophysics Data System (ADS)

    Johnson, R. Barry; Stewart, Sean M.

    2012-10-01

    During the Second World War the importance of utilizing detection devices capable of operating in the infrared portion of the electromagnetic spectrum was firmly established. Up until that time, laboriously constructed tables for blackbody radiation needed to be used in calculations involving the amount of radiation radiated within a given spectral region or for other related radiometric quantities. To rapidly achieve reasonably accurate calculations of such radiometric quantities, a blackbody radiation calculator was devised in slide rule form first in Germany in 1944 and soon after in England and the United States. In the immediate decades after its introduction, the radiation slide rule was widely adopted and recognized as a useful and important tool for engineers and scientists working in the infrared field. It reached its pinnacle in the United States in 1970 in a rule introduced by Electro Optical Industries, Inc. With the onset in the latter half of the 1970s of affordable, hand-held electronic calculators, the impending demise of the radiation slide rule was evident. No longer the calculational device of choice, the radiation slide rule all but disappeared within a few short years. Although today blackbody radiation calculations can be readily accomplished using anything from a programmable pocket calculator upwards, with each device making use of a wide variety of numerical approximations to the integral of Planck's function, radiation slide rules were in the early decades of infrared technology the definitive "workhorse" for those involved in infrared systems design and engineering. This paper presents a historical development of radiation slide rules with many versions being discussed.

  4. Equivalent blackbody temperature of the top of a severe storm

    NASA Technical Reports Server (NTRS)

    Pitts, D. E.; Reeser, W. K.; Mendlowitz, M. A.

    1975-01-01

    An RB-57F high-altitude aircraft equipped with Wilde RC-8 cameras and an infrared spectrometer was used in the investigations. A storm was overflown over Graham, Texas, on April 29, 1970. In the experiment, the average radiometric temperature was determined to be very near the environmental temperature near the cloud tops. However, hot and cold regions in and near the updrafts and downdrafts were found to be significantly out of equilibrium. It is recommended that caution should be exercised in determining cloud top altitude from equivalent blackbody temperature.

  5. Magnetic blackbody shift of hyperfine transitions for atomic clocks

    SciTech Connect

    Berengut, J. C.; Flambaum, V. V.; King-Lacroix, J.

    2009-12-15

    We derive an expression for the magnetic blackbody shift of hyperfine transitions such as the cesium primary reference transition which defines the second. The shift is found to be a complicated function of temperature, and has a T{sup 2} dependence only in the high-temperature limit. We also calculate the shift of ground-state p{sub 1/2} hyperfine transitions which have been proposed as new atomic clock transitions. In this case interaction with the p{sub 3/2} fine-structure multiplet may be the dominant effect.

  6. Interior radiances in optically deep absorbing media. 1: Exact solutions for one-dimensional model

    NASA Technical Reports Server (NTRS)

    Kattawar, G. W.; Plass, G. N.

    1973-01-01

    The exact solutions are obtained for a one dimensional model of a scattering and absorbing medium. The results are given for both the reflected and transmitted radiance for any arbitrary surface albedo as well as for the interior radiance. These same quantities are calculated by the matrix operator method. The relative error of the solutions is obtained by comparison with the exact solutions as well as by an error analysis of the equations. The importance of an accurate starting value for the reflection and transmission operators is shown. A fourth order Runge-Kutta method can be used to solve the differential equations satisfied by these operators in order to obtain such accurate starting values.

  7. Development of statistical seasonal prediction models of Arctic Sea Ice concentration using CERES absorbed solar radiation

    NASA Astrophysics Data System (ADS)

    Kim, Yoojin; Kim, Ha-Rim; Choi, Yong-Sang; Kim, WonMoo; Kim, Hye-Sil

    2016-11-01

    Statistical seasonal prediction models for the Arctic sea ice concentration (SIC) were developed for the late summer (August-October) when the downward trend is dramatic. The absorbed solar radiation (ASR) at the top of the atmosphere in June has a significant seasonal leading role on the SIC. Based on the lagged ASR-SIC relationship, two simple statistical models were established: the Markovian stochastic and the linear regression models. Crossvalidated hindcasts of SIC from 1979 to 2014 by the two models were compared with each other and observation. The hindcasts showed general agreement between the models as they share a common predictor, ASR in June and the observed SIC was well reproduced, especially over the relatively thin-ice regions (of one- or multi-year sea ice). The robust predictability confirms the functional role of ASR in the prediction of SIC. In particular, the SIC prediction in October was quite promising probably due to the pronounced icealbedo feedback. The temporal correlation coefficients between the predicted SIC and the observed SIC were 0.79 and 0.82 by the Markovian and regression models, respectively. Small differences were observed between the two models; the regression model performed slightly better in August and September in terms of temporal correlation coefficients. Meanwhile, the prediction skills of the Markovian model in October were higher in the north of Chukchi, the East Siberian, and the Laptev Seas. A strong non-linear relationship between ASR in June and SIC in October in these areas would have increased the predictability of the Markovian model.

  8. A hybrid transport-diffusion model for radiative transfer in absorbing and scattering media

    NASA Astrophysics Data System (ADS)

    Roger, M.; Caliot, C.; Crouseilles, N.; Coelho, P. J.

    2014-10-01

    A new multi-scale hybrid transport-diffusion model for radiative transfer is proposed in order to improve the efficiency of the calculations close to the diffusive regime, in absorbing and strongly scattering media. In this model, the radiative intensity is decomposed into a macroscopic component calculated by the diffusion equation, and a mesoscopic component. The transport equation for the mesoscopic component allows to correct the estimation of the diffusion equation, and then to obtain the solution of the linear radiative transfer equation. In this work, results are presented for stationary and transient radiative transfer cases, in examples which concern solar concentrated and optical tomography applications. The Monte Carlo and the discrete-ordinate methods are used to solve the mesoscopic equation. It is shown that the multi-scale model allows to improve the efficiency of the calculations when the medium is close to the diffusive regime. The proposed model is a good alternative for radiative transfer at the intermediate regime where the macroscopic diffusion equation is not accurate enough and the radiative transfer equation requires too much computational effort.

  9. A study of fraction of absorbed photosynthetically active radiation characteristics based on SAIL model simulation

    NASA Astrophysics Data System (ADS)

    Li, Li; Du, Yongming; Tang, Yong; Liu, Qinhuo

    2012-10-01

    The photosynthetically Active Radiation reached to plant canopy could be divided into two parts that are direct radiation and diffuse radiation. The paths into the vegetation canopy are different of these two kinds of radiation. It makes Fraction of Absorbed Photosynthetically Active Radiation (FPAR) different. So this difference between direct FPAR and diffuse FPAR must be determined to decide whether it should be considered into the FPAR inversion model. In this study, the SAIL model was modified which could output direct FPAR and diffuse FPAR. Then with the change of input parameters such as solar zenith angle, visiblity and LAI, the direct FPAR and diffuse FPAR would be change. When the visibility is set as 5km, 15km and 30km, the contribution of scattering of FPAR on the total FPAR is 52.6%, 29.3% and 21.7%. The error between whole FPAR and direct FPAR is reduced with the increasing of visibility and increased with the reducing of LAI. The maximum relative error is 13.2%. From the simulation analyses, we could see that direct and diffuse FPAR are different with the changes of environment variables. So when modeling of FPAR, the diffuse part cannot be ignored. Direct FPAR and diffuse FPAR must be modeled respectively. This separation will help improve the accuracy of FPAR inversion.

  10. Blackbody radiation shift in the {sup 87}Rb frequency standard

    SciTech Connect

    Safronova, M. S.; Jiang Dansha; Safronova, U. I.

    2010-08-15

    The operation of atomic clocks is generally carried out at room temperature, whereas the definition of the second refers to the clock transition in an atom at absolute zero. This implies that the clock transition frequency should be corrected in practice for the effect of finite temperature, of which the leading contributor is the blackbody radiation (BBR) shift. Experimental measurements of the BBR shifts are difficult. In this work, we have calculated the blackbody radiation shift of the ground-state hyperfine microwave transition in {sup 87}Rb using the relativistic all-order method and carried out a detailed evaluation of the accuracy of our final value. Particular care is taken to accurately account for the contributions from highly excited states. Our predicted value for the Stark coefficient, k{sub S}=-1.240(4)x10{sup -10} Hz/(V/m){sup 2}, is three times more accurate than the previous calculation [E. J. Angstman, V. A. Dzuba, and V. V. Flambaum, Phys. Rev. A 74, 023405 (2006)].

  11. Measurements of Martin-Puplett Interferometer Limitations using Blackbody Source

    SciTech Connect

    Evtushenko, Pavel E.; Klopf, John M.

    2013-06-01

    Frequency domain measurements with Martin-Puplett interferometer is one of a few techniques capable of bunch length measurements at the level of ~ 100 fs. As the bunch length becomes shorter, it is important to know and be able to measure the limitations of the instrument in terms of shortest measurable bunch length. In this paper we describe an experiment using a blackbody source with the modified Martin-Puplett interferometer that is routine- ly used for bunch length measurements at the JLab FEL, as a way to estimate the shortest, measurable bunch length. The limitation comes from high frequency cut-off of the wire-grid polarizer currently used and is estimated to be 50 fs RMS. The measurements are made with the same Golay cell detector that is used for beam measure- ments. We demonstrate that, even though the blackbody source is many orders of magnitude less bright than the coherent transition or synchrotron radiation, it can be used for the measurements and gives a very good signal to noise ratio in combination with lock-in detection. We also compare the measurements made in air and in vacuum to characterize the very strong effect of the atmospheric absorption.

  12. Optimising Blackbody Cavity Shape for Spatially Uniform Integrated Emissivity

    NASA Astrophysics Data System (ADS)

    Saunders, P.

    2017-01-01

    The emissivity of a blackbody cavity, as seen by a radiation thermometer viewing the cavity, depends on both the field of view of the thermometer and the distribution of local effective emissivity values within the field of view. For cylindro-conical cavities, the local effective emissivity generally attains a maximum value at the apex of the cone and drops along the conical section. Thus, radiation thermometers with different fields of view see different blackbody emissivity values. This impacts, particularly, on the calibration of wide-angle low-temperature radiation thermometers and thermal imaging systems where each pixel responds to a different radiance. The spatial uniformity of the effective emissivity profile depends principally on the cone angle, with a weaker dependence on the length-to-diameter ratio of the cavity, the intrinsic emissivity of the cavity surfaces, and the temperature gradient along the cavity. In this paper, a nonlinear least-squares method is used to determine the optimal cone angle as a function of the cavity parameters. It is concluded that full cone angles close to 160° provide the flattest effective emissivity profile across the conical section of the cavity for typical cavity parameters. A method is also described for calculating the value of integrated emissivity, which includes the umbral and penumbral regions seen by an imaging radiation thermometer.

  13. Calibration and investigation of infrared camera systems applying blackbody radiation

    NASA Astrophysics Data System (ADS)

    Hartmann, Juergen; Fischer, Joachim

    2001-03-01

    An experimental facility is presented, which allows calibration and detailed investigation of infrared camera systems. Various blackbodies operating in the temperature range from -60 degree(s)C up to 3000 degree(s)C serve as standard radiation sources, enabling calibration of camera systems in a wide temperature and spectral range with highest accuracy. Quantitative results and precise long-term investigations, especially in detecting climatic trends, require accurate traceability to the International Temperature Scale of 1990 (ITS-90). For the used blackbodies the traceability to ITS- 90 is either realized by standard platinum resistance thermometers (in the temperature range below 962 degree(s)C) or by absolute and relative radiometry (in the temperature range above 962 degree(s)C). This traceability is fundamental for implementation of quality assurance systems and realization of different standardizations, for example according ISO 9000. For investigation of the angular and the temperature resolution our set-up enables minimum resolvable (MRTD) and minimum detectable temperature difference (MDTD) measurements in the various temperature ranges. A collimator system may be used to image the MRTD and MDTD targets to infinity. As internal calibration of infrared camera systems critically depends on the temperature of the surrounding, the calibration and investigation of the cameras is performed in a climate box, which allows a detailed controlling of the environmental parameters like humidity and temperature. Experimental results obtained for different camera systems are presented and discussed.

  14. A Blackbody Microwave Source for CMB Polarimeter Development

    NASA Astrophysics Data System (ADS)

    Lindman, Alec

    2014-03-01

    I present an evolved design for a thermally isolated blackbody source operating at 90 GHz and 120 GHz, frequencies of interest to Cosmic Microwave Background measurements. The NASA GSFC Experimental Cosmology lab is developing transition edge sensor bolometers for the CLASS and PIPER missions to measure CMB polarization; the source described here is for use in an existing 150 mK test package to quantify the detectors' properties. The design is optimized to minimize heat loading into the ADR and cryocoolers by employing a Kevlar kinematic suspension and additional thermal breaks. The blackbody light is coupled to a detector by means of an electroformed waveguide, which is mated to the source by an ultraprecise ring-centered flange design; this precision is critical to maintain the vacuum gap between the heated source and the cold waveguide, which is an order of magnitude smaller than the allowable misalignment of the standard military-spec microwave flange design. The source will provide at least 50% better thermal isolation than the existing 40 GHz source, as well as a smaller thermal time constant to enable faster measurement cycles. Special thanks to Dr. David Chuss at GSFC, and the Society of Physics Students.

  15. Blackbody radiation shift in the Rb87 frequency standard

    NASA Astrophysics Data System (ADS)

    Safronova, M. S.; Jiang, Dansha; Safronova, U. I.

    2010-08-01

    The operation of atomic clocks is generally carried out at room temperature, whereas the definition of the second refers to the clock transition in an atom at absolute zero. This implies that the clock transition frequency should be corrected in practice for the effect of finite temperature, of which the leading contributor is the blackbody radiation (BBR) shift. Experimental measurements of the BBR shifts are difficult. In this work, we have calculated the blackbody radiation shift of the ground-state hyperfine microwave transition in Rb87 using the relativistic all-order method and carried out a detailed evaluation of the accuracy of our final value. Particular care is taken to accurately account for the contributions from highly excited states. Our predicted value for the Stark coefficient, kS=-1.240(4)×10-10Hz/(V/m)2, is three times more accurate than the previous calculation [E. J. Angstman, V. A. Dzuba, and V. V. Flambaum, Phys. Rev. APLRAAN1050-294710.1103/PhysRevA.74.023405 74, 023405 (2006)].

  16. Radiative effects of absorbing aerosols over northeastern India: Observations and model simulations

    NASA Astrophysics Data System (ADS)

    Gogoi, Mukunda M.; Babu, S. Suresh; Moorthy, K. Krishna; Bhuyan, Pradip Kumar; Pathak, Binita; Subba, Tamanna; Chutia, Lakhima; Kundu, Shyam Sundar; Bharali, Chandrakala; Borgohain, Arup; Guha, Anirban; De, Barin Kumar; Singh, Brajamani; Chin, Mian

    2017-01-01

    Multiyear measurements of spectral properties of aerosol absorption are examined over four geographically distinct locations of northeastern India. Results indicated significant spatiotemporal variation in aerosol absorption coefficients (σabs) with highest values in winter and lowest in monsoon. The western parts of the region, close to the outflow of Indo-Gangetic Plains, showed higher values of σabs and black carbon (BC) concentration—mostly associated with fossil fuel combustion. But, the eastern parts showed higher contributions from biomass-burning aerosols, as much as 20-25% to the total aerosol absorption, conspicuously during premonsoon season. This is attributed to a large number of burning activities over the Southeast Asian region, as depicted from Moderate Resolution Imaging Spectroradiometer fire count maps, whose spatial extent and magnitude peaks during March/April. The nearly consistent high values of aerosol index (AI) and layer height from Ozone Monitoring Instrument indicate the presence of absorbing aerosols in the upper atmosphere. The observed seasonality has been captured fairly well by Goddard Chemistry Aerosol Radiation and Transport (GOCART) as well as Weather Research and Forecasting-Chemistry (WRF-Chem) model simulations. The ratio of column-integrated optical depths due to particulate organic matter and BC from GOCART showed good coincidence with satellite-based observations, indicating the increased vertical dispersion of absorbing aerosols, probably by the additional local convection due to higher fire radiative power caused by the intense biomass-burning activities. In the WRF-Chem though underperformed by different magnitude in winter, the values are closer or overestimated near the burnt areas. Atmospheric forcing due to BC was highest ( 30 Wm-2) over the western part associated with the fossil fuel combustion.

  17. Radiator standards for accurate IR calibrations in remote sensing based on heatpipe blackbodies

    NASA Astrophysics Data System (ADS)

    Hartmann, Juergen; Fischer, Joachim

    1999-09-01

    The demand of instrumentation in the field of remote sensing is increasing rapidly. For international compatibility, for reliable results and precise long-term investigation, necessary for example in the measurement of climatic trends, accurate traceability of the results to international standards or SI-units is mandatory. Additionally, interpretation of the results strongly requires a careful evaluation of the involved errors and the resulting uncertainties in order to allow for a rating of the obtained results. For that purpose quality assurance was introduced, not only for industrial fabrication, but also, and with increasing tendency, for industrial and scientific research. As an overview, the necessity and the possibilities of quality assurance in the area of remote sensing are discussed. Taking remote sensing of temperature as an example, the general approach is described. For that purpose, a description of heatpipe blackbodies used as standard radiation sources and of the apparatus for measuring the area of the beam limiting apertures is given. We also introduce the applied mathematical model for determination of the emissivity of the blackbodies, which crucially influenced the detected radiation temperature and the uncertainty. Finally the evaluation procedure of the uncertainties is described and a sophisticated estimation of the overall uncertainty is presented.

  18. A Computational Approach for Model Update of an LS-DYNA Energy Absorbing Cell

    NASA Technical Reports Server (NTRS)

    Horta, Lucas G.; Jackson, Karen E.; Kellas, Sotiris

    2008-01-01

    NASA and its contractors are working on structural concepts for absorbing impact energy of aerospace vehicles. Recently, concepts in the form of multi-cell honeycomb-like structures designed to crush under load have been investigated for both space and aeronautics applications. Efforts to understand these concepts are progressing from tests of individual cells to tests of systems with hundreds of cells. Because of fabrication irregularities, geometry irregularities, and material properties uncertainties, the problem of reconciling analytical models, in particular LS-DYNA models, with experimental data is a challenge. A first look at the correlation results between single cell load/deflection data with LS-DYNA predictions showed problems which prompted additional work in this area. This paper describes a computational approach that uses analysis of variance, deterministic sampling techniques, response surface modeling, and genetic optimization to reconcile test with analysis results. Analysis of variance provides a screening technique for selection of critical parameters used when reconciling test with analysis. In this study, complete ignorance of the parameter distribution is assumed and, therefore, the value of any parameter within the range that is computed using the optimization procedure is considered to be equally likely. Mean values from tests are matched against LS-DYNA solutions by minimizing the square error using a genetic optimization. The paper presents the computational methodology along with results obtained using this approach.

  19. A quasi-static continuum model describing interactions between plasmons and non-absorbing biomolecules

    NASA Astrophysics Data System (ADS)

    Salary, Mohammad Mahdi; Mosallaei, Hossein

    2015-06-01

    Interactions between the plasmons of noble metal nanoparticles and non-absorbing biomolecules forms the basis of the plasmonic sensors, which have received much attention. Studying these interactions can help to exploit the full potentials of plasmonic sensors in quantification and analysis of biomolecules. Here, a quasi-static continuum model is adopted for this purpose. We present a boundary-element method for computing the optical response of plasmonic particles to the molecular binding events by solving the Poisson equation. The model represents biomolecules with their molecular surfaces, thus accurately accounting for the influence of exact binding conformations as well as structural differences between different proteins on the response of plasmonic nanoparticles. The linear systems arising in the method are solved iteratively with Krylov generalized minimum residual algorithm, and the acceleration is achieved by applying precorrected-Fast Fourier Transformation technique. We apply the developed method to investigate interactions of biotinylated gold nanoparticles (nanosphere and nanorod) with four different types of biotin-binding proteins. The interactions are studied at both ensemble and single-molecule level. Computational results demonstrate the ability of presented model for analyzing realistic nanoparticle-biomolecule configurations. The method can provide comprehensive study for wide variety of applications, including protein structures, monitoring structural and conformational transitions, and quantification of protein concentrations. In addition, it is suitable for design and optimization of the nano-plasmonic sensors.

  20. Linear behavior of a preformed microbubble containing light absorbing nanoparticles: insight from a mathematical model.

    PubMed

    Sassaroli, E; Li, K C P; O'Neill, B E

    2009-11-01

    Microbubbles are used as ultrasonic contrast agents in medical imaging because of their highly efficient scattering properties. Gold nanoparticles absorb specific wavelengths of optical radiation very effectively with the subsequent generation of thermo-acoustic waves in the surrounding medium. A theoretical and numerical analysis of the possibility of inducing radial oscillations in a pre-existing spherical microbubble, through the laser excitation of gold nanoparticles contained within, is presented. A description of such a system can be obtained in terms of a confined two-phase model, with the nanoparticles suspended in a confined region of gas, surrounded by a liquid. The Rayleigh-Plesset equation is assumed to be valid at the boundary between the gas and the liquid. The confined two-phase model is solved in linear approximation. The system is diagonalized and the general solution is obtained. This solution is in the form of exponentially decaying oscillatory functions for the temperature and pressure inside the bubble, and radial oscillations of the bubble boundary. It was found that, for the right size of bubbles, the oscillatory behavior takes place in the low megahertz range, which is ideal for medical applications. This study suggests the possibility of new applications of microbubbles in photoacoustic imaging.

  1. Multicritical absorbing phase transition in a class of exactly solvable models

    NASA Astrophysics Data System (ADS)

    Chatterjee, Arijit; Mohanty, P. K.

    2016-12-01

    We study diffusion of hard-core particles on a one-dimensional periodic lattice subjected to a constraint that the separation between any two consecutive particles does not increase beyond a fixed value n +1 ; an initial separation larger than n +1 can however decrease. These models undergo an absorbing state phase transition when the conserved particle density of the system falls below a critical threshold ρc=1 /(n +1 ) . We find that the ϕk, the density of 0-clusters (0 representing vacancies) of size 0 ≤k models can be written in matrix product form to obtain analytically the static exponents βk=n -k and ν =1 =η corresponding to each ϕk. We also show from numerical simulations that, starting from a natural condition, ϕk(t ) s decay as t-αk with αk=(n -k ) /2 even though other dynamic exponents νt=2 =z are independent of k ; this ensures the validity of scaling laws β =α νt and νt=z ν .

  2. Influence of the Opening of a Blackbody Cavity Measured at the Ag and Cu ITS-90 Fixed Points

    NASA Astrophysics Data System (ADS)

    Bourson, F.; Sadli, M.; Rougié, B.; Briaudeau, S.; Kozlova, O.

    2014-04-01

    The International Temperature Scale of 1990 blackbody fixed points are commonly composed of a graphite crucible containing a pure metal enclosing a radiating blackbody cavity. The shape of the cavity is determined to behave as much as possible as a perfect blackbody; however, the opening from which the radiance is measured induces radiative losses. The measured temperature is therefore underestimated by a few tens of millikelvins at C, compared to that of a perfect blackbody. The difference is due, on the one hand, to the drop of emissivity caused by the opening, and on the other hand, to the temperature drop between the solid/liquid interface and the inner wall of the cavity, observed by the radiation thermometer. The temperature drop is generally estimated by modeling the emissivity and the temperature difference across the cavity wall. This approach is relevant as long as the temperature distribution along the cavity and the graphite properties are known, but in many cases, the lack of data does not allow precise determination of the corrections. The corrections for the temperature drop and emissivity drop, which both depend on the cavity opening, can be determined experimentally with a low uncertainty by measuring the temperature of a fixed point for different cavity openings. To be significant, the measurement requires a source stable within a few millikelvins. In this study, this constraint has been solved by changing the cavity opening during the phase transition of the fixed point, with a rotating wheel supporting apertures of different dimensions. Measurements have been performed at the Ag and Cu fixed points during the freezing plateaus. Experimental results are presented and compared to those obtained by modeling.

  3. Multipolar blackbody radiation shifts for single-ion clocks

    NASA Astrophysics Data System (ADS)

    Arora, Bindiya; Nandy, D. K.; Sahoo, B. K.

    2012-01-01

    Appraising the projected 10-18 fractional uncertainty in the optical frequency standards using singly ionized ions, we estimate the blackbody radiation (BBR) shifts due to the magnetic dipole (M1) and electric quadrupole (E2) multipoles of the applied external electromagnetic field. Multipolar scalar polarizabilities are determined for the singly ionized calcium (Ca+) and strontium (Sr+) ions using the relativistic coupled-cluster method, though the theory can be exercised for any single-ion clocks. The expected energy shifts for the respective clock transitions are estimated to be 4.38(3)×10-4 Hz for Ca+ and 9.50(7)×10-5 Hz for Sr+. These shifts are large enough and may be a prerequisite for the frequency standards to achieve the foreseen 10-18 precision goal.

  4. Oscillatory phenomena and Q switching in a model for laser with a saturable absorber

    SciTech Connect

    Antoranz, J.C.; Gea, J.; Velarde, M.G.

    1981-12-28

    Sufficiently long population decay times and sufficiently short dipole decay times in a single-mode laser with saturable absorber permit passive Q switching in the form of a hard-mode sustained relaxation oscillation.

  5. Modeling of optically controlled reflective bistability in a vertical cavity semiconductor saturable absorber

    NASA Astrophysics Data System (ADS)

    Mishra, L.

    2015-05-01

    Bistability switching between two optical signals has been studied theoretically utilizing the concept of cross absorption modulation in a vertical cavity semiconductor saturable absorber (VCSSA). The probe beam is fixed at a wavelength other than the low power cavity resonance wavelength, which exhibits bistable characteristic by controlling the power of a pump beam (λpump≠λprobe). The cavity nonlinear effects that arises simultaneously from the excitonic absorption bleaching, and the carrier induced nonlinear index change has been considered in the model. The high power absorption in the active region introduces thermal effects within the nonlinear cavity due to which the effective cavity length changes. This leads to a red-shift of the cavity resonance wavelength, which results a change in phase of the optical fields within the cavity. In the simulation, the phase-change due to this resonance shifting is considered to be constant over time, and it assumes the value corresponding to the maximum input power. Further, an initial phase detuning of the probe beam has been considered to investigate its effect on switching. It is observed from the simulated results that, the output of the probe beam exhibits either clockwise or counter-clockwise bistability, depending on its initial phase detuning.

  6. Light-absorbing particles in snow and ice: Measurement and modeling of climatic and hydrological impact

    NASA Astrophysics Data System (ADS)

    Qian, Yun; Yasunari, Teppei J.; Doherty, Sarah J.; Flanner, Mark G.; Lau, William K. M.; Ming, Jing; Wang, Hailong; Wang, Mo; Warren, Stephen G.; Zhang, Rudong

    2015-01-01

    Light absorbing particles (LAP, e.g., black carbon, brown carbon, and dust) influence water and energy budgets of the atmosphere and snowpack in multiple ways. In addition to their effects associated with atmospheric heating by absorption of solar radiation and interactions with clouds, LAP in snow on land and ice can reduce the surface reflectance (a.k.a., surface darkening), which is likely to accelerate the snow aging process and further reduces snow albedo and increases the speed of snowpack melt. LAP in snow and ice (LAPSI) has been identified as one of major forcings affecting climate change, e.g. in the fourth and fifth assessment reports of IPCC. However, the uncertainty level in quantifying this effect remains very high. In this review paper, we document various technical methods of measuring LAPSI and review the progress made in measuring the LAPSI in Arctic, Tibetan Plateau and other mid-latitude regions. We also report the progress in modeling the mass concentrations, albedo reduction, radiative forcing, and climatic and hydrological impact of LAPSI at global and regional scales. Finally we identify some research needs for reducing the uncertainties in the impact of LAPSI on global and regional climate and the hydrological cycle.

  7. Light-absorbing Particles in Snow and Ice: Measurement and Modeling of Climatic and Hydrological Impact

    SciTech Connect

    Qian, Yun; Yasunari, Teppei J.; Doherty, Sarah J.; Flanner, M. G.; Lau, William K.; Ming, J.; Wang, Hailong; Wang, Mo; Warren, Stephen G.; Zhang, Rudong

    2015-01-01

    Light absorbing particles (LAP, e.g., black carbon, brown carbon, and dust) influence water and energy budgets of the atmosphere and snowpack in multiple ways. In addition to their effects associated with atmospheric heating by absorption of solar radiation and interactions with clouds, LAP in snow on land and ice can reduce the surface reflectance (a.k.a., surface darkening), which is likely to accelerate the snow aging process and further reduces snow albedo and increases the speed of snowpack melt. LAP in snow and ice (LAPSI) has been identified as one of major forcings affecting climate change, e.g. in the fourth and fifth assessment reports of IPCC. However, the uncertainty level in quantifying this effect remains very high. In this review paper, we document various technical methods of measuring LAPSI and review the progress made in measuring the LAPSI in Arctic, Tibetan Plateau and other mid-latitude regions. We also report the progress in modeling the mass concentrations, albedo reduction, radiative forcing, andclimatic and hydrological impact of LAPSI at global and regional scales. Finally we identify some research needs for reducing the uncertainties in the impact of LAPSI on global and regional climate and the hydrological cycle.

  8. Modeling the tight focusing of beams in absorbing media with Monte Carlo simulations

    NASA Astrophysics Data System (ADS)

    Brandes, Arnd R.; Elmaklizi, Ahmed; Akarçay, H. Günhan; Kienle, Alwin

    2014-11-01

    A severe drawback to the scalar Monte Carlo (MC) method is the difficulty of introducing diffraction when simulating light propagation. This hinders, for instance, the accurate modeling of beams focused through microscope objectives, where the diffraction patterns in the focal plane are of great importance in various applications. Here, we propose to overcome this issue by means of a direct extinction method. In the MC simulations, the photon paths' initial positions are sampled from probability distributions which are calculated with a modified angular spectrum of the plane waves technique. We restricted our study to the two-dimensional case, and investigated the feasibility of our approach for absorbing yet nonscattering materials. We simulated the focusing of collimated beams with uniform profiles through microscope objectives. Our results were compared with those yielded by independent simulations using the finite-difference time-domain method. Very good agreement was achieved between the results of both methods, not only for the power distributions around the focal region including diffraction patterns, but also for the distribution of the energy flow (Poynting vector).

  9. A comprehensive simulation model of the performance of photochromic films in absorbance-modulation-optical-lithography

    NASA Astrophysics Data System (ADS)

    Majumder, Apratim; Helms, Phillip L.; Andrew, Trisha L.; Menon, Rajesh

    2016-03-01

    Optical lithography is the most prevalent method of fabricating micro-and nano-scale structures in the semiconductor industry due to the fact that patterning using photons is fast, accurate and provides high throughput. However, the resolution of this technique is inherently limited by the physical phenomenon of diffraction. Absorbance-Modulation-Optical Lithography (AMOL), a recently developed technique has been successfully demonstrated to be able to circumvent this diffraction limit. AMOL employs a dual-wavelength exposure system in conjunction with spectrally selective reversible photo-transitions in thin films of photochromic molecules to achieve patterning of features with sizes beyond the far-field diffraction limit. We have developed a finite-element-method based full-electromagnetic-wave solution model that simulates the photo-chemical processes that occur within the thin film of the photochromic molecules under illumination by the exposure and confining wavelengths in AMOL. This model allows us to understand how the material characteristics influence the confinement to sub-diffraction dimensions, of the transmitted point spread function (PSF) of the exposure wavelength inside the recording medium. The model reported here provides the most comprehensive analysis of the AMOL process to-date, and the results show that the most important factors that govern the process, are the polarization of the two beams, the ratio of the intensities of the two wavelengths, the relative absorption coefficients and the concentration of the photochromic species, the thickness of the photochromic layer and the quantum yields of the photoreactions at the two wavelengths. The aim of this work is to elucidate the requirements of AMOL in successfully circumventing the far-field diffraction limit.

  10. A Physically Based Algorithm for Non-Blackbody Correction of Cloud-Top Temperature and Application to Convection Study

    NASA Technical Reports Server (NTRS)

    Wang, Chunpeng; Lou, Zhengzhao Johnny; Chen, Xiuhong; Zeng, Xiping; Tao, Wei-Kuo; Huang, Xianglei

    2014-01-01

    Cloud-top temperature (CTT) is an important parameter for convective clouds and is usually different from the 11-micrometers brightness temperature due to non-blackbody effects. This paper presents an algorithm for estimating convective CTT by using simultaneous passive [Moderate Resolution Imaging Spectroradiometer (MODIS)] and active [CloudSat 1 Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO)] measurements of clouds to correct for the non-blackbody effect. To do this, a weighting function of the MODIS 11-micrometers band is explicitly calculated by feeding cloud hydrometer profiles from CloudSat and CALIPSO retrievals and temperature and humidity profiles based on ECMWF analyses into a radiation transfer model.Among 16 837 tropical deep convective clouds observed by CloudSat in 2008, the averaged effective emission level (EEL) of the 11-mm channel is located at optical depth; approximately 0.72, with a standard deviation of 0.3. The distance between the EEL and cloud-top height determined by CloudSat is shown to be related to a parameter called cloud-top fuzziness (CTF), defined as the vertical separation between 230 and 10 dBZ of CloudSat radar reflectivity. On the basis of these findings a relationship is then developed between the CTF and the difference between MODIS 11-micrometers brightness temperature and physical CTT, the latter being the non-blackbody correction of CTT. Correction of the non-blackbody effect of CTT is applied to analyze convective cloud-top buoyancy. With this correction, about 70% of the convective cores observed by CloudSat in the height range of 6-10 km have positive buoyancy near cloud top, meaning clouds are still growing vertically, although their final fate cannot be determined by snapshot observations.

  11. Fermi's golden rule for N -body systems in a blackbody radiation

    NASA Astrophysics Data System (ADS)

    Ostilli, Massimo; Presilla, Carlo

    2016-09-01

    We review the calculation of Fermi's golden rule for a system of N -body dipoles, magnetic or electric, weakly interacting with a blackbody radiation. By using the magnetic or electric field-field correlation function evaluated in the 1960s for blackbody radiation, we deduce a general formula for the transition rates and study its limiting, fully coherent or fully incoherent, regimes.

  12. Upconversion luminescence and blackbody radiation in tetragonal YSZ co-doped with Tm3+ and Yb3+

    NASA Astrophysics Data System (ADS)

    Soares, M. R. N.; Ferro, M.; Costa, F. M.; Monteiro, T.

    2015-11-01

    Lanthanide doped inorganic nanoparticles with upconversion luminescence are of utmost importance for biomedical applications, solid state lighting and photovoltaics. In this work we studied the downshifted luminescence, upconversion luminescence (UCL) and blackbody radiation of tetragonal yttrium stabilized zirconia co-doped with Tm3+ and Yb3+ single crystals and nanoparticles produced by laser floating zone and laser ablation in liquids, respectively. The photoluminescence (PL) and PL excitation (PLE) were investigated at room temperature (RT). PL spectra exhibit the characteristic lines in UV, blue/green, red and NIR regions of the Tm3+ (4f12) under resonant excitation into the high energy 2S+1LJ multiplets. Under NIR excitation (980 nm), the samples placed in air display an intense NIR at ~800 nm due to the 1G4 --> 3H5/3H4 --> 3H6 transitions. Additionally, red, blue/green and ultraviolet UCL is observed arising from higher excited 1G4 and 1D2 multiplets. The power excitation dependence of the UCL intensity indicated that 2-3 low energy absorbed photons are involved in the UCL for low power levels, while for high powers, the identified saturation is dependent on the material size with a enhanced effect on the NPs. The temperature dependence of the UCL was investigated for single crystals and targets used in the ablation. An overall increase of the integrated intensity was found to occur between 12 K and the RT. The thermally activated process is described by activation energies of 10 meV and 30 meV for single crystals and targets, respectively. For the NPs, the UCL was found to be strongly sensitive to pressure conditions. Under vacuum conditions, instead of the narrow lines of the Tm3+, a wide blackbody radiation was detected, responsible for the change in the emission colour from blue to orange. This phenomenon is totally reversible when the NPs are placed at ambient pressure. The UCL/blackbody radiation in the nanosized material exhibits non-contact pressure

  13. Upconversion luminescence and blackbody radiation in tetragonal YSZ co-doped with Tm(3+) and Yb(3+).

    PubMed

    Soares, M R N; Ferro, M; Costa, F M; Monteiro, T

    2015-12-21

    Lanthanide doped inorganic nanoparticles with upconversion luminescence are of utmost importance for biomedical applications, solid state lighting and photovoltaics. In this work we studied the downshifted luminescence, upconversion luminescence (UCL) and blackbody radiation of tetragonal yttrium stabilized zirconia co-doped with Tm(3+) and Yb(3+) single crystals and nanoparticles produced by laser floating zone and laser ablation in liquids, respectively. The photoluminescence (PL) and PL excitation (PLE) were investigated at room temperature (RT). PL spectra exhibit the characteristic lines in UV, blue/green, red and NIR regions of the Tm(3+) (4f(12)) under resonant excitation into the high energy (2S+1)LJ multiplets. Under NIR excitation (980 nm), the samples placed in air display an intense NIR at ∼800 nm due to the (1)G4→(3)H5/(3)H4→(3)H6 transitions. Additionally, red, blue/green and ultraviolet UCL is observed arising from higher excited (1)G4 and (1)D2 multiplets. The power excitation dependence of the UCL intensity indicated that 2-3 low energy absorbed photons are involved in the UCL for low power levels, while for high powers, the identified saturation is dependent on the material size with a enhanced effect on the NPs. The temperature dependence of the UCL was investigated for single crystals and targets used in the ablation. An overall increase of the integrated intensity was found to occur between 12 K and the RT. The thermally activated process is described by activation energies of 10 meV and 30 meV for single crystals and targets, respectively. For the NPs, the UCL was found to be strongly sensitive to pressure conditions. Under vacuum conditions, instead of the narrow lines of the Tm(3+), a wide blackbody radiation was detected, responsible for the change in the emission colour from blue to orange. This phenomenon is totally reversible when the NPs are placed at ambient pressure. The UCL/blackbody radiation in the nanosized material exhibits

  14. Vapor shielding models and the energy absorbed by divertor targets during transient events

    NASA Astrophysics Data System (ADS)

    Skovorodin, D. I.; Pshenov, A. A.; Arakcheev, A. S.; Eksaeva, E. A.; Marenkov, E. D.; Krasheninnikov, S. I.

    2016-02-01

    The erosion of divertor targets caused by high heat fluxes during transients is a serious threat to ITER operation, as it is going to be the main factor determining the divertor lifetime. Under the influence of extreme heat fluxes, the surface temperature of plasma facing components can reach some certain threshold, leading to an onset of intense material evaporation. The latter results in formation of cold dense vapor and secondary plasma cloud. This layer effectively absorbs the energy of the incident plasma flow, turning it into its own kinetic and internal energy and radiating it. This so called vapor shielding is a phenomenon that may help mitigating the erosion during transient events. In particular, the vapor shielding results in saturation of energy (per unit surface area) accumulated by the target during single pulse of heat load at some level Emax. Matching this value is one of the possible tests to verify complicated numerical codes, developed to calculate the erosion rate during abnormal events in tokamaks. The paper presents three very different models of vapor shielding, demonstrating that Emax depends strongly on the heat pulse duration, thermodynamic properties, and evaporation energy of the irradiated target material. While its dependence on the other shielding details such as radiation capabilities of material and dynamics of the vapor cloud is logarithmically weak. The reason for this is a strong (exponential) dependence of the target material evaporation rate, and therefore the "strength" of vapor shield on the target surface temperature. As a result, the influence of the vapor shielding phenomena details, such as radiation transport in the vapor cloud and evaporated material dynamics, on the Emax is virtually completely masked by the strong dependence of the evaporation rate on the target surface temperature. However, the very same details define the amount of evaporated particles, needed to provide an effective shielding to the target, and

  15. Modeling investigation of light-absorbing aerosols in the Amazon Basin during the wet season

    NASA Astrophysics Data System (ADS)

    Wang, Qiaoqiao; Saturno, Jorge; Chi, Xuguang; Walter, David; Lavric, Jost V.; Moran-Zuloaga, Daniel; Ditas, Florian; Pöhlker, Christopher; Brito, Joel; Carbone, Samara; Artaxo, Paulo; Andreae, Meinrat O.

    2016-11-01

    We use a global chemical transport model (GEOS-Chem) to interpret observed light-absorbing aerosols in Amazonia during the wet season. Observed aerosol properties, including black carbon (BC) concentration and light absorption, at the Amazon Tall Tower Observatory (ATTO) site in the central Amazon have relatively low background levels but frequently show high peaks during the study period of January-April 2014. With daily temporal resolution for open fire emissions and modified aerosol optical properties, our model successfully captures the observed variation in fine/coarse aerosol and BC concentrations as well as aerosol light absorption and its wavelength dependence over the Amazon Basin. The source attribution in the model indicates the important influence of open fire on the observed variances of aerosol concentrations and absorption, mainly from regional sources (northern South America) and from northern Africa. The contribution of open fires from these two regions is comparable, with the latter becoming more important in the late wet season. The analysis of correlation and enhancement ratios of BC versus CO suggests transport times of < 3 days for regional fires and ˜ 11 days for African plumes arriving at ATTO during the wet season. The model performance of long-range transport of African plumes is also evaluated with observations from AERONET, MODIS, and CALIOP. Simulated absorption aerosol optical depth (AAOD) averaged over the wet season is lower than 0.0015 over the central Amazon, including the ATTO site. We find that more than 50 % of total absorption at 550 nm is from BC, except for the northeastern Amazon and the Guianas, where the influence of dust becomes significant (up to 35 %). The brown carbon contribution is generally between 20 and 30 %. The distribution of absorption Ångström exponents (AAE) suggests more influence from fossil fuel combustion in the southern part of the basin (AAE ˜ 1) but more open fire and dust influence in the

  16. Improved Blackbody Temperature Sensors for a Vacuum Furnace

    NASA Technical Reports Server (NTRS)

    Farmer, Jeff; Coppens, Chris; O'Dell, J. Scott; McKechnie, Timothy N.; Schofield, Elizabeth

    2009-01-01

    Some improvements have been made in the design and fabrication of blackbody sensors (BBSs) used to measure the temperature of a heater core in a vacuum furnace. Each BBS consists of a ring of thermally conductive, high-melting-temperature material with two tantalum-sheathed thermocouples attached at diametrically opposite points. The name "blackbody sensor" reflects the basic principle of operation. Heat is transferred between the ring and the furnace heater core primarily by blackbody radiation, heat is conducted through the ring to the thermocouples, and the temperature of the ring (and, hence, the temperature of the heater core) is measured by use of the thermocouples. Two main requirements have guided the development of these BBSs: (1) The rings should have as high an emissivity as possible in order to maximize the heat-transfer rate and thereby maximize temperature-monitoring performance and (2) the thermocouples must be joined to the rings in such a way as to ensure long-term, reliable intimate thermal contact. The problem of fabricating a BBS to satisfy these requirements is complicated by an application-specific prohibition against overheating and thereby damaging nearby instrumentation leads through the use of conventional furnace brazing or any other technique that involves heating the entire BBS and its surroundings. The problem is further complicated by another application-specific prohibition against damaging the thin tantalum thermocouple sheaths through the use of conventional welding to join the thermocouples to the ring. The first BBS rings were made of graphite. The tantalum-sheathed thermocouples were attached to the graphite rings by use of high-temperature graphite cements. The ring/thermocouple bonds thus formed were found to be weak and unreliable, and so graphite rings and graphite cements were abandoned. Now, each BBS ring is made from one of two materials: either tantalum or a molybdenum/titanium/zirconium alloy. The tantalum

  17. Vapor shielding models and the energy absorbed by divertor targets during transient events

    SciTech Connect

    Skovorodin, D. I. Arakcheev, A. S.; Pshenov, A. A.; Eksaeva, E. A.; Marenkov, E. D.; Krasheninnikov, S. I.

    2016-02-15

    The erosion of divertor targets caused by high heat fluxes during transients is a serious threat to ITER operation, as it is going to be the main factor determining the divertor lifetime. Under the influence of extreme heat fluxes, the surface temperature of plasma facing components can reach some certain threshold, leading to an onset of intense material evaporation. The latter results in formation of cold dense vapor and secondary plasma cloud. This layer effectively absorbs the energy of the incident plasma flow, turning it into its own kinetic and internal energy and radiating it. This so called vapor shielding is a phenomenon that may help mitigating the erosion during transient events. In particular, the vapor shielding results in saturation of energy (per unit surface area) accumulated by the target during single pulse of heat load at some level E{sub max}. Matching this value is one of the possible tests to verify complicated numerical codes, developed to calculate the erosion rate during abnormal events in tokamaks. The paper presents three very different models of vapor shielding, demonstrating that E{sub max} depends strongly on the heat pulse duration, thermodynamic properties, and evaporation energy of the irradiated target material. While its dependence on the other shielding details such as radiation capabilities of material and dynamics of the vapor cloud is logarithmically weak. The reason for this is a strong (exponential) dependence of the target material evaporation rate, and therefore the “strength” of vapor shield on the target surface temperature. As a result, the influence of the vapor shielding phenomena details, such as radiation transport in the vapor cloud and evaporated material dynamics, on the E{sub max} is virtually completely masked by the strong dependence of the evaporation rate on the target surface temperature. However, the very same details define the amount of evaporated particles, needed to provide an effective shielding

  18. Blackbody-induced decay, excitation and ionization rates for Rydberg states in hydrogen and helium atoms

    NASA Astrophysics Data System (ADS)

    Glukhov, I. L.; Nekipelov, E. A.; Ovsiannikov, V. D.

    2010-06-01

    New features of the blackbody-induced radiation processes on Rydberg atoms were discovered on the basis of numerical data for the blackbody-induced decay Pdnl(T), excitation Penl(T) and ionization Pionnl(T) rates of nS, nP and nD Rydberg states calculated together with the spontaneous decay rates Pspnl in neutral hydrogen, and singlet and triplet helium atoms for some values of the principal quantum number n from 10 to 500 at temperatures from T = 100 K to 2000 K. The fractional rates Rd(e, ion)nl(T) = Pnld(e, ion)(T)/Pspnl equal to the ratio of the induced decay (excitation, ionization) rates to the rate of spontaneous decay were determined as functions of T and n in every series of states with a given angular momentum l = 0, 1, 2. The calculated data reveal an essential difference between the asymptotic dependence of the ionization rate Pionnl(T) and the rates of decay and excitation Pd(e)nl(T)~T/n2. The departures appear in each Rydberg series for n > 100 and introduce appreciable corrections to the formula of Cooke and Gallagher. Two different approximation formulae are proposed on the basis of the numerical data, one for Rd(e)nl(T) and another one for Rionnl(T), which reproduce the calculated values in wide ranges of principal quantum number from n = 10 to 1000 and temperatures between T = 100 K and T = 2000 K with an accuracy of 2% or better. Modified Fues' model potential approach was used for calculating matrix elements of bound-bound and bound-free radiation transitions in helium.

  19. Precision Calculation of Blackbody Radiation Shifts for Optical Frequency Metrology

    SciTech Connect

    Safronova, M. S.; Kozlov, M. G.; Clark, Charles W.

    2011-09-30

    We show that three group IIIB divalent ions, B{sup +}, Al{sup +}, and In{sup +}, have anomalously small blackbody radiation (BBR) shifts of the ns{sup 2} {sup 1}S{sub 0}-nsnp {sup 3}P{sub 0}{sup o} clock transitions. The fractional BBR shifts for these ions are at least 10 times smaller than those of any other present or proposed optical frequency standards at the same temperature, and are less than 0.3% of the Sr clock shift. We have developed a hybrid configuration-interaction + coupled-cluster method that provides accurate treatment of correlation corrections in such ions and yields a rigorous upper bound on the uncertainty of the final results. We reduce the BBR contribution to the fractional frequency uncertainty of the Al{sup +} clock to 4x10{sup -19} at T=300 K. We also reduce the uncertainties due to this effect at room temperature to 10{sup -18} level for B{sup +} and In{sup +} to facilitate further development of these systems for metrology and quantum sensing.

  20. Aqueous blackbody calibration source for millimeter-wave/terahertz metrology

    SciTech Connect

    Dietlein, Charles; Popovic, Zoya; Grossman, Erich N

    2008-10-20

    This paper describes a calibrated broadband emitter for the millimeter-wave through terahertz frequency regime, called the aqueous blackbody calibration source. Due to its extremely high absorption, liquid water is chosen as the emitter on the basis of reciprocity. The water is constrained to a specific shape (an optical trap geometry) in an expanded polystyrene (EPS) container and maintained at a selected, uniform temperature. Uncertainty in the selected radiometric temperature due to the undesirable reflectance present at a water interface is minimized by the trap geometry, ensuring that radiation incident on the entrance aperture encounters a pair of s and a pair of p reflections at 45 deg. . For water reflectance Rw of 40% at 45 deg. in W-band, this implies a theoretical effective aperture emissivity of (1-R{sup 2}wsR{sup 2}wp)>98.8%. From W-band to 450 GHz, the maximum radiometric temperature uncertainty is {+-}0.40 K, independent of water temperature. Uncertainty from 450 GHz to 1 THz is increased due to EPS scattering and absorption, resulting in a maximum uncertainty of -3 K at 1 THz.

  1. On-Orbit Operation and Performance of MODIS Blackbody

    NASA Technical Reports Server (NTRS)

    Xiong, X.; Chang, T.; Barnes, W.

    2009-01-01

    MODIS collects data in 36 spectral bands, including 20 reflective solar bands (RSB) and 16 thermal emissive bands (TES). The TEB on-orbit calibration is performed on a scan-by-scan basis using a quadratic algorithm that relates the detector response with the calibration radiance from the sensor on-board blackbody (BB). The calibration radiance is accurately determined each scan from the BB temperature measured using a set of 12 thermistors. The BB thermistors were calibrated pre-launch with traceability to the NIST temperature standard. Unlike many heritage sensors, the MODIS BB can be operated at a constant temperature or with the temperature continuously varying between instrument ambient (about 270K) and 315K. In this paper, we provide an overview of both Terra and Aqua MODIS on-board BB operations, functions, and on-orbit performance. We also examine the impact of key calibration parameters, such as BB emissivity and temperature (stability and gradient) determined from its thermistors, on the TEB calibration and Level I (LIB) data product uncertainty.

  2. Secure thermal infrared communications using engineered blackbody radiation

    PubMed Central

    Liang, Xiaoxin; Hu, Fangjing; Yan, Yuepeng; Lucyszyn, Stepan

    2014-01-01

    The thermal (emitted) infrared frequency bands, from 20–40 THz and 60–100 THz, are best known for applications in thermography. This underused and unregulated part of the spectral range offers opportunities for the development of secure communications. The ‘THz Torch' concept was recently presented by the authors. This technology fundamentally exploits engineered blackbody radiation, by partitioning thermally-generated spectral noise power into pre-defined frequency channels; the energy in each channel is then independently pulsed modulated and multiplexing schemes are introduced to create a robust form of short-range secure communications in the far/mid infrared. To date, octave bandwidth (25–50 THz) single-channel links have been demonstrated with 380 bps speeds. Multi-channel ‘THz Torch' frequency division multiplexing (FDM) and frequency-hopping spread-spectrum (FHSS) schemes have been proposed, but only a slow 40 bps FDM scheme has been demonstrated experimentally. Here, we report a much faster 1,280 bps FDM implementation. In addition, an experimental proof-of-concept FHSS scheme is demonstrated for the first time, having a 320 bps data rate. With both 4-channel multiplexing schemes, measured bit error rates (BERs) of < 10−6 are achieved over a distance of 2.5 cm. Our approach represents a new paradigm in the way niche secure communications can be established over short links. PMID:24912871

  3. Measurement and modeling of high-linearity modified uni-traveling carrier photodiode with highly-doped absorber.

    PubMed

    Pan, Huapu; Li, Zhi; Beling, Andreas; Campbell, Joe C

    2009-10-26

    The third-order intermodulation distortions of InGaAs/InP modified uni-traveling carrier photodiodes with a highly-doped p-type absorber are characterized. The third-order local intercept point is 55 dBm at low frequency (< 3 GHz) and remains as high as 47.5 dBm up to 20 GHz. The frequency characteristics of the OIP3 are well explained by an equivalent circuit model.

  4. New bone formation in a bone defect associated to dental implant using absorbable or non-absorbable membrane in a dog model

    PubMed Central

    Lopez, Maria de Almeida; Olate, Sergio; Lanata-Flores, Antonio; Pozzer, Leandro; Cavalieri-Pereira, Lucas; Cantín, Mario; Vásquez, Bélgica; de Albergaria-Barbosa, José

    2013-01-01

    The aim of this research was to determine the bone formation capacity in fenestration defects associated with dental implants using absorbable and non-absorbable membranes. Six dogs were used in the study. In both tibias of each animal 3 implants were installed, and around these 5 mm circular defects were created. The defects were covered with absorbable membranes (experimental group 1), non-absorbable membranes (experimental group 2), and the third defect was not covered (control group). At 3 and 8 weeks post-surgery, the animals were euthanized and the membranes with the bone tissue around the implants were processed for histological analysis. The statistical analysis was conducted with Tukey’s test, considering statistical significance when p<0.1. Adequate bone repair was observed in the membrane-covered defects. At 3 weeks, organization of the tissue, bone formation from the periphery of the defect and the absence of inflammatory infiltrate were observed in both experimental groups, but the defect covered with absorbable membrane presented statistically greater bone formation. At 8 weeks, both membrane-covered defects showed adequate bone formation without significant differences, although they did in fact present differences with the control defect in both periods (p>0.1). In the defects without membrane, continuous connective tissue invasions and bone repair deficiency were observed. There were no significant differences in the characteristics and volume of the neoformed bone in the defects around the implants covered by the different membranes, whereas the control defects produced significantly less bone. The use of biological membranes contributes to bone formation in three-wall defects. PMID:24228090

  5. The Fermilab Large Cold Blackbody Test Stand for CMB R&D

    SciTech Connect

    Kubik, Donna; Butler, D.; DeJongh, F.; Korienek, J.; Lindenmeyer, C.; Montes, J.; Nguyen, H.; Wilson, J.

    2012-03-18

    The Fermilab Large Cold Blackbody Test Stand can be used to expose a microwave receiver and horn assembly to a large blackbody at cryogenic temperatures (as low as 20 K). The temperature of the blackbody can be varied while keeping the receiver temperature constant, facilitating Y-factor measurements of the receiver noise temperature and gain. The test stand has recently been used for studying a QUIET-I receiver module. The test stand will be used to measure both QUIET-I and prototype QUIET-II modules.

  6. Sound Absorbers

    NASA Astrophysics Data System (ADS)

    Fuchs, H. V.; Möser, M.

    Sound absorption indicates the transformation of sound energy into heat. It is, for instance, employed to design the acoustics in rooms. The noise emitted by machinery and plants shall be reduced before arriving at a workplace; auditoria such as lecture rooms or concert halls require a certain reverberation time. Such design goals are realised by installing absorbing components at the walls with well-defined absorption characteristics, which are adjusted for corresponding demands. Sound absorbers also play an important role in acoustic capsules, ducts and screens to avoid sound immission from noise intensive environments into the neighbourhood.

  7. Quantitative impact of small angle forward scatter on whole blood oximetry using a Beer-Lambert absorbance model.

    PubMed

    LeBlanc, Serge Emile; Atanya, Monica; Burns, Kevin; Munger, Rejean

    2011-04-21

    It is well known that red blood cell scattering has an impact on whole blood oximetry as well as in vivo retinal oxygen saturation measurements. The goal of this study was to quantify the impact of small angle forward scatter on whole blood oximetry for scattering angles found in retinal oximetry light paths. Transmittance spectra of whole blood were measured in two different experimental setups: one that included small angle scatter in the transmitted signal and one that measured the transmitted signal only, at absorbance path lengths of 25, 50, 100, 250 and 500 µm. Oxygen saturation was determined by multiple linear regression in the 520-600 nm wavelength range and compared between path lengths and experimental setups. Mean calculated oxygen saturation differences between setups were greater than 10% at every absorbance path length. The deviations to the Beer-Lambert absorbance model had different spectral dependences between experimental setups, with the highest deviations found in the 520-540 nm range when scatter was added to the transmitted signal. These results are consistent with other models of forward scatter that predict different spectral dependences of the red blood cell scattering cross-section and haemoglobin extinction coefficients in this wavelength range.

  8. MODIS On-Board Blackbody Function and Performance

    NASA Technical Reports Server (NTRS)

    Xiaoxiong, Xiong; Wenny, Brian N.; Wu, Aisheng; Barnes, William

    2009-01-01

    Two MODIS instruments are currently in orbit, making continuous global observations in visible to long-wave infrared wavelengths. Compared to heritage sensors, MODIS was built with an advanced set of on-board calibrators, providing sensor radiometric, spectral, and spatial calibration and characterization during on-orbit operation. For the thermal emissive bands (TEB) with wavelengths from 3.7 m to 14.4 m, a v-grooved blackbody (BB) is used as the primary calibration source. The BB temperature is accurately measured each scan (1.47s) using a set of 12 temperature sensors traceable to NIST temperature standards. The onboard BB is nominally operated at a fixed temperature, 290K for Terra MODIS and 285K for Aqua MODIS, to compute the TEB linear calibration coefficients. Periodically, its temperature is varied from 270K (instrument ambient) to 315K in order to evaluate and update the nonlinear calibration coefficients. This paper describes MODIS on-board BB functions with emphasis on on-orbit operation and performance. It examines the BB temperature uncertainties under different operational conditions and their impact on TEB calibration and data product quality. The temperature uniformity of the BB is also evaluated using TEB detector responses at different operating temperatures. On-orbit results demonstrate excellent short-term and long-term stability for both the Terra and Aqua MODIS on-board BB. The on-orbit BB temperature uncertainty is estimated to be 10mK for Terra MODIS at 290K and 5mK for Aqua MODIS at 285K, thus meeting the TEB design specifications. In addition, there has been no measurable BB temperature drift over the entire mission of both Terra and Aqua MODIS.

  9. Anomalously small blackbody radiation shift in the Tl+ frequency standard

    NASA Astrophysics Data System (ADS)

    Zuhrianda, Z.; Safronova, M. S.; Kozlov, M. G.

    2012-02-01

    The operation of atomic clocks is generally carried out at room temperature, whereas the definition of the second refers to the clock transition in an atom at absolute zero. This implies that the clock transition frequency should be corrected in practice for the effect of finite temperature of which the leading contributor is the blackbody radiation (BBR) shift. In the present work, we used configuration interaction + coupled-cluster method to evaluate polarizabilities of the 6s21S0 and 6s6p3P0 states of the Tl+ ion; we find α0(1S0)=19.6 a.u. and α0(3P0)=21.4 a.u. The resulting BBR shift of the 6s6p3P0-6s21S0 Tl+ transition at 300 K is ΔνBBR=-0.0157(16) Hz. This result demonstrates that near cancellation of the 1S0 and 3P0 state polarizabilities in divalent B+, Al+, and In+ ions of group IIIB [M. S. Safronova , Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.107.143006 107, 143006 (2011)] continues for much heavier Tl+, leading to anomalously small BBR shift for this system. This calculation demonstrates that the BBR contribution to the fractional frequency uncertainty of the Tl+ frequency standard at 300 K is 1×10-18. We find that Tl+ has the smallest fractional BBR shift among all present or proposed frequency standards with the exception of Al+.

  10. Absorption features in the quasar HS 1603 + 3820 II. Distance to the absorber obtained from photoionisation modelling

    NASA Astrophysics Data System (ADS)

    Różańska, A.; Nikołajuk, M.; Czerny, B.; Dobrzycki, A.; Hryniewicz, K.; Bechtold, J.; Ebeling, H.

    2014-04-01

    We present the photoionisation modelling of the intrinsic absorber in the bright quasar HS 1603 + 3820. We constructed the broad-band spectral energy distribution using the optical/UV/X-ray observations from different instruments as inputs for the photoionisation calculations. The spectra from the Keck telescope show extremely high CIV to HI ratios, for the first absorber in system A, named A1. This value, together with high column density of CIV ion, place strong constraints on the photoionisation model. We used two photoionisation codes to derive the hydrogen number density at the cloud illuminated surface. By estimating bolometric luminosity of HS 1603 + 3820 using the typical formula for quasars, we calculated the distance to A1. We could find one photoionization solution, by assuming either a constant density cloud (which was modelled using CLOUDY), or a stratified cloud (which was modelled using TITAN), as well as the solar abundances. This model explained both the ionic column density of CIV and the high CIV to HI ratio. The location of A1 is 0.1 pc, and it is situated even closer to the nucleus than the possible location of the Broad Line Region in this object. The upper limit of the distance is sensitive to the adopted covering factor and the carbon abundance. Photoionisation modelling always prefers dense clouds with the number density n0 = 1010 - 1012 cm-3, which explains intrinsic absorption in HS 1603 + 3820. This number density is of the same order as that in the disk atmosphere at the implied distance of A1. Therefore, our results show that the disk wind that escapes from the outermost accretion disk atmosphere can build up dense absorber in quasars.

  11. In situ study of binding of copper by fulvic acid: comparison of differential absorbance data and model predictions.

    PubMed

    Yan, Mingquan; Dryer, Deborah; Korshin, Gregory V; Benedetti, Marc F

    2013-02-01

    This study examined the binding of copper(II) by Suwannee River fulvic acid (SRFA) using the method of differential absorbance that was used at environmentally-relevant concentrations of copper and SRFA. The pH- and metal-differential spectra were processed via numeric deconvolution to establish commonalities seen in the changes of absorbance caused by deprotonation of SRFA and its interactions with copper(II) ions. Six Gaussian bands were determined to be present in both the pH- and Cu-differential spectra. Their maxima were located, in the order of increasing wavelengths at 208 nm, 242 nm, 276 nm, 314 nm, 378 nm and 551 nm. The bands with these maxima were denoted as A0, A1, A2, A3, A4 and A5, respectively. Properties of these bands were compared with those existing in the spectra of model compounds such as sulfosalicylic acid (SSA), tannic acid (TA), and polystyrenesulfonic acid-co-maleic acid (PSMA). While none of the features observed in differential spectra of the model compound were identical to those present in the case of SRFA, Gaussian bands A1, A3 and possibly A2 were concluded to be largely attributable to a combination of responses of salicylic- and polyhydroxyphenolic groups. In contrast, bands A4 and A5 were detected in the differential spectra of SRFA only. Their nature remains to be elucidated. To examine correlations between the amount of copper(II) bound by SRFA and changes of its absorbance, differential absorbances measured at indicative wavelengths 250 nm and 400 nm were compared with the total amount of SRFA-bound copper estimated based on Visual MINTEQ calculations. This examination showed that the differential absorbances of SRFA in a wide range of pH values and copper concentrations were strongly correlated with the concentration of SRFA-bound copper. The approach presented in this study can be used to generate in situ information concerning the nature of functional groups in humic substances engaged in interactions with metals ions. This

  12. Numerical modeling of mode-locked fiber lasers with a fiber-based saturable-absorber

    NASA Astrophysics Data System (ADS)

    Wang, Long; Chong, Andy; Haus, Joseph W.

    2017-01-01

    We report fiber laser simulations with a fiber compatible, self-focusing, saturable absorber (SA) device. The SA device consists of two tapered fiber ends separated by a bulk, nonlinear medium. An optical beam transmitted from one tapered fiber end, propagate through the nonlinear medium (chalcogenide glass As40 S e60) and couples back into the other tapered fiber end. Pulse propagation in the fiber laser cavity is performed using the Split Step Method. Stable pulses are generated with energies around 0.3 nJ and a transform limited pulse width around 200 fs.

  13. Models for the optical simulations of fractal aggregated soot particles thinly coated with non-absorbing aerosols

    NASA Astrophysics Data System (ADS)

    Wu, Yu; Cheng, Tianhai; Zheng, Lijuan; Chen, Hao

    2016-10-01

    Light absorption enhancement of aged soot aerosols is highly sensitive to the morphologies and mixing states of soot aggregates and their non-absorbing coatings, such as organic materials. The quantification of these effects on the optical properties of thinly coated soot aerosols is simulated using an effective model with fixed volume fractions. Fractal aggregated soot was simulated using the diffusion limited aggregation (DLA) algorithm and discretized into soot dipoles. The dipoles of non-absorbing aerosols, whose number was fixed by the volume fraction, were further generated from the neighboring random edge dipoles. Their optical properties were calculated using the discrete dipole approximation (DDA) method and were compared with other commonly used models. The optical properties of thinly coated soot calculated using the fixed volume fraction model are close to (less than ~10% difference) the results of the fixed coating thickness model, except their asymmetry parameters (up to ~25% difference). In the optical simulations of thinly coated soot aerosols, this relative difference of asymmetry parameters and phase functions between these realistic models may be notable. The realizations of the fixed volume fraction model may introduce smaller variation of optical results than those of the fixed coating thickness model. Moreover, the core-shell monomers model and homogeneous aggregated spheres model with the Maxwell-Garnett (MG) theory may underestimate (up to ~20%) the cross sections of thinly coated soot aggregates. The single core-shell sphere model may largely overestimate (up to ~150%) the cross sections and single scattering albedo of thinly coated soot aggregates, and it underestimated (up to ~60%) their asymmetry parameters. It is suggested that the widely used single core-shell sphere approximation may not be suitable for the single scattering calculations of thinly coated soot aerosols.

  14. Design and model of wideband absorber made of ultrathin metamaterial structures

    NASA Astrophysics Data System (ADS)

    Sellier, Alexandre; Teperik, Tatiana V.; Burokur, Shah Nawaz; Sabanowski, Guy; Piau, Gérard-Pascal; de Lustrac, André

    2014-08-01

    A planar microwave ultrathin broadband absorber is proposed. It is composed of metallic patterns arranged on a dielectric material which is backed by a copper plate. The patterns of different dimensions allow to judiciously design absorption peaks at specific frequencies of interest. These peaks are due to the mode resonances of the cavities formed by the metallic patches, the dielectric substrate and the copper plate. In order to widen the absorption bandwidth, patterns of different dimensions are used, together with the different modes of these cavities. Numerical and experimental results are presented to validate the proposed method at microwave frequencies. It is also shown that the use of a composite air dielectric substrate supporting the metallic patterns helps to increase the absorption level.

  15. Transient multi-physics analysis of a magnetorheological shock absorber with the inverse Jiles-Atherton hysteresis model

    NASA Astrophysics Data System (ADS)

    Zheng, Jiajia; Li, Yancheng; Li, Zhaochun; Wang, Jiong

    2015-10-01

    This paper presents multi-physics modeling of an MR absorber considering the magnetic hysteresis to capture the nonlinear relationship between the applied current and the generated force under impact loading. The magnetic field, temperature field, and fluid dynamics are represented by the Maxwell equations, conjugate heat transfer equations, and Navier-Stokes equations. These fields are coupled through the apparent viscosity and the magnetic force, both of which in turn depend on the magnetic flux density and the temperature. Based on a parametric study, an inverse Jiles-Atherton hysteresis model is used and implemented for the magnetic field simulation. The temperature rise of the MR fluid in the annular gap caused by core loss (i.e. eddy current loss and hysteresis loss) and fluid motion is computed to investigate the current-force behavior. A group of impulsive tests was performed for the manufactured MR absorber with step exciting currents. The numerical and experimental results showed good agreement, which validates the effectiveness of the proposed multi-physics FEA model.

  16. Constraining the Redshift Evolution of the Cosmic Microwave Background Blackbody Temperature with PLANCK Data.

    NASA Astrophysics Data System (ADS)

    de Martino, I.; Génova-Santos, R.; Atrio-Barandela, F.; Ebeling, H.; Kashlinsky, A.; Kocevski, D.; Martins, C. J. A. P.

    2015-08-01

    We constrain the deviation of adiabatic evolution of the universe using the data on the cosmic microwave background (CMB) temperature anisotropies measured by the Planck satellite and a sample of 481 X-ray selected clusters with spectroscopically measured redshifts. To avoid antenna beam effects, we bring all of the maps to the same resolution. We use a CMB template to subtract the cosmological signal while preserving the Thermal Sunyaev-Zeldovich (TSZ) anisotropies; next, we remove galactic foreground emissions around each cluster and we mask out all known point sources. If the CMB blackbody temperature scales with redshift as T{(z)={T}0(1+z)}1-α , we constrain deviations of adiabatic evolution to be α = -0.007 ± 0.013, consistent with the temperature-redshift relation of the standard cosmological model. This result could suffer from a potential bias δα associated with the CMB template. We quantify it to be | δ α | ≤slant 0.02, with the same sign as the measured value of α. Our result is free from those biases associated with using TSZ selected clusters; it represents the best constraint to date of the temperature-redshift relation of the Big Bang model using only CMB data, confirming previous results.

  17. Sensitivity of blackbody effective emissivity to wavelength and temperature: By genetic algorithm

    SciTech Connect

    Ejigu, E. K.; Liedberg, H. G.

    2013-09-11

    A variable-temperature blackbody (VTBB) is used to calibrate an infrared radiation thermometer (pyrometer). The effective emissivity (ε{sub eff}) of a VTBB is dependent on temperature and wavelength other than the geometry of the VTBB. In the calibration process the effective emissivity is often assumed to be constant within the wavelength and temperature range. There are practical situations where the sensitivity of the effective emissivity needs to be known and correction has to be applied. We present a method using a genetic algorithm to investigate the sensitivity of the effective emissivity to wavelength and temperature variation. Two matlab® programs are generated: the first to model the radiance temperature calculation and the second to connect the model to the genetic algorithm optimization toolbox. The effective emissivity parameter is taken as a chromosome and optimized at each wavelength and temperature point. The difference between the contact temperature (reading from a platinum resistance thermometer or liquid in glass thermometer) and radiance temperature (calculated from the ε{sub eff} values) is used as an objective function where merit values are calculated and best fit ε{sub eff} values selected. The best fit ε{sub eff} values obtained as a solution show how sensitive they are to temperature and wavelength parameter variation. Uncertainty components that arise from wavelength and temperature variation are determined based on the sensitivity analysis. Numerical examples are considered for illustration.

  18. Specification of absorbed dose to water using model-based dose calculation algorithms for treatment planning in brachytherapy

    NASA Astrophysics Data System (ADS)

    Carlsson Tedgren, Åsa; Alm Carlsson, Gudrun

    2013-04-01

    Model-based dose calculation algorithms (MBDCAs), recently introduced in treatment planning systems (TPS) for brachytherapy, calculate tissue absorbed doses. In the TPS framework, doses have hereto been reported as dose to water and water may still be preferred as a dose specification medium. Dose to tissue medium Dmed then needs to be converted into dose to water in tissue Dw,med. Methods to calculate absorbed dose to differently sized water compartments/cavities inside tissue, infinitesimal (used for definition of absorbed dose), small, large or intermediate, are reviewed. Burlin theory is applied to estimate photon energies at which cavity sizes in the range 1 nm-10 mm can be considered small or large. Photon and electron energy spectra are calculated at 1 cm distance from the central axis in cylindrical phantoms of bone, muscle and adipose tissue for 20, 50, 300 keV photons and photons from 125I, 169Yb and 192Ir sources; ratios of mass-collision-stopping powers and mass energy absorption coefficients are calculated as applicable to convert Dmed into Dw,med for small and large cavities. Results show that 1-10 nm sized cavities are small at all investigated photon energies; 100 µm cavities are large only at photon energies <20 keV. A choice of an appropriate conversion coefficient Dw, med/Dmed is discussed in terms of the cavity size in relation to the size of important cellular targets. Free radicals from DNA bound water of nanometre dimensions contribute to DNA damage and cell killing and may be the most important water compartment in cells implying use of ratios of mass-collision-stopping powers for converting Dmed into Dw,med.

  19. Specification of absorbed dose to water using model-based dose calculation algorithms for treatment planning in brachytherapy.

    PubMed

    Tedgren, Åsa Carlsson; Carlsson, Gudrun Alm

    2013-04-21

    Model-based dose calculation algorithms (MBDCAs), recently introduced in treatment planning systems (TPS) for brachytherapy, calculate tissue absorbed doses. In the TPS framework, doses have hereto been reported as dose to water and water may still be preferred as a dose specification medium. Dose to tissue medium Dmed then needs to be converted into dose to water in tissue Dw,med. Methods to calculate absorbed dose to differently sized water compartments/cavities inside tissue, infinitesimal (used for definition of absorbed dose), small, large or intermediate, are reviewed. Burlin theory is applied to estimate photon energies at which cavity sizes in the range 1 nm-10 mm can be considered small or large. Photon and electron energy spectra are calculated at 1 cm distance from the central axis in cylindrical phantoms of bone, muscle and adipose tissue for 20, 50, 300 keV photons and photons from (125)I, (169)Yb and (192)Ir sources; ratios of mass-collision-stopping powers and mass energy absorption coefficients are calculated as applicable to convert Dmed into Dw,med for small and large cavities. Results show that 1-10 nm sized cavities are small at all investigated photon energies; 100 µm cavities are large only at photon energies <20 keV. A choice of an appropriate conversion coefficient Dw, med/Dmed is discussed in terms of the cavity size in relation to the size of important cellular targets. Free radicals from DNA bound water of nanometre dimensions contribute to DNA damage and cell killing and may be the most important water compartment in cells implying use of ratios of mass-collision-stopping powers for converting Dmed into Dw,med.

  20. -30° C to 960° C Variable Temperature Blackbody (VTBB) Radiance Temperature Calibration Facility

    NASA Astrophysics Data System (ADS)

    Yuan, Z.; Wang, J.; Hao, X.; Wang, T.; Dong, W.

    2015-12-01

    A blackbody radiance temperature calibration facility (RTCF) has recently been established at the National Institute of Metrology, China, offering calibration and verification services for variable temperature blackbody (VTBB) radiation sources. The RTCF includes reference VTBBs in the range of -30° C to 960° C and consists of a stirred liquid bath blackbody of -30° C to 80° C and water, cesium, and sodium heat-pipe blackbodies spanning 50° C to 960° C. In addition, the facility is equipped with a set of radiation thermometers with different working wavelengths (or wavebands); these thermometers are used to transfer radiance temperatures from the reference to customers' VTBBs. Cavities with V-notch grooves in the inner surface have an estimated emissivity from 0.99986 to 0.99994. The temperature control stability and temperature uniformity of VTBBs are characterized. Furthermore, we test the difference between a cavity and thermometer well temperatures and compare the radiance temperatures of the Cs and Na heat-pipe blackbodies. The expanded uncertainty (k = 2) of VTBBs' radiance temperatures at 10 \\upmu m (8 \\upmu m to 14 \\upmu m) is evaluated from 0.016° C to 0.23° C. The facility has been used to calibrate and characterize customers' VTBBs.

  1. Blackbody-mediated rotational laser cooling schemes in MgH+, DCl+, HCl+, LiH and CsH.

    PubMed

    Deb, Nabanita; Heazlewood, Brianna R; Bell, Martin T; Softley, Timothy P

    2013-09-14

    Ensembles of ultra-cold atoms, molecules and ions (both atomic and molecular) can be held in traps for increasingly long periods of time. While these trapped species remain translationally cold, for molecules the absorption of ambient black-body radiation can result in rapid thermalisation of the rotational (and vibrational) degrees of freedom. At 300 K, internal state purity is lost typically on the order of tens of seconds, inhibiting the study of quantum state selected reactions. In this paper a theoretical model is used to investigate laser-driven, blackbody-mediated, rotational cooling schemes for several (1)Σ and (2)Π diatomic species. The rotational cooling is particularly effective for DCl(+) and HCl(+), for which 92% and >99% (respectively) of the population can be driven into the rovibrational ground state. For the other systems a broadband optical pumping source (simultaneously exciting up to four transitions) is found to enhance the population that can be accumulated in the rovibrational ground state by up to 29% over that achieved when exciting a single transition. The influence of the rotational constant, dipole moments and electronic state of the diatomics on the rotational cooling achievable is also considered. An extension to polyatomic species is discussed and a combination of cold trap environments (at 77 K) and optical pumping schemes is proposed.

  2. Terahertz magneto-optic generalized ellipsometry using synchrotron and blackbody radiation

    NASA Astrophysics Data System (ADS)

    Hofmann, T.; Schade, U.; Herzinger, C. M.; Esquinazi, P.; Schubert, M.

    2006-06-01

    We report on the first setup and experimental verification of terahertz frequency domain magneto-optic generalized ellipsometry using a combination of highly brilliant terahertz synchrotron and conventional blackbody radiation sources. The polarizer-sample-rotating-analyzer ellipsometry principle is employed to measure the three normalized Stokes vector elements excluding depolarization information, and the upper left 3×3 block of the normalized 4×4 Mueller matrix accordingly for wave numbers from 30to650cm-1 (0.9-20THz). We discuss setup, measurement, and data analysis procedures specific to the use of synchrotron radiation for terahertz ellipsometry. Two sample systems with different free-charge-carrier properties were studied and are presented here to illustrate terahertz ellipsometry and data analysis. The first example is low-chlorine-doped ZnMnSe, a dilute magnetic semiconductor. Analysis of the normalized Mueller matrix elements using the Drude magneto-optic dielectric function tensor model over the entire spectral range from 30to650cm-1 allowed the independent determination of the free-charge-carrier properties effective mass, concentration, and mobility. We further present and discuss Mueller matrix spectra obtained from highly oriented pyrolytic graphite at low temperatures. The spectra of this second example, a two-dimensionally confined charge carrier system, reveal distinct fingerprints of chiral electronic transitions between Landau levels.

  3. Mathematical models and specific absorbed fractions of photon energy in the nonpregnant adult female and at the end of each trimester of pregnancy

    SciTech Connect

    Stabin, M.G.; Watson, E.E.; Cristy, M.; Ryman, J.C.; Eckerman, K.F.; Davis, J.L.; Marshall, D.; Gehlen, M.K.

    1995-05-08

    Mathematical phantoms representing the adult female at three, six, and nine months of gestation are described. They are modifications of the 15-year-old male/adult female phantom (15-AF phantom) of Cristy and Eckerman (1987). The model of uterine contents includes the fetus, fetal skeleton, and placenta. The model is suitable for dose calculations for the fetus as a whole; individual organs within the fetus (other than the skeleton) are not modeled. A new model for the nonpregnant adult female is also described, comprising (1) the 15-AF phantom; (2) an adjustment to specific absorbed fractions for organ self-dose from photons to better match Reference Woman masses; and (3) computation of specific absorbed fractions with Reference Woman masses from ICRP Publication 23 for both penetrating and nonpenetrating radiations. Specific absorbed fractions for photons emitted from various source regions are tabulated for the new non;pregnant adult female model and the three pregnancy models.

  4. An Oil-Bath-Based 293 K to 473 K Blackbody Source

    PubMed Central

    Fowler, Joel B.

    1996-01-01

    A high temperature oil-bath-based-black-body source has been designed and constructed in the Radiometric Physics Division at the National Institute of Standards and Technology, Gaithersburg, MD. The goal of this work was to design a large aperture blackbody source with highly uniform radiance across the aperture, good temporal stability, and good reproducibility. This blackbody source operates in the 293 K to 473 K range with blackbody temperature combined standard uncertainties of 7.2 mK to 30.9 mK. The calculated emissivity of this source is 0.9997 with a standard uncertainty of 0.0003. With a 50 mm limiting aperture at the cavity entrance, the emissivity increases to 0.99996. PMID:27805082

  5. Understanding the Planck blackbody spectrum and Landau diamagnetism within classical electromagnetism

    NASA Astrophysics Data System (ADS)

    Boyer, Timothy H.

    2016-11-01

    Electromagnetism is a relativistic theory, and one must exercise care in coupling this theory with nonrelativistic classical mechanics and with nonrelativistic classical statistical mechanics. Indeed historically, both the blackbody radiation spectrum and diamagnetism within classical theory have been misunderstood because of two crucial failures: (1) the neglect of classical electromagnetic zero-point radiation, and (2) the use of erroneous combinations of nonrelativistic mechanics with relativistic electrodynamics. Here we review the treatment of classical blackbody radiation, and show that the presence of Lorentz-invariant classical electromagnetic zero-point radiation can explain both the Planck blackbody spectrum and Landau diamagnetism at thermal equilibrium within classical electromagnetic theory. The analysis requires that relativistic electromagnetism is joined appropriately with simple nonrelativistic mechanical systems which can be regarded as the zero-velocity limits of relativistic systems, and that nonrelativistic classical statistical mechanics is applied only in the low-frequency limit when zero-point energy makes no contribution.

  6. Enhancement of blackbody friction due to the finite lifetime of atomic levels.

    PubMed

    Łach, G; DeKieviet, M; Jentschura, U D

    2012-01-27

    The thermal friction force acting on an atom moving relative to a thermal photon bath is known to be proportional to an integral over the imaginary part of the frequency-dependent atomic (dipole) polarizability. Using a numerical approach, we find that blackbody friction on atoms either in dilute environments or in hot ovens is larger than previously thought by orders of magnitude. This enhancement is due to far off-resonant driving of transitions by low-frequency thermal radiation. At typical temperatures, the blackbody radiation maximum lies far below the atomic transition wavelengths. Surprisingly, due to the finite lifetime of atomic levels, which gives rise to Lorentzian line profiles, far off-resonant excitation leads to the dominant contribution for blackbody friction.

  7. Rydberg Spectroscopy in an Optical Lattice: Blackbody Thermometry for Atomic Clocks

    SciTech Connect

    Ovsiannikov, Vitali D.; Derevianko, Andrei; Gibble, Kurt

    2011-08-26

    We show that optical spectroscopy of Rydberg states can provide accurate in situ thermometry at room temperature. Transitions from a metastable state to Rydberg states with principal quantum numbers of 25-30 have 200 times larger fractional frequency sensitivities to blackbody radiation than the strontium clock transition. We demonstrate that magic-wavelength lattices exist for both strontium and ytterbium transitions between the metastable and Rydberg states. Frequency measurements of Rydberg transitions with 10{sup -16} accuracy provide 10 mK resolution and yield a blackbody uncertainty for the clock transition of 10{sup -18}.

  8. Rydberg spectroscopy in an optical lattice: blackbody thermometry for atomic clocks.

    PubMed

    Ovsiannikov, Vitali D; Derevianko, Andrei; Gibble, Kurt

    2011-08-26

    We show that optical spectroscopy of Rydberg states can provide accurate in situ thermometry at room temperature. Transitions from a metastable state to Rydberg states with principal quantum numbers of 25-30 have 200 times larger fractional frequency sensitivities to blackbody radiation than the strontium clock transition. We demonstrate that magic-wavelength lattices exist for both strontium and ytterbium transitions between the metastable and Rydberg states. Frequency measurements of Rydberg transitions with 10(-16) accuracy provide 10 mK resolution and yield a blackbody uncertainty for the clock transition of 10(-18).

  9. Theoretical model of homogeneous metal-insulator-metal perfect multi-band absorbers for the visible spectrum

    NASA Astrophysics Data System (ADS)

    Kajtár, G.; Kafesaki, M.; Economou, E. N.; Soukoulis, C. M.

    2016-02-01

    We present a rigorous study of the perfect absorption properties of metal-insulator-metal (MIM) structures in the visible spectrum. We provide a derivation (based on the transfer matrix method) and analysis of the conditions for which the perfect absorption occurs. We show that these conditions are fulfilled when the incident wave excites the eigenmodes of the structure. The quantitative analysis allows us to design specific perfect absorbers for our needs. The analytical model is verified by rigorous simulations based on rigorous coupled wave analysis, which demonstrate also the angle and polarization insensitivity of the absorption properties of such a structure. Employing the MIM approach and results, we also investigate and demonstrate multiple perfect absorption bands and broad-band absorption in properly designed multilayer metal-insulator systems.

  10. Analysis of the blackbody-radiation shift in an ytterbium optical lattice clock

    NASA Astrophysics Data System (ADS)

    Xu, Yi-Lin; Xu, Xin-Ye

    2016-10-01

    We accurately evaluate the blackbody-radiation shift in a 171Yb optical lattice clock by utilizing temperature measurement and numerical simulation. In this work. three main radiation sources are considered for the blackbody-radiation shift, including the heated atomic oven, the warm vacuum chamber, and the room-temperature vacuum windows. The temperatures on the outer surface of the vacuum chamber are measured during the clock operation period by utilizing seven calibrated temperature sensors. Then we infer the temperature distribution inside the vacuum chamber by numerical simulation according to the measured temperatures. Furthermore, we simulate the temperature variation around the cold atoms while the environmental temperature is fluctuating. Finally, we obtain that the total blackbody-radiation shift is -1.289(7) Hz with an uncertainty of 1.25 × 10-17 for our 171Yb optical lattice clock. The presented method is quite suitable for accurately evaluating the blackbody-radiation shift of the optical lattice clock in the case of lacking the sensors inside the vacuum chamber. Project supported by the National Key Basic Research and Development Program of China (Grant No. 2012CB821302), the National Natural Science Foundation of China (Grant No. 11134003), the National High Technology Research and Development Program of China (Grant No. 2014AA123401), and the Shanghai Excellent Academic Leaders Program of China (Grant No. 12XD1402400).

  11. The relativistic blackbody spectrum in inertial and non-inertial reference frames

    NASA Astrophysics Data System (ADS)

    Lee, Jeffrey S.; Cleaver, Gerald B.

    2017-04-01

    By invoking inverse temperature as a van Kampen-Israel future-directed timelike 4-vector, this paper derives the Relativistic Blackbody Spectrum, the Relativistic Wien's Displacement Law, and the Relativistic Stefan-Boltzmann Law in inertial and non-inertial reference frames.

  12. Modelling of zircaloy dissolution by molten (Ag, In, Cd) absorber alloy

    NASA Astrophysics Data System (ADS)

    Veshchunov, M. S.; Hofmann, P.

    1996-04-01

    Solid Zircaloy (Zry) is dissolved by molten (Ag, In, Cd) alloy at high temperatures. Results of detailed chemical-analytical examinations (integral and point analysis) of (Ag, In, Cd)/Zry reaction couples annealed at temperatures of 1100, 1150 and 1200°C in crucible tests demonstrate a homogeneous composition of the resulting liquid phase and prove that strong convective mixing of the liquid takes place in the course of the interactions. The theoretical model developed on the basis of the measured data explains the reasons for the observed convective mixing of the liquid phase and describes the kinetics of the (Ag, In, Cd)/Zry interactions leading to the saturation of the liquid phase with Zr. Two main parameters of the model are calculated: Zr concentration in the saturated melt and convective mass transfer coefficient in the liquid phase. The influence of an oxide layer on the (Ag, In, Cd)/Zry interactions is additionally studied and described by the developed model.

  13. The development of early pediatric models and their application to radiation absorbed dose calculations

    SciTech Connect

    Poston, J.W.

    1989-01-01

    This presentation will review and describe the development of pediatric phantoms for use in radiation dose calculations . The development of pediatric models for dose calculations essentially paralleled that of the adult. In fact, Snyder and Fisher at the Oak Ridge National Laboratory reported on a series of phantoms for such calculations in 1966 about two years before the first MIRD publication on the adult human phantom. These phantoms, for a newborn, one-, five-, ten-, and fifteen-year old, were derived from the adult phantom. The pediatric'' models were obtained through a series of transformations applied to the major dimensions of the adult, which were specified in a Cartesian coordinate system. These phantoms suffered from the fact that no real consideration was given to the influence of these mathematical transformations on the actual organ sizes in the other models nor to the relation of the resulting organ masses to those in humans of the particular age. Later, an extensive effort was invested in designing individual'' pediatric phantoms for each age based upon a careful review of the literature. Unfortunately, the phantoms had limited use and only a small number of calculations were made available to the user community. Examples of the phantoms, their typical dimensions, common weaknesses, etc. will be discussed.

  14. The development of early pediatric models and their application to radiation absorbed dose calculations

    SciTech Connect

    Poston, J.W.

    1989-12-31

    This presentation will review and describe the development of pediatric phantoms for use in radiation dose calculations . The development of pediatric models for dose calculations essentially paralleled that of the adult. In fact, Snyder and Fisher at the Oak Ridge National Laboratory reported on a series of phantoms for such calculations in 1966 about two years before the first MIRD publication on the adult human phantom. These phantoms, for a newborn, one-, five-, ten-, and fifteen-year old, were derived from the adult phantom. The ``pediatric`` models were obtained through a series of transformations applied to the major dimensions of the adult, which were specified in a Cartesian coordinate system. These phantoms suffered from the fact that no real consideration was given to the influence of these mathematical transformations on the actual organ sizes in the other models nor to the relation of the resulting organ masses to those in humans of the particular age. Later, an extensive effort was invested in designing ``individual`` pediatric phantoms for each age based upon a careful review of the literature. Unfortunately, the phantoms had limited use and only a small number of calculations were made available to the user community. Examples of the phantoms, their typical dimensions, common weaknesses, etc. will be discussed.

  15. Hydrocarbon pyrolysis reactor experimentation and modeling for the production of solar absorbing carbon nanoparticles

    NASA Astrophysics Data System (ADS)

    Frederickson, Lee Thomas

    Much of combustion research focuses on reducing soot particulates in emissions. However, current research at San Diego State University (SDSU) Combustion and Solar Energy Laboratory (CSEL) is underway to develop a high temperature solar receiver which will utilize carbon nanoparticles as a solar absorption medium. To produce carbon nanoparticles for the small particle heat exchange receiver (SPHER), a lab-scale carbon particle generator (CPG) has been built and tested. The CPG is a heated ceramic tube reactor with a set point wall temperature of 1100-1300°C operating at 5-6 bar pressure. Natural gas and nitrogen are fed to the CPG where natural gas undergoes pyrolysis resulting in carbon particles. The gas-particle mixture is met downstream with dilution air and sent to the lab scale solar receiver. To predict soot yield and general trends in CPG performance, a model has been setup in Reaction Design CHEMKIN-PRO software. One of the primary goals of this research is to accurately measure particle properties. Mean particle diameter, size distribution, and index of refraction are calculated using Scanning Electron Microscopy (SEM) and a Diesel Particulate Scatterometer (DPS). Filter samples taken during experimentation are analyzed to obtain a particle size distribution with SEM images processed in ImageJ software. These results are compared with the DPS, which calculates the particle size distribution and the index of refraction from light scattering using Mie theory. For testing with the lab scale receiver, a particle diameter range of 200-500 nm is desired. Test conditions are varied to understand effects of operating parameters on particle size and the ability to obtain the size range. Analysis of particle loading is the other important metric for this research. Particle loading is measured downstream of the CPG outlet and dilution air mixing point. The air-particle mixture flows through an extinction tube where opacity of the mixture is measured with a 532 nm

  16. Experimental Wave Tank Test for Reference Model 3 Floating-Point Absorber Wave Energy Converter Project

    SciTech Connect

    Yu, Y. H.; Lawson, M.; Li, Y.; Previsic, M.; Epler, J.; Lou, J.

    2015-01-01

    The U.S. Department of Energy established a reference model project to benchmark a set of marine and hydrokinetic technologies including current (tidal, open-ocean, and river) turbines and wave energy converters. The objectives of the project were to first evaluate the status of these technologies and their readiness for commercial applications. Second, to evaluate the potential cost of energy and identify cost-reduction pathways and areas where additional research could be best applied to accelerate technology development to market readiness.

  17. Direct measurements and modeling of gradient-aligned cross-field ion flows near an absorbing boundary

    NASA Astrophysics Data System (ADS)

    Thompson, D. S.; Siddiqui, M. Umair; McIlvain, J. S.; Short, Z. D.; Scime, E. E.; Aguirre, E. M.; Henriquez, M. F.; McKee, J. S.

    2015-11-01

    Direct measurements of cross-field ion transport near boundaries are sought for validating transport models in magnetically confined plasmas. Using laser-induced fluorescence, we measured ion flows normal to an absorbing boundary that was aligned to be parallel to a uniform axial magnetic field in a helicon plasma. We used Langmuir and emissive probes to measure local density, temperature and plasma potential profiles in the same region. We then scanned ion-neutral collisionality by varying the ratio of the ion gyro-radius, ρi, and ion-neutral collision length, λ, over the range 0.34 <=ρi / λ <= 1.60. Classical diffusion along density and potential gradients is sufficient to describe flow profiles for most cases but did not describe measurements well for 0.44 <=ρi / λ <= 0.65. In these cases, cross-sections ~3 times the classical prediction produced acceptable fits, and flow to the boundary was enhanced significantly. These enhanced flow cases exhibit spectra with low-frequency electrostatic fluctuations (f <10 kHz) that are not observed in data described well by a classical diffusion model. This work is supported by US National Science Foundation grant number PHY-1360278.

  18. Ionized Absorbers in AGN

    NASA Technical Reports Server (NTRS)

    Mathur, S.

    1999-01-01

    As a part of this program, we observed three AGN:PKS2251 + 113, PG0043 = 039 and PLH909. Two objects show signatures of absorbtion in their UV spectra. Based on our earlier modeling of X-ray warm absorbents, we expected to observe X-ray observation in these objects. The third, PLH909, is known to have soft excess in EINSTEIN data. Attachment: "Exploratory ASCA observation of broad absorption line quasi-stellar objects".

  19. Numerical simulation of optical Stark effect saturable absorbers in mode-locked femtosecond VECSELs using a modified two-level atom model.

    PubMed

    Quarterman, A H; Carswell, S; Daniell, G J; Mihoubi, Z; Wilcox, K G; Chung, A L; Apostolopoulos, V; Tropper, A C

    2011-12-19

    The interaction of an optical pulse with a quantum well saturable absorber is simulated using a semi-classical two-level-atom model which has been modified to approximate spectral hole burning in the carrier distribution. Saturable absorption behaviour is examined in the limit where pulse duration approaches the carrier-carrier scattering time. For long pulses bleaching dominates the absorber response but as the pulse duration approaches the carrier-carrier scattering timescale an additional pulse shaping mechanism becomes active, allowing the absorber to continue to shorten pulses beyond the limit set by bleaching. Examination of the spectral and temporal absorption profiles suggests that intense pulses experience additional pulse shortening from the optical Stark effect.

  20. A detailed analysis of the high-resolution X-ray spectra of NGC 3516: variability of the ionized absorbers

    SciTech Connect

    Huerta, E. M.; Krongold, Y.; Jimenez-Bailon, E.; Nicastro, F.; Mathur, S.; Longinotti, A. L.

    2014-09-20

    The 1.5 Seyfert galaxy NGC 3516 presents a strong time variability in X-rays. We re-analyzed the nine observations performed in 2006 October by XMM-Newton and Chandra in the 0.3 to 10 keV energy band. An acceptable model was found for the XMM-Newton data fitting the EPIC-PN and RGS spectra simultaneously; later, this model was successfully applied to the contemporary Chandra high-resolution data. The model consists of a continuum emission component (power law + blackbody) absorbed by four ionized components (warm absorbers), and 10 narrow emission lines. Three absorbing components are warm, producing features only in the soft X-ray band. The fourth ionization component produces Fe XXV and Fe XXVI in the hard-energy band. We study the time response of the absorbing components to the well-detected changes in the X-ray luminosity of this source and find that the two components with the lower ionization state show clear opacity changes consistent with gas close to photoionization equilibrium. These changes are supported by the models and by differences in the spectral features among the nine observations. On the other hand, the two components with higher ionization state do not seem to respond to continuum variations. The response time of the ionized absorbers allows us to constrain their electron density and location. We find that one component (with intermediate ionization) must be located within the obscuring torus at a distance 2.7 × 10{sup 17} cm from the central engine. This outflowing component likely originated in the accretion disk. The three remaining components are at distances larger than 10{sup 16}-10{sup 17} cm. Two of the absorbing components in the soft X-rays have similar outflow velocities and locations. These components may be in pressure equilibrium, forming a multi-phase medium, if the gas has metallicity larger than the solar one (≳ 5 Z {sub ☉}). We also search for variations in the covering factor of the ionized absorbers (although partial

  1. Nano-imaging in the black-body infrared near-field.

    NASA Astrophysics Data System (ADS)

    Jones, Andrew C.; Raschke, Markus B.

    2010-03-01

    In order to probe material properties on the nanoscale, Scanning Near-field Optical Microscopy (SNOM) traditionally relies on the use of external far-field light sources. Recent experiments have demonstrated the alternative use of the evanescent thermal black-body radiation in scattering-SNOM [1]. Here, we explore the use of both heated samples and heated probe tips for scattering type SNOM in combination with Fourier transform infrared spectroscopy (FTIR) of the scattered thermal blackbody near-field radiation of IR nano-antennas and surface phonon excitations. We relate the observed and theoretically expected signal strength with the resonantly enhanced electromagnetic near-field density of states. Our result illustrates the potential as well as the limitations of the use of thermal evanescent fields for nano-imaging. [1] De Wilde, Y. et al. Nature. 444:740-743 (2006)

  2. Ytterbium in quantum gases and atomic clocks: van der Waals interactions and blackbody shifts.

    PubMed

    Safronova, M S; Porsev, S G; Clark, Charles W

    2012-12-07

    We evaluated the C(6) coefficients of Yb-Yb, Yb-alkali, and Yb-group II van der Waals interactions with 2% uncertainty. The only existing experimental result for such quantities is for the Yb-Yb dimer. Our value, C(6)=1929(39) a.u., is in excellent agreement with the recent experimental determination of 1932(35) a.u. We have also developed a new approach for the calculation of the dynamic correction to the blackbody radiation shift. We have calculated this quantity for the Yb 6s(2) (1)S(0)-6s6p (3)P(0)(o) clock transition with 3.5% uncertainty. This reduces the fractional uncertainty due to the blackbody radiation shift in the Yb optical clock at 300 K to the 10(-18) level.

  3. The role of the equivalent blackbody temperature in the study of Atlantic Ocean tropical cyclones

    NASA Technical Reports Server (NTRS)

    Steranka, J.; Rodgers, E. B.; Gentry, R. C.

    1983-01-01

    Satellite measured equivalent blackbody temperatures of Atlantic Ocean tropical cyclones are used to investigate their role in describing the convection and cloud patterns of the storms and in predicting wind intensity. The high temporal resolution of the equivalent blackbody temperature measurements afforded with the geosynchronous satellite provided sequential quantitative measurements of the tropical cyclone which reveal a diurnal pattern of convection at the inner core during the early developmental stage; a diurnal pattern of cloudiness in the storm's outer circulation throughout the life cycle; a semidiurnal pattern of cloudiness in the environmental atmosphere surrounding the storms during the weak storm stage; an outward modulating atmospheric wave originating at the inner core; and long term convective bursts at the inner core prior to wind intensification.

  4. Comparing the influence of distinct kinds of temporal disorder in a low-dimensional absorbing transition model

    NASA Astrophysics Data System (ADS)

    Solano, C. M. D.; de Oliveira, M. M.; Fiore, C. E.

    2016-10-01

    Recently it was stated that temporal disorder constitutes a relevant perturbation in absorbing phase transitions for all dimensions. However, its effect on systems other than the standard contact process (CP), its competition with other ingredients (e.g., particle diffusion), and other kinds of disorder (besides the standard types) are unknown. In order to shed some light on the above-mentioned points, we investigate a variant of the usual CP, namely, the triplet annihilation model, in which the competition between triplet annihilation and single particle diffusion leads to an unusual phase diagram behavior, with reentrant shape and endless activity for sufficiently large diffusion rates. Two kinds of time-dependent disorder have been considered. In the former, it is introduced in the creation-annihilation parameters (as commonly considered in recent studies), whereas in the latter, the diffusion rate D is allowed to be time dependent. In all cases, the disorder follows a uniform distribution with fixed mean and width σ . Two values of σ have been considered in order to exemplify the regime of "weaker" and "stronger" temporal disorder strengths. Our results show that in the former approach, the disorder suppresses the reentrant phase diagram with a critical behavior deviating from the directed percolation (DP) universality class in the regime of low diffusion rates, while they strongly suggest that the DP class is recovered for larger hopping rates. An opposite scenario is found in the latter disorder approach, with a substantial increase of reentrant shape and the maximum diffusion, in which the reentrant shape also displays a critical behavior consistent with the DP universality class (in similarity with the pure model). In order to compare with very recent claims, the results from taking a bimodal distribution and critical behavior in the limit of strong disorder are presented. Also, the results derived from the mean-field theory are performed, presenting

  5. Comparing the influence of distinct kinds of temporal disorder in a low-dimensional absorbing transition model.

    PubMed

    Solano, C M D; de Oliveira, M M; Fiore, C E

    2016-10-01

    Recently it was stated that temporal disorder constitutes a relevant perturbation in absorbing phase transitions for all dimensions. However, its effect on systems other than the standard contact process (CP), its competition with other ingredients (e.g., particle diffusion), and other kinds of disorder (besides the standard types) are unknown. In order to shed some light on the above-mentioned points, we investigate a variant of the usual CP, namely, the triplet annihilation model, in which the competition between triplet annihilation and single particle diffusion leads to an unusual phase diagram behavior, with reentrant shape and endless activity for sufficiently large diffusion rates. Two kinds of time-dependent disorder have been considered. In the former, it is introduced in the creation-annihilation parameters (as commonly considered in recent studies), whereas in the latter, the diffusion rate D is allowed to be time dependent. In all cases, the disorder follows a uniform distribution with fixed mean and width σ. Two values of σ have been considered in order to exemplify the regime of "weaker" and "stronger" temporal disorder strengths. Our results show that in the former approach, the disorder suppresses the reentrant phase diagram with a critical behavior deviating from the directed percolation (DP) universality class in the regime of low diffusion rates, while they strongly suggest that the DP class is recovered for larger hopping rates. An opposite scenario is found in the latter disorder approach, with a substantial increase of reentrant shape and the maximum diffusion, in which the reentrant shape also displays a critical behavior consistent with the DP universality class (in similarity with the pure model). In order to compare with very recent claims, the results from taking a bimodal distribution and critical behavior in the limit of strong disorder are presented. Also, the results derived from the mean-field theory are performed, presenting

  6. Laser-induced two-photon blackbody radiation in the vacuum ultraviolet

    NASA Technical Reports Server (NTRS)

    Zych, L. J.; Young, J. F.; Harris, S. E.; Lukasik, J.

    1978-01-01

    Experimental measurements of a new type of vacuum-ultraviolet radiation source are reported. It is shown that the maximum source brightness, within its narrow linewidth, is that of a blackbody at the temperature of a metastable storage level. The laser-induced emission at 569 A from a He glow discharge corresponded to a metastable temperature of 22,700 K and was over 100 times brighter than the 584-A He resonance line.

  7. Absorbing aerosols over Asia: A Geophysical Fluid Dynamics Laboratory general circulation model sensitivity study of model response to aerosol optical depth and aerosol absorption

    NASA Astrophysics Data System (ADS)

    Randles, C. A.; Ramaswamy, V.

    2008-11-01

    Forcing by absorbing atmospheric black carbon (BC) tends to heat the atmosphere, cool the surface, and reduce the surface latent and sensible heat fluxes. BC aerosol can have a large impact on regional climates and the hydrologic cycle. However, significant uncertainties remain concerning the increases in (1) the total amount of all aerosol species and (2) the amount of aerosol absorption that may have occurred over the 1950-1990 period. Focusing on south and east Asia, the sensitivity of a general circulation model's climate response (with prescribed sea surface temperatures and aerosol distributions) to such changes is investigated by considering a range of both aerosol absorption and aerosol extinction optical depth increases. We include direct and semidirect aerosol effects only. Precipitation changes are less sensitive to changes in aerosol absorption optical depth at lower aerosol loadings. At higher-extinction optical depths, low-level convergence and increases in vertical velocity overcome the stabilizing effects of absorbing aerosols and enhance the monsoonal circulation and precipitation in northwestern India. In contrast, the presence of increases in only scattering aerosols weakens the monsoonal circulation and inhibits precipitation here. Cloud amount changes can enhance or counteract surface solar flux reduction depending on the aerosol loading and absorption, with the changes also influencing the surface temperature and the surface energy balance. The results have implications for aerosol reduction strategies in the future that seek to mitigate air pollution concerns. At higher optical depths, if absorbing aerosol is present, reduction of scattering aerosol alone has a reduced effect on precipitation changes, implying that reductions in BC aerosols should be undertaken at the same time as reductions in sulfate aerosols.

  8. Bilateral comparison of blackbody cavities for calibration of infrared ear thermometers between NPL and FE/LMK.

    PubMed

    Pusnik, Igor; Simpson, Rob; Drnovsek, Janko

    2004-10-01

    The paper describes the comparison method and analyses the results of comparison in terms of agreement between the blackbody of the National Physical Laboratory (NPL), United Kingdom and four different blackbody cavities of the Laboratory of Metrology and Quality (LMK), at the University of Ljubljana, Faculty of Electrical Engineering (FE), Slovenia. Three cavity shapes are suggested in different standards as suitable for calibration of infrared ear thermometers (IRETs), while one cavity shape was proposed by the LMK. The agreement between blackbody cavities was determined with the help of platinum resistance thermometers. Two reference IRETs were used to check their stability and level of agreement between calibration results at different institutes and against different blackbody cavities. Measurements were performed with two IRETs, at the NPL in one cavity and at the LMK in four different cavities. The comparison was initiated to solve the problem of assuring proper traceability for IRETs and to present the solution to their users.

  9. Comparison Measurements of Infrared Ear Thermometers Against Three Types of Blackbody Sources

    NASA Astrophysics Data System (ADS)

    Tsai, S. F.

    2010-09-01

    Body temperature is a basic vital sign of the human body, and the use of infrared ear thermometers for medical diagnosis and health management on human bodies has been widespread nowadays. To gain credibility and confidence in the usage of IR ear thermometers, a standard blackbody source (BBS) with a calibration traceable to ITS-90 is necessitated. Three types of cavity-shaped blackbodies (designated BBC-A, BBC-E, and BBC-J) vertically immersed in a temperature-controlled stirred water bath were developed at the Center for Measurement Standards (CMS) as standard BBSs to calibrate and verify 14 commercial IR ear thermometers produced by six manufacturers. The basic structure of each cavity was designed based on the informative examples recommended in ASTM E-1965, EN 12470-5, and JIS T 4207 standards. The temperature of the blackbody cavity shall be represented by the water temperature near the bottom of the cavity that is measured using an immersed platinum resistance thermometer (PRT) for which the calibration is traceable to our national standard and with an uncertainty no greater than 0.03 °C ( k = 2). The water bath was evaluated using the PRT to be stable within ±3.5 mK over 1 h and uniform within ±1.1 mK. Three types of BBSs were compared and analyzed utilizing two IR ear thermometers of 0.01 °C resolution as well as the statistical technique of analysis of variance (ANOVA). On the contrary, IR ear thermometers were tested and verified against three BBSs at three blackbody temperatures of 35.5 °C, 37 °C, and 41 °C. The analysis results of ANOVA showed that there is no significant temperature difference among three different structured blackbodies, and the average measured radiance temperature of three BBSs at 35.5 °C, 37 °C, and 41 °C were within 0.026 °C, 0.024 °C, and 0.027 °C of each other. Three among fourteen IR ear thermometers tested were outside of the 0.2 °C MPE (maximum permissible error) recommended by ASTM E-1965, EN 12470-5, or JIS T

  10. Blackbody-like emission of terahertz radiation from AlGaN/GaN heterostructure under electron heating in lateral electric field

    NASA Astrophysics Data System (ADS)

    Shalygin, V. A.; Vorobjev, L. E.; Firsov, D. A.; Sofronov, A. N.; Melentyev, G. A.; Lundin, W. V.; Nikolaev, A. E.; Sakharov, A. V.; Tsatsulnikov, A. F.

    2011-04-01

    The authors report on the observation and study of terahertz radiation emission from modulation-doped AlGaN/GaN heterostructure under conditions of heating of a two-dimensional electron gas in the lateral electric field. The experimental results are compared with the theoretical model of blackbody-like emission from hot two-dimensional electrons. Complementary transport measurements and a theoretical simulation were carried out to determine the dependence of effective electron temperature on electric field. The role of nonequilibrium optical phonon accumulation is discussed.

  11. Potentially Missing Physics of the Early Universe: Nonlinear Vacuum Polarization in Intense Blackbody Radiation

    SciTech Connect

    Wu, S Q; Hartemann, F V

    2010-04-13

    The standard Big Bang universe model is mainly based on linear interactions, except during exotic periods such as inflation. The purpose of the present proposal is to explore the effects, if any, of vacuum polarization in the very high energy density environment of the early universe. These conditions can be found today in astrophysical settings and may also be emulated in the laboratory using high intensity advanced lasers. Shortly after the Big Bang, there once existed a time when the energy density of the universe corresponded to a temperature in the range 10{sup 8} - 10{sup 9} K, sufficient to cause vacuum polarization effects. During this period, the nonlinear vacuum polarization may have had significant modifications on the propagation of radiation. Thus the thermal spectrum of the early universe may have been starkly non-Planckian. Measurements of the cosmic microwave background today show a spectrum relatively close to an ideal blackbody. Could the early universe have shown spectral deviations due to nonlinear vacuum effects? If so, is it possible to detect traces of those relic photons in the universe today? Found in galactic environments, compact objects such as blazars and magnetars can possess astronomically large energy densities that far exceed anything that can be created in the laboratory. Their field strengths are known to reach energy levels comparable to or surpassing the energy corresponding to the Schwinger critical field E {approx} 10{sup 18} V/m. Nonlinear vacuum effects become prominent under these conditions and have garnered much interest from the astronomical and theoretical physics communities. The effects of a nonlinear vacuum may be of crucial importance for our understanding of these objects. At energies of the order of the electron rest mass, the most important interactions are described by quantum electrodynamics (QED). It is predicted that nonlinear photon-photon interactions will occur at energies approaching the Schwinger

  12. Blackbody material

    DOEpatents

    Lauf, Robert J.; Hamby, Jr., Clyde; Akerman, M. Alfred; Trivelpiece, Alvin W.

    1994-01-01

    A light emitting article comprises a composite of carbon-bonded carbon fibers, prepared by: blending carbon fibers with a carbonizable organic powder to form a mixture; dispersing the mixture into an aqueous slurry; vacuum molding the aqueous slurry to form a green article; drying and curing the green article to form a cured article; and, carbonizing the cured article at a temperature of at least about 1000.degree. C. to form a carbon-bonded carbon fiber light emitting composite article having a bulk density less than 1 g/cm.sup.3.

  13. From Anti-greenhouse Effect of Solar Absorbers to Cooling Effect of Greenhouse Gases: A 1-D Radiative Convective Model Study

    NASA Astrophysics Data System (ADS)

    Shia, R.

    2012-12-01

    The haze layer in Titan's upper atmosphere absorbs 90% of the solar radiation, but is inefficient for trapping infrared radiation generated by the surface. Its existence partially compensates for the greenhouse warming and keeps the surface approximately 9°C cooler than would otherwise be expected from the greenhouse effect alone. This is the so called anti-greenhouse effect (McKay et al., 1991). This effect can be used to alleviate the warming caused by the increasing level of greenhouse gases in the Earth's atmosphere. A one-dimensional radiative convective model (Kasting et al., 2009 and references listed there) is used to investigate the anti-greenhouse effect in the Earth atmosphere. Increasing of solar absorbers, e.g. aerosols and ozone, in the stratosphere reduces the surface solar flux and cool the surface. However, the absorption of the solar flux also increases the temperature in the upper atmosphere, while reduces the temperature at the surface. Thus, the temperature profile of the atmosphere changes and the regions with positive vertical temperature gradient are expanded. According to Shia (2010) the radiative forcing of greenhouse gases is directly related to the vertical temperature gradient. Under the new temperature profile increases of greenhouse gases should have less warming effect. When the solar absorbers keep increasing, eventually most of the atmosphere has positive temperature gradient and increasing greenhouse gases would cool the surface (Shia, 2011). The doubling CO2 scenario in the Earth atmosphere is simulated for different levels of solar absorbers using the 1-D RC model. The model results show that if the solar absorber increases to a certain level that less than 50% solar flux reaching the surface, doubling CO2 cools the surface by about 2 C. This means if the snowball Earth is generated by solar absorbers in the stratosphere, increasing greenhouse gases would make it freeze even more (Shia, 2011). References: Kasting, J. et al

  14. Dataset demonstrating the modeling of a high performance Cu(In,Ga)Se2 absorber based thin film photovoltaic cell.

    PubMed

    Asaduzzaman, Md; Bahar, Ali Newaz; Bhuiyan, Mohammad Maksudur Rahman

    2017-04-01

    The physical data of the semiconductor materials used in the design of a CIGS absorber based thin film photovoltaic cell have been presented in this data article. Besides, the values of the contact parameter and operating conditions of the cell have been reported. Furthermore, by conducting the simulation with data corresponding to the device structure: soda-lime glass (SLG) substrate/Mo back-contact/CIGS absorber/CdS buffer/intrinsic ZnO/Al-doped ZnO window/Al-grid front-contact, the solar cell performance parameters such as open circuit voltage [Formula: see text], short circuit current density [Formula: see text], fill factor [Formula: see text], efficiency [Formula: see text], and collection efficiency [Formula: see text] have been analyzed.

  15. Construction and Characterization of a Large Aperture Blackbody for Infrared Radiometer Calibration

    NASA Astrophysics Data System (ADS)

    Park, Chul-Woung; Yoo, Yong Shim; Kim, Bong-Hak; Chun, Sejong; Park, Seung-Nam

    2011-08-01

    A large aperture blackbody (LABB) with a diameter of 1 m has been successfully constructed for calibrating radiation thermometers and infrared radiometers with a wide field of view in the temperature range between 10 °C and 90 °C. The blackbody is a 1 m long cylindro-conical cavity with a diameter of 1.1 m. Its conical bottom has an apex angle of 120°. To achieve good temperature stability and uniformity, the cavity is integrated to a water-bath to which the pressurized water is supplied from a reservoir. To reduce the convection heat loss from the cavity to the ambient, the cavity is purged of the dried air that passes through a coiled tube immersed in the reservoir. For an uncertainty evaluation of the LABB, its temperature stability was measured by using a reference radiation thermometer (RRT) and a platinum resistance thermometer (PRT), and its radiance temperature distributions on the aperture plane were measured by using a thermal camera. Measuring the spectral emissivity of the coating material, the effective emissivity of the blackbody was calculated to be 0.9955 from 1 μm to 15 μm. The expanded uncertainty of the radiance temperature scale was evaluated based on the PRT readings, which vary from 0.3 °C to 0.5 °C ( k = 2) in the temperature range. The temperature scale is validated by comparing with the RRT of which the temperature scale is realized by a multiple fixed-point calibration.

  16. Upper limits to near-field radiative heat transfer: generalizing the blackbody concept

    NASA Astrophysics Data System (ADS)

    Miller, Owen D.; Rodriguez, Alejandro W.; Johnson, Steven G.

    2016-09-01

    For 75 years it has been known that radiative heat transfer can exceed far-field blackbody rates when two bodies are separated by less than a thermal wavelength. Yet an open question has remained: what is the maximum achievable radiative transfer rate? Here we describe basic energy-conservation principles that answer this question, yielding upper bounds that depend on the temperatures, material susceptibilities, and separation distance, but which encompass all geometries. The simple structures studied to date fall far short of the bounds, offering the possibility for significant future enhancement, with ramifications for experimental studies as well as thermophotovoltaic applications.

  17. Fresnel Lens Solar Concentrator Design Based on Geometric Optics and Blackbody Radiation Equations

    NASA Technical Reports Server (NTRS)

    Watson, Michael D.; Jayroe, Robert, Jr.

    1999-01-01

    Fresnel lenses have been used for years as solar concentrators in a variety of applications. Several variables effect the final design of these lenses including: lens diameter, image spot distance from the lens, and bandwidth focused in the image spot. Defining the image spot as the geometrical optics circle of least confusion and applying blackbody radiation equations the spot energy distribution can be determined. These equations are used to design a fresnel lens to produce maximum flux for a given spot size, lens diameter, and image distance. This approach results in significant increases in solar efficiency over traditional single wavelength designs.

  18. The Aspects About of Objectively Appraisals of Modeling Gypsum Quality and Composites of Phonic-Absorbent and Orthopedic on Base of Gypsum

    NASA Astrophysics Data System (ADS)

    Pop, P. A.; Ungur, P. A.; Lazar, L.; Marcu, F.

    2009-11-01

    The EU Norms about of protection environment, outside and inside ambient, and human health demands has lead at obtain of new materials on the base of airborne material, with high thermo and phonic-absorbent properties, porous and lightweight. The α and β-modeling gypsum plaster quality and lightweight depend on many factors as: fabrication process, granulation, roast temperature, work temperature, environment, additives used, breakage, etc. Also, the objectively appraisal of modeling gypsum quality depends of proper tests methods selection, which are legislated in norms, standards and recommendations. In Romanian Standards SR EN 13279-1/2005 and SR EN 13279-2/2005, adaptable from EU Norms EN 13279-1/2004 and EN 13279-2/2004, the characteristics gypsum family tests are well specification, as: granule-metric analysis, determination of water/plaster ratio, setting time, mechanical characteristics, adhesions and water restrain. For plaster with special use (phonic-absorbent and orthopedic materials, etc.) these determinations are not concluding, being necessary more parameters finding, as: elastic constant, phonic-absorbent coefficient, porosity, working, etc., which is imposed the completion of norms and standards with new determinations.

  19. Composition for absorbing hydrogen

    DOEpatents

    Heung, Leung K.; Wicks, George G.; Enz, Glenn L.

    1995-01-01

    A hydrogen absorbing composition. The composition comprises a porous glass matrix, made by a sol-gel process, having a hydrogen-absorbing material dispersed throughout the matrix. A sol, made from tetraethyl orthosilicate, is mixed with a hydrogen-absorbing material and solidified to form a porous glass matrix with the hydrogen-absorbing material dispersed uniformly throughout the matrix. The glass matrix has pores large enough to allow gases having hydrogen to pass through the matrix, yet small enough to hold the particles dispersed within the matrix so that the hydrogen-absorbing particles are not released during repeated hydrogen absorption/desorption cycles.

  20. Composition for absorbing hydrogen

    DOEpatents

    Heung, L.K.; Wicks, G.G.; Enz, G.L.

    1995-05-02

    A hydrogen absorbing composition is described. The composition comprises a porous glass matrix, made by a sol-gel process, having a hydrogen-absorbing material dispersed throughout the matrix. A sol, made from tetraethyl orthosilicate, is mixed with a hydrogen-absorbing material and solidified to form a porous glass matrix with the hydrogen-absorbing material dispersed uniformly throughout the matrix. The glass matrix has pores large enough to allow gases having hydrogen to pass through the matrix, yet small enough to hold the particles dispersed within the matrix so that the hydrogen-absorbing particles are not released during repeated hydrogen absorption/desorption cycles.

  1. The 3 K blackbody radiation, Dirac's Large Numbers Hypothesis, and scale-covariant cosmology

    NASA Technical Reports Server (NTRS)

    Canuto, V.; Hsieh, S.-H.

    1978-01-01

    A program is described which is intended to derive a generalized system of gravitational equations that allow (but do not require) G to vary, to use the 3-K blackbody radiation to fix the relation between G and the gauge function, and to employ Dirac's (1937) Large Numbers Hypothesis to derive the geometry of the universe. Einstein's equations are retained in their total integrity, but the specification is made that they are valid only when gravitational units are used. A scale-invariant form of Einstein's equations is obtained, and from this are derived the energy conservation law, the baryon-number conservation law, and the appropriate cosmological equations. Dirac's proposals of 1937 and 1973 are incorporated into the formalism, and a gauge based on consolidation of the 3-K blackbody radiation is presented. A unique solution for the geometry of the universe is determined for zero curvature solely from the 3-K radiation and the Large Numbers Hypothesis; this solution predicts a deceleration parameter exactly equal to unity.

  2. Development of the blackbody probe type pyrometer, part 1. Experimental study on the fundamental characteristics

    NASA Astrophysics Data System (ADS)

    Hisamatsu, Toru; Mori, Noriyuki; Hamamatsu, Teruhide; Abe, Toshio

    1988-06-01

    For the benefit of the monitoring and controlling high temperature equipment, such as a coal gasification furnace or a gas turbine, measuring the internal temperature of equipment is very important. The black body probe type pyrometer using cavity radiation was designed and studied to develop a pyrometer with high accuracy of measurement in very high temperature of nearly 2000 C or in the corrosive ambient atmosphere. This pyrometer has a small spherical cavity as a pseudo-blackbody at the tip of its probe. Temperature measurement with this pyrometer is carried out by measuring infrared radiation from the cavity. It was shown that the ceramic probe with microcavity can be manufactured by sintering an assembly of powder mouldings to one body. As a calibration result of this pyrometer using an electric furnace, the infrared radiation output of the probe conformed with one measured by a blackbody furnace for calibration with an error of + or - 1 percent or less. The accuracy of temperature measurement was as high as that of the thermocouple.

  3. A model for the pressure excitation spectrum and acoustic impedance of sound absorbers in the presence of grazing flow

    NASA Technical Reports Server (NTRS)

    Rice, E. J.

    1973-01-01

    The acoustic impedance of sound absorbers in the presence of grazing flow is essential information when analyzing sound propagation within ducts. A unification of the theory of the nonlinear acoustic resistance of Helmholtz resonators including grazing flow is presented. The nonlinear resistance due to grazing flow is considered to be caused by an exciting pressure spectrum produced by the interaction of the grazing flow and the jets flowing from the resonator orifices. With this exciting pressure spectrum the resonator can be treated in the same manner as a resonator without grazing flow but with an exciting acoustic spectrum.

  4. Compound A production from sevoflurane is not less when KOH-free absorbent is used in a closed-circuit lung model system.

    PubMed

    Versichelen, L; Bouche, M P; Struys, M; Van Bocxlaer, J; Mortier, E; de Leenheer, A P; Rolly, G

    2001-03-01

    In an in vitro study, less compound A was formed when a KOH-free carbon dioxide absorbent was used. To confirm this observation we used a lung model in which carbon dioxide was fed in at 160 ml min(-1) and sampling gas was taken out for analysis at 200 ml min(-1); ventilation aimed for a PE'CO2 of 5.4 kPa. The soda lime canister temperatures in the inflow and outflow ports (Tin and Tout) were recorded. In six runs of 240 min each, a standard soda lime, Sodasorb (Grace, Epernon, France) was used and in eight runs KOH-free Sofnolime (Molecular Products, Thaxted, UK) was used. Liquid sevoflurane was injected using a syringe pump to obtain 2.1% E'. Compound A was measured by capillary gas chromatography combined with mass spectrometry. Median (range) compound Ainsp increased to a maximum of 22.7 (7.9) ppm for Sodasorb and 33.1 (20) for Sofnolime at 60 min and decreased thereafter; the difference between groups was significant (P<0.05) at each time of analysis up to 240 min. The canister temperatures were similar in both groups and increased to approximately 40 degrees C at 240 min. Contrary to expectation, compound A concentrations were greater with the KOH-free absorbent despite similar canister temperatures with both absorbents.

  5. Modelling potential photovoltaic absorbers Cu3MCh4(M = V, Nb, Ta; Ch = S, Se, Te) using density functional theory.

    PubMed

    Kehoe, Aoife B; Scanlon, David O; Watson, Graeme W

    2016-05-05

    The geometric and electronic properties of a series of potential photovoltaic materials, the sulvanite structured Cu3MCh4(M = V, Nb, Ta; Ch = S, Se, Te), have been computationally examined using both PBEsol+U and HSE06 methods to assess the materials' suitability for solar cell application and to compare the predictions of the two theoretical approaches. The lattice parameters, electronic density of states, and band gaps of the compounds have been calculated to ascertain the experimental agreement obtained by each method and to determine if any of the systems have an optical band gap appropriate for photovoltaic absorber materials. The PBEsol+U results are shown to achieve better agreement with experiment than HSE06 in terms of both lattice constants and band gaps, demonstrating that higher level theoretical methods do not automatically result in a greater level of accuracy than their computationally less expensive counterparts. The PBEsol+U calculated optical band gaps of five materials suggest potential suitability as photovoltaic absorbers, with values of 1.72 eV, 1.49 eV, 1.19 eV, 1.46 eV, and 1.69 eV for Cu3VS4, Cu3VSe4, Cu3VTe4, Cu3NbTe4, and Cu3TaTe4, respectively, although it should be noted that all fundamental band gaps are indirect in nature, which could lower the open-circuit voltage and hence the efficiency of prospective devices.

  6. Ferroelectrics based absorbing layers

    NASA Astrophysics Data System (ADS)

    Hao, Jianping; Sadaune, Véronique; Burgnies, Ludovic; Lippens, Didier

    2014-07-01

    We show that ferroelectrics-based periodic structure made of BaSrTiO3 (BST) cubes, arrayed onto a metal plate with a thin dielectric spacer film exhibit a dramatic enhancement of absorbance with value close to unity. The enhancement is found around the Mie magnetic resonance of the Ferroelectrics cubes with the backside metal layer stopping any transmitted waves. It also involves quasi-perfect impedance matching resulting in reflection suppression via simultaneous magnetic and electrical activities. In addition, it was shown numerically the existence of a periodicity optimum, which is explained from surface waves analysis along with trade-off between the resonance damping and the intrinsic loss of ferroelectrics cubes. An experimental verification in a hollow waveguide configuration with a good comparison with full-wave numerical modelling is at last reported by measuring the scattering parameters of single and dual BST cubes schemes pointing out coupling effects for densely packed structures.

  7. THz-metamaterial absorbers

    NASA Astrophysics Data System (ADS)

    Tuong Pham, Van; Park, J. W.; Vu, Dinh Lam; Zheng, H. Y.; Rhee, J. Y.; Kim, K. W.; Lee, Y. P.

    2013-03-01

    An ultrabroad-band metamaterial absorber was investigated in mid-IR regime based on a similar model in previous work. The high absorption of metamaterial was obtained in a band of 8-11.7 THz with energy loss distributed in SiO2, which is appropriate potentially for solar-cell applications. A perfect absorption peak was provided by using a sandwich structure with periodical anti-dot pattern in the IR region, getting closed to visible-band metamaterials. The dimensional parameters were examined for the corresponding fabrication. Invited talk at the 6th International Workshop on Advanced Materials Science and Nanotechnology, 30 October-2 November, 2012, Ha Long, Vietnam.

  8. Externally tuned vibration absorber

    DOEpatents

    Vincent, Ronald J.

    1987-09-22

    A vibration absorber unit or units are mounted on the exterior housing of a hydraulic drive system of the type that is powered from a pressure wave generated, e.g., by a Stirling engine. The hydraulic drive system employs a piston which is hydraulically driven to oscillate in a direction perpendicular to the axis of the hydraulic drive system. The vibration absorbers each include a spring or other resilient member having one side affixed to the housing and another side to which an absorber mass is affixed. In a preferred embodiment, a pair of vibration absorbers is employed, each absorber being formed of a pair of leaf spring assemblies, between which the absorber mass is suspended.

  9. Shock absorber control system

    SciTech Connect

    Nakano, Y.; Ohira, M.; Ushida, M.; Miyagawa, T.; Shimodaira, T.

    1987-01-13

    A shock absorber control system is described for controlling a dampening force of a shock absorber of a vehicle comprising: setting means for setting a desired dampening force changeable within a predetermined range; drive means for driving the shock absorber to change the dampening force of the shock absorber linearly; control means for controlling the drive means in accordance with the desired dampening force when the setting of the desired dampening force has been changed; detecting means for detecting an actual dampening force of the shock absorber; and correcting means for correcting the dampening force of the shock absorber by controlling the drive means in accordance with a difference between the desired dampening force and the detected actual dampening force.

  10. CPCs with segmented absorbers

    SciTech Connect

    Keita, M.; Robertson, H.S. )

    1991-01-01

    One of the most promising means of improving the performance of solar thermal collectors is to reduce the energy lost by the hot absorber. One way to do this, not currently part of the technology, is to recognize that since the absorber is usually not irradiated uniformly, it is therefore possible to construct an absorber of thermally isolated segments, circulate the fluid in sequence from low to high irradiance segments, and reduce loss by improving effective concentration. This procedure works even for ideal concentrators, without violating Winston's theorem. Two equivalent CPC collectors with single and segmented absorber were constructed and compared under actual operating conditions. The results showed that the daily thermal efficiency of the collector with segmented absorber is higher (about 13%) than that of the collector with nonsegmented absorber.

  11. Methods for absorbing neutrons

    DOEpatents

    Guillen, Donna P [Idaho Falls, ID; Longhurst, Glen R [Idaho Falls, ID; Porter, Douglas L [Idaho Falls, ID; Parry, James R [Idaho Falls, ID

    2012-07-24

    A conduction cooled neutron absorber may include a metal matrix composite that comprises a metal having a thermal neutron cross-section of at least about 50 barns and a metal having a thermal conductivity of at least about 1 W/cmK. Apparatus for providing a neutron flux having a high fast-to-thermal neutron ratio may include a source of neutrons that produces fast neutrons and thermal neutrons. A neutron absorber positioned adjacent the neutron source absorbs at least some of the thermal neutrons so that a region adjacent the neutron absorber has a fast-to-thermal neutron ratio of at least about 15. A coolant in thermal contact with the neutron absorber removes heat from the neutron absorber.

  12. Design and analysis on fume exhaust system of blackbody cavity sensor for continuously measuring molten steel temperature

    NASA Astrophysics Data System (ADS)

    Mei, Guohui; Zhang, Jiu; Zhao, Shumao; Xie, Zhi

    2017-03-01

    Fume exhaust system is the main component of the novel blackbody cavity sensor with a single layer tube, which removes the fume by gas flow along the exhaust pipe to keep the light path clean. However, the gas flow may break the conditions of blackbody cavity and results in the poor measurement accuracy. In this paper, we analyzed the influence of the gas flow on the temperature distribution of the measuring cavity, and then calculated the integrated effective emissivity of the non-isothermal cavity based on Monte-Carlo method, accordingly evaluated the sensor measurement accuracy, finally obtained the maximum allowable flow rate for various length of the exhaust pipe to meet the measurement accuracy. These results will help optimize the novel blackbody cavity sensor design and use it better for measuring the temperature of molten steel.

  13. Additive manufacturing of RF absorbers

    NASA Astrophysics Data System (ADS)

    Mills, Matthew S.

    The ability of additive manufacturing techniques to fabricate integrated electromagnetic absorbers tuned for specific radio frequency bands within structural composites allows for unique combinations of mechanical and electromagnetic properties. These composites and films can be used for RF shielding of sensitive electromagnetic components through in-plane and out-of-plane RF absorption. Structural composites are a common building block of many commercial platforms. These platforms may be placed in situations in which there is a need for embedded RF absorbing properties along with structural properties. Instead of adding radar absorbing treatments to the external surface of existing structures, which adds increased size, weight and cost; it could prove to be advantageous to integrate the microwave absorbing properties directly into the composite during the fabrication process. In this thesis, a method based on additive manufacturing techniques of composites structures with prescribed electromagnetic loss, within the frequency range 1 to 26GHz, is presented. This method utilizes screen printing and nScrypt micro dispensing to pattern a carbon based ink onto low loss substrates. The materials chosen for this study will be presented, and the fabrication technique that these materials went through to create RF absorbing structures will be described. The calibration methods used, the modeling of the RF structures, and the applications in which this technology can be utilized will also be presented.

  14. Thermodynamic limits to the conversion of blackbody radiation by quantum systems. [with application to solar energy conversion devices

    NASA Technical Reports Server (NTRS)

    Buoncristiani, A. M.; Smith, B. T.; Byvik, C. E.

    1982-01-01

    Using general thermodynamic arguments, we analyze the conversion of the energy contained in the radiation from a blackbody to useful work by a quantum system. We show that the energy available for conversion is bounded above by the change in free energy in the incident and reradiated fields and that this free energy change depends upon the temperature of the receiving device. Universal efficiency curves giving the ultimate thermodynamic conversion efficiency of the quantum system are presented in terms of the blackbody temperature and the temperature and threshold energy of the quantum system. Application of these results is made to a variety of systems including biological photosynthetic, photovoltaic, and photoelectrochemical systems.

  15. Theoretical development and validation of a Sharp Front model of the dewatering of a slurry by an absorbent substrate

    NASA Astrophysics Data System (ADS)

    Collier, N. C.; Wilson, M. A.; Carter, M. A.; Hoff, W. D.; Hall, Christopher; Ball, R. J.; El-Turki, A.; Allen, G. C.

    2007-07-01

    The absorption of water from a slurry into an absorbent substrate is analysed using Sharp Front theory. The analysis describes the relationship between the sorptivity S of the substrate, the desorptivity R of the slurry and the transfer sorptivity A between slurry and substrate, and leads to the relationship 1/A2 = 1/R2 + 1/S2. Experimental data are presented which validate this equation for the practically important case of the absorption of water from soft mortar mixes by fired clay bricks. A unique feature of the experimental work is the measurement of the desorptivity of the mortars at a pressure equal to the wetting front capillary pressure of the clay brick substrate. Analysis of the experimental data also enables, for the first time, the calculation of the capillary potential at the slurry/substrate interface. The analysis has relevance to many aspects of ceramic and mineral processing, industrial filtration and construction engineering.

  16. Three-dimensional model of zeaxanthin binding PsbS protein associated with nonphotochemical quenching of excess quanta of light energy absorbed by the photosynthetic apparatus.

    PubMed

    Haripal, Prafulla K; Raval, Hemant K; Raval, Mukesh K; Rawal, Rakesh M; Biswal, Basanti; Biswal, Udaya C

    2006-09-01

    A three-dimensional model of the PsbS protein was built with the help of homology-modeling methods. This protein is also known as CP22 and is associated with the protection of photosystem II of thylakoid from excess quanta of light energy absorbed by the photosynthetic apparatus. PsbS is reported to bind two molecules of zeaxanthin at low pH (<5.0) and is believed to be essential for rapid nonphotochemical quenching (qE) of chlorophyll a fluorescence in photosystem II. An attempt was made to explain the pH modulation of the conformation of protein through salt-bridges Glu(-)(122)-Lys(+)(113) and Glu(-)(226)-Lys(+)(217). Binding of two molecules of zeaxanthin in the three-dimensional model of PsbS is postulated. The molecular mechanism of photoprotection by PsbS is explained through the model.

  17. Electromagnetic scattering by pyramidal and wedge absorber

    NASA Technical Reports Server (NTRS)

    Dewitt, Brian T.; Burnside, Walter D.

    1988-01-01

    Electromagnetic scattering from pyramidal and wedge absorbers used to line the walls of modern anechoic chambers is measured and compared with theoretically predicted values. The theoretical performance for various angles of incidence is studied. It is shown that a pyramidal absorber scatters electromagnetic energy more as a random rough surface does. The apparent reflection coefficient from an absorber wall illuminated by a plane wave can be much less than the normal absorber specifications quoted by the manufacturer. For angles near grazing incidence, pyramidal absorbers give a large backscattered field from the pyramid side-faces or edges. The wedge absorber was found to give small backscattered fields for near-grazing incidence. Based on this study, some new guidelines for the design of anechoic chambers are advocated because the specular scattering models used at present do not appear valid for pyramids that are large compared to the wavelength.

  18. Advanced neutron absorber materials

    DOEpatents

    Branagan, Daniel J.; Smolik, Galen R.

    2000-01-01

    A neutron absorbing material and method utilizing rare earth elements such as gadolinium, europium and samarium to form metallic glasses and/or noble base nano/microcrystalline materials, the neutron absorbing material having a combination of superior neutron capture cross sections coupled with enhanced resistance to corrosion, oxidation and leaching.

  19. A simple blackbody simulator with several possibilities and applications on thermography

    NASA Astrophysics Data System (ADS)

    dos Santos, Laerte; Lemos, Alisson Maria; Abi-Ramia, Marco Antônio

    2016-05-01

    Originally designed to make the practical examination on thermography certification1 possible, the device presented in this paper has demonstrated to be a very useful and versatile didactic tool for training centers and educational institutions, it can also be used as a low cost blackbody simulator to verify calibration of radiometers. It is a simple device with several functionalities for studying and for applications on heat transfer and radiometry, among them the interesting ability to thermally simulate the surface of real objects. On that functionality, if the device is seen by a thermographic camera, it reproduces the surface apparent temperatures of the object that it is simulating, at the same time, if it is seen by a naked eye it shows a visible image of that same surface. This functionality makes the practical study in the classroom possible, from different areas such as electrical, mechanical, medical, building, veterinary, etc.

  20. Chemical reactivity on gas-phase metal clusters driven by blackbody infrared radiation.

    PubMed

    Parry, Imogen S; Kartouzian, Aras; Hamilton, Suzanne M; Balaj, O Petru; Beyer, Martin K; Mackenzie, Stuart R

    2015-01-19

    We report the observation of chemical reactions in gas-phase Rh(n)(N2O)m(+) complexes driven by absorption of blackbody radiation. The experiments are performed under collision-free conditions in a Fourier transform ion cyclotron resonance mass spectrometer. Mid-infrared absorption by the molecularly adsorbed N2O moieties promotes a small fraction of the cluster distribution sufficiently to drive the N2O decomposition reaction, leading to the production of cluster oxides and the release of molecular nitrogen. N2O decomposition competes with molecular desorption and the branching ratios for the two processes show marked size effects, reflecting variations in the relative barriers. The rate of decay is shown to scale approximately linearly with the number of infrared chromophores. The experimental findings are interpreted in terms of calculated infrared absorption rates assuming a sudden-death limit.

  1. Black-body radiation in a curved Robertson-Walker background

    NASA Astrophysics Data System (ADS)

    Deng, Yaobing; Mannheim, Philip D.

    1987-07-01

    In the standard Friedmann cosmology the black-body radiation spectrum is usually taken to have the same familiar T4-form that it has in a flat space. With explicit use of the equation of motion of a quantized massless field propagating in a curved background Robertson-Walker metric the authors show (for the readily tractable scalar field case) that the assumption is in fact true for an open Universe. For a closed Universe, it is found that there is an in principle modification to the T4-law. Unfortunately, the correction turns out to be too small to be experimentally detectable. In passing, the authors also obtain a simple derivation for the cosmological red shift of frequencies.

  2. Atomic Clock with 1 ×10-18 Room-Temperature Blackbody Stark Uncertainty

    NASA Astrophysics Data System (ADS)

    Beloy, K.; Hinkley, N.; Phillips, N. B.; Sherman, J. A.; Schioppo, M.; Lehman, J.; Feldman, A.; Hanssen, L. M.; Oates, C. W.; Ludlow, A. D.

    2014-12-01

    The Stark shift due to blackbody radiation (BBR) is the key factor limiting the performance of many atomic frequency standards, with the BBR environment inside the clock apparatus being difficult to characterize at a high level of precision. Here we demonstrate an in-vacuum radiation shield that furnishes a uniform, well-characterized BBR environment for the atoms in an ytterbium optical lattice clock. Operated at room temperature, this shield enables specification of the BBR environment to a corresponding fractional clock uncertainty contribution of 5.5 ×10-19 . Combined with uncertainty in the atomic response, the total uncertainty of the BBR Stark shift is now 1 ×10-18. Further operation of the shield at elevated temperatures enables a direct measure of the BBR shift temperature dependence and demonstrates consistency between our evaluated BBR environment and the expected atomic response.

  3. Fresnel lens solar concentrator design based on geometric optics and blackbody radiation equations

    SciTech Connect

    Watson, M.D.; Jayroe, R.R. Jr.

    1999-07-01

    Fresnel lenses have been used for years as solar concentrators in a variety of applications. Several variables affect the final design of these lenses including: lens diameter, image spot distance from the lens, and bandwidth focused in the image spot. Defining the image spot as the geometrical optics circle of least confusion, a set of design equations has been derived to define the groove angles for each groove on the lens. These equations allow the distribution of light by wavelength within the image spot to be calculated. Combining these equations with the blackbody radiation equations power, power distribution, and flux within the image spot can be calculated. In addition, equations have been derived to design a lens to produce maximum flux in a given spot size. Using these equations, a lens may be designed to optimize the spot energy concentration for given energy source.

  4. Fresnel Lens Solar Concentrator Design Based on Geometric Optics and Blackbody Radiation Equations

    NASA Technical Reports Server (NTRS)

    Watson, Michael D.; Jayroe, Robert

    1998-01-01

    Fresnel lenses have been used for years as solar concentrators in a variety of applications. Several variables effect the final design of these lenses including: lens diameter, image spot distance from the lens, and bandwidth focused in the image spot. Defining the image spot as the geometrical optics circle of least confusion, a set of design equations has been derived to define the groove angles for each groove on the lens. These equations allow the distribution of light by wavelength within the image spot to be calculated. Combining these equations with the blackbody radiation equations, energy distribution, power, and flux within the image spot can be calculated. In addition, equations have been derived to design a lens to produce maximum flux in a given spot size. Using these equations, a lens may be designed to optimize the spot energy concentration for given energy source.

  5. Isotropic blackbody cosmic microwave background radiation as evidence for a homogeneous universe.

    PubMed

    Clifton, Timothy; Clarkson, Chris; Bull, Philip

    2012-08-03

    The question of whether the Universe is spatially homogeneous and isotropic on the largest scales is of fundamental importance to cosmology but has not yet been answered decisively. Surprisingly, neither an isotropic primary cosmic microwave background (CMB) nor combined observations of luminosity distances and galaxy number counts are sufficient to establish such a result. The inclusion of the Sunyaev-Zel'dovich effect in CMB observations, however, dramatically improves this situation. We show that even a solitary observer who sees an isotropic blackbody CMB can conclude that the Universe is homogeneous and isotropic in their causal past when the Sunyaev-Zel'dovich effect is present. Critically, however, the CMB must either be viewed for an extended period of time, or CMB photons that have scattered more than once must be detected. This result provides a theoretical underpinning for testing the cosmological principle with observations of the CMB alone.

  6. Natural widths and blackbody radiation induced shift and broadening of Rydberg levels in magnesium ions

    NASA Astrophysics Data System (ADS)

    Glukhov, Igor L.; Mokhnenko, Sergey N.; Nikitina, Elizaveta A.; Ovsiannikov, Vitaly D.

    2015-01-01

    Theoretical analysis is presented of the natural lifetimes and blackbody-radiation (BBR)-induced shifts and widths of Rydberg states with small and large angular momenta l. Asymptotic presentations in elementary functions are derived for matrix elements of bound-bound, bound-free and threshold radiative transitions from hydrogenic-type states with large angular momenta, applicable to both hydrogen-like and many-electron atoms and ions. For states with small angular momenta two numerical methods based on the quantum defects were used and corresponding data are compared with one another and with the most reliable data of the literature. Asymptotic approximations are derived for natural lifetimes, thermal shifts and broadening of Rydberg states of small and high l and principal quantum numbers n ≫ 1.

  7. Multispectral metamaterial absorber.

    PubMed

    Grant, J; McCrindle, I J H; Li, C; Cumming, D R S

    2014-03-01

    We present the simulation, implementation, and measurement of a multispectral metamaterial absorber (MSMMA) and show that we can realize a simple absorber structure that operates in the mid-IR and terahertz (THz) bands. By embedding an IR metamaterial absorber layer into a standard THz metamaterial absorber stack, a narrowband resonance is induced at a wavelength of 4.3 μm. This resonance is in addition to the THz metamaterial absorption resonance at 109 μm (2.75 THz). We demonstrate the inherent scalability and versatility of our MSMMA by describing a second device whereby the MM-induced IR absorption peak frequency is tuned by varying the IR absorber geometry. Such a MSMMA could be coupled with a suitable sensor and formed into a focal plane array, enabling multispectral imaging.

  8. Depth dependence of absorbed dose, dose equivalent and linear energy transfer spectra of galactic and trapped particles in polyethylene and comparison with calculations of models

    NASA Technical Reports Server (NTRS)

    Badhwar, G. D.; Cucinotta, F. A.; Wilson, J. W. (Principal Investigator)

    1998-01-01

    A matched set of five tissue-equivalent proportional counters (TEPCs), embedded at the centers of 0 (bare), 3, 5, 8 and 12-inch-diameter polyethylene spheres, were flown on the Shuttle flight STS-81 (inclination 51.65 degrees, altitude approximately 400 km). The data obtained were separated into contributions from trapped protons and galactic cosmic radiation (GCR). From the measured linear energy transfer (LET) spectra, the absorbed dose and dose-equivalent rates were calculated. The results were compared to calculations made with the radiation transport model HZETRN/NUCFRG2, using the GCR free-space spectra, orbit-averaged geomagnetic transmission function and Shuttle shielding distributions. The comparison shows that the model fits the dose rates to a root mean square (rms) error of 5%, and dose-equivalent rates to an rms error of 10%. Fairly good agreement between the LET spectra was found; however, differences are seen at both low and high LET. These differences can be understood as due to the combined effects of chord-length variation and detector response function. These results rule out a number of radiation transport/nuclear fragmentation models. Similar comparisons of trapped-proton dose rates were made between calculations made with the proton transport model BRYNTRN using the AP-8 MIN trapped-proton model and Shuttle shielding distributions. The predictions of absorbed dose and dose-equivalent rates are fairly good. However, the prediction of the LET spectra below approximately 30 keV/microm shows the need to improve the AP-8 model. These results have strong implications for shielding requirements for an interplanetary manned mission.

  9. On the physical and geometrical properties responsible for the highly absorbing nature of black materials in the infrared

    NASA Astrophysics Data System (ADS)

    Meier, Steven Robert

    Black surfaces are of paramount importance in the design of terrestrial and space-borne optical systems. Optical designers can choose from a variety of black materials to suppress reflected and scattered stray light. Among these applications are the suppression of unwanted reflection or scattering of light in optical systems, solar collectors, blackbody absorbers, thermal insulators, telescope housing and baffles where stray light reduction is vital, and cold stops and light shields for infrared detectors. The physical mechanisms responsible for understanding the highly absorbing nature of black materials in the infrared spectral region are investigated in this dissertation. We present experimental data on the optical, surface, and constituent properties of black materials. In addition, we developed unique optical instrumentation to characterize the hemispherical reflectance and scattering properties of these materials as a function of incident angle and state of polarization. We compared the experimental data to theoretical rough surface scattering models to understand the absorption mechanisms of these black materials and found good agreement. Furthermore, results from a new, highly absorbing black material in the infrared wavelength regime, known as carbon aerogels, are presented and shown to be superior or equivalent to existing black materials used by optical designers. In addition, we presented a new cylindrical-spherical cavity enclosure and calculated the apparent emissivity along the bounding surfaces of this new cavity enclosure. To our knowledge, this was the first calculation of the apparent emissivity for a cavity enclosure with obscuration. Finally, we proposed several improvements for each individual black material in order to achieve even higher absorption levels.

  10. Nonlinear dynamic vibration absorbers with a saturation

    NASA Astrophysics Data System (ADS)

    Febbo, M.; Machado, S. P.

    2013-03-01

    The behavior of a new type of nonlinear dynamic vibration absorber is studied. A distinctive characteristic of the proposed absorber is the impossibility to extend the system to infinity. The mathematical formulation is based on a finite extensibility nonlinear elastic potential to model the saturable nonlinearity. The absorber is attached to a single degree-of-freedom linear/nonlinear oscillator subjected to a periodic external excitation. In order to solve the equations of motion and to analyze the frequency-response curves, the method of averaging is used. The performance of the FENE absorber is evaluated considering a variation of the nonlinearity of the primary system, the damping and the linearized frequency of the absorber and the mass ratio. The numerical results show that the proposed absorber has a very good efficiency when the nonlinearity of the primary system increases. When compared with a cubic nonlinear absorber, for a large nonlinearity of the primary system, the FENE absorber shows a better effectiveness for the whole studied frequency range. A complete absence of quasi-periodic oscillations is also found for an appropriate selection of the parameters of the absorber. Finally, direct integrations of the equations of motion are performed to verify the accuracy of the proposed method.

  11. Internal absorber solar collector

    DOEpatents

    Sletten, Carlyle J.; Herskovitz, Sheldon B.; Holt, F. S.; Sletten, E. J.

    1981-01-01

    Thin solar collecting panels are described made from arrays of small rod collectors consisting of a refracting dielectric rod lens with an absorber imbedded within it and a reflecting mirror coated on the back side of the dielectric rod. Non-tracking collector panels on vertical walls or roof tops receive approximately 90% of solar radiation within an acceptance zone 60.degree. in elevation angle by 120.degree. or more in the azimuth sectors with a collector concentration ratio of approximately 3.0. Miniaturized construction of the circular dielectric rods with internal absorbers reduces the weight per area of glass, plastic and metal used in the collector panels. No external parts or insulation are needed as heat losses are low due to partial vacuum or low conductivity gas surrounding heated portions of the collector. The miniature internal absorbers are generally made of solid copper with black selective surface and the collected solar heat is extracted at the collector ends by thermal conductivity along the absorber rods. Heat is removed from end fittings by use of liquid circulants. Several alternate constructions are provided for simplifying collector panel fabrication and for preventing the thermal expansion and contraction of the heated absorber or circulant tubes from damaging vacuum seals. In a modified version of the internal absorber collector, oil with temperature dependent viscosity is pumped through a segmented absorber which is now composed of closely spaced insulated metal tubes. In this way the circulant is automatically diverted through heated portions of the absorber giving higher collector concentration ratios than theoretically possible for an unsegmented absorber.

  12. Lipid-absorbing Polymers

    NASA Technical Reports Server (NTRS)

    Marsh, H. E., Jr.; Wallace, C. J.

    1973-01-01

    The removal of bile acids and cholesterol by polymeric absorption is discussed in terms of micelle-polymer interaction. The results obtained with a polymer composed of 75 parts PEO and 25 parts PB plus curing ingredients show an absorption of 305 to 309%, based on original polymer weight. Particle size effects on absorption rate are analyzed. It is concluded that crosslinked polyethylene oxide polymers will absorb water, crosslinked polybutadiene polymers will absorb lipids; neither polymer will absorb appreciable amounts of lipids from micellar solutions of lipids in water.

  13. Electromagnetic power absorber

    NASA Technical Reports Server (NTRS)

    Iwasaki, R. S. (Inventor)

    1979-01-01

    A structure is presented with a surface portion of dielectric material which passes electromagnetic radiation and with a portion below the surface which includes material that absorbs the radiation, the face of the structure being formed with numerous steep ridges. The steepness of the dielectric material results in a high proportion of the electromagnetic energy passing through the surface for absorption by the absorbing material under the surface. A backing of aluminum or other highly heat-conductive and reflective material lies under the face and has very steep protuberances supporting the absorbing and dielectric materials.

  14. Modeling Laser-Tissue Interactions: Implementing the Heat Diffusion Equation and Wave Equation to Simulate Thermal Interactions of Absorber Distributions in Biological Tissues

    NASA Astrophysics Data System (ADS)

    Barrera, Frederick; Ahmed, Elharith; Nash, Patrick; Sardar, Dhiraj

    2011-03-01

    The tracking of photons through turbid media (e.g. tissues) has been studied extensively from an experimental vantage point. These turbid media are difficult to characterize- since their components are exceedingly variegated- and thus present many challenges to clinicians who require models which precisely predict the location and time evolution of energy deposition. Furthermore, the interaction of the turbid media sample with the source of radiation typically involves many dynamic mechanisms (e.g. photothermal etc.) Using diffuse light transport, and an electromagnetic wave approach (e.g. Maxwell's equations), an analysis of thermal energy distribution in tissues is performed. Assuming a highly absorbing chromophore model of melanocytes in tissues, a comparison of the variation of thermal energy is determined for different collections of melanocyte spatial distributions. This work was funded by NIH/NIGMS MBRS-RISE GM60655.

  15. First principles study of the ternary complex model of EL2 defect in GaAs saturable absorber.

    PubMed

    Li, Dechun; Yang, Ming; Cai, Yongqing; Zhao, Shengzhi; Feng, Yuanping

    2012-03-12

    First principles calculations are performed for the perfect GaAs crystal, the double Ga vacancies (VGa)₂, and the ternary complex defect (AsGaVAsVGa), using the state-of-the-art computational method with the Heyd-Scuseria-Ernzerhof (HSE) hybrid functional to correct the band gap and account for a proper description of the interaction between defects states and bulk states. Three shallow acceptor defect levels are found due to the creation of (VGa)₂ with nearest-neighbor As dangling bonds. However, for GaAs with the ternary complex defects (AsGaVAsVGa), the As antisite AsGa and the VAs'S nearest-neighbor Ga dangling bonds provoke several donor defect states. The lowest donor defect state locates at 0.85 eV below the bottom of conduction band, which is very close to the experimental observation of the EL2 defect level. In addition, structual evolution from (VGa)₂ defect to the ternary defect complex (AsGaVAsVGa) is simulated by ab initio molecular dynamic (MD) calculation at different temperatures. The MD results demonstrate that the ternary complex defect (AsGaVAsVGa) can be converted from the double Ga vacancies (VGa)₂ at room temperature, and it can exist stably at higher temperature. The present work is helpful to unravel the microstructure and the forming mechanism of the EL2 defect, to find out methods to improve the performance of the GaAs saturable absorber by changing the growth conditions of GaAs crystal.

  16. Water heat pipe blackbody as a reference spectral radiance source between 50°C and 250°C

    NASA Astrophysics Data System (ADS)

    Noorma, M.; Mekhontsev, S.; Khromchenko, V.; Litorja, M.; Cagran, C.; Zeng, J.; Hanssen, L.

    2006-04-01

    Realization of a radiometric temperature scale for near ambient temperatures with accuracy at the 20 to 50 mK level is crucial for a number of demanding military and commercial applications. In support of such measurements, radiation sources with high stability and spatial uniformity must be developed as reference and working standards. Traditionally, the temperature scale, maintained at the National Institute of Standards and Technology (NIST), relies on water bath and oil bath blackbodies in this temperature range. Recently, a water heat pipe blackbody was used at NIST as a spectral radiance source in a spectral emissivity measurement facility. Now a new, more versatile high emissivity water heat pipe blackbody was designed and characterized to be used as a reference radiance source for the radiometric temperature scale realization between 50 °C and 250 °C. Furthermore, it will serve as a reference source for the infrared spectral radiance measurements between 2.5 μm and 20 μm. The calculated spectral emissivity of the painted copper alloy cavity was verified by reflectance measurements using a CO II laser at 10.6 μm wavelength. The spatial thermal uniformity and stability of the blackbody were characterized. Two independent realizations of the radiometric temperature scale were compared in order to verify the accuracy of the scale. Radiance temperature, calculated from the cavity temperature measured with a calibrated PRT contact thermometer and from the emissivity of the cavity, was compared to the radiance temperature, directly measured with a reference pyrometer, which was calibrated with a set of fixed point blackbodies. The difference was found to be within measurement uncertainties.

  17. Evaluation of beta-absorbed fractions in a mouse model for 90Y, 188Re, 166Ho, 149Pm, 64Cu, and 177Lu radionuclides.

    PubMed

    Miller, William H; Hartmann-Siantar, Christine; Fisher, Darrell; Descalle, Marie-Anne; Daly, Tom; Lehmann, Joerg; Lewis, Michael R; Hoffman, Timothy; Smith, Jeff; Situ, Peter D; Volkert, Wynn A

    2005-08-01

    Several short-lived, high-energy beta emitters are being proposed as the radionuclide components for molecular- targeted potential cancer therapeutic agents. The laboratory mice used to determine the efficacy of these new agents have organs that are relatively small compared to the ranges of these high-energy particles. The dosimetry model developed by Hui et al. was extended to provide realistic beta-dose estimates for organs in mice that received therapeutic radiopharmaceuticals containing (90)Y, (188)Re, (166)Ho, (149)Pm, (64)Cu, and (177)Lu. Major organs in this model included the liver, spleen, kidneys, lungs, heart, stomach, small and large bowel, thyroid, pancreas, bone, marrow, carcass, and a 0.025-g tumor. The study as reported in this paper verifies their results for (90)Y and extends them by using their organ geometry factors combined with newly calculated organ self-absorbed fractions from PEREGRINE and MCNP. PEREGRINE and MCNP agree to within 8% for the worst-case organ with average differences (averaged over all organs) decreasing from 5% for (90)Y to 1% for (177)Lu. When used with typical biodistribution data, the three different models predict doses that are in agreement to within 5% for the worst-case organ. The beta-absorbed fractions and cross-organ-deposited energy provided in this paper can be used by researchers to predict mouse-organ doses and should contribute to an improved understanding of the relationship between dose and radiation toxicity in mouse models where use of these isotopes is favorable.

  18. Evaluation of Beta-Absorbed Fractions in a Mouse Model for 90Y, 188Re, 166Ho, 149Pm, 64Cu, and 177Lu Radionuclides

    SciTech Connect

    Miller, William H.; Hartmann-Siantar, Christine; Fisher, Darrell R.; Descalle, Marie-Anne; Daly, Tom; Lehmann, Joerg; Lewis, Michael R.; Hoffman, Timothy J.; Smith, Jeff; Situ, Peter D.; Volkert, Wynn A.

    2005-08-01

    Several short-lived, high-energy beta emitters are being proposed as the radionuclide components for molecular-targeted potential cancer therapeutic agents. The laboratory mice used to determine the efficacy of these new agents have organs that are relatively small compared to the ranges of these high-energy particles. The dosimetry model developed by Hui et al. was extended to provide realistic beta-dose estimates for organs in mice that received therapeutic radiopharmaceuticals containing 90Y, 188Re, 166Ho, 149Pm, 64Cu, and 177 Lu. Major organs in this model included the liver, spleen, kidneys, lungs, heart, stomach, small and large bowel, thyroid, pancreas, bone, marrow, carcass, and a 0.025-g tumor. The study as reported in this paper verifies their results for 90Y and extends them by using their organ geometry factors combined with newly calculated organ self-absorbed fractions from PEREGRINE and MCNP. PEREGRINE and MCNP agree to within 8% for the worst-case organ with average differences (averaged over all organs) decreasing from 5% for 90Y to 1% for 177Lu. When used with typical biodistribution data, the three different models predict doses that are in agreement to within 5% for the worst-case organ. The beta-absorbed fractions and cross-organ-deposited energy provided in this paper can be used by researchers to predict mouse-organ doses and should contribute to an improved understanding of the relationship between dose and radiation toxicity in mouse models where use of these isotopes is favorable.

  19. "Smart" Electromechanical Shock Absorber

    NASA Technical Reports Server (NTRS)

    Stokes, Lebarian; Glenn, Dean C.; Carroll, Monty B.

    1989-01-01

    Shock-absorbing apparatus includes electromechanical actuator and digital feedback control circuitry rather than springs and hydraulic damping as in conventional shock absorbers. Device not subject to leakage and requires little or no maintenance. Attenuator parameters adjusted in response to sensory feedback and predictive algorithms to obtain desired damping characteristic. Device programmed to decelerate slowly approaching vehicle or other large object according to prescribed damping characteristic.

  20. Truly Absorbed Microbial Protein Synthesis, Rumen Bypass Protein, Endogenous Protein, and Total Metabolizable Protein from Starchy and Protein-Rich Raw Materials: Model Comparison and Predictions.

    PubMed

    Parand, Ehsan; Vakili, Alireza; Mesgaran, Mohsen Danesh; van Duinkerken, Gert; Yu, Peiqiang

    2015-07-29

    This study was carried out to measure truly absorbed microbial protein synthesis, rumen bypass protein, and endogenous protein loss, as well as total metabolizable protein, from starchy and protein-rich raw feed materials with model comparisons. Predictions by the DVE2010 system as a more mechanistic model were compared with those of two other models, DVE1994 and NRC-2001, that are frequently used in common international feeding practice. DVE1994 predictions for intestinally digestible rumen undegradable protein (ARUP) for starchy concentrates were higher (27 vs 18 g/kg DM, p < 0.05, SEM = 1.2) than predictions by the NRC-2001, whereas there was no difference in predictions for ARUP from protein concentrates among the three models. DVE2010 and NRC-2001 had highest estimations of intestinally digestible microbial protein for starchy (92 g/kg DM in DVE2010 vs 46 g/kg DM in NRC-2001 and 67 g/kg DM in DVE1994, p < 0.05 SEM = 4) and protein concentrates (69 g/kg DM in NRC-2001 vs 31 g/kg DM in DVE1994 and 49 g/kg DM in DVE2010, p < 0.05 SEM = 4), respectively. Potential protein supplies predicted by tested models from starchy and protein concentrates are widely different, and comparable direct measurements are needed to evaluate the actual ability of different models to predict the potential protein supply to dairy cows from different feedstuffs.

  1. Experiments and Modeling of High Altitude Chemical Agent Release

    SciTech Connect

    Nakafuji, G.; Greenman, R.; Theofanous, T.

    2002-07-08

    Using ASCA data, we find, contrary to other researchers using ROSAT data, that the X-ray spectra of the VY Scl stars TT Ari and KR Aur are poorly fit by an absorbed blackbody model but are well fit by an absorbed thermal plasma model. The different conclusions about the nature of the X-ray spectrum of KR Aur may be due to differences in the accretion rate, since this Star was in a high optical state during the ROSAT observation, but in an intermediate optical state during the ASCA observation. TT Ari, on the other hand, was in a high optical state during both observations, so directly contradicts the hypothesis that the X-ray spectra of VY Sol stars in their high optical states are blackbodies. Instead, based on theoretical expectations and the ASCA, Chandra, and XMM spectra of other nonmagnetic cataclysmic variables, we believe that the X-ray spectra of VY Sol stars in their low and high optical states are due to hot thermal plasma in the boundary layer between the accretion disk and the surface of the white dwarf, and appeal to the acquisition of Chandra and XMM grating spectra to test this prediction.

  2. Spectrophotometry of Thin Films of Light-Absorbing Particles.

    PubMed

    Binks, Bernard P; Fletcher, Paul D I; Johnson, Andrew J; Marinopoulos, Ioannis; Crowther, Jonathan M; Thompson, Michael A

    2017-04-06

    Thin films of dispersions of light-absorbing solid particles or emulsions containing a light-absorbing solute all have a nonuniform distribution of light-absorbing species throughout the sample volume. This results in nonuniform light absorption over the illuminated area, which causes the optical absorbance, as measured using a conventional specular UV-vis spectrophotometer, to deviate from the Beer-Lambert relationship. We have developed a theoretical model to account for the absorbance properties of such films, which are shown to depend on the size and volume fraction of the light-absorbing particles plus other sample variables. We have compared model predictions with measured spectra for samples consisting of emulsions containing a dissolved light-absorbing solute. Using no adjustable parameters, the model successfully predicts the behavior of nonuniform, light-absorbing emulsion films with varying values of droplet size, volume fraction, and other parameters.

  3. USE OF A PHYSIOLOGICALLY-BASED PHARMACOKINETIC MODEL TO ESTIMATE ABSORBED CARBARYL DOSE IN CHILDREN AFTER TURF APPLICATION

    EPA Science Inventory

    A physiologically based pharmacokinetic (PBPK) model was developed to investigate exposure scenarios of children to carbaryl following turf application. Physiological, pharmacokinetic and pharmacodynamic parameters describing the fate and effects of carbaryl in rats were scaled ...

  4. Experimental study of the furnace effect with the copper point blackbody

    NASA Astrophysics Data System (ADS)

    Imbe, Masatoshi; Yamada, Yoshiro

    2016-12-01

    The furnace effect is a major uncertainty source in the realization of high-temperature fixed points in metal-carbon systems. The cause of this effect is as yet unexplained, and understanding it is a high-priority task for the inclusion of fixed points in future high-temperature metrology. In this paper, the furnace effect is studied experimentally and systematically with three furnaces, two cells, and two radiation thermometers. The copper point is chosen for the fixed point of investigation in order to eliminate the influence of the properties of the furnace. Correction for drift and the size-of-source effect of the thermometer is applied to achieve the required measurement accuracy. As a result, the furnace effect has been demonstrated quantitatively for the first time as the difference in radiance temperature of the same cell observed in different furnaces by the same thermometer. The experimental results show that it is related to the dimension of the furnace and the design of the fixed-point blackbody cell.

  5. Unidirectional perfect absorber

    PubMed Central

    Jin, L.; Wang, P.; Song, Z.

    2016-01-01

    This study proposes a unidirectional perfect absorber (UPA), which we realized with a two-arm Aharonov-Bohm interferometer, that consists of a dissipative resonator side-coupled to a uniform resonator array. The UPA has reflection-less full absorption on one direction, and reflectionless full transmission on the other, with an appropriate magnetic flux and coupling, detuning, and loss of the side-coupled resonator. The magnetic flux controls the transmission, the left transmission is larger for magnetic flux less than one-half flux quantum; and the right transmission is larger for magnetic flux between one-half and one flux quantum. Besides, a perfect absorber (PA) can be realized based on the UPA, in which light waves from both sides, with arbitrary superposition of the ampli- tude and phase, are perfectly absorbed. The UPA is expected to be useful in the design of novel optical devices. PMID:27615125

  6. Shock absorber servicing tool

    NASA Technical Reports Server (NTRS)

    Koepler, Jack L. (Inventor); Hill, Robert L. (Inventor)

    1981-01-01

    A tool to assist in the servicing of a shock absorber wherein the shock absorber is constructed of a pair of aligned gas and liquid filled chambers. Each of the chambers is separated by a movable separator member. Maximum efficiency of the shock absorber is achieved in the locating of a precise volume of gas within the gas chamber and a precise volume of liquid within the liquid chamber. The servicing tool of this invention employs a rod which is to connect with the separator and by observation of the position of the rod with respect to the gauge body, the location of the separator is ascertained even though it is not directly observable.

  7. Unidirectional perfect absorber

    NASA Astrophysics Data System (ADS)

    Jin, L.; Wang, P.; Song, Z.

    2016-09-01

    This study proposes a unidirectional perfect absorber (UPA), which we realized with a two-arm Aharonov-Bohm interferometer, that consists of a dissipative resonator side-coupled to a uniform resonator array. The UPA has reflection-less full absorption on one direction, and reflectionless full transmission on the other, with an appropriate magnetic flux and coupling, detuning, and loss of the side-coupled resonator. The magnetic flux controls the transmission, the left transmission is larger for magnetic flux less than one-half flux quantum; and the right transmission is larger for magnetic flux between one-half and one flux quantum. Besides, a perfect absorber (PA) can be realized based on the UPA, in which light waves from both sides, with arbitrary superposition of the ampli- tude and phase, are perfectly absorbed. The UPA is expected to be useful in the design of novel optical devices.

  8. OVI absorbers in SDSS spectra

    NASA Astrophysics Data System (ADS)

    Frank, Stephan

    with the ubiquitous Lya forest lines, and estimate the success rate of retrieving each individual candidate as a function of its redshift, the emission redshift of the quasar, the strength of the absorber and the measured S/N of the spectrum by modelling typical Ly forest spectra. These correction factors allow us to derive the 'incompleteness and S/N corrected' redshift number densities of O VI absorbers. We can place a secure lower limit for the contribution of O VI to the closure mass density at the redshifts probed here: O OV I (2.8 < z < 3.2) >= 1.9 × 10 - 8 h -1 . We show that the strong lines we probe account for over 65% of the mass in the O VI absorbers; the weak absorbers, while dominant in line number density, do not contribute significantly to the mass density. Making a conservative assumption about the ionisation fraction, [Special characters omitted.] , and adopting the Anders & Grevesse (1989) solar abundance values, we derive the mean metallicty of the gas probed in our search : z(2.8 < z < 3.2) >= 3.6 × 10 -4 h , in good agreement with other studies. These results demonstrate that large spectroscopic datasets such as SDSS can play an important role in QSO absorption line studies, in spite of the relatively low resolution. Lastly, we have performed a stacking analysis whereby we shift individual spectra back to the rest-frame of the absorber candidate, and derive a mean absorption spectrum for various subsamples. Besides further validating the reality of the absorbers themselves, i.e. ruling out spurious interlopers and other misclassifications, we can use these stacked spectra for a variety of purposes. First of all, we can judge the effects of additional cut criteria like a minimal strength for associated CIV absorption, and hence produce cleaner and better defined subsamples, increasing the strength of future proposals for high-resolution studies. Secondly, the stack itself contains valuable information about the gas probed in our search. We have

  9. Shock Absorbing System

    NASA Astrophysics Data System (ADS)

    1982-01-01

    A lightweight, inexpensive shock-absorbing system, developed by Langley Research Center 20 years ago, is now in service as safety device for an automated railway at Duke University Medical Center. The transportation system travels at about 25 miles per hour, carrying patients, visitors, staff and cargo. At the end of each guideway of the system are "frangible," (breakable) tube "buffers." If a slowing car fails to make a complete stop at the terminal, it would bump and shatter the tubes, absorbing energy that might otherwise jolt the passengers or damage the vehicle.

  10. An InGaAs detector based radiation thermometer and fixed-point blackbodies for temperature scale realization at NIM

    SciTech Connect

    Hao, X.; Yuan, Z.; Wang, J.; Lu, X.

    2013-09-11

    In this paper, we describe an InGaAs detector based radiation thermometer (IRT) and new design of fixed-point blackbodies, including Sn, Zn, Al and Cu, for the establishment of a temperature scale from 200 °C to 1085 °C at the National Institute of Metrology of China. The construction and calibration of the IRT with the four fixed-point blackbodies are described. Characteristics of the IRT, such as the size-of-source effect, the amplifier performance and its stability are determined. The design of the four fixed-points, with 10 mm diameter of aperture and 0.9999 emissivity, is described. The uncertainty of the scale realization is elaborated.

  11. An InGaAs detector based radiation thermometer and fixed-point blackbodies for temperature scale realization at NIM

    NASA Astrophysics Data System (ADS)

    Hao, X.; Yuan, Z.; Wang, J.; Lu, X.

    2013-09-01

    In this paper, we describe an InGaAs detector based radiation thermometer (IRT) and new design of fixed-point blackbodies, including Sn, Zn, Al and Cu, for the establishment of a temperature scale from 200 °C to 1085 °C at the National Institute of Metrology of China. The construction and calibration of the IRT with the four fixed-point blackbodies are described. Characteristics of the IRT, such as the size-of-source effect, the amplifier performance and its stability are determined. The design of the four fixed-points, with 10 mm diameter of aperture and 0.9999 emissivity, is described. The uncertainty of the scale realization is elaborated.

  12. High-Accuracy Measurement of the Blackbody Radiation Frequency Shift of the Ground-State Hyperfine Transition in Cs133

    NASA Astrophysics Data System (ADS)

    Jefferts, S. R.; Heavner, T. P.; Parker, T. E.; Shirley, J. H.; Donley, E. A.; Ashby, N.; Levi, F.; Calonico, D.; Costanzo, G. A.

    2014-02-01

    We report a high-accuracy direct measurement of the blackbody radiation shift of the Cs133 ground-state hyperfine transition. This frequency shift is one of the largest systematic frequency biases encountered in realizing the current definition of the International System of Units (SI) second. Uncertainty in the blackbody radiation frequency shift correction has led to its being the focus of intense theoretical effort by a variety of research groups. Our experimental measurement of the shift used three primary frequency standards operating at different temperatures. We achieved an uncertainty a factor of five smaller than the previous best direct measurement. These results tend to validate the claimed accuracy of the recently calculated values.

  13. A modal-based reduction method for sound absorbing porous materials in poro-acoustic finite element models.

    PubMed

    Rumpler, Romain; Deü, Jean-François; Göransson, Peter

    2012-11-01

    Structural-acoustic finite element models including three-dimensional (3D) modeling of porous media are generally computationally costly. While being the most commonly used predictive tool in the context of noise reduction applications, efficient solution strategies are required. In this work, an original modal reduction technique, involving real-valued modes computed from a classical eigenvalue solver is proposed to reduce the size of the problem associated with the porous media. In the form presented in this contribution, the method is suited for homogeneous porous layers. It is validated on a 1D poro-acoustic academic problem and tested for its performance on a 3D application, using a subdomain decomposition strategy. The performance of the proposed method is estimated in terms of degrees of freedom downsizing, computational time enhancement, as well as matrix sparsity of the reduced system.

  14. An iterative approach for modeling the interaction of a partial coherent light distribution with an absorbing photosensitive polymer

    NASA Astrophysics Data System (ADS)

    Heyvaert, S.; Meuret, Y.; Meulebroeck, W.; Thienpont, H.

    2012-06-01

    The propagation of coherent light through a heterogeneous medium is an often-encountered problem in optics. Analytical solutions, found by solving the appropriate differential equations, usually only exist for simplified and idealized situations limiting their accuracy and applicability. A widely used approach is the Beam Propagation Method in which the electric field is determined by solving the wave equation numerically, making the method time-consuming, a drawback exacerbated by the heterogeneity of the medium. In this work we propose an alternative approach which combines, in an iterative way, optical ray-tracing simulation in the software ASAP™ with numerical simulations in Matlab in order to model the change in light distribution in a medium with anisotropic absorption, exposed to partially coherent light with high irradiance. The medium under study is a photosensitive polymer in which photochemical reactions cause the local absorption to change as a function of the local light fluence. Under continuous illumination, this results in time-varying light distributions throughout the irradiance process. In our model the fluence-absorption interaction is modelled by splitting up each iteration step into two parts. In the first part the optical ray-tracing software determines the new light distribution in the medium using the absorption from the previous iteration step. In the second part, using the new light distribution, the new absorption coefficients are calculated and expressed as a set of polynomials. The evolution of the light distribution and absorption is presented and the change in total transmission is compared with experiments.

  15. Experimental validation of computational models for large-scale nonlinear ultrasound simulations in heterogeneous, absorbing fluid media

    NASA Astrophysics Data System (ADS)

    Martin, Elly; Treeby, Bradley E.

    2015-10-01

    To increase the effectiveness of high intensity focused ultrasound (HIFU) treatments, prediction of ultrasound propagation in biological tissues is essential, particularly where bones are present in the field. This requires complex full-wave computational models which account for nonlinearity, absorption, and heterogeneity. These models must be properly validated but there is a lack of analytical solutions which apply in these conditions. Experimental validation of the models is therefore essential. However, accurate measurement of HIFU fields is not trivial. Our aim is to establish rigorous methods for obtaining reference data sets with which to validate tissue realistic simulations of ultrasound propagation. Here, we present preliminary measurements which form an initial validation of simulations performed using the k-Wave MATLAB toolbox. Acoustic pressure was measured on a plane in the field of a focused ultrasound transducer in free field conditions to be used as a Dirichlet boundary condition for simulations. Rectangular and wedge shaped olive oil scatterers were placed in the field and further pressure measurements were made in the far field for comparison with simulations. Good qualitative agreement was observed between the measured and simulated nonlinear pressure fields.

  16. Determination of the 5d6s3D1 State Lifetime and Blackbody Radiation Clock Shift in Yb

    DTIC Science & Technology

    2012-08-03

    transition due to room temperature blackbody radiation is dominated by a static Stark effect , which was recently measured to high accuracy [J. A. Shennan et...Stark effect , which was recently measured to high accuracy [J. A. Sherman et al., Phys. Rev. Lett. 108, 153002 (2012)]. However, room temperature... effect , which was recently measured to high accuracy [J. A. Sherman et al., Phys. Rev. Lett. 108, 153002 (2012)]. However, room temperature

  17. Specific absorbed fractions from the image-based VIP-Man body model and EGS4-VLSI Monte Carlo code: internal electron emitters

    NASA Astrophysics Data System (ADS)

    Chao, T. C.; Xu, X. G.

    2001-04-01

    VIP-Man is a whole-body anatomical model newly developed at Rensselaer from the high-resolution colour images of the National Library of Medicine's Visible Human Project. This paper summarizes the use of VIP-Man and the Monte Carlo method to calculate specific absorbed fractions from internal electron emitters. A specially designed EGS4 user code, named EGS4-VLSI, was developed to use the extremely large number of image data contained in the VIP-Man. Monoenergetic and isotropic electron emitters with energies from 100 keV to 4 MeV are considered to be uniformly distributed in 26 organs. This paper presents, for the first time, results of internal electron exposures based on a realistic whole-body tomographic model. Because VIP-Man has many organs and tissues that were previously not well defined (or not available) in other models, the efforts at Rensselaer and elsewhere bring an unprecedented opportunity to significantly improve the internal dosimetry.

  18. Predicting the Dynamic Crushing Response of a Composite Honeycomb Energy Absorber Using Solid-Element-Based Models in LS-DYNA

    NASA Technical Reports Server (NTRS)

    Jackson, Karen E.

    2010-01-01

    This paper describes an analytical study that was performed as part of the development of an externally deployable energy absorber (DEA) concept. The concept consists of a composite honeycomb structure that can be stowed until needed to provide energy attenuation during a crash event, much like an external airbag system. One goal of the DEA development project was to generate a robust and reliable Finite Element Model (FEM) of the DEA that could be used to accurately predict its crush response under dynamic loading. The results of dynamic crush tests of 50-, 104-, and 68-cell DEA components are presented, and compared with simulation results from a solid-element FEM. Simulations of the FEM were performed in LS-DYNA(Registered TradeMark) to compare the capabilities of three different material models: MAT 63 (crushable foam), MAT 26 (honeycomb), and MAT 126 (modified honeycomb). These material models are evaluated to determine if they can be used to accurately predict both the uniform crushing and final compaction phases of the DEA for normal and off-axis loading conditions

  19. Design of a nonlinear torsional vibration absorber

    NASA Astrophysics Data System (ADS)

    Tahir, Ammaar Bin

    Tuned mass dampers (TMD) utilizing linear spring mechanisms to mitigate destructive vibrations are commonly used in practice. A TMD is usually tuned for a specific resonant frequency or an operating frequency of a system. Recently, nonlinear vibration absorbers attracted attention of researchers due to some potential advantages they possess over the TMDs. The nonlinear vibration absorber, or the nonlinear energy sink (NES), has an advantage of being effective over a broad range of excitation frequencies, which makes it more suitable for systems with several resonant frequencies, or for a system with varying excitation frequency. Vibration dissipation mechanism in an NES is passive and ensures that there is no energy backflow to the primary system. In this study, an experimental setup of a rotational system has been designed for validation of the concept of nonlinear torsional vibration absorber with geometrically induced cubic stiffness nonlinearity. Dimensions of the primary system have been optimized so as to get the first natural frequency of the system to be fairly low. This was done in order to excite the dynamic system for torsional vibration response by the available motor. Experiments have been performed to obtain the modal parameters of the system. Based on the obtained modal parameters, the design optimization of the nonlinear torsional vibration absorber was carried out using an equivalent 2-DOF modal model. The optimality criterion was chosen to be maximization of energy dissipation in the nonlinear absorber attached to the equivalent 2-DOF system. The optimized design parameters of the nonlinear absorber were tested on the original 5-DOF system numerically. A comparison was made between the performance of linear and nonlinear absorbers using the numerical models. The comparison showed the superiority of the nonlinear absorber over its linear counterpart for the given set of primary system parameters as the vibration energy dissipation in the former is

  20. Solar concentrator/absorber

    NASA Technical Reports Server (NTRS)

    Von Tiesenhausen, G. F.

    1976-01-01

    Collector/energy converter, consisting of dual-slope optical concentrator and counterflow thermal energy absorber, is attached to multiaxis support structure. Efficient over wide range of illumination levels, device may be used to generate high temperature steam, serve as solar powered dryer, or power absorption cycle cooler.

  1. Neutron Absorbing Alloys

    SciTech Connect

    Mizia, Ronald E.; Shaber, Eric L.; DuPont, John N.; Robino, Charles V.; Williams, David B.

    2004-05-04

    The present invention is drawn to new classes of advanced neutron absorbing structural materials for use in spent nuclear fuel applications requiring structural strength, weldability, and long term corrosion resistance. Particularly, an austenitic stainless steel alloy containing gadolinium and less than 5% of a ferrite content is disclosed. Additionally, a nickel-based alloy containing gadolinium and greater than 50% nickel is also disclosed.

  2. Shock Absorbing Helmets

    NASA Technical Reports Server (NTRS)

    1978-01-01

    This paper presents a description of helmets used by football players that offer three times the shock-absorbing capacity of earlier types. An interior padding for the helmets, composed of Temper Foam, first used by NASA's Ames Research Center in the design of aircraft seats is described.

  3. Radar Absorbing Materials for Cube Stealth Satellite

    NASA Astrophysics Data System (ADS)

    Micheli, D.; Pastore, R.; Vricella, A.; Marchetti, M.

    A Cube Stealth Satellite is proposed for potential applications in defense system. Particularly, the faces of the satellite exposed to the Earth are made of nanostructured materials able to absorb radar surveillance electromagnetic waves, conferring stealth capability to the cube satellite. Microwave absorbing and shielding material tiles are proposed using composite materials consisting in epoxy-resin and carbon nanotubes filler. The electric permittivity of the composite nanostructured materials is measured and discussed. Such data are used by the modeling algorithm to design the microwave absorbing and the shielding faces of the cube satellite. The electromagnetic modeling takes into account for several incidence angles (0-80°), extended frequency band (2-18 GHz), and for the minimization of the electromagnetic reflection coefficient. The evolutionary algorithm used for microwave layered microwave absorber modeling is the recently developed Winning Particle Optimization. The mathematical model of the absorbing structure is finally experimentally validated by comparing the electromagnetic simulation to the measurement of the manufactured radar absorber tile. Nanostructured composite materials manufacturing process and electromagnetic reflection measurements methods are described. Finally, a finite element method analysis of the electromagnetic scattering by cube stealth satellite is performed.

  4. All-in-one optical heater-thermometer nanoplatform operative from 300 to 2000 k based on Er(3+) emission and blackbody radiation.

    PubMed

    Debasu, Mengistie L; Ananias, Duarte; Pastoriza-Santos, Isabel; Liz-Marzán, Luis M; Rocha, J; Carlos, Luís D

    2013-09-20

    A single nanoplatform integrating laser-induced heat generation by gold nanoparticles and temperature sensing up to 2000 K via (Gd,Yb,Er)2 O3 nanorods is demonstrated, which presents considerable potential for nanoscale photonics and biomedicine. Blackbody emission is ascertained from the temperature increment with AuNP concentration, emission color coordinates as a function of the laser pump power, and Planck's law of blackbody radiation.

  5. Metasurface Broadband Solar Absorber

    PubMed Central

    Azad, Abul K.; Kort-Kamp, Wilton J. M.; Sykora, Milan; Weisse-Bernstein, Nina R.; Luk, Ting S.; Taylor, Antoinette J.; Dalvit, Diego A. R.; Chen, Hou-Tong

    2016-01-01

    We demonstrate a broadband, polarization independent, wide-angle absorber based on a metallic metasurface architecture, which accomplishes greater than 90% absorptance in the visible and near-infrared range of the solar spectrum, and exhibits low absorptivity (emissivity) at mid- and far-infrared wavelengths. The complex unit cell of the metasurface solar absorber consists of eight pairs of gold nano-resonators that are separated from a gold ground plane by a thin silicon dioxide spacer. Our experimental measurements reveal high-performance absorption over a wide range of incidence angles for both s- and p-polarizations. We also investigate numerically the frequency-dependent field and current distributions to elucidate how the absorption occurs within the metasurface structure. PMID:26828999

  6. Metasurface Broadband Solar Absorber

    DOE PAGES

    Azad, Abul K.; Kort-Kamp, Wilton J. M.; Sykora, Milan; ...

    2016-02-01

    Here, we demonstrate a broadband, polarization independent, wide-angle absorber based on a metallic metasurface architecture, which accomplishes greater than 90% absorptance in the visible and near-infrared range of the solar spectrum, and exhibits low absorptivity (emissivity) at mid- and far-infrared wavelengths. The complex unit cell of the metasurface solar absorber consists of eight pairs of gold nano-resonators that are separated from a gold ground plane by a thin silicon dioxide spacer. Moreover, our experimental measurements reveal high-performance absorption over a wide range of incidence angles for both s- and p-polarizations. We also investigate numerically the frequency-dependent field and current distributionsmore » to elucidate how the absorption occurs within the metasurface structure.« less

  7. Metasurface Broadband Solar Absorber

    SciTech Connect

    Azad, Abul K.; Kort-Kamp, Wilton J. M.; Sykora, Milan; Weisse-Bernstein, Nina R.; Luk, Ting S.; Taylor, Antoinette J.; Dalvit, Diego A. R.; Chen, Hou-Tong

    2016-02-01

    Here, we demonstrate a broadband, polarization independent, wide-angle absorber based on a metallic metasurface architecture, which accomplishes greater than 90% absorptance in the visible and near-infrared range of the solar spectrum, and exhibits low absorptivity (emissivity) at mid- and far-infrared wavelengths. The complex unit cell of the metasurface solar absorber consists of eight pairs of gold nano-resonators that are separated from a gold ground plane by a thin silicon dioxide spacer. Moreover, our experimental measurements reveal high-performance absorption over a wide range of incidence angles for both s- and p-polarizations. We also investigate numerically the frequency-dependent field and current distributions to elucidate how the absorption occurs within the metasurface structure.

  8. Comparison of mathematical models for red marrow and blood absorbed dose estimation in the radioiodine treatment of advanced differentiated thyroid carcinoma

    NASA Astrophysics Data System (ADS)

    Miranti, A.; Giostra, A.; Richetta, E.; Gino, E.; Pellerito, R. E.; Stasi, M.

    2015-02-01

    Metastatic and recurrent differentiated thyroid carcinoma is preferably treated with 131I, whose administered activity is limited by red marrow (RM) toxicity, originally correlated by Benua to a blood absorbed dose higher than 2 Gy. Afterward a variety of dosimetric approaches has been proposed. The aim of this work is to compare the results of the Benua formula with the ones of other three blood and RM absorbed dose formulae. Materials and methods have been borrowed by the dosimetric protocol of the Italian Internal Dosimetry group and adapted to the routine of our centre. Wilcoxon t-tests and percentage differences have been applied for comparison purposes. Results are significantly different (p < 0.05) from each other, with an average percentage difference between Benua versus other results of -22%. The dosimetric formula applied to determine blood or RM absorbed dose may contribute significantly to increase heterogeneity in absorbed dose and dose-response results. Standardization should be a major objective.

  9. Apollo couch energy absorbers

    NASA Technical Reports Server (NTRS)

    Wesselski, C. J.; Drexel, R. E.

    1972-01-01

    Load attenuators for the Apollo spacecraft crew couch and its potential applications are described. Energy absorption is achieved through friction and cyclic deformation of material. In one concept, energy absorption is accomplished by rolling a compressed ring of metal between two surfaces. In another concept, energy is absorbed by forcing a plastically deformed washer along a rod. Among the design problems that had to be solved were material selection, fatigue life, ring slippage, lubrication, and friction loading.

  10. Tear Production Rate in a Mouse Model of Dry Eye According to the Phenol Red Thread and Endodontic Absorbent Paper Point Tear Tests

    PubMed Central

    Kilic, Servet

    2016-01-01

    This study compared the endodontic absorbent paper point test (EAPTT) and the phenol red thread test (PRTT) for the assessment of tear production rate in a mouse model of dry eye. Fourteen BALB/c breed female mice were allocated into experimental and control groups of equal number. For 6 wk, the experimental group was kept in dry-eye cabinets, whereas the control group was kept in normal cages under ambient conditions. In both groups, the tear production rate was measured by using EAPTT and PRTT before the study, at study baseline, and at weeks 2, 4, and 6. Tear production at weeks 2, 4, and 6 differed significantly between groups and tests. Evaluating the groups independently in terms of the test technique revealed significant differences in tear production rate between the 2 groups at the same measurement times. Due to their persistent exposure to evaporative stress factors, the tear production rate of the mice in the dry-eye cabinet was consistently lower than that of controls. Unlike PRTT, EAPTT can be readily applied to the small globes of laboratory animals without the need for forceps, thus saving time and effort. In addition, EAPTT was practical and imposed no undue stress on the mice, due to the test material's firmer structure. Therefore, compared with PRTT, EAPTT is safer and more reliable for the diagnosis of dry-eye syndrome in mice. PMID:27780003

  11. Tear Production Rate in a Mouse Model of Dry Eye According to the Phenol Red Thread and Endodontic Absorbent Paper Point Tear Tests.

    PubMed

    Kilic, Servet; Kulualp, Kadri

    2016-01-01

    This study compared the endodontic absorbent paper point test (EAPTT) and the phenol red thread test (PRTT) for the assessment of tear production rate in a mouse model of dry eye. Fourteen BALB/c breed female mice were allocated into experimental and control groups of equal number. For 6 wk, the experimental group was kept in dry-eye cabinets, whereas the control group was kept in normal cages under ambient conditions. In both groups, the tear production rate was measured by using EAPTT and PRTT before the study, at study baseline, and at weeks 2, 4, and 6. Tear production at weeks 2, 4, and 6 differed significantly between groups and tests. Evaluating the groups independently in terms of the test technique revealed significant differences in tear production rate between the 2 groups at the same measurement times. Due to their persistent exposure to evaporative stress factors, the tear production rate of the mice in the dry-eye cabinet was consistently lower than that of controls. Unlike PRTT, EAPTT can be readily applied to the small globes of laboratory animals without the need for forceps, thus saving time and effort. In addition, EAPTT was practical and imposed no undue stress on the mice, due to the test material's firmer structure. Therefore, compared with PRTT, EAPTT is safer and more reliable for the diagnosis of dry-eye syndrome in mice.

  12. A review of measurement and modeling of Light-absorbing Particles in Snow and Ice and their climatic and hydrological impact

    NASA Astrophysics Data System (ADS)

    Qian, Y.; Doherty, S. J.; Lau, W. K. M.; Ming, J.; Wang, H.; Warren, S. G.; Yasunari, T. J.; Zhang, R.; Flanner, M.

    2015-12-01

    Light absorbing particles (LAP, e.g., black carbon, brown carbon, and dust) influence water and energy budgets of the atmosphere and snowpack in multiple ways. In addition to their effects associated with atmospheric heating by absorption of solar radiation and interactions with clouds, LAP in snow on land and ice can reduce the surface reflectance , which is likely to accelerate the snow aging process and further reduces snow albedo and increases the speed of snowpack melt. LAP in snow and ice (LAPSI) has been identified as one of major forcings affecting climate change, e.g. in the fourth and fifth assessment reports of IPCC. However, the uncertainty level in quantifying this effect remains very high. In this talk, we document various technical methods of measuring LAPSI and review the progress made in measuring the LAPSI in Arctic, Tibetan Plateau and other mid-latitude regions. We also report the progress in modeling the concentrations, albedo reduction, radiative forcing, and climatic and hydrological impact of LAPSI at global and regional scales. Finally we identify some research needs for reducing the uncertainties in the impact of LAPSI on global and regional climate and the hydrological cycle.

  13. Evaluation of blackbody radiation shift with temperature-associated fractional uncertainty at 10-18 level for 40Ca+ ion optical clock

    NASA Astrophysics Data System (ADS)

    Zhang, Ping; Cao, Jian; Shu, Hua-lin; Yuan, Jin-bo; Shang, Jun-juan; Cui, Kai-feng; Chao, Si-jia; Wang, Shao-mao; Liu, Dao-xin; Huang, Xue-ren

    2017-01-01

    In this paper, the blackbody radiation (BBR) temperature rise experienced by a 40Ca+ ion confined in a miniature Paul trap and its uncertainty have been evaluated via finite-element method (FEM) modelling. The FEM model was validated through comparisons with thermal camera measurements at several points on a dummy trap. Before the validation, the thermal camera was calibrated by using a PT1000 resistance thermometer. The input modelling parameters were analyzed carefully, and their contributions to the uncertainty of the trap environment temperature were evaluated using the validated FEM model. The result shows that the temperature rise experienced by the 40Ca+ ion is 1.72 K with an uncertainty of 0.46 K. It results in a contribution of 2.2 mHz to the systematic uncertainty of a 40Ca+ ion optical clock, corresponding to a fractional uncertainty 5.4 × 10-18. This is much smaller than the uncertainty caused by the BBR shift coefficient, which is evaluated to be 4.8 mHz and at the 10-17 level in fractional frequency units.

  14. Observations and model simulations of snow albedo reduction in seasonal snow due to insoluble light-absorbing particles during 2014 Chinese survey

    NASA Astrophysics Data System (ADS)

    Wang, Xin; Pu, Wei; Ren, Yong; Zhang, Xuelei; Zhang, Xueying; Shi, Jinsen; Jin, Hongchun; Dai, Mingkai; Chen, Quanliang

    2017-02-01

    A snow survey was carried out to collect 13 surface snow samples (10 for fresh snow, and 3 for aged snow) and 79 subsurface snow samples in seasonal snow at 13 sites across northeastern China in January 2014. A spectrophotometer combined with chemical analysis was used to quantify snow particulate absorption by insoluble light-absorbing particles (ILAPs, e.g., black carbon, BC; mineral dust, MD; and organic carbon, OC) in snow. Snow albedo was measured using a field spectroradiometer. A new radiative transfer model (Spectral Albedo Model for Dirty Snow, or SAMDS) was then developed to simulate the spectral albedo of snow based on the asymptotic radiative transfer theory. A comparison between SAMDS and an existing model - the Snow, Ice, and Aerosol Radiation (SNICAR) - indicates good agreements in the model-simulated spectral albedos of pure snow. However, the SNICAR model values tended to be slightly lower than those of SAMDS when BC and MD were considered. Given the measured BC, MD, and OC mixing ratios of 100-5000, 2000-6000, and 1000-30 000 ng g-1, respectively, in surface snow across northeastern China, the SAMDS model produced a snow albedo in the range of 0.95-0.75 for fresh snow at 550 nm, with a snow grain optical effective radius (Reff) of 100 µm. The snow albedo reduction due to spherical snow grains assumed to be aged snow is larger than fresh snow such as fractal snow grains and hexagonal plate or column snow grains associated with the increased BC in snow. For typical BC mixing ratios of 100 ng g-1 in remote areas and 3000 ng g-1 in heavy industrial areas across northern China, the snow albedo for internal mixing of BC and snow is lower by 0.005 and 0.036 than that of external mixing for hexagonal plate or column snow grains with Reff of 100 µm. These results also show that the simulated snow albedos by both SAMDS and SNICAR agree well with the observed values at low ILAP mixing ratios but tend to be higher than surface observations at high ILAP

  15. Absorber for terahertz radiation management

    SciTech Connect

    Biallas, George Herman; Apeldoorn, Cornelis; Williams, Gwyn P.; Benson, Stephen V.; Shinn, Michelle D.; Heckman, John D.

    2015-12-08

    A method and apparatus for minimizing the degradation of power in a free electron laser (FEL) generating terahertz (THz) radiation. The method includes inserting an absorber ring in the FEL beam path for absorbing any irregular THz radiation and thus minimizes the degradation of downstream optics and the resulting degradation of the FEL output power. The absorber ring includes an upstream side, a downstream side, and a plurality of wedges spaced radially around the absorber ring. The wedges form a scallop-like feature on the innermost edges of the absorber ring that acts as an apodizer, stopping diffractive focusing of the THz radiation that is not intercepted by the absorber. Spacing between the scallop-like features and the shape of the features approximates the Bartlett apodization function. The absorber ring provides a smooth intensity distribution, rather than one that is peaked on-center, thereby eliminating minor distortion downstream of the absorber.

  16. Corrosion resistant neutron absorbing coatings

    DOEpatents

    Choi, Jor-Shan [El Cerrito, CA; Farmer, Joseph C [Tracy, CA; Lee, Chuck K [Hayward, CA; Walker, Jeffrey [Gaithersburg, MD; Russell, Paige [Las Vegas, NV; Kirkwood, Jon [Saint Leonard, MD; Yang, Nancy [Lafayette, CA; Champagne, Victor [Oxford, PA

    2012-05-29

    A method of forming a corrosion resistant neutron absorbing coating comprising the steps of spray or deposition or sputtering or welding processing to form a composite material made of a spray or deposition or sputtering or welding material, and a neutron absorbing material. Also a corrosion resistant neutron absorbing coating comprising a composite material made of a spray or deposition or sputtering or welding material, and a neutron absorbing material.

  17. Corrosion resistant neutron absorbing coatings

    DOEpatents

    Choi, Jor-Shan; Farmer, Joseph C; Lee, Chuck K; Walker, Jeffrey; Russell, Paige; Kirkwood, Jon; Yang, Nancy; Champagne, Victor

    2013-11-12

    A method of forming a corrosion resistant neutron absorbing coating comprising the steps of spray or deposition or sputtering or welding processing to form a composite material made of a spray or deposition or sputtering or welding material, and a neutron absorbing material. Also a corrosion resistant neutron absorbing coating comprising a composite material made of a spray or deposition or sputtering or welding material, and a neutron absorbing material.

  18. New blackbody standard for the evaluation and calibration of tympanic ear thermometers at the NPL, United Kingdom

    NASA Astrophysics Data System (ADS)

    McEvoy, Helen C.; Simpson, Robert; Machin, Graham

    2004-04-01

    The use of infrared tympanic thermometers for monitoring patient health is widespread. However, studies into the performance of these thermometers have questioned their accuracy and repeatability. To give users confidence in these devices, and to provide credibility in the measurements, it is necessary for them to be tested using an accredited, standard blackbody source, with a calibration traceable to the International Temperature Scale of 1990 (ITS-90). To address this need the National Physical Laboratory (NPL), UK, has recently set up a primary ear thermometer calibration (PET-C) source for the evaluation and calibration of tympanic (ear) thermometers over the range from 15 °C to 45 °C. The overall uncertainty of the PET-C source is estimated to be +/- 0.04 °C at k = 2. The PET-C source meets the requirements of the European Standard EN 12470-5: 2003 Clinical thermometers. It consists of a high emissivity blackbody cavity immersed in a bath of stirred liquid. The temperature of the blackbody is determined using an ITS-90 calibrated platinum resistance thermometer inserted close to the rear of the cavity. The temperature stability and uniformity of the PET-C source was evaluated and its performance validated. This paper provides a description of the PET-C along with the results of the validation measurements. To further confirm the performance of the PET-C source it was compared to the standard ear thermometer calibration sources of the National Metrology Institute of Japan (NMIJ), Japan and the Physikalisch-Technische Bundesanstalt (PTB), Germany. The results of this comparison will also be briefly discussed. The PET-C source extends the capability for testing ear thermometers offered by the NPL body temperature fixed-point source, described previously. An update on the progress with the commercialisation of the fixed-point source will be given.

  19. Solar radiation absorbing material

    DOEpatents

    Googin, John M.; Schmitt, Charles R.; Schreyer, James M.; Whitehead, Harlan D.

    1977-01-01

    Solar energy absorbing means in solar collectors are provided by a solar selective carbon surface. A solar selective carbon surface is a microporous carbon surface having pores within the range of 0.2 to 2 micrometers. Such a surface is provided in a microporous carbon article by controlling the pore size. A thermally conductive substrate is provided with a solar selective surface by adhering an array of carbon particles in a suitable binder to the substrate, a majority of said particles having diameters within the range of about 0.2-10 microns.

  20. The 3K Blackbody Radiation, 'Stored' & 'Frozen' Light, 'Viscous Optical Molasses' as Effects of the Electron Positron Lattice (EPOLA) Structure of Our "Vacuum" Space

    NASA Astrophysics Data System (ADS)

    Simhony, Menahem

    2002-05-01

    In the EPOLA model of space [1] the mysterious 3K blackbody radiation of the sky is due to random thermal vibrations of the electrons and positrons, bound in the epola. They also cause the zero-point motion of helium atoms, a Brownian Motion analog. The temperature T of our epola region is therefore 3K. In space regions with more hot stars, more nuclear activity, T is higher and they may create the mystery of gray matter. Epola regions below 3K are observed as mysterious dark matter. The gray and dark matter regions are considered to constitute 90 percent of the mass of the universe. The 1997 Nobel Prize winners' "Optical Molasses" at micro-K T's are also explained by the epola model, as well as the 'stored', 'frozen' light effects, observed in 1999-2001. References: 1. M.Simhony, Invitation to the Natural Physics of Matter, Space, and Radiation, World Scientific, 1994 (292 pp), ISBN 981-02-1649-1. See the website: www.word1.co.il/physics .

  1. Liquid Cryogen Absorber for MICE

    SciTech Connect

    Baynham, D.E.; Bish, P.; Bradshaw, T.W.; Cummings, M.A.; Green,M.A.; Ishimoto, S.; Ivaniouchenkov, I.; Lau, W.; Yang, S.Q.; Zisman, M.S.

    2005-08-20

    The Muon Ionization Cooling Experiment (MICE) will test ionization cooling of muons. In order to have effective ionization cooling, one must use an absorber that is made from a low-z material. The most effective low z materials for ionization cooling are hydrogen, helium, lithium hydride, lithium and beryllium, in that order. In order to measure the effect of material on cooling, several absorber materials must be used. This report describes a liquid-hydrogen absorber that is within a pair of superconducting focusing solenoids. The absorber must also be suitable for use with liquid helium. The following absorber components are discussed in this report; the absorber body, its heat exchanger, the hydrogen system, and the hydrogen safety. Absorber cooling and the thin windows are not discussed here.

  2. Laser-trapping of {sup 225}Ra and {sup 226}Ra with repumping by room-temperature blackbody radiation.

    SciTech Connect

    Guest, J. R.; Scielzo, N. D.; Ahmad, I.; Bailey, K.; Greene, J. P.; Holt, R. J.; Lu, Z.-T.; O'Connor, T. P.; Potterveld, D. H.; Physics; Enrico Fermi Inst.; Univ. of Chicago

    2007-02-27

    We have demonstrated Zeeman slowing and capture of neutral {sup 225}Ra and {sup 226}Ra atoms in a magneto-optical trap. The intercombination transition {sup 1}S{sub 0} {yields} {sup 3}P{sub 1} is the only quasicycling transition in radium and was used for laser-cooling and trapping. Repumping along the {sup 3}D{sub 1} {yields} {sup 1}P{sub 1} transition extended the lifetime of the trap from milliseconds to seconds. Room-temperature blackbody radiation was demonstrated to provide repumping from the metastable {sup 3}P{sub 0} level. We measured the isotope shift and hyperfine splittings on the {sup 3}D{sub 1} {yields} {sup 1}P{sub 1} transition with the laser-cooled atoms, and set a limit on the lifetime of the {sup 3}D{sub 1} level based on the measured blackbody repumping rate. Laser-cooled and trapped radium is an attractive system for studying fundamental symmetries.

  3. Radiative heat transfer exceeding the blackbody limit between macroscale planar surfaces separated by a nanosize vacuum gap

    PubMed Central

    Bernardi, Michael P.; Milovich, Daniel; Francoeur, Mathieu

    2016-01-01

    Using Rytov's fluctuational electrodynamics framework, Polder and Van Hove predicted that radiative heat transfer between planar surfaces separated by a vacuum gap smaller than the thermal wavelength exceeds the blackbody limit due to tunnelling of evanescent modes. This finding has led to the conceptualization of systems capitalizing on evanescent modes such as thermophotovoltaic converters and thermal rectifiers. Their development is, however, limited by the lack of devices enabling radiative transfer between macroscale planar surfaces separated by a nanosize vacuum gap. Here we measure radiative heat transfer for large temperature differences (∼120 K) using a custom-fabricated device in which the gap separating two 5 × 5 mm2 intrinsic silicon planar surfaces is modulated from 3,500 to 150 nm. A substantial enhancement over the blackbody limit by a factor of 8.4 is reported for a 150-nm-thick gap. Our device paves the way for the establishment of novel evanescent wave-based systems. PMID:27682992

  4. Warm Absorber Diagnostics of AGN Dynamics

    NASA Astrophysics Data System (ADS)

    Kallman, Timothy

    Warm absorbers and related phenomena are observable manifestations of outflows or winds from active galactic nuclei (AGN) that have great potential value. Understanding AGN outflows is important for explaining the mass budgets of the central accreting black hole, and also for understanding feedback and the apparent co-evolution of black holes and their host galaxies. In the X-ray band warm absorbers are observed as photoelectric absorption and resonance line scattering features in the 0.5-10 keV energy band; the UV band also shows resonance line absorption. Warm absorbers are common in low luminosity AGN and they have been extensively studied observationally. They may play an important role in AGN feedback, regulating the net accretion onto the black hole and providing mechanical energy to the surroundings. However, fundamental properties of the warm absorbers are not known: What is the mechanism which drives the outflow?; what is the gas density in the flow and the geometrical distribution of the outflow?; what is the explanation for the apparent relation between warm absorbers and the surprising quasi-relativistic 'ultrafast outflows' (UFOs)? We propose a focused set of model calculations that are aimed at synthesizing observable properties of warm absorber flows and associated quantities. These will be used to explore various scenarios for warm absorber dynamics in order to answer the questions in the previous paragraph. The guiding principle will be to examine as wide a range as possible of warm absorber driving mechanisms, geometry and other properties, but with as careful consideration as possible to physical consistency. We will build on our previous work, which was a systematic campaign for testing important class of scenarios for driving the outflows. We have developed a set of tools that are unique and well suited for dynamical calculations including radiation in this context. We also have state-of-the-art tools for generating synthetic spectra, which are

  5. Dual broadband metamaterial absorber.

    PubMed

    Kim, Young Ju; Yoo, Young Joon; Kim, Ki Won; Rhee, Joo Yull; Kim, Yong Hwan; Lee, YoungPak

    2015-02-23

    We propose polarization-independent and dual-broadband metamaterial absorbers at microwave frequencies. This is a periodic meta-atom array consisting of metal-dielectric-multilayer truncated cones. We demonstrate not only one broadband absorption from the fundamental magnetic resonances but additional broadband absorption in high-frequency range using the third-harmonic resonance, by both simulation and experiment. In simulation, the absorption was over 90% in 3.93-6.05 GHz, and 11.64-14.55 GHz. The corresponding experimental absorption bands over 90% were 3.88-6.08 GHz, 9.95-10.46 GHz and 11.86-13.84 GHz, respectively. The origin of absorption bands was elucidated. Furthermore, it is independent of polarization angle owing to the multilayered circular structures. The design is scalable to smaller size for the infrared and the visible ranges.

  6. Electrochemically regenerable carbon dioxide absorber

    NASA Technical Reports Server (NTRS)

    Woods, R. R.; Marshall, R. D.; Schubert, F. H.; Heppner, D. B.

    1979-01-01

    Preliminary designs were generated for two electrochemically regenerable carbon dioxide absorber concepts. Initially, an electrochemically regenerable absorption bed concept was designed. This concept incorporated the required electrochemical regeneration components in the absorber design, permitting the absorbent to be regenerated within the absorption bed. This hardware was identified as the electrochemical absorber hardware. The second hardware concept separated the functional components of the regeneration and absorption process. This design approach minimized the extravehicular activity component volume by eliminating regeneration hardware components within the absorber. The electrochemical absorber hardware was extensively characterized for major operating parameters such as inlet carbon dioxide partial pressure, process air flow rate, operational pressure, inlet relative humidity, regeneration current density and absorption/regeneration cycle endurance testing.

  7. Broadband patterned magnetic microwave absorber

    SciTech Connect

    Li, Wei; Wu, Tianlong; Wang, Wei; Guan, Jianguo; Zhai, Pengcheng

    2014-07-28

    It is a tough task to greatly improve the working bandwidth for the traditional flat microwave absorbers because of the restriction of available material parameters. In this work, a simple patterning method is proposed to drastically broaden the absorption bandwidth of a conventional magnetic absorber. As a demonstration, an ultra-broadband microwave absorber with more than 90% absorption in the frequency range of 4–40 GHz is designed and experimentally realized, which has a thin thickness of 3.7 mm and a light weight equivalent to a 2-mm-thick flat absorber. In such a patterned absorber, the broadband strong absorption is mainly originated from the simultaneous incorporation of multiple λ/4 resonances and edge diffraction effects. This work provides a facile route to greatly extend the microwave absorption bandwidth for the currently available absorbing materials.

  8. Liquid Hydrogen Absorber for MICE

    SciTech Connect

    Ishimoto, S.; Suzuki, S.; Yoshida, M.; Green, Michael A.; Kuno, Y.; Lau, Wing

    2010-05-30

    Liquid hydrogen absorbers for the Muon Ionization Cooling Experiment (MICE) have been developed, and the first absorber has been tested at KEK. In the preliminary test at KEK we have successfully filled the absorber with {approx}2 liters of liquid hydrogen. The measured hydrogen condensation speed was 2.5 liters/day at 1.0 bar. No hydrogen leakage to vacuum was found between 300 K and 20 K. The MICE experiment includes three AFC (absorber focusing coil) modules, each containing a 21 liter liquid hydrogen absorber made of aluminum. The AFC module has safety windows to separate its vacuum from that of neighboring modules. Liquid hydrogen is supplied from a cryocooler with cooling power 1.5 W at 4.2 K. The first absorber will be assembled in the AFC module and installed in MICE at RAL.

  9. Evaluation of the absorption line blackbody distribution function of CO2 and H2O using the proper orthogonal decomposition and hyperbolic correlations

    NASA Astrophysics Data System (ADS)

    Liu, F.; Chu, H.; Zhou, H.; Smallwood, G. J.

    2013-10-01

    Databases of the absorption line blackbody distribution function (ALBDF) of CO2 and H2O were generated over a wide range of gas and blackbody temperatures and the full range of gas concentration from line-by-line (LBL) calculations using the latest version of HITEMP. Proper orthogonal decomposition (POD) and the hyperbolic correlations (HC) were then used for rapid calculation the ALBDF value at an arbitrary combination of gas and blackbody temperatures and gas concentration. A novel hyperbolic correlation for H2O was proposed to fully account for the self-broadening effect. The accuracy of POD and the HC was evaluated by comparing the ALBDF values and the total gas emissivities from these two approximate methods at several selected conditions against those from LBL calculations. POD is significantly more accurate than HC at essentially no extra computational costs.

  10. High bioavailablilty iron maize (Zea mays L.) developed through molecular breeding provides more absorbable iron in vitro (Caco-2 model) and in vivo (Gallus gallus)

    PubMed Central

    2013-01-01

    Background Iron (Fe) deficiency is the most common micronutrient deficiency worldwide. Iron biofortification is a preventative strategy that alleviates Fe deficiency by improving the amount of absorbable Fe in crops. In the present study, we used an in vitro digestion/Caco 2 cell culture model as the guiding tool for breeding and development of two maize (Zea mays L.) lines with contrasting Fe bioavailability (ie. Low and High). Our objective was to confirm and validate the in vitro results and approach. Also, to compare the capacities of our two maize hybrid varieties to deliver Fe for hemoglobin (Hb) synthesis and to improve the Fe status of Fe deficient broiler chickens. Methods We compared the Fe-bioavailability between these two maize varieties with the presence or absence of added Fe in the maize based-diets. Diets were made with 75% (w/w) maize of either low or high Fe-bioavailability maize, with or without Fe (ferric citrate). Chicks (Gallus gallus) were fed the diets for 6 wk. Hb, liver ferritin and Fe related transporter/enzyme gene-expression were measured. Hemoglobin maintenance efficiency (HME) and total body Hb Fe values were used to estimate Fe bioavailability from the diets. Results DMT-1, DcytB and ferroportin expressions were higher (P < 0.05) in the "Low Fe" group than in the "High Fe" group (no added Fe), indicating lower Fe status and adaptation to less Fe-bioavailability. At times, Hb concentrations (d 21,28,35), HME (d 21), Hb-Fe (as from d 14) and liver ferritin were higher in the "High Fe" than in the "Low Fe" groups (P < 0.05), indicating greater Fe absorption from the diet and improved Fe status. Conclusions We conclude that the High Fe-bioavailability maize contains more bioavailable Fe than the Low Fe-bioavailability maize, presumably due to a more favorable matrix for absorption. Maize shows promise for Fe biofortification; therefore, human trials should be conducted to determine the efficacy of consuming the high bioavailable

  11. Ferrite HOM Absorber for the RHIC ERL

    SciTech Connect

    Hahn,H.; Choi, E.M.; Hammons, L.

    2008-10-01

    A superconducting Energy Recovery Linac is under construction at Brookhaven National Laboratory to serve as test bed for RHIC upgrades. The damping of higher-order modes in the superconducting five-cell cavity for the Energy-Recovery linac at RHIC is performed exclusively by two ferrite absorbers. The ferrite properties have been measured in ferrite-loaded pill box cavities resulting in the permeability values given by a first-order Debye model for the tiled absorber structure and an equivalent permeability value for computer simulations with solid ring dampers. Measured and simulated results for the higher-order modes in the prototype copper cavity are discussed. First room-temperature measurements of the finished niobium cavity are presented which confirm the effective damping of higher-order modes in the ERL. by the ferrite absorbers.

  12. Absorber topography dependence of phase edge effects

    NASA Astrophysics Data System (ADS)

    Shanker, Aamod; Sczyrba, Martin; Connolly, Brid; Waller, Laura; Neureuther, Andy

    2015-10-01

    Mask topography contributes to phase at the wafer plane, even for OMOG binary masks currently in use at the 22nm node in deep UV (193nm) lithography. Here, numerical experiments with rigorous FDTD simulation are used to study the impact of mask 3D effects on aerial imaging, by varying the height of the absorber stack and its sidewall angle. Using a thin mask boundary layer model to fit to rigorous simulations it is seen that increasing the absorber thickness, and hence the phase through the middle of a feature (bulk phase) monotonically changes the wafer-plane phase. Absorber height also influences best focus, revealed by an up/down shift in the Bossung plot (linewidth vs. defocus). Bossung plot tilt, however, responsible for process window variability at the wafer, is insensitive to changes in the absorber height (and hence also the bulk phase). It is seen to depend instead on EM edge diffraction from the thick mask edge (edge phase), but stays constant for variations in mask thickness within a 10% range. Both bulk phase and edge phase are also independent of sidewall angle fluctuation, which is seen to linearly affect the CD at the wafer, but does not alter wafer phase or the defocus process window. Notably, as mask topography varies, the effect of edge phase can be replicated by a thin mask model with 8nm wide boundary layers, irrespective of absorber height or sidewall angle. The conclusions are validated with measurements on phase shifting masks having different topographic parameters, confirming the strong dependence of phase variations at the wafer on bulk phase of the mask absorber.

  13. Polarization independent broadband metamaterial absorber based on tapered helical structure

    NASA Astrophysics Data System (ADS)

    Agarwal, Sajal; Prajapati, Y. K.; Singh, V.; Saini, J. P.

    2015-12-01

    This communication presents a tapered helical structure as absorber, made of unconventional material i.e. metamaterial. Modeling, analytical study and the optimization of the absorber have been done. Quad helical optimized structure gives almost unity absorption at 499 nm wavelength and gives the absorption more than 75% from 300 nm to 1650 nm which is a very wide operating region with, average absorbance of 91.32%. Whereas, triple helical structure gives 85% average absorbance with the operating range from 300 nm to 1350 nm. Also, it is analyzed that the presented structures are polarization independent and broadband. Comparison of the proposed quad helical absorber with the existing metamaterial absorbers is done and found it is most eligible.

  14. Optimal active vibration absorber: Design and experimental results

    NASA Technical Reports Server (NTRS)

    Lee-Glauser, Gina; Juang, Jer-Nan; Sulla, Jeffrey L.

    1992-01-01

    An optimal active vibration absorber can provide guaranteed closed-loop stability and control for large flexible space structures with collocated sensors/actuators. The active vibration absorber is a second-order dynamic system which is designed to suppress any unwanted structural vibration. This can be designed with minimum knowledge of the controlled system. Two methods for optimizing the active vibration absorber parameters are illustrated: minimum resonant amplitude and frequency matched active controllers. The Controls-Structures Interaction Phase-1 Evolutionary Model at NASA LaRC is used to demonstrate the effectiveness of the active vibration absorber for vibration suppression. Performance is compared numerically and experimentally using acceleration feedback.

  15. Aether Drift and the isotropy of the universe: A measurement of anisotropes in the primordial black-body radiation

    NASA Technical Reports Server (NTRS)

    Smoot, G. F.

    1981-01-01

    Large-angular-scale anisotropies in the 3 K primordial black-body radiation were detected and mapped with a sensitivity of 2 x to the minus 4 power K and an angular resolution of about 10 deg. The motion of the Earth with respect to the distant matter of the Universe ("Aether Drift") was measured and the homogeneity and isotropy of the Universe (the "Cosmological Principle") was probed. The experiment uses two Dicke radiometers, one at 33 GHz to detect the cosmic anisotropy, and one at 54 GHz to detect anisotropies in the residual oxygen above the detectors. The system was installed in the NASA-Ames Earth survey aircraft (U-2), and operated successfully in a series of flights in both the Northern and Southern Hemispheres. Data taking and analysis to measure the anisotropy were successful.

  16. Measurement of the blackbody radiation shift of the {sup 133}Cs hyperfine transition in an atomic fountain

    SciTech Connect

    Levi, Filippo; Calonico, Davide; Lorini, Luca; Micalizio, Salvatore; Godone, Aldo

    2004-09-01

    We used a Cs fountain to measure the Stark shift of the ground-state hyperfine transition frequency in cesium (9.2 GHz) due to the electric field of the blackbody radiation. The relative shift at 300 K deduced from our measurements, including the leading and the second-order term in temperature, is (-1.45{+-}0.09)x10{sup -14} and agrees with our recent theoretical evaluation (-1.51{+-}0.07)x10{sup -14} [Micalizio et al. Phys. Rev. A 69, 053401 (2004)]. These values differ from that currently used (-1.735{+-}0.003)x10{sup -14}, with significant implications on frequency standards accuracy, on clocks comparison and on a variety of high-precision physics tests, such as the time stability of fundamental constants.

  17. Analytic evaluation of the weighting functions for remote sensing of blackbody planetary atmospheres : the case of limb viewing geometry

    NASA Technical Reports Server (NTRS)

    Ustinov, Eugene A.

    2006-01-01

    In a recent publication (Ustinov, 2002), we proposed an analytic approach to evaluation of radiative and geophysical weighting functions for remote sensing of a blackbody planetary atmosphere, based on general linearization approach applied to the case of nadir viewing geometry. In this presentation, the general linearization approach is applied to the limb viewing geometry. The expressions, similar to those obtained in (Ustinov, 2002), are obtained for weighting functions with respect to the distance along the line of sight. Further on, these expressions are converted to the expressions for weighting functions with respect to the vertical coordinate in the atmosphere. Finally, the numerical representation of weighting functions in the form of matrices of partial derivatives of grid limb radiances with respect to the grid values of atmospheric parameters is used for a convolution with the finite field of view of the instrument.

  18. Multipolar theory of blackbody radiation shift of atomic energy levels and its implications for optical lattice clocks

    SciTech Connect

    Porsev, Sergey G.; Derevianko, Andrei

    2006-08-15

    Blackbody radiation (BBR) shifts of the {sup 3}P{sub 0}-{sup 1}S{sub 0} clock transition in the divalent atoms Mg, Ca, Sr, and Yb are evaluated. The dominant electric-dipole contributions are computed using accurate relativistic many-body techniques of atomic structure. At room temperatures, the resulting uncertainties in the E1 BBR shifts are large and substantially affect the projected 10{sup -18} fractional accuracy of the optical-lattice-based clocks. A peculiarity of these clocks is that the characteristic BBR wavelength is comparable to the {sup 3}P fine-structure intervals. To evaluate relevant M1 and E2 contributions, a theory of multipolar BBR shifts is developed. The resulting corrections, although presently masked by the uncertainties in the E1 contribution, are required at the 10{sup -18} accuracy goal.

  19. Aether drift and the isotropy of the universe: a measurement of anisotropies in the primordial black-body radiation

    NASA Technical Reports Server (NTRS)

    Muller, R. A.

    1979-01-01

    This experiment detected and mapped large-angular-scale anisotropies in the 3 K primordial black-body radiation with a sensitivity of 2x.0001k and an angular resolution of about 10 degs. It measured the motion of the Earth with respect to the distant matter of the Universe (Aether Drift), and probed the homogeneity and isotropy of the Universe (the Cosmological Principle). The experiment used two Dicke radiometers, one at 33 GHz to detect the cosmic anisotropy, and one at 54 GHz to detect anisotropies in the residual oxygen above the detectors. The system was installed in the NASA-Ames Earth Survey Aircraft (U-2), and operated successfully in a series of flights.

  20. Energy absorber for the CETA

    NASA Technical Reports Server (NTRS)

    Wesselski, Clarence J.

    1994-01-01

    The energy absorber that was developed for the CETA (Crew Equipment and Translation Aid) on Space Station Freedom is a metal on metal frictional type and has a load regulating feature that prevents excessive stroking loads from occurring while in operation. This paper highlights some of the design and operating aspects and the testing of this energy absorber.

  1. Improvement Of The Helmholtz Absorber

    NASA Technical Reports Server (NTRS)

    Morrow, Duane L.

    1992-01-01

    Helmholtz-resonator system improved to enable it to absorb sound at more than one frequency without appreciable loss of effectiveness at primary frequency. Addition of annular cavities enables absorption of sound at harmonic frequencies in addition to primary frequency. Improved absorber designed for use on structures of high transmission loss. Applied to such machines as fixed-speed engines and fans.

  2. Metal-shearing energy absorber

    NASA Technical Reports Server (NTRS)

    Fay, R. J.; Wittrock, E. P.

    1971-01-01

    Device, consisting of tongue of thin aluminum alloy strip, pull tab, slotted steel plate which serves as cutter, and steel buckle, absorbs mechanical energy when its ends are subjected to tensile loading. Device is applicable as auxiliary shock absorbing anchor for automobile and airplane safety belts.

  3. Leaf absorbance and photosynthesis

    NASA Technical Reports Server (NTRS)

    Schurer, Kees

    1994-01-01

    The absorption spectrum of a leaf is often thought to contain some clues to the photosynthetic action spectrum of chlorophyll. Of course, absorption of photons is needed for photosynthesis, but the reverse, photosynthesis when there is absorption, is not necessarily true. As a check on the existence of absorption limits we measured spectra for a few different leaves. Two techniques for measuring absorption have been used, viz. the separate determination of the diffuse reflectance and the diffuse transmittance with the leaf at a port of an integrating sphere and the direct determination of the non-absorbed fraction with the leaf in the sphere. In a cross-check both methods yielded the same results for the absorption spectrum. The spectrum of a Fuchsia leaf, covering the short-wave region from 350 to 2500 nm, shows a high absorption in UV, blue and red, the well known dip in the green and a steep fall-off at 700 nm. Absorption drops to virtually zero in the near infrared, with subsequent absorptions, corresponding to the water absorption bands. In more detailed spectra, taken at 5 nm intervals with a 5 nm bandwidth, differences in chlorophyll content show in the different depths of the dip around 550 nm and in a small shift of the absorption edge at 700 nm. Spectra for Geranium (Pelargonium zonale) and Hibiscus (with a higher chlorophyll content) show that the upper limit for photosynthesis can not be much above 700 nm. No evidence, however, is to be seen of a lower limit for photosynthesis and, in fact, some experiments down to 300 nm still did not show a decrease of the absorption although it is well recognized that no photosynthesis results with 300 nm wavelengths.

  4. An Absorbing Look at Terry-Cloth Towels

    ERIC Educational Resources Information Center

    Moyer, Richard; Everett, Susan

    2010-01-01

    This article describes a lesson where students explore the absorbency of several towels with different weaves and weights. The lesson follows the 5E learning-cycle model and incorporates engineering in the sense of product testing with a focus on the relationship between the weave of a towel and its absorbency. The National Science Education…

  5. Absorbent product to absorb fluids. [for collection of human wastes

    NASA Technical Reports Server (NTRS)

    Dawn, F. S.; Correale, J. V. (Inventor)

    1982-01-01

    A multi-layer absorbent product for use in contact with the skin to absorb fluids is discussed. The product utilizes a water pervious facing layer for contacting the skin, overlayed by a first fibrous wicking layer, the wicking layer preferably being of the one-way variety in which fluid or liquid is moved away from the facing layer. The product further includes a first container section defined by inner and outer layer of a water pervious wicking material between which is disposed a first absorbent mass. A second container section defined by inner and outer layers between which is disposed a second absorbent mass and a liquid impermeable/gas permeable layer. Spacesuit applications are discussed.

  6. Fault Detection for Automotive Shock Absorber

    NASA Astrophysics Data System (ADS)

    Hernandez-Alcantara, Diana; Morales-Menendez, Ruben; Amezquita-Brooks, Luis

    2015-11-01

    Fault detection for automotive semi-active shock absorbers is a challenge due to the non-linear dynamics and the strong influence of the disturbances such as the road profile. First obstacle for this task, is the modeling of the fault, which has been shown to be of multiplicative nature. Many of the most widespread fault detection schemes consider additive faults. Two model-based fault algorithms for semiactive shock absorber are compared: an observer-based approach and a parameter identification approach. The performance of these schemes is validated and compared using a commercial vehicle model that was experimentally validated. Early results shows that a parameter identification approach is more accurate, whereas an observer-based approach is less sensible to parametric uncertainty.

  7. An introduction to absorbent dressings.

    PubMed

    Jones, Menna Lloyd

    2014-12-01

    Exudate bathes the wound bed with a serous fluid that contains essential components that promote wound healing. However, excess exudate is often seen as a challenge for clinicians. Absorbent dressings are often used to aid in the management of exudate, with the aim of providing a moist but unmacerated environment. With so many different types of absorbent dressings available today-alongside making a holistic assessment-it is essential that clinicians also have the knowledge and skill to select the most appropriate absorbent dressing for a given patient.

  8. Self-Regulating Shock Absorber

    NASA Technical Reports Server (NTRS)

    Wesselski, Clarence J.

    1995-01-01

    Mechanical shock absorber keeps frictional damping force within tolerable limit. Its damping force does not increase with coefficient of friction between energy-absorbing components; rather, frictional damping force varies only slightly. Relatively insensitive to manufacturing variations and environmental conditions altering friction. Does not exhibit high breakaway friction and consequent sharp increase followed by sharp decrease in damping force at beginning of stroking. Damping force in absorber does not vary appreciably with speed of stroking. In addition, not vulnerable to leakage of hydraulic fluid.

  9. Cu(In,Ga)Se2 absorber thinning and the homo-interface model: Influence of Mo back contact and 3-stage process on device characteristics

    NASA Astrophysics Data System (ADS)

    Leonard, E.; Arzel, L.; Tomassini, M.; Zabierowski, P.; Fuertes Marrón, D.; Barreau, N.

    2014-08-01

    Thinning the absorber layer is one of the possibilities envisaged to further decrease the production costs of Cu(In,Ga)Se2 (CIGSe) thin films solar cell technology. In the present study, the electronic transport in submicron CIGSe-based devices has been investigated and compared to that of standard devices. It is observed that when the absorber is around 0.5 μm-thick, tunnelling enhanced interface recombination dominates, which harms cells energy conversion efficiency. It is also shown that by varying either the properties of the Mo back contact or the characteristics of 3-stage growth processing, one can shift the dominating recombination mechanism from interface to space charge region and thereby improve the cells efficiency. Discussions on these experimental facts led to the conclusions that 3-stage process implies the formation of a CIGSe/CIGSe homo-interface, whose location as well as properties rule the device operation; its influence is enhanced in submicron CIGSe based solar cells.

  10. Cu(In,Ga)Se{sub 2} absorber thinning and the homo-interface model: Influence of Mo back contact and 3-stage process on device characteristics

    SciTech Connect

    Leonard, E.; Arzel, L.; Tomassini, M.; Barreau, N.; Zabierowski, P.; Fuertes Marrón, D.

    2014-08-21

    Thinning the absorber layer is one of the possibilities envisaged to further decrease the production costs of Cu(In,Ga)Se{sub 2} (CIGSe) thin films solar cell technology. In the present study, the electronic transport in submicron CIGSe-based devices has been investigated and compared to that of standard devices. It is observed that when the absorber is around 0.5 μm-thick, tunnelling enhanced interface recombination dominates, which harms cells energy conversion efficiency. It is also shown that by varying either the properties of the Mo back contact or the characteristics of 3-stage growth processing, one can shift the dominating recombination mechanism from interface to space charge region and thereby improve the cells efficiency. Discussions on these experimental facts led to the conclusions that 3-stage process implies the formation of a CIGSe/CIGSe homo-interface, whose location as well as properties rule the device operation; its influence is enhanced in submicron CIGSe based solar cells.

  11. Membrane acoustic metamaterial absorbers with magnetic negative stiffness.

    PubMed

    Zhao, Junjuan; Li, Xianhui; Wang, Yueyue; Wang, Wenjiang; Zhang, Bin; Gai, Xiaoling

    2017-02-01

    A membrane absorber usually requires a large back cavity to achieve low-frequency sound absorption. This paper describes the design of a membrane acoustic metamaterial absorber in which magnetic negative stiffness is employed to reduce the size of the back cavity. As a baseline for the present research, analysis of a typical membrane sound absorber based on an equivalent circuit model is presented first. Then, a theoretical model is established by introducing negative stiffness into a standard absorber. It is demonstrated that a small cavity with negative stiffness can achieve the acoustic impedance of a large cavity and that the absorption peak is shifted to lower frequencies. Experimental results from an impedance tube test are also presented to validate this idea and show that negative stiffness can be employed to design compact low-frequency membrane absorbers.

  12. Spontaneous emission and absorber theory

    NASA Astrophysics Data System (ADS)

    Pegg, David T.

    1997-01-01

    One of the long term interests of George Series was the construction of a theory of spontaneous emission which does not involve field quantisation. His approach was written in terms of atomic operators only and he drew a parallel with the Wheeler-Feynman absorber theory of radiation. By making a particular extra postulate, he was able to obtain the correct spontaneous emission rate and the Lamb shift reasonably simply and directly. An examination of his approach indicates that this postulate is physically reasonable and the need for it arises because quantisation in his theory occurs after the response of the absorber has been accounted for by means of the radiative reaction field. We review briefly an alternative absorber theory approach to spontaneous emission based on the direct action between the emitting atom and a quantised absorber, and outline some applications to more recent effects of interest in quantum optics.

  13. Guided tissue regeneration. Absorbable barriers.

    PubMed

    Wang, H L; MacNeil, R L

    1998-07-01

    Over the past 15 years, techniques aimed at regeneration of lost periodontal tissue have become widely used and accepted in clinical practice. Among these techniques are those which use the principles of guided tissue regeneration (GTR), wherein barriers (i.e., membranes) are used to control cell and tissue repopulation of the periodontal wound. A variety of non-absorbable and absorbable barriers have been developed and used for this purpose, with a trend in recent years toward increased use of absorbable GTR materials. This article describes the evolution of absorbable barrier materials and overview materials available for clinical use today. In addition, advantages and disadvantages of these materials are discussed, as well as possible new developments in barrier-based GTR therapy.

  14. Countercurrent flow absorber and desorber

    DOEpatents

    Wilkinson, W.H.

    1984-10-16

    Countercurrent flow absorber and desorber devices are provided for use in absorption cycle refrigeration systems and thermal boosting systems. The devices have increased residence time and surface area resulting in improved heat and mass transfer characteristics. The apparatuses may be incorporated into open cycle thermal boosting systems in which steam serves both as the refrigerant vapor which is supplied to the absorber section and as the supply of heat to drive the desorber section of the system. 9 figs.

  15. Countercurrent flow absorber and desorber

    DOEpatents

    Wilkinson, William H.

    1984-01-01

    Countercurrent flow absorber and desorber devices are provided for use in absorption cycle refrigeration systems and thermal boosting systems. The devices have increased residence time and surface area resulting in improved heat and mass transfer characteristics. The apparatuses may be incorporated into open cycle thermal boosting systems in which steam serves both as the refrigerant vapor which is supplied to the absorber section and as the supply of heat to drive the desorber section of the system.

  16. Perfect selective metamaterial solar absorbers.

    PubMed

    Wang, Hao; Wang, Liping

    2013-11-04

    In this work, we numerically investigate the radiative properties of metamaterial nanostructures made of two-dimensional tungsten gratings on a thin dielectric spacer and an opaque tungsten film from UV to mid-infrared region as potential selective solar absorbers. The metamaterial absorber with single-sized tungsten patches exhibits high absorptance in the visible and near-infrared region due to several mechanisms such as surface plasmon polaritons, magnetic polaritons, and intrinsic bandgap absorption of tungsten. Geometric effects on the resonance wavelengths and the absorptance spectra are studied, and the physical mechanisms are elucidated in detail. The absorptance could be further enhanced in a broader spectral range with double-sized metamaterial absorbers. The total solar absorptance of the optimized metamaterial absorbers at normal incidence could be more than 88%, while the total emittance is less than 3% at 100°C, resulting in total photon-to-heat conversion efficiency of 86% without any optical concentration. Moreover, the metamaterial solar absorbers exhibit quasi-diffuse behaviors as well as polarization independence. The results here will facilitate the design of novel highly efficient solar absorbers to enhance the performance of various solar energy conversion systems.

  17. Metamaterial Resonant Absorbers for Terahertz Sensing

    DTIC Science & Technology

    2015-12-01

    and their periodic nature , finite element (FE) modeling is the preferable means of designing metamaterials. In order to use metamaterials in sensors ...will incorporate the metamaterial absorber design of this research into a more efficient, cost effective, bi-material THz sensor that can be employed...in a variety of naval applications. 14. SUBJECT TERMS terahertz sensors , metamaterials, uncooled detectors 15. NUMBER OF PAGES 73 16

  18. An electromechanical low frequency panel sound absorber.

    PubMed

    Chang, Daoqing; Liu, Bilong; Li, Xiaodong

    2010-08-01

    The sound absorbing properties of a thin micro-perforated plate (MPP) coated with piezoelectric material with shunt damping technology is investigated. First a theoretical model is presented to predict the sound absorption coefficients of a thin plate attached with a piezoelectric patch and electrical circuits. Then the model is extended to analyze the sound absorption for a thin plate with micro perforations and piezoelectric material. Measurements are also carried out in an impedance tube and found to be in good agreements with the theoretical model. The sound absorption of the constructions can be much improved by tuning the electrical circuits.

  19. Relativistic many-body calculation of energies, lifetimes, polarizabilities, blackbody radiative shift, and hyperfine constants in Lu2 +

    NASA Astrophysics Data System (ADS)

    Safronova, U. I.; Safronova, M. S.; Johnson, W. R.

    2016-09-01

    Energy levels of 30 low-lying states of Lu2 + and allowed electric-dipole matrix elements between these states are evaluated using a relativistic all-order method in which all single, double, and partial triple excitations of Dirac-Fock wave functions are included to all orders of perturbation theory. Matrix elements are critically evaluated for their accuracy and recommended values of the matrix elements are given together with uncertainty estimates. Line strengths, transition rates, and lifetimes of the metastable 5 d3 /2 and 5 d5 /2 states are calculated. Recommended values are given for static polarizabilities of the 6 s , 5 d , and 6 p states and tensor polarizabilities of the 5 d and 6 p3 /2 states. Uncertainties of the polarizability values are estimated in all cases. The blackbody radiation shift of the 6 s1 /2-5 d5 /2 transition frequency of the Lu2 + ion is calculated with the aid of the recommended scalar polarizabilities of the 6 s1 /2 and 5 d5 /2 states. Finally, A and B hyperfine constants are determined for states of 2+175Lu with n ≤9 . This work provides recommended values of transition matrix elements, polarizabilities, and hyperfine constants of Lu2 +, critically evaluated for accuracy, for benchmark tests of high-precision theoretical methodology and planning of future experiments.

  20. Water binding energies of [Pb(amino acid-H)H2O]+ complexes determined by blackbody infrared radiative dissociation.

    PubMed

    Burt, Michael B; Decker, Sarah G A; Fridgen, Travis D

    2012-11-21

    The water binding energies (E(0)) of eight deprotonated Pb(2+)-amino acid (Aa) complexes of the form [Pb(Aa-H)H(2)O](+) (Aa = Gly, Ala, Val, Leu, Ile, Phe, Glu, and Lys) were determined using blackbody infrared radiative dissociation (BIRD). A Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer was used to trap ions generated by electrospray ionization (ESI) in a "zero"-pressure (~10(-10) torr) cell where dissociation can only occur by absorption of thermally generated photons. Since the [Pb(Aa-H)H(2)O](+) complexes have relatively few vibrational degrees of freedom (36-78) and are within the slow-exchange kinetic limit, the master equation was solved to extract meaningful threshold dissociation energies and thermal unimolecular dissociation rate constants (k(uni)). The master equation analysis uses variable reaction coordinate transition state theory (VRC-TST) to minimize the Rice-Ramsperger-Kassel-Marcus (RRKM) dissociation rate constants. The determined water binding energies range from 76.6 to 113.6 kJ mol(-1), and agree well with 0 K dissociation energies calculated using the B3LYP/6-31+G(d,p) and MP2(full)/6-311++G(2d,2p)//B3LYP/6-31+G(d,p) methods. The relative strengths of the binding energies reflect the known structural isomers (A-, B-, C-, and D-type) of these [Pb(Aa-H)H(2)O](+) complexes.

  1. Nonlinear Vacuum Polarization In Intense Blackbody Radiation And The Generation Of Cherenkov Radiation By Energetic Charged Particles

    NASA Astrophysics Data System (ADS)

    Wu, Sheldon S. Q.; Hartemann, F. V.; Barty, C. P. J.

    2010-03-01

    A study of thermally-induced vacuum polarization stemming from the Euler-Heisenberg nonlinear radiation correction to Maxwell equations is conducted. While nonlinear effects associated with photon-photon scattering in the photon gas had been previously calculated, we present an analysis in the framework of stochastic electrodynamics. To lowest order of approximation, it is shown that the phase velocity of light is reduced in the presence of intense ambient electromagnetic radiation. Therefore Cherenkov radiation can be generated when charged particles traverse a region of intense blackbody radiation. Suitable conditions may be found in astrophysical environments. Cosmic ray electrons and positrons in the GeV to TeV range meet the energy requirement for this process to occur. We present calculations of the emission characteristics and conditions under which Cherenkov radiation may be observed. This effect combined with synchrotron and inverse Compton processes may lead to a more complete understanding of cosmic ray propagation. Also of interest, the question of the linearity of the relic cosmic microwave background is under investigation using this formalism and will be discussed. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  2. Derivation of the blackbody radiation spectrum from the equivalence principle in classical physics with classical electromagnetic zero-point radiation

    SciTech Connect

    Boyer, T.H.

    1984-03-15

    A derivation of Planck's spectrum including zero-point radiation is given within classical physics from recent results involving the thermal effects of acceleration through classical electromagnetic zero-point radiation. A harmonic electric-dipole oscillator undergoing a uniform acceleration a through classical electromagnetic zero-point radiation responds as would the same oscillator in an inertial frame when not in zero-point radiation but in a different spectrum of random classical radiation. Since the equivalence principle tells us that the oscillator supported in a gravitational field g = -a will respond in the same way, we see that in a gravitational field we can construct a perpetual-motion machine based on this different spectrum unless the different spectrum corresponds to that of thermal equilibrium at a finite temperature. Therefore, assuming the absence of perpetual-motion machines of the first kind in a gravitational field, we conclude that the response of an oscillator accelerating through classical zero-point radiation must be that of a thermal system. This then determines the blackbody radiation spectrum in an inertial frame which turns out to be exactly Planck's spectrum including zero-point radiation.

  3. Thermally Resilient, Broadband Optical Absorber from UV to IR Derived from Carbon Nanostructures

    NASA Technical Reports Server (NTRS)

    Kaul, Anupama B.; Coles, James B.

    2012-01-01

    Optical absorber coatings have been developed from carbon-based paints, metal blacks, or glassy carbon. However, such materials are not truly black and have poor absorption characteristics at longer wavelengths. The blackness of such coatings is important to increase the accuracy of calibration targets used in radiometric imaging spectrometers since blackbody cavities are prohibitively large in size. Such coatings are also useful potentially for thermal detectors, where a broadband absorber is desired. Au-black has been a commonly used broadband optical absorber, but it is very fragile and can easily be damaged by heat and mechanical vibration. An optically efficient, thermally rugged absorber could also be beneficial for thermal solar cell applications for energy harnessing, particularly in the 350-2,500 nm spectral window. It has been demonstrated that arrays of vertically oriented carbon nanotubes (CNTs), specifically multi-walled-carbon- nanotubes (MWCNTs), are an exceptional optical absorber over a broad range of wavelengths well into the infrared (IR). The reflectance of such arrays is 100x lower compared to conventional black materials, such as Au black in the spectral window of 350-2,500 nm. Total hemispherical measurements revealed a reflectance of approximately equal to 1.7% at lambda approximately equal to 1 micrometer, and at longer wavelengths into the infrared (IR), the specular reflectance was approximately equal to 2.4% at lambda approximately equal to 7 micrometers. The previously synthesized CNTs for optical absorber applications were formed using water-assisted thermal chemical vapor deposition (CVD), which yields CNT lengths in excess of 100's of microns. Vertical alignment, deemed to be a critical feature in enabling the high optical absorption from CNT arrays, occurs primarily via the crowding effect with thermal CVD synthesized CNTs, which is generally not effective in aligning CNTs with lengths less than 10 m. Here it has been shown that the

  4. Mushroom plasmonic metamaterial infrared absorbers

    SciTech Connect

    Ogawa, Shinpei Fujisawa, Daisuke; Hata, Hisatoshi; Uetsuki, Mitsuharu; Misaki, Koji; Kimata, Masafumi

    2015-01-26

    There has been a considerable amount of interest in the development of various types of electromagnetic wave absorbers for use in different wavelength ranges. In particular, infrared (IR) absorbers with wavelength selectivity can be applied to advanced uncooled IR sensors, which would be capable of identifying objects through their radiation spectrum. In the present study, mushroom plasmonic metamaterial absorbers (MPMAs) for the IR wavelength region were designed and fabricated. The MPMAs consist of a periodic array of thin metal micropatches connected to a thin metal plate with narrow silicon (Si) posts. A Si post height of 200 nm was achieved by isotropic XeF{sub 2} etching of a thin Si layer sandwiched between metal plates. This fabrication procedure is relatively simple and is consistent with complementary metal oxide semiconductor technology. The absorption spectra of the fabricated MPMAs were experimentally measured. In addition, theoretical calculations of their absorption properties were conducted using rigorous coupled wave analysis. Both the calculated and measured absorbance results demonstrated that these MPMAs can realize strong selective absorption at wavelengths beyond the period of the array by varying the micropatch width. Absorbance values greater than 90% were achieved. Dual- or single-mode absorption can also be selected by varying the width of the Si posts. Pixel structures using such MPMAs could be used as high responsivity, high resolution and fast uncooled IR sensors.

  5. Mushroom plasmonic metamaterial infrared absorbers

    NASA Astrophysics Data System (ADS)

    Ogawa, Shinpei; Fujisawa, Daisuke; Hata, Hisatoshi; Uetsuki, Mitsuharu; Misaki, Koji; Kimata, Masafumi

    2015-01-01

    There has been a considerable amount of interest in the development of various types of electromagnetic wave absorbers for use in different wavelength ranges. In particular, infrared (IR) absorbers with wavelength selectivity can be applied to advanced uncooled IR sensors, which would be capable of identifying objects through their radiation spectrum. In the present study, mushroom plasmonic metamaterial absorbers (MPMAs) for the IR wavelength region were designed and fabricated. The MPMAs consist of a periodic array of thin metal micropatches connected to a thin metal plate with narrow silicon (Si) posts. A Si post height of 200 nm was achieved by isotropic XeF2 etching of a thin Si layer sandwiched between metal plates. This fabrication procedure is relatively simple and is consistent with complementary metal oxide semiconductor technology. The absorption spectra of the fabricated MPMAs were experimentally measured. In addition, theoretical calculations of their absorption properties were conducted using rigorous coupled wave analysis. Both the calculated and measured absorbance results demonstrated that these MPMAs can realize strong selective absorption at wavelengths beyond the period of the array by varying the micropatch width. Absorbance values greater than 90% were achieved. Dual- or single-mode absorption can also be selected by varying the width of the Si posts. Pixel structures using such MPMAs could be used as high responsivity, high resolution and fast uncooled IR sensors.

  6. Carbon Absorber Retrofit Equipment (CARE)

    SciTech Connect

    Klein, Eric

    2015-12-23

    During Project DE-FE0007528, CARE (Carbon Absorber Retrofit Equipment), Neumann Systems Group (NSG) designed, installed and tested a 0.5MW NeuStream® carbon dioxide (CO2) capture system using the patented NeuStream® absorber equipment and concentrated (6 molal) piperazine (PZ) as the solvent at Colorado Springs Utilities’ (CSU’s) Martin Drake pulverized coal (PC) power plant. The 36 month project included design, build and test phases. The 0.5MW NeuStream® CO2 capture system was successfully tested on flue gas from both coal and natural gas combustion sources and was shown to meet project objectives. Ninety percent CO2 removal was achieved with greater than 95% CO2product purity. The absorbers tested support a 90% reduction in absorber volume compared to packed towers and with an absorber parasitic power of less than 1% when configured for operation with a 550MW coal plant. The preliminary techno-economic analysis (TEA) performed by the Energy and Environmental Research Center (EERC) predicted an over-the-fence cost of $25.73/tonne of CO2 captured from a sub-critical PC plant.

  7. Modeling and Simulation of Turbulent Flows through a Solar Air Heater Having Square-Sectioned Transverse Rib Roughness on the Absorber Plate

    PubMed Central

    Yadav, Anil Singh; Bhagoria, J. L.

    2013-01-01

    Solar air heater is a type of heat exchanger which transforms solar radiation into heat energy. The thermal performance of conventional solar air heater has been found to be poor because of the low convective heat transfer coefficient from the absorber plate to the air. Use of artificial roughness on a surface is an effective technique to enhance the rate of heat transfer. A CFD-based investigation of turbulent flow through a solar air heater roughened with square-sectioned transverse rib roughness has been performed. Three different values of rib-pitch (P) and rib-height (e) have been taken such that the relative roughness pitch (P/e = 14.29) remains constant. The relative roughness height, e/D, varies from 0.021 to 0.06, and the Reynolds number, Re, varies from 3800 to 18,000. The results predicted by CFD show that the average heat transfer, average flow friction, and thermohydraulic performance parameter are strongly dependent on the relative roughness height. A maximum value of thermohydraulic performance parameter has been found to be 1.8 for the range of parameters investigated. Comparisons with previously published work have been performed and found to be in excellent agreement. PMID:24222752

  8. Low temperature selective absorber research

    NASA Astrophysics Data System (ADS)

    Herzenberg, S. A.; Silberglitt, R.

    1982-04-01

    Research carried out since 1979 on selective absorbers is surveyed, with particular attention given to the low-temperature coatings seen as promising for flat plate and evacuated tube applications. The most thoroughly investigated absorber is black chrome, which is highly selective and is the most durable low-temperature absorber. It is believed that other materials, because of their low cost and lower content of strategic materials, may eventually supplant black chrome. Among these candidates are chemically converted black nickel; anodically oxidized nickel, zinc, and copper composites; and nickel or other low-cost multilayer coatings. In reviewing medium and high-temperature research, black chrome, multilayer coatings and black cobalt are seen as best medium-temperature candidates. For high temperatures, an Al2O3/Pt-Al203 multilayer composite or the zirconium diboride coating is preferred.

  9. Magnetically tunable metamaterial perfect absorber

    NASA Astrophysics Data System (ADS)

    Lei, Ming; Feng, Ningyue; Wang, Qingmin; Hao, Yanan; Huang, Shanguo; Bi, Ke

    2016-06-01

    A magnetically tunable metamaterial perfect absorber (MPA) based on ferromagnetic resonance is experimentally and numerically demonstrated. The ferrite-based MPA is composed of an array of ferrite rods and a metallic ground plane. Frequency dependent absorption of the ferrite-based MPA under a series of applied magnetic fields is discussed. An absorption peak induced by ferromagnetic resonance appears in the range of 8-12 GHz under a certain magnetic field. Both the simulated and experimental results demonstrate that the absorption frequency of the ferrite-based MPA can be tuned by the applied magnetic field. This work provides an effective way to fabricate the magnetically tunable metamaterial perfect absorber.

  10. Adaptive inertial shock-absorber

    NASA Astrophysics Data System (ADS)

    Faraj, Rami; Holnicki-Szulc, Jan; Knap, Lech; Seńko, Jarosław

    2016-03-01

    This paper introduces and discusses a new concept of impact absorption by means of impact energy management and storage in dedicated rotating inertial discs. The effectiveness of the concept is demonstrated in a selected case-study involving spinning management, a recently developed novel impact-absorber. A specific control technique performed on this device is demonstrated to be the main source of significant improvement in the overall efficiency of impact damping process. The influence of various parameters on the performance of the shock-absorber is investigated. Design and manufacturing challenges and directions of further research are formulated.

  11. Damage tolerant light absorbing material

    DOEpatents

    Lauf, R.J.; Hamby, C. Jr.; Akerman, M.A.; Seals, R.D.

    1993-09-07

    A light absorbing article comprised of a composite of carbon-bonded carbon fibers, is prepared by: blending carbon fibers with a carbonizable organic powder to form a mixture; dispersing the mixture into an aqueous slurry; vacuum molding the aqueous slurry to form a green article; drying and curing the green article to form a cured article; and, carbonizing the cured article at a temperature of at least about 1000 C to form a carbon-bonded carbon fiber light absorbing composite article having a bulk density less than 1 g/cm[sup 3]. 9 figures.

  12. Damage tolerant light absorbing material

    DOEpatents

    Lauf, Robert J.; Hamby, Jr., Clyde; Akerman, M. Alfred; Seals, Roland D.

    1993-01-01

    A light absorbing article comprised of a composite of carbon-bonded carbon fibers, prepared by: blending carbon fibers with a carbonizable organic powder to form a mixture; dispersing the mixture into an aqueous slurry; vacuum molding the aqueous slurry to form a green article; drying and curing the green article to form a cured article; and, carbonizing the cured article at a temperature of at least about 1000.degree. C. to form a carbon-bonded carbon fiber light absorbing composite article having a bulk density less than 1 g/cm.sup.3.

  13. HS 1603+3820 and its Warm Absorber

    NASA Astrophysics Data System (ADS)

    Nikołajuk, M.; Różańska, A.; Czerny, B.; Dobrzycki, A.

    2009-07-01

    We use photoionization codes CLOUDY and TITAN to obtain physical conditions in the absorbing medium close to the nucleus of a distant quasar (z = 2.54) HS 1603+3820. We found that the total column density of this Warm Absorber is 2 x 1022 cm-2. Due to the softness of the quasars spectrum the modelling allowed us also to determine uniquely the volume hydrogen density of this warm gas (n = 1010 cm-3) which combined with the other quasar parameters leads to a distance determination to the Warm Absorber from the central source which is ~ 1.5 x 1016 cm.

  14. Dynamic vibration absorber using magnetic spring and damper

    SciTech Connect

    Aida, Y.; Niwa, H.; Miyano, H.; Ozaki, O.; Kitada, Y.

    1995-12-31

    This paper describes a dynamic vibration absorber based on a magnetic spring and damper system. A pair of double cylindrical magnets face each other across a gap, with one magnet fixed to the target structure and the other to the moving mass of the dynamic vibration absorber. The magnetic restoring force characteristics of the proposed system are examined through static loading tests and analysis. The dynamic characteristics are also tested in vibration tests. Furthermore, application of the proposed dynamic vibration absorber to a rotating machinery model demonstrates that the system gives effective two-dimensional vibration control.

  15. The AWWE-based hybrid absorbing boundary condition for finite-difference modeling and its application in reverse-time migration

    NASA Astrophysics Data System (ADS)

    Zhang, Xi; Liu, Yang; Cai, Xiaohui; Ren, Zhiming

    2015-12-01

    The reverse-time migration (RTM) crosscorrelation imaging condition requires that the forward-propagated source wavefield and the backward-propagated receiver wavefield must be obtained at the same time. The easiest way to get the source wavefield is to save the entire time history of the full wavefield into computer memory. However, this strategy requires huge amount of data storage. It is impossible for large-scale 3D RTM. To reduce the computer memory cost, the back-propagated source wavefield is reconstructed by using the stored boundary wavefield. Its computer memory is proportional to the saved boundary grid points. For high order of spatial finite-difference (FD) schemes, more boundary grid points are needed to be stored, which consumes a large amount of the computer memory required for RTM. To further reduce the computer memory cost, we adopt the hybrid absorbing boundary condition (ABC) combined with the arbitrarily wide-angle wave equations (AWWEs). In our method, three boundary grid points can obtain good absorption. The source wavefield can be accurately reconstructed by using these points and the mirror-image symmetry method. Numerical experiments demonstrate the correctness and effectiveness of the proposed method. We compared our method with the conventional hybrid ABC method based on the 15°one way wave equations (OWWEs). Comparisons show that our method with three boundary grid points can achieve the same absorption as the conventional method with ten boundary grid points. For twentieth order of accuracy in space, our method uses only about 30% of memory requirement and about 59% of computation time required by the conventional method.

  16. Efficacy and immunogenicity of single-dose AdVAV intranasal anthrax vaccine compared to anthrax vaccine absorbed in an aerosolized spore rabbit challenge model.

    PubMed

    Krishnan, Vyjayanthi; Andersen, Bo H; Shoemaker, Christine; Sivko, Gloria S; Tordoff, Kevin P; Stark, Gregory V; Zhang, Jianfeng; Feng, Tsungwei; Duchars, Matthew; Roberts, M Scot

    2015-04-01

    AdVAV is a replication-deficient adenovirus type 5-vectored vaccine expressing the 83-kDa protective antigen (PA83) from Bacillus anthracis that is being developed for the prevention of disease caused by inhalation of aerosolized B. anthracis spores. A noninferiority study comparing the efficacy of AdVAV to the currently licensed Anthrax Vaccine Absorbed (AVA; BioThrax) was performed in New Zealand White rabbits using postchallenge survival as the study endpoint (20% noninferiority margin for survival). Three groups of 32 rabbits were vaccinated with a single intranasal dose of AdVAV (7.5 × 10(7), 1.5 × 10(9), or 3.5 × 10(10) viral particles). Three additional groups of 32 animals received two doses of either intranasal AdVAV (3.5 × 10(10) viral particles) or intramuscular AVA (diluted 1:16 or 1:64) 28 days apart. The placebo group of 16 rabbits received a single intranasal dose of AdVAV formulation buffer. All animals were challenged via the inhalation route with a targeted dose of 200 times the 50% lethal dose (LD50) of aerosolized B. anthracis Ames spores 70 days after the initial vaccination and were followed for 3 weeks. PA83 immunogenicity was evaluated by validated toxin neutralizing antibody and serum anti-PA83 IgG enzyme-linked immunosorbent assays (ELISAs). All animals in the placebo cohort died from the challenge. Three of the four AdVAV dose cohorts tested, including two single-dose cohorts, achieved statistical noninferiority relative to the AVA comparator group, with survival rates between 97% and 100%. Vaccination with AdVAV also produced antibody titers with earlier onset and greater persistence than vaccination with AVA.

  17. Counterflow absorber for an absorption refrigeration system

    DOEpatents

    Reimann, Robert C.

    1984-01-01

    An air-cooled, vertical tube absorber for an absorption refrigeration system is disclosed. Strong absorbent solution is supplied to the top of the absorber and refrigerant vapor is supplied to the bottom of the absorber to create a direct counterflow of refrigerant vapor and absorbent solution in the absorber. The refrigeration system is designed so that the volume flow rate of refrigerant vapor in the tubes of the absorber is sufficient to create a substantially direct counterflow along the entire length of each tube in the absorber. This provides several advantages for the absorber such as higher efficiency and improved heat transfer characteristics, and allows improved purging of non-condensibles from the absorber.

  18. Metamaterial Absorbers for Microwave Detection

    DTIC Science & Technology

    2015-06-01

    a) Depiction of metamaterial array of square resonators atop FR4. (b) Metamaterial dimensions and structure...comparison for varying resonator array dimension sizes. ..............23 Figure 12. Absorption derived from raw reflection data...36 x Figure 23. Metamaterial absorber array where resonator dimensions control the detection frequencies and

  19. Oil and fat absorbing polymers

    NASA Technical Reports Server (NTRS)

    Marsh, H. E., Jr. (Inventor)

    1977-01-01

    A method is described for forming a solid network polymer having a minimal amount of crosslinking for use in absorbing fats and oils. The polymer remains solid at a swelling ratio in oil or fat of at least ten and provides an oil absorption greater than 900 weight percent.

  20. Energy deposition studies for the LBNE beam absorber

    SciTech Connect

    Rakhno, Igor L.; Mokhov, Nikolai V.; Tropin, Igor S.

    2015-01-29

    Results of detailed Monte Carlo energy deposition studies performed for the LBNE absorber core and the surrounding shielding with the MARS15 code are described. The model of the entire facility, that includes a pion-production target, focusing horns, target chase, decay channel, hadron absorber system – all with corresponding radiation shielding – was developed using the recently implemented ROOT-based geometry option in the MARS15 code. This option provides substantial flexibility and automation when developing complex geometry models. Both normal operation and accidental conditions were studied. Various design options were considered, in particular the following: (i) filling the decay pipe with air or helium; (ii) the absorber mask material and shape; (iii) the beam spoiler material and size. Results of detailed thermal calculations with the ANSYS code helped to select the most viable absorber design options.

  1. A circuit method to integrate metamaterial and graphene in absorber design

    NASA Astrophysics Data System (ADS)

    Wang, Zuojia; Zhou, Min; Lin, Xiao; Liu, Huixia; Wang, Huaping; Yu, Faxin; Lin, Shisheng; Li, Erping; Chen, Hongsheng

    2014-10-01

    We theoretically investigate a circuit analog approach to integrate graphene and metamaterial in electromagnetic wave absorber design. In multilayer graphene-metamaterial (GM) absorbers, ultrathin metamaterial elements are theoretically modeled as equivalent loads which attached to the junctions between two transmission lines. Combining with the benefits of tunable chemical potential in graphene, an optimized GM absorber is proposed as a proof of the circuit method. Numerical simulation results demonstrate the effectiveness of the circuit analytical model. The operating frequency of the GM absorber can be varied in terahertz frequency, indicating the potential applications of the GM absorber in sensors, modulators, and filters.

  2. Calirimeter/absorber optimization for a RHIC dimuon experiment

    SciTech Connect

    Aronson, S.H.; Murtagh, M.J.; Starks, M.; Liu, X.T.; Petitt, G.A.; Zhang, Z.; Ewell, L.A.; Hill, J.C.; Wohn, F.K.; Costales, J.B.; Namboodiri, M.N., Sangster, T.C.; Thomas, J.H.; Gavron, A.; Waters, L.; Kehoe, W.L.; Steadman, S.G.; Awes, T.C.; Obenshain, F.E.; Saini, S.; Young, G.R.; Chang, J.; Fung, S.Y.; Kang, J.H.; Kreke, J.; He, Xiaochun, Sorensen, S.P.; Cornell, E.C.; Maguire, C.F.

    1991-12-31

    The RD-10 R&D effort on calorimeter/absorber optimization for a RHIC experiment had an extended run in 1991 using the A2 test beam at the AGS. Measurements were made of the leakage of particles behind various model hadron calorimeters. Behavior of the calorimeter/absorber as a muon-identifier was studied. First comparisons of results from test measurements to calculated results using the GHEISHA code were made

  3. Fluence-to-absorbed-dose conversion coefficients for neutron beams from 0.001 eV to 100 GeV calculated for a set of pregnant female and fetus models

    NASA Astrophysics Data System (ADS)

    Taranenko, Valery; Xu, X. George

    2008-03-01

    Protection of fetuses against external neutron exposure is an important task. This paper reports a set of absorbed dose conversion coefficients for fetal and maternal organs for external neutron beams using the RPI-P pregnant female models and the MCNPX code. The newly developed pregnant female models represent an adult female with a fetus including its brain and skeleton at the end of each trimester. The organ masses were adjusted to match the reference values within 1%. For the 3 mm cubic voxel size, the models consist of 10-15 million voxels for 35 organs. External monoenergetic neutron beams of six standard configurations (AP, PA, LLAT, RLAT, ROT and ISO) and source energies 0.001 eV-100 GeV were considered. The results are compared with previous data that are based on simplified anatomical models. The differences in dose depend on source geometry, energy and gestation periods: from 20% up to 140% for the whole fetus, and up to 100% for the fetal brain. Anatomical differences are primarily responsible for the discrepancies in the organ doses. For the first time, the dependence of mother organ doses upon anatomical changes during pregnancy was studied. A maximum of 220% increase in dose was observed for the placenta in the nine months model compared to three months, whereas dose to the pancreas, small and large intestines decreases by 60% for the AP source for the same models. Tabulated dose conversion coefficients for the fetus and 27 maternal organs are provided.

  4. EXTERNAL INVERSE COMPTON SPECTRA FOR MONOENERGETIC AND BLACKBODY PHOTON FIELDS UPSCATTERED BY A POWER-LAW ELECTRON DISTRIBUTION WITH A FINITE ENERGY RANGE

    SciTech Connect

    Fouka, M.; Ouichaoui, S. E-mail: souichaoui@usthb.dz

    2011-08-20

    We have calculated the inverse Compton (IC) integrated spectral power within the Thomson limit for a monoenergetic isotropic photon field upscattered off highly relativistic electrons assuming an isotropic power-law distribution of the latter, N({gamma}) = C{gamma}{sup -p}, with Lorentz parameter values {gamma}{sub 1} < {gamma} < {gamma}{sub 2}. Our interest was essentially focused on the case of a finite energy range (finite {gamma}{sub 2}) possibly having realistic applications in high-energy astrophysical sites, mainly relativistic shock regions. To this end, we have defined and derived a dimensionless parametric function, F{sub p} (z{sub 1}, {eta}), with variables z{sub 1} = {epsilon}{sub 1}/4{gamma}{sup 2}{sub 1}{epsilon} and {eta} = {gamma}{sub 2}/{gamma}{sub 1}. This result was used to derive the IC-integrated spectral power for an upscattered blackbody (BB) photon field using a dimensionless parametric function, W{sub p} ({xi}, {eta}), with variable {xi} = {epsilon}{sub 1}/4{gamma}{sup 2}{sub 1} kT. Asymptotic forms of this function have been derived for three energy ranges, i.e., {xi} << 1, 1 << {xi} << {eta}{sup 2}, and {xi} >> {eta}{sup 2}. Then, a characteristic value, {eta}{sub c}(p, {epsilon}) with {epsilon} << 1, of parameter {eta} was defined such that the middle range asymptotic form of W{sub p} ({xi}, {eta}) could be valid and good when {eta} {approx}> {eta}{sub c}(p, {epsilon}), by deriving an approximate expression of this particular value for {epsilon} = 10{sup -3}. The resulting spectra featured by a high-energy cutoff in the case of low values of the ratio {eta} can be discussed at least for a population of short gamma-ray bursts (GRBs), those best described by the cutoff power-law model with a low-energy spectral index, {alpha} {approx} 0. Furthermore, it is suggested that for GRB spectra with {alpha} < -1/2 pertaining to the prompt emission phase, the IC is a likely emission mechanism for both monoenergetic and BB photon fields if one

  5. External Inverse Compton Spectra for Monoenergetic and Blackbody Photon Fields Upscattered by a Power-law Electron Distribution with a Finite Energy Range

    NASA Astrophysics Data System (ADS)

    Fouka, M.; Ouichaoui, S.

    2011-08-01

    We have calculated the inverse Compton (IC) integrated spectral power within the Thomson limit for a monoenergetic isotropic photon field upscattered off highly relativistic electrons assuming an isotropic power-law distribution of the latter, N(γ) = Cγ-p , with Lorentz parameter values γ1 < γ < γ2. Our interest was essentially focused on the case of a finite energy range (finite γ2) possibly having realistic applications in high-energy astrophysical sites, mainly relativistic shock regions. To this end, we have defined and derived a dimensionless parametric function, Fp (z 1, η), with variables z 1 = epsilon1/4γ2 1epsilon and η = γ2/γ1. This result was used to derive the IC-integrated spectral power for an upscattered blackbody (BB) photon field using a dimensionless parametric function, Wp (ξ, η), with variable ξ = epsilon1/4γ2 1 kT. Asymptotic forms of this function have been derived for three energy ranges, i.e., ξ Lt 1, 1 Lt ξ Lt η2, and ξ Gt η2. Then, a characteristic value, η c (p, ɛ) with ɛ Lt 1, of parameter η was defined such that the middle range asymptotic form of Wp (ξ, η) could be valid and good when η >~ η c (p, ɛ), by deriving an approximate expression of this particular value for ɛ = 10-3. The resulting spectra featured by a high-energy cutoff in the case of low values of the ratio η can be discussed at least for a population of short gamma-ray bursts (GRBs), those best described by the cutoff power-law model with a low-energy spectral index, α ≈ 0. Furthermore, it is suggested that for GRB spectra with α < -1/2 pertaining to the prompt emission phase, the IC is a likely emission mechanism for both monoenergetic and BB photon fields if one assumes that the former photon field could exist specifically in the GRB environment. Various suitable astrophysical applications are presented and discussed.

  6. Blackbody Radiation Tables

    DTIC Science & Technology

    at the indicated wavelength and temperature, Planck’s equation . This equation represents the monochromatic radiant intensity at a particular wavelength from a perfect radiator maintained at the indicated temperature.

  7. On Blackbody Radiation.

    ERIC Educational Resources Information Center

    Jain, Pushpendra K.

    1991-01-01

    The interrelationship between the various forms of the Planck radiation equation is discussed. A differential equation that gives intensity or energy density of radiation per unit wavelength or per unit frequency is emphasized. The Stefan-Boltzmann Law and the change in the glow of a hot body with temperature are also discussed. (KR)

  8. Improved Blackbody Simulator

    DTIC Science & Technology

    1974-06-01

    copper , ani steel. The candidate coatings were different forms of the oxides of each 28 4 29 metal. Aluminum was selected as a candidate because of its...high thermal conductivity and its hard oxide coating. (See Appendix C2.) Copper was selected as a candidate because of its high conductivity and because...of reports that copper could be oxidized to form a hard black cupric oxide coating. Steel was selected as a candidate because of its high temperature

  9. Digital Alloy Absorber for Photodetectors

    NASA Technical Reports Server (NTRS)

    Hill, Cory J. (Inventor); Ting, David Z. (Inventor); Gunapala, Sarath D. (Inventor)

    2016-01-01

    In order to increase the spectral response range and improve the mobility of the photo-generated carriers (e.g. in an nBn photodetector), a digital alloy absorber may be employed by embedding one (or fraction thereof) to several monolayers of a semiconductor material (insert layers) periodically into a different host semiconductor material of the absorber layer. The semiconductor material of the insert layer and the host semiconductor materials may have lattice constants that are substantially mismatched. For example, this may performed by periodically embedding monolayers of InSb into an InAsSb host as the absorption region to extend the cutoff wavelength of InAsSb photodetectors, such as InAsSb based nBn devices. The described technique allows for simultaneous control of alloy composition and net strain, which are both key parameters for the photodetector operation.

  10. USE OF PBPK MODELS FOR ASSESSING ABSORBED DOSE AND CHE INHIBITION FROM AGGREGATE EXPOSURE OF INFANTS AND CHILDREN TO ORGANOPHOSPHORUS INSECTICIDES

    EPA Science Inventory

    A physiological pharmacokinetic (PBPK) modeling framework has been established to assess cumulative risk of dose and injury of infants and children to organophosphorus (OP) insecticides from aggregate sources and routes. Exposure inputs were drawn from all reasonable sources, pr...

  11. Kinetic modeling of dissolution and crystallization of slurries with attenuated total reflectance UV-visible absorbance and near-infrared reflectance measurements.

    PubMed

    Hsieh, Chun H; Billeter, Julien; McNally, Mary Ellen P; Hoffman, Ronald M; Gemperline, Paul J

    2013-06-04

    Slurries are often used in chemical and pharmaceutical manufacturing processes but present challenging online measurement and monitoring problems. In this paper, a novel multivariate kinetic modeling application is described that provides calibration-free estimates of time-resolved profiles of the solid and dissolved fractions of a substance in a model slurry system. The kinetic model of this system achieved data fusion of time-resolved spectroscopic measurements from two different kinds of fiber-optic probes. Attenuated total reflectance UV-vis (ATR UV-vis) and diffuse reflectance near-infrared (NIR) spectra were measured simultaneously in a small-scale semibatch reactor. A simplified comprehensive kinetic model was then fitted to the time-resolved spectroscopic data to determine the kinetics of crystallization and the kinetics of dissolution for online monitoring and quality control purposes. The parameters estimated in the model included dissolution and crystal growth rate constants, as well as the dissolution rate order. The model accurately estimated the degree of supersaturation as a function of time during conditions when crystallization took place and accurately estimated the degree of undersaturation during conditions when dissolution took place.

  12. Energy-Absorbing, Lightweight Wheels

    NASA Technical Reports Server (NTRS)

    Waydo, Peter

    2003-01-01

    Improved energy-absorbing wheels are under development for use on special-purpose vehicles that must traverse rough terrain under conditions (e.g., extreme cold) in which rubber pneumatic tires would fail. The designs of these wheels differ from those of prior non-pneumatic energy-absorbing wheels in ways that result in lighter weights and more effective reduction of stresses generated by ground/wheel contact forces. These wheels could be made of metals and/or composite materials to withstand the expected extreme operating conditions. As shown in the figure, a wheel according to this concept would include an isogrid tire connected to a hub via spring rods. The isogrid tire would be a stiff, lightweight structure typically made of aluminum. The isogrid aspect of the structure would both impart stiffness and act as a traction surface. The hub would be a thin-walled body of revolution having a simple or compound conical or other shape chosen for structural efficiency. The spring rods would absorb energy and partially isolate the hub and the supported vehicle from impact loads. The general spring-rod configuration shown in the figure was chosen because it would distribute contact and impact loads nearly evenly around the periphery of the hub, thereby helping to protect the hub against damage that would otherwise be caused by large loads concentrated onto small portions of the hub.

  13. Acoustic metamaterial structures based on multi-frequency vibration absorbers

    NASA Astrophysics Data System (ADS)

    Pai, P. Frank; Peng, Hao

    2014-03-01

    This paper presents a new metamaterial beam based on multi-frequency vibration absorbers for broadband vibration absorption. The proposed metamaterial beam consists of a uniform isotropic beam and small two-mass spring-mass- damper subsystems at many locations along the beam to act as multi-frequency vibration absorbers. For an infinite metamaterial beam, governing equations of a unit cell are derived using the extended Hamilton principle. The existence of two stopbands is demonstrated using a model based on averaging material properties over a cell length and a model based on finite element modeling and the Bloch-Floquet theory for periodic structures. For a finite metamaterial beam, because these two idealized models cannot be used for finite beams and/or elastic waves having short wavelengths, a finite-element method is used for detailed modeling and analysis. The concepts of negative effective mass and effective stiffness and how the spring-mass-damper subsystem creates two stopbands are explained in detail. Numerical simulations reveal that the actual working mechanism of the proposed metamaterial beam is based on the concept of conventional mechanical vibration absorbers. For an incoming wave with a frequency in one of the two stopbands, the absorbers are excited to vibrate in their optical modes to create shear forces to straighten the beam and stop the wave propagation. For an incoming wave with a frequency outside of but between the two stopbands, it can be efficiently damped out by the damper with the second mass of each absorber. Hence, the two stopbands are connected into a wide stopband. Numerical examples validate the concept and show that the structure's boundary conditions do not have significant influence on the absorption of high-frequency waves. However, for absorption of low-frequency waves, the structure's boundary conditions and resonance frequencies and the location and spatial distribution of absorbers need to be considered in design, and it

  14. A THz plasmonics perfect absorber and Fabry-Perot cavity mechanism (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Zhou, Jiangfeng; Bhattarai, Khagendra; Silva, Sinhara; Jeon, Jiyeon; Kim, Junoh; Lee, Sang Jun; Ku, Zahyun

    2016-10-01

    Light Modulator for THz Applications," Advanced Optical Materials, vol. 2, pp. 275-279, 2014. [7] H. Tao, N. I. Landy, C. M. Bingham, X. Zhang, R. D. Averitt, and W. J. Padilla, "A metamaterial absorber for the terahertz regime: Design, fabrication and characterization," Optics Express, vol. 16, pp. 7181-7188, May 12 2008. [8] J. Hao, J. Wang, X. Liu, W. J. Padilla, L. Zhou, and M. Qiu, "High performance optical absorber based on a plasmonic metamaterial," Applied Physics Letters, vol. 96, p. 251104, 2010. [9] X. Liu, T. Tyler, T. Starr, A. F. Starr, N. M. Jokerst, and W. J. Padilla, "Taming the Blackbody with Infrared Metamaterials as Selective Thermal Emitters," Physical Review Letters, vol. 107, p. 045901, 07/18/ 2011. [10] T. Maier and H. Brückl, "Wavelength-tunable microbolometers with metamaterial absorbers," Optics Letters, vol. 34, pp. 3012-3014, 2009/10/01 2009. [11] A. Tittl, P. Mai, R. Taubert, D. Dregely, N. Liu, and H. Giessen, "Palladium-Based Plasmonic Perfect Absorber in the Visible Wavelength Range and Its Application to Hydrogen Sensing," Nano Letters, vol. 11, pp. 4366-4369, 2011/10/12 2011. [12] N. Liu, M. Mesch, T. Weiss, M. Hentschel, and H. Giessen, "Infrared Perfect Absorber and Its Application As Plasmonic Sensor," Nano Letters, vol. 10, pp. 2342-2348, Jul 2010. [13] G. H. Li, X. S. Chen, O. P. Li, C. X. Shao, Y. Jiang, L. J. Huang, et al., "A novel plasmonic resonance sensor based on an infrared perfect absorber," Journal of Physics D-Applied Physics, vol. 45, p. 205102, May 23 2012.

  15. Direct MC conversion of absorbed dose to graphite to absorbed dose to water for 60Co radiation.

    PubMed

    Lye, J E; Butler, D J; Franich, R D; Harty, P D; Oliver, C P; Ramanathan, G; Webb, D V; Wright, T

    2013-06-01

    The ARPANSA calibration service for (60)Co gamma rays is based on a primary standard graphite calorimeter that measures absorbed dose to graphite. Measurements with the calorimeter are converted to the absorbed dose to water using the calculation of the ratio of the absorbed dose in the calorimeter to the absorbed dose in a water phantom. ARPANSA has recently changed the basis of this calculation from a photon fluence scaling method to a direct Monte Carlo (MC) calculation. The MC conversion uses an EGSnrc model of the cobalt source that has been validated against water tank and graphite phantom measurements, a step that is required to quantify uncertainties in the underlying interaction coefficients in the MC code. A comparison with the Bureau International des Poids et Mesures (BIPM) as part of the key comparison BIPM.RI(I)-K4 showed an agreement of 0.9973 (53).

  16. Shock absorber operates over wide range

    NASA Technical Reports Server (NTRS)

    Creasy, W. K.; Jones, J. C.

    1965-01-01

    Piston-type hydraulic shock absorber, with a metered damping system, operates over a wide range of kinetic energy loading rates. It is used for absorbing shock and vibration on mounted machinery and heavy earth-moving equipment.

  17. 21 CFR 872.6050 - Saliva absorber.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... absorber is a device made of paper or cotton intended to absorb moisture from the oral cavity during dental... manufacturing practice requirements of the quality system regulation in part 820 of this chapter, with...

  18. Possible Quantum Absorber Effects in Cortical Synchronization

    NASA Astrophysics Data System (ADS)

    Kämpf, Uwe

    The Wheeler-Feynman transactional "absorber" approach was proposed originally to account for anomalous resonance coupling between spatio-temporally distant measurement partners in entangled quantum states of so-called Einstein-Podolsky-Rosen paradoxes, e.g. of spatio-temporal non-locality, quantum teleportation, etc. Applied to quantum brain dynamics, however, this view provides an anticipative resonance coupling model for aspects of cortical synchronization and recurrent visual action control. It is proposed to consider the registered activation patterns of neuronal loops in so-called synfire chains not as a result of retarded brain communication processes, but rather as surface effects of a system of standing waves generated in the depth of visual processing. According to this view, they arise from a counterbalance between the actual input's delayed bottom-up data streams and top-down recurrent information-processing of advanced anticipative signals in a Wheeler-Feynman-type absorber mode. In the framework of a "time-loop" model, findings about mirror neurons in the brain cortex are suggested to be at least partially associated with temporal rather than spatial mirror functions of visual processing, similar to phase conjugate adaptive resonance-coupling in nonlinear optics.

  19. Improving the laboratory monitoring of absorbent oil

    SciTech Connect

    V.S. Shved; S.S. Sychev; I.V. Safina; S.A. Klykov

    2009-05-15

    The performance of absorbent coal tar oil is analyzed as a function of the constituent and group composition. The qualitative and quantitative composition of the oil that ensures the required absorbent properties is determined. Operative monitoring may be based on absorbent characteristics that permit regulation of the beginning and end of regeneration.

  20. Spectral estimators of absorbed photosynthetically active radiation in corn canopies

    NASA Technical Reports Server (NTRS)

    Gallo, K. P.; Daughtry, C. S. T.; Bauer, M. E.

    1985-01-01

    Most models of crop growth and yield require an estimate of canopy leaf area index (LAI) or absorption of radiation. Relationships between photosynthetically active radiation (PAR) absorbed by corn canopies and the spectral reflectance of the canopies were investigated. Reflectance factor data were acquired with a Landsat MSS band radiometer. From planting to silking, the three spectrally predicted vegetation indices examined were associated with more than 95 percent of the variability in absorbed PAR. The relationships developed between absorbed PAR and the three indices were evaluated with reflectance factor data acquired from corn canopies planted in 1979 through 1982. Seasonal cumulations of measured LAI and each of the three indices were associated with greater than 50 percent of the variation in final grain yields from the test years. Seasonal cumulations of daily absorbed PAR were associated with up to 73 percent of the variation in final grain yields. Absorbed PAR, cumulated through the growing season, is a better indicator of yield than cumulated leaf area index. Absorbed PAR may be estimated reliably from spectral reflectance data of crop canopies.

  1. Spectral estimators of absorbed photosynthetically active radiation in corn canopies

    NASA Technical Reports Server (NTRS)

    Gallo, K. P.; Daughtry, C. S. T.; Bauer, M. E.

    1984-01-01

    Most models of crop growth and yield require an estimate of canopy leaf area index (LAI) or absorption of radiation. Relationships between photosynthetically active radiation (PAR) absorbed by corn canopies and the spectral reflectance of the canopies were investigated. Reflectance factor data were acquired with a LANDSAT MSS band radiometer. From planting to silking, the three spectrally predicted vegetation indices examined were associated with more than 95% of the variability in absorbed PAR. The relationships developed between absorbed PAR and the three indices were evaluated with reflectance factor data acquired from corn canopies planted in 1979 through 1982. Seasonal cumulations of measured LAI and each of the three indices were associated with greater than 50% of the variation in final grain yields from the test years. Seasonal cumulations of daily absorbed PAR were associated with up to 73% of the variation in final grain yields. Absorbed PAR, cumulated through the growing season, is a better indicator of yield than cumulated leaf area index. Absorbed PAR may be estimated reliably from spectral reflectance data of crop canopies.

  2. Static and dynamic polarizability and the Stark and blackbody-radiation frequency shifts of the molecular hydrogen ions H2+, HD+, and D2+

    NASA Astrophysics Data System (ADS)

    Schiller, S.; Bakalov, D.; Bekbaev, A. K.; Korobov, V. I.

    2014-05-01

    We calculate the dc Stark effect for three molecular hydrogen ions in the nonrelativistic approximation. The effect is calculated both in dependence on the rovibrational state and in dependence on the hyperfine state. We discuss special cases and approximations. We also calculate the ac polarizabilities for several rovibrational levels and therefrom evaluate accurately the blackbody radiation shift, including the effects of excited electronic states. The results enable the detailed evaluation of certain systematic shifts of the transitions frequencies for the purpose of ultrahigh-precision optical, microwave, or radio-frequency spectroscopy in ion traps.

  3. Numerical Sensitivity Analysis of a Composite Impact Absorber

    NASA Astrophysics Data System (ADS)

    Caputo, F.; Lamanna, G.; Scarano, D.; Soprano, A.

    2008-08-01

    This work deals with a numerical investigation on the energy absorbing capability of structural composite components. There are several difficulties associated with the numerical simulation of a composite impact-absorber, such as high geometrical non-linearities, boundary contact conditions, failure criteria, material behaviour; all those aspects make the calibration of numerical models and the evaluation of their sensitivity to the governing geometrical, physical and numerical parameters one of the main objectives of whatever numerical investigation. The last aspect is a very important one for designers in order to make the application of the model to real cases robust from both a physical and a numerical point of view. At first, on the basis of experimental data from literature, a preliminary calibration of the numerical model of a composite impact absorber and then a sensitivity analysis to the variation of the main geometrical and material parameters have been developed, by using explicit finite element algorithms implemented in the Ls-Dyna code.

  4. Porcelain enamel neutron absorbing material

    DOEpatents

    Iverson, Daniel C.

    1990-02-06

    A porcelain enamel composition as a neutron absorbing material can be prepared of a major proportion by weight of a cadmium compound and a minor proportion of compounds of boron, lithium and silicon. These compounds in the form of a porcelain enamel coating or layer on several alloys has been found to be particularly effective in enhancing the nuclear safety of equipment for use in the processing and storage of fissile material. The composition of the porcelain enamel coating can be tailored to match the coefficient of thermal expansion of the equipment to be coated and excellent coating adhesion can be achieved.

  5. Porcelain enamel neutron absorbing material

    DOEpatents

    Iverson, D.C.

    1987-11-20

    A porcelain enamel composition as a neutron absorbing material can be prepared of a major proportion by weight of a cadmium compound and a minor proportion of compound of boron, lithium and silicon. These compounds in the form of a porcelain enamel coating or layer on several alloys has been found to be particularly effective in enhancing the nuclear safety of equipment for use in the processing and storage of fissile material. The composition of the porcelain enamel coating can be tailored to match the coefficient of thermal expansion of the equipment to be coated and excellent coating adhesion can be achieved. 2 figs.

  6. Porcelain enamel neutron absorbing material

    DOEpatents

    Iverson, Daniel C.

    1990-01-01

    A porcelain enamel composition as a neutron absorbing material can be prepared of a major proportion by weight of a cadmium compound and a minor proportion of compounds of boron, lithium and silicon. These compounds in the form of a porcelain enamel coating or layer on several alloys has been found to be particularly effective in enhancing the nuclear safety of equipment for use in the processing and storage of fissile material. The composition of the porcelain enamel coating can be tailored to match the coefficient of thermal expansion of the equipment to be coated and excellent coating adhesion can be achieved.

  7. Effects of climate and lifeform on dry matter yield (epsilon) from simulations using BIOME BGC. [ecosystem process model for vegetation biomass production using daily absorbed photosynthetically active radiation

    NASA Technical Reports Server (NTRS)

    Hunt, E. R., Jr.; Running, Steven W.

    1992-01-01

    An ecosystem process simulation model, BIOME-BGC, is used in a sensitivity analysis to determine the factors that may cause the dry matter yield (epsilon) and annual net primary production to vary for different ecosystems. At continental scales, epsilon is strongly correlated with annual precipitation. At a single location, year-to-year variation in net primary production (NPP) and epsilon is correlated with either annual precipitation or minimum air temperatures. Simulations indicate that forests have lower epsilon than grasslands. The most sensitive parameter affecting forest epsilon is the total amount of living woody biomass, which affects NPP by increasing carbon loss by maintenance respiration. A global map of woody biomass should significantly improve estimates of global NPP using remote sensing.

  8. Carbon dioxide absorbents for rebreather diving.

    PubMed

    Pennefather, John

    2016-09-01

    Firstly I would like to thank SPUMS members for making me a Life Member of SPUMS; I was surprised and greatly honoured by the award. I also want to confirm and expand on the findings on carbon dioxide absorbents reported by David Harvey et al. For about 35 years, I was the main player in deciding which absorbent went into Australian Navy and Army diving sets. On several occasions, suppliers of absorbents to the anaesthesia market tried to supply the Australian military market. On no occasion did they provide absorbent that came close to the minimum absorbent capacity required, generally being 30-40% less efficient than diving-grade absorbents. Because I regard lives as being more important than any likely dollar saving, the best absorbent was always selected unless two suppliers provided samples with the same absorbent capacity. On almost every occasion, there was a clear winner and cost was never considered. I suggest the same argument for the best absorbent should be used by members and their friends who dive using rebreather sets. I make this point because of my findings on a set that was brought to me after the death of its owner. The absorbent was not the type or grain size recommended by the manufacturer of the set and did not resemble any of the diving grade absorbents I knew of. I suspected by its appearance that it was anaesthetic grade absorbent. When I tested the set, the absorbent system failed very quickly so it is likely that carbon dioxide toxicity contributed to his death. The death was not the subject of an inquest and I have no knowledge of how the man obtained the absorbent. Possibly there was someone from an operating theatre staff who unintentionally caused their friend's death by supplying him with 'borrowed absorbent'. I make this point as I would like to discourage members from making a similar error.

  9. High-Resolution Modeling of the Predictability of Convective Systems, and Influences by Absorbing Aerosols Over Northern India and the Himalayas Foothills During Boreal Summer

    NASA Technical Reports Server (NTRS)

    Kim, Kyu-Myong; Lau, William K.-M.; Tao, Wei-Kuo; Shi, Jainn; Tan, Qian; Chin, Mian; Matsui, Toshihisa; Bian, Huisheng

    2011-01-01

    The Himalayas foothills region (HFR) is an important component of the South Asian monsoon. To the south, the HFR borders the fertile, populous, and heavily polluted Indo-Gangetic Plain (IGP). To the north, it rises to great height (approx. 4-5 km) to the Tibetan Plateau over a distance of less than 100 km. The HFR itself consists of complex mountainous terrain, with strong orographic forcing for precipitation. During the late spring and early summer, dust aerosol from the Thar and Middle East deserts , as well as moisture from the Arabian Sea were transported to the western part of the western part of the IGP and foothills spurs pre-monsoon severe thunderstorm over the region. During the monsoon season (mid June -August) convection from the Bay of Bengal, spread along the foothills northwestward to northern Pakistan. Recent climate model studies and preliminary observations have indicted not only the importance of dynamical forcing of precipitation in the HFR, but also possible strong impacts by the dense aerosols, from both local sources, and remote transport, that blanket the IGP from late spring up to the onset of the monsoon in June, and during monsoon breaks in July. In this work, we use the NASA Unified Weather Research and Forecasting (Nu-WRF) model to study the predictability ( 1-7 days) South Asian monsoon rainfall system. Results of 7 -day forecast experiments using an embedded domain of 27 km and 9 km resolution were conducted for the period June 11- July 15, 2008, with and without aerosol forcing are carried out to assess the intrinsic predictability of rainfall over the HFR, and possible impacts by aerosol direct effect, and possible connection of large-scale South Asian monsoon system.

  10. High-resolution modeling of the influences of absorbing aerosols on rainfall over northern India and the Himalaya foothills during boreal summer

    NASA Astrophysics Data System (ADS)

    Kim, K.; Lau, W. K.; Tao, W.; Shi, J. J.; Tan, Q.; Chin, M.; Matsui, T.; Kemp, E. M.; Peters-Lidard, C. D.

    2012-12-01

    High elevation and steep topography of Tibetan Plateau and the Himalayas foothills regions are important components of the South Asian summer monsoon system. Strong orographic forcing combined with abundant moisture from the Arabian Sea and the Bay of Bengal and aerosols stacked up against the southern slope of the Tibetan Plateau produce complex physical and dynamical effects on monsoon rainfall and circulation. In this work, we use the NASA Unified Weather Research and Forecasting (Nu-WRF) model to study the effect of aerosol radiative forcing on the short-term predictability (1-7 days) of the South Asian monsoon rainfall system. Two sets of 7-day forecasting experiments were conducted with and without aerosol radiative forcing. Each set consists of 34 7-day forcasts with initial conditions from daily reanalysis and GEOS-5 aerosol distribution (only for aerosol run) from June 11- July 14, 2008. Nu-WRF, without aerosol forcing captures the horizontal distribution of 7-day mean precipitation reasonably well, but it tends to over-estimates rainfall over the central India. The biases are especially larger in the upwind side of the western Ghats and northeast India and Bangladesh. Preliminary results show that inclusion of aerosol radiative forcing and interaction with dynamics reduces rainfall over the Indo-Gangetic plain where aerosol loadinng is high, but enhances rainfall downstream of the prevailing monsoon flow in the southern slope of Tibetan Plateau, especially over the northeast India and foothills regions, consistent with the EHP hypothesis. Effect of aerosol radiative forcing is small during the first two days of forecasts. Rainfall anomalies generated by atmospheric feedback induced by aerosol radiative forcing becomes statistically significant and large enough to be separable from growing model biases after three days of simulation. The results indicate the inclusion of aerosol radiative forcing may improve short-term (4-7 day) forecasting skill in

  11. Assessment of the accuracy of an MCNPX-based Monte Carlo simulation model for predicting three-dimensional absorbed dose distributions.

    PubMed

    Titt, U; Sahoo, N; Ding, X; Zheng, Y; Newhauser, W D; Zhu, X R; Polf, J C; Gillin, M T; Mohan, R

    2008-08-21

    In recent years, the Monte Carlo method has been used in a large number of research studies in radiation therapy. For applications such as treatment planning, it is essential to validate the dosimetric accuracy of the Monte Carlo simulations in heterogeneous media. The AAPM Report no 105 addresses issues concerning clinical implementation of Monte Carlo based treatment planning for photon and electron beams, however for proton-therapy planning, such guidance is not yet available. Here we present the results of our validation of the Monte Carlo model of the double scattering system used at our Proton Therapy Center in Houston. In this study, we compared Monte Carlo simulated depth doses and lateral profiles to measured data for a magnitude of beam parameters. We varied simulated proton energies and widths of the spread-out Bragg peaks, and compared them to measurements obtained during the commissioning phase of the Proton Therapy Center in Houston. Of 191 simulated data sets, 189 agreed with measured data sets to within 3% of the maximum dose difference and within 3 mm of the maximum range or penumbra size difference. The two simulated data sets that did not agree with the measured data sets were in the distal falloff of the measured dose distribution, where large dose gradients potentially produce large differences on the basis of minute changes in the beam steering. Hence, the Monte Carlo models of medium- and large-size double scattering proton-therapy nozzles were valid for proton beams in the 100 MeV-250 MeV interval.

  12. Warm Absorbers in the ROSAT Spectra of Quasars

    NASA Technical Reports Server (NTRS)

    Fiore, Fabrizio

    1998-01-01

    We present two ROSAT PSPC observations of the radio-loud, lobe-dominated quasar 3C 351, which shows an 'ionized absorber' in its X-ray spectrum. The factor 1.7 change in flux in the approx. 2 years between the observations allows a test of of models for this ionized absorber. The absorption feature at approx. 0.7 keV (quasar frame) is present in both spectra but with a lower optical depth when the source intensity - and hence the ionizing flux at the absorber - is higher, in accordance with a simple, single-zone, equilibrium photoionization model. Detailed modeling confirms this agreement quantitatively. The maximum response time of 2 years allows us to limit the gas density: n(sub e) greater than 2 x 10(exp 4)cm(exp -3); and the distance of the ionized gas from the central source R less than 19 pc. This produces a strong test for a photoionized absorber in 3C 351: a factor 2 flux change in approx. 1 week in this source must show non-equilibrium effects in the ionized absorber.

  13. A polarization-independent broadband terahertz absorber

    SciTech Connect

    Shi, Cheng; Zang, XiaoFei E-mail: ymzhu@usst.edu.cn; Wang, YiQiao; Chen, Lin; Cai, Bin; Zhu, YiMing E-mail: ymzhu@usst.edu.cn

    2014-07-21

    A highly efficient broadband terahertz absorber is designed, fabricated, and experimentally as well as theoretically evaluated. The absorber comprises a heavily doped silicon substrate and a well-designed two-dimensional grating. Due to the destructive interference of waves and diffraction, the absorber can achieve over 95% absorption in a broad frequency range from 1 to 2 THz and for angles of incidence from 0° to 60°. Such a terahertz absorber is also polarization-independent due to its symmetrical structure. This omnidirectional and broadband absorber have potential applications in anti-reflection coatings, imaging systems, and so on.

  14. The foot as a shock absorber.

    PubMed

    Salathé, E P; Arangio, G A; Salathé, E P

    1990-01-01

    A mathematical analysis of the deformation of the foot is developed to determine the role that stretch of ligaments and tendons plays in absorbing shock following impact. Our analysis is based on an anatomical biomechanical model that includes each of the bones of the foot. We calculate the time course of the deflection of the joints and the elongation of the ligaments and tendons and determine the ground reaction force acting on the heel. Quasi-linear viscoelastic theory is used for soft tissue constitutive relationships. With biomechanical data selected from the literature, we obtain a vertical force impact peak of 8000 N, occurring at 16 ms following heel strike. This is of higher magnitude and shorter duration than is found experimentally, as is to be expected, since we did not include the heel pad in our model and we assumed that the impact surface was ideally rigid.

  15. Cascaded Perforates as One-Dimensional, Bulk Absorbers

    NASA Technical Reports Server (NTRS)

    Parrott, T. L.; Jones, M. G.

    2006-01-01

    Porous cell honeycomb liners for aircraft engine nacelles offer the possibility of exploiting extended reaction effects to improve liner attenuation bandwidth as generally attributed to the performance of bulk absorbers. This paper describes an analytical procedure, starting with an impedance prediction model for a single perforated plate, to estimate the bulk-absorber parameters for a cascade of such perforates - a first step to modeling a porous wall honeycomb structure. The objective is to build confidence in a lumped element impedance model, when applied to a uniformly-spaced set of porous plates to predict its .bulk. absorber properties. The model is based upon a modified version of the two-parameter flow resistance model of the form A + BV(sub inc), where A and B are physics-based, semi-empirical parameters that are adjusted to provide an optimum fit to a composite dataset from three plate porosities of 2.5, 5 and 10%. The composite dataset is achieved by reformulating the two-parameter flow resistance model into a .reduced pressure drop coefficient. dependency on perforate hole Reynolds number. The resulting impedance model is employed to calculate surface impedance spectra for N and 2N-layer perforate cascades. The well-known two-thickness method for experimental determination of bulk-absorber parameters is then applied to these .synthesized. data sets to predict the characteristic impedance and propagation constant for the perforate cascades. These results are then compared with experimental results reported in a companion paper.

  16. Mapping liquid distribution in absorbent incontinence products.

    PubMed

    Landeryou, M A; Yerworth, R J; Cottenden, A M

    2003-01-01

    This paper reviews methods available for mapping the distribution of fluid in incontinence pad materials to assist with evaluating existing products and developing new ones, and to provide data for building and validating predictive models. Specifically, the following technologies are considered and their strengths and limitations described: discrete sensors based on conductance, temperature or optical measurements, optical imaging, gravimetric methods, X-ray imaging and magnetic resonance imaging. It is suggested that the ideal method would enable fluid distribution to be mapped in three dimensions with good spatial and time resolution in single materials and composite structures of simple and complex geometries under static and dynamic mechanical loading. It would also allow liquid to be mapped in products when worn by users. It is concluded that, although each existing method meets some of these requirements, and each requirement is met, at least reasonably well, by at least one method, improved techniques are needed. The particular need for methods that can provide some measurement of liquid saturation within absorbent products, both in the laboratory and in real use, is highlighted. In many cases, simple methods used appropriately are sufficient to elicit the important aspects of liquid transport and storage within absorbent products.

  17. Acoustic metamaterial panels based on multi frequency vibration absorbers

    NASA Astrophysics Data System (ADS)

    Shi, Chao; Sun, Hongwei; Hu, Xiaolei; Gu, Jinliang

    2016-04-01

    Presented here is a new metamaterial panel based on multi-frequency vibration absorbers for broadband vibration absorption. The proposed metamaterial panel consists of a uniform isotropic panel and small two-mass spring-mass-damper subsystem many locations along the panel to act as multi-frequency vibration absorbers. The existence of two stopbands is demonstrated using a model based on averaging material properties over a cell length and a model based on finite element modeling and the Bloch-Floquet theory for periodic structures. For a finite metamaterial panel, because these two idealized models can not be used for finite panels and/or elastic waves having short wavelengths, a finite-element method is used for detailed modeling and analysis. The concepts of negative effective stiffness is explained in detail. For an incoming wave with a frequency in one of the two stopbands, the absorbers are excited to vibrate in their optical modes to create shear forces to straighten the panel and stop the wave propagation. For an incoming wave with a frequency outside of but between the two stopbands, it can be efficiently damped out by the damper with these mass of each absorber. Hence, the two stopbands are connected in to a wide stopband. Numerical examples validate the concept and show that the structures boundary conditions do not have significant influence on the absorption of high-frequency waves. However, for absorption of low-frequency waves, the structures boundary conditions and resonance frequencies and the location and spatial distribution of absorbers need to be considered in design, and it is better to use heavier masses for absorbers.

  18. System size expansion for systems with an absorbing state.

    PubMed

    Di Patti, Francesca; Azaele, Sandro; Banavar, Jayanth R; Maritan, Amos

    2011-01-01

    The well-known van Kampen system size expansion, while of rather general applicability, is shown to fail to reproduce some qualitative features of the time evolution for systems with an absorbing state, apart from a transient initial time interval. We generalize the van Kampen ansatz by introducing a new prescription leading to non-Gaussian fluctuations around the absorbing state. The two expansion predictions are explicitly compared for the infinite range voter model with speciation as a paradigmatic model with an absorbing state. The new expansion, both for a finite size system in the large time limit and at finite time in the large size limit, converges to the exact solution as obtained in a numerical implementation using the Gillespie algorithm. Furthermore, the predicted lifetime distribution is shown to have the correct asymptotic behavior.

  19. Inferring Absorbing Organic Carbon Content from AERONET Data

    NASA Technical Reports Server (NTRS)

    Arola, A.; Schuster, G.; Myhre, G.; Kazadzis, S.; Dey, S.; Tripathi, S. N.

    2011-01-01

    Black carbon, light-absorbing organic carbon (often called brown carbon) and mineral dust are the major light-absorbing aerosols. Currently the sources and formation of brown carbon aerosol in particular are not well understood. In this study we estimated globally the amount of light absorbing organic carbon and black carbon from AERONET measurements. We find that the columnar absorbing organic carbon (brown carbon) levels in biomass burning regions of South-America and Africa are relatively high (about 15-20 magnesium per square meters during biomass burning season), while the concentrations are significantly lower in urban areas in US and Europe. However, we estimated significant absorbing organic carbon amounts from the data of megacities of newly industrialized countries, particularly in India and China, showing also clear seasonality with peak values up to 30-35 magnesium per square meters during the coldest season, likely caused by the coal and biofuel burning used for heating. We also compared our retrievals with the modeled organic carbon by global Oslo CTM for several sites. Model values are higher in biomass burning regions than AERONET-based retrievals, while opposite is true in urban areas in India and China.

  20. Absorbable plate strength loss during molding.

    PubMed

    Ballard, Tiffany N S; Kelly, Kevin J; Zaydfudim, Victor; Walcutt, Noah L; Lahijani, Soheil S; Shack, R Bruce; Thayer, Wesley P

    2010-05-01

    Bioabsorbable plating systems play an integral role in cranial vault remodeling. After experiencing a case of plate failure requiring emergent reexploration, we investigated the potential causes. We hypothesize that extended submersion in the molding bath during plate preparation might advance the rate of hydrolysis and compromise plate structural integrity. Using an absorbable poly-D/L-lactic acid plating system, we assessed the effect of extended submersion on plate strength and stiffness when loaded in a cantilever fashion and with pure tension. We assessed these differences with the Student t test and linear regression modeling. We also generated a computer model of the plates for finite element analysis. When left in the molding bath for extended periods, the plates changed color and lost strength. After 5 minutes, 30% of maximum plate load capacity was lost in a cantilever beam test (P < 0.001) consistent with use of a 15% thinner plate. Tensile testing revealed the initial elastic modulus of 6.42 +/- 0.13 GPa decreased 16% to 5.41 +/- 0.50 GPa after 5 minutes of submersion (P = 0.027). The changes in plate strength and elastic modulus both worsened with increased submersion times. Finite element analysis of the plates also predicted clinically significant increases in plate deviation under normal loading conditions. Our study demonstrates that extended submersion of absorbable plates during molding results in a significant loss of plate strength and stiffness. Further, our computer model predicts that these changes could result in an unacceptable plate deviation under normal loading conditions. Together, these data caution against overmolding of plates to avoid compromising their structural integrity.

  1. Liquid crystal tunable metamaterial absorber.

    PubMed

    Shrekenhamer, David; Chen, Wen-Chen; Padilla, Willie J

    2013-04-26

    We present an experimental demonstration of electronically tunable metamaterial absorbers in the terahertz regime. By incorporation of active liquid crystal into strategic locations within the metamaterial unit cell, we are able to modify the absorption by 30% at 2.62 THz, as well as tune the resonant absorption over 4% in bandwidth. Numerical full-wave simulations match well to experiments and clarify the underlying mechanism, i.e., a simultaneous tuning of both the electric and magnetic response that allows for the preservation of the resonant absorption. These results show that fundamental light interactions of surfaces can be dynamically controlled by all-electronic means and provide a path forward for realization of novel applications.

  2. Oxalate: Effect on calcium absorbability

    SciTech Connect

    Heaney, R.P.; Weaver, C.M. )

    1989-10-01

    Absorption of calcium from intrinsically labeled Ca oxalate was measured in 18 normal women and compared with absorption of Ca from milk in these same subjects, both when the test substances were ingested in separate meals and when ingested together. Fractional Ca absorption from oxalate averaged 0.100 +/- 0.043 when ingested alone and 0.140 +/- 0.063 when ingested together with milk. Absorption was, as expected, substantially lower than absorption from milk (0.358 +/- 0.113). Nevertheless Ca oxalate absorbability in these women was higher than we had previously found for spinach Ca. When milk and Ca oxalate were ingested together, there was no interference of oxalate in milk Ca absorption and no evidence of tracer exchange between the two labeled Ca species.

  3. Absorbing ice model of interstellar grains.

    NASA Technical Reports Server (NTRS)

    Swamy, K. S. K.; Jackson, W. M.; Donn, B. D.

    1971-01-01

    Extinction curves have been calculated for Mie scattering by grains with a refractive index m equals to n - ik, where n was between 1.3 and 2.0 and k varied from 0 to 0.5. A good fit for the observed interstellar extinction in the wavelength region of 0.1 to 2.0 microns was obtained for particles with a radius of 0.1 micron and m equal to 1.3 - 0.2i. Inclusion of the changes in the refractive index in the vacuum ultraviolet region due to the strong absorptions of methane, ammonia and water does not appreciably alter these results. Theoretical extinction curves for the composite medium of H2O, NH3, CH4, and graphite show a general agreement with the observed interstellar reddening curve over the whole spectral range, in addition to producing kinks in the far-ultraviolet region.

  4. Energy harvesting from an autoparametric vibration absorber

    NASA Astrophysics Data System (ADS)

    Yan, Zhimiao; Hajj, Muhammad R.

    2015-11-01

    The combined control and energy harvesting characteristics of an autoparametric vibration absorber consisting of a base structure subjected to the external force and a cantilever beam with a tip mass are investigated. The piezoelectric sheets are attached to the cantilever beam to convert the vibrations of the base structure into electrical energy. The coupled nonlinear representative model is developed by using the extended Hamiton’s principle. The effects of the electrical load resistance on the frequency and damping ratio of the cantilever beam are analyzed. The impacts of the external force and load resistance on the structural displacements of the base structure and the beam and on the level of harvested energy are determined. The results show that the initial conditions have a significant impact on the system’s response. The relatively high level of energy harvesting is not necessarily accompanied with the minimum displacements of the base structure.

  5. Magnetic field effects on microwave absorbing materials

    NASA Technical Reports Server (NTRS)

    Goldberg, Ira; Hollingsworth, Charles S.; Mckinney, Ted M.

    1991-01-01

    The objective of this program was to gather information to formulate a microwave absorber that can work in the presence of strong constant direct current (DC) magnetic fields. The program was conducted in four steps. The first step was to investigate the electrical and magnetic properties of magnetic and ferrite microwave absorbers in the presence of strong magnetic fields. This included both experimental measurements and a literature survey of properties that may be applicable to finding an appropriate absorbing material. The second step was to identify those material properties that will produce desirable absorptive properties in the presence of intense magnetic fields and determine the range of magnetic field in which the absorbers remain effective. The third step was to establish ferrite absorber designs that will produce low reflection and adequate absorption in the presence of intense inhomogeneous static magnetic fields. The fourth and final step was to prepare and test samples of such magnetic microwave absorbers if such designs seem practical.

  6. Light Absorbing Aerosols in Mexico City

    NASA Astrophysics Data System (ADS)

    Marley, N. A.; Kelley, K. L.; Kilaparty, P. S.; Gaffney, J. S.

    2008-12-01

    The direct effects of aerosol radiative forcing has been identified by the IPCC as a major uncertainty in climate modeling. The DOE Megacity Aerosol Experiment-Mexico City (MAX-Mex), as part of the MILAGRO study in March of 2006, was undertaken to reduce these uncertainties by characterization of the optical, chemical, and physical properties of atmospheric aerosols emitted from this megacity environment. Aerosol samples collected during this study using quartz filters were characterized in the uv-visible-infrared by using surface spectroscopic techniques. These included the use of an integrating sphere approach combined with the use of Kubelka-Munk theory to obtain aerosol absorption spectra. In past work black carbon has been assumed to be the only major absorbing species in atmospheric aerosols with an broad band spectral profile that follows a simple inverse wavelength dependence. Recent work has also identified a number of other absorbing species that can also add to the overall aerosol absorption. These include primary organics from biomass and trash burning and secondary organic aerosols including nitrated PAHs and humic-like substances, or HULIS. By using surface diffuse reflection spectroscopy we have also obtained spectra in the infrared that indicate significant IR absorption in the atmospheric window-region. These data will be presented and compared to spectra of model compounds that allow for evaluation of the potential importance of these species in adding strength to the direct radiative forcing of atmospheric aerosols. This work was supported by the Office of Science (BER), U.S. Department of Energy, Grant No. DE-FG02-07ER64327 as part of the Atmospheric Science Program.

  7. Croconic acid - An absorber in the Venus clouds?

    NASA Technical Reports Server (NTRS)

    Hartley, Karen K.; Wolff, Andrew R.; Travis, Larry D.

    1989-01-01

    The absorbing species responsible for the UV cloud features and pale yellow hue of the Venus clouds is presently suggested to be the carbon monoxide-polymer croconic acid, which strongly absorbs in the blue and near-UV. Laboratory absorption-coefficient measurements of a dilute solution of croconic acid in sulfuric acid are used as the bases of cloud-scattering models; the Venus planetary albedo's observed behavior in the blue and near-UV are noted to be qualitatively reproduced. Attention is given to a plausible croconic acid-production mechanism for the Venus cloudtop region.

  8. The dynamics analysis of a ferrofluid shock absorber

    NASA Astrophysics Data System (ADS)

    Yao, Jie; Chang, Jianjun; Li, Decai; Yang, Xiaolong

    2016-03-01

    The paper presents a shock absorber using three magnets as the inertial mass. Movement of the inertial mass inside a cylindrical body filled with ferrofluid will lead to a viscous dissipation of the oscillating system energy. The influence of a dumbbell-like ferrofluid structure on the energy dissipation is considered and the magnetic restoring force is investigated by experiment and theoretical calculation. A theoretical model of the hydrodynamics and energy dissipation processes is developed, which includes the geometrical characteristics of the body, the fluid viscosity, and the external magnetic field. The theory predicts the experimental results well under some condition. The shock absorber can be used in spacecraft technology.

  9. Energy Deposition and Radiological Studies for the LBNF Hadron Absorber

    SciTech Connect

    Rakhno, I. L.; Mokhov, N. V.; Tropin, I. S.; Eidelman, Y. I.

    2015-06-25

    Results of detailed Monte Carlo energy deposition and radiological studies performed for the LBNF hadron absorber with the MARS15 code are described. The model of the entire facility, that includes a pion-production target, focusing horns, target chase, decay channel, hadron absorber system – all with corresponding radiation shielding – was developed using the recently implemented ROOT-based geometry option in the MARS15 code. Both normal operation and accidental conditions were studied. Results of detailed thermal calculations with the ANSYS code helped to select the most viable design options.

  10. Experimental characterization of a nonlinear vibration absorber using free vibration

    NASA Astrophysics Data System (ADS)

    Tang, Bin; Brennan, M. J.; Gatti, G.; Ferguson, N. S.

    2016-04-01

    Knowledge of the nonlinear characteristics of a vibration absorber is important if its performance is to be predicted accurately when connected to a host structure. This can be achieved theoretically, but experimental validation is necessary to verify the modelling procedure and assumptions. This paper describes the characterization of such an absorber using a novel experimental procedure. The estimation method is based on a free vibration test, which is appropriate for a lightly damped device. The nonlinear absorber is attached to a shaker which is operated such that the shaker works in its mass-controlled regime, which means that the shaker dynamics, which are also included in the measurement, are considerably simplified, which facilitates a simple estimation of the absorber properties. From the free vibration time history, the instantaneous amplitude and instantaneous damped natural frequency are estimated using the Hilbert transform. The stiffness and damping of the nonlinear vibration absorber are then estimated from these quantities. The results are compared with an analytical solution for the free vibration of the nonlinear system with cubic stiffness and viscous damping, which is also derived in the paper using an alternative approach to the conventional perturbation methods. To further verify the approach, the results are compared with a method in which the internal forces are balanced at each measured instant in time.

  11. Use of negative complex potential as absorbing potential

    NASA Astrophysics Data System (ADS)

    Ge, Jiu-Yuan; Zhang, John Z. H.

    1998-01-01

    Exact numerical calculation shows that the use of negative complex potential (NCP) significantly improves the efficiency of wavefunction absorption over that of negative imaginary potential (NIP) in scattering applications. The improvement in absorption is especially significant in the case of low energy scattering with de Broglie wavelength larger than the length of absorbing potential. The addition of a negative real potential to the pure imaginary potential speeds up the absorption of wavefunction by effectively shortening its de Broglie wavelength. Explicit TD numerical calculation for a one-dimensional model demonstrates the effectiveness of the NCP and shows that the reflection from the absorbing potential can effectively be eliminated by using optimized absorbing parameters for the energy in question. In addition, comparison of the exact numerical calculation with semiclassical WKB analysis casts a serious doubt on the quantitative value of using WKB analysis at low energies with de Broglie wavelengths much larger than the absorbing length and/or for polynomial absorbing potentials higher than linear.

  12. Molecular dynamic simulations of the water absorbency of hydrogels.

    PubMed

    Ou, Xiang; Han, Qiang; Dai, Hui-Hui; Wang, Jiong

    2015-09-01

    A polymer gel can imbibe solvent molecules through surface tension effect. When the solvent happens to be water, the gel can swell to a large extent and forms an aggregate called hydrogel. The large deformation caused by such swelling makes it difficult to study the behaviors of hydrogels. Currently, few molecular dynamic simulation works have been reported on the water absorbing mechanism of hydrogels. In this paper, we first use molecular dynamic simulation to study the water absorbing mechanism of hydrogels and propose a hydrogel-water interface model to study the water absorbency of the hydrogel surface. Also, the saturated water content and volume expansion rate of the hydrogel are investigated by building a hydrogel model with different cross-linking degree and by comparing the water absorption curves under different temperatures. The sample hydrogel model used consists of Polyethylene glycol diglycidyl ether (PEGDGE) as epoxy and the Jeffamine, poly-oxy-alkylene-amines, as curing agent. The conclusions obtained are useful for further investigation on PEGDGE/Jeffamine hydrogel. Moreover, the simulation methods, including hydrogel-water interface modeling, we first propose are also suitable to study the water absorbing mechanism of other hydrogels.

  13. Constraining MHD Disk-Winds with X-ray Absorbers

    NASA Astrophysics Data System (ADS)

    Fukumura, Keigo; Tombesi, F.; Shrader, C. R.; Kazanas, D.; Contopoulos, J.; Behar, E.

    2014-01-01

    From the state-of-the-art spectroscopic observations of active galactic nuclei (AGNs) the robust features of absorption lines (e.g. most notably by H/He-like ions), called warm absorbers (WAs), have been often detected in soft X-rays (< 2 keV). While the identified WAs are often mildly blueshifted to yield line-of-sight velocities up to ~100-3,000 km/sec in typical X-ray-bright Seyfert 1 AGNs, a fraction of Seyfert galaxies such as PG 1211+143 exhibits even faster absorbers (v/ 0.1-0.2) called ultra-fast outflows (UFOs) whose physical condition is much more extreme compared with the WAs. Motivated by these recent X-ray data we show that the magnetically- driven accretion-disk wind model is a plausible scenario to explain the characteristic property of these X-ray absorbers. As a preliminary case study we demonstrate that the wind model parameters (e.g. viewing angle and wind density) can be constrained by data from PG 1211+143 at a statistically significant level with chi-squared spectral analysis. Our wind models can thus be implemented into the standard analysis package, XSPEC, as a table spectrum model for general analysis of X-ray absorbers.

  14. Absorbent product and articles made therefrom

    NASA Technical Reports Server (NTRS)

    Dawn, F. S.; Correale, J. V. (Inventor)

    1982-01-01

    A multilayer absorbent product for use in contact with the skin to absorb fluids is described. The product has a water pervious facing layer for contacting the skin, and a first fibrous wicking layer overlaying the water pervious layer. A first container section is defined by inner and outer layers of a water pervious wicking material in between a first absorbent mass and a second container section defined by inner and outer layers of a water pervious wicking material between what is disposed a second absorbent mass, and a liquid impermeable/gas permeable layer overlaying the second fibrous wicking layer.

  15. Metamaterial absorber with random dendritic cells

    NASA Astrophysics Data System (ADS)

    Zhu, Weiren; Zhao, Xiaopeng

    2010-05-01

    The metamaterial absorber composed of random dendritic cells has been investigated at microwave frequencies. It is found that the absorptivities come to be weaker and the resonant frequency get red shift as the disordered states increasing, however, the random metamaterial absorber still presents high absorptivity more than 95%. The disordered structures can help understanding of the metamaterial absorber and may be employed for practical design of infrared metamaterial absorber, which may play important roles in collection of radiative heat energy and directional transfer enhancement.

  16. Damping Performance of Taut Cables with Passive Absorbers Incorporating Inerters

    NASA Astrophysics Data System (ADS)

    Luo, Jiannan; Jiang, Jason Zheng; Macdonald, John H. G.

    2016-09-01

    As stay cables are prone to vibrations due to their low inherent damping, a common method to limit unwanted vibrations is to install a viscous damper normal to the cable near one of its supports. This paper investigates the potential performance improvement that can be delivered by a numbers of candidate absorbers that incorporate inerters. The inerter device is the true network dual of a spring, with the property that the force is proportional to the relative acceleration between its two terminals. A finite element taut cable model is used for this study. A specific cost function indicating the damping performance of a cable with an absorber attached is proposed. An optimisation of the performance is then carried out. Based on optimisation results, the best damping performance for each of the candidate absorber structures against a specific range of inertance values is presented.

  17. Scattering Properties of Heterogeneous Mineral Particles with Absorbing Inclusions

    NASA Technical Reports Server (NTRS)

    Dlugach, Janna M.; Mishchenko, Michael I.

    2015-01-01

    We analyze the results of numerically exact computer modeling of scattering and absorption properties of randomly oriented poly-disperse heterogeneous particles obtained by placing microscopic absorbing grains randomly on the surfaces of much larger spherical mineral hosts or by imbedding them randomly inside the hosts. These computations are paralleled by those for heterogeneous particles obtained by fully encapsulating fractal-like absorbing clusters in the mineral hosts. All computations are performed using the superposition T-matrix method. In the case of randomly distributed inclusions, the results are compared with the outcome of Lorenz-Mie computations for an external mixture of the mineral hosts and absorbing grains. We conclude that internal aggregation can affect strongly both the integral radiometric and differential scattering characteristics of the heterogeneous particle mixtures.

  18. On the undamped vibration absorber with cubic stiffness characteristics

    NASA Astrophysics Data System (ADS)

    Gatti, G.

    2016-09-01

    In order to improve the performance of a vibration absorber, a nonlinear spring can be used on purpose. This paper presents an analytical insight on the characteristics of an undamped nonlinear vibration absorber when it is attached to a linear spring-mass-damper oscillator. In particular, the nonlinear attachment is modelled as a Duffing's oscillator with a spring characteristics having a linear positive stiffness term plus a cubic stiffness term. The effects of the nonlinearity, mass ratio and frequency ratio are investigated based on an approximate analytical formulation of the amplitude-frequency equation. Comparisons to the linear case are shown in terms of the frequency response curves. The nonlinear absorber seems to show an improved robustness to mistuning respect to the corresponding linear device. However, such a better robustness may be limited by some instability of the expected harmonic response.

  19. Design of electromagnetic shock absorbers for automotive suspensions

    NASA Astrophysics Data System (ADS)

    Amati, Nicola; Festini, Andrea; Tonoli, Andrea

    2011-12-01

    Electromechanical dampers seem to be a valid alternative to conventional shock absorbers for automotive suspensions. They are based on linear or rotative electric motors. If they are of the DC-brushless type, the shock absorber can be devised by shunting its electric terminals with a resistive load. The damping force can be modified by acting on the added resistance. To supply the required damping force without exceeding in size and weight, a mechanical or hydraulic system that amplifies the speed is required. This paper illustrates the modelling and design of such electromechanical shock absorbers. This paper is devoted to describe an integrated design procedure of the electrical and mechanical parameters with the objective of optimising the device performance. The application to a C class front suspension car has shown promising results in terms of size, weight and performance.

  20. Device for absorbing mechanical shock

    DOEpatents

    Newlon, C.E.

    1979-08-29

    This invention is a comparatively inexpensive but efficient shock-absorbing device having special application to the protection of shipping and storage cylinders. In a typical application, two of the devices are strapped to a cylinder to serve as saddle-type supports for the cylinder during storage and to protect the cylinder in the event it is dropped during lifting or lowering operations. In its preferred form, the invention includes a hardwood plank whose grain runs in the longitudinal direction. The basal portion of the plank is of solid cross-section, whereas the upper face of the plank is cut away to form a concave surface fittable against the sidewall of a storage cylinder. The concave surface is divided into a series of segments by transversely extending, throughgoing relief slots. A layer of elastomeric material is positioned on the concave face, the elastomer being extrudable into slots when pressed against the segments by a preselected pressure characteristic of a high-energy impact. The compressive, tensile, and shear properties of the hardwood and the elastomer are utilized in combination to provide a surprisingly high energy-absorption capability.

  1. Device for absorbing mechanical shock

    DOEpatents

    Newlon, Charles E.

    1980-01-01

    This invention is a comparatively inexpensive but efficient shock-absorbing device having special application to the protection of shipping and storage cylinders. In a typical application, two of the devices are strapped to a cylinder to serve as saddle-type supports for the cylinder during storage and to protect the cylinder in the event it is dropped during lifting or lowering operations. In its preferred form, the invention includes a hardwood plank whose grain runs in the longitudinal direction. The basal portion of the plank is of solid cross-section, whereas the upper face of the plank is cut away to form a concave surface fittable against the sidewall of a storage cylinder. The concave surface is divided into a series of segments by transversely extending, throughgoing relief slots. A layer of elastomeric material is positioned on the concave face, the elastomer being extrudable into slots when pressed against the segments by a preselected pressure characteristic of a high-energy impact. The compressive, tensile, and shear properties of the hardwood and the elastomer are utilized in combination to provide a surprisingly high energy-absorption capability.

  2. Energy-harvesting shock absorber with a mechanical motion rectifier

    NASA Astrophysics Data System (ADS)

    Li, Zhongjie; Zuo, Lei; Kuang, Jian; Luhrs, George

    2013-02-01

    Energy-harvesting shock absorbers are able to recover the energy otherwise dissipated in the suspension vibration while simultaneously suppressing the vibration induced by road roughness. They can work as a controllable damper as well as an energy generator. An innovative design of regenerative shock absorbers is proposed in this paper, with the advantage of significantly improving the energy harvesting efficiency and reducing the impact forces caused by oscillation. The key component is a unique motion mechanism, which we called ‘mechanical motion rectifier (MMR)’, to convert the oscillatory vibration into unidirectional rotation of the generator. An implementation of a MMR-based harvester with high compactness is introduced and prototyped. A dynamic model is created to analyze the general properties of the motion rectifier by making an analogy between mechanical systems and electrical circuits. The model is capable of analyzing electrical and mechanical components at the same time. Both simulation and experiments are carried out to verify the modeling and the advantages. The prototype achieved over 60% efficiency at high frequency, much better than conventional regenerative shock absorbers in oscillatory motion. Furthermore, road tests are done to demonstrate the feasibility of the MMR shock absorber, in which more than 15 Watts of electricity is harvested while driving at 15 mph on a smooth paved road. The MMR-based design can also be used for other applications of vibration energy harvesting, such as from tall buildings or long bridges.

  3. Analysis and design of triple-band high-impedance surface absorber with periodic diversified impedance

    NASA Astrophysics Data System (ADS)

    Rui Zhang, Guo; Heng Zhou, Pei; Bin Zhang, Hui; Bo Zhang, Lin; Liang Xie, Jian; Jiang Deng, Long

    2013-10-01

    In this paper, a triple-band planar absorber with high-impedance surface (HIS) is designed and fabricated. The absorber structure is composed of polyurethane foam sandwiched between a lossy sheet of frequency selective surfaces (FSS) and a perfect electric conductor. The lossy FSS possesses different resistances in a periodic composite unit as compared with typical HIS absorber. Losses in the FSS are introduced by printing the periodic composite square ring pattern on blank stickers using various resistive inks. Physical mechanism of the HIS absorbers is analyzed by equivalent circuit model and electric field distribution studies. The proposed absorber with periodic composite units offers superimposed triple-band absorption as compared with that of the single units having single- or dual-band absorption characteristics. The reflection loss measurements show that the 90% absorption bandwidth of the HIS absorber is increased by 42% by the proposed composite periodic units.

  4. Existence, uniqueness and construction of the solution of the energy transfer problem in a rigid and non-convex blackbody with temperature-dependent thermal conductivity

    NASA Astrophysics Data System (ADS)

    da Gama, Rogério Martins Saldanha

    2015-10-01

    In this paper, we study the steady-state (coupled) conduction-radiation heat transfer phenomenon in a non-convex opaque blackbody with temperature-dependent thermal conductivity. The mathematical description consists of a nonlinear partial differential equation subjected to a nonlinear boundary condition involving an integral operator that is inherently associated with the non-convexity of the body. The unknown is the absolute temperature distribution. The problem is rewritten with the aid of a Kirchhoff transformation, giving rise to linear partial differential equation and a new unknown. An iterative procedure is proposed for constructing the solution of the problem by means of a sequence of problems, each of them with an equivalent minimum principle. Proofs of convergence as well as existence and uniqueness of the solution are presented. An error estimate, for each element of the sequence, is presented too.

  5. The relation between the bolometric flux and the blackbody temperature at the peak of type II bursts from the Rapid Burster

    NASA Technical Reports Server (NTRS)

    Lubin, Lori M.; Lewin, Walter H. G.; Dotani, Tadayasu; Oosterbroek, Tim; Mitsuda, Kazuhisa; Magnier, Eugene; Van Paradijs, Jan; Van Der Klis, Michiel

    1992-01-01

    During about 6 hr of Ginga observations of the Rapid Burster in August 1988, the source emitted type II bursts with durations between about 3 and about 35 s and with peak fluxes which varied by factors of about 5. The Rapid Burster was active in two bursting modes as defined by Marshall et al. (1979): mode I characterize by a burst energy distribution which is 'double-peaked' and mode II by a distribution which is 'single-peaked'. A study of the relationship between the maximum bolometric burst flux, F(max), and the associated blackbody temperature, Tc, shows that mode I bursts consistently show higher Tc values than bursts of mode II. These results, together with previous work, suggest that the relation between F(max) and Tc is dependent on mode. In mode I the color temperature is approximately independent of the burst peak flux, whereas in mode II the two properties are correlated.

  6. Absorbencies of six different rodent beddings: commercially advertised absorbencies are potentially misleading.

    PubMed

    Burn, C C; Mason, G J

    2005-01-01

    Moisture absorbency is one of the most important characteristics of rodent beddings for controlling bacterial growth and ammonia production. However, bedding manufacturers rarely provide information on the absorbencies of available materials, and even when they do, absorption values are usually expressed per unit mass of bedding. Since beddings are usually placed into cages to reach a required depth rather than a particular mass, their volumetric absorbencies are far more relevant. This study therefore compared the saline absorbencies of sawdust, aspen woodchips, two virgin loose pulp beddings (Alpha-Dri and Omega-Dri), reclaimed wood pulp (Tek-Fresh), and corncob, calculated both by volume and by mass. Absorbency per unit volume correlated positively with bedding density, while absorbency per unit mass correlated negatively. Therefore, the relative absorbencies of the beddings were almost completely reversed depending on how absorbency was calculated. By volume, corncob was the most absorbent bedding, absorbing about twice as much saline as Tek-Fresh, the least absorbent bedding. Conversely, when calculated by mass, Tek-Fresh appeared to absorb almost three times as much saline as the corncob. Thus, in practical terms the most absorbent bedding here was corncob, followed by the loose pulp beddings; and this is generally supported by their relatively low ammonia production as seen in previous studies. Many factors other than absorbency determine whether a material is suitable as a rodent bedding, and they are briefly mentioned here. However, manufacturers should provide details of bedding absorbencies in terms of volume, in order to help predict the relative absorbencies of the beddings in practical situations.

  7. An ultrathin dual-band metamaterial absorber

    NASA Astrophysics Data System (ADS)

    Zhang, Yong; Duan, Junping; Zhang, Wendong; Wang, Wanjun; Zhang, Binzhen

    2016-10-01

    The design and preparation of an ultrathin dual-band metamaterial absorber whose resonant frequency located at radar wave (20 GHz-60 GHz) is presented in this paper. The absorber is composed of a 2-D periodic sandwich featured with two concentric annuluses. The influence on the absorber's performance produced by resonant cell's structure size and material parameters was numerically simulated and analyzed based on the standard full wave finite integration technology in CST. Laser ablation process was adopted to prepare the designed absorber on epoxy resin board coated with on double plane of copper with a thickness that is 1/30 and 1/50 of the resonant wavelength at a resonant frequency of 30.51 GHz and 48.15 GHz. The full width at half maximum (FWHM) reached 2.2 GHz and 2.35 GHz and the peak of the absorptance reached 99.977%. The ultrathin absorber is nearly omnidirectional for all polarizations. The test results of prepared sample testify the designed absorber's excellent absorbing performance forcefully. The absorber expands inspirations of radar stealth in military domain due to its flexible design, cost-effective and other outstanding properties.

  8. 21 CFR 872.6050 - Saliva absorber.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Saliva absorber. 872.6050 Section 872.6050 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Miscellaneous Devices § 872.6050 Saliva absorber. (a) Identification. A...

  9. 21 CFR 872.6050 - Saliva absorber.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Saliva absorber. 872.6050 Section 872.6050 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Miscellaneous Devices § 872.6050 Saliva absorber. (a) Identification. A...

  10. [Absorbed doses in dental radiology].

    PubMed

    Bianchi, S D; Roccuzzo, M; Albrito, F; Ragona, R; Anglesio, S

    1996-01-01

    The growing use of dento-maxillo-facial radiographic examinations has been accompanied by the publication of a large number of studies on dosimetry. A thorough review of the literature is presented in this article. Most studies were carried out on tissue equivalent skull phantoms, while only a few were in vivo. The aim of the present study was to evaluate in vivo absorbed doses during Orthopantomography (OPT). Full Mouth Periapical Examination (FMPE) and Intraoral Tube Panoramic Radiography (ITPR). Measurements were made on 30 patients, reproducing clinical conditions, in 46 anatomical sites, with 24 intra- and 22 extra-oral thermoluminiscent dosimeters (TLDS). The highest doses were measured, in orthopantomography, at the right mandibular angle (1899 mu Gy) in FMPE on the right naso-labial fold (5640 mu Gy and in ITPR on the palatal surface of the left second upper molar (1936 mu Gy). Intraoral doses ranged from 21 mu Gy, in orthopantomography, to 4494 mu Gy in FMPE. Standard errors ranged from 142% in ITPR to 5% in orthopantomography. The highest rate of standard errors was found in FMPE and ITPR. The data collected in this trial are in agreement with others in major literature reports. Disagreements are probably due to different exam acquisition and data collections. Such differences, presented comparison in several sites, justify lower doses in FMPE and ITPR. Advantages and disadvantages of in vivo dosimetry of the maxillary region are discussed, the former being a close resemblance to clinical conditions of examination and the latter the impossibility of collecting values in depth of tissues. Finally, both ITPR and FMPE required lower doses than expected, and can be therefore reconsidered relative to their radiation risk.

  11. Helicopter rotor lag damping augmentation based on a radial absorber and Coriolis coupling

    NASA Astrophysics Data System (ADS)

    Byers, Lynn Karen

    A radial vibration absorber is proposed to augment rotor lag damping. Modeled as a discrete mass restrained by a damped spring and moving along the spanwise direction within the rotor blade, it introduces damping into the lag mode of the blade through strong Coriolis coupling. A two-degree-of-freedom model is developed and used to examine the effectiveness of the radial absorber in transferring damping to the rotor lag mode. Results demonstrate that it is possible to introduce a significant amount of damping in the lag mode with a relatively small absorber mass, and the corresponding amplitudes of 1/rev periodic motions are not excessively large. The lag mode damping and 1/rev motions are also compared with the results achieved for an embedded chordwise inertial damper. A classical six-degree-of-freedom aeromechanical stability analysis is augmented with two absorber cyclic degrees of freedom in the nonrotating frame to examine the effect of the radial absorber on aeromechanical stability characteristics. These results indicate that ground resonance instability is eliminated for the range of absorber parameters considered, and in most cases, the stability margins are significant. A rotor blade with a discrete radial vibration absorber is also analyzed to examine the effect of the absorber on rotor blade and hub loads. The rotor blade is modeled as an elastic beam undergoing flap and lag bending, with the absorber modeled as a discrete mass restrained by a damped spring, moving in the spanwise direction within the rotor blade. Results indicate that the addition of the absorber does not detrimentally affect the blade spanwise and root loads, as well as steady and vibratory hub loads. Finally, device concepts and implementation possibilities are considered for the embedded radial vibration absorber.

  12. Side branch absorber for exhaust manifold of two-stroke internal combustion engine

    SciTech Connect

    Harris, Ralph E; Broerman, III, Eugene L.; Bourn, Gary D

    2011-01-11

    A method of improving scavenging operation of a two-stroke internal combustion engine. The exhaust pressure of the engine is analyzed to determine if there is a pulsation frequency. Acoustic modeling is used to design an absorber. An appropriately designed side branch absorber may be attached to the exhaust manifold.

  13. Transient QED effects in absorbing dielectrics

    NASA Astrophysics Data System (ADS)

    Wubs, Martijn; Suttorp, L. G.

    2001-04-01

    The spontaneous-emission rate of a radiating atom reaches its time-independent equilibrium value after an initial transient regime. In this paper, we consider the associated relaxation effects of the spontaneous-decay rate of atoms in dispersive and absorbing dielectric media for atomic-transition frequencies near material resonances. A quantum mechanical description of such media is furnished by a damped-polariton model in which absorption is taken into account through coupling to a bath. We show how all field and matter operators in this theory can be expressed in terms of the bath operators at an initial time. The consistency of these solutions for the field and matter operators are found to depend on the validity of certain velocity sum rules. The transient effects in the spontaneous-decay rate are studied with the help of several specific models for the dielectric constant, which are shown to follow from the general theory by adopting particular forms of the bath coupling constant.

  14. Absorber Coatings for Mid-Infrared Astrophysics

    NASA Astrophysics Data System (ADS)

    Baker, Dahlia Anne; Wollack, Edward; Rostem, Karwan

    2017-01-01

    Control over optical response is an important aspect of instrument design for astrophysical imaging. Here we consider a mid-infrared absorber coating proposed for use on HIRMES (High Resolution Mid-Infrared Spectrometer), a cryogenic spectrometer which will fly on the SOFIA (Stratospheric Observatory for Infrared Astronomy) aircraft. The aim of this effort is to develop an absorptive coating for the 20-200 microns spectral range based on a graphene loaded epoxy binder (Epotek 377H) and glass microsphere scatterers (3M K1). The coatings electromagnetic response was modeled using a Matlab script and the glass microspheres were characterized by the measured size distribution, the dielectric constant, and the filling fraction. Images of the microspheres taken by a microscope were used to determine the size distribution with an ImageJ particle analysis program. Representative test samples for optical evaluation were fabricated for characterization via infrared Fourier transform spectroscopy. The optical tests will determine the material’s absorptance and reflectance. These test results will be compared to the modeled response.

  15. Thin film absorber for a solar collector

    DOEpatents

    Wilhelm, William G.

    1985-01-01

    This invention pertains to energy absorbers for solar collectors, and more particularly to high performance thin film absorbers. The solar collectors comprising the absorber of this invention overcome several problems seen in current systems, such as excessive hardware, high cost and unreliability. In the preferred form, the apparatus features a substantially rigid planar frame with a thin film window bonded to one planar side of the frame. An absorber in accordance with the present invention is comprised of two thin film layers that are sealed perimetrically. In a preferred embodiment, thin film layers are formed from a metal/plastic laminate. The layers define a fluid-tight planar envelope of large surface area to volume through which a heat transfer fluid flows. The absorber is bonded to the other planar side of the frame. The thin film construction of the absorber assures substantially full envelope wetting and thus good efficiency. The window and absorber films stress the frame adding to the overall strength of the collector.

  16. The nonlinear piezoelectric tuned vibration absorber

    NASA Astrophysics Data System (ADS)

    Soltani, P.; Kerschen, G.

    2015-07-01

    This paper proposes a piezoelectric vibration absorber, termed the nonlinear piezoelectric tuned vibration absorber (NPTVA), for the mitigation of nonlinear resonances of mechanical systems. The new feature of the NPTVA is that its nonlinear restoring force is designed according to a principle of similarity, i.e., the NPTVA should be an electrical analog of the nonlinear host system. Analytical formulas for the NPTVA parameters are derived using the homotopy perturbation method. Doing so, a nonlinear generalization of Den Hartog’s equal-peak tuning rule is developed for piezoelectric vibration absorbers.

  17. Performance of a Multifunctional Space Evaporator-Absorber-Radiator (SEAR)

    NASA Technical Reports Server (NTRS)

    Izenson, Michael G.; Chen, Weibo; Phillips, Scott; Chepko, Ariane; Bue, Grant; Quinn, Gregory

    2014-01-01

    The Space Evaporator-Absorber-Radiator (SEAR) is a nonventing thermal control subsystem that combines a Space Water Membrane Evaporator (SWME) with a Lithium Chloride Absorber Radiator (LCAR). The LCAR is a heat pump radiator that absorbs water vapor produced in the SWME. Because of the very low water vapor pressure at equilibrium with lithium chloride solution, the LCAR can absorb water vapor at a temperature considerably higher than the SWME, enabling heat rejection sufficient for most EVA activities by thermal radiation from a relatively small area radiator. Prior SEAR prototypes used a flexible LCAR that was designed to be installed on the outer surface of a portable life support system (PLSS) backpack. This paper describes a SEAR subsystem that incorporates a very compact LCAR. The compact, multifunctional LCAR is built in the form of thin panels that can also serve as the PLSS structural shell. We designed and assembled a 2 ft² prototype LCAR based on this design and measured its performance in thermal vacuum tests when supplied with water vapor by a SWME. These tests validated our models for SEAR performance and showed that there is enough area available on the PLSS backpack shell to enable rejection of metabolic heat from the LCAR. We used results of these tests to assess future performance potential and suggest approaches for integrating the SEAR system with future space suits.

  18. Performance of a Multifunctional Space Evaporator- Absorber-Radiator (SEAR)

    NASA Technical Reports Server (NTRS)

    Izenson, Michael G.; Chen, Weibo; Bue, Grant; Quinn, Gregory

    2013-01-01

    The Space Evaporator-Absorber-Radiator (SEAR) is a nonventing thermal control subsystem that combines a Space Water Membrane Evaporator (SWME) with a Lithium Chloride Absorber Radiator (LCAR). The LCAR is a heat pump radiator that absorbs water vapor produced in the SWME. Because of the very low water vapor pressure at equilibrium with lithium chloride solution, the LCAR can absorb water vapor at a temperature considerably higher than the SWME, enabling heat rejection by thermal radiation from a relatively small area radiator. Prior SEAR prototypes used a flexible LCAR that was designed to be installed on the outer surface of a portable life support system (PLSS) backpack. This paper describes a SEAR subsystem that incorporates a very compact LCAR. The compact, multifunctional LCAR is built in the form of thin panels that can also serve as the PLSS structural shell. We designed and assembled a 2 sq ft prototype LCAR based on this design and measured its performance in thermal vacuum tests when supplied with water vapor by a SWME. These tests validated our models for SEAR performance and showed that there is enough area available on the PLSS backpack shell to enable heat rejection from the LCAR.

  19. Design optimization of a damped hybrid vibration absorber

    NASA Astrophysics Data System (ADS)

    Cheung, Y. L.; Wong, W. O.; Cheng, L.

    2012-02-01

    In this article, the H∞ optimization design of a hybrid vibration absorber (HVA), including both passive and active elements, for the minimization of the resonant vibration amplitude of a single degree-of-freedom (sdof) vibrating structure is derived by using the fixed-points theory. The optimum tuning parameters are the feedback gain, the tuning frequency, damping and mass ratios of the absorber. The effects of these parameters on the vibration reduction of the primary structure are revealed based on the analytical model. Design parameters of both passive and active elements of the HVA are optimized for the minimization of the resonant vibration amplitude of the primary system. One of the inherent limitations of the traditional passive vibration absorber is that its vibration absorption is low if the mass ratio between the absorber mass and the mass of the primary structure is low. The proposed HVA overcomes this limitation and provides very good vibration reduction performance even at a low mass ratio. The proposed optimized HVA is compared to a recently published HVA designed for similar propose and it shows that the present design requires less energy for the active element of the HVA than the compared design.

  20. Vibration reduction in a tilting rotor using centrifugal pendulum vibration absorbers

    NASA Astrophysics Data System (ADS)

    Shi, Chengzhi; Shaw, Steven W.; Parker, Robert G.

    2016-12-01

    This paper investigates vibration reduction in a rigid rotor with tilting, rotational, and translational motions using centrifugal pendulum vibration absorbers (CPVAs). A linearized vibration model is derived for the system consisting of the rotor and multiple sets of absorbers tuned to different orders. Each group of absorbers lies in a given plane perpendicular to the rotor rotation axis. Gyroscopic system modal analysis is applied to derive the steady-state response of the absorbers and the rotor to external, rotor-order, periodic forces and torques with frequency mΩ, where Ω is the mean rotor speed and m is the engine order (rotor-order). It is found that an absorber group with tuning order m is effective at reducing the rotor translational, tilting, and rotational vibrations, provided certain conditions are met. When the periodic force and torque are caused by N substructures that are equally spaced around the rotor, the rotor translational and tilting vibrations at order j are addressed by two absorber groups with tuning orders jN±1. In this case, the rotor rotational vibration at order j can be attenuated by an absorber group with tuning order jN. The results show how the response depends on the load amplitudes and order, the rotor speed, and design parameters associated with the sets of absorbers, most importantly, their tuning, mass, and plane of placement. In the ideal case with zero damping and exact tuning of the absorber sets, the vibrations can be eliminated for a range of loads over which the linearized model holds. The response for systems with detuned absorbers is also determined, which is relevant to applications where small detuning is employed due to robustness issues, and to allow for a larger range of operating loads over which the absorbers are effective. The system also exhibits undesirable resonances very close to these tuning conditions, an issue that is difficult to resolve and deserves further investigation.

  1. Attenuation of external Bremsstrahlung in metallic absorbers

    SciTech Connect

    Dhaliwal, A.S.; Powar, M.S.; Singh, M. )

    1990-12-01

    In this paper attenuation of bremsstrahlung from {sup 147}Pm and {sup 170}Tm beta emitters has been studied in aluminum, copper, tin, and lead metallic absorbers. Bremsstrahlung spectra and mass attenuation coefficients for monoenergetic gamma rays are used to calculate theoretical attenuation curves. Magnetic deflection and beta stopping techniques are used to measure the integral bremsstrahlung intensities above 30 keV in different target thicknesses. Comparison of measured and calculated attenuation curves shows a good agreement for various absorbers, thus providing a test of this technique, which may be useful in understanding bremsstrahlung intensity buildup and in the design of optimum shielding for bremsstrahlung sources. It is found that the absorption of bremsstrahlung in metallic absorbers does not obey an exponential law and that absorbers act as energy filters.

  2. Energy absorber uses expanded coiled tube

    NASA Technical Reports Server (NTRS)

    Johnson, E. F.

    1972-01-01

    Mechanical shock mitigating device, based on working material to its failure point, absorbs mechanical energy by bending or twisting tubing. It functions under axial or tangential loading, has no rebound, is area independent, and is easy and inexpensive to build.

  3. Neutron absorbing coating for nuclear criticality control

    DOEpatents

    Mizia, Ronald E.; Wright, Richard N.; Swank, William D.; Lister, Tedd E.; Pinhero, Patrick J.

    2007-10-23

    A neutron absorbing coating for use on a substrate, and which provides nuclear criticality control is described and which includes a nickel, chromium, molybdenum, and gadolinium alloy having less than about 5% boron, by weight.

  4. Durability of Polymeric Glazing and Absorber Materials

    SciTech Connect

    Jorgensen, G.; Terwilliger, K.; Bingham, C.; Milbourne, M.

    2005-01-01

    The Solar Heating and Lighting Program has set the goal of reducing the cost of solar water heating systems by at least 50%. An attractive approach to such large cost reduction is to replace glass and metal parts with less-expensive, lighter-weight, more-integrated polymeric components. The key challenge with polymers is to maintain performance and assure requisite durability for extended lifetimes. The objective of this task is to quantify lifetimes through measurement of the optical and mechanical stability of candidate polymeric glazing and absorber materials. Polycarbonate sheet glazings, as proposed by two industry partners, have been tested for resistance to UV radiation with three complementary methods. Incorporation of a specific 2-mil thick UV-absorbing screening layer results in glazing lifetimes of at least 15 years; improved screens promise even longer lifetimes. Proposed absorber materials were tested for creep and embrittlement under high temperature, and appear adequate for planned ICS absorbers.

  5. Porous absorber for solar air heaters

    SciTech Connect

    Finch, J.A.

    1980-09-10

    A general discussion of the factors affecting solar collector performance is presented. Bench scale tests done to try to determine the heat transfer characteristics of various screen materials are explained. The design, performance, and evaluation of a crude collector with a simple screen stack absorber is treated. The more sophisticated absorber concept, and its first experimental approximation is examined. A short summary of future plans for the collector concept is included. (MHR)

  6. Multilayer Radar Absorbing Non-Woven Material

    NASA Astrophysics Data System (ADS)

    Dedov, A. V.; Nazarov, V. G.

    2016-06-01

    We study the electrical properties of multilayer radar absorbing materials obtained by adding nonwoven sheets of dielectric fibers with an intermediate layer of electrically conductive carbon fibers. Multilayer materials that absorb electromagnetic radiation in a wide frequency range are obtained by varying the content of the carbon fibers. The carbon-fiber content dependent mechanism of absorption of electromagnetic radiation by sheets and multilayer materials is considered.

  7. Non-absorbed Antibiotics for IBS

    DTIC Science & Technology

    2012-03-16

    absorbed antibiotic rifaximin for nonconstipated irritable bowel syndrome (IBS). This effort adds to the body of literature from other, smaller studies that...have demonstrated clinical efficacy for IBS with rifaximin . Non-absorbed antibiotics have been endorsed by the American College of Gastroenterology... rifaximin 400 mg three times daily for 10 days or placebo. During the initial 2 weeks of therapy and the subsequent 10 weeks of follow-up rifaximin

  8. Structured metal film as a perfect absorber.

    PubMed

    Xiong, Xiang; Jiang, Shang-Chi; Hu, Yu-Hui; Peng, Ru-Wen; Wang, Mu

    2013-08-07

    A new type of absorber, a four-tined fish-spear-like resonator (FFR), constructed by the two-photon polymerization process, is reported. An absorbance of more than 90% is experimentally realized and the resonance occurs in the space between the tines. Since a continuous layer of metallic thin film covers the structure, it is perfectly thermo- and electroconductive, which is the mostly desired feature for many applications.

  9. Light absorbing carbon emissions from commercial shipping

    NASA Astrophysics Data System (ADS)

    Lack, Daniel; Lerner, Brian; Granier, Claire; Baynard, Tahllee; Lovejoy, Edward; Massoli, Paola; Ravishankara, A. R.; Williams, Eric

    2008-07-01

    Extensive measurements of the emission of light absorbing carbon aerosol (LAC) from commercial shipping are presented. Vessel emissions were sampled using a photoacoustic spectrometer in the Gulf of Mexico region. The highest emitters (per unit fuel burnt) are tug boats, thus making significant contributions to local air quality in ports. Emission of LAC from cargo and non cargo vessels in this study appears to be independent of engine load. Shipping fuel consumption data (2001) was used to calculate a global LAC contribution of 133(+/-27) Ggyr-1, or ~1.7% of global LAC. This small fraction could have disproportionate effects on both air quality near port areas and climate in the Arctic if direct emissions of LAC occur in that region due to opening Arctic sea routes. The global contribution of this LAC burden was investigated using the MOZART model. Increases of 20-50 ng m-3 LAC (relative increases up to 40%) due to shipping occur in the tropical Atlantic, Indonesia, central America and the southern regions of South America and Africa.

  10. Absorbance changes of carotenoids in different solvents.

    PubMed

    Zang, L Y; Sommerburg, O; van Kuijk, F J

    1997-01-01

    Carotenoids are typically measured in tissues with the high performance liquid chromatography (HPLC) and quantitation is usually done by calibrating with stock solutions in solvents. Four carotenoids including lutein, zeaxanthin, lycopene and beta-carotene were dissolved in hexane and methanol respectively, and their absorbance characteristics were compared. Lutein shows absorbance spectra that are almost independent of solvents at various concentrations. Spectra of zeaxanthin, lycopene and beta-carotene were found to be more solvent-dependent. The absorbance of zeaxanthin at lambda max is about approximately 2 times larger in methanol than in hexane at the higher concentrations, and increased non-linearly with increasing concentration in hexane. The absorbance of lycopene at lambda max in hexane is approximately 4 fold larger than in methanol, but the absorbance of the methanol sample can be recovered by re-extracting this sample in hexane. The absorbance of beta-carotene in hexane is larger than in methanol, and increased linearly with increasing concentration. But beta-carotene showed a non-linear concentration effect in methanol. There are very small variations in lambda max for all four carotenoids between hexane and methanol, due to differences in molar extinction coefficients. The non-linear concentration effects for these carotenoids are probably due to differences in solubility leading to the formation of microcrystals. Thus, care should be taken with quantitation of tissue carotenoid values, when they depend on measurement of concentrations in stock solutions.

  11. Perfect terahertz absorber using fishnet based metafilm

    SciTech Connect

    Azad, Abul Kalam; Shchegolkov, Dmitry Yu; Chen, Houtong; Taylor, Antoinette; Smirnova, E I; O' Hara, John F

    2009-01-01

    We present a perfect terahertz (THz) absorber working for a broad-angle of incidence. The two fold symmetry of rectangular fishnet structure allows either complete absorption or mirror like reflection depending on the polarization of incident the THz beam. Metamaterials enable the ability to control the electromagnetic wave in a unique fashion by designing the permittivity or permeability of composite materials with desired values. Although the initial idea of metamaterials was to obtain a negative index medium, however, the evolution of metamaterials (MMs) offers a variety of practically applicable devices for controlling electromagnetic wave such as tunable filters, modulators, phase shifters, compact antenna, absorbers, etc. Terahertz regime, a crucial domain of the electromagnetic wave, is suffering from the scarcity of the efficient devices and might take the advantage of metamaterials. Here, we demonstrate design, fabrication, and characterization of a terahertz absorber based on a simple fishnet metallic film separated from a ground mirror plane by a dielectric spacer. Such absorbers are in particular important for bolometric terahertz detectors, high sensitivity imaging, and terahertz anechoic chambers. Recently, split-ring-resonators (SRR) have been employed for metamaterial-based absorbers at microwave and THz frequencies. The experimental demonstration reveals that such absorbers have absorptivity close to unity at resonance frequencies. However, the downside of these designs is that they all employ resonators of rather complicated shape with many fine parts and so they are not easy to fabricate and are sensitive to distortions.

  12. Impact resistance of fiber composites - Energy-absorbing mechanisms and environmental effects

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Sinclair, J. H.

    1985-01-01

    Energy absorbing mechanisms were identified by several approaches. The energy absorbing mechanisms considered are those in unidirectional composite beams subjected to impact. The approaches used include: mechanic models, statistical models, transient finite element analysis, and simple beam theory. Predicted results are correlated with experimental data from Charpy impact tests. The environmental effects on impact resistance are evaluated. Working definitions for energy absorbing and energy releasing mechanisms are proposed and a dynamic fracture progression is outlined. Possible generalizations to angle-plied laminates are described.

  13. Impact resistance of fiber composites: Energy absorbing mechanisms and environmental effects

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Sinclair, J. H.

    1983-01-01

    Energy absorbing mechanisms were identified by several approaches. The energy absorbing mechanisms considered are those in unidirectional composite beams subjected to impact. The approaches used include: mechanic models, statistical models, transient finite element analysis, and simple beam theory. Predicted results are correlated with experimental data from Charpy impact tests. The environmental effects on impact resistance are evaluated. Working definitions for energy absorbing and energy releasing mechanisms are proposed and a dynamic fracture progression is outlined. Possible generalizations to angle-plied laminates are described.

  14. Ultrathin and lightweight microwave absorbers made of mu-near-zero metamaterials

    PubMed Central

    Zhong, Shuomin; He, Sailing

    2013-01-01

    We present a theory of perfect absorption in a bilayer model composed of a mu-near-zero (MNZ) metamaterial (MM) absorbing layer on a metallic substrate. Our analytical solutions reveal that a MM layer with a large purely imaginary permeability and a moderate permittivity backed by a metallic plane has a zero reflection at normal incidence when the thickness is ultrathin. The impedance-mismatched metamaterial absorber (MA) can be 77.3% thinner than conventional impedance-matched MAs with the same material loss in order to get the same absorption. A microwave absorber using double-layered spiral MMs with a thickness of only about one percent of the operating wavelength is designed and realized. An absorption efficiency above 93% at 1.74 GHz is demonstrated experimentally at illumination angles up to 60 degrees. Our absorber is 98% lighter than traditional microwave absorbers made of natural materials working at the same frequencies. PMID:23803861

  15. Optimal design of a magneto-rheological brake absorber for torsional vibration control

    NASA Astrophysics Data System (ADS)

    Nguyen, Q. H.; Choi, S. B.

    2012-02-01

    This research presents an optimal design of a magneto-rheological (MR) brake absorber for torsional vibration control of a rotating shaft. Firstly, the configuration of an MR brake absorber for torsional vibration control of a rotating shaft system is proposed. Then, the braking torque of the MR brake is derived based on the Bingham plastic model of the MR fluid. By assuming that the behaviour of the MR brake absorber is similar to that of a dry friction torsional damper, the optimal braking torque to control the torsional vibration is determined and validated by simulation. The optimal design problem of the MR brake absorber is then developed and a procedure to solve the optimal problem is proposed. Based on the proposed optimal design procedure, the optimal design of a specific rotating shaft system is performed. Vibration control performance of the shaft system employing the optimized MR brake absorber is then investigated through simulation and discussion on the results is given.

  16. Method of absorbance correction in a spectroscopic heating value sensor

    SciTech Connect

    Saveliev, Alexei; Jangale, Vilas Vyankatrao; Zelepouga, Sergeui; Pratapas, John

    2013-09-17

    A method and apparatus for absorbance correction in a spectroscopic heating value sensor in which a reference light intensity measurement is made on a non-absorbing reference fluid, a light intensity measurement is made on a sample fluid, and a measured light absorbance of the sample fluid is determined. A corrective light intensity measurement at a non-absorbing wavelength of the sample fluid is made on the sample fluid from which an absorbance correction factor is determined. The absorbance correction factor is then applied to the measured light absorbance of the sample fluid to arrive at a true or accurate absorbance for the sample fluid.

  17. Synchronous and non-synchronous responses of systems with multiple identical nonlinear vibration absorbers

    NASA Astrophysics Data System (ADS)

    Issa, Jimmy S.; Shaw, Steven W.

    2015-07-01

    In this work we investigate the nonlinear dynamic response of systems composed of a primary inertia to which multiple identical vibration absorbers are attached. This problem is motivated by observations of systems of centrifugal pendulum vibration absorbers that are designed to reduce engine order torsional vibrations in rotating systems, but the results are relevant to translational systems as well. In these systems the total absorber mass is split into multiple equal masses for purposes of distribution and/or balance, and it is generally expected that the absorbers will act in unison, corresponding to a synchronous response. In order to capture nonlinear effects of the responses of the absorbers, specifically, their amplitude-dependent frequency, we consider them to possess nonlinear stiffness. The equations of motion for the system are derived and it is shown how one can uncouple the equations for the absorbers from that for the primary inertia, resulting in a system of identical resonators that are globally coupled. These symmetric equations are scaled for weak nonlinear effects, near resonant forcing, and small damping. The method of averaging is applied, from which steady-state responses and their stability are investigated. The response of systems with two, three, and four absorbers are considered in detail, demonstrating a rich variety of bifurcations of the synchronous response, resulting in responses with various levels of symmetry in which sub-groups of absorbers are mutually synchronous. It is also shown that undamped models with more than two absorbers possess a degenerate response, which is made robust by the addition of damping to the model. Design guidelines are proposed based on the nature of the system response, with the aim of minimizing the acceleration of the primary system. It is shown that the desired absorber parameters are selected so that the system achieves a stable synchronous response which does not undergo jumps via saddle

  18. Simulation on Vapor Flow in the Absorber/Evaporator of an Absorption Chiller

    NASA Astrophysics Data System (ADS)

    Suzuki, Hiroshi; Nagamoto, Wataru; Sugiyama, Takahide

    Two-dimensional numerical computation methodology for vapor flow in the absorber/ evaporator in an absorption chiller has been suggested and the effect of pitch ratio of cylinders in the absorber/evaporator has been discussed. Pseudo-diffusion effects of surfactants added to lithium bromide solution flowing along cylinders in the absorber were considered into liquid film model suggested in the previous study. From the results, the present model was found to agree well with experimental data in a rather wide range of the pressure in the present system. The present model effectively reduces the computational load for vapor flow in the absorber/evaporator including 176 cylinders. Near the top and bottom walls of the absorber/evaporator, the high velocity regions were observed and the recirculating regions were also found to be formed just inside of the high velocity regions. This high velocity region is intensified with pitch-to-diameter ratio decrease because the vapor flow penetrating from the back side of the absorber increases for the pressure drop increase of front side of the absorber.

  19. A comparison of the NPL and LNE-Cnam silver and copper fixed-point blackbody sources, and measurement of the silver/copper temperature interval

    NASA Astrophysics Data System (ADS)

    McEvoy, H. C.; Sadli, M.; Bourson, F.; Briaudeau, S.; Rougié, B.

    2013-12-01

    The silver and copper fixed-point blackbody sources of NPL were directly compared with those of LNE-Cnam using an IKE LP3 and an IKE LP5 at three wavelengths (650 nm, 795 nm and 903 nm). The two silver fixed points and the two copper fixed points were in excellent agreement with each other, with a difference of 11 mK for the silver and within 16 mK for the copper, with an expanded measurement uncertainty of between 10 mK and 20 mK depending on the pyrometer used. The temperature interval between the silver and copper freezing points was also measured using combinations of all four fixed points. The results with the NPL LP3 gave a value for the silver-copper temperature interval of 122.89 °C with an expanded uncertainty of 30 mK those with the LNE-Cnam LP5 gave a temperature interval of 122.87 °C also with an expanded uncertainty of 30 mK this compares with the ITS-90 value of 122.84 °C.

  20. Water absorbency by wool fibers: Hofmeister effect.

    PubMed

    Lo Nostro, Pierandrea; Fratoni, Laura; Ninham, Barry W; Baglioni, Piero

    2002-01-01

    Wool is a complex material, composed of cuticle and epicuticle cells, surrounded by a cell membrane complex. Wool fibers absorb moisture from air, and, once immersed in water, they take up considerable amounts of liquid. The water absorbency parameter can be determined from weight gain, according to a standard method, and used to quantify this phenomenon. In this paper we report a study on the water absorbency (or retention) of untreated wool fibers in the presence of aqueous 1 M salt solutions at 29 degrees C and a relative humidity of either 33% or 56%. The effect of anions was determined by selecting a wide range of different sodium salts, while the effect of cations was checked through some chlorides and nitrates. Our results show a significant specific ion and ion pair "Hofmeister" effects, that change the amount of water absorbed by the fibers. To understand this phenomenon, the water absorbency parameter (A(w)) is compared to different physicochemical parameters such as the lyotropic number, free energy of hydration of ions, molar surface tension increment, polarizability, refractive index increment, and molar refractivity. The data indicate that this Hofmeister phenomenon is controlled by dispersion forces that depend on the polarizability of ionic species, their adsorption frequencies, the solvent, and the substrate. These dispersion forces dominate the behavior in concentrated solutions. They are in accord with new developing theories of solutions and molecular interactions in colloidal systems that account for Hofmeister effects.

  1. Oxygen absorbers in food preservation: a review.

    PubMed

    Cichello, Simon Angelo

    2015-04-01

    The preservation of packaged food against oxidative degradation is essential to establish and improve food shelf life, customer acceptability, and increase food security. Oxygen absorbers have an important role in the removal of dissolved oxygen, preserving the colour, texture and aroma of different food products, and importantly inhibition of food spoilage microbes. Active packaging technology in food preservation has improved over decades mostly due to the sealing of foods in oxygen impermeable package material and the quality of oxygen absorber. Ferrous iron oxides are the most reliable and commonly used oxygen absorbers within the food industry. Oxygen absorbers have been transformed from sachets of dried iron-powder to simple self-adhesive patches to accommodate any custom size, capacity and application. Oxygen concentration can be effectively lowered to 100 ppm, with applications spanning a wide range of food products and beverages across the world (i.e. bread, meat, fish, fruit, and cheese). Newer molecules that preserve packaged food materials from all forms of degradation are being developed, however oxygen absorbers remain a staple product for the preservation of food and pharmaceutical products to reduce food wastage in developed nations and increased food security in the developing & third world.

  2. Basic Physical Applications and the Mathematical Development of a Glint Visual Threshold Domain Model

    DTIC Science & Technology

    2009-11-01

    having an absorbtance ratio ’nO..)’ of the absorbed to incident energy with a value less than unity. This means that the balance of the energy is...blackbody cavity. According to the principles of thermodynamics, the object will reach the temperature ’T’ of the cavity and remain at this...Reflectivity Characteristics of Eye Armor Surface *Kreith, Frank, Principles of Solar Engineering. Washington, DC, McGraw 10 The final segment of the

  3. Using absorbable chitosan hemostatic sponges as a promising surgical dressing.

    PubMed

    Huang, Xiaofei; Sun, Yongfu; Nie, Jingyi; Lu, Wentao; Yang, Ling; Zhang, Zhiliang; Yin, Hongping; Wang, Zhengke; Hu, Qiaoling

    2015-04-01

    As absorbable hemostatic dressings, chitosan with a deacetylation degree of 40% (CS-40) and 73% (CS-73) have been fabricated into sponges via a modified method. The hemostatic, biocompatible and biodegradable properties were evaluated through in vivo assays. In a hepatic hemorrhage model, the chitosan sponges, with excellent blood compatibility, achieved less blood loss than the gelation sponge (GS). In addition, CS-40 showed better hemostatic capability and biodegradability than CS-73. After implantation, a histological analysis indicated that CS-40 exhibited the best biodegradability, tissue regeneration and least tissue adhesion. By contrasting CS-40 and CS-73, the deacetylation degree is confirmed to be a key factor for the hemostatic effect, biodegradability, biocompatibility and tissue regeneration. Our overall results demonstrated the potential application of CS-40 for use in absorbable hemostatic dressings.

  4. Engineering absorption and blackbody radiation in the far-infrared with surface phonon polaritons on gallium phosphide

    SciTech Connect

    Streyer, W.; Law, S.; Rosenberg, A.; Wasserman, D.; Roberts, C.; Podolskiy, V. A.; Hoffman, A. J.

    2014-03-31

    We demonstrate excitation of surface phonon polaritons on patterned gallium phosphide surfaces. Control over the light-polariton coupling frequencies is demonstrated by changing the pattern periodicity and used to experimentally determine the gallium phosphide surface phonon polariton dispersion curve. Selective emission via out-coupling of thermally excited surface phonon polaritons is experimentally demonstrated. Samples are characterized experimentally by Fourier transform infrared reflection and emission spectroscopy, and modeled using finite element techniques and rigorous coupled wave analysis. The use of phonon resonances for control of emissivity and excitation of bound surface waves offers a potential tool for the exploration of long-wavelength Reststrahlen band frequencies.

  5. Incorporating piezoelectric energy harvester in tunable vibration absorber for application in multi-modal vibration reduction of a platform structure

    NASA Astrophysics Data System (ADS)

    Lee, Chun-Ying; Lin, Jia-Hong

    2017-02-01

    Tunable vibration absorber is an effective device to reduce the vibration of structure subjected to harmonic excitation. The vibration energy is transferred mostly to the absorber when the natural frequency of the absorber is tuned to the excitation frequency. In this study, a piezoelectric (PZT) transducer was incorporated into the absorber in order to harvest the vibration energy and still alleviate the vibration of a platform structure. The tuning in dynamic characteristics of the absorber was facilitated by controlling its tip mass. The design formulation of the absorber was presented with a single degree-of-freedom (SDOF) model having the equivalent parameters. In the meantime, an optimal electric load resistor was determined to maximize the power output from the PZT transducer. The experimental measurement validated the SDOF model with good accuracy both in the vibration response and the output electric voltage. Finally, the absorber was installed on a platform structure to investigate its vibration reduction and energy harvesting capability for the external disturbance frequency covering certain frequency span. With three resonance modes of the platform studied, the absorber was able to reduce more than 80% of its original vibration and harvest several folds of electric power comparing with the untuned absorber. Although the performance in vibration reduction was slightly influenced (<6%), the great increase in the electric energy harvested revealed the absorber design a good potential toward self-powered sensor or actuator applications.

  6. Non-Absorbable Gas Behavior in the Absorber/Evaporator of a Absorption Chiller

    NASA Astrophysics Data System (ADS)

    Suzuki, Hiroshi; Nagamoto, Wataru; Sugiyama, Takahide

    A two-dimensional numerical study on non-absorbable gas behavior in the absorber/evaporator of an absorption chiller has been performed. In the present study, the effect of the pitch-to-diameter ratio of a cylinder bundle in the absorber was highlighted. From the results, a sudden decrease of the overall heat transfer coefficient of the absorber was observed at a certain mean concentration of non-absorbable gas for each pitch-to-diameter ratio. Such a critical concentration was also found to decrease as the pitch-to- diameter ratio increased. The sudden decrease occurs due to the sudden disappearance of recirculating region, which is formed between the absorber and the evaporator, and where most of non-absorbable gas stays when it exists. As the pitch-to-diameter ratio increases, the recirculating region becomes weak because the velocity of the high velocity region supporting the recirculating flow decreases. Then, the critical mean concentration of non-absorbable gas is found to decrease as pitch-to-ratio increases.

  7. Optical analysis of solar energy tubular absorbers.

    PubMed

    Saltiel, C; Sokolov, M

    1982-11-15

    The energy absorbed by a solar energy tubular receiver element for a single incident ray is derived. Two types of receiver elements were analyzed: (1) an inner tube with an absorbing coating surrounded by a semitransparent cover tube, and (2) a semitransparent inner tube filled with an absorbing fluid surrounded by a semitransparent cover tube. The formation of ray cascades in the semitransparent tubes is considered. A numerical simulation to investigate the influence of the angle of incidence, sizing, thickness, and coefficient of extinction of the tubes was performed. A comparison was made between receiver elements with and without cover tubes. Ray tracing analyses in which rays were followed within the tubular receiver element as well as throughout the rest of the collector were performed for parabolic and circular trough concentrating collectors.

  8. Interference theory of metamaterial perfect absorbers.

    PubMed

    Chen, Hou-Tong

    2012-03-26

    The impedance matching to free space in metamaterial perfect absorbers has been believed to involve and rely on magnetic resonant response, with direct evidence provided by the anti-parallel surface currents in the metal structures. Here I present a different theoretical interpretation based on interference, which shows that the two layers of metal structures in metamaterial absorbers are linked only by multiple reflections with negligible near-field interactions or magnetic resonances. This is further supported by the out-of-phase surface currents derived at the interfaces of resonator array and ground plane through multiple reflections and superpositions. The theory developed here explains all features observed in narrowband metamaterial absorbers and therefore provides a profound understanding of the underlying physics.

  9. Translatory shock absorber for attitude sensors

    NASA Technical Reports Server (NTRS)

    Vonpragenau, G. L.; Morgan, I. T., Jr.; Kirby, C. A. (Inventor)

    1976-01-01

    A translatory shock absorber is provided for mounting an attitude sensor thereon for isolating a sensor from translatory vibrations. The translatory shock absorber includes a hollow block structure formed as one piece to form a parallelogram. The absorber block structure includes a movable top plate for supporting the attitude sensor and a fixed base plate with opposed side plates interposed between. At the junctions of the side plates, and the base and top plates, there are provided grooves which act as flexible hinges for attenuating translatory vibrations. A damping material is supported on a pedestal which is carried on the base plate between the side plates thereof. The top of the damping material rests against the bottom surface of the top plate for eliminating the resonant peaks of vibration.

  10. Absorber Materials at Room and Cryogenic Temperatures

    SciTech Connect

    F. Marhauser, T.S. Elliott, A.T. Wu, E.P. Chojnacki, E. Savrun

    2011-09-01

    We recently reported on investigations of RF absorber materials at cryogenic temperatures conducted at Jefferson Laboratory (JLab). The work was initiated to find a replacement material for the 2 Kelvin low power waveguide Higher Order Mode (HOM) absorbers employed within the original cavity cryomodules of the Continuous Electron Beam Accelerator Facility (CEBAF). This effort eventually led to suitable candidates as reported in this paper. Furthermore, though constrained by small funds for labor and resources, we have analyzed a variety of lossy ceramic materials, several of which could be usable as HOM absorbers for both normal conducting and superconducting RF structures, e.g. as loads in cavity waveguides and beam tubes either at room or cryogenic temperatures and, depending on cooling measures, low to high operational power levels.

  11. Optimization and engineering of microwave absorbers

    NASA Astrophysics Data System (ADS)

    Chen, Kuo-Liang

    1998-12-01

    In this thesis, a concerted effort has been made to study and evaluate the individual electromagnetic properties of the absorbing components including carbon black, conducting fibers, metal flakes, magnetic materials such as carbonyl iron, ferrite and the chiral type of micro- carbon coil. The study of the electromagnetic properties covers functions such as dielectric dissipation, random scattering effect at low and high frequencies, magnetic dissipation at high frequencies and also the effect of chirality for different angles of incidence. The results of these studies have been used in the design, engineering and optimization of the microwave absorbers. The objective of this thesis is to identify the absorption mechanism of each of various type of fillers and to study the synergic effect arising from a combination of these in a non-metallic host medium. This will help us in producing microwave absorbers suitable for broad band application with the advantages of light weight, having high strength and possessing good chemical resistance. The results from experimental measurements of various material combinations have been greatly influenced by the theoretical understanding of the absorption mechanism. Design of microwave absorbers is governed by the requirement of the users as well as the characteristics of the objects (targets) inferred by theoretical understanding and experimental data to arrive at the right formula. Finally a detailed quality control program has to be charted out reflecting both the electromagnetic as well as mechanical properties. This is done by carrying out the tests systematically on small samples and then proceeding to practical absorbers making use of the data compiled earlier on smaller samples. In this thesis, to modify all dielectric absorbing components including micro-carbon chirals to reduce the sensitivity of absorption for different incident angles is unprecedented topic.

  12. A physically based algorithm for non-blackbody correction of the cloud top temperature for the convective clouds

    NASA Astrophysics Data System (ADS)

    Wang, C.; Luo, Z. J.; Chen, X.; Zeng, X.; Tao, W.; Huang, X.

    2012-12-01

    Cloud top temperature is a key parameter to retrieval in the remote sensing of convective clouds. Passive remote sensing cannot directly measure the temperature at the cloud tops. Here we explore a synergistic way of estimating cloud top temperature by making use of the simultaneous passive and active remote sensing of clouds (in this case, CloudSat and MODIS). Weighting function of the MODIS 11μm band is explicitly calculated by feeding cloud hydrometer profiles from CloudSat retrievals and temperature and humidity profiles based on ECMWF ERA-interim reanalysis into a radiation transfer model. Among 19,699 tropical deep convective clouds observed by the CloudSat in 2008, the averaged effective emission level (EEL, where the weighting function attains its maximum) is at optical depth 0.91 with a standard deviation of 0.33. Furthermore, the vertical gradient of CloudSat radar reflectivity, an indicator of the fuzziness of convective cloud top, is linearly proportional to, d_{CTH-EEL}, the distance between the EEL of 11μm channel and cloud top height (CTH) determined by the CloudSat when d_{CTH-EEL}<0.6km. Beyond 0.6km, the distance has little sensitivity to the vertical gradient of CloudSat radar reflectivity. Based on these findings, we derive a formula between the fuzziness in the cloud top region, which is measurable by CloudSat, and the MODIS 11μm brightness temperature assuming that the difference between effective emission temperature and the 11μm brightness temperature is proportional to the cloud top fuzziness. This formula is verified using the simulated deep convective cloud profiles by the Goddard Cumulus Ensemble model. We further discuss the application of this formula in estimating cloud top buoyancy as well as the error characteristics of the radiative calculation within such deep-convective clouds.

  13. Quantum walk with one variable absorbing boundary

    NASA Astrophysics Data System (ADS)

    Wang, Feiran; Zhang, Pei; Wang, Yunlong; Liu, Ruifeng; Gao, Hong; Li, Fuli

    2017-01-01

    Quantum walks constitute a promising ingredient in the research on quantum algorithms; consequently, exploring different types of quantum walks is of great significance for quantum information and quantum computation. In this study, we investigate the progress of quantum walks with a variable absorbing boundary and provide an analytical solution for the escape probability (the probability of a walker that is not absorbed by the boundary). We simulate the behavior of escape probability under different conditions, including the reflection coefficient, boundary location, and initial state. Moreover, it is also meaningful to extend our research to the situation of continuous-time and high-dimensional quantum walks.

  14. OSCEE fan exhaust bulk absorber treatment evaluation

    NASA Technical Reports Server (NTRS)

    Bloomer, H. E.; Samanich, N. E.

    1980-01-01

    The acoustic suppression capability of bulk absorber material designed for use in the fan exhaust duct walls of the quiet clean short haul experiment engine (OCSEE UTW) was evaluated. The acoustic suppression to the original design for the engine fan duct which consisted of phased single degree-of-freedom wall treatment was tested with a splitter and also with the splitter removed. Peak suppression was about as predicted with the bulk absorber configuration, however, the broadband characteristics were not attained. Post test inspection revealed surface oil contamination on the bulk material which could have caused the loss in bandwidth suppression.

  15. Analysis of Energy-Absorbing Foundations.

    DTIC Science & Technology

    1978-12-15

    1ENN51YVAN&A 5TATL UNIV UNIVERSITY PARK DEPT OF ENGI-CYTC F/S 13/h ANALYSIS OF ENERGY -ABSORBING POUNDATIONS.(U) ECC 78 V H NEUBERT, S Ji YIN DNA01-78...C-0036 UNCLASSIFIED DNA-48OFP NL "M~ENOMOEE MIflfl END ______ 1 32 112.2 MICROCOPY RILSOLUTION TEST CHIART LELL ,NA 480 MIL ANALYSIS OF ENERGY ...8217 REPORT & PERIOD COVERED Final Report for Period ANALYSIS OF ENERGY -ABSORBING FOUNDATIONS I Dee 77-1S Dee 78 6. PERFORMING ORG, REPORT NUMBER 7AUTHOR

  16. Shock-Absorbent Ball-Screw Mechanism

    NASA Technical Reports Server (NTRS)

    Hirr, Otto A., Jr.; Meneely, R. W.

    1986-01-01

    Actuator containing two ball screws in series employs Belleville springs to reduce impact loads, thereby increasing life expectancy. New application of springs increases reliability of equipment in which ball screws commonly used. Set of three springs within lower screw of ball-screw mechanism absorbs impacts that result when parts reach their upper and lower limits of movement. Mechanism designed with Belleville springs as shock-absorbing elements because springs have good energy-to-volume ratio and easily stacked to attain any stiffness and travel.

  17. Radio-Absorbing Nanocoatings on Corrugated Surfaces

    NASA Astrophysics Data System (ADS)

    Antipov, V. B.; Potekaev, A. I.; Vorozhtsov, A. B.; Melentyev, S. V.; Tsyganok, Yu. I.

    2016-12-01

    The feasibility of producing protective radio-absorbing shielding materials on the basis of differently shaped surfaces with nanostructured coatings is investigated. Combinations of special nanostructured materials and technical solutions for the shape of the absorbing surface were tested, in order to create efficient nanocoatings. It is shown that the coatings of interest that meet the requirements of low reflection and high attenuation of transmitted radiation combined with low coating thickness can be developed, using corrugated surfaces. Corrugated chicken egg-packing cell samples with nanostructured carbon coatings were examined and found to allow for effective shielding of electromagnetic radiation and to exhibit minimum reflection coefficients as compared to construction materials.

  18. Timing the warm absorber in NGC 4051

    NASA Astrophysics Data System (ADS)

    Silva, C. V.; Uttley, P.; Costantini, E.

    2016-12-01

    We investigated, using spectral-timing analysis, the characterization of highly ionized outflows in Seyfert galaxies, the so-called warm absorbers. Here, we present our results of the extensive 600 ks of XMM-Newton archival observations of the bright and highly variable Seyfert 1 galaxy NGC 4051 whose spectrum has revealed a complex multicomponent wind. Making use of both RGS and EPIC-pn data, we performed a detailed analysis through a time-dependent photoionization code in combination with spectral and Fourier spectral-timing techniques. The source light curves and the warm absorber parameters obtained from the data were used to simulate the response of the gas to variations in the ionizing flux of the central source. The resulting time variable spectra were employed to predict the effects of the warm absorber on the time lags and coherence of the energy dependent light curves. We have found that, in the absence of any other lag mechanisms, a warm absorber with the characteristics of the one observed in NGC 4051, is able to produce soft lags, up to 100 s, on timescales of hours. The time delay is associated with the response of the gas to changes in the ionizing source, either by photoionization or radiative recombination, which is dependent on its density. The range of radial distances that, under our assumptions, yield longer time delays are distances r 0.3-1.0 × 1016 cm, and hence gas densities n 0.4-3.0 × 107 cm-3. Since these ranges are comparable to the existing estimates of the location of the warm absorber in NGC 4051, we suggest that it is likely that the observed X-ray time lags may carry a signature of the warm absorber response time to changes in the ionizing continuum. Our results show that the warm absorber in NGC 4051 does not introduce lags on the short timescales associated with reverberation, but will likely modify the hard continuum lags seen on longer timescales, which in this source have been measured to be on the order of 50 s. Hence, these

  19. Durability of Polymeric Glazing and Absorber Materials

    SciTech Connect

    Jorgensen, G.; Terwilliger, K.; Bingham, C.; Lindquist, C.; Milbourne, M.

    2005-11-01

    The Solar Heating and Lighting Program has set the goal of reducing the cost of solar water heating systems by at least 50%. An attractive approach to such large cost reduction is to replace glass and metal parts with less-expensive, lighter-weight, more-integrated polymeric components. The key challenge with polymers is to maintain performance and assure requisite durability for extended lifetimes. We have begun evaluation of several new UV-screened polycarbonate sheet glazing constructions. This has involved interactions with several major polymer industry companies to obtain improved candidate samples. Proposed absorber materials were tested for UV resistance, and appear adequate for unglazed ICS absorbers.

  20. Absorbed fractions for alpha-particles in tissues of cortical bone

    NASA Astrophysics Data System (ADS)

    Watchman, Christopher J.; Bolch, Wesley E.

    2009-10-01

    Bone-seeking alpha-particle emitting radionuclides are common health physics hazards. Additionally, they are under consideration as an option for therapeutic molecular radiotherapy applications. Current dose models do not account for energy or bone-site dependence as shown by alpha-particle absorbed fractions given in ICRP Publication 30. Energy-dependent, yet bone-site independent, alpha-particle absorbed fractions have been presented by the models of Stabin and Siegel (2003 Health Phys. 85 294-310). In this work, a chord-based computational model of alpha-particle transport in cortical bone has been developed that explicitly accounts for both the bone-site and particle-energy dependence of alpha-particle absorbed fractions in this region of the skeleton. The model accounts for energy deposition to three targets: cortical endosteum, haversian space tissues and cortical bone. Path length distributions for cortical bone given in Beddoe (1977 Phys. Med. Biol. 22 298-308) provided additional transport regions in the absorbed fraction calculation. Significant variations in absorbed fractions between different skeletal sites were observed. Differences were observed between this model and the absorbed fractions given in ICRP Publication 30, which varied by as much as a factor of 2.1 for a cortical bone surface source irradiating cortical endosteum.

  1. Synthesis and absorbing mechanism of two-layer microwave absorbers containing polycrystalline iron fibers and carbonyl iron

    NASA Astrophysics Data System (ADS)

    Ding, Qingwei; Zhang, Mingang; Zhang, Cunrui; Qian, Tianwei

    2013-04-01

    Polycrystalline iron fibers were fabricated by α-FeOOH fiber precursors. Two-layer microwave absorber had been prepared by as-prepared polycrystalline iron fibers and carbonyl iron. The structure, morphology and properties of the composites were characterized with X-ray diffraction, scanning electron microscope and Network Analyzer. The complex permittivity and reflection loss (dB) of the composites were measured employing vector network analyzer model PNA 3629D vector in the frequency range between 30 and 6000 MHz. The thickness effect of the carbonyl iron layer on the microwave loss properties of the composites was investigated. A possible microwave-absorbing mechanism of polycrystalline iron fibers/carbonyl iron composite was proposed. The polycrystalline iron fibers/carbonyl iron composite can find applications in suppression of electromagnetic interference, and reduction of radar signature.

  2. 21 CFR 880.6025 - Absorbent tipped applicator.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Absorbent tipped applicator. 880.6025 Section 880... Devices § 880.6025 Absorbent tipped applicator. (a) Identification. An absorbent tipped applicator is a device intended for medical purposes that consists of an absorbent swab on a wooden, paper, or...

  3. Hollow carbon spheres in microwaves: Bio inspired absorbing coating

    NASA Astrophysics Data System (ADS)

    Bychanok, D.; Li, S.; Sanchez-Sanchez, A.; Gorokhov, G.; Kuzhir, P.; Ogrin, F. Y.; Pasc, A.; Ballweg, T.; Mandel, K.; Szczurek, A.; Fierro, V.; Celzard, A.

    2016-01-01

    The electromagnetic response of a heterostructure based on a monolayer of hollow glassy carbon spheres packed in 2D was experimentally surveyed with respect to its response to microwaves, namely, the Ka-band (26-37 GHz) frequency range. Such an ordered monolayer of spheres mimics the well-known "moth-eye"-like coating structures, which are widely used for designing anti-reflective surfaces, and was modelled with the long-wave approximation. Based on the experimental and modelling results, we demonstrate that carbon hollow spheres may be used for building an extremely lightweight, almost perfectly absorbing, coating for Ka-band applications.

  4. Design of mid-infrared ultra-wideband metallic absorber based on circuit theory

    NASA Astrophysics Data System (ADS)

    Arik, Kamalodin; Abdollahramezani, Sajjad; Farajollahi, Saeed; Khavasi, Amin; Rejaei, Behzad

    2016-12-01

    An ultra-broadband absorber of light is proposed by using periodic array of ultra-thin metallic ribbons on top of a lossless quarter-wavelength dielectric spacer placed on a metallic reflector. We propose a fully analytical circuit model for the structure, and then the absorber is duly designed based on the impedance matching concept. As a result, normalized bandwidth of 99.5% is realized by the proposed absorbing structure in mid-infrared regime. Performing a numerical optimization algorithm, we could also reach to normalized bandwidth of 103%.

  5. The Cooling of a Liquid Absorber using a Small Cooler

    SciTech Connect

    Baynham, D.E.; Bradshaw, T.W.; Green, M.A.; Ishimoto, S.; Liggins, N.

    2005-08-24

    This report discusses the use of small cryogenic coolers for cooling the Muon Ionization Cooling Experiment (MICE) liquid cryogen absorbers. Since the absorber must be able contain liquid helium as well liquid hydrogen, the characteristics of the available 4.2 K coolers are used here. The issues associated with connecting two-stage coolers to liquid absorbers are discussed. The projected heat flows into an absorber and the cool-down of the absorbers using the cooler are presented. The warm-up of the absorber is discussed. Special hydrogen safety issues that may result from the use of a cooler on the absorbers are also discussed.

  6. Measured acoustic properties of variable and low density bulk absorbers

    NASA Technical Reports Server (NTRS)

    Dahl, M. D.; Rice, E. J.

    1985-01-01

    Experimental data were taken to determine the acoustic absorbing properties of uniform low density and layered variable density samples using a bulk absober with a perforated plate facing to hold the material in place. In the layered variable density case, the bulk absorber was packed such that the lowest density layer began at the surface of the sample and progressed to higher density layers deeper inside. The samples were placed in a rectangular duct and measurements were taken using the two microphone method. The data were used to calculate specific acoustic impedances and normal incidence absorption coefficients. Results showed that for uniform density samples the absorption coefficient at low frequencies decreased with increasing density and resonances occurred in the absorption coefficient curve at lower densities. These results were confirmed by a model for uniform density bulk absorbers. Results from layered variable density samples showed that low frequency absorption was the highest when the lowest density possible was packed in the first layer near the exposed surface. The layers of increasing density within the sample had the effect of damping the resonances.

  7. Energy scavenging strain absorber: application to kinetic dielectric elastomer generator

    NASA Astrophysics Data System (ADS)

    Jean-Mistral, C.; Beaune, M.; Vu-Cong, T.; Sylvestre, A.

    2014-03-01

    Dielectric elastomer generators (DEGs) are light, compliant, silent energy scavengers. They can easily be incorporated into clothing where they could scavenge energy from the human kinetic movements for biomedical applications. Nevertheless, scavengers based on dielectric elastomers are soft electrostatic generators requiring a high voltage source to polarize them and high external strain, which constitutes the two major disadvantages of these transducers. We propose here a complete structure made up of a strain absorber, a DEG and a simple electronic power circuit. This new structure looks like a patch, can be attached on human's wear and located on the chest, knee, elbow… Our original strain absorber, inspired from a sailing boat winch, is able to heighten the external available strain with a minimal factor of 2. The DEG is made of silicone Danfoss Polypower and it has a total area of 6cm per 2.5cm sustaining a maximal strain of 50% at 1Hz. A complete electromechanical analytical model was developed for the DEG associated to this strain absorber. With a poling voltage of 800V, a scavenged energy of 0.57mJ per cycle is achieved with our complete structure. The performance of the DEG can further be improved by enhancing the imposed strain, by designing a stack structure, by using a dielectric elastomer with high dielectric permittivity.

  8. Monte Carlo Simulation of Massive Absorbers for Cryogenic Calorimeters

    SciTech Connect

    Brandt, D.; Asai, M.; Brink, P.L.; Cabrera, B.; Silva, E.do Couto e; Kelsey, M.; Leman, S.W.; McArthy, K.; Resch, R.; Wright, D.; Figueroa-Feliciano, E.; /MIT

    2012-06-12

    There is a growing interest in cryogenic calorimeters with macroscopic absorbers for applications such as dark matter direct detection and rare event search experiments. The physics of energy transport in calorimeters with absorber masses exceeding several grams is made complex by the anisotropic nature of the absorber crystals as well as the changing mean free paths as phonons decay to progressively lower energies. We present a Monte Carlo model capable of simulating anisotropic phonon transport in cryogenic crystals. We have initiated the validation process and discuss the level of agreement between our simulation and experimental results reported in the literature, focusing on heat pulse propagation in germanium. The simulation framework is implemented using Geant4, a toolkit originally developed for high-energy physics Monte Carlo simulations. Geant4 has also been used for nuclear and accelerator physics, and applications in medical and space sciences. We believe that our current work may open up new avenues for applications in material science and condensed matter physics.

  9. Tuneable vibration absorber using acceleration and displacement feedback

    NASA Astrophysics Data System (ADS)

    Alujević, N.; Tomac, I.; Gardonio, P.

    2012-06-01

    This study is concerned with the analysis and design of a tuneable vibration absorber, which is composed by a flexible beam with a clamping block in the middle and two masses symmetrically mounted at the two ends. The free length of the beam is used to accommodate piezoelectric strain actuators. The two masses at the ends are equipped with inertial accelerometers. This arrangement is used to generate two independent acceleration feedback control loops that produce virtual mass effects, which shift the absorbing frequency of the device. Another arrangement is also studied where the two accelerometer outputs are time-integrated twice in order to implement displacement feedback loops that change the beam stiffness to shift the characteristic frequency of the device. The two feedback approaches are first analysed theoretically, using a mobility-impedance model, and then experimentally on a prototype absorber unit. The stability of the feedback loops is studied using the Nyquist criterion in order to estimate the limits on the tuneable range of frequencies which are set by the maximum stable feedback gains. The study indicates that the stability margins for the acceleration feedback loops substantially depend on the application of an appropriate low-pass filter. On the contrary, the implementation of displacement feedback gives better stability margins.

  10. Fast ionized X-ray absorbers in AGNs

    NASA Astrophysics Data System (ADS)

    Fukumura, K.; Tombesi, F.; Kazanas, D.; Shrader, C.; Behar, E.; Contopoulos, I.

    2016-05-01

    We investigate the physics of the X-ray ionized absorbers often identified as warm absorbers (WAs) and ultra-fast outflows (UFOs) in Seyfert AGNs from spectroscopic studies in the context of magnetically-driven accretion-disk wind scenario. Launched and accelerated by the action of a global magnetic field anchored to an underlying accretion disk around a black hole, outflowing plasma is irradiated and ionized by an AGN radiation field characterized by its spectral energy density (SED). By numerically solving the Grad-Shafranov equation in the magnetohydrodynamic (MHD) framework, the physical property of the magnetized disk-wind is determined by a wind parameter set, which is then incorporated into radiative transfer calculations with xstar photoionization code under heating-cooling equilibrium state to compute the absorber's properties such as column density N_H, line-of-sight (LoS) velocity v, ionization parameter ξ, among others. Assuming that the wind density scales as n ∝ r-1, we calculate theoretical absorption measure distribution (AMD) for various ions seen in AGNs as well as line spectra especially for the Fe Kα absorption feature by focusing on a bright quasar PG 1211+143 as a case study and show the model's plausibility. In this note we demonstrate that the proposed MHD-driven disk-wind scenario is not only consistent with the observed X-ray data, but also help better constrain the underlying nature of the AGN environment in a close proximity to a central engine.

  11. Tunable metamaterial dual-band terahertz absorber

    NASA Astrophysics Data System (ADS)

    Luo, C. Y.; Li, Z. Z.; Guo, Z. H.; Yue, J.; Luo, Q.; Yao, G.; Ji, J.; Rao, Y. K.; Li, R. K.; Li, D.; Wang, H. X.; Yao, J. Q.; Ling, F. R.

    2015-11-01

    We report a design of a temperature controlled tunable dual band terahertz absorber. The compact single unit cell consists of two nested closed square ring resonators and a layer metallic separated by a substrate strontium titanate (STO) dielectric layer. It is found that the absorber has two distinctive absorption peaks at frequencies 0.096 THz and 0.137 THz, whose peaks are attained 97% and 75%. Cooling the absorber from 400 K to 250 K causes about 25% and 27% shift compared to the resonance frequency of room temperature, when we cooling the temperature to 150 K, we could attained both the two tunabilities exceeding 53%. The frequency tunability is owing to the variation of the dielectric constant of the low-temperature co-fired ceramic (LTCC) substrate. The mechanism of the dual band absorber is attributed to the overlapping of dual resonance frequencies, and could be demonstrated by the distributions of the electric field. The method opens up avenues for designing tunable terahertz devices in detection, imaging, and stealth technology.

  12. Methods of calculating radiation absorbed dose.

    PubMed

    Wegst, A V

    1987-01-01

    The new tumoricidal radioactive agents being developed will require a careful estimate of radiation absorbed tumor and critical organ dose for each patient. Clinical methods will need to be developed using standard imaging or counting instruments to determine cumulated organ activities with tracer amounts before the therapeutic administration of the material. Standard MIRD dosimetry methods can then be applied.

  13. Moving core beam energy absorber and converter

    DOEpatents

    Degtiarenko, Pavel V.

    2012-12-18

    A method and apparatus for the prevention of overheating of laser or particle beam impact zones through the use of a moving-in-the-coolant-flow arrangement for the energy absorbing core of the device. Moving of the core spreads the energy deposition in it in 1, 2, or 3 dimensions, thus increasing the effective cooling area of the device.

  14. Composition for absorbing hydrogen from gas mixtures

    DOEpatents

    Heung, Leung K.; Wicks, George G.; Lee, Myung W.

    1999-01-01

    A hydrogen storage composition is provided which defines a physical sol-gel matrix having an average pore size of less than 3.5 angstroms which effectively excludes gaseous metal hydride poisons while permitting hydrogen gas to enter. The composition is useful for separating hydrogen gas from diverse gas streams which may have contaminants that would otherwise render the hydrogen absorbing material inactive.

  15. Shock absorbing mount for electrical components

    NASA Technical Reports Server (NTRS)

    Dillon, R. F., Jr.; Mayne, R. C. (Inventor)

    1975-01-01

    A shock mount for installing electrical components on circuit boards is described. The shock absorber is made of viscoelastic material which interconnects the electrical components. With this system, shocks imposed on one component of the circuit are not transmitted to other components. A diagram of a typical circuit is provided.

  16. How to build a molecular shock absorber.

    PubMed

    McGough, A

    1999-12-02

    Newly determined structures of the alpha-helical repeats that make up the key 'rod' domains of spectrin and alpha-actinin - which serve as spacers between their actin-binding domains - have provided important insights into how these proteins function as molecular shock absorbers in cells.

  17. Novel shock absorber features varying yield strengths

    NASA Technical Reports Server (NTRS)

    Geier, D. J.

    1964-01-01

    A shock absorbent webbing of partially drawn synthetic strands is arranged in sections of varying density related to the varying mass of the human body. This is contoured to protect the body at points of contact, when subjected to large acceleration or deceleration forces.

  18. Shock absorber protects motive components against overloads

    NASA Technical Reports Server (NTRS)

    1965-01-01

    Shock absorber with an output shaft, hollow gear, and a pair of springs forming a resilient driving connection between shaft and gear, operates when abnormally high torques are applied. This simple durable frictional device is valuable in rotating mechanisms subject to sudden overloads.

  19. Torus elements used in effective shock absorber

    NASA Technical Reports Server (NTRS)

    Cunningham, P.; Platus, D. L.

    1966-01-01

    Energy absorbing device forces torus elements to revolve annularly between two concentric tubes when a load is applied to one tube. Interference forces can be varied by using torus elements of different thicknesses. The device operates repeatedly in compression or tension, and under problems of large onset rate tolerance or structural overload.

  20. Aldehyde-containing urea-absorbing polysaccharides

    NASA Technical Reports Server (NTRS)

    Mueller, W. A.; Hsu, G. C.; Marsh, H. E., Jr. (Inventor)

    1977-01-01

    A novel aldehyde containing polymer (ACP) is prepared by reaction of a polysaccharide with periodate to introduce aldehyde groups onto the C2 - C3 carbon atoms. By introduction of ether and ester groups onto the pendant primary hydroxyl solubility characteristics are modified. The ACP is utilized to absorb nitrogen bases such as urea in vitro or in vivo.