Simple Models of the Spatial Distribution of Cloud Radiative Properties for Remote Sensing Studies

NASA Technical Reports Server (NTRS)

2004-01-01

This project aimed to assess the degree to which estimates of three-dimensional cloud structure can be inferred from a time series of profiles obtained at a point. The work was motivated by the desire to understand the extent to which high-frequency profiles of the atmosphere (e.g. ARM data streams) can be used to assess the magnitude of non-plane parallel transfer of radiation in thc atmosphere. We accomplished this by performing an observing system simulation using a large-eddy simulation and a Monte Carlo radiative transfer model. We define the 3D effect as the part of the radiative transfer that isn't captured by one-dimensional radiative transfer calculations. We assess the magnitude of the 3D effect in small cumulus clouds by using a fine-scale cloud model to simulate many hours of cloudiness over a continental site. We then use a Monte Carlo radiative transfer model to compute the broadband shortwave fluxes at the surface twice, once using the complete three-dimensional radiative transfer F(sup 3D), and once using the ICA F (sup ICA); the difference between them is the 3D effect given.

Spatial radiation environment in a heterogeneous oak woodland using a three-dimensional radiative transfer model and multiple constraints from observations

NASA Astrophysics Data System (ADS)

Kobayashi, H.; Ryu, Y.; Ustin, S.; Baldocchi, D. D.

2009-12-01

B15: Remote Characterization of Vegetation Structure: Including Research to Inform the Planned NASA DESDynI and ESA BIOMASS Missions Title: Spatial radiation environment in a heterogeneous oak woodland using a three-dimensional radiative transfer model and multiple constraints from observations Hideki Kobayashi, Youngryel Ryu, Susan Ustin, and Dennis Baldocchi Abstract Accurate evaluations of radiation environments of visible, near infrared, and thermal infrared wavebands in forest canopies are important to estimate energy, water, and carbon fluxes. Californian oak woodlands are sparse and highly clumped so that radiation environments are extremely heterogeneous spatially. The heterogeneity of radiation environments also varies with wavebands which depend on scattering and emission properties. So far, most of modeling studies have been performed in one dimensional radiative transfer models with (or without) clumping effect in the forest canopies. While some studies have been performed by using three dimensional radiative transfer models, several issues are still unresolved. For example, some 3D models calculate the radiation field with individual tree basis, and radiation interactions among trees are not considered. This interaction could be important in the highly scattering waveband such as near infrared. The objective of this study is to quantify the radiation field in the oak woodland. We developed a three dimensional radiative transfer model, which includes the thermal waveband. Soil/canopy energy balances and canopy physiology models, CANOAK, are incorporated in the radiative transfer model to simulate the diurnal patterns of thermal radiation fields and canopy physiology. Airborne LiDAR and canopy gap data measured by the several methods (digital photographs and plant canopy analyzer) were used to constrain the forest structures such as tree positions, crown sizes and leaf area density. Modeling results were tested by a traversing radiometer system that measured incoming photosynthetically active radiation and net radiation at forest floor and spatial variations in canopy reflectances taken by the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS). In this study, we show how the model with available measurements can reproduce the spatially heterogeneous radiation environments in the oak woodland.

A three-dimensional model of solar radiation transfer in a non-uniform plant canopy

NASA Astrophysics Data System (ADS)

Levashova, N. T.; Mukhartova, Yu V.

2018-01-01

A three-dimensional (3D) model of solar radiation transfer in a non-uniform plant canopy was developed. It is based on radiative transfer equations and a so-called turbid medium assumption. The model takes into account the multiple scattering contributions of plant elements in radiation fluxes. These enable more accurate descriptions of plant canopy reflectance and transmission in different spectral bands. The model was applied to assess the effects of plant canopy heterogeneity on solar radiation transmission and to quantify the difference in a radiation transfer between photosynthetically active radiation PAR (=0.39-0.72 μm) and near infrared solar radiation NIR (Δλ = 0.72-3.00 μm). Comparisons of the radiative transfer fluxes simulated by the 3D model within a plant canopy consisted of sparsely planted fruit trees (plant area index, PAI - 0.96 m2 m-2) with radiation fluxes simulated by a one-dimensional (1D) approach, assumed horizontal homogeneity of plant and leaf area distributions, showed that, for sunny weather conditions with a high solar elevation angle, an application of a simplified 1D approach can result in an underestimation of transmitted solar radiation by about 22% for PAR, and by about 26% for NIR.

FBILI method for multi-level line transfer

NASA Astrophysics Data System (ADS)

Kuzmanovska, O.; Atanacković, O.; Faurobert, M.

2017-07-01

Efficient non-LTE multilevel radiative transfer calculations are needed for a proper interpretation of astrophysical spectra. In particular, realistic simulations of time-dependent processes or multi-dimensional phenomena require that the iterative method used to solve such non-linear and non-local problem is as fast as possible. There are several multilevel codes based on efficient iterative schemes that provide a very high convergence rate, especially when combined with mathematical acceleration techniques. The Forth-and-Back Implicit Lambda Iteration (FBILI) developed by Atanacković-Vukmanović et al. [1] is a Gauss-Seidel-type iterative scheme that is characterized by a very high convergence rate without the need of complementing it with additional acceleration techniques. In this paper we make the implementation of the FBILI method to the multilevel atom line transfer in 1D more explicit. We also consider some of its variants and investigate their convergence properties by solving the benchmark problem of CaII line formation in the solar atmosphere. Finally, we compare our solutions with results obtained with the well known code MULTI.

Solution of Radiation and Convection Heat-Transfer Problems

NASA Technical Reports Server (NTRS)

Oneill, R. F.

1986-01-01

Computer program P5399B developed to accommodate variety of fin-type heat conduction applications involving radiative or convective boundary conditions with additionally imposed local heat flux. Program also accommodates significant variety of one-dimensional heat-transfer problems not corresponding specifically to fin-type applications. Program easily accommodates all but few specialized one-dimensional heat-transfer analyses as well as many twodimensional analyses.

Discontinuous finite element method for vector radiative transfer

NASA Astrophysics Data System (ADS)

Wang, Cun-Hai; Yi, Hong-Liang; Tan, He-Ping

2017-03-01

The discontinuous finite element method (DFEM) is applied to solve the vector radiative transfer in participating media. The derivation in a discrete form of the vector radiation governing equations is presented, in which the angular space is discretized by the discrete-ordinates approach with a local refined modification, and the spatial domain is discretized into finite non-overlapped discontinuous elements. The elements in the whole solution domain are connected by modelling the boundary numerical flux between adjacent elements, which makes the DFEM numerically stable for solving radiative transfer equations. Several various problems of vector radiative transfer are tested to verify the performance of the developed DFEM, including vector radiative transfer in a one-dimensional parallel slab containing a Mie/Rayleigh/strong forward scattering medium and a two-dimensional square medium. The fact that DFEM results agree very well with the benchmark solutions in published references shows that the developed DFEM in this paper is accurate and effective for solving vector radiative transfer problems.

FitSKIRT: genetic algorithms to automatically fit dusty galaxies with a Monte Carlo radiative transfer code

NASA Astrophysics Data System (ADS)

De Geyter, G.; Baes, M.; Fritz, J.; Camps, P.

2013-02-01

We present FitSKIRT, a method to efficiently fit radiative transfer models to UV/optical images of dusty galaxies. These images have the advantage that they have better spatial resolution compared to FIR/submm data. FitSKIRT uses the GAlib genetic algorithm library to optimize the output of the SKIRT Monte Carlo radiative transfer code. Genetic algorithms prove to be a valuable tool in handling the multi- dimensional search space as well as the noise induced by the random nature of the Monte Carlo radiative transfer code. FitSKIRT is tested on artificial images of a simulated edge-on spiral galaxy, where we gradually increase the number of fitted parameters. We find that we can recover all model parameters, even if all 11 model parameters are left unconstrained. Finally, we apply the FitSKIRT code to a V-band image of the edge-on spiral galaxy NGC 4013. This galaxy has been modeled previously by other authors using different combinations of radiative transfer codes and optimization methods. Given the different models and techniques and the complexity and degeneracies in the parameter space, we find reasonable agreement between the different models. We conclude that the FitSKIRT method allows comparison between different models and geometries in a quantitative manner and minimizes the need of human intervention and biasing. The high level of automation makes it an ideal tool to use on larger sets of observed data.

Multiscale solutions of radiative heat transfer by the discrete unified gas kinetic scheme

NASA Astrophysics Data System (ADS)

Luo, Xiao-Ping; Wang, Cun-Hai; Zhang, Yong; Yi, Hong-Liang; Tan, He-Ping

2018-06-01

The radiative transfer equation (RTE) has two asymptotic regimes characterized by the optical thickness, namely, optically thin and optically thick regimes. In the optically thin regime, a ballistic or kinetic transport is dominant. In the optically thick regime, energy transport is totally dominated by multiple collisions between photons; that is, the photons propagate by means of diffusion. To obtain convergent solutions to the RTE, conventional numerical schemes have a strong dependence on the number of spatial grids, which leads to a serious computational inefficiency in the regime where the diffusion is predominant. In this work, a discrete unified gas kinetic scheme (DUGKS) is developed to predict radiative heat transfer in participating media. Numerical performances of the DUGKS are compared in detail with conventional methods through three cases including one-dimensional transient radiative heat transfer, two-dimensional steady radiative heat transfer, and three-dimensional multiscale radiative heat transfer. Due to the asymptotic preserving property, the present method with relatively coarse grids gives accurate and reliable numerical solutions for large, small, and in-between values of optical thickness, and, especially in the optically thick regime, the DUGKS demonstrates a pronounced computational efficiency advantage over the conventional numerical models. In addition, the DUGKS has a promising potential in the study of multiscale radiative heat transfer inside the participating medium with a transition from optically thin to optically thick regimes.

Radiative Instabilities in Three-Dimensional Astrophysical Masers

NASA Technical Reports Server (NTRS)

Scappaticci, Gerardo A.; Watson, William D.

1995-01-01

Inherent instabilities in the radiative transfer for astrophysical masers have been recognized and calculated in the linear maser idealization in our previous investigations. The same instabilities are now shown to occur in the more realistic, three-dimensional geometries. Fluctuations in the emergent flux result and may be related to the observed fluctuations in the radiative flux from the 1665 MHz OH masers that have been reported to occur on timescales as short as 1000 s. The time-dependent differential equations of radiative transfer are solved numerically for three-dimensional astrophysical masers. Computations are performed for spherical and elongated (rectangular parallelepiped) geometries.

IPRT polarized radiative transfer model intercomparison project - Phase A

NASA Astrophysics Data System (ADS)

Emde, Claudia; Barlakas, Vasileios; Cornet, Céline; Evans, Frank; Korkin, Sergey; Ota, Yoshifumi; Labonnote, Laurent C.; Lyapustin, Alexei; Macke, Andreas; Mayer, Bernhard; Wendisch, Manfred

2015-10-01

The polarization state of electromagnetic radiation scattered by atmospheric particles such as aerosols, cloud droplets, or ice crystals contains much more information about the optical and microphysical properties than the total intensity alone. For this reason an increasing number of polarimetric observations are performed from space, from the ground and from aircraft. Polarized radiative transfer models are required to interpret and analyse these measurements and to develop retrieval algorithms exploiting polarimetric observations. In the last years a large number of new codes have been developed, mostly for specific applications. Benchmark results are available for specific cases, but not for more sophisticated scenarios including polarized surface reflection and multi-layer atmospheres. The International Polarized Radiative Transfer (IPRT) working group of the International Radiation Commission (IRC) has initiated a model intercomparison project in order to fill this gap. This paper presents the results of the first phase A of the IPRT project which includes ten test cases, from simple setups with only one layer and Rayleigh scattering to rather sophisticated setups with a cloud embedded in a standard atmosphere above an ocean surface. All scenarios in the first phase A of the intercomparison project are for a one-dimensional plane-parallel model geometry. The commonly established benchmark results are available at the IPRT website.

Multi-dimensional simulations of core-collapse supernova explosions with CHIMERA

NASA Astrophysics Data System (ADS)

Messer, O. E. B.; Harris, J. A.; Hix, W. R.; Lentz, E. J.; Bruenn, S. W.; Mezzacappa, A.

2018-04-01

Unraveling the core-collapse supernova (CCSN) mechanism is a problem that remains essentially unsolved despite more than four decades of effort. Spherically symmetric models with otherwise high physical fidelity generally fail to produce explosions, and it is widely accepted that CCSNe are inherently multi-dimensional. Progress in realistic modeling has occurred recently through the availability of petascale platforms and the increasing sophistication of supernova codes. We will discuss our most recent work on understanding neutrino-driven CCSN explosions employing multi-dimensional neutrino-radiation hydrodynamics simulations with the Chimera code. We discuss the inputs and resulting outputs from these simulations, the role of neutrino radiation transport, and the importance of multi-dimensional fluid flows in shaping the explosions. We also highlight the production of 48Ca in long-running Chimera simulations.

Atmospheric Radiative Transfer for Satellite Remote Sensing

NASA Technical Reports Server (NTRS)

Marshak, Alexander

2008-01-01

I will discuss the science of satellite remote sensing which involves the interpretation and inversion of radiometric measurements made from space. The goal of remote sensing is to retrieve some physical aspects of the medium which are sensitive to the radiation at specific wavelengths. This requires the use of fundamentals of atmospheric radiative transfer. I will talk about atmospheric radiation or, more specifically, about the interactions of solar radiation with aerosols and cloud particles. The focus will be more on cloudy atmospheres. I will also show how a standard one-dimensional approach, that is traced back at least 100 years, can fail to interpret the complexity of real clouds. I n these cases, three-dimensional radiative transfer should be used. Examples of satellite retrievals will illustrate the cases.

Extending generalized Kubelka-Munk to three-dimensional radiative transfer.

PubMed

Sandoval, Christopher; Kim, Arnold D

2015-08-10

The generalized Kubelka-Munk (gKM) approximation is a linear transformation of the double spherical harmonics of order one (DP₁) approximation of the radiative transfer equation. Here, we extend the gKM approximation to study problems in three-dimensional radiative transfer. In particular, we derive the gKM approximation for the problem of collimated beam propagation and scattering in a plane-parallel slab composed of a uniform absorbing and scattering medium. The result is an 8×8 system of partial differential equations that is much easier to solve than the radiative transfer equation. We compare the solutions of the gKM approximation with Monte Carlo simulations of the radiative transfer equation to identify the range of validity for this approximation. We find that the gKM approximation is accurate for isotropic scattering media that are sufficiently thick and much less accurate for anisotropic, forward-peaked scattering media.

Final Report: SciDAC Computational Astrophysics Consortium (at Princeton University)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burrows, Adam

Supernova explosions are the central events in astrophysics. They are the major agencies of change in the interstellar medium, driving star formation and the evolution of galaxies. Their gas remnants are the birthplaces of the cosmic rays. Such is their brightness that they can be used as standard candles to measure the size and geometry of the universe and their investigation draws on particle and nuclear physics, radiative transfer, kinetic theory, gravitational physics, thermodynamics, and the numerical arts. Hence, supernovae are unrivaled astrophysical laboratories. We will develop new state-of-the-art multi-dimensional radiation hydrodynamic codes to address this and other related astrophysicalmore » phenomena.« less

Atmospheric Radiative Transfer for Satellite Remote Sensing: Validation and Uncertainty

NASA Technical Reports Server (NTRS)

Marshak, Alexander

2007-01-01

My presentation will begin with the discussion of the Intercomparison of three-dimensional (3D) Radiative Codes (13RC) project that has been started in 1997. I will highlight the question of how well the atmospheric science community can solve the 3D radiative transfer equation. Initially I3RC was focused only on algorithm intercomparison; now it has acquired a broader identity providing new insights and creating new community resources for 3D radiative transfer calculations. Then I will switch to satellite remote sensing. Almost all radiative transfer calculations for satellite remote sensing are one-dimensional (1D) assuming (i) no variability inside a satellite pixel and (ii) no radiative interactions between pixels. The assumptions behind the 1D approach will be checked using cloud and aerosol data measured by the MODerate Resolution Imaging Spectroradiometer (MODIS) on board of two NASA satellites TERRA and AQUA. In the discussion, I will use both analysis technique: statistical analysis over large areas and time intervals, and single scene analysis to validate how well the 1D radiative transfer equation describes radiative regime in cloudy atmospheres.

Multi-dimensional simulations of core-collapse supernova explosions with CHIMERA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Messer, Bronson; Harris, James Austin; Hix, William Raphael

Unraveling the core-collapse supernova (CCSN) mechanism is a problem that remains essentially unsolved despite more than four decades of effort. Spherically symmetric models with otherwise high physical fidelity generally fail to produce explosions, and it is widely accepted that CCSNe are inherently multi-dimensional. Progress in realistic modeling has occurred recently through the availability of petascale platforms and the increasing sophistication of supernova codes. We will discuss our most recent work on understanding neutrino-driven CCSN explosions employing multi-dimensional neutrino-radiation hydrodynamics simulations with the Chimera code. We discuss the inputs and resulting outputs from these simulations, the role of neutrino radiation transport,more » and the importance of multi-dimensional fluid flows in shaping the explosions. We also highlight the production of 48Ca in long-running Chimera simulations.« less

Adjoint Methods for Adjusting Three-Dimensional Atmosphere and Surface Properties to Fit Multi-Angle Multi-Pixel Polarimetric Measurements

NASA Technical Reports Server (NTRS)

Martin, William G.; Cairns, Brian; Bal, Guillaume

2014-01-01

This paper derives an efficient procedure for using the three-dimensional (3D) vector radiative transfer equation (VRTE) to adjust atmosphere and surface properties and improve their fit with multi-angle/multi-pixel radiometric and polarimetric measurements of scattered sunlight. The proposed adjoint method uses the 3D VRTE to compute the measurement misfit function and the adjoint 3D VRTE to compute its gradient with respect to all unknown parameters. In the remote sensing problems of interest, the scalar-valued misfit function quantifies agreement with data as a function of atmosphere and surface properties, and its gradient guides the search through this parameter space. Remote sensing of the atmosphere and surface in a three-dimensional region may require thousands of unknown parameters and millions of data points. Many approaches would require calls to the 3D VRTE solver in proportion to the number of unknown parameters or measurements. To avoid this issue of scale, we focus on computing the gradient of the misfit function as an alternative to the Jacobian of the measurement operator. The resulting adjoint method provides a way to adjust 3D atmosphere and surface properties with only two calls to the 3D VRTE solver for each spectral channel, regardless of the number of retrieval parameters, measurement view angles or pixels. This gives a procedure for adjusting atmosphere and surface parameters that will scale to the large problems of 3D remote sensing. For certain types of multi-angle/multi-pixel polarimetric measurements, this encourages the development of a new class of three-dimensional retrieval algorithms with more flexible parametrizations of spatial heterogeneity, less reliance on data screening procedures, and improved coverage in terms of the resolved physical processes in the Earth?s atmosphere.

A Numerical Investigation of the Extinction of Low Strain Rate Diffusion Flames by an Agent in Microgravity

NASA Technical Reports Server (NTRS)

Puri, Ishwar K.

2004-01-01

Our goal has been to investigate the influence of both dilution and radiation on the extinction process of nonpremixed flames at low strain rates. Simulations have been performed by using a counterflow code and three radiation models have been included in it, namely, the optically thin, the narrowband, and discrete ordinate models. The counterflow flame code OPPDIFF was modified to account for heat transfer losses by radiation from the hot gases. The discrete ordinate method (DOM) approximation was first suggested by Chandrasekhar for solving problems in interstellar atmospheres. Carlson and Lathrop developed the method for solving multi-dimensional problem in neutron transport. Only recently has the method received attention in the field of heat transfer. Due to the applicability of the discrete ordinate method for thermal radiation problems involving flames, the narrowband code RADCAL was modified to calculate the radiative properties of the gases. A non-premixed counterflow flame was simulated with the discrete ordinate method for radiative emissions. In comparison with two other models, it was found that the heat losses were comparable with the optically thin and simple narrowband model. The optically thin model had the highest heat losses followed by the DOM model and the narrow-band model.

GPU-BASED MONTE CARLO DUST RADIATIVE TRANSFER SCHEME APPLIED TO ACTIVE GALACTIC NUCLEI

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heymann, Frank; Siebenmorgen, Ralf, E-mail: fheymann@pa.uky.edu

2012-05-20

A three-dimensional parallel Monte Carlo (MC) dust radiative transfer code is presented. To overcome the huge computing-time requirements of MC treatments, the computational power of vectorized hardware is used, utilizing either multi-core computer power or graphics processing units. The approach is a self-consistent way to solve the radiative transfer equation in arbitrary dust configurations. The code calculates the equilibrium temperatures of two populations of large grains and stochastic heated polycyclic aromatic hydrocarbons. Anisotropic scattering is treated applying the Heney-Greenstein phase function. The spectral energy distribution (SED) of the object is derived at low spatial resolution by a photon counting proceduremore » and at high spatial resolution by a vectorized ray tracer. The latter allows computation of high signal-to-noise images of the objects at any frequencies and arbitrary viewing angles. We test the robustness of our approach against other radiative transfer codes. The SED and dust temperatures of one- and two-dimensional benchmarks are reproduced at high precision. The parallelization capability of various MC algorithms is analyzed and included in our treatment. We utilize the Lucy algorithm for the optical thin case where the Poisson noise is high, the iteration-free Bjorkman and Wood method to reduce the calculation time, and the Fleck and Canfield diffusion approximation for extreme optical thick cells. The code is applied to model the appearance of active galactic nuclei (AGNs) at optical and infrared wavelengths. The AGN torus is clumpy and includes fluffy composite grains of various sizes made up of silicates and carbon. The dependence of the SED on the number of clumps in the torus and the viewing angle is studied. The appearance of the 10 {mu}m silicate features in absorption or emission is discussed. The SED of the radio-loud quasar 3C 249.1 is fit by the AGN model and a cirrus component to account for the far-infrared emission.« less

The Physics of Imaging with Remote Sensors : Photon State Space & Radiative Transfer

NASA Technical Reports Server (NTRS)

Davis, Anthony B.

2012-01-01

Standard (mono-pixel/steady-source) retrieval methodology is reaching its fundamental limit with access to multi-angle/multi-spectral photo- polarimetry. Next... Two emerging new classes of retrieval algorithm worth nurturing: multi-pixel time-domain Wave-radiometry transition regimes, and more... Cross-fertilization with bio-medical imaging. Physics-based remote sensing: - What is "photon state space?" - What is "radiative transfer?" - Is "the end" in sight? Two wide-open frontiers! center dot Examples (with variations.

Variable Density Multilayer Insulation for Cryogenic Storage

NASA Technical Reports Server (NTRS)

Hedayat, A.; Brown, T. M.; Hastings, L. J.; Martin, J.

2000-01-01

Two analytical models for a foam/Variable Density Multi-Layer Insulation (VD-MLI) system performance are discussed. Both models are one-dimensional and contain three heat transfer mechanisms, namely conduction through the spacer material, radiation between the shields, and conduction through the gas. One model is based on the methodology developed by McIntosh while the other model is based on the Lockheed semi-empirical approach. All models input variables are based on the Multi-purpose Hydrogen Test Bed (MHTB) geometry and available values for material properties and empirical solid conduction coefficient. Heat flux predictions are in good agreement with the MHTB data, The heat flux predictions are presented for the foam/MLI combinations with 30, 45, 60, and 75 MLI layers

Heat Transfer Modelling of Glass Media within TPV Systems

NASA Astrophysics Data System (ADS)

Bauer, Thomas; Forbes, Ian; Penlington, Roger; Pearsall, Nicola

2004-11-01

Understanding and optimisation of heat transfer, and in particular radiative heat transfer in terms of spectral, angular and spatial radiation distributions is important to achieve high system efficiencies and high electrical power densities for thermophtovoltaics (TPV). This work reviews heat transfer models and uses the Discrete Ordinates method. Firstly one-dimensional heat transfer in fused silica (quartz glass) shields was examined for the common arrangement, radiator-air-glass-air-PV cell. It has been concluded that an alternative arrangement radiator-glass-air-PV cell with increased thickness of fused silica should have advantages in terms of improved transmission of convertible radiation and enhanced suppression of non-convertible radiation.

Multi-dimensional Core-Collapse Supernova Simulations with Neutrino Transport

NASA Astrophysics Data System (ADS)

Pan, Kuo-Chuan; Liebendörfer, Matthias; Hempel, Matthias; Thielemann, Friedrich-Karl

We present multi-dimensional core-collapse supernova simulations using the Isotropic Diffusion Source Approximation (IDSA) for the neutrino transport and a modified potential for general relativity in two different supernova codes: FLASH and ELEPHANT. Due to the complexity of the core-collapse supernova explosion mechanism, simulations require not only high-performance computers and the exploitation of GPUs, but also sophisticated approximations to capture the essential microphysics. We demonstrate that the IDSA is an elegant and efficient neutrino radiation transfer scheme, which is portable to multiple hydrodynamics codes and fast enough to investigate long-term evolutions in two and three dimensions. Simulations with a 40 solar mass progenitor are presented in both FLASH (1D and 2D) and ELEPHANT (3D) as an extreme test condition. It is found that the black hole formation time is delayed in multiple dimensions and we argue that the strong standing accretion shock instability before black hole formation will lead to strong gravitational waves.

Research Advances on Radiation Transfer Modeling and Inversion for Multi-Scale Land Surface Remote Sensing

NASA Astrophysics Data System (ADS)

Liu, Q.

2011-09-01

At first, research advances on radiation transfer modeling on multi-scale remote sensing data are presented: after a general overview of remote sensing radiation transfer modeling, several recent research advances are presented, including leaf spectrum model (dPROS-PECT), vegetation canopy BRDF models, directional thermal infrared emission models(TRGM, SLEC), rugged mountains area radiation models, and kernel driven models etc. Then, new methodologies on land surface parameters inversion based on multi-source remote sensing data are proposed. The land surface Albedo, leaf area index, temperature/emissivity, and surface net radiation etc. are taken as examples. A new synthetic land surface parameter quantitative remote sensing product generation system is designed and the software system prototype will be demonstrated. At last, multi-scale field experiment campaigns, such as the field campaigns in Gansu and Beijing, China will be introduced briefly. The ground based, tower based, and airborne multi-angular measurement system have been built to measure the directional reflectance, emission and scattering characteristics from visible, near infrared, thermal infrared and microwave bands for model validation and calibration. The remote sensing pixel scale "true value" measurement strategy have been designed to gain the ground "true value" of LST, ALBEDO, LAI, soil moisture and ET etc. at 1-km2 for remote sensing product validation.

Quantum funneling in blended multi-band gap core/shell colloidal quantum dot solar cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Neo, Darren C. J.; Assender, Hazel E.; Watt, Andrew A. R., E-mail: Andrew.watt@materials.ox.ac.uk

2015-09-07

Multi-band gap heterojunction solar cells fabricated from a blend of 1.2 eV and 1.4 eV PbS colloidal quantum dots (CQDs) show poor device performance due to non-radiative recombination. To overcome this, a CdS shell is epitaxially formed around the PbS core using cation exchange. From steady state and transient photoluminescence measurements, we understand the nature of charge transfer between these quantum dots. Photoluminescence decay lifetimes are much longer in the PbS/CdS core/shell blend compared to PbS only, explained by a reduction in non-radiative recombination resulting from CdS surface passivation. PbS/CdS heterojunction devices sustain a higher open-circuit voltage and lower reverse saturation currentmore » as compared to PbS-only devices, implying lower recombination rates. Further device performance enhancement is attained by modifying the composition profile of the CQD species in the absorbing layer resulting in a three dimensional quantum cascade structure.« less

Backward and forward Monte Carlo method for vector radiative transfer in a two-dimensional graded index medium

NASA Astrophysics Data System (ADS)

Qian, Lin-Feng; Shi, Guo-Dong; Huang, Yong; Xing, Yu-Ming

2017-10-01

In vector radiative transfer, backward ray tracing is seldom used. We present a backward and forward Monte Carlo method to simulate vector radiative transfer in a two-dimensional graded index medium, which is new and different from the conventional Monte Carlo method. The backward and forward Monte Carlo method involves dividing the ray tracing into two processes backward tracing and forward tracing. In multidimensional graded index media, the trajectory of a ray is usually a three-dimensional curve. During the transport of a polarization ellipse, the curved ray trajectory will induce geometrical effects and cause Stokes parameters to continuously change. The solution processes for a non-scattering medium and an anisotropic scattering medium are analysed. We also analyse some parameters that influence the Stokes vector in two-dimensional graded index media. The research shows that the Q component of the Stokes vector cannot be ignored. However, the U and V components of the Stokes vector are very small.

Two-dimensional simulation of a two-phase, regenerative pumped radiator loop utilizing direct contact heat transfer with phase change

NASA Astrophysics Data System (ADS)

Rhee, Hyop S.; Begg, Lester L.; Wetch, Joseph R.; Jang, Jong H.; Juhasz, Albert J.

An innovative pumped loop concept for 600 K space power system radiators utilizing direct contact heat transfer, which facilitates repeated startup/shutdown of the power system without complex and time-consuming coolant thawing during power startup, is under development. The heat transfer process with melting/freezing of Li in an NaK flow was studied through two-dimensional time-dependent numerical simulations to characterize and predict the Li/NaK radiator performance during startup (thawing) and shutdown (cold-trapping). Effects of system parameters and the criteria for the plugging domain are presented together with temperature distribution patterns in solid Li and subsequent melting surface profile variations in time.

Radiative Heat Transfer in Finite Cylindrical Enclosures with Nonhomogeneous Participating Media

NASA Technical Reports Server (NTRS)

Hsu, Pei-Feng; Ku, Jerry C.

1994-01-01

Results of a numerical solution for radiative heat transfer in homogeneous and nonhomogeneous participating media are presented. The geometry of interest is a finite axisymmetric cylindrical enclosure. The integral formulation for radiative transport is solved by the YIX method. A three-dimensional solution scheme is applied to two-dimensional axisymmetric geometry to simplify kernel calculations and to avoid difficulties associated with treating boundary conditions. As part of the effort to improve modeling capabilities for turbulent jet diffusion flames, predicted distributions for flame temperature and soot volume fraction are used to calculate radiative heat transfer from soot particles in such flames. It is shown that the nonhomogeneity of radiative property has very significant effects. The peak value of the divergence of radiative heat flux could be underestimated by 2 factor of 7 if a mean homogeneous radiative property is used. Since recent studies have shown that scattering by soot agglomerates is significant in flames, the effect of magnitude of scattering is also investigated and found to be nonnegligible.

Two-dimensional HID light source radiative transfer using discrete ordinates method

NASA Astrophysics Data System (ADS)

Ghrib, Basma; Bouaoun, Mohamed; Elloumi, Hatem

2016-08-01

This paper shows the implementation of the Discrete Ordinates Method for handling radiation problems in High Intensity Discharge (HID) lamps. Therefore, we start with presenting this rigorous method for treatment of radiation transfer in a two-dimensional, axisymmetric HID lamp. Furthermore, the finite volume method is used for the spatial discretization of the Radiative Transfer Equation. The atom and electron densities were calculated using temperature profiles established by a 2D semi-implicit finite-element scheme for the solution of conservation equations relative to energy, momentum, and mass. Spectral intensities as a function of position and direction are first calculated, and then axial and radial radiative fluxes are evaluated as well as the net emission coefficient. The results are given for a HID mercury lamp on a line-by-line basis. A particular attention is paid on the 253.7 nm resonance and 546.1 nm green lines.

A numerical study of three-dimensional flame propagation over thin solids in purely forced concurrent flow including gas-phase radiation

NASA Astrophysics Data System (ADS)

Feier, Ioan I., Jr.

The effect of flame radiation on concurrent-flow flame spread over a thin solid sample of finite width in a low-speed wind tunnel is modeled using three-dimensional full Navier-Stokes equations and three-dimensional flame radiation transfer equations. The formulation includes the conservation of mass, momentum, energy, and species: fuel vapor, oxygen, carbon dioxide and water vapor. The SN discrete ordinates method is used to solve the radiation transfer equation with a mean absorption coefficient kappa = Ckappa p, where kappap is the Planck mean absorption coefficient of the gas mixture. The varying parameter C has a value between 0 and 1; C represents the strength of flame radiation. In addition, the solid fuel absorptivity alpha is varied to ascertain the effect of flame radiation heat feedback to the solid. The flow tunnel modeled has a dimension of 10x10x30 cm, the solid fuel has a width of 6-cm with two 1-cm inert strips as edges. Incoming forced flow velocity (5 cm/s) of 21% oxygen is assumed. For comparison with the three-dimensional results, corresponding two-dimensional computations are also performed. Detailed spatial flame profiles, solid surface profiles, and heat fluxes are presented. Increasing the flame radiation strength decreases the flame length. Although flame radiation provides an additional heat transfer mechanism to preheat the solid, it is insufficient to offset the decreased convective heating due to the shorter flame; the net effect is a slower spread rate. The percentage of unreacted fuel vapor that escapes from the flame is under 2%. It is theorized that some of the pyrolyzed fuel vapor diffuses sideway and reacts at the flame edges. A radiative energy balance is analyzed also. Flame radiative feedback to the solid plays a more important role in two-dimensional flames. With high solid fuel absorptivity, a peak in the flame spread rate occurs at an intermediate value of flame radiation strength---due to the competition between two mechanisms: gas-radiation heat loss weakening the flame and the radiative feedback boosting the solid pyrolysis. Two-dimensional calculations suggest that a larger percentage of unreacted fuel vapor can escape from the flame when the flame radiation strength is high.

Research Advances on Radiation Transfer Modeling and Inversion for Multi-scale Land Surface Remote Sensing

NASA Astrophysics Data System (ADS)

Liu, Q.; Li, J.; Du, Y.; Wen, J.; Zhong, B.; Wang, K.

2011-12-01

As the remote sensing data accumulating, it is a challenge and significant issue how to generate high accurate and consistent land surface parameter product from the multi source remote observation and the radiation transfer modeling and inversion methodology are the theoretical bases. In this paper, recent research advances and unresolved issues are presented. At first, after a general overview, recent research advances on multi-scale remote sensing radiation transfer modeling are presented, including leaf spectrum model, vegetation canopy BRDF models, directional thermal infrared emission models, rugged mountains area radiation models, and kernel driven models etc. Then, new methodologies on land surface parameters inversion based on multi-source remote sensing data are proposed, taking the land surface Albedo, leaf area index, temperature/emissivity, and surface net radiation as examples. A new synthetic land surface parameter quantitative remote sensing product generation system is suggested and the software system prototype will be demonstrated. At last, multi-scale field experiment campaigns, such as the field campaigns in Gansu and Beijing, China are introduced briefly. The ground based, tower based, and airborne multi-angular measurement system have been built to measure the directional reflectance, emission and scattering characteristics from visible, near infrared, thermal infrared and microwave bands for model validation and calibration. The remote sensing pixel scale "true value" measurement strategy have been designed to gain the ground "true value" of LST, ALBEDO, LAI, soil moisture and ET etc. at 1-km2 for remote sensing product validation.

Radiation transfer in plant canopies - Scattering of solar radiation and canopy reflectance

NASA Technical Reports Server (NTRS)

Verstraete, Michel M.

1988-01-01

The one-dimensional vertical model of radiation transfer in a plant canopy described by Verstraete (1987) is extended to account for the transfer of diffuse radiation. This improved model computes the absorption and scattering of both visible and near-infrared radiation in a multilayer canopy as a function of solar position and leaf orientation distribution. Multiple scattering is allowed, and the spectral reflectance of the vegetation stand is predicted. The results of the model are compared to those of other models and actual observations.

Multi-Dimensional Full Boltzmann-Neutrino-Radiation Hydrodynamic Simulations and Their Detailed Comparisons with Monte-Carlo Methods in Core Collapse Supernovae

NASA Astrophysics Data System (ADS)

Nagakura, H.; Richers, S.; Ott, C. D.; Iwakami, W.; Furusawa, S.; Sumiyoshi, K.; Yamada, S.; Matsufuru, H.; Imakura, A.

2016-10-01

We have developed a 7-dimensional Full Boltzmann-neutrino-radiation-hydrodynamical code and carried out ab-initio axisymmetric CCSNe simulations. I will talk about main results of our simulations and also discuss current ongoing projects.

Two-dimensional radiative transfer for the retrieval of limb emission measurements in the martian atmosphere

NASA Astrophysics Data System (ADS)

Kleinböhl, Armin; Friedson, A. James; Schofield, John T.

2017-01-01

The remote sounding of infrared emission from planetary atmospheres using limb-viewing geometry is a powerful technique for deriving vertical profiles of structure and composition on a global scale. Compared with nadir viewing, limb geometry provides enhanced vertical resolution and greater sensitivity to atmospheric constituents. However, standard limb profile retrieval techniques assume spherical symmetry and are vulnerable to biases produced by horizontal gradients in atmospheric parameters. We present a scheme for the correction of horizontal gradients in profile retrievals from limb observations of the martian atmosphere. It characterizes horizontal gradients in temperature, pressure, and aerosol extinction along the line-of-sight of a limb view through neighboring measurements, and represents these gradients by means of two-dimensional radiative transfer in the forward model of the retrieval. The scheme is applied to limb emission measurements from the Mars Climate Sounder instrument on Mars Reconnaissance Orbiter. Retrieval simulations using data from numerical models indicate that biases of up to 10 K in the winter polar region, obtained with standard retrievals using spherical symmetry, are reduced to about 2 K in most locations by the retrieval with two-dimensional radiative transfer. Retrievals from Mars atmospheric measurements suggest that the two-dimensional radiative transfer greatly reduces biases in temperature and aerosol opacity caused by observational geometry, predominantly in the polar winter regions.

GENERAL: Scattering Phase Correction for Semiclassical Quantization Rules in Multi-Dimensional Quantum Systems

NASA Astrophysics Data System (ADS)

Huang, Wen-Min; Mou, Chung-Yu; Chang, Cheng-Hung

2010-02-01

While the scattering phase for several one-dimensional potentials can be exactly derived, less is known in multi-dimensional quantum systems. This work provides a method to extend the one-dimensional phase knowledge to multi-dimensional quantization rules. The extension is illustrated in the example of Bogomolny's transfer operator method applied in two quantum wells bounded by step potentials of different heights. This generalized semiclassical method accurately determines the energy spectrum of the systems, which indicates the substantial role of the proposed phase correction. Theoretically, the result can be extended to other semiclassical methods, such as Gutzwiller trace formula, dynamical zeta functions, and semiclassical Landauer-Büttiker formula. In practice, this recipe enhances the applicability of semiclassical methods to multi-dimensional quantum systems bounded by general soft potentials.

SPECT3D - A multi-dimensional collisional-radiative code for generating diagnostic signatures based on hydrodynamics and PIC simulation output

NASA Astrophysics Data System (ADS)

MacFarlane, J. J.; Golovkin, I. E.; Wang, P.; Woodruff, P. R.; Pereyra, N. A.

2007-05-01

SPECT3D is a multi-dimensional collisional-radiative code used to post-process the output from radiation-hydrodynamics (RH) and particle-in-cell (PIC) codes to generate diagnostic signatures (e.g. images, spectra) that can be compared directly with experimental measurements. This ability to post-process simulation code output plays a pivotal role in assessing the reliability of RH and PIC simulation codes and their physics models. SPECT3D has the capability to operate on plasmas in 1D, 2D, and 3D geometries. It computes a variety of diagnostic signatures that can be compared with experimental measurements, including: time-resolved and time-integrated spectra, space-resolved spectra and streaked spectra; filtered and monochromatic images; and X-ray diode signals. Simulated images and spectra can include the effects of backlighters, as well as the effects of instrumental broadening and time-gating. SPECT3D also includes a drilldown capability that shows where frequency-dependent radiation is emitted and absorbed as it propagates through the plasma towards the detector, thereby providing insights on where the radiation seen by a detector originates within the plasma. SPECT3D has the capability to model a variety of complex atomic and radiative processes that affect the radiation seen by imaging and spectral detectors in high energy density physics (HEDP) experiments. LTE (local thermodynamic equilibrium) or non-LTE atomic level populations can be computed for plasmas. Photoabsorption rates can be computed using either escape probability models or, for selected 1D and 2D geometries, multi-angle radiative transfer models. The effects of non-thermal (i.e. non-Maxwellian) electron distributions can also be included. To study the influence of energetic particles on spectra and images recorded in intense short-pulse laser experiments, the effects of both relativistic electrons and energetic proton beams can be simulated. SPECT3D is a user-friendly software package that runs on Windows, Linux, and Mac platforms. A parallel version of SPECT3D is supported for Linux clusters for large-scale calculations. We will discuss the major features of SPECT3D, and present example results from simulations and comparisons with experimental data.

A Comparison of Numerical and Analytical Radiative-Transfer Solutions for Plane Albedo of Natural Waters

EPA Science Inventory

Three numerical algorithms were compared to provide a solution of a radiative transfer equation (RTE) for plane albedo (hemispherical reflectance) in semi-infinite one-dimensional plane-parallel layer. Algorithms were based on the invariant imbedding method and two different var...

Polarization radiation in the planetary atmosphere delimited by a heterogeneous diffusely reflecting surface

NASA Technical Reports Server (NTRS)

Strelkov, S. A.; Sushkevich, T. A.

1983-01-01

Spatial frequency characteristics (SFC) and the scattering functions were studied in the two cases of a uniform horizontal layer with absolutely black bottom, and an isolated layer. The mathematical model for these examples describes the horizontal heterogeneities in a light field with regard to radiation polarization in a three dimensional planar atmosphere, delimited by a heterogeneous surface with diffuse reflection. The perturbation method was used to obtain vector transfer equations which correspond to the linear and nonlinear systems of polarization radiation transfer. The boundary value tasks for the vector transfer equation that is a parametric set and one dimensional are satisfied by the SFC of the nonlinear system, and are expressed through the SFC of linear approximation. As a consequence of the developed theory, formulas were obtained for analytical calculation of albedo in solving the task of dissemination of polarization radiation in the planetary atmosphere with uniform Lambert bottom.

Two-dimensional molecular line transfer for a cometary coma

NASA Astrophysics Data System (ADS)

Szutowicz, S.

2017-09-01

In the proposed axisymmetric model of the cometary coma the gas density profile is described by an angular density function. Three methods for treating two-dimensional radiative transfer are compared: the Large Velocity Gradient (LVG) (the Sobolev method), Accelerated Lambda Iteration (ALI) and accelerated Monte Carlo (MC).

A Comparison of Numerical and Analytical Radiative-Transfer Solutions for Plane Albedo in Natural Waters

EPA Science Inventory

Several numerical and analytical solutions of the radiative transfer equation (RTE) for plane albedo were compared for solar light reflection by sea water. The study incorporated the simplest case, that being a semi-infinite one-dimensional plane-parallel absorbing and scattering...

Strain-induced modulation of near-field radiative transfer.

PubMed

Ghanekar, Alok; Ricci, Matthew; Tian, Yanpei; Gregory, Otto; Zheng, Yi

2018-06-11

In this theoretical study, we present a near-field thermal modulator that exhibits change in radiative heat transfer when subjected to mechanical stress/strain. The device has two terminals at different temperatures separated by vacuum: one fixed and one stretchable. The stretchable side contains one-dimensional grating. When subjected to mechanical strain, the effective optical properties of the stretchable side are affected upon deformation of the grating. This results in modulation of surface waves across the interfaces influencing near-field radiative heat transfer. We show that for a separation of 100 nm, it is possible to achieve 25% change in radiative heat transfer for a strain of 10%.

Coupling radiative heat transfer in participating media with other heat transfer modes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tencer, John; Howell, John R.

The common methods for finding the local radiative flux divergence in participating media through solution of the radiative transfer equation are outlined. The pros and cons of each method are discussed in terms of their speed, ability to handle spectral properties and scattering phenomena, as well as their accuracy in different ranges of media transport properties. The suitability of each method for inclusion in the energy equation to efficiently solve multi-mode thermal transfer problems is discussed. Lastly, remaining topics needing research are outlined.

Coupling radiative heat transfer in participating media with other heat transfer modes

DOE PAGES

Tencer, John; Howell, John R.

2015-09-28

The common methods for finding the local radiative flux divergence in participating media through solution of the radiative transfer equation are outlined. The pros and cons of each method are discussed in terms of their speed, ability to handle spectral properties and scattering phenomena, as well as their accuracy in different ranges of media transport properties. The suitability of each method for inclusion in the energy equation to efficiently solve multi-mode thermal transfer problems is discussed. Lastly, remaining topics needing research are outlined.

One-dimensional transient radiative transfer by lattice Boltzmann method.

PubMed

Zhang, Yong; Yi, Hongliang; Tan, Heping

2013-10-21

The lattice Boltzmann method (LBM) is extended to solve transient radiative transfer in one-dimensional slab containing scattering media subjected to a collimated short laser irradiation. By using a fully implicit backward differencing scheme to discretize the transient term in the radiative transfer equation, a new type of lattice structure is devised. The accuracy and computational efficiency of this algorithm are examined firstly. Afterwards, effects of the medium properties such as the extinction coefficient, the scattering albedo and the anisotropy factor, and the shapes of laser pulse on time-resolved signals of transmittance and reflectance are investigated. Results of the present method are found to compare very well with the data from the literature. For an oblique incidence, the LBM results in this paper are compared with those by Monte Carlo method generated by ourselves. In addition, transient radiative transfer in a two-Layer inhomogeneous media subjected to a short square pulse irradiation is investigated. At last, the LBM is further extended to study the transient radiative transfer in homogeneous medium with a refractive index discontinuity irradiated by the short pulse laser. Several trends on the time-resolved signals different from those for refractive index of 1 (i.e. refractive-index-matched boundary) are observed and analysed.

Numerical Model of Flame Spread Over Solids in Microgravity: A Supplementary Tool for Designing a Space Experiment

NASA Technical Reports Server (NTRS)

Shih, Hsin-Yi; Tien, James S.; Ferkul, Paul (Technical Monitor)

2001-01-01

The recently developed numerical model of concurrent-flow flame spread over thin solids has been used as a simulation tool to help the designs of a space experiment. The two-dimensional and three-dimensional, steady form of the compressible Navier-Stokes equations with chemical reactions are solved. With the coupled multi-dimensional solver of the radiative heat transfer, the model is capable of answering a number of questions regarding the experiment concept and the hardware designs. In this paper, the capabilities of the numerical model are demonstrated by providing the guidance for several experimental designing issues. The test matrix and operating conditions of the experiment are estimated through the modeling results. The three-dimensional calculations are made to simulate the flame-spreading experiment with realistic hardware configuration. The computed detailed flame structures provide the insight to the data collection. In addition, the heating load and the requirements of the product exhaust cleanup for the flow tunnel are estimated with the model. We anticipate that using this simulation tool will enable a more efficient and successful space experiment to be conducted.

Three-dimensional large-eddy simulations of the early phase of contrail-to-cirrus transition: effects of atmospheric turbulence and radiative transfer

DOE PAGES

Paoli, Roberto; Thouron, Odile; Cariolle, Daniel; ...

2017-12-08

Here, this article presents the results from numerical experiments of the early phase of contrail-cirrus formation using a limited set of fully three-dimensional, high-resolution large-eddy-simulations. The focus is laid on the interplay between atmospheric turbulence and the radiative transfer (and to a limited extent the ambient ice relative humidity), and how this interaction affects the contrail evolution and the characteristics of the resulting contrail-cirrus one hour after emission. Turbulence is sustained via a large-scale stochastic forcing that creates a non-uniform shear in addition to pure turbulent fluctuations. This effect manifests in the formation of vertically sheared structures of ice crystals.more » When radiative transfer is activated, ice tends to redistribute more uniformly along the vertical direction forming spotty vertical structures. For the conditions analyzed in this study, atmospheric turbulence, inclusive of non-uniform turbulent shear and turbulent fluctuations, affects primarily the contrail width whereas the microphysical properties such ice water path and ice mass are controlled by radiative transfer and relative humidity.« less

Three-dimensional large-eddy simulations of the early phase of contrail-to-cirrus transition: effects of atmospheric turbulence and radiative transfer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paoli, Roberto; Thouron, Odile; Cariolle, Daniel

Here, this article presents the results from numerical experiments of the early phase of contrail-cirrus formation using a limited set of fully three-dimensional, high-resolution large-eddy-simulations. The focus is laid on the interplay between atmospheric turbulence and the radiative transfer (and to a limited extent the ambient ice relative humidity), and how this interaction affects the contrail evolution and the characteristics of the resulting contrail-cirrus one hour after emission. Turbulence is sustained via a large-scale stochastic forcing that creates a non-uniform shear in addition to pure turbulent fluctuations. This effect manifests in the formation of vertically sheared structures of ice crystals.more » When radiative transfer is activated, ice tends to redistribute more uniformly along the vertical direction forming spotty vertical structures. For the conditions analyzed in this study, atmospheric turbulence, inclusive of non-uniform turbulent shear and turbulent fluctuations, affects primarily the contrail width whereas the microphysical properties such ice water path and ice mass are controlled by radiative transfer and relative humidity.« less

Linear Polarization, Circular Polarization, and Depolarization of Gamma-ray Bursts: A Simple Case of Jitter Radiation

NASA Astrophysics Data System (ADS)

Mao, Jirong; Wang, Jiancheng

2017-04-01

Linear and circular polarizations of gamma-ray bursts (GRBs) have been detected recently. We adopt a simplified model to investigate GRB polarization characteristics in this paper. A compressed two-dimensional turbulent slab containing stochastic magnetic fields is considered, and jitter radiation can produce the linear polarization under this special magnetic field topology. Turbulent Faraday rotation measure (RM) of this slab makes strong wavelength-dependent depolarization. The jitter photons can also scatter with those magnetic clumps inside the turbulent slab, and a nonzero variance of the Stokes parameter V can be generated. Furthermore, the linearly and circularly polarized photons in the optical and radio bands may suffer heavy absorptions from the slab. Thus we consider the polarized jitter radiation transfer processes. Finally, we compare our model results with the optical detections of GRB 091018, GRB 121024A, and GRB 131030A. We suggest simultaneous observations of GRB multi-wavelength polarization in the future.

Linear Polarization, Circular Polarization, and Depolarization of Gamma-ray Bursts: A Simple Case of Jitter Radiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mao, Jirong; Wang, Jiancheng, E-mail: jirongmao@mail.ynao.ac.cn

Linear and circular polarizations of gamma-ray bursts (GRBs) have been detected recently. We adopt a simplified model to investigate GRB polarization characteristics in this paper. A compressed two-dimensional turbulent slab containing stochastic magnetic fields is considered, and jitter radiation can produce the linear polarization under this special magnetic field topology. Turbulent Faraday rotation measure (RM) of this slab makes strong wavelength-dependent depolarization. The jitter photons can also scatter with those magnetic clumps inside the turbulent slab, and a nonzero variance of the Stokes parameter V can be generated. Furthermore, the linearly and circularly polarized photons in the optical and radiomore » bands may suffer heavy absorptions from the slab. Thus we consider the polarized jitter radiation transfer processes. Finally, we compare our model results with the optical detections of GRB 091018, GRB 121024A, and GRB 131030A. We suggest simultaneous observations of GRB multi-wavelength polarization in the future.« less

Modeling of bioheat equation for skin and a preliminary study on a noninvasive diagnostic method for skin burn wounds.

PubMed

Lee, Shong-Leih; Lu, Yung-Hsiang

2014-08-01

Heat transfer in a unit three-dimensional skin tissue with an embedded vascular system of actual histology structure is computed in the present work. The tissue temperature and the blood temperatures in artery and vein vessels are solved with a multi-grid system. The mean temperature of the tissue over the cross-section of the unit skin area is evaluated. The resulting one-dimensional function is regarded as the temperature of healthy tissue (or injured skin but the blood perfusion is still normally working) for large area of skin in view of the symmetric and periodic structure of the paired artery-vein vessels in nature. A three-dimensional bioheat equation then is formulated by the superposition of the skin burn wound effect and the healthy skin temperature with and without thermal radiation exposure. When this bioheat equation is employed to simulate ADT process on burn wounds, the decaying factor of the skin surface temperature is found to be a sharply decreasing function of time in the self-cooling stage after a thermal radiation heating. Nevertheless, the boundary of non-healing (needing surgery) and healing regions in a large burn wound can be estimated by tracking the peak of the gradient of decaying factor within 30 s after the thermal radiation is turned off. Experimental studies on the full ADT procedure are needed to justify the assumptions in the present computation. Copyright © 2013 Elsevier Ltd and ISBI. All rights reserved.

Using Synchrotron Radiation Microtomography to Investigate Multi-scale Three-dimensional Microelectronic Packages

DOE PAGES

Carlton, Holly D.; Elmer, John W.; Li, Yan; ...

2016-04-13

For this study synchrotron radiation micro-­tomography, a non-destructive three-dimensional imaging technique, is employed to investigate an entire microelectronic package with a cross-sectional area of 16 x 16 mm. Due to the synchrotron’s high flux and brightness the sample was imaged in just 3 minutes with an 8.7 μm spatial resolution.

Derivation and application of the reciprocity relations for radiative transfer with internal illumination

NASA Technical Reports Server (NTRS)

Cogley, A. C.

1975-01-01

A Green's function formulation is used to derive basic reciprocity relations for planar radiative transfer in a general medium with internal illumination. Reciprocity (or functional symmetry) allows an explicit and generalized development of the equivalence between source and probability functions. Assuming similar symmetry in three-dimensional space, a general relationship is derived between planar-source intensity and point-source total directional energy. These quantities are expressed in terms of standard (universal) functions associated with the planar medium, while all results are derived from the differential equation of radiative transfer.

Method for calculating internal radiation and ventilation with the ADINAT heat-flow code

DOE Office of Scientific and Technical Information (OSTI.GOV)

Butkovich, T.R.; Montan, D.N.

1980-04-01

One objective of the spent fuel test in Climax Stock granite (SFTC) is to correctly model the thermal transport, and the changes in the stress field and accompanying displacements from the application of the thermal loads. We have chosen the ADINA and ADINAT finite element codes to do these calculations. ADINAT is a heat transfer code compatible to the ADINA displacement and stress analysis code. The heat flow problem encountered at SFTC requires a code with conduction, radiation, and ventilation capabilities, which the present version of ADINAT does not have. We have devised a method for calculating internal radiation andmore » ventilation with the ADINAT code. This method effectively reproduces the results from the TRUMP multi-dimensional finite difference code, which correctly models radiative heat transport between drift surfaces, conductive and convective thermal transport to and through air in the drifts, and mass flow of air in the drifts. The temperature histories for each node in the finite element mesh calculated with ADINAT using this method can be used directly in the ADINA thermal-mechanical calculation.« less

Discontinuous Galerkin finite element methods for radiative transfer in spherical symmetry

NASA Astrophysics Data System (ADS)

Kitzmann, D.; Bolte, J.; Patzer, A. B. C.

2016-11-01

The discontinuous Galerkin finite element method (DG-FEM) is successfully applied to treat a broad variety of transport problems numerically. In this work, we use the full capacity of the DG-FEM to solve the radiative transfer equation in spherical symmetry. We present a discontinuous Galerkin method to directly solve the spherically symmetric radiative transfer equation as a two-dimensional problem. The transport equation in spherical atmospheres is more complicated than in the plane-parallel case owing to the appearance of an additional derivative with respect to the polar angle. The DG-FEM formalism allows for the exact integration of arbitrarily complex scattering phase functions, independent of the angular mesh resolution. We show that the discontinuous Galerkin method is able to describe accurately the radiative transfer in extended atmospheres and to capture discontinuities or complex scattering behaviour which might be present in the solution of certain radiative transfer tasks and can, therefore, cause severe numerical problems for other radiative transfer solution methods.

A tensor formulation of the equation of transfer for spherically symmetric flows. [radiative transfer in seven dimensional Riemannian space

NASA Technical Reports Server (NTRS)

Haisch, B. M.

1976-01-01

A tensor formulation of the equation of radiative transfer is derived in a seven-dimensional Riemannian space such that the resulting equation constitutes a divergence in any coordinate system. After being transformed to a spherically symmetric comoving coordinate system, the transfer equation contains partial derivatives in angle and frequency, as well as optical depth due to the effects of aberration and the Doppler shift. However, by virtue of the divergence form of this equation, the divergence theorem may be applied to yield a numerical differencing scheme which is expected to be stable and to conserve luminosity. It is shown that the equation of transfer derived by this method in a Lagrangian coordinate system may be reduced to that given by Castor (1972), although it is, of course, desirable to leave the equation in divergence form.

Solar Ellerman Bombs in 1D Radiative Hydrodynamics

NASA Astrophysics Data System (ADS)

Reid, A.; Mathioudakis, M.; Kowalski, A.; Doyle, J. G.; Allred, J. C.

2017-02-01

Recent observations from the Interface Region Imaging Spectrograph appear to show impulsive brightenings in high temperature lines, which when combined with simultaneous ground-based observations in Hα, appear co-spatial to Ellerman Bombs (EBs). We use the RADYN one-dimensional radiative transfer code in an attempt to try and reproduce the observed line profiles and simulate the atmospheric conditions of these events. Combined with the MULTI/RH line synthesis codes, we compute the Hα, Ca II 8542 Å, and Mg II h and k lines for these simulated events and compare them to previous observations. Our findings hint that the presence of superheated regions in the photosphere (>10,000 K) is not a plausible explanation for the production of EB signatures. While we are able to recreate EB-like line profiles in Hα, Ca II 8542 Å, and Mg II h and k, we cannot achieve agreement with all of these simultaneously.

Hybrid numerical method for solution of the radiative transfer equation in one, two, or three dimensions.

PubMed

Reinersman, Phillip N; Carder, Kendall L

2004-05-01

A hybrid method is presented by which Monte Carlo (MC) techniques are combined with an iterative relaxation algorithm to solve the radiative transfer equation in arbitrary one-, two-, or three-dimensional optical environments. The optical environments are first divided into contiguous subregions, or elements. MC techniques are employed to determine the optical response function of each type of element. The elements are combined, and relaxation techniques are used to determine simultaneously the radiance field on the boundary and throughout the interior of the modeled environment. One-dimensional results compare well with a standard radiative transfer model. The light field beneath and adjacent to a long barge is modeled in two dimensions and displayed. Ramifications for underwater video imaging are discussed. The hybrid model is currently capable of providing estimates of the underwater light field needed to expedite inspection of ship hulls and port facilities.

Multi-Band Light Curves from Two-Dimensional Simulations of Gamma-Ray Burst Afterglows

NASA Astrophysics Data System (ADS)

MacFadyen, Andrew

2010-01-01

The dynamics of gamma-ray burst outflows is inherently multi-dimensional. 1.) We present high resolution two-dimensional relativistic hydrodynamics simulations of GRBs in the afterglow phase using adaptive mesh refinement (AMR). Using standard synchrotron radiation models, we compute multi-band light curves, from the radio to X-ray, directly from the 2D hydrodynamics simulation data. We will present on-axis light curves for both constant density and wind media. We will also present off-axis light curves relevant for searches for orphan afterglows. We find that jet breaks are smoothed due to both off-axis viewing and wind media effects. 2.) Non-thermal radiation mechanisms in GRB afterglows require substantial magnetic field strengths. In turbulence driven by shear instabilities in relativistic magnetized gas, we demonstrate that magnetic field is naturally amplified to half a percent of the total energy (epsilon B = 0.005). We will show high resolution three dimensional relativistic MHD simulations of this process as well as particle in cell (PIC) simulations of mildly relativistic collisionless shocks.

Image matrix processor for fast multi-dimensional computations

DOEpatents

Roberson, George P.; Skeate, Michael F.

1996-01-01

An apparatus for multi-dimensional computation which comprises a computation engine, including a plurality of processing modules. The processing modules are configured in parallel and compute respective contributions to a computed multi-dimensional image of respective two dimensional data sets. A high-speed, parallel access storage system is provided which stores the multi-dimensional data sets, and a switching circuit routes the data among the processing modules in the computation engine and the storage system. A data acquisition port receives the two dimensional data sets representing projections through an image, for reconstruction algorithms such as encountered in computerized tomography. The processing modules include a programmable local host, by which they may be configured to execute a plurality of different types of multi-dimensional algorithms. The processing modules thus include an image manipulation processor, which includes a source cache, a target cache, a coefficient table, and control software for executing image transformation routines using data in the source cache and the coefficient table and loading resulting data in the target cache. The local host processor operates to load the source cache with a two dimensional data set, loads the coefficient table, and transfers resulting data out of the target cache to the storage system, or to another destination.

Thermal radiation heat transfer in participating media by finite volume discretization using collimated beam incidence

NASA Astrophysics Data System (ADS)

Harijishnu, R.; Jayakumar, J. S.

2017-09-01

The main objective of this paper is to study the heat transfer rate of thermal radiation in participating media. For that, a generated collimated beam has been passed through a two dimensional slab model of flint glass with a refractive index 2. Both Polar and azimuthal angle have been varied to generate such a beam. The Temperature of the slab and Snells law has been validated by Radiation Transfer Equation (RTE) in OpenFOAM (Open Field Operation and Manipulation), a CFD software which is the major computational tool used in Industry and research applications where the source code is modified in which radiation heat transfer equation is added to the case and different radiation heat transfer models are utilized. This work concentrates on the numerical strategies involving both transparent and participating media. Since Radiation Transfer Equation (RTE) is difficult to solve, the purpose of this paper is to use existing solver buoyantSimlpeFoam to solve radiation model in the participating media by compiling the source code to obtain the heat transfer rate inside the slab by varying the Intensity of radiation. The Finite Volume Method (FVM) is applied to solve the Radiation Transfer Equation (RTE) governing the above said physical phenomena.

Evaporating Atmospheres Around Close-in Exoplanets.

NASA Astrophysics Data System (ADS)

Owen, J.; Jackson, A.; Wu, Y.; Adams, F.

2014-12-01

The majority of currently observed exoplanets appear exceeding close to the central star (<0.1 AU) and as such are subject to intense high energy radiation from UV & X-ray photons. We will discuss that in such environments the atmospheres these planets are heated sufficiently that they can escape the planet's gravitational field in a hydrodynamic trans-sonic wind. We will show that this hydrodynamic mass-loss occurs for the majority of exoplanets at short periods, and for low-mass planets (<50 Mearth) is vigorous enough to significantly alter the planet's evolution. In some cases we will argue that an originally gas rich exoplanet can be completely evaporated leaving behind a bare rock core. In addition, we will present new multi-dimensional simulations of evaporation that include realistic treatment of the radiative transfer. These new simulations show that evaporation from 'hot' Jupiters is likely to be magnetically controlled, where mass-loss can only occur along open filed lines, where the interaction between the stellar and planetary magnetic field strongly controls the geometry of the evaporative flow. We will indicate how these new multi-dimensional radiation-magneto-hydrodynamic calculations can be used to study the time-dependence of the outflow and link the small but growing number of observations of exoplanet evaporation to the theoretical models. Finally, we will indicate that asymmetric evaporative flows can lead to orbital evolution of planets at close separations. Figure Caption: "Flow structure from an evaporating Hot Jupiter with a magnetic field strength of 0.3 Gauss. Top panels show density and magnetic field configuration and bottom panel shows plasma beta and velocity structure; left panels show simulation domain, right panels show a zoom in on the planet."

Effects of multiple scattering and surface albedo on the photochemistry of the troposphere

NASA Technical Reports Server (NTRS)

Augustsson, T. R.; Tiwari, S. N.

1981-01-01

The effect of treatment of incoming solar radiation on the photochemistry of the troposphere is discussed. A one dimensional photochemical model of the troposphere containing the species of the nitrogen, oxygen, carbon, hydrogen, and sulfur families was developed. The vertical flux is simulated by use of the parameterized eddy diffusion coefficients. The photochemical model is coupled to a radiative transfer model that calculates the radiation field due to the incoming solar radiation which initiates much of the photochemistry of the troposphere. Vertical profiles of tropospheric species were compared with the Leighton approximation, radiative transfer, matrix inversion model. The radiative transfer code includes the effects of multiple scattering due to molecules and aerosols, pure absorption, and surface albedo on the transfer of incoming solar radiation. It is indicated that significant differences exist for several key photolysis frequencies and species number density profiles between the Leighton approximation and the profiles generated with, radiative transfer, matrix inversion technique. Most species show enhanced vertical profiles when the more realistic treatment of the incoming solar radiation field is included

On the use of multi-dimensional scaling and electromagnetic tracking in high dose rate brachytherapy

NASA Astrophysics Data System (ADS)

Götz, Th I.; Ermer, M.; Salas-González, D.; Kellermeier, M.; Strnad, V.; Bert, Ch; Hensel, B.; Tomé, A. M.; Lang, E. W.

2017-10-01

High dose rate brachytherapy affords a frequent reassurance of the precise dwell positions of the radiation source. The current investigation proposes a multi-dimensional scaling transformation of both data sets to estimate dwell positions without any external reference. Furthermore, the related distributions of dwell positions are characterized by uni—or bi—modal heavy—tailed distributions. The latter are well represented by α—stable distributions. The newly proposed data analysis provides dwell position deviations with high accuracy, and, furthermore, offers a convenient visualization of the actual shapes of the catheters which guide the radiation source during the treatment.

Three-dimensional modeling of the Ca II H and K lines in the solar atmosphere

NASA Astrophysics Data System (ADS)

Bjørgen, Johan P.; Sukhorukov, Andrii V.; Leenaarts, Jorrit; Carlsson, Mats; de la Cruz Rodríguez, Jaime; Scharmer, Göran B.; Hansteen, Viggo H.

2018-03-01

Context. CHROMIS, a new imaging spectrometer at the Swedish 1-m Solar Telescope (SST), can observe the chromosphere in the H and K lines of Ca II at high spatial and spectral resolution. Accurate modeling as well as an understanding of the formation of these lines are needed to interpret the SST/CHROMIS observations. Such modeling is computationally challenging because these lines are influenced by strong departures from local thermodynamic equilibrium, three-dimensional radiative transfer, and partially coherent resonance scattering of photons. Aim. We aim to model the Ca II H and K lines in 3D model atmospheres to understand their formation and to investigate their diagnostic potential for probing the chromosphere. Methods: We model the synthetic spectrum of Ca II using the radiative transfer code Multi3D in three different radiation-magnetohydrodynamic model atmospheres computed with the Bifrost code. We classify synthetic intensity profiles according to their shapes and study how their features are related to the physical properties in the model atmospheres. We investigate whether the synthetic data reproduce the observed spatially-averaged line shapes, center-to-limb variation and compare this data with SST/CHROMIS images. Results: The spatially-averaged synthetic line profiles show too low central emission peaks, and too small separation between the peaks. The trends of the observed center-to-limb variation of the profiles properties are reproduced by the models. The Ca II H and K line profiles provide a temperature diagnostic of the temperature minimum and the temperature at the formation height of the emission peaks. The Doppler shift of the central depression is an excellent probe of the velocity in the upper chromosphere.

Incorporation of Three-dimensional Radiative Transfer into a Very High Resolution Simulation of Horizontally Inhomogeneous Clouds

NASA Astrophysics Data System (ADS)

Ishida, H.; Ota, Y.; Sekiguchi, M.; Sato, Y.

2016-12-01

A three-dimensional (3D) radiative transfer calculation scheme is developed to estimate horizontal transport of radiation energy in a very high resolution (with the order of 10 m in spatial grid) simulation of cloud evolution, especially for horizontally inhomogeneous clouds such as shallow cumulus and stratocumulus. Horizontal radiative transfer due to inhomogeneous clouds seems to cause local heating/cooling in an atmosphere with a fine spatial scale. It is, however, usually difficult to estimate the 3D effects, because the 3D radiative transfer often needs a large resource for computation compared to a plane-parallel approximation. This study attempts to incorporate a solution scheme that explicitly solves the 3D radiative transfer equation into a numerical simulation, because this scheme has an advantage in calculation for a sequence of time evolution (i.e., the scene at a time is little different from that at the previous time step). This scheme is also appropriate to calculation of radiation with strong absorption, such as the infrared regions. For efficient computation, this scheme utilizes several techniques, e.g., the multigrid method for iteration solution, and a correlated-k distribution method refined for efficient approximation of the wavelength integration. For a case study, the scheme is applied to an infrared broadband radiation calculation in a broken cloud field generated with a large eddy simulation model. The horizontal transport of infrared radiation, which cannot be estimated by the plane-parallel approximation, and its variation in time can be retrieved. The calculation result elucidates that the horizontal divergences and convergences of infrared radiation flux are not negligible, especially at the boundaries of clouds and within optically thin clouds, and the radiative cooling at lateral boundaries of clouds may reduce infrared radiative heating in clouds. In a future work, the 3D effects on radiative heating/cooling will be able to be included into atmospheric numerical models.

Prediction of the 21-cm signal from reionization: comparison between 3D and 1D radiative transfer schemes

NASA Astrophysics Data System (ADS)

Ghara, Raghunath; Mellema, Garrelt; Giri, Sambit K.; Choudhury, T. Roy; Datta, Kanan K.; Majumdar, Suman

2018-05-01

Three-dimensional radiative transfer simulations of the epoch of reionization can produce realistic results, but are computationally expensive. On the other hand, simulations relying on one-dimensional radiative transfer solutions are faster but limited in accuracy due to their more approximate nature. Here, we compare the performance of the reionization simulation codes GRIZZLY and C2-RAY which use 1D and 3D radiative transfer schemes, respectively. The comparison is performed using the same cosmological density fields, halo catalogues, and source properties. We find that the ionization maps, as well as the 21-cm signal maps from these two simulations are very similar even for complex scenarios which include thermal feedback on low-mass haloes. The comparison between the schemes in terms of the statistical quantities such as the power spectrum of the brightness temperature fluctuation agrees with each other within 10 per cent error throughout the entire reionization history. GRIZZLY seems to perform slightly better than the seminumerical approaches considered in Majumdar et al. which are based on the excursion set principle. We argue that GRIZZLY can be efficiently used for exploring parameter space, establishing observations strategies, and estimating parameters from 21-cm observations.

Forward Monte Carlo Computations of Polarized Microwave Radiation

NASA Technical Reports Server (NTRS)

Battaglia, A.; Kummerow, C.

2000-01-01

Microwave radiative transfer computations continue to acquire greater importance as the emphasis in remote sensing shifts towards the understanding of microphysical properties of clouds and with these to better understand the non linear relation between rainfall rates and satellite-observed radiance. A first step toward realistic radiative simulations has been the introduction of techniques capable of treating 3-dimensional geometry being generated by ever more sophisticated cloud resolving models. To date, a series of numerical codes have been developed to treat spherical and randomly oriented axisymmetric particles. Backward and backward-forward Monte Carlo methods are, indeed, efficient in this field. These methods, however, cannot deal properly with oriented particles, which seem to play an important role in polarization signatures over stratiform precipitation. Moreover, beyond the polarization channel, the next generation of fully polarimetric radiometers challenges us to better understand the behavior of the last two Stokes parameters as well. In order to solve the vector radiative transfer equation, one-dimensional numerical models have been developed, These codes, unfortunately, consider the atmosphere as horizontally homogeneous with horizontally infinite plane parallel layers. The next development step for microwave radiative transfer codes must be fully polarized 3-D methods. Recently a 3-D polarized radiative transfer model based on the discrete ordinate method was presented. A forward MC code was developed that treats oriented nonspherical hydrometeors, but only for plane-parallel situations.

Microphysics in the Multi-Scale Modeling Systems with Unified Physics

NASA Technical Reports Server (NTRS)

Tao, Wei-Kuo; Chern, J.; Lamg, S.; Matsui, T.; Shen, B.; Zeng, X.; Shi, R.

2011-01-01

In recent years, exponentially increasing computer power has extended Cloud Resolving Model (CRM) integrations from hours to months, the number of computational grid points from less than a thousand to close to ten million. Three-dimensional models are now more prevalent. Much attention is devoted to precipitating cloud systems where the crucial 1-km scales are resolved in horizontal domains as large as 10,000 km in two-dimensions, and 1,000 x 1,000 km2 in three-dimensions. Cloud resolving models now provide statistical information useful for developing more realistic physically based parameterizations for climate models and numerical weather prediction models. It is also expected that NWP and mesoscale model can be run in grid size similar to cloud resolving model through nesting technique. Recently, a multi-scale modeling system with unified physics was developed at NASA Goddard. It consists of (l) a cloud-resolving model (Goddard Cumulus Ensemble model, GCE model), (2) a regional scale model (a NASA unified weather research and forecast, WRF), (3) a coupled CRM and global model (Goddard Multi-scale Modeling Framework, MMF), and (4) a land modeling system. The same microphysical processes, long and short wave radiative transfer and land processes and the explicit cloud-radiation, and cloud-surface interactive processes are applied in this multi-scale modeling system. This modeling system has been coupled with a multi-satellite simulator to use NASA high-resolution satellite data to identify the strengths and weaknesses of cloud and precipitation processes simulated by the model. In this talk, the microphysics developments of the multi-scale modeling system will be presented. In particular, the results from using multi-scale modeling system to study the heavy precipitation processes will be presented.

Laser radiation in active amplifying media treated as a transport problem - Transfer equation derived and exactly solved

NASA Astrophysics Data System (ADS)

Gupta, S. R. D.; Gupta, Santanu D.

1991-10-01

The flow of laser radiation in a plane-parallel cylindrical slab of active amplifying medium with axial symmetry is treated as a problem in radiative transfer. The appropriate one-dimensional transfer equation describing the transfer of laser radiation has been derived by an appeal to Einstein's A, B coefficients (describing the processes of stimulated line absorption, spontaneous line emission, and stimulated line emission sustained by population inversion in the medium) and considering the 'rate equations' to completely establish the rational of the transfer equation obtained. The equation is then exactly solved and the angular distribution of the emergent laser beam intensity is obtained; its numerically computed values are given in tables and plotted in graphs showing the nature of peaks of the emerging laser beam intensity about the axis of the laser cylinder.

Radiative heat transfer in low-dimensional systems -- microscopic mode

NASA Astrophysics Data System (ADS)

Woods, Lilia; Phan, Anh; Drosdoff, David

2013-03-01

Radiative heat transfer between objects can increase dramatically at sub-wavelength scales. Exploring ways to modulate such transport between nano-systems is a key issue from fundamental and applied points of view. We advance the theoretical understanding of radiative heat transfer between nano-objects by introducing a microscopic model, which takes into account the individual atoms and their atomic polarizabilities. This approach is especially useful to investigate nano-objects with various geometries and give a detailed description of the heat transfer distribution. We employ this model to study the heat exchange in graphene nanoribbon/substrate systems. Our results for the distance separations, substrates, and presence of extended or localized defects enable making predictions for tailoring the radiative heat transfer at the nanoscale. Financial support from the Department of Energy under Contract No. DE-FG02-06ER46297 is acknowledged.

Scaling dimensions in spectroscopy of soil and vegetation

NASA Astrophysics Data System (ADS)

Malenovský, Zbyněk; Bartholomeus, Harm M.; Acerbi-Junior, Fausto W.; Schopfer, Jürg T.; Painter, Thomas H.; Epema, Gerrit F.; Bregt, Arnold K.

2007-05-01

The paper revises and clarifies definitions of the term scale and scaling conversions for imaging spectroscopy of soil and vegetation. We demonstrate a new four-dimensional scale concept that includes not only spatial but also the spectral, directional and temporal components. Three scaling remote sensing techniques are reviewed: (1) radiative transfer, (2) spectral (un)mixing, and (3) data fusion. Relevant case studies are given in the context of their up- and/or down-scaling abilities over the soil/vegetation surfaces and a multi-source approach is proposed for their integration. Radiative transfer (RT) models are described to show their capacity for spatial, spectral up-scaling, and directional down-scaling within a heterogeneous environment. Spectral information and spectral derivatives, like vegetation indices (e.g. TCARI/OSAVI), can be scaled and even tested by their means. Radiative transfer of an experimental Norway spruce ( Picea abies (L.) Karst.) research plot in the Czech Republic was simulated by the Discrete Anisotropic Radiative Transfer (DART) model to prove relevance of the correct object optical properties scaled up to image data at two different spatial resolutions. Interconnection of the successive modelling levels in vegetation is shown. A future development in measurement and simulation of the leaf directional spectral properties is discussed. We describe linear and/or non-linear spectral mixing techniques and unmixing methods that demonstrate spatial down-scaling. Relevance of proper selection or acquisition of the spectral endmembers using spectral libraries, field measurements, and pure pixels of the hyperspectral image is highlighted. An extensive list of advanced unmixing techniques, a particular example of unmixing a reflective optics system imaging spectrometer (ROSIS) image from Spain, and examples of other mixture applications give insight into the present status of scaling capabilities. Simultaneous spatial and temporal down-scaling by means of a data fusion technique is described. A demonstrative example is given for the moderate resolution imaging spectroradiometer (MODIS) and LANDSAT Thematic Mapper (TM) data from Brazil. Corresponding spectral bands of both sensors were fused via a pyramidal wavelet transform in Fourier space. New spectral and temporal information of the resultant image can be used for thematic classification or qualitative mapping. All three described scaling techniques can be integrated as the relevant methodological steps within a complex multi-source approach. We present this concept of combining numerous optical remote sensing data and methods to generate inputs for ecosystem process models.

Super-Planckian far-field radiative heat transfer

NASA Astrophysics Data System (ADS)

Fernández-Hurtado, V.; Fernández-Domínguez, A. I.; Feist, J.; García-Vidal, F. J.; Cuevas, J. C.

2018-01-01

We present here a theoretical analysis that demonstrates that the far-field radiative heat transfer between objects with dimensions smaller than the thermal wavelength can overcome the Planckian limit by orders of magnitude. To guide the search for super-Planckian far-field radiative heat transfer, we make use of the theory of fluctuational electrodynamics and derive a relation between the far-field radiative heat transfer and the directional absorption efficiency of the objects involved. Guided by this relation, and making use of state-of-the-art numerical simulations, we show that the far-field radiative heat transfer between highly anisotropic objects can largely overcome the black-body limit when some of their dimensions are smaller than the thermal wavelength. In particular, we illustrate this phenomenon in the case of suspended pads made of polar dielectrics like SiN or SiO2. These structures are widely used to measure the thermal transport through nanowires and low-dimensional systems and can be employed to test our predictions. Our work illustrates the dramatic failure of the classical theory to predict the far-field radiative heat transfer between micro- and nanodevices.

Groups in the radiative transfer theory

NASA Astrophysics Data System (ADS)

Nikoghossian, Arthur

2016-11-01

The paper presents a group-theoretical description of radiation transfer in inhomogeneous and multi-component atmospheres with the plane-parallel geometry. It summarizes and generalizes the results obtained recently by the author for some standard transfer problems of astrophysical interest with allowance of the angle and frequency distributions of the radiation field. We introduce the concept of composition groups for media with different optical and physical properties. Group representations are derived for two possible cases of illumination of a composite finite atmosphere. An algorithm for determining the reflectance and transmittance of inhomogeneous and multi-component atmospheres is described. The group theory is applied also to determining the field of radiation inside an inhomogeneous atmosphere. The concept of a group of optical depth translations is introduced. The developed theory is illustrated with the problem of radiation diffusion with partial frequency distribution assuming that the inhomogeneity is due to depth-variation of the scattering coefficient. It is shown that once reflectance and transmittance of a medium are determined, the internal field of radiation in the source-free atmosphere is found without solving any new equations. The transfer problems for a semi-infinite atmosphere and an atmosphere with internal sources of energy are discussed. The developed theory allows to derive summation laws for the mean number of scattering events underwent by the photons in the course of diffusion in the atmosphere.

Implications of a quadratic stream definition in radiative transfer theory.

NASA Technical Reports Server (NTRS)

Whitney, C.

1972-01-01

An explicit definition of the radiation-stream concept is stated and applied to approximate the integro-differential equation of radiative transfer with a set of twelve coupled differential equations. Computational efficiency is enhanced by distributing the corresponding streams in three-dimensional space in a totally symmetric way. Polarization is then incorporated in this model. A computer program based on the model is briefly compared with a Monte Carlo program for simulation of horizon scans of the earth's atmosphere. It is found to be considerably faster.

Image matrix processor for fast multi-dimensional computations

DOEpatents

Roberson, G.P.; Skeate, M.F.

1996-10-15

An apparatus for multi-dimensional computation is disclosed which comprises a computation engine, including a plurality of processing modules. The processing modules are configured in parallel and compute respective contributions to a computed multi-dimensional image of respective two dimensional data sets. A high-speed, parallel access storage system is provided which stores the multi-dimensional data sets, and a switching circuit routes the data among the processing modules in the computation engine and the storage system. A data acquisition port receives the two dimensional data sets representing projections through an image, for reconstruction algorithms such as encountered in computerized tomography. The processing modules include a programmable local host, by which they may be configured to execute a plurality of different types of multi-dimensional algorithms. The processing modules thus include an image manipulation processor, which includes a source cache, a target cache, a coefficient table, and control software for executing image transformation routines using data in the source cache and the coefficient table and loading resulting data in the target cache. The local host processor operates to load the source cache with a two dimensional data set, loads the coefficient table, and transfers resulting data out of the target cache to the storage system, or to another destination. 10 figs.

Three-dimensional modeling of diesel engine intake flow, combustion and emissions

NASA Technical Reports Server (NTRS)

Reitz, R. D.; Rutland, C. J.

1992-01-01

A three-dimensional computer code (KIVA) is being modified to include state-of-the-art submodels for diesel engine flow and combustion: spray atomization, drop breakup/coalescence, multi-component fuel vaporization, spray/wall interaction, ignition and combustion, wall heat transfer, unburned HC and NOx formation, soot and radiation, and the intake flow process. Improved and/or new submodels which were completed are: wall heat transfer with unsteadiness and compressibility, laminar-turbulent characteristic time combustion with unburned HC and Zeldo'vich NOx, and spray/wall impingement with rebounding and sliding drops. Results to date show that adding the effects of unsteadiness and compressibility improves the accuracy of heat transfer predictions; spray drop rebound can occur from walls at low impingement velocities (e.g., in cold-starting); larger spray drops are formed at the nozzle due to the influence of vaporization on the atomization process; a laminar-and-turbulent characteristic time combustion model has the flexibility to match measured engine combustion data over a wide range of operating conditions; and finally, the characteristic time combustion model can also be extended to allow predictions of ignition. The accuracy of the predictions is being assessed by comparisons with available measurements. Additional supporting experiments are also described briefly. To date, comparisons with measured engine cylinder pressure and heat flux data were made for homogeneous charge, spark-ignited and compression-ignited engines. The model results are in good agreement with the experiments.

Intercomparison of shortwave radiative transfer schemes in global aerosol modeling: results from the AeroCom Radiative Transfer Experiment

NASA Astrophysics Data System (ADS)

Randles, C. A.; Kinne, S.; Myhre, G.; Schulz, M.; Stier, P.; Fischer, J.; Doppler, L.; Highwood, E.; Ryder, C.; Harris, B.; Huttunen, J.; Ma, Y.; Pinker, R. T.; Mayer, B.; Neubauer, D.; Hitzenberger, R.; Oreopoulos, L.; Lee, D.; Pitari, G.; Di Genova, G.; Quaas, J.; Rose, Fred G.; Kato, S.; Rumbold, S. T.; Vardavas, I.; Hatzianastassiou, N.; Matsoukas, C.; Yu, H.; Zhang, F.; Zhang, H.; Lu, P.

2012-12-01

In this study we examine the performance of 31 global model radiative transfer schemes in cloud-free conditions with prescribed gaseous absorbers and no aerosols (Rayleigh atmosphere), with prescribed scattering-only aerosols, and with more absorbing aerosols. Results are compared to benchmark results from high-resolution, multi-angular line-by-line radiation models. For purely scattering aerosols, model bias relative to the line-by-line models in the top-of-the atmosphere aerosol radiative forcing ranges from roughly -10 to 20%, with over- and underestimates of radiative cooling at higher and lower sun elevation, respectively. Inter-model diversity (relative standard deviation) increases from ~10 to 15% as sun elevation increases. Inter-model diversity in atmospheric and surface forcing decreases with increased aerosol absorption, indicating that the treatment of multiple-scattering is more variable than aerosol absorption in the models considered. Aerosol radiative forcing results from multi-stream models are generally in better agreement with the line-by-line results than the simpler two-stream schemes. Considering radiative fluxes, model performance is generally the same or slightly better than results from previous radiation scheme intercomparisons. However, the inter-model diversity in aerosol radiative forcing remains large, primarily as a result of the treatment of multiple-scattering. Results indicate that global models that estimate aerosol radiative forcing with two-stream radiation schemes may be subject to persistent biases introduced by these schemes, particularly for regional aerosol forcing.

Intercomparison of shortwave radiative transfer schemes in global aerosol modeling: results from the AeroCom Radiative Transfer Experiment

NASA Astrophysics Data System (ADS)

Randles, C. A.; Kinne, S.; Myhre, G.; Schulz, M.; Stier, P.; Fischer, J.; Doppler, L.; Highwood, E.; Ryder, C.; Harris, B.; Huttunen, J.; Ma, Y.; Pinker, R. T.; Mayer, B.; Neubauer, D.; Hitzenberger, R.; Oreopoulos, L.; Lee, D.; Pitari, G.; Di Genova, G.; Quaas, J.; Rose, F. G.; Kato, S.; Rumbold, S. T.; Vardavas, I.; Hatzianastassiou, N.; Matsoukas, C.; Yu, H.; Zhang, F.; Zhang, H.; Lu, P.

2013-03-01

In this study we examine the performance of 31 global model radiative transfer schemes in cloud-free conditions with prescribed gaseous absorbers and no aerosols (Rayleigh atmosphere), with prescribed scattering-only aerosols, and with more absorbing aerosols. Results are compared to benchmark results from high-resolution, multi-angular line-by-line radiation models. For purely scattering aerosols, model bias relative to the line-by-line models in the top-of-the atmosphere aerosol radiative forcing ranges from roughly -10 to 20%, with over- and underestimates of radiative cooling at lower and higher solar zenith angle, respectively. Inter-model diversity (relative standard deviation) increases from ~10 to 15% as solar zenith angle decreases. Inter-model diversity in atmospheric and surface forcing decreases with increased aerosol absorption, indicating that the treatment of multiple-scattering is more variable than aerosol absorption in the models considered. Aerosol radiative forcing results from multi-stream models are generally in better agreement with the line-by-line results than the simpler two-stream schemes. Considering radiative fluxes, model performance is generally the same or slightly better than results from previous radiation scheme intercomparisons. However, the inter-model diversity in aerosol radiative forcing remains large, primarily as a result of the treatment of multiple-scattering. Results indicate that global models that estimate aerosol radiative forcing with two-stream radiation schemes may be subject to persistent biases introduced by these schemes, particularly for regional aerosol forcing.

Ionizing Shocks in Argon. Part 2: Transient and Multi-Dimensional Effects (Preprint)

DTIC Science & Technology

2010-09-09

stability in ionizing monatomic gases. Part 1. Argon ,” J. Fluid Mech., 84, 55 (1978). 2M. P. F. Bristow and I. I. Glass, “ Polarizability of singly...Article 3. DATES COVERED (From - To) 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER Ionizing Shocks in Argon . Part 2: Transient...Physics. 14. ABSTRACT We extend the computations of ionizing shocks in argon to unsteady and multi-dimensional, using a collisional-radiative

Laser Radiation in Active Amplifying Media Treated as a Transport Problem - Transfer Equation Derived and Exactly Solved

NASA Astrophysics Data System (ADS)

Das Gupta, Santanu; Das Gupta, S. R.

1991-10-01

The flow of laser radiation in a plane-parallel cylindrical slab of active amplifying medium with axial symmetry is treated as a problem in radiative transfer. The appropriate one-dimensional transfer equation describing the transfer of laser radiation has been derived by an appeal to Einstein'sA, B coefficients (describing the processes of stimulated line absorption, spontaneous line emission, and stimulated line emission sustained by population inversion in the medium) and considering the ‘rate equations’ to completely establish the rational of the transfer equation obtained. The equation is then exactly solved and the angular distribution of the emergent laser beam intensity is obtained; its numerically computed values are given in tables and plotted in graphs showing the nature of peaks of the emerging laser beam intensity about the axis of the laser cylinder.

Evaluation of the Anisotropic Radiative Conductivity of a Low-Density Carbon Fiber Material from Realistic Microscale Imaging

NASA Technical Reports Server (NTRS)

Nouri, Nima; Panerai, Francesco; Tagavi, Kaveh A.; Mansour, Nagi N.; Martin, Alexandre

2015-01-01

The radiative heat transfer inside a low-density carbon fiber insulator is analyzed using a three-dimensional direct simulation model. A robust procedure is presented for the numerical calculation of the geometric configuration factor to compute the radiative energy exchange processes among the small discretized surface areas of the fibrous material. The methodology is applied to a polygonal mesh of a fibrous insulator obtained from three-dimensional microscale imaging of the real material. The anisotropic values of the radiative conductivity are calculated for that geometry. The results yield both directional and thermal dependence of the radiative conductivity.

A multi-layer discrete-ordinate method for vector radiative transfer in a vertically-inhomogeneous, emitting and scattering atmosphere. I - Theory. II - Application

NASA Technical Reports Server (NTRS)

Weng, Fuzhong

1992-01-01

A theory is developed for discretizing the vector integro-differential radiative transfer equation including both solar and thermal radiation. A complete solution and boundary equations are obtained using the discrete-ordinate method. An efficient numerical procedure is presented for calculating the phase matrix and achieving computational stability. With natural light used as a beam source, the Stokes parameters from the model proposed here are compared with the analytical solutions of Chandrasekhar (1960) for a Rayleigh scattering atmosphere. The model is then applied to microwave frequencies with a thermal source, and the brightness temperatures are compared with those from Stamnes'(1988) radiative transfer model.

A Variational Formalism for the Radiative Transfer Equation and a Geostrophic, Hydrostatic Atmosphere: Prelude to Model 3

NASA Technical Reports Server (NTRS)

Achtemeier, Gary L.

1991-01-01

The second step in development of MODEL III is summarized. It combines the four radiative transfer equations of the first step with the equations for a geostrophic and hydrostatic atmosphere. This step is intended to bring radiance into a three dimensional balance with wind, height, and temperature. The use of the geostrophic approximation in place of the full set of primitive equations allows for an easier evaluation of how the inclusion of the radiative transfer equation increases the complexity of the variational equations. Seven different variational formulations were developed for geostrophic, hydrostatic, and radiative transfer equations. The first derivation was too complex to yield solutions that were physically meaningful. For the remaining six derivations, the variational method gave the same physical interpretation (the observed brightness temperatures could provide no meaningful input to a geostrophic, hydrostatic balance) at least through the problem solving methodology used in these studies. The variational method is presented and the Euler-Lagrange equations rederived for the geostrophic, hydrostatic, and radiative transfer equations.

Effects of multiple scattering and surface albedo on the photochemistry of the troposphere. Final report, period ending 30 Nov 1981

DOE Office of Scientific and Technical Information (OSTI.GOV)

Augustsson, T.R.; Tiwari, S.N.

The effect of treatment of incoming solar radiation on the photochemistry of the troposphere is discussed. A one dimensional photochemical model of the troposphere containing the species of the nitrogen, oxygen, carbon, hydrogen, and sulfur families was developed. The vertical flux is simulated by use of the parameterized eddy diffusion coefficients. The photochemical model is coupled to a radiative transfer model that calculates the radiation field due to the incoming solar radiation which initiates much of the photochemistry of the troposphere. Vertical profiles of tropospheric species were compared with the Leighton approximation, radiative transfer, matrix inversion model. The radiative transfermore » code includes the effects of multiple scattering due to molecules and aerosols, pure absorption, and surface albedo on the transfer of incoming solar radiation. It is indicated that significant differences exist for several key photolysis frequencies and species number density profiles between the Leighton approximation and the profiles generated with, radiative transfer, matrix inversion technique. Most species show enhanced vertical profiles when the more realistic treatment of the incoming solar radiation field is included« less

A multidimensional unified gas-kinetic scheme for radiative transfer equations on unstructured mesh

NASA Astrophysics Data System (ADS)

Sun, Wenjun; Jiang, Song; Xu, Kun

2017-12-01

In order to extend the unified gas kinetic scheme (UGKS) to solve radiative transfer equations in a complex geometry, a multidimensional asymptotic preserving implicit method on unstructured mesh is constructed in this paper. With an implicit formulation, the CFL condition for the determination of the time step in UGKS can be much relaxed, and a large time step is used in simulations. Differently from previous direction-by-direction UGKS on orthogonal structured mesh, on unstructured mesh the interface flux transport takes into account multi-dimensional effect, where gradients of radiation intensity and material temperature in both normal and tangential directions of a cell interface are included in the flux evaluation. The multiple scale nature makes the UGKS be able to capture the solutions in both optically thin and thick regions seamlessly. In the optically thick region the condition of cell size being less than photon's mean free path is fully removed, and the UGKS recovers a solver for diffusion equation in such a limit on unstructured mesh. For a distorted quadrilateral mesh, the UGKS goes to a nine-point scheme for the diffusion equation, and it naturally reduces to the standard five-point scheme for a orthogonal quadrilateral mesh. Numerical computations covering a wide range of transport regimes on unstructured and distorted quadrilateral meshes will be presented to validate the current approach.

Heat transfer in porous medium embedded with vertical plate: Non-equilibrium approach - Part A

DOE Office of Scientific and Technical Information (OSTI.GOV)

Badruddin, Irfan Anjum; Quadir, G. A.

2016-06-08

Heat transfer in a porous medium embedded with vertical flat plate is investigated by using thermal non-equilibrium model. Darcy model is employed to simulate the flow inside porous medium. It is assumed that the heat transfer takes place by natural convection and radiation. The vertical plate is maintained at isothermal temperature. The governing partial differential equations are converted into non-dimensional form and solved numerically using finite element method. Results are presented in terms of isotherms and streamlines for various parameters such as heat transfer coefficient parameter, thermal conductivity ratio, and radiation parameter.

Finite element computation of multi-physical micropolar transport phenomena from an inclined moving plate in porous media

NASA Astrophysics Data System (ADS)

Shamshuddin, MD.; Anwar Bég, O.; Sunder Ram, M.; Kadir, A.

2018-02-01

Non-Newtonian flows arise in numerous industrial transport processes including materials fabrication systems. Micropolar theory offers an excellent mechanism for exploring the fluid dynamics of new non-Newtonian materials which possess internal microstructure. Magnetic fields may also be used for controlling electrically-conducting polymeric flows. To explore numerical simulation of transport in rheological materials processing, in the current paper, a finite element computational solution is presented for magnetohydrodynamic, incompressible, dissipative, radiative and chemically-reacting micropolar fluid flow, heat and mass transfer adjacent to an inclined porous plate embedded in a saturated homogenous porous medium. Heat generation/absorption effects are included. Rosseland's diffusion approximation is used to describe the radiative heat flux in the energy equation. A Darcy model is employed to simulate drag effects in the porous medium. The governing transport equations are rendered into non-dimensional form under the assumption of low Reynolds number and also low magnetic Reynolds number. Using a Galerkin formulation with a weighted residual scheme, finite element solutions are presented to the boundary value problem. The influence of plate inclination, Eringen coupling number, radiation-conduction number, heat absorption/generation parameter, chemical reaction parameter, plate moving velocity parameter, magnetic parameter, thermal Grashof number, species (solutal) Grashof number, permeability parameter, Eckert number on linear velocity, micro-rotation, temperature and concentration profiles. Furthermore, the influence of selected thermo-physical parameters on friction factor, surface heat transfer and mass transfer rate is also tabulated. The finite element solutions are verified with solutions from several limiting cases in the literature. Interesting features in the flow are identified and interpreted.

Active and Passive 3D Vector Radiative Transfer with Preferentially-Aligned Ice Particles

NASA Astrophysics Data System (ADS)

Adams, I. S.; Munchak, S. J.; Pelissier, C.; Kuo, K. S.; Heymsfield, G. M.

2017-12-01

To support the observation of clouds and precipitation using combinations of radars and radiometers, a forward model capable of representing diverse sensing geometries for active and passive instruments is necessary for correctly interpreting and consistently combining multi-sensor measurements from ground-based, airborne, and spaceborne platforms. As such, the Atmospheric Radiative Transfer Simulator (ARTS) uses Monte Carlo integration to produce radar reflectivities and radiometric brightness temperatures for three-dimensional cloud and precipitation input fields. This radiative transfer framework is capable of efficiently sampling Gaussian antenna beams and fully accounting for multiple scattering. By relying on common ray-tracing tools, gaseous absorption models, and scattering properties, the model reproduces accurate and consistent radar and radiometer observables. While such a framework is an important component for simulating remote sensing observables, the key driver for self-consistent radiative transfer calculations of clouds and precipitation is scattering data. Research over the past decade has demonstrated that spheroidal models of frozen hydrometeors cannot accurately reproduce all necessary scattering properties at all desired frequencies. The discrete dipole approximation offers flexibility in calculating scattering for arbitrary particle geometries, but at great computational expense. When considering scattering for certain pristine ice particles, the Extended Boundary Condition Method, or T-Matrix, is much more computationally efficient; however, convergence for T-Matrix calculations fails at large size parameters and high aspect ratios. To address these deficiencies, we implemented the Invariant Imbedding T-Matrix Method (IITM). A brief overview of ARTS and IITM will be given, including details for handling preferentially-aligned hydrometeors. Examples highlighting the performance of the model for simulating space-based and airborne measurements will be offered, and some case studies showing the response to particle type and orientation will be presented. Simulations of polarized radar (Z, LDR, ZDR) and radiometer (Stokes I and Q) quantities will be used to demonstrate the capabilities of the model.

High performance computation of radiative transfer equation using the finite element method

NASA Astrophysics Data System (ADS)

Badri, M. A.; Jolivet, P.; Rousseau, B.; Favennec, Y.

2018-05-01

This article deals with an efficient strategy for numerically simulating radiative transfer phenomena using distributed computing. The finite element method alongside the discrete ordinate method is used for spatio-angular discretization of the monochromatic steady-state radiative transfer equation in an anisotropically scattering media. Two very different methods of parallelization, angular and spatial decomposition methods, are presented. To do so, the finite element method is used in a vectorial way. A detailed comparison of scalability, performance, and efficiency on thousands of processors is established for two- and three-dimensional heterogeneous test cases. Timings show that both algorithms scale well when using proper preconditioners. It is also observed that our angular decomposition scheme outperforms our domain decomposition method. Overall, we perform numerical simulations at scales that were previously unattainable by standard radiative transfer equation solvers.

Assessing the Suitability of Process and Information Technology in Supporting Tacit Knowledge Transfer

ERIC Educational Resources Information Center

Wu, Chien-Hsing; Kao, Shu-Chen; Shih, Lan-Hsin

2010-01-01

The transfer of tacit knowledge, one of the most important issues in the knowledge sharing context, needs a multi-dimensional perception in its process. Information technology's (IT) supporting role has already been addressed in the process of tacit knowledge transfer. However, IT has its own characteristics, and in turn, may have dissimilar…

Reflectivity of the atmosphere-inhomogeneous surfaces system Laboratory simulation

NASA Technical Reports Server (NTRS)

Mekler, Y.; Kaufman, Y. J.; Fraser, R. S.

1984-01-01

Theoretical two- and three-dimensional solutions of the radiative transfer equation have been applied to the earth-atmosphere system. Such solutions have not been verified experimentally. A laboratory experiment simulates such a system to test the theory. The atmosphere was simulated by latex spheres suspended in water and the ground by a nonuniform surface, half white and half black. A stable radiation source provided uniform illumination over the hydrosol. The upward radiance along a line orthogonal to the boundary of the two-halves field was recorded for different amounts of the hydrosol. The simulation is a well-defined radiative transfer experiment to test radiative transfer models involving nonuniform surfaces. Good agreement is obtained between the measured and theoretical results.

Development and Verification of Enclosure Radiation Capabilities in the CHarring Ablator Response (CHAR) Code

NASA Technical Reports Server (NTRS)

Salazar, Giovanni; Droba, Justin C.; Oliver, Brandon; Amar, Adam J.

2016-01-01

With the recent development of multi-dimensional thermal protection system (TPS) material response codes, the capability to account for surface-to-surface radiation exchange in complex geometries is critical. This paper presents recent efforts to implement such capabilities in the CHarring Ablator Response (CHAR) code developed at NASA's Johnson Space Center. This work also describes the different numerical methods implemented in the code to compute geometric view factors for radiation problems involving multiple surfaces. Verification of the code's radiation capabilities and results of a code-to-code comparison are presented. Finally, a demonstration case of a two-dimensional ablating cavity with enclosure radiation accounting for a changing geometry is shown.

Theoretical and Observational Determination of Global and Regional Radiation Budget, Forcing and Feedbacks at the Top-of-Atmosphere and Surface

NASA Technical Reports Server (NTRS)

Loeb, Norman G.

2004-01-01

Report consists of: 1. List of accomplishments 2. List of publications 3. Abstracts of published or submitted papers and 4. Subject invention disclosure. The accomplishments of the grant listed are: 1. Improved the third-order turbulence closure in cloud resolving models to remove the liquid water oscillation. 2. Used the University of California-Los Angeles (UCLA) large-eddy simulation (LES) model to provide data for radiation transfer testing. 3. Revised shortwave k-distribution models based on HITRAN 2000. 4. Developed a gamma-weighted two-stream radiative transfer model for radiation budget estimate applications. 5. Estimated the effect of spherical geometry to the earth radiation budget. 6. Estimated top-of-atmosphere irradiance over snow and sea ice surfaces. 7. Estimated the aerosol direct radiative effect at the top of the atmosphere. 8. Estimated the top-of-atmosphere reflectance of the clear-sky molecular atmosphere over ocean. 9. Developed and validated new set of Angular Distribution Models for the CERES TRMM satellite instrument (tropical) 10. Developed and validated new set of Angular Distribution Models for the CERES Terra satellite instrument (global) 11. Quantified the top-of-atmosphere direct radiative effect of aerosols over global oceans from merged CERES and MODIS observations 12 Clarified the definition of TOA flux reference level for radiation budget studies 13. Developed new algorithm for unfaltering CERES measured radiances 14. Used multiangle POLDER measurements to produce narrowband angular distribution models and examine the effect of scene identification errors on TOA albedo estimates 15. Developed and validated a novel algorithm called the Multidirectional Reflectance Matching (MRM) model for inferring TOA albedos from ice clouds using multi-angle satellite measurements. 16. Developed and validated a novel algorithm called the Multidirectional Polarized Reflectance Matching (MPRM) model for inferring particle shapes from ice clouds using multi-angle polarized satellite measurements. 17. Developed 4 advanced light scattering models including the three-dimensional (3D) uniaxial perfectly matched layer (UPML) finite-difference time-domain (FDTD) model. 18. Develop sunglint in situ measurement and study reflectance distribution in the sunglint area. 19. Lead a balloon-borne radiometer TOA albedo validation effort. 20. Developed a CERES surface UVB, UVA, and UV index product.

Effectiveness of a multi-channel volumetric air receiver for a solar power tower

NASA Astrophysics Data System (ADS)

Jung, Eui Guk; Boo, Joon Hong; Kang, Yong Heak; Kim, Nak Hoon

2013-08-01

In this study, the heat transfer performance of a multi-channel volumetric air receiver for a solar power tower was numerically analyzed. The governing equations, including the solar radiation heat flux, conduction, convection and radiation heat transfer for a single channel, were solved on the basis of valid related references and a methodology that can predict the temperature distribution of the receiver wall and the heat transfer fluid for specific dimensions and input conditions. Furthermore, a mathematical model of the effectiveness of the receiver was derived from an analysis of the temperature profiles of the wall and the heat transfer fluid. The receiver effectiveness as an appropriate criterion to assess economic feasibility regarding geometric size was investigated, as it would be applied to the design process of the receiver. The main parameters for the thermal performance simulations described in this paper are the air mass flow rate, receiver length and the influence of these parameters on the heat transfer performance from the viewpoint of receiver efficiency and effectiveness.

Modeling the Scattering Polarization of the Hydrogen Ly-alpha Line Observed by CLASP in a Filament Channel

NASA Technical Reports Server (NTRS)

Stepan, J.; Trujillo Bueno, J.; Gunar, S.; del Pino Aleman, T.; Heinzel, P.; Kano, R.; Ishikawa, R.; Narukage, M.; Bando, T.; Winebarger, Amy;

Minimum mass design of large-scale space trusses subjected to thermal gradients

NASA Technical Reports Server (NTRS)

Williams, R. Brett; Agnes, Gregory S.

2006-01-01

Lightweight, deployable trusses are commonly used to support space-borne instruments including RF reflectors, radar panels, and telescope optics. While in orbit, these support structures are subjected to thermal gradients that vary with altitude, location in orbit, and self-shadowing. Since these instruments have tight dimensional-stability requirements, their truss members are often covered with multi-layer insulation (MLI) blankets to minimize thermal distortions. This paper develops a radiation heat transfer model to predict the thermal gradient experienced by a triangular truss supporting a long, linear radar panel in Medium Earth Orbit (MEO). The influence of self-shadowing effects of the radar panel are included in the analysis, and the influence of both MLI thickness and outer covers/coatings on the magnitude of the thermal gradient are formed into a simple, two-dimensional analysis. This thermal model is then used to size and estimate the structural mass of a triangular truss that meets a given set of structural requirements.

Two-dimensional analytic weighting functions for limb scattering

NASA Astrophysics Data System (ADS)

Zawada, D. J.; Bourassa, A. E.; Degenstein, D. A.

2017-10-01

Through the inversion of limb scatter measurements it is possible to obtain vertical profiles of trace species in the atmosphere. Many of these inversion methods require what is often referred to as weighting functions, or derivatives of the radiance with respect to concentrations of trace species in the atmosphere. Several radiative transfer models have implemented analytic methods to calculate weighting functions, alleviating the computational burden of traditional numerical perturbation methods. Here we describe the implementation of analytic two-dimensional weighting functions, where derivatives are calculated relative to atmospheric constituents in a two-dimensional grid of altitude and angle along the line of sight direction, in the SASKTRAN-HR radiative transfer model. Two-dimensional weighting functions are required for two-dimensional inversions of limb scatter measurements. Examples are presented where the analytic two-dimensional weighting functions are calculated with an underlying one-dimensional atmosphere. It is shown that the analytic weighting functions are more accurate than ones calculated with a single scatter approximation, and are orders of magnitude faster than a typical perturbation method. Evidence is presented that weighting functions for stratospheric aerosols calculated under a single scatter approximation may not be suitable for use in retrieval algorithms under solar backscatter conditions.

The program FANS-3D (finite analytic numerical simulation 3-dimensional) and its applications

NASA Technical Reports Server (NTRS)

Bravo, Ramiro H.; Chen, Ching-Jen

1992-01-01

In this study, the program named FANS-3D (Finite Analytic Numerical Simulation-3 Dimensional) is presented. FANS-3D was designed to solve problems of incompressible fluid flow and combined modes of heat transfer. It solves problems with conduction and convection modes of heat transfer in laminar flow, with provisions for radiation and turbulent flows. It can solve singular or conjugate modes of heat transfer. It also solves problems in natural convection, using the Boussinesq approximation. FANS-3D was designed to solve heat transfer problems inside one, two and three dimensional geometries that can be represented by orthogonal planes in a Cartesian coordinate system. It can solve internal and external flows using appropriate boundary conditions such as symmetric, periodic and user specified.

Gray and multigroup radiation transport models for two-dimensional binary stochastic media using effective opacities

DOE PAGES

Olson, Gordon L.

2015-09-24

One-dimensional models for the transport of radiation through binary stochastic media do not work in multi-dimensions. In addition, authors have attempted to modify or extend the 1D models to work in multidimensions without success. Analytic one-dimensional models are successful in 1D only when assuming greatly simplified physics. State of the art theories for stochastic media radiation transport do not address multi-dimensions and temperature-dependent physics coefficients. Here, the concept of effective opacities and effective heat capacities is found to well represent the ensemble averaged transport solutions in cases with gray or multigroup temperature-dependent opacities and constant or temperature-dependent heat capacities. Inmore » every case analyzed here, effective physics coefficients fit the transport solutions over a useful range of parameter space. The transport equation is solved with the spherical harmonics method with angle orders of n=1 and 5. Although the details depend on what order of solution is used, the general results are similar, independent of angular order.« less

Gray and multigroup radiation transport models for two-dimensional binary stochastic media using effective opacities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Olson, Gordon L.

One-dimensional models for the transport of radiation through binary stochastic media do not work in multi-dimensions. In addition, authors have attempted to modify or extend the 1D models to work in multidimensions without success. Analytic one-dimensional models are successful in 1D only when assuming greatly simplified physics. State of the art theories for stochastic media radiation transport do not address multi-dimensions and temperature-dependent physics coefficients. Here, the concept of effective opacities and effective heat capacities is found to well represent the ensemble averaged transport solutions in cases with gray or multigroup temperature-dependent opacities and constant or temperature-dependent heat capacities. Inmore » every case analyzed here, effective physics coefficients fit the transport solutions over a useful range of parameter space. The transport equation is solved with the spherical harmonics method with angle orders of n=1 and 5. Although the details depend on what order of solution is used, the general results are similar, independent of angular order.« less

Transmission mode terahertz computed tomography

DOEpatents

Ferguson, Bradley Stuart; Wang, Shaohong; Zhang, Xi-Cheng

2006-10-10

A method of obtaining a series of images of a three-dimensional object by transmitting pulsed terahertz (THz) radiation through the entire object from a plurality of angles, optically detecting changes in the transmitted THz radiation using pulsed laser radiation, and constructing a plurality of imaged slices of the three-dimensional object using the detected changes in the transmitted THz radiation. The THz radiation is transmitted through the object as a scanning spot. The object is placed within the Rayleigh range of the focused THz beam and a focusing system is used to transfer the imaging plane from adjacent the object to a desired distance away from the object. A related system is also disclosed.

Galaxy Morphology From the UV to the FIR: An Intercomparison of Recent Observations From Space With New Radiative Transfer Models

NASA Technical Reports Server (NTRS)

(CIT), Barry Madore

1995-01-01

We will present the latest multiwavelength observations of spiral galaxies made from space and from the ground covering the electromagnetic spectrum from the far ultraviolet (ASTRO-2 UIT observations) through the optical, and out to the far infrared (IRAS). Comparisons with recent theoretical models for the radiative transfer of stellar light through a three-dimensional dusty galaxy will be presented.

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Hydrodynamic efficiency of laser-induced transfer of matter

NASA Astrophysics Data System (ADS)

Isakov, Vladimir A.; Kanavin, Andrey P.; Nasibov, A. S.

2007-04-01

A one-dimensional analytic hydrodynamic model of the direct laser-induced transfer of matter is considered. The efficiency of pulsed laser radiation energy conversion to the kinetic energy of the ejected matter is determined. It is shown that the hydrodynamic efficiency of the process for the layers of matter of thickness exceeding the laser radiation absorption depth is determined by the adiabatic index of the evaporated matter.

Multi-Wavelength Implications of the Companion Star in eta Carinae

NASA Technical Reports Server (NTRS)

Madura, Thomas I.; Gull, Theodore R.; Groh, Jose H.; Owocki, Stanley P.; Okazaki, Atsuo; Hillier, D. John; Russell, Christopher

2012-01-01

Eta-Carinae is considered to be a massive colliding wind binary system with a highly eccentric (e approximately 0.9), 5.54-yr orbit. However, the companion star continues to evade direct detection as the primary dwarfs its emission at most wavelengths. Using three-dimensional (3-D) SPH simulations of eta-Car's colliding winds and radiative transfer codes, we are able to compute synthetic observables across multiple wavebands for comparison to the observations. The models show that the presence of a companion star has a profound influence on the observed HST/STIS UV spectrum and H-alpha line profiles, as well as the ground-based photometric monitoring. Here, we focus on the Bore Hole effect, wherein the fast wind from the hot secondary star carves a cavity in the dense primary wind, allowing increased escape of radiation from the hotter/deeper layers of the primary's extended wind photosphere. The results have important implications for interpretations of eta-Car's observables at multiple wavelengths.

OSOAA: A Vector Radiative Transfer Model of Coupled Atmosphere-Ocean System for a Rough Sea Surface Application to the Estimates of the Directional Variations of the Water Leaving Reflectance to Better Process Multi-angular Satellite Sensors Data Over the Ocean

NASA Technical Reports Server (NTRS)

Chami, Malik; LaFrance, Bruno; Fougnie, Bertrand; Chowdhary, Jacek; Harmel, Tristan; Waquet, Fabien

2015-01-01

In this study, we present a radiative transfer model, so-called OSOAA, that is able to predict the radiance and degree of polarization within the coupled atmosphere-ocean system in the presence of a rough sea surface. The OSOAA model solves the radiative transfer equation using the successive orders of scattering method. Comparisons with another operational radiative transfer model showed a satisfactory agreement within 0.8%. The OSOAA model has been designed with a graphical user interface to make it user friendly for the community. The radiance and degree of polarization are provided at any level, from the top of atmosphere to the ocean bottom. An application of the OSOAA model is carried out to quantify the directional variations of the water leaving reflectance and degree of polarization for phytoplankton and mineral-like dominated waters. The difference between the water leaving reflectance at a given geometry and that obtained for the nadir direction could reach 40%, thus questioning the Lambertian assumption of the sea surface that is used by inverse satellite algorithms dedicated to multi-angular sensors. It is shown as well that the directional features of the water leaving reflectance are weakly dependent on wind speed. The quantification of the directional variations of the water leaving reflectance obtained in this study should help to correctly exploit the satellite data that will be acquired by the current or forthcoming multi-angular satellite sensors.

A Multi-scale Modeling System with Unified Physics to Study Precipitation Processes

NASA Astrophysics Data System (ADS)

Tao, W. K.

2017-12-01

In recent years, exponentially increasing computer power has extended Cloud Resolving Model (CRM) integrations from hours to months, the number of computational grid points from less than a thousand to close to ten million. Three-dimensional models are now more prevalent. Much attention is devoted to precipitating cloud systems where the crucial 1-km scales are resolved in horizontal domains as large as 10,000 km in two-dimensions, and 1,000 x 1,000 km2 in three-dimensions. Cloud resolving models now provide statistical information useful for developing more realistic physically based parameterizations for climate models and numerical weather prediction models. It is also expected that NWP and mesoscale model can be run in grid size similar to cloud resolving model through nesting technique. Recently, a multi-scale modeling system with unified physics was developed at NASA Goddard. It consists of (1) a cloud-resolving model (Goddard Cumulus Ensemble model, GCE model), (2) a regional scale model (a NASA unified weather research and forecast, WRF), and (3) a coupled CRM and global model (Goddard Multi-scale Modeling Framework, MMF). The same microphysical processes, long and short wave radiative transfer and land processes and the explicit cloud-radiation, and cloud-land surface interactive processes are applied in this multi-scale modeling system. This modeling system has been coupled with a multi-satellite simulator to use NASA high-resolution satellite data to identify the strengths and weaknesses of cloud and precipitation processes simulated by the model. In this talk, a review of developments and applications of the multi-scale modeling system will be presented. In particular, the results from using multi-scale modeling system to study the precipitation, processes and their sensitivity on model resolution and microphysics schemes will be presented. Also how to use of the multi-satellite simulator to improve precipitation processes will be discussed.

Using Multi-Scale Modeling Systems and Satellite Data to Study the Precipitation Processes

NASA Technical Reports Server (NTRS)

Tao, Wei-Kuo; Chern, J.; Lamg, S.; Matsui, T.; Shen, B.; Zeng, X.; Shi, R.

2011-01-01

In recent years, exponentially increasing computer power has extended Cloud Resolving Model (CRM) integrations from hours to months, the number of computational grid points from less than a thousand to close to ten million. Three-dimensional models are now more prevalent. Much attention is devoted to precipitating cloud systems where the crucial 1-km scales are resolved in horizontal domains as large as 10,000 km in two-dimensions, and 1,000 x 1,000 km2 in three-dimensions. Cloud resolving models now provide statistical information useful for developing more realistic physically based parameterizations for climate models and numerical weather prediction models. It is also expected that NWP and mesoscale model can be run in grid size similar to cloud resolving model through nesting technique. Recently, a multi-scale modeling system with unified physics was developed at NASA Goddard. It consists of (l) a cloud-resolving model (Goddard Cumulus Ensemble model, GCE model), (2) a regional scale model (a NASA unified weather research and forecast, WRF), (3) a coupled CRM and global model (Goddard Multi-scale Modeling Framework, MMF), and (4) a land modeling system. The same microphysical processes, long and short wave radiative transfer and land processes and the explicit cloud-radiation, and cloud-land surface interactive processes are applied in this multi-scale modeling system. This modeling system has been coupled with a multi-satellite simulator to use NASA high-resolution satellite data to identify the strengths and weaknesses of cloud and precipitation processes simulated by the model. In this talk, the recent developments and applications of the multi-scale modeling system will be presented. In particular, the results from using multi-scale modeling system to study the precipitating systems and hurricanes/typhoons will be presented. The high-resolution spatial and temporal visualization will be utilized to show the evolution of precipitation processes. Also how to use of the multi-satellite simulator tqimproy precipitation processes will be discussed.

Using Multi-Scale Modeling Systems and Satellite Data to Study the Precipitation Processes

NASA Technical Reports Server (NTRS)

Tao, Wei--Kuo; Chern, J.; Lamg, S.; Matsui, T.; Shen, B.; Zeng, X.; Shi, R.

2010-01-01

In recent years, exponentially increasing computer power extended Cloud Resolving Model (CRM) integrations from hours to months, the number of computational grid points from less than a thousand to close to ten million. Three-dimensional models are now more prevalent. Much attention is devoted to precipitating cloud systems where the crucial 1-km scales are resolved in horizontal domains as large as 10,000 km in two-dimensions, and 1,000 x 1,000 sq km in three-dimensions. Cloud resolving models now provide statistical information useful for developing more realistic physically based parameterizations for climate models and numerical weather prediction models. It is also expected that NWP and mesoscale models can be run in grid size similar to cloud resolving models through nesting technique. Recently, a multi-scale modeling system with unified physics was developed at NASA Goddard. It consists of (1) a cloud-resolving model (Goddard Cumulus Ensemble model, GCE model). (2) a regional scale model (a NASA unified weather research and forecast, W8F). (3) a coupled CRM and global model (Goddard Multi-scale Modeling Framework, MMF), and (4) a land modeling system. The same microphysical processes, long and short wave radiative transfer and land processes and the explicit cloud-radiation and cloud-land surface interactive processes are applied in this multi-scale modeling system. This modeling system has been coupled with a multi-satellite simulator to use NASA high-resolution satellite data to identify the strengths and weaknesses of cloud and precipitation processes simulated by the model. In this talk, a review of developments and applications of the multi-scale modeling system will be presented. In particular, the results from using multi-scale modeling systems to study the interactions between clouds, precipitation, and aerosols will be presented. Also how to use the multi-satellite simulator to improve precipitation processes will be discussed.

Using Multi-Scale Modeling Systems to Study the Precipitation Processes

NASA Technical Reports Server (NTRS)

Tao, Wei-Kuo

2010-01-01

In recent years, exponentially increasing computer power has extended Cloud Resolving Model (CRM) integrations from hours to months, the number of computational grid points from less than a thousand to close to ten million. Three-dimensional models are now more prevalent. Much attention is devoted to precipitating cloud systems where the crucial 1-km scales are resolved in horizontal domains as large as 10,000 km in two-dimensions, and 1,000 x 1,000 km2 in three-dimensions. Cloud resolving models now provide statistical information useful for developing more realistic physically based parameterizations for climate models and numerical weather prediction models. It is also expected that NWP and mesoscale model can be run in grid size similar to cloud resolving model through nesting technique. Recently, a multi-scale modeling system with unified physics was developed at NASA Goddard. It consists of (1) a cloud-resolving model (Goddard Cumulus Ensemble model, GCE model), (2) a regional scale model (a NASA unified weather research and forecast, WRF), (3) a coupled CRM and global model (Goddard Multi-scale Modeling Framework, MMF), and (4) a land modeling system. The same microphysical processes, long and short wave radiative transfer and land processes and the explicit cloud-radiation, and cloud-land surface interactive processes are applied in this multi-scale modeling system. This modeling system has been coupled with a multi-satellite simulator to use NASA high-resolution satellite data to identify the strengths and weaknesses of cloud and precipitation processes simulated by the model. In this talk, a review of developments and applications of the multi-scale modeling system will be presented. In particular, the results from using multi-scale modeling system to study the interactions between clouds, precipitation, and aerosols will be presented. Also how to use of the multi-satellite simulator to improve precipitation processes will be discussed.

The vector radiative transfer numerical model of coupled ocean-atmosphere system using the matrix-operator method

NASA Astrophysics Data System (ADS)

Xianqiang, He; Delu, Pan; Yan, Bai; Qiankun, Zhu

2005-10-01

The numerical model of the vector radiative transfer of the coupled ocean-atmosphere system is developed based on the matrix-operator method, which is named PCOART. In PCOART, using the Fourier analysis, the vector radiative transfer equation (VRTE) splits up into a set of independent equations with zenith angle as only angular coordinate. Using the Gaussian-Quadrature method, VRTE is finally transferred into the matrix equation, which is calculated by using the adding-doubling method. According to the reflective and refractive properties of the ocean-atmosphere interface, the vector radiative transfer numerical model of ocean and atmosphere is coupled in PCOART. By comparing with the exact Rayleigh scattering look-up-table of MODIS(Moderate-resolution Imaging Spectroradiometer), it is shown that PCOART is an exact numerical calculation model, and the processing methods of the multi-scattering and polarization are correct in PCOART. Also, by validating with the standard problems of the radiative transfer in water, it is shown that PCOART could be used to calculate the underwater radiative transfer problems. Therefore, PCOART is a useful tool to exactly calculate the vector radiative transfer of the coupled ocean-atmosphere system, which can be used to study the polarization properties of the radiance in the whole ocean-atmosphere system and the remote sensing of the atmosphere and ocean.

ASTRORAY: General relativistic polarized radiative transfer code

NASA Astrophysics Data System (ADS)

Shcherbakov, Roman V.

2014-07-01

ASTRORAY employs a method of ray tracing and performs polarized radiative transfer of (cyclo-)synchrotron radiation. The radiative transfer is conducted in curved space-time near rotating black holes described by Kerr-Schild metric. Three-dimensional general relativistic magneto hydrodynamic (3D GRMHD) simulations, in particular performed with variations of the HARM code, serve as an input to ASTRORAY. The code has been applied to reproduce the sub-mm synchrotron bump in the spectrum of Sgr A*, and to test the detectability of quasi-periodic oscillations in its light curve. ASTRORAY can be readily applied to model radio/sub-mm polarized spectra of jets and cores of other low-luminosity active galactic nuclei. For example, ASTRORAY is uniquely suitable to self-consistently model Faraday rotation measure and circular polarization fraction in jets.

Transcending the slow bimolecular recombination in lead-halide perovskites for electroluminescence

PubMed Central

Xing, Guichuan; Wu, Bo; Wu, Xiangyang; Li, Mingjie; Du, Bin; Wei, Qi; Guo, Jia; Yeow, Edwin K. L.; Sum, Tze Chien; Huang, Wei

2017-01-01

The slow bimolecular recombination that drives three-dimensional lead-halide perovskites' outstanding photovoltaic performance is conversely a fundamental limitation for electroluminescence. Under electroluminescence working conditions with typical charge densities lower than 1015 cm−3, defect-states trapping in three-dimensional perovskites competes effectively with the bimolecular radiative recombination. Herein, we overcome this limitation using van-der-Waals-coupled Ruddlesden-Popper perovskite multi-quantum-wells. Injected charge carriers are rapidly localized from adjacent thin few layer (n≤4) multi-quantum-wells to the thick (n≥5) multi-quantum-wells with extremely high efficiency (over 85%) through quantum coupling. Light emission originates from excitonic recombination in the thick multi-quantum-wells at much higher decay rate and efficiency than bimolecular recombination in three-dimensional perovskites. These multi-quantum-wells retain the simple solution processability and high charge carrier mobility of two-dimensional lead-halide perovskites. Importantly, these Ruddlesden-Popper perovskites offer new functionalities unavailable in single phase constituents, permitting the transcendence of the slow bimolecular recombination bottleneck in lead-halide perovskites for efficient electroluminescence. PMID:28239146

Transcending the slow bimolecular recombination in lead-halide perovskites for electroluminescence.

PubMed

Xing, Guichuan; Wu, Bo; Wu, Xiangyang; Li, Mingjie; Du, Bin; Wei, Qi; Guo, Jia; Yeow, Edwin K L; Sum, Tze Chien; Huang, Wei

2017-02-27

The slow bimolecular recombination that drives three-dimensional lead-halide perovskites' outstanding photovoltaic performance is conversely a fundamental limitation for electroluminescence. Under electroluminescence working conditions with typical charge densities lower than 10 15  cm -3 , defect-states trapping in three-dimensional perovskites competes effectively with the bimolecular radiative recombination. Herein, we overcome this limitation using van-der-Waals-coupled Ruddlesden-Popper perovskite multi-quantum-wells. Injected charge carriers are rapidly localized from adjacent thin few layer (n≤4) multi-quantum-wells to the thick (n≥5) multi-quantum-wells with extremely high efficiency (over 85%) through quantum coupling. Light emission originates from excitonic recombination in the thick multi-quantum-wells at much higher decay rate and efficiency than bimolecular recombination in three-dimensional perovskites. These multi-quantum-wells retain the simple solution processability and high charge carrier mobility of two-dimensional lead-halide perovskites. Importantly, these Ruddlesden-Popper perovskites offer new functionalities unavailable in single phase constituents, permitting the transcendence of the slow bimolecular recombination bottleneck in lead-halide perovskites for efficient electroluminescence.

A journey from nuclear criticality methods to high energy density radflow experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Urbatsch, Todd James

Los Alamos National Laboratory is a nuclear weapons laboratory supporting our nation's defense. In support of this mission is a high energy-density physics program in which we design and execute experiments to study radiationhydrodynamics phenomena and improve the predictive capability of our largescale multi-physics software codes on our big-iron computers. The Radflow project’s main experimental effort now is to understand why we haven't been able to predict opacities on Sandia National Laboratory's Z-machine. We are modeling an increasing fraction of the Z-machine's dynamic hohlraum to find multi-physics explanations for the experimental results. Further, we are building an entirely different opacitymore » platform on Lawrence Livermore National Laboratory's National Ignition Facility (NIF), which is set to get results early 2017. Will the results match our predictions, match the Z-machine, or give us something entirely different? The new platform brings new challenges such as designing hohlraums and spectrometers. The speaker will recount his history, starting with one-dimensional Monte Carlo nuclear criticality methods in graduate school, radiative transfer methods research and software development for his first 16 years at LANL, and, now, radflow technology and experiments. Who knew that the real world was more than just radiation transport? Experiments aren't easy, but they sure are fun.« less

Multi-phase Nature of a Radiation-driven Fountain with Nuclear Starburst in a Low-mass Active Galactic Nucleus

NASA Astrophysics Data System (ADS)

Wada, Keiichi; Schartmann, Marc; Meijerink, Rowin

2016-09-01

The structures and dynamics of molecular, atomic, and ionized gases are studied around a low-luminosity active galactic nucleus (AGN) with a small (2× {10}6{M}⊙ ) black hole using three-dimensional (3D) radiation-hydrodynamic simulations. We studied, for the first time, the non-equilibrium chemistry for the X-ray-dominated region in the “radiation-driven fountain” with supernova feedback. A double hollow cone structure is naturally formed without postulating a thick “torus” around a central source. The cone is occupied with an inhomogeneous, diffuse ionized gas and surrounded by a geometrically thick (h/r≳ 1) atomic gas. Dense molecular gases are distributed near the equatorial plane, and energy feedback from supernovae enhances their scale height. Molecular hydrogen exists in a hot phase (>1000 K) as well as in a cold (\\lt 100 {{K}}), dense (\\gt {10}3 {{cm}}-3) phase. The velocity dispersion of H2 in the vertical direction is comparable to the rotational velocity, which is consistent with near-infrared observations of nearby Seyfert galaxies. Using 3D radiation transfer calculations for the dust emission, we find polar emission in the mid-infrared band (12 μm), which is associated with bipolar outflows, as suggested in recent interferometric observations of nearby AGNs. If the viewing angle for the nucleus is larger than 75°, the spectral energy distribution is consistent with that of the Circinus galaxy. The multi-phase interstellar medium observed in optical/infrared and X-ray observations is also discussed.

Assessment of polarization effect on aerosol retrievals from MODIS

NASA Astrophysics Data System (ADS)

Korkin, S.; Lyapustin, A.

2010-12-01

Light polarization affects the total intensity of scattered radiation. In this work, we compare aerosol retrievals performed by code MAIAC [1] with and without taking polarization into account. The MAIAC retrievals are based on the look-up tables (LUT). For this work, MAIAC was run using two different LUTs, the first one generated using the scalar code SHARM [2], and the second one generated with the vector code Modified Vector Discrete Ordinates Method (MVDOM). MVDOM is a new code suitable for computations with highly anisotropic phase functions, including cirrus clouds and snow [3]. To this end, the solution of the vector radiative transfer equation (VRTE) is represented as a sum of anisotropic and regular components. The anisotropic component is evaluated in the Small Angle Modification of the Spherical Harmonics Method (MSH) [4]. The MSH is formulated in the frame of reference of the solar beam where z-axis lies along the solar beam direction. In this case, the MSH solution for anisotropic part is nearly symmetric in azimuth, and is computed analytically. In scalar case, this solution coincides with the Goudsmit-Saunderson small-angle approximation [5]. To correct for an analytical separation of the anisotropic part of the signal, the transfer equation for the regular part contains a correction source function term [6]. Several examples of polarization impact on aerosol retrievals over different surface types will be presented. 1. Lyapustin A., Wang Y., Laszlo I., Kahn R., Korkin S., Remer L., Levy R., and Reid J. S. Multi-Angle Implementation of Atmospheric Correction (MAIAC): Part 2. Aerosol Algorithm. J. Geophys. Res., submitted (2010). 2. Lyapustin A., Muldashev T., Wang Y. Code SHARM: fast and accurate radiative transfer over spatially variable anisotropic surfaces. In: Light Scattering Reviews 5. Chichester: Springer, 205 - 247 (2010). 3. Budak, V.P., Korkin S.V. On the solution of a vectorial radiative transfer equation in an arbitrary three-dimensional turbid medium with anisotropic scattering. JQSRT, 109, 220-234 (2008). 4. Budak V.P., Sarmin S.E. Solution of radiative transfer equation by the method of spherical harmonics in the small angle modification. Atmospheric and Oceanic Optics, 3, 898-903 (1990). 5. Goudsmit S., Saunderson J.L. Multiple scattering of electrons. Phys. Rev., 57, 24-29 (1940). 6. Budak V.P, Klyuykov D.A., Korkin S.V. Convergence acceleration of radiative transfer equation solution at strongly anisotropic scattering. In: Light Scattering Reviews 5. Chichester: Springer, 147 - 204 (2010).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lv, Q.; Kraus, A.; Hu, R.

CFD analysis has been focused on important component-level phenomena using STARCCM+ to supplement the system analysis of integral system behavior. A notable area of interest was the cavity region. This area is of particular interest for CFD analysis due to the multi-dimensional flow and complex heat transfer (thermal radiation heat transfer and natural convection), which are not simulated directly by RELAP5. CFD simulations allow for the estimation of the boundary heat flux distribution along the riser tubes, which is needed in the RELAP5 simulations. The CFD results can also provide additional data to help establish what level of modeling detailmore » is necessary in RELAP5. It was found that the flow profiles in the cavity region are simpler for the water-based concept than for the air-cooled concept. The local heat flux noticeably increases axially, and is higher in the fins than in the riser tubes. These results were utilized in RELAP5 simulations as boundary conditions, to provide better temperature predictions in the system level analyses. It was also determined that temperatures were higher in the fins than the riser tubes, but within design limits for thermal stresses. Higher temperature predictions were identified in the edge fins, in part due to additional thermal radiation from the side cavity walls.« less

Developing Present-day Proxy Cases Based on NARVAL Data for Investigating Low Level Cloud Responses to Future Climate Change.

NASA Astrophysics Data System (ADS)

Reilly, Stephanie

2017-04-01

The energy budget of the entire global climate is significantly influenced by the presence of boundary layer clouds. The main aim of the High Definition Clouds and Precipitation for Advancing Climate Prediction (HD(CP)2) project is to improve climate model predictions by means of process studies of clouds and precipitation. This study makes use of observed elevated moisture layers as a proxy of future changes in tropospheric humidity. The associated impact on radiative transfer triggers fast responses in boundary layer clouds, providing a framework for investigating this phenomenon. The investigation will be carried out using data gathered during the Next-generation Aircraft Remote-sensing for VALidation (NARVAL) South campaigns. Observational data will be combined with ECMWF reanalysis data to derive the large scale forcings for the Large Eddy Simulations (LES). Simulations will be generated for a range of elevated moisture layers, spanning a multi-dimensional phase space in depth, amplitude, elevation, and cloudiness. The NARVAL locations will function as anchor-points. The results of the large eddy simulations and the observations will be studied and compared in an attempt to determine how simulated boundary layer clouds react to changes in radiative transfer from the free troposphere. Preliminary LES results will be presented and discussed.

Efficient Radiative Transfer for Dynamically Evolving Stratified Atmospheres

NASA Astrophysics Data System (ADS)

Judge, Philip G.

2017-12-01

We present a fast multi-level and multi-atom non-local thermodynamic equilibrium radiative transfer method for dynamically evolving stratified atmospheres, such as the solar atmosphere. The preconditioning method of Rybicki & Hummer (RH92) is adopted. But, pressed for the need of speed and stability, a “second-order escape probability” scheme is implemented within the framework of the RH92 method, in which frequency- and angle-integrals are carried out analytically. While minimizing the computational work needed, this comes at the expense of numerical accuracy. The iteration scheme is local, the formal solutions for the intensities are the only non-local component. At present the methods have been coded for vertical transport, applicable to atmospheres that are highly stratified. The probabilistic method seems adequately fast, stable, and sufficiently accurate for exploring dynamical interactions between the evolving MHD atmosphere and radiation using current computer hardware. Current 2D and 3D dynamics codes do not include this interaction as consistently as the current method does. The solutions generated may ultimately serve as initial conditions for dynamical calculations including full 3D radiative transfer. The National Center for Atmospheric Research is sponsored by the National Science Foundation.

Radiative characterization of random fibrous media with long cylindrical fibers: Comparison of single- and multi-RTE approaches

NASA Astrophysics Data System (ADS)

Randrianalisoa, Jaona; Haussener, Sophia; Baillis, Dominique; Lipiński, Wojciech

2017-11-01

Radiative heat transfer is analyzed in participating media consisting of long cylindrical fibers with a diameter in the limit of geometrical optics. The absorption and scattering coefficients and the scattering phase function of the medium are determined based on the discrete-level medium geometry and optical properties of individual fibers. The fibers are assumed to be randomly oriented and positioned inside the medium. Two approaches are employed: a volume-averaged two-intensity approach referred to as multi-RTE approach and a homogenized single-intensity approach referred to as the single-RTE approach. Both approaches require effective properties, determined using direct Monte Carlo ray tracing techniques. The macroscopic radiative transfer equations (for single intensity or two volume-averaged intensities) with the corresponding effective properties are solved using Monte Carlo techniques and allow for the determination of the radiative flux distribution as well as overall transmittance and reflectance of the medium. The results are compared against predictions by the direct Monte Carlo simulation on the exact morphology. The effects of fiber volume fraction and optical properties on the effective radiative properties and the overall slab radiative characteristics are investigated. The single-RTE approach gives accurate predictions for high porosity fibrous media (porosity about 95%). The multi-RTE approach is recommended for isotropic fibrous media with porosity in the range of 79-95%.

Analytic Methods for Predicting Significant Multi-Quanta Effects in Collisional Molecular Energy Transfer

NASA Technical Reports Server (NTRS)

Bieniek, Ronald J.

1996-01-01

Collision-induced transitions can significantly affect molecular vibrational-rotational populations and energy transfer in atmospheres and gaseous systems. This, in turn. can strongly influence convective heat transfer through dissociation and recombination of diatomics. and radiative heat transfer due to strong vibrational coupling. It is necessary to know state-to-state rates to predict engine performance and aerothermodynamic behavior of hypersonic flows, to analyze diagnostic radiative data obtained from experimental test facilities, and to design heat shields and other thermal protective systems. Furthermore, transfer rates between vibrational and translational modes can strongly influence energy flow in various 'disturbed' environments, particularly where the vibrational and translational temperatures are not equilibrated.

Analysis of Radiation-natural Convection Interactions in 1-g and low-g Environments using the Discrete Exchange Factor Method

NASA Technical Reports Server (NTRS)

Kassemi, M.; Naraghi, M. H. N.

1993-01-01

A new numerical method is presented for the analysis of combined natural convection and radiation heat transfer with applications in many engineering situations such as materials processing, combustion and fire research. Because of the recent interest in the low gravity environment of space, attention is devoted to both 1-g and low-g applications. The two-dimensional mathematical model is represented by a set of coupled nonlinear integro-partial differential equations. Radiative exchange is formulated using the Discrete Exchange Factor method (DEF). This method considers point to point exchange and provides accurate results over a wide range of radiation parameters. Numerical results show that radiation significantly influences the flow and heat transfer in both low-g and 1-g applications. In the low-g environment, convection is weak, and radiation can easily become the dominant heat transfer mode. It is also shown that volumetric heating by radiation gives rise to an intricate cell pattern in the top heated enclosure.

Modeling the interaction between plant canopies and the planetary boundary layer using a new 1D multi-layer soil- vegetation-atmosphere transfer (SVAT) scheme combined with a non-local turbulence closure model

NASA Astrophysics Data System (ADS)

Yetzer, Kenneth H.

A new one-dimensional (1D) soil-vegetation-atmospheric transport (SVAT) scheme is coupled to a nonlocal turbulence closure model in order to simulate the interactions between a forested canopy and the planetary boundary layer. The SVAT consists of mechanistic models for both physiological (photosynthesis, stomatal conductance and soil/root and bole respiration) and micrometeorological (radiative transfer and surface energy exchanges) processes. The turbulence closure model is a first-order, nonlocal turbulence closure called transilient turbulence theory (Stull, 1993; Inclan et al., 1995) which includes the effects of form drag, wake turbulence, and interference to vertical mixing by the plant elements. The submodel that accounts for radiative transfer inside the forest has been taken from Norman (1979) and Baldocchi (1989). It includes the effect of varying mean leaf inclination angle with height and it also accounts for leaf clumping The photosynthesis submodel is taken from Nikolov and others (1995). It accounts for both differences between shaded and sunlit leaves and the variation of photosynthetic capacity with height. The model was tested with data obtained from a deciduous forest in Pennsylvania. The results show reasonable agreement with the observations. They also demonstrate the model's ability to simulate phenomena that is characteristic of tall canopies like forests, including counter gradient-fluxes and local wind speed maxima in the trunk space.

Comprehensive analysis of heat transfer of gold-blood nanofluid (Sisko-model) with thermal radiation

NASA Astrophysics Data System (ADS)

Eid, Mohamed R.; Alsaedi, Ahmed; Muhammad, Taseer; Hayat, Tasawar

Characteristics of heat transfer of gold nanoparticles (Au-NPs) in flow past a power-law stretching surface are discussed. Sisko bio-nanofluid flow (with blood as a base fluid) in existence of non-linear thermal radiation is studied. The resulting equations system is abbreviated to model the suggested problem in non-linear PDEs. Along with initial and boundary-conditions, the equations are made non-dimensional and then resolved numerically utilizing 4th-5th order Runge-Kutta-Fehlberg (RKF45) technique with shooting integration procedure. Various flow quantities behaviors are examined for parametric consideration such as the Au-NPs volume fraction, the exponentially stretching and thermal radiation parameters. It is observed that radiation drives to shortage the thermal boundary-layer thickness and therefore resulted in better heat transfer at surface.

On the calculation of dynamic and heat loads on a three-dimensional body in a hypersonic flow

NASA Astrophysics Data System (ADS)

Bocharov, A. N.; Bityurin, V. A.; Evstigneev, N. M.; Fortov, V. E.; Golovin, N. N.; Petrovskiy, V. P.; Ryabkov, O. I.; Teplyakov, I. O.; Shustov, A. A.; Solomonov, Yu S.

2018-01-01

We consider a three-dimensional body in a hypersonic flow at zero angle of attack. Our aim is to estimate heat and aerodynamic loads on specific body elements. We are considering a previously developed code to solve coupled heat- and mass-transfer problem. The change of the surface shape is taken into account by formation of the iterative process for the wall material ablation. The solution is conducted on the multi-graphics-processing-unit (multi-GPU) cluster. Five Mach number points are considered, namely for M = 20-28. For each point we estimate body shape after surface ablation, heat loads on the surface and aerodynamic loads on the whole body and its elements. The latter is done using Gauss-type quadrature on the surface of the body. The comparison of the results for different Mach numbers is performed. We also estimate the efficiency of the Navier-Stokes code on multi-GPU and central processing unit architecture for the coupled heat and mass transfer problem.

Radiation Heat Transfer Between Diffuse-Gray Surfaces Using Higher Order Finite Elements

NASA Technical Reports Server (NTRS)

Gould, Dana C.

2000-01-01

This paper presents recent work on developing methods for analyzing radiation heat transfer between diffuse-gray surfaces using p-version finite elements. The work was motivated by a thermal analysis of a High Speed Civil Transport (HSCT) wing structure which showed the importance of radiation heat transfer throughout the structure. The analysis also showed that refining the finite element mesh to accurately capture the temperature distribution on the internal structure led to very large meshes with unacceptably long execution times. Traditional methods for calculating surface-to-surface radiation are based on assumptions that are not appropriate for p-version finite elements. Two methods for determining internal radiation heat transfer are developed for one and two-dimensional p-version finite elements. In the first method, higher-order elements are divided into a number of sub-elements. Traditional methods are used to determine radiation heat flux along each sub-element and then mapped back to the parent element. In the second method, the radiation heat transfer equations are numerically integrated over the higher-order element. Comparisons with analytical solutions show that the integration scheme is generally more accurate than the sub-element method. Comparison to results from traditional finite elements shows that significant reduction in the number of elements in the mesh is possible using higher-order (p-version) finite elements.

Portable laser synthesizer for high-speed multi-dimensional spectroscopy

DOEpatents

Demos, Stavros G [Livermore, CA; Shverdin, Miroslav Y [Sunnyvale, CA; Shirk, Michael D [Brentwood, CA

2012-05-29

Portable, field-deployable laser synthesizer devices designed for multi-dimensional spectrometry and time-resolved and/or hyperspectral imaging include a coherent light source which simultaneously produces a very broad, energetic, discrete spectrum spanning through or within the ultraviolet, visible, and near infrared wavelengths. The light output is spectrally resolved and each wavelength is delayed with respect to each other. A probe enables light delivery to a target. For multidimensional spectroscopy applications, the probe can collect the resulting emission and deliver this radiation to a time gated spectrometer for temporal and spectral analysis.

An asymptotic preserving unified gas kinetic scheme for gray radiative transfer equations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Wenjun, E-mail: sun_wenjun@iapcm.ac.cn; Jiang, Song, E-mail: jiang@iapcm.ac.cn; Xu, Kun, E-mail: makxu@ust.hk

The solutions of radiative transport equations can cover both optical thin and optical thick regimes due to the large variation of photon's mean-free path and its interaction with the material. In the small mean free path limit, the nonlinear time-dependent radiative transfer equations can converge to an equilibrium diffusion equation due to the intensive interaction between radiation and material. In the optical thin limit, the photon free transport mechanism will emerge. In this paper, we are going to develop an accurate and robust asymptotic preserving unified gas kinetic scheme (AP-UGKS) for the gray radiative transfer equations, where the radiation transportmore » equation is coupled with the material thermal energy equation. The current work is based on the UGKS framework for the rarefied gas dynamics [14], and is an extension of a recent work [12] from a one-dimensional linear radiation transport equation to a nonlinear two-dimensional gray radiative system. The newly developed scheme has the asymptotic preserving (AP) property in the optically thick regime in the capturing of diffusive solution without using a cell size being smaller than the photon's mean free path and time step being less than the photon collision time. Besides the diffusion limit, the scheme can capture the exact solution in the optical thin regime as well. The current scheme is a finite volume method. Due to the direct modeling for the time evolution solution of the interface radiative intensity, a smooth transition of the transport physics from optical thin to optical thick can be accurately recovered. Many numerical examples are included to validate the current approach.« less

Generalized Radiative Transfer as an Efficient Computational Tool for Spatial and/or Spectral Integration over Unresolved Variability in Multi-Angle Observations

NASA Astrophysics Data System (ADS)

Davis, A. B.; Xu, F.; Diner, D. J.

2017-12-01

Two perennial problems in applied theoretical and computational radiative transfer (RT) are: (1) the impact of unresolved spatial variability on large-scale fluxes (in climate models) or radiances (in remote sensing); and (2) efficient-yet-accurate estimation of broadband spectral integrals in radiant energy budget estimation as well as in remote sensing, in particular, of trace gases.Generalized RT (GRT) is a modification of classic RT in an optical medium with uniform extinction where Beer's exponential law for direct transmission is replaced by a monotonically decreasing function with a slower power-law decay. In a convenient parameterized version of GRT, mean extinction replaces the uniform value and just one new property is introduced. As a non-dimensional metric for the unresolved variability, we use the square of the mean extinction coefficient divided by its variance. This parameter is also the exponent of the power-law tail of the modified transmission law.This specific form of sub-exponential transmission has explored for almost two decades in application to spatial variability in the presence of long-range correlations, much like in turbulent media such as clouds, with a focus on multiple scattering. It has also been proposed by Conley and Collins (JQSRT, 112, 1525-, 2011) to improve on the standard (weak-line) implementation of the correlated-k technique for efficient spectral integration.We have merged these two applications within a rigorous formulation of the combined problem, and solve the new integral RT equations in the single-scattering limit. The result is illustrated by addressing practical problems in multi-angle remote sensing of aerosols using the O2 A-band, an emerging methodology for passive profiling of coarse aerosols and clouds.

Global simulation of canopy scale sun-induced chlorophyll fluorescence with a 3 dimensional radiative transfer model

NASA Astrophysics Data System (ADS)

Kobayashi, H.; Yang, W.; Ichii, K.

2015-12-01

Global simulation of canopy scale sun-induced chlorophyll fluorescence with a 3 dimensional radiative transfer modelHideki Kobayashi, Wei Yang, and Kazuhito IchiiDepartment of Environmental Geochemical Cycle Research, Japan Agency for Marine-Earth Science and Technology3173-25, Showa-machi, Kanazawa-ku, Yokohama, Japan.Plant canopy scale sun-induced chlorophyll fluorescence (SIF) can be observed from satellites, such as Greenhouse gases Observation Satellite (GOSAT), Orbiting Carbon Observatory-2 (OCO-2), and Global Ozone Monitoring Experiment-2 (GOME-2), using Fraunhofer lines in the near infrared spectral domain [1]. SIF is used to infer photosynthetic capacity of plant canopy [2]. However, it is not well understoond how the leaf-level SIF emission contributes to the top of canopy directional SIF because SIFs observed by the satellites use the near infrared spectral domain where the multiple scatterings among leaves are not negligible. It is necessary to quantify the fraction of emission for each satellite observation angle. Absorbed photosynthetically active radiation of sunlit leaves are 100 times higher than that of shaded leaves. Thus, contribution of sunlit and shaded leaves to canopy scale directional SIF emission should also be quantified. Here, we show the results of global simulation of SIF using a 3 dimensional radiative transfer simulation with MODIS atmospheric (aerosol optical thickness) and land (land cover and leaf area index) products and a forest landscape data sets prepared for each land cover category. The results are compared with satellite-based SIF (e.g. GOME-2) and the gross primary production empirically estimated by FLUXNET and remote sensing data.

Nanofabrication

DOEpatents

Tuominen, Mark; Bal, Mustafa; Russell, Thomas P.; Ursache, Andrei

2007-03-13

Pathways to rapid and reliable fabrication of three-dimensional nanostructures are provided. Simple methods are described for the production of well-ordered, multilevel nanostructures. This is accomplished by patterning block copolymer templates with selective exposure to a radiation source. The resulting multi-scale lithographic template can be treated with post-fabrication steps to produce multilevel, three-dimensional, integrated nanoscale media, devices, and systems.

Millimeter wave radiative transfer studies for precipitation measurements

NASA Technical Reports Server (NTRS)

Vivekanandan, J.; Evans, Frank

1989-01-01

Scattering calculations using the discrete dipole approximation and vector radiative transfer calculations were performed to model multiparameter radar return and passive microwave emission for a simple model of a winter storm. The issue of dendrite riming was addressed by computing scattering properties of thin ice disks with varying bulk density. It was shown that C-band multiparameter radar contains information about particle density and the number concentration of the ice particles. The radiative transfer modeling indicated that polarized multifrequency passive microwave emission may be used to infer some properties of ice hydrometers. Detailed radar modeling and vector radiative transfer modeling is in progress to enhance the understanding of simultaneous radar and radiometer measurements, as in the case of the proposed TRMM field program. A one-dimensional cloud model will be used to simulate the storm structure in detail and study the microphysics, such as size and density. Multifrequency polarized radiometer measurements from the SSMI satellite instrument will be analyzed in relation to dual-frequency and dual-polarization radar measurements.

The Impact of a Discipline-Based Learning Community on Transfer Students: A Multi-Dimensional Pilot Study

ERIC Educational Resources Information Center

Lord, Vivian B.; Coston, Charisse T. M.; Blowers, Anita N.; Davis, Boyd; Johannes, Kenia S.

2012-01-01

Learning communities (LCs) have become a popular strategy for developing structured programming aimed at enhancing student success and retention. While most LCs have focused on improving the quality of education for first-year students, little attention has been placed on addressing their usefulness for enhancing the success of transfer students.…

Multi-dimensional modeling of a thermal energy storage canister. M.S. Thesis - Cleveland State Univ., Dec. 1990

NASA Technical Reports Server (NTRS)

Kerslake, Thomas W.

1991-01-01

The Solar Dynamic Power Module being developed for Space Station Freedom uses a eutectic mixture of LiF-CaF2 phase change material (PCM) contained in toroidal canisters for thermal energy storage. Presented are the results from heat transfer analyses of a PCM containment canister. One and two dimensional finite difference computer models are developed to analyze heat transfer in the canister walls, PCM, void, and heat engine working fluid coolant. The modes of heat transfer considered include conduction in canister walls and solid PCM, conduction and pseudo-free convection in liquid PCM, conduction and radiation across PCM vapor filled void regions, and forced convection in the heat engine working fluid. Void shape, location, growth or shrinkage (due to density difference between the solid and liquid PCM phases) are prescribed based on engineering judgment. The PCM phase change process is analyzed using the enthalpy method. The discussion of the results focuses on how canister thermal performance is affected by free convection in the liquid PCM and void heat transfer. Characterizing these effects is important for interpreting the relationship between ground-based canister performance (in 1-g) and expected on-orbit performance (in micro-g). Void regions accentuate canister hot spots and temperature gradients due to their large thermal resistance. Free convection reduces the extent of PCM superheating and lowers canister temperatures during a portion of the PCM thermal charge period. Surprisingly small differences in canister thermal performance result from operation on the ground and operation on-orbit. This lack of a strong gravity dependency is attributed to the large contribution of container walls in overall canister energy redistribution by conduction.

Numerical investigation of flow and heat transfer in a novel configuration multi-tubular fixed bed reactor for propylene to acrolein process

NASA Astrophysics Data System (ADS)

Jiang, Bin; Hao, Li; Zhang, Luhong; Sun, Yongli; Xiao, Xiaoming

2015-01-01

In the present contribution, a numerical study of fluid flow and heat transfer performance in a pilot-scale multi-tubular fixed bed reactor for propylene to acrolein oxidation reaction is presented using computational fluid dynamics (CFD) method. Firstly, a two-dimensional CFD model is developed to simulate flow behaviors, catalytic oxidation reaction, heat and mass transfer adopting porous medium model on tube side to achieve the temperature distribution and investigate the effect of operation parameters on hot spot temperature. Secondly, based on the conclusions of tube-side, a novel configuration multi-tubular fixed-bed reactor comprising 790 tubes design with disk-and-doughnut baffles is proposed by comparing with segmental baffles reactor and their performance of fluid flow and heat transfer is analyzed to ensure the uniformity condition using molten salt as heat carrier medium on shell-side by three-dimensional CFD method. The results reveal that comprehensive performance of the reactor with disk-and-doughnut baffles is better than that of with segmental baffles. Finally, the effects of operating conditions to control the hot spots are investigated. The results show that the flow velocity range about 0.65 m/s is applicable and the co-current cooling system flow direction is better than counter-current flow to control the hottest temperature.

Equivalent isotropic scattering formulation for transient short-pulse radiative transfer in anisotropic scattering planar media.

PubMed

Guo, Z; Kumar, S

2000-08-20

An isotropic scaling formulation is evaluated for transient radiative transfer in a one-dimensional planar slab subject to collimated and/or diffuse irradiation. The Monte Carlo method is used to implement the equivalent scattering and exact simulations of the transient short-pulse radiation transport through forward and backward anisotropic scattering planar media. The scaled equivalent isotropic scattering results are compared with predictions of anisotropic scattering in various problems. It is found that the equivalent isotropic scaling law is not appropriate for backward-scattering media in transient radiative transfer. Even for an optically diffuse medium, the differences in temporal transmittance and reflectance profiles between predictions of backward anisotropic scattering and equivalent isotropic scattering are large. Additionally, for both forward and backward anisotropic scattering media, the transient equivalent isotropic results are strongly affected by the change of photon flight time, owing to the change of flight direction associated with the isotropic scaling technique.

Verification and validation of an advanced model of heat and mass transfer in the protective clothing

NASA Astrophysics Data System (ADS)

Łapka, Piotr; Furmański, Piotr

2018-04-01

The paper presents verification and validation of an advanced numerical model of heat and moisture transfer in the multi-layer protective clothing and in components of the experimental stand subjected to either high surroundings temperature or high radiative heat flux emitted by hot objects. The developed model included conductive-radiative heat transfer in the hygroscopic porous fabrics and air gaps as well as conductive heat transfer in components of the stand. Additionally, water vapour diffusion in the pores and air spaces as well as phase transition of the bound water in the fabric fibres (sorption and desorption) were accounted for. All optical phenomena at internal or external walls were modelled and the thermal radiation was treated in the rigorous way, i.e., semi-transparent absorbing, emitting and scattering fabrics with the non-grey properties were assumed. The air was treated as transparent. Complex energy and mass balances as well as optical conditions at internal or external interfaces were formulated in order to find values of temperatures, vapour densities and radiation intensities at these interfaces. The obtained highly non-linear coupled system of discrete equations was solved by the Finite Volume based in-house iterative algorithm. The developed model passed discretisation convergence tests and was successfully verified against the results obtained applying commercial software for simplified cases. Then validation was carried out using experimental measurements collected during exposure of the protective clothing to high radiative heat flux emitted by the IR lamp. Satisfactory agreement of simulated and measured temporal variation of temperature at external and internal surfaces of the multi-layer clothing was attained.

Radiative interactions in chemically reacting compressible nozzle flows using Monte Carlo simulations

NASA Technical Reports Server (NTRS)

Liu, J.; Tiwari, Surendra N.

1994-01-01

The two-dimensional spatially elliptic Navier-Stokes equations have been used to investigate the radiative interactions in chemically reacting compressible flows of premixed hydrogen and air in an expanding nozzle. The radiative heat transfer term in the energy equation is simulated using the Monte Carlo method (MCM). The nongray model employed is based on the statistical narrow band model with an exponential-tailed inverse intensity distribution. The spectral correlation has been considered in the Monte Carlo formulations. Results obtained demonstrate that the effect of radiation on the flow field is minimal but its effect on the wall heat transfer is significant. Extensive parametric studies are conducted to investigate the effects of equivalence ratio, wall temperature, inlet flow temperature, and the nozzle size on the radiative and conductive wall fluxes.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ashraf, M. Bilal, E-mail: bilalashraf-qau@yahoo.com; Hayat, T.; Department of Mathematics, Faculty of Science, King Abdulaziz University, P. O. Box 80257, Jeddah 21589

Three dimensional radiative flow of Maxwell fluid over an inclined stretching surface with convective boundary condition is investigated. Heat and mass transfer analysis is taken into account with thermophoresis effects. Similarity transformations are utilized to reduce the partial differential equations into ordinary differential equations. Series solutions of velocity, temperature and concentration are developed. Influence of different parameters Biot number, therrmophoretic parameter, Deborah number, ratio parameter, inclined stretching angle, radiation parameter, mixed convection parameter and concentration buoyancy parameter on the non-dimensional velocity components, temperature and concentration are plotted and discussed in detail. Physical quantities of interests are tabulated and examined.

Correlated k-distribution method for radiative transfer in climate models: Application to effect of cirrus clouds on climate

NASA Technical Reports Server (NTRS)

Lacis, A. A.; Wang, W. C.; Hansen, J. E.

1979-01-01

A radiative transfer method appropriate for use in simple climate models and three dimensional global climate models was developed. It is fully interactive with climate changes, such as in the temperature-pressure profile, cloud distribution, and atmospheric composition, and it is accurate throughout the troposphere and stratosphere. The vertical inhomogeneity of the atmosphere is accounted for by assuming a correlation of gaseous k-distributions of different pressures and temperatures. Line-by-line calculations are made to demonstrate that The method is remarkably accurate. The method is then used in a one-dimensional radiative-convective climate model to study the effect of cirrus clouds on surface temperature. It is shown that an increase in cirrus cloud cover can cause a significant warming of the troposphere and the Earth's surface, by the mechanism of an enhanced green-house effect. The dependence of this phenomenon on cloud optical thickness, altitude, and latitude is investigated.

Asymmetric Base-Bleed Effect on Aerospike Plume-Induced Base-Heating Environment

NASA Technical Reports Server (NTRS)

Wang, Ten-See; Droege, Alan; DAgostino, Mark; Lee, Young-Ching; Williams, Robert

2004-01-01

A computational heat transfer design methodology was developed to study the dual-engine linear aerospike plume-induced base-heating environment during one power-pack out, in ascent flight. It includes a three-dimensional, finite volume, viscous, chemically reacting, and pressure-based computational fluid dynamics formulation, a special base-bleed boundary condition, and a three-dimensional, finite volume, and spectral-line-based weighted-sum-of-gray-gases absorption computational radiation heat transfer formulation. A separate radiation model was used for diagnostic purposes. The computational methodology was systematically benchmarked. In this study, near-base radiative heat fluxes were computed, and they compared well with those measured during static linear aerospike engine tests. The base-heating environment of 18 trajectory points selected from three power-pack out scenarios was computed. The computed asymmetric base-heating physics were analyzed. The power-pack out condition has the most impact on convective base heating when it happens early in flight. The source of its impact comes from the asymmetric and reduced base bleed.

Modeling of high pressure arc-discharge with a fully-implicit Navier-Stokes stabilized finite element flow solver

NASA Astrophysics Data System (ADS)

Sahai, A.; Mansour, N. N.; Lopez, B.; Panesi, M.

2017-05-01

This work addresses the modeling of high pressure electric discharge in an arc-heated wind tunnel. The combined numerical solution of Poisson’s equation, radiative transfer equations, and the set of Favre-averaged thermochemical nonequilibrium Navier-Stokes equations allows for the determination of the electric, radiation, and flow fields, accounting for their mutual interaction. Semi-classical statistical thermodynamics is used to determine the plasma thermodynamic properties, while transport properties are obtained from kinetic principles with the Chapman-Enskog method. A multi-temperature formulation is used to account for thermal non-equilibrium. Finally, the turbulence closure of the flow equations is obtained by means of the Spalart-Allmaras model, which requires the solution of an additional scalar transport equation. A Streamline upwind Petrov-Galerkin stabilized finite element formulation is employed to solve the Navier-Stokes equation. The electric field equation is solved using the standard Galerkin formulation. A stable formulation for the radiative transfer equations is obtained using the least-squares finite element method. The developed simulation framework has been applied to investigate turbulent plasma flows in the 20 MW Aerodynamic Heating Facility at NASA Ames Research Center. The current model is able to predict the process of energy addition and re-distribution due to Joule heating and thermal radiation, resulting in a hot central core surrounded by colder flow. The use of an unsteady three-dimensional treatment also allows the asymmetry due to a dynamic electric arc attachment point in the cathode chamber to be captured accurately. The current work paves the way for detailed estimation of operating characteristics for arc-heated wind tunnels which are critical in testing thermal protection systems.

FluorWPS: A Monte Carlo ray-tracing model to compute sun-induced chlorophyll fluorescence of three-dimensional canopy

USDA-ARS?s Scientific Manuscript database

A model to simulate radiative transfer (RT) of sun-induced chlorophyll fluorescence (SIF) of three-dimensional (3-D) canopy, FluorWPS, was proposed and evaluated. The inclusion of fluorescence excitation was implemented with the ‘weight reduction’ and ‘photon spread’ concepts based on Monte Carlo ra...

Bayesian Atmospheric Radiative Transfer (BART) Code and Application to WASP-43b

NASA Astrophysics Data System (ADS)

Blecic, Jasmina; Harrington, Joseph; Cubillos, Patricio; Bowman, Oliver; Rojo, Patricio; Stemm, Madison; Lust, Nathaniel B.; Challener, Ryan; Foster, Austin James; Foster, Andrew S.; Blumenthal, Sarah D.; Bruce, Dylan

2016-01-01

We present a new open-source Bayesian radiative-transfer framework, Bayesian Atmospheric Radiative Transfer (BART, https://github.com/exosports/BART), and its application to WASP-43b. BART initializes a model for the atmospheric retrieval calculation, generates thousands of theoretical model spectra using parametrized pressure and temperature profiles and line-by-line radiative-transfer calculation, and employs a statistical package to compare the models with the observations. It consists of three self-sufficient modules available to the community under the reproducible-research license, the Thermochemical Equilibrium Abundances module (TEA, https://github.com/dzesmin/TEA, Blecic et al. 2015}, the radiative-transfer module (Transit, https://github.com/exosports/transit), and the Multi-core Markov-chain Monte Carlo statistical module (MCcubed, https://github.com/pcubillos/MCcubed, Cubillos et al. 2015). We applied BART on all available WASP-43b secondary eclipse data from the space- and ground-based observations constraining the temperature-pressure profile and molecular abundances of the dayside atmosphere of WASP-43b. This work was supported by NASA Planetary Atmospheres grant NNX12AI69G and NASA Astrophysics Data Analysis Program grant NNX13AF38G. JB holds a NASA Earth and Space Science Fellowship.

A patient-specific computational model of hypoxia-modulated radiation resistance in glioblastoma using 18F-FMISO-PET

PubMed Central

Rockne, Russell C.; Trister, Andrew D.; Jacobs, Joshua; Hawkins-Daarud, Andrea J.; Neal, Maxwell L.; Hendrickson, Kristi; Mrugala, Maciej M.; Rockhill, Jason K.; Kinahan, Paul; Krohn, Kenneth A.; Swanson, Kristin R.

2015-01-01

Glioblastoma multiforme (GBM) is a highly invasive primary brain tumour that has poor prognosis despite aggressive treatment. A hallmark of these tumours is diffuse invasion into the surrounding brain, necessitating a multi-modal treatment approach, including surgery, radiation and chemotherapy. We have previously demonstrated the ability of our model to predict radiographic response immediately following radiation therapy in individual GBM patients using a simplified geometry of the brain and theoretical radiation dose. Using only two pre-treatment magnetic resonance imaging scans, we calculate net rates of proliferation and invasion as well as radiation sensitivity for a patient's disease. Here, we present the application of our clinically targeted modelling approach to a single glioblastoma patient as a demonstration of our method. We apply our model in the full three-dimensional architecture of the brain to quantify the effects of regional resistance to radiation owing to hypoxia in vivo determined by [18F]-fluoromisonidazole positron emission tomography (FMISO-PET) and the patient-specific three-dimensional radiation treatment plan. Incorporation of hypoxia into our model with FMISO-PET increases the model–data agreement by an order of magnitude. This improvement was robust to our definition of hypoxia or the degree of radiation resistance quantified with the FMISO-PET image and our computational model, respectively. This work demonstrates a useful application of patient-specific modelling in personalized medicine and how mathematical modelling has the potential to unify multi-modality imaging and radiation treatment planning. PMID:25540239

MULTI2D - a computer code for two-dimensional radiation hydrodynamics

NASA Astrophysics Data System (ADS)

Ramis, R.; Meyer-ter-Vehn, J.; Ramírez, J.

2009-06-01

Simulation of radiation hydrodynamics in two spatial dimensions is developed, having in mind, in particular, target design for indirectly driven inertial confinement energy (IFE) and the interpretation of related experiments. Intense radiation pulses by laser or particle beams heat high-Z target configurations of different geometries and lead to a regime which is optically thick in some regions and optically thin in others. A diffusion description is inadequate in this situation. A new numerical code has been developed which describes hydrodynamics in two spatial dimensions (cylindrical R-Z geometry) and radiation transport along rays in three dimensions with the 4 π solid angle discretized in direction. Matter moves on a non-structured mesh composed of trilateral and quadrilateral elements. Radiation flux of a given direction enters on two (one) sides of a triangle and leaves on the opposite side(s) in proportion to the viewing angles depending on the geometry. This scheme allows to propagate sharply edged beams without ray tracing, though at the price of some lateral diffusion. The algorithm treats correctly both the optically thin and optically thick regimes. A symmetric semi-implicit (SSI) method is used to guarantee numerical stability. Program summaryProgram title: MULTI2D Catalogue identifier: AECV_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AECV_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 151 098 No. of bytes in distributed program, including test data, etc.: 889 622 Distribution format: tar.gz Programming language: C Computer: PC (32 bits architecture) Operating system: Linux/Unix RAM: 2 Mbytes Word size: 32 bits Classification: 19.7 External routines: X-window standard library (libX11.so) and corresponding heading files (X11/*.h) are required. Nature of problem: In inertial confinement fusion and related experiments with lasers and particle beams, energy transport by thermal radiation becomes important. Under these conditions, the radiation field strongly interacts with the hydrodynamic motion through emission and absorption processes. Solution method: The equations of radiation transfer coupled with Lagrangian hydrodynamics, heat diffusion and beam tracing (laser or ions) are solved, in two-dimensional axial-symmetric geometry ( R-Z coordinates) using a fractional step scheme. Radiation transfer is solved with angular resolution. Matter properties are either interpolated from tables (equations-of-state and opacities) or computed by user routines (conductivities and beam attenuation). Restrictions: The code has been designed for typical conditions prevailing in inertial confinement fusion (ns time scale, matter states close to local thermodynamical equilibrium, negligible radiation pressure, …). Although a wider range of situations can be treated, extrapolations to regions beyond this design range need special care. Unusual features: A special computer language, called r94, is used at top levels of the code. These parts have to be converted to standard C by a translation program (supplied as part of the package). Due to the complexity of code (hydro-code, grid generation, user interface, graphic post-processor, translator program, installation scripts) extensive manuals are supplied as part of the package. Running time: 567 seconds for the example supplied.

Linearized Flux Evolution (LiFE): A technique for rapidly adapting fluxes from full-physics radiative transfer models

NASA Astrophysics Data System (ADS)

Robinson, Tyler D.; Crisp, David

2018-05-01

Solar and thermal radiation are critical aspects of planetary climate, with gradients in radiative energy fluxes driving heating and cooling. Climate models require that radiative transfer tools be versatile, computationally efficient, and accurate. Here, we describe a technique that uses an accurate full-physics radiative transfer model to generate a set of atmospheric radiative quantities which can be used to linearly adapt radiative flux profiles to changes in the atmospheric and surface state-the Linearized Flux Evolution (LiFE) approach. These radiative quantities describe how each model layer in a plane-parallel atmosphere reflects and transmits light, as well as how the layer generates diffuse radiation by thermal emission and by scattering light from the direct solar beam. By computing derivatives of these layer radiative properties with respect to dynamic elements of the atmospheric state, we can then efficiently adapt the flux profiles computed by the full-physics model to new atmospheric states. We validate the LiFE approach, and then apply this approach to Mars, Earth, and Venus, demonstrating the information contained in the layer radiative properties and their derivatives, as well as how the LiFE approach can be used to determine the thermal structure of radiative and radiative-convective equilibrium states in one-dimensional atmospheric models.

Solar Radiation Transport in the Cloudy Atmosphere: A 3D Perspective on Observations and Climate Impacts

NASA Technical Reports Server (NTRS)

Davis, Anthony B.; Marshak, Alexander

2010-01-01

The interplay of sunlight with clouds is a ubiquitous and often pleasant visual experience, but it conjures up major challenges for weather, climate, environmental science and beyond. Those engaged in the characterization of clouds (and the clear air nearby) by remote sensing methods are even more confronted. The problem comes, on the one hand, from the spatial complexity of real clouds and, on the other hand, from the dominance of multiple scattering in the radiation transport. The former ingredient contrasts sharply with the still popular representation of clouds as homogeneous plane-parallel slabs for the purposes of radiative transfer computations. In typical cloud scenes the opposite asymptotic transport regimes of diffusion and ballistic propagation coexist. We survey the three-dimensional (3D) atmospheric radiative transfer literature over the past 50 years and identify three concurrent and intertwining thrusts: first, how to assess the damage (bias) caused by 3D effects in the operational 1D radiative transfer models? Second, how to mitigate this damage? Finally, can we exploit 3D radiative transfer phenomena to innovate observation methods and technologies? We quickly realize that the smallest scale resolved computationally or observationally may be artificial but is nonetheless a key quantity that separates the 3D radiative transfer solutions into two broad and complementary classes: stochastic and deterministic. Both approaches draw on classic and contemporary statistical, mathematical and computational physics.

A journey from nuclear criticality methods to high energy density radflow experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Urbatsch, Todd James

Los Alamos National Laboratory is a nuclear weapons laboratory supporting our nation's defense. In support of this mission is a high energy-density physics program in which we design and execute experiments to study radiationhydrodynamics phenomena and improve the predictive capability of our largescale multi-physics software codes on our big-iron computers. The Radflow project’s main experimental effort now is to understand why we haven't been able to predict opacities on Sandia National Laboratory's Z-machine. We are modeling an increasing fraction of the Z-machine's dynamic hohlraum to find multi-physics explanations for the experimental results. Further, we are building an entirely different opacitymore » platform on Lawrence Livermore National Laboratory's National Ignition Facility (NIF), which is set to get results early 2017. Will the results match our predictions, match the Z-machine, or give us something entirely different? The new platform brings new challenges such as designing hohlraums and spectrometers. The speaker will recount his history, starting with one-dimensional Monte Carlo nuclear criticality methods in graduate school, radiative transfer methods research and software development for his first 16 years at LANL, and, now, radflow technology and experiments. Who knew that the real world was more than just radiation transport? Experiments aren't easy and they are as saturated with politics as a presidential election, but they sure are fun.« less

Supernova Light Curves and Spectra from Two Different Codes: Supernu and Phoenix

NASA Astrophysics Data System (ADS)

Van Rossum, Daniel R; Wollaeger, Ryan T

2014-08-01

The observed similarities between light curve shapes from Type Ia supernovae, and in particular the correlation of light curve shape and brightness, have been actively studied for more than two decades. In recent years, hydronamic simulations of white dwarf explosions have advanced greatly, and multiple mechanisms that could potentially produce Type Ia supernovae have been explored in detail. The question which of the proposed mechanisms is (or are) possibly realized in nature remains challenging to answer, but detailed synthetic light curves and spectra from explosion simulations are very helpful and important guidelines towards answering this question.We present results from a newly developed radiation transport code, Supernu. Supernu solves the supernova radiation transfer problem uses a novel technique based on a hybrid between Implicit Monte Carlo and Discrete Diffusion Monte Carlo. This technique enhances the efficiency with respect to traditional implicit monte carlo codes and thus lends itself perfectly for multi-dimensional simulations. We show direct comparisons of light curves and spectra from Type Ia simulations with Supernu versus the legacy Phoenix code.

Projection methods for line radiative transfer in spherical media.

NASA Astrophysics Data System (ADS)

Anusha, L. S.; Nagendra, K. N.

An efficient numerical method called the Preconditioned Bi-Conjugate Gradient (Pre-BiCG) method is presented for the solution of radiative transfer equation in spherical geometry. A variant of this method called Stabilized Preconditioned Bi-Conjugate Gradient (Pre-BiCG-STAB) is also presented. These methods are based on projections on the subspaces of the n dimensional Euclidean space mathbb {R}n called Krylov subspaces. The methods are shown to be faster in terms of convergence rate compared to the contemporary iterative methods such as Jacobi, Gauss-Seidel and Successive Over Relaxation (SOR).

New numerical method for radiation heat transfer in nonhomogeneous participating media

DOE Office of Scientific and Technical Information (OSTI.GOV)

Howell, J.R.; Tan, Zhiqiang

A new numerical method, which solves the exact integral equations of distance-angular integration form for radiation transfer, is introduced in this paper. By constructing and prestoring the numerical integral formulas for the distance integral for appropriate kernel functions, this method eliminates the time consuming evaluations of the kernels of the space integrals in the formal computations. In addition, when the number of elements in the system is large, the resulting coefficient matrix is quite sparse. Thus, either considerable time or much storage can be saved. A weakness of the method is discussed, and some remedies are suggested. As illustrations, somemore » one-dimensional and two-dimensional problems in both homogeneous and inhomogeneous emitting, absorbing, and linear anisotropic scattering media are studied. Some results are compared with available data. 13 refs.« less

Polarization as a probe of dusty environments around Type Ia supernovae: radiative transfer models for SN 2012dn

NASA Astrophysics Data System (ADS)

Nagao, Takashi; Maeda, Keiichi; Yamanaka, Masayuki

2018-06-01

The geometry of the circumstellar (CS) medium around supernovae (SNe) provides important diagnostics to understand the nature of their progenitors. In this article, the properties of CS dust around SN 2012dn, a super-Chandrasekhar candidate Type Ia supernova (SC-SN), have been studied through detailed three-dimensional radiation transfer simulations. Using the detected near-infrared excess from SN 2012dn, we show that it has a disc-like dusty CS environment, the mass of which is roughly consistent with a branch of an accreting white dwarf system (the single degenerate scenario). We show that a similar system should produce polarization signals up to ˜8 per cent in the B band, depending on the viewing direction if polarimetric observations are performed. We predict that maximum polarization is reached around ˜60 d after the B-band maximum. We show that the temporal and wavelength dependence of the polarization signals, together with other unique features, can be easily distinguished from the interstellar polarization and intrinsic SN polarization. Indeed, the small polarization degree observed for normal Type Ia SNe (SNe Ia) can constrain a parameter space in CS dust mass and distribution. We thus encourage multi-band polarimetric observations for SNe Ia, especially for outliers including SC-SNe, for which some arguments for the single degenerate scenario exist but polarization data are very rare so far.

Consistent radiative transfer modeling of active and passive observations of precipitation

NASA Astrophysics Data System (ADS)

Adams, Ian

2016-04-01

Spaceborne platforms such as the Tropical Rainfall Measurement Mission (TRMM) and the Global Precipitation Measurement (GPM) mission exploit a combination of active and passive sensors to provide a greater understanding of the three-dimensional structure of precipitation. While "operationalized" retrieval algorithms require fast forward models, the ability to perform higher fidelity simulations is necessary in order to understand the physics of remote sensing problems by testing assumptions and developing parameterizations for the fast models. To ensure proper synergy between active and passive modeling, forward models must be consistent when modeling the responses of radars and radiometers. This work presents a self-consistent transfer model for simulating radar reflectivities and millimeter wave brightness temperatures for precipitating scenes. To accomplish this, we extended the Atmospheric Radiative Transfer Simulator (ARTS) version 2.3 to solve the radiative transfer equation for active sensors and multiple scattering conditions. Early versions of ARTS (1.1) included a passive Monte Carlo solver, and ARTS is capable of handling atmospheres of up to three dimensions with ellipsoidal planetary geometries. The modular nature of ARTS facilitates extensibility, and the well-developed ray-tracing tools are suited for implementation of Monte Carlo algorithms. Finally, since ARTS handles the full Stokes vector, co- and cross-polarized reflectivity products are possible for scenarios that include nonspherical particles, with or without preferential alignment. The accuracy of the forward model will be demonstrated with precipitation events observed by TRMM and GPM, and the effects of multiple scattering will be detailed. The three-dimensional nature of the radiative transfer model will be useful for understanding the effects of nonuniform beamfill and multiple scattering for spatially heterogeneous precipitation events. The targets of this forward model are GPM (the Dual-wavelength Precipitation Radar (DPR) and GPM Microwave Imager (GMI)).

Beyond multi-fractals: surrogate time series and fields

NASA Astrophysics Data System (ADS)

Venema, V.; Simmer, C.

2007-12-01

Most natural complex are characterised by variability on a large range of temporal and spatial scales. The two main methodologies to generate such structures are Fourier/FARIMA based algorithms and multifractal methods. The former is restricted to Gaussian data, whereas the latter requires the structure to be self-similar. This work will present so-called surrogate data as an alternative that works with any (empirical) distribution and power spectrum. The best-known surrogate algorithm is the iterative amplitude adjusted Fourier transform (IAAFT) algorithm. We have studied six different geophysical time series (two clouds, runoff of a small and a large river, temperature and rain) and their surrogates. The power spectra and consequently the 2nd order structure functions were replicated accurately. Even the fourth order structure function was more accurately reproduced by the surrogates as would be possible by a fractal method, because the measured structure deviated too strong from fractal scaling. Only in case of the daily rain sums a fractal method could have been more accurate. Just as Fourier and multifractal methods, the current surrogates are not able to model the asymmetric increment distributions observed for runoff, i.e., they cannot reproduce nonlinear dynamical processes that are asymmetric in time. Furthermore, we have found differences for the structure functions on small scales. Surrogate methods are especially valuable for empirical studies, because the time series and fields that are generated are able to mimic measured variables accurately. Our main application is radiative transfer through structured clouds. Like many geophysical fields, clouds can only be sampled sparsely, e.g. with in-situ airborne instruments. However, for radiative transfer calculations we need full 3-dimensional cloud fields. A first study relating the measured properties of the cloud droplets and the radiative properties of the cloud field by generating surrogate cloud fields yielded good results within the measurement error. A further test of the suitability of the surrogate clouds for radiative transfer is evaluated by comparing the radiative properties of model cloud fields of sparse cumulus and stratocumulus with their surrogate fields. The bias and root mean square error in various radiative properties is small and the deviations in the radiances and irradiances are not statistically significant, i.e. these deviations can be attributed to the Monte Carlo noise of the radiative transfer calculations. We compared these results with optical properties of synthetic clouds that have either the correct distribution (but no spatial correlations) or the correct power spectrum (but a Gaussian distribution). These clouds did show statistical significant deviations. For more information see: http://www.meteo.uni-bonn.de/venema/themes/surrogates/

A vector radiative transfer model for coupled atmosphere and ocean systems based on successive order of scattering method.

PubMed

Zhai, Peng-Wang; Hu, Yongxiang; Trepte, Charles R; Lucker, Patricia L

2009-02-16

A vector radiative transfer model has been developed for coupled atmosphere and ocean systems based on the Successive Order of Scattering (SOS) Method. The emphasis of this study is to make the model easy-to-use and computationally efficient. This model provides the full Stokes vector at arbitrary locations which can be conveniently specified by users. The model is capable of tracking and labeling different sources of the photons that are measured, e.g. water leaving radiances and reflected sky lights. This model also has the capability to separate florescence from multi-scattered sunlight. The delta - fit technique has been adopted to reduce computational time associated with the strongly forward-peaked scattering phase matrices. The exponential - linear approximation has been used to reduce the number of discretized vertical layers while maintaining the accuracy. This model is developed to serve the remote sensing community in harvesting physical parameters from multi-platform, multi-sensor measurements that target different components of the atmosphere-oceanic system.

Bridging the Radiative Transfer Models for Meteorology and Solar Energy Applications

NASA Astrophysics Data System (ADS)

Xie, Y.; Sengupta, M.

2017-12-01

Radiative transfer models are used to compute solar radiation reaching the earth surface and play an important role in both meteorology and solar energy studies. Therefore, they are designed to meet the needs of specialized applications. For instance, radiative transfer models for meteorology seek to provide more accurate cloudy-sky radiation compared to models used in solar energy that are geared towards accuracy in clear-sky conditions associated with the maximum solar resource. However, models for solar energy applications are often computationally faster, as the complex solution of the radiative transfer equation is parameterized by atmospheric properties that can be acquired from surface- or satellite-based observations. This study introduces the National Renewable Energy Laboratory's (NREL's) recent efforts to combine the advantages of radiative transfer models designed for meteorology and solar energy applictions. A fast all-sky radiation model, FARMS-NIT, was developed to efficiently compute narrowband all-sky irradiances over inclined photovoltaic (PV) panels. This new model utilizes the optical preperties from a solar energy model, SMARTS, to computes surface radiation by considering all possible paths of photon transmission and the relevent scattering and absorption attenuation. For cloudy-sky conditions, cloud bidirectional transmittance functions (BTDFs) are provided by a precomputed lookup table (LUT) by LibRadtran. Our initial results indicate that FARMS-NIT has an accuracy that is similar to LibRadtran, a highly accurate multi-stream model, but is significantly more efficient. The development and validation of this model will be presented.

Heat transfer evaluation in a plasma core reactor

NASA Technical Reports Server (NTRS)

Smith, D. E.; Smith, T. M.; Stoenescu, M. L.

1976-01-01

Numerical evaluations of heat transfer in a fissioning uranium plasma core reactor cavity, operating with seeded hydrogen propellant, was performed. A two-dimensional analysis is based on an assumed flow pattern and cavity wall heat exchange rate. Various iterative schemes were required by the nature of the radiative field and by the solid seed vaporization. Approximate formulations of the radiative heat flux are generally used, due to the complexity of the solution of a rigorously formulated problem. The present work analyzes the sensitivity of the results with respect to approximations of the radiative field, geometry, seed vaporization coefficients and flow pattern. The results present temperature, heat flux, density and optical depth distributions in the reactor cavity, acceptable simplifying assumptions, and iterative schemes. The present calculations, performed in cartesian and spherical coordinates, are applicable to any most general heat transfer problem.

Results from Core-collapse Simulations with Multi-dimensional, Multi-angle Neutrino Transport

NASA Astrophysics Data System (ADS)

Brandt, Timothy D.; Burrows, Adam; Ott, Christian D.; Livne, Eli

2011-02-01

We present new results from the only two-dimensional multi-group, multi-angle calculations of core-collapse supernova evolution. The first set of results from these calculations was published in 2008 by Ott et al. We have followed a nonrotating and a rapidly rotating 20 M sun model for ~400 ms after bounce. We show that the radiation fields vary much less with angle than the matter quantities in the region of net neutrino heating. This happens because most neutrinos are emitted from inner radiative regions and because the specific intensity is an integral over sources from many angles at depth. The latter effect can only be captured by multi-angle transport. We then compute the phase relationship between dipolar oscillations in the shock radius and in matter and radiation quantities throughout the post-shock region. We demonstrate a connection between variations in neutrino flux and the hydrodynamical shock oscillations, and use a variant of the Rayleigh test to estimate the detectability of these neutrino fluctuations in IceCube and Super-Kamiokande. Neglecting flavor oscillations, fluctuations in our nonrotating model would be detectable to ~10 kpc in IceCube, and a detailed power spectrum could be measured out to ~5 kpc. These distances are considerably lower in our rapidly rotating model or with significant flavor oscillations. Finally, we measure the impact of rapid rotation on detectable neutrino signals. Our rapidly rotating model has strong, species-dependent asymmetries in both its peak neutrino flux and its light curves. The peak flux and decline rate show pole-equator ratios of up to ~3 and ~2, respectively.

Reflection of solar radiation by a cylindrical cloud

NASA Technical Reports Server (NTRS)

Smith, G. L.

1989-01-01

Potential applications of an analytic method for computing the solar radiation reflected by a cylindrical cloud are discussed, including studies of radiative transfer within finite clouds and evaluations of these effects on other clouds and on remote sensing problems involving finite clouds. The pattern of reflected sunlight from a cylindrical cloud as seen at a large distance has been considered and described by the bidirectional function method for finite cloud analysis, as previously studied theoretically for plane-parallel atmospheres by McKee and Cox (1974); Schmetz and Raschke (1981); and Stuhlmann et al. (1985). However, the lack of three-dimensional radiative transfer solutions for anisotropic scattering media have hampered theoretical investigations of bidirectional functions for finite clouds. The present approach permits expression of the directional variation of the radiation field as a spherical harmonic series to any desired degree and order.

Modeling multi-layer effects in passive microwave remote sensing of dry snow using Dense Media Radiative Transfer Theory (DMRT) based on quasicrystalline approximation

USGS Publications Warehouse

Liang, D.; Xu, X.; Tsang, L.; Andreadis, K.M.; Josberger, E.G.

2008-01-01

The Dense Media Radiative Transfer theory (DMRT) of Quasicrystalline Approximation of Mie scattering by sticky particles is used to study the multiple scattering effects in layered snow in microwave remote sensing. Results are illustrated for various snow profile characteristics. Polarization differences and frequency dependences of multilayer snow model are significantly different from that of the single-layer snow model. Comparisons are also made with CLPX data using snow parameters as given by the VIC model. ?? 2007 IEEE.

Statistics Analysis of the Uncertainties in Cloud Optical Depth Retrievals Caused by Three-Dimensional Radiative Effects

NASA Technical Reports Server (NTRS)

Varnai, Tamas; Marshak, Alexander

2000-01-01

This paper presents a simple approach to estimate the uncertainties that arise in satellite retrievals of cloud optical depth when the retrievals use one-dimensional radiative transfer theory for heterogeneous clouds that have variations in all three dimensions. For the first time, preliminary error bounds are set to estimate the uncertainty of cloud optical depth retrievals. These estimates can help us better understand the nature of uncertainties that three-dimensional effects can introduce into retrievals of this important product of the MODIS instrument. The probability distribution of resulting retrieval errors is examined through theoretical simulations of shortwave cloud reflection for a wide variety of cloud fields. The results are used to illustrate how retrieval uncertainties change with observable and known parameters, such as solar elevation or cloud brightness. Furthermore, the results indicate that a tendency observed in an earlier study, clouds appearing thicker for oblique sun, is indeed caused by three-dimensional radiative effects.

An Introduction to Atmospheric Radiation: Review for the Bulletin of AMS

NASA Technical Reports Server (NTRS)

Marshak, Alexander

2003-01-01

Whether you like a certain geophysical book or not, largely depends on your background. The field of radiative transfer and atmospheric radiation, in particular, combines people with a wide range of mathematical skills: from theoretical astrophysicists and nuclear physicists to meteorologists and ecologists. There is always a delicate balance between physical explanations and their mathematical interpretations. This balance is very personal and is based on your background. I came to the field of atmospheric radiative transfer as a mathematician with little knowledge of atmospheric physics. After being in the field for more than a decade, I still have gaps in my atmospheric science education. Thus I assess a radiative transfer book fi-om two main criteria: how well does it describe the material that is familiar to me (the radiative transfer equation and its numerical solutions) and how well does it help me to fill the gaps in my personal knowledge. So I present this review fi-om the perspective of a former mathematician working in the field of atmospheric radiation. . After being asked to review the book, my first intention was to compare the new edition with the previous one (Liou, 1980). In doing so, you can clearly follow the progress made in the field of atmospheric radiation over the past two decades. If there are few changes (as in Fundamental Radiative Transfer) or no changes at all (as in the Maxwell s equations), then the field has not seen much development. To the contrary, many differences between the two editions illustrate areas of major progress in the field, such as evidenced in Thermal Ineared Radiative Transfer and even in the creations of completely new fields like Three-Dimensional Radiative Transfer or Light Scattering by Nonspherical Particles. Obviously, the major changes happened not in the theory, which is at least half a century old, but in data quality and completely new measurements (mostly due to new satellite data) with higher accuracy and more reliability. The new edition illustrates this progress well.

Principal Component-Based Radiative Transfer Model (PCRTM) for Hyperspectral Sensors. Part I; Theoretical Concept

NASA Technical Reports Server (NTRS)

Liu, Xu; Smith, William L.; Zhou, Daniel K.; Larar, Allen

2005-01-01

Modern infrared satellite sensors such as Atmospheric Infrared Sounder (AIRS), Cosmic Ray Isotope Spectrometer (CrIS), Thermal Emission Spectrometer (TES), Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS) and Infrared Atmospheric Sounding Interferometer (IASI) are capable of providing high spatial and spectral resolution infrared spectra. To fully exploit the vast amount of spectral information from these instruments, super fast radiative transfer models are needed. This paper presents a novel radiative transfer model based on principal component analysis. Instead of predicting channel radiance or transmittance spectra directly, the Principal Component-based Radiative Transfer Model (PCRTM) predicts the Principal Component (PC) scores of these quantities. This prediction ability leads to significant savings in computational time. The parameterization of the PCRTM model is derived from properties of PC scores and instrument line shape functions. The PCRTM is very accurate and flexible. Due to its high speed and compressed spectral information format, it has great potential for super fast one-dimensional physical retrievals and for Numerical Weather Prediction (NWP) large volume radiance data assimilation applications. The model has been successfully developed for the National Polar-orbiting Operational Environmental Satellite System Airborne Sounder Testbed - Interferometer (NAST-I) and AIRS instruments. The PCRTM model performs monochromatic radiative transfer calculations and is able to include multiple scattering calculations to account for clouds and aerosols.

An interface for simulating radiative transfer in and around volcanic plumes with the Monte Carlo radiative transfer model McArtim

USGS Publications Warehouse

Kern, Christoph

2016-03-23

This report describes two software tools that, when used as front ends for the three-dimensional backward Monte Carlo atmospheric-radiative-transfer model (RTM) McArtim, facilitate the generation of lookup tables of volcanic-plume optical-transmittance characteristics in the ultraviolet/visible-spectral region. In particular, the differential optical depth and derivatives thereof (that is, weighting functions), with regard to a change in SO2 column density or aerosol optical thickness, can be simulated for a specific measurement geometry and a representative range of plume conditions. These tables are required for the retrieval of SO2 column density in volcanic plumes, using the simulated radiative-transfer/differential optical-absorption spectroscopic (SRT-DOAS) approach outlined by Kern and others (2012). This report, together with the software tools published online, is intended to make this sophisticated SRT-DOAS technique available to volcanologists and gas geochemists in an operational environment, without the need for an indepth treatment of the underlying principles or the low-level interface of the RTM McArtim.

Holographic leaky-wave metasurfaces for dual-sensor imaging.

PubMed

Li, Yun Bo; Li, Lian Lin; Cai, Ben Geng; Cheng, Qiang; Cui, Tie Jun

2015-12-10

Metasurfaces have huge potentials to develop new type imaging systems due to their abilities of controlling electromagnetic waves. Here, we propose a new method for dual-sensor imaging based on cross-like holographic leaky-wave metasurfaces which are composed of hybrid isotropic and anisotropic surface impedance textures. The holographic leaky-wave radiations are generated by special impedance modulations of surface waves excited by the sensor ports. For one independent sensor, the main leaky-wave radiation beam can be scanned by frequency in one-dimensional space, while the frequency scanning in the orthogonal spatial dimension is accomplished by the other sensor. Thus, for a probed object, the imaging plane can be illuminated adequately to obtain the two-dimensional backward scattered fields by the dual-sensor for reconstructing the object. The relativity of beams under different frequencies is very low due to the frequency-scanning beam performance rather than the random beam radiations operated by frequency, and the multi-illuminations with low relativity are very appropriate for multi-mode imaging method with high resolution and anti- noise. Good reconstruction results are given to validate the proposed imaging method.

Thermal energy and charge currents in multi-terminal nanorings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kramer, Tobias; Konrad-Zuse-Zentrum für Informationstechnik Berlin, 14195 Berlin; Kreisbeck, Christoph

2016-06-15

We study in experiment and theory thermal energy and charge transfer close to the quantum limit in a ballistic nanodevice, consisting of multiply connected one-dimensional electron waveguides. The fabricated device is based on an AlGaAs/GaAs heterostructure and is covered by a global top-gate to steer the thermal energy and charge transfer in the presence of a temperature gradient, which is established by a heating current. The estimate of the heat transfer by means of thermal noise measurements shows the device acting as a switch for charge and thermal energy transfer. The wave-packet simulations are based on the multi-terminal Landauer-Büttiker approachmore » and confirm the experimental finding of a mode-dependent redistribution of the thermal energy current, if a scatterer breaks the device symmetry.« less

Three dimensional radiative flow of magnetite-nanofluid with homogeneous-heterogeneous reactions

NASA Astrophysics Data System (ADS)

Hayat, Tasawar; Rashid, Madiha; Alsaedi, Ahmed

2018-03-01

Present communication deals with the effects of homogeneous-heterogeneous reactions in flow of nanofluid by non-linear stretching sheet. Water based nanofluid containing magnetite nanoparticles is considered. Non-linear radiation and non-uniform heat sink/source effects are examined. Non-linear differential systems are computed by Optimal homotopy analysis method (OHAM). Convergent solutions of nonlinear systems are established. The optimal data of auxiliary variables is obtained. Impact of several non-dimensional parameters for velocity components, temperature and concentration fields are examined. Graphs are plotted for analysis of surface drag force and heat transfer rate.

The actinic UV-radiation budget during the ESCOMPTE campaign 2001: results of airborne measurements with the microlight research aircraft D-MIFU

NASA Astrophysics Data System (ADS)

Junkermann, Wolfgang

2005-03-01

During the ESCOMPTE campaign 2001, the vertical distribution of ultraviolet actinic radiation was investigated with concurrent measurements of ozone, aerosol size distributions, and scattering coefficients using a microlight aircraft as airborne platform. Three-dimensional (3D) measurements were performed on a regional scale in the area between Avignon, Aix-en-Provence, and Marseille up to an altitude of 4000 m a.s.l. The results show a pronounced dependence of the vertical actinic flux distribution on aerosol load and stratification while horizontally no significant variability was observed. Furthermore, investigations under cloudy conditions and in the vicinity of cumulus clouds were performed allowing comparisons with one-dimensional and recently published three-dimensional model results. Cloud effects of scattered convective clouds were often found to be masked by aerosols and the aerosol content was generally the dominating factor controlling radiation transfer.

An assessment of some non-gray global radiation models in enclosures

NASA Astrophysics Data System (ADS)

Meulemans, J.

2016-01-01

The accuracy of several non-gray global gas/soot radiation models, namely the Wide-Band Correlated-K (WBCK) model, the Spectral Line Weighted-sum-of-gray-gases model with one optimized gray gas (SLW-1), the (non-gray) Weighted-Sum-of-Gray-Gases (WSGG) model with different sets of coefficients (Smith et al., Soufiani and Djavdan, Taylor and Foster) was assessed on several test cases from the literature. Non-isothermal (or isothermal) participating media containing non-homogeneous (or homogeneous) mixtures of water vapor, carbon dioxide and soot in one-dimensional planar enclosures and multi-dimensional rectangular enclosures were investigated. For all the considered test cases, a benchmark solution (LBL or SNB) was used in order to compute the relative error of each model on the predicted radiative source term and the wall net radiative heat flux.

Near-field thermal radiation of deep- subwavelength slits in the near infrared range.

PubMed

Guo, Yan; Li, Kuanbiao; Xu, Ying; Wei, Kaihua

2017-09-18

We numerically investigate the thermal radiation of one-dimensional deep subwavelength slits in the near infrared range. Using numerical calculations of single-slit and multi-slit structures, we find that high-level radiation efficiency can be achieved for a wide spectrum when ultra-thin intermediate layers are used, and it is less affected by structure parameters. The underlying mechanisms involve Surface Plasmon Polaritons resonance and Fabry-Perot interference at each slit and the interaction between adjacent slits. This structure helps understand and improve the design of thermal radiation control devices.

Radiative transfer simulations of the two-dimensional ocean glint reflectance and determination of the sea surface roughness.

PubMed

Lin, Zhenyi; Li, Wei; Gatebe, Charles; Poudyal, Rajesh; Stamnes, Knut

2016-02-20

An optimized discrete-ordinate radiative transfer model (DISORT3) with a pseudo-two-dimensional bidirectional reflectance distribution function (BRDF) is used to simulate and validate ocean glint reflectances at an infrared wavelength (1036 nm) by matching model results with a complete set of BRDF measurements obtained from the NASA cloud absorption radiometer (CAR) deployed on an aircraft. The surface roughness is then obtained through a retrieval algorithm and is used to extend the simulation into the visible spectral range where diffuse reflectance becomes important. In general, the simulated reflectances and surface roughness information are in good agreement with the measurements, and the diffuse reflectance in the visible, ignored in current glint algorithms, is shown to be important. The successful implementation of this new treatment of ocean glint reflectance and surface roughness in DISORT3 will help improve glint correction algorithms in current and future ocean color remote sensing applications.

Radiative Transfer Simulations of the Two-Dimensional Ocean Glint Reflectance and Determination of the Sea Surface Roughness

NASA Technical Reports Server (NTRS)

Lin, Zhenyi; Li, Wei; Gatebe, Charles; Poudyal, Rajesh; Stamnes, Knut

2016-01-01

An optimized discrete-ordinate radiative transfer model (DISORT3) with a pseudo-two-dimensional bidirectional reflectance distribution function (BRDF) is used to simulate and validate ocean glint reflectances at an infrared wavelength (1036 nm) by matching model results with a complete set of BRDF measurements obtained from the NASA cloud absorption radiometer (CAR) deployed on an aircraft. The surface roughness is then obtained through a retrieval algorithm and is used to extend the simulation into the visible spectral range where diffuse reflectance becomes important. In general, the simulated reflectances and surface roughness information are in good agreement with the measurements, and the diffuse reflectance in the visible, ignored in current glint algorithms, is shown to be important. The successful implementation of this new treatment of ocean glint reflectance and surface roughness in DISORT3 will help improve glint correction algorithms in current and future ocean color remote sensing applications.

Radiative transfer model for aerosols at infrared wavelengths for passive remote sensing applications: revisited.

PubMed

Ben-David, Avishai; Davidson, Charles E; Embury, Janon F

2008-11-01

We introduced a two-dimensional radiative transfer model for aerosols in the thermal infrared [Appl. Opt.45, 6860-6875 (2006)APOPAI0003-693510.1364/AO.45.006860]. In that paper we superimposed two orthogonal plane-parallel layers to compute the radiance due to a two-dimensional (2D) rectangular aerosol cloud. In this paper we revisit the model and correct an error in the interaction of the two layers. We derive new expressions relating to the signal content of the radiance from an aerosol cloud based on the concept of five directional thermal contrasts: four for the 2D diffuse radiance and one for direct radiance along the line of sight. The new expressions give additional insight on the radiative transfer processes within the cloud. Simulations for Bacillus subtilis var. niger (BG) bioaerosol and dustlike kaolin aerosol clouds are compared and contrasted for two geometries: an airborne sensor looking down and a ground-based sensor looking up. Simulation results suggest that aerosol cloud detection from an airborne platform may be more challenging than for a ground-based sensor and that the detection of an aerosol cloud in emission mode (negative direct thermal contrast) is not the same as the detection of an aerosol cloud in absorption mode (positive direct thermal contrast).

K-distribution models for gas mixtures in hypersonic nonequilibrium flows

NASA Astrophysics Data System (ADS)

Bansal, Ankit

Calculation of nonequilibrium radiation field in plasmas around a spacecraft entering into an atmosphere at hypersonic velocities is a very complicated and computationally expensive task. The objective of this Dissertation is to collect state-of-the art spectroscopic data for the evaluation of spectral absorption and emission coefficients of atomic and molecular gases, develop efficient and accurate spectral models and databases, and study the effect of radiation on wall heat loads and flowfield around the spacecraft. The most accurate simulation of radiative transport in the shock layer requires calculating the gas properties at a large number of wavelengths and solving the Radiative Transfer Equation (RTE) in a line-by-line (LBL) fashion, which is prohibitively expensive for coupled simulations. A number of k-distribution based spectral models are developed for atomic lines, continuum and molecular bands that allow efficient evaluation of radiative properties and heat loads in hypersonic shock layer plasma. Molecular radiation poses very different challenges than atomic radiation. A molecular spectrum is governed by simultaneous electronic, vibrational and rotational transitions, making the spectrum very strongly dependent on wavelength. In contrast to an atomic spectrum, where line wings play a major role in heat transfer, most of the heat transfer in molecular spectra occurs near line centers. As the first step, k-distribution models are developed separately for atomic and molecular species, taking advantage of the fact that in the Earth's atmosphere the radiative field is dominated by atomic species (N and O) and in Titan's and Mars' atmospheres molecular bands of CN and CO are dominant. There are a number of practical applications where both atomic and molecular species are present, for example, the vacuum-ultra-violet spectrum during Earth's reentry conditions is marked by emission from atomic bound-bound lines and continuum and simultaneous absorption by strong bands of N2. For such cases, a new model is developed for the treatment of gas mixtures containing atomic lines, continuum and molecular bands. Full-spectrum k-distribution (FSK) method provides very accurate results compared to those obtained from the exact line-by-line method. For cases involving more extreme gradients in species concentrations and temperature, full-spectrum k-distribution model is relatively less accurate, and the method is refined by dividing the spectrum into a number of groups or scales, leading to the development of multi-scale models. The detailed methodology of splitting the gas mixture into scales is presented. To utilize the full potential of the k-distribution methods, pre-calculated values of k-distributions are stored in databases, which can later be interpolated at local flow conditions. Accurate and compact part-spectrum k-distribution databases are developed for atomic species and molecular bands. These databases allow users to calculate desired full-spectrum k-distributions through look-up and interpolation. Application of the new spectral models and databases to shock layer plasma radiation is demonstrated by solving the radiative transfer equation along typical one-dimensional flowfields in Earth's, Titan's and Mars' atmospheres. The k-distribution methods are vastly more efficient than the line-by-line method. The efficiency of the method is compared with the line-by-line method by measuring computational times for a number of test problems, showing typical reduction in computational time by a factor of more than 500 for property evaluation and a factor of about 32,000 for the solution of the RTE. A large percentage of radiative energy emitted in the shock-layer is likely to escape the region, resulting in cooling of the shock layer. This may change the flow parameters in the flowfield and, in turn, can affect radiative as well as convective heat loads. A new flow solver is constructed to simulate coupled hypersonic flow-radiation over a reentry vehicle. The flow solver employs a number of existing schemes and tools available in OpenFOAM; along with a number of additional features for high temperature, compressible and chemically reacting flows, and k-distribution models for radiative calculations. The radiative transport is solved with the one-dimensional tangent slab and P1 solvers, and also with the two-dimensional P1 solver. The new solver is applied to simulate flow around an entry vehicle in Martian atmosphere. Results for uncoupled and coupled flow-radiation simulations are presented, highlighting the effects of radiative cooling on flowfield and wall fluxes.

Analyzing the Signatures of High Red-shift Hydrogen: The Lyman Alpha and 21cm Emission Lines

NASA Astrophysics Data System (ADS)

Hansen, Matthew

Hydrogen line emission is an important window on galaxy formation due to the large abundance of neutral hydrogen in the early Universe. This dissertation comprises two theoretical/computational studies of two types of hydrogen line emission: Lyman alpha emission and escape from young stellar populations, and 21cm radiation from neutral hydrogen clouds at the time of the first luminous objects. The Lyman alpha research concerns the radiative transfer of resonant line radiation from a central source escaping from a multi-phase medium appropriate to young star forming regions. To analyze the properties of this novel radiative transfer problem I develop new theoretical formulations of the problem, substantiated by physically accurate monte carlo simulations of photon scattering and absorption through multi-phase gas geometries. I find that the escape fraction of resonant line photons from young star forming regions--ionized gas filled with neutral hydrogen clouds with low dust content--can exceed the continuum photon escape fraction by up to an order of magnitude. Additionally, I study the effect of gas outflow on the line profile of escaping resonant photons. In light of these results, I discuss why a young normal stellar populations surrounded by a clumpy multi-phase gas outflow can explain the Lyman alpha spectra seen from high red-shift Lyman Alpha Emitters (LAEs). The 21cm research concerns the ionization evolution of the Intergalactic Medium (IGM) during the era of the first luminous objects in the Universe. Large radio-array observatories are currently being built to specifically detect the red-shifted 21cm radiation from neutral hydrogen at red-shifts z ˜ 12 - - 6; the output will be three dimensional maps of ionized regions across the plane of the sky at various red-shift depths. The signal in the resulting ionization maps will be limited by observational noise, mainly from foreground galactic emission in radio frequencies. The research presented here is a unique approach to data mining the planned observational ionization map data. I develop the one-point statistics of the observed 21cm intensity appropriate for the IGM at high red-shifts using a mixture model technique. I show that physically interesting parameters of such mixture models, such as the total ionized gas fraction at a given red-shift slice, can be estimated by applying Maximum Likelihood Expectation to the mixture model of the observed 21cm intensity distribution. The confidence intervals on the expected model parameters are rigorously calculated, and applied to expected detection capabilities of the planned radio-array observatories. I find that at least one of the observatories, the Low Frequency Array (LOFAR), will be able to statistically detect the evolution of the total ionized gas fraction with good precision.

An Investigation of the Compatibility of Radiation and Convection Heat Flux Measurements

NASA Technical Reports Server (NTRS)

Liebert, Curt H.

1996-01-01

A method for determining time-resolved absorbed surface heat flux and surface temperature in radiation and convection environments is described. The method is useful for verification of aerodynamic, heat transfer and durability models. A practical heat flux gage fabrication procedure and a simple one-dimensional inverse heat conduction model and calculation procedure are incorporated in this method. The model provides an estimate of the temperature and heat flux gradient in the direction of heat transfer through the gage. This paper discusses several successful time-resolved tests of this method in hostile convective heating and cooling environments.

Air temperature sensors: dependence of radiative errors on sensor diameter in precision metrology and meteorology

NASA Astrophysics Data System (ADS)

de Podesta, Michael; Bell, Stephanie; Underwood, Robin

2018-04-01

In both meteorological and metrological applications, it is well known that air temperature sensors are susceptible to radiative errors. However, it is not widely known that the radiative error measured by an air temperature sensor in flowing air depends upon the sensor diameter, with smaller sensors reporting values closer to true air temperature. This is not a transient effect related to sensor heat capacity, but a fluid-dynamical effect arising from heat and mass flow in cylindrical geometries. This result has been known historically and is in meteorology text books. However, its significance does not appear to be widely appreciated and, as a consequence, air temperature can be—and probably is being—widely mis-estimated. In this paper, we first review prior descriptions of the ‘sensor size’ effect from the metrological and meteorological literature. We develop a heat transfer model to describe the process for cylindrical sensors, and evaluate the predicted temperature error for a range of sensor sizes and air speeds. We compare these predictions with published predictions and measurements. We report measurements demonstrating this effect in two laboratories at NPL in which the air flow and temperature are exceptionally closely controlled. The results are consistent with the heat-transfer model, and show that the air temperature error is proportional to the square root of the sensor diameter and that, even under good laboratory conditions, it can exceed 0.1 °C for a 6 mm diameter sensor. We then consider the implications of this result. In metrological applications, errors of the order of 0.1 °C are significant, representing limiting uncertainties in dimensional and mass measurements. In meteorological applications, radiative errors can easily be much larger. But in both cases, an understanding of the diameter dependence allows assessment and correction of the radiative error using a multi-sensor technique.

Inverse Faraday effect driven by radiation friction

NASA Astrophysics Data System (ADS)

Liseykina, T. V.; Popruzhenko, S. V.; Macchi, A.

2016-07-01

A collective, macroscopic signature to detect radiation friction in laser-plasma experiments is proposed. In the interaction of superintense circularly polarized laser pulses with high density targets, the effective dissipation due to radiative losses allows the absorption of electromagnetic angular momentum, which in turn leads to the generation of a quasistatic axial magnetic field. This peculiar ‘inverse Faraday effect’ is investigated by analytical modeling and three-dimensional simulations, showing that multi-gigagauss magnetic fields may be generated at laser intensities \\gt {10}23 {{{W}}{{cm}}}-2.

AOI 1— COMPUTATIONAL ENERGY SCIENCES:MULTIPHASE FLOW RESEARCH High-fidelity multi-phase radiation module for modern coal combustion systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Modest, Michael

The effects of radiation in particle-laden flows were the object of the present research. The presence of particles increases optical thickness substantially, making the use of the “optically thin” approximation in most cases a very poor assumption. However, since radiation fluxes peak at intermediate optical thicknesses, overall radiative effects may not necessarily be stronger than in gas combustion. Also, the spectral behavior of particle radiation properties is much more benign, making spectral models simpler (and making the assumption of a gray radiator halfway acceptable, at least for fluidized beds when gas radiation is not large). On the other hand, particlesmore » scatter radiation, making the radiative transfer equation (RTE) much more di fficult to solve. The research carried out in this project encompassed three general areas: (i) assessment of relevant radiation properties of particle clouds encountered in fluidized bed and pulverized coal combustors, (ii) development of proper spectral models for gas–particulate mixtures for various types of two-phase combustion flows, and (iii) development of a Radiative Transfer Equation (RTE) solution module for such applications. The resulting models were validated against artificial cases since open literature experimental data were not available. The final models are in modular form tailored toward maximum portability, and were incorporated into two research codes: (i) the open-source CFD code OpenFOAM, which we have extensively used in our previous work, and (ii) the open-source multi-phase flow code MFIX, which is maintained by NETL.« less

Calculations of thermal radiation transfer of C2H2 and C2H4 together with H2O, CO2, and CO in a one-dimensional enclosure using LBL and SNB models

NASA Astrophysics Data System (ADS)

Qi, Chaobo; Zheng, Shu; Zhou, Huaichun

2017-08-01

Generally, the involvement of hydrocarbons such as C2H4 and its derivative C2H2 in thermal radiation has not been accounted in the numerical simulation of their flames, which may cause serious error for estimation of temperature in the early stage of combustion. At the first, the Statistical Narrow-Band (SNB) model parameters for C2H2 and C2H4 are generated from line by line (LBL) calculations. The distributions of the concentrations of radiating gases such as H2O, CO2, CO, C2H2 and C2H4, and the temperature along the centerline of a laminar ethylene/air diffusion flame were chosen to form a one-dimensional, planar enclosure to be tested in this study. Thermal radiation transfer in such an enclosure was calculated using the LBL approach and the SNB model, most of the relative errors are less than 8% and the results of these two models shows an excellent agreement. Below the height of 20 mm, which is the early stage of the flame, the average fraction contributed by C2H2 and C2H4 in the radiative heat source is 33.8%, while that by CO is only 5.8%. This result indicates that the involvement of C2H2 and C2H4 in radiation heat transfer needs to be taken into account in the numerical modeling of the ethylene/air diffusion flame, especially in the early stage of combustion.

MODTRAN Radiance Modeling of Multi-Angle Worldview-2 Imagery

DTIC Science & Technology

2013-09-01

this thesis, multi-angle CHRIS data has been used to validate canopy BRDF models generated using PROSPECT and SAILH radiative transfer models (D’Urso...67 1. MODTRAN Modeling using BRDF Algorithms .............................67 2. MODTRAN Modeling of Hyperspectral Data...associated with BRDF , and (2) develop software- 2 based atmospheric models , using parameters similar to those found in the imagery, for comparison to

Three-Dimensional Waveguide Arrays for Coupling Between Fiber-Optic Connectors and Surface-Mounted Optoelectronic Devices

NASA Astrophysics Data System (ADS)

Hiramatsu, Seiki; Kinoshita, Masao

2005-09-01

This paper describes the fabrication of novel surface-mountable waveguide connectors and presents test results for them. To ensure more highly integrated and low-cost fabrication, we propose new three-dimensional (3-D) waveguide arrays that feature two-dimensionally integrated optical inputs/outputs and optical path redirection. A wafer-level stack and lamination process was used to fabricate the waveguide arrays. Vertical-cavity surface-emitting lasers (VCSELs) and photodiodes were directly mounted on the arrays and combined with mechanical transferable ferrule using active alignment. With the help of a flip-chip bonder, the waveguide connectors were mounted on a printed circuit board by solder bumps. Using mechanical transferable connectors, which can easily plug into the waveguide connectors, we obtained multi-gigabits-per-second transmission performance.

Constraining physical parameters of ultra-fast outflows in PDS 456 with Monte Carlo simulations

NASA Astrophysics Data System (ADS)

Hagino, K.; Odaka, H.; Done, C.; Gandhi, P.; Takahashi, T.

2014-07-01

Deep absorption lines with extremely high velocity of ˜0.3c observed in PDS 456 spectra strongly indicate the existence of ultra-fast outflows (UFOs). However, the launching and acceleration mechanisms of UFOs are still uncertain. One possible way to solve this is to constrain physical parameters as a function of distance from the source. In order to study the spatial dependence of parameters, it is essential to adopt 3-dimensional Monte Carlo simulations that treat radiation transfer in arbitrary geometry. We have developed a new simulation code of X-ray radiation reprocessed in AGN outflow. Our code implements radiative transfer in 3-dimensional biconical disk wind geometry, based on Monte Carlo simulation framework called MONACO (Watanabe et al. 2006, Odaka et al. 2011). Our simulations reproduce FeXXV and FeXXVI absorption features seen in the spectra. Also, broad Fe emission lines, which reflects the geometry and viewing angle, is successfully reproduced. By comparing the simulated spectra with Suzaku data, we obtained constraints on physical parameters. We discuss launching and acceleration mechanisms of UFOs in PDS 456 based on our analysis.

Monte Carlo Calculations of Polarized Microwave Radiation Emerging from Cloud Structures

NASA Technical Reports Server (NTRS)

Kummerow, Christian; Roberti, Laura

1998-01-01

The last decade has seen tremendous growth in cloud dynamical and microphysical models that are able to simulate storms and storm systems with very high spatial resolution, typically of the order of a few kilometers. The fairly realistic distributions of cloud and hydrometeor properties that these models generate has in turn led to a renewed interest in the three-dimensional microwave radiative transfer modeling needed to understand the effect of cloud and rainfall inhomogeneities upon microwave observations. Monte Carlo methods, and particularly backwards Monte Carlo methods have shown themselves to be very desirable due to the quick convergence of the solutions. Unfortunately, backwards Monte Carlo methods are not well suited to treat polarized radiation. This study reviews the existing Monte Carlo methods and presents a new polarized Monte Carlo radiative transfer code. The code is based on a forward scheme but uses aliasing techniques to keep the computational requirements equivalent to the backwards solution. Radiative transfer computations have been performed using a microphysical-dynamical cloud model and the results are presented together with the algorithm description.

Radiation transfer in plant canopies - Transmission of direct solar radiation and the role of leaf orientation

NASA Technical Reports Server (NTRS)

Verstraete, Michel M.

1987-01-01

Understanding the details of the interaction between the radiation field and plant structures is important climatically because of the influence of vegetation on the surface water and energy balance, but also biologically, since solar radiation provides the energy necessary for photosynthesis. The problem is complex because of the extreme variety of vegetation forms in space and time, as well as within and across plant species. This one-dimensional vertical multilayer model describes the transfer of direct solar radiation through a leaf canopy, accounting explicitly for the vertical inhomogeneities of a plant stand and leaf orientation, as well as heliotropic plant behavior. This model reproduces observational results on homogeneous canopies, but it is also well adapted to describe vertically inhomogeneous canopies. Some of the implications of leaf orientation and plant structure as far as light collection is concerned are briefly reviewed.

Förster resonance energy transfer and protein-induced fluorescence enhancement as synergetic multi-scale molecular rulers

NASA Astrophysics Data System (ADS)

Ploetz, Evelyn; Lerner, Eitan; Husada, Florence; Roelfs, Martin; Chung, Sangyoon; Hohlbein, Johannes; Weiss, Shimon; Cordes, Thorben

2016-09-01

Advanced microscopy methods allow obtaining information on (dynamic) conformational changes in biomolecules via measuring a single molecular distance in the structure. It is, however, extremely challenging to capture the full depth of a three-dimensional biochemical state, binding-related structural changes or conformational cross-talk in multi-protein complexes using one-dimensional assays. In this paper we address this fundamental problem by extending the standard molecular ruler based on Förster resonance energy transfer (FRET) into a two-dimensional assay via its combination with protein-induced fluorescence enhancement (PIFE). We show that donor brightness (via PIFE) and energy transfer efficiency (via FRET) can simultaneously report on e.g., the conformational state of double stranded DNA (dsDNA) following its interaction with unlabelled proteins (BamHI, EcoRV, and T7 DNA polymerase gp5/trx). The PIFE-FRET assay uses established labelling protocols and single molecule fluorescence detection schemes (alternating-laser excitation, ALEX). Besides quantitative studies of PIFE and FRET ruler characteristics, we outline possible applications of ALEX-based PIFE-FRET for single-molecule studies with diffusing and immobilized molecules. Finally, we study transcription initiation and scrunching of E. coli RNA-polymerase with PIFE-FRET and provide direct evidence for the physical presence and vicinity of the polymerase that causes structural changes and scrunching of the transcriptional DNA bubble.

Förster resonance energy transfer and protein-induced fluorescence enhancement as synergetic multi-scale molecular rulers

PubMed Central

Ploetz, Evelyn; Lerner, Eitan; Husada, Florence; Roelfs, Martin; Chung, SangYoon; Hohlbein, Johannes; Weiss, Shimon; Cordes, Thorben

2016-01-01

Advanced microscopy methods allow obtaining information on (dynamic) conformational changes in biomolecules via measuring a single molecular distance in the structure. It is, however, extremely challenging to capture the full depth of a three-dimensional biochemical state, binding-related structural changes or conformational cross-talk in multi-protein complexes using one-dimensional assays. In this paper we address this fundamental problem by extending the standard molecular ruler based on Förster resonance energy transfer (FRET) into a two-dimensional assay via its combination with protein-induced fluorescence enhancement (PIFE). We show that donor brightness (via PIFE) and energy transfer efficiency (via FRET) can simultaneously report on e.g., the conformational state of double stranded DNA (dsDNA) following its interaction with unlabelled proteins (BamHI, EcoRV, and T7 DNA polymerase gp5/trx). The PIFE-FRET assay uses established labelling protocols and single molecule fluorescence detection schemes (alternating-laser excitation, ALEX). Besides quantitative studies of PIFE and FRET ruler characteristics, we outline possible applications of ALEX-based PIFE-FRET for single-molecule studies with diffusing and immobilized molecules. Finally, we study transcription initiation and scrunching of E. coli RNA-polymerase with PIFE-FRET and provide direct evidence for the physical presence and vicinity of the polymerase that causes structural changes and scrunching of the transcriptional DNA bubble. PMID:27641327

Microphysics in Multi-scale Modeling System with Unified Physics

NASA Technical Reports Server (NTRS)

Tao, Wei-Kuo

2012-01-01

Recently, a multi-scale modeling system with unified physics was developed at NASA Goddard. It consists of (1) a cloud-resolving model (Goddard Cumulus Ensemble model, GCE model), (2) a regional scale model (a NASA unified weather research and forecast, WRF), (3) a coupled CRM and global model (Goddard Multi-scale Modeling Framework, MMF), and (4) a land modeling system. The same microphysical processes, long and short wave radiative transfer and land processes and the explicit cloud-radiation, and cloud-land surface interactive processes are applied in this multi-scale modeling system. This modeling system has been coupled with a multi-satellite simulator to use NASA high-resolution satellite data to identify the strengths and weaknesses of cloud and precipitation processes simulated by the model. In this talk, a review of developments and applications of the multi-scale modeling system will be presented. In particular, the microphysics development and its performance for the multi-scale modeling system will be presented.

Development and validation of P-MODTRAN7 and P-MCScene, 1D and 3D polarimetric radiative transfer models

NASA Astrophysics Data System (ADS)

Hawes, Frederick T.; Berk, Alexander; Richtsmeier, Steven C.

2016-05-01

A validated, polarimetric 3-dimensional simulation capability, P-MCScene, is being developed by generalizing Spectral Sciences' Monte Carlo-based synthetic scene simulation model, MCScene, to include calculation of all 4 Stokes components. P-MCScene polarimetric optical databases will be generated by a new version (MODTRAN7) of the government-standard MODTRAN radiative transfer algorithm. The conversion of MODTRAN6 to a polarimetric model is being accomplished by (1) introducing polarimetric data, by (2) vectorizing the MODTRAN radiation calculations and by (3) integrating the newly revised and validated vector discrete ordinate model VDISORT3. Early results, presented here, demonstrate a clear pathway to the long-term goal of fully validated polarimetric models.

Ultrafast High Accuracy PCRTM_SOLAR Model for Cloudy Atmosphere

NASA Technical Reports Server (NTRS)

Yang, Qiguang; Liu, Xu; Wu, Wan; Yang, Ping; Wang, Chenxi

2015-01-01

An ultrafast high accuracy PCRTM_SOLAR model is developed based on PCA compression and principal component-based radiative transfer model (PCRTM). A fast algorithm for simulation of multi-scattering properties of cloud and/or aerosols is integrated into the fast infrared PCRTM. We completed radiance simulation and training for instruments, such as IASI, AIRS, CrIS, NASTI and SHIS, under diverse conditions. The new model is 5 orders faster than 52-stream DISORT with very high accuracy for cloudy sky radiative transfer simulation. It is suitable for hyperspectral remote data assimilation and cloudy sky retrievals.

Bayesian Atmospheric Radiative Transfer (BART): Model, Statistics Driver, and Application to HD 209458b

NASA Astrophysics Data System (ADS)

Cubillos, Patricio; Harrington, Joseph; Blecic, Jasmina; Stemm, Madison M.; Lust, Nate B.; Foster, Andrew S.; Rojo, Patricio M.; Loredo, Thomas J.

2014-11-01

Multi-wavelength secondary-eclipse and transit depths probe the thermo-chemical properties of exoplanets. In recent years, several research groups have developed retrieval codes to analyze the existing data and study the prospects of future facilities. However, the scientific community has limited access to these packages. Here we premiere the open-source Bayesian Atmospheric Radiative Transfer (BART) code. We discuss the key aspects of the radiative-transfer algorithm and the statistical package. The radiation code includes line databases for all HITRAN molecules, high-temperature H2O, TiO, and VO, and includes a preprocessor for adding additional line databases without recompiling the radiation code. Collision-induced absorption lines are available for H2-H2 and H2-He. The parameterized thermal and molecular abundance profiles can be modified arbitrarily without recompilation. The generated spectra are integrated over arbitrary bandpasses for comparison to data. BART's statistical package, Multi-core Markov-chain Monte Carlo (MC3), is a general-purpose MCMC module. MC3 implements the Differental-evolution Markov-chain Monte Carlo algorithm (ter Braak 2006, 2009). MC3 converges 20-400 times faster than the usual Metropolis-Hastings MCMC algorithm, and in addition uses the Message Passing Interface (MPI) to parallelize the MCMC chains. We apply the BART retrieval code to the HD 209458b data set to estimate the planet's temperature profile and molecular abundances. This work was supported by NASA Planetary Atmospheres grant NNX12AI69G and NASA Astrophysics Data Analysis Program grant NNX13AF38G. JB holds a NASA Earth and Space Science Fellowship.

Polarimetric signatures of a coniferous forest canopy based on vector radiative transfer theory

NASA Technical Reports Server (NTRS)

Karam, M. A.; Fung, A. K.; Amar, F.; Mougin, E.; Lopes, A.; Beaudoin, A.

1992-01-01

Complete polarization signatures of a coniferous forest canopy are studied by the iterative solution of the vector radiative transfer equations up to the second order. The forest canopy constituents (leaves, branches, stems, and trunk) are embedded in a multi-layered medium over a rough interface. The branches, stems and trunk scatterers are modeled as finite randomly oriented cylinders. The leaves are modeled as randomly oriented needles. For a plane wave exciting the canopy, the average Mueller matrix is formulated in terms of the iterative solution of the radiative transfer solution and used to determine the linearly polarized backscattering coefficients, the co-polarized and cross-polarized power returns, and the phase difference statistics. Numerical results are presented to investigate the effect of transmitting and receiving antenna configurations on the polarimetric signature of a pine forest. Comparison is made with measurements.

Multi-dimensional effects in radiation pressure acceleration of ions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tripathi, V. K., E-mail: tripathivipin@yahoo.co.in

A laser carries momentum. On reflection from an ultra-thin overdense plasma foil, it deposits recoil momentum on the foil, i.e. exerts radiation pressure on the foil electrons and pushes them to the rear. The space charge field thus created takes the ions along, accelerating the electron-ion double layer as a single unit. When the foil has surface ripple, of wavelength comparable to laser wavelength, the radiation pressure acts non-uniformly on the foil and the perturbation grows as Reyleigh-Taylor (RT) instability as the foil moves. The finite spot size of the laser causes foil to bend. These effects limit the quasi-monomore » energy acceleration of ions. Multi-ion foils, e.g., diamond like carbon foil embedded with protons offer the possibility of suppressing RT instability.« less

Dynamic modeling of temperature change in outdoor operated tubular photobioreactors.

PubMed

Androga, Dominic Deo; Uyar, Basar; Koku, Harun; Eroglu, Inci

2017-07-01

In this study, a one-dimensional transient model was developed to analyze the temperature variation of tubular photobioreactors operated outdoors and the validity of the model was tested by comparing the predictions of the model with the experimental data. The model included the effects of convection and radiative heat exchange on the reactor temperature throughout the day. The temperatures in the reactors increased with increasing solar radiation and air temperatures, and the predicted reactor temperatures corresponded well to the measured experimental values. The heat transferred to the reactor was mainly through radiation: the radiative heat absorbed by the reactor medium, ground radiation, air radiation, and solar (direct and diffuse) radiation, while heat loss was mainly through the heat transfer to the cooling water and forced convection. The amount of heat transferred by reflected radiation and metabolic activities of the bacteria and pump work was negligible. Counter-current cooling was more effective in controlling reactor temperature than co-current cooling. The model developed identifies major heat transfer mechanisms in outdoor operated tubular photobioreactors, and accurately predicts temperature changes in these systems. This is useful in determining cooling duty under transient conditions and scaling up photobioreactors. The photobioreactor design and the thermal modeling were carried out and experimental results obtained for the case study of photofermentative hydrogen production by Rhodobacter capsulatus, but the approach is applicable to photobiological systems that are to be operated under outdoor conditions with significant cooling demands.

Crystallographic effects during radiative melting of semitransparent materials

NASA Astrophysics Data System (ADS)

Webb, B. W.; Viskanta, R.

1987-10-01

Experiments have been performed to illustrate crystallogrpahic effects during radiative melting of unconfined vertical layers of semitransparent material. Radiative melting of a polycrystalline paraffin was performed and the instantaneous layer weight and transmittance were measured using a cantilever beam technique and thermopile radiation detector, respectively. The effects of radiative flux, initial solid subcooling, spectral distribution of the irradiation, and crystal structure of the solid as determined qualitatively by the sample solidification rate were studied. Experimental results show conclusively the dominant influence of cystallographic effects in the form of multiple internal scattering of radiation during the melting process. A theoretical model is formulated to predict the melting rate of the material. Radiation transfer is treated by solving the one-dimensional radiative transfer equation for an absorbing-scattering medium using the discrete ordinates method. Melting rate and global layer reflectance as predicted by the model agree well with experimental data. Parametric studies conducted with the model illustrate the sensitivity of the melting behavior to such variables as incident radiative flux, initial layer opacity (material extinction coefficient), and scattering asymmetry factor.

Thermal ablation therapeutics based on CNx multi-walled nanotubes

PubMed Central

Torti, Suzy V; Byrne, Fiona; Whelan, Orla; Levi, Nicole; Ucer, Burak; Schmid, Michael; Torti, Frank M; Akman, Steven; Liu, Jiwen; Ajayan, Pulickel M; Nalamasu, Omkaram; Carroll, David L

2007-01-01

We demonstrate that nitrogen doped, multi-walled carbon nanotubes (CNx-MWNT) result in photo-ablative destruction of kidney cancer cells when excited by near infrared (NIR) irradiation. Further, we show that effective heat transduction and cellular cytotoxicity depends on nanotube length: effective NIR coupling occurs at nanotube lengths that exceed half the wavelength of the stimulating radiation, as predicted in classical antenna theory. We also demonstrate that this radiation heats the nanotubes through induction processes, resulting in significant heat transfer to surrounding media and cell killing at extraordinarily small radiation doses. This cell death was attributed directly to photothermal effect generated within the culture, since neither the infrared irradiation itself nor the CNx-MWNT were toxic to the cells. PMID:18203437

Engineering of multi-segmented light tunnel and flattop focus with designed axial lengths and gaps

NASA Astrophysics Data System (ADS)

Yu, Yanzhong; Huang, Han; Zhou, Mianmian; Zhan, Qiwen

2018-01-01

Based on the radiation pattern from a sectional-uniform line source antenna, a three-dimensional (3D) focus engineering technique for the creation of multi-segmented light tunnel and flattop focus with designed axial lengths and gaps is proposed. Under a 4Pi focusing system, the fields radiated from sectional-uniform magnetic and electromagnetic current line source antennas are employed to generate multi-segmented optical tube and flattop focus, respectively. Numerical results demonstrate that the produced light tube and flattop focus remain homogeneous along the optical axis; and their lengths of the nth segment and the nth gap between consecutive segments can be easily adjusted and only depend on the sizes of the nth section and the nth blanking between adjacent sectional antennas. The optical tube is a pure azimuthally polarized field but for the flattop focus the longitudinal polarization is dominant on the optical axis. To obtain the required pupil plane illumination for constructing the above focal field with prescribed characteristics, the inverse problem of the antenna radiation field is solved. These peculiar focusing fields might find potential applications in multi-particle acceleration, multi-particle trapping and manipulation.

Multi-year predictability of climate, drought, and wildfire in southwestern North America.

PubMed

Chikamoto, Yoshimitsu; Timmermann, Axel; Widlansky, Matthew J; Balmaseda, Magdalena A; Stott, Lowell

2017-07-26

Past severe droughts over North America have led to massive water shortages and increases in wildfire frequency. Triggering sources for multi-year droughts in this region include randomly occurring atmospheric blocking patterns, ocean impacts on atmospheric circulation, and climate's response to anthropogenic radiative forcings. A combination of these sources translates into a difficulty to predict the onset and length of such droughts on multi-year timescales. Here we present results from a new multi-year dynamical prediction system that exhibits a high degree of skill in forecasting wildfire probabilities and drought for 10-23 and 10-45 months lead time, which extends far beyond the current seasonal prediction activities for southwestern North America. Using a state-of-the-art earth system model along with 3-dimensional ocean data assimilation and by prescribing the external radiative forcings, this system simulates the observed low-frequency variability of precipitation, soil water, and wildfire probabilities in close agreement with observational records and reanalysis data. The underlying source of multi-year predictability can be traced back to variations of the Atlantic/Pacific sea surface temperature gradient, external radiative forcings, and the low-pass filtering characteristics of soils.

Analysis of Aerospike Plume Induced Base-Heating Environment

NASA Technical Reports Server (NTRS)

Wang, Ten-See

1998-01-01

Computational analysis is conducted to study the effect of an aerospike engine plume on X-33 base-heating environment during ascent flight. To properly account for the effect of forebody and aftbody flowfield such as shocks and to allow for potential plume-induced flow-separation, thermo-flowfield of trajectory points is computed. The computational methodology is based on a three-dimensional finite-difference, viscous flow, chemically reacting, pressure-base computational fluid dynamics formulation, and a three-dimensional, finite-volume, spectral-line based weighted-sum-of-gray-gases radiation absorption model computational heat transfer formulation. The predicted convective and radiative base-heat fluxes are presented.

Multi-fluid CFD analysis in Process Engineering

NASA Astrophysics Data System (ADS)

Hjertager, B. H.

2017-12-01

An overview of modelling and simulation of flow processes in gas/particle and gas/liquid systems are presented. Particular emphasis is given to computational fluid dynamics (CFD) models that use the multi-dimensional multi-fluid techniques. Turbulence modelling strategies for gas/particle flows based on the kinetic theory for granular flows are given. Sub models for the interfacial transfer processes and chemical kinetics modelling are presented. Examples are shown for some gas/particle systems including flow and chemical reaction in risers as well as gas/liquid systems including bubble columns and stirred tanks.

Two-dimensional radiative transfer. I - Planar geometry. [in stellar atmospheres

NASA Technical Reports Server (NTRS)

Mihalas, D.; Auer, L. H.; Mihalas, B. R.

1978-01-01

Differential-equation methods for solving the transfer equation in two-dimensional planar geometries are developed. One method, which uses a Hermitian integration formula on ray segments through grid points, proves to be extremely well suited to velocity-dependent problems. An efficient elimination scheme is developed for which the computing time scales linearly with the number of angles and frequencies; problems with large velocity amplitudes can thus be treated accurately. A very accurate and efficient method for performing a formal solution is also presented. A discussion is given of several examples of periodic media and free-standing slabs, both in static cases and with velocity fields. For the free-standing slabs, two-dimensional transport effects are significant near boundaries, but no important effects were found in any of the periodic cases studied.

Numerical developments for short-pulsed Near Infra-Red laser spectroscopy. Part I: direct treatment

NASA Astrophysics Data System (ADS)

Boulanger, Joan; Charette, André

2005-03-01

This two part study is devoted to the numerical treatment of short-pulsed laser near infra-red spectroscopy. The overall goal is to address the possibility of numerical inverse treatment based on a recently developed direct model to solve the transient radiative transfer equation. This model has been constructed in order to incorporate the last improvements in short-pulsed laser interaction with semi-transparent media and combine a discrete ordinates computing of the implicit source term appearing in the radiative transfer equation with an explicit treatment of the transport of the light intensity using advection schemes, a method encountered in reactive flow dynamics. The incident collimated beam is analytically solved through Bouger Beer Lambert extinction law. In this first part, the direct model is extended to fully non-homogeneous materials and tested with two different spatial schemes in order to be adapted to the inversion methods presented in the following second part. As a first point, fundamental methods and schemes used in the direct model are presented. Then, tests are conducted by comparison with numerical simulations given as references. In a third and last part, multi-dimensional extensions of the code are provided. This allows presentation of numerical results of short pulses propagation in 1, 2 and 3D homogeneous and non-homogeneous materials given some parametrical studies on medium properties and pulse shape. For comparison, an integral method adapted to non-homogeneous media irradiated by a pulsed laser beam is also developed for the 3D case.

Current Status on the use of Parallel Computing in Turbulent Reacting Flow Computations Involving Sprays, Monte Carlo PDF and Unstructured Grids. Chapter 4

NASA Technical Reports Server (NTRS)

Raju, M. S.

1998-01-01

The state of the art in multidimensional combustor modeling as evidenced by the level of sophistication employed in terms of modeling and numerical accuracy considerations, is also dictated by the available computer memory and turnaround times afforded by present-day computers. With the aim of advancing the current multi-dimensional computational tools used in the design of advanced technology combustors, a solution procedure is developed that combines the novelty of the coupled CFD/spray/scalar Monte Carlo PDF (Probability Density Function) computations on unstructured grids with the ability to run on parallel architectures. In this approach, the mean gas-phase velocity and turbulence fields are determined from a standard turbulence model, the joint composition of species and enthalpy from the solution of a modeled PDF transport equation, and a Lagrangian-based dilute spray model is used for the liquid-phase representation. The gas-turbine combustor flows are often characterized by a complex interaction between various physical processes associated with the interaction between the liquid and gas phases, droplet vaporization, turbulent mixing, heat release associated with chemical kinetics, radiative heat transfer associated with highly absorbing and radiating species, among others. The rate controlling processes often interact with each other at various disparate time 1 and length scales. In particular, turbulence plays an important role in determining the rates of mass and heat transfer, chemical reactions, and liquid phase evaporation in many practical combustion devices.

Laboratory simulation of interplanetary ultraviolet radiation (broad spectrum) and its effects on Deinococcus radiodurans

NASA Astrophysics Data System (ADS)

Paulino-Lima, Ivan Gláucio; Pilling, Sérgio; Janot-Pacheco, Eduardo; de Brito, Arnaldo Naves; Barbosa, João Alexandre Ribeiro Gonçalves; Leitão, Alvaro Costa; Lage, Claudia de Alencar Santos

2010-08-01

The radiation-resistant bacterium Deinococcus radiodurans was exposed to a simulated interplanetary UV radiation at the Brazilian Synchrotron Light Laboratory (LNLS). Bacterial samples were irradiated on different substrates to investigate the influence of surface relief on cell survival. The effects of cell multi-layers were also investigated. The ratio of viable microorganisms remained virtually the same (average 2%) for integrated doses from 1.2 to 12 kJ m -2, corresponding to 16 h of irradiation at most. The asymptotic profiles of the curves, clearly connected to a shielding effect provided by multi-layering cells on a cavitary substrate (carbon tape), means that the inactivation rate may not change significantly along extended periods of exposure to radiation. Such high survival rates reinforce the possibility of an interplanetary transfer of viable microbes.

Satellite Remote Sensing of Tropical Precipitation and Ice Clouds for GCM Verification

NASA Technical Reports Server (NTRS)

Evans, K. Franklin

2001-01-01

This project, supported by the NASA New Investigator Program, has primarily been funding a graduate student, Darren McKague. Since August 1999 Darren has been working part time at Raytheon, while continuing his PhD research. Darren is planning to finish his thesis work in May 2001, thus some of the work described here is ongoing. The proposed research was to use GOES visible and infrared imager data and SSM/I microwave data to obtain joint distributions of cirrus cloud ice mass and precipitation for a study region in the Eastern Tropical Pacific. These joint distributions of cirrus cloud and rainfall were to be compared to those from the CSU general circulation model to evaluate the cloud microphysical amd cumulus parameterizations in the GCM. Existing algorithms were to be used for the retrieval of cloud ice water path from GOES (Minnis) and rainfall from SSM/I (Wilheit). A theoretical study using radiative transfer models and realistic variations in cloud and precipitation profiles was to be used to estimate the retrieval errors. Due to the unavailability of the GOES satellite cloud retrieval algorithm from Dr. Minnis (a co-PI), there was a change in the approach and emphasis of the project. The new approach was to develop a completely new type of remote sensing algorithm - one to directly retrieve joint probability density functions (pdf's) of cloud properties from multi-dimensional histograms of satellite radiances. The usual approach is to retrieve individual pixels of variables (i.e. cloud optical depth), and then aggregate the information. Only statistical information is actually needed, however, and so a more direct method is desirable. We developed forward radiative transfer models for the SSM/I and GOES channels, originally for testing the retrieval algorithms. The visible and near infrared ice scattering information is obtained from geometric ray tracing of fractal ice crystals (Andreas Macke), while the mid-infrared and microwave scattering is computed with Mie scattering. The radiative transfer is performed with the Spherical Harmonic Discrete Ordinate Method (developed by the PI), and infrared molecular absorption is included with the correlated k-distribution method. The SHDOM radiances have been validated by comparison to version 2 of DISORT (the community "standard" discrete-ordinates radiative transfer model), however we use SHDOM since it is computationally more efficient.

Development, Verification and Validation of Enclosure Radiation Capabilities in the CHarring Ablator Response (CHAR) Code

NASA Technical Reports Server (NTRS)

Salazar, Giovanni; Droba, Justin C.; Oliver, Brandon; Amar, Adam J.

2016-01-01

With the recent development of multi-dimensional thermal protection system (TPS) material response codes including the capabilities to account for radiative heating is a requirement. This paper presents the recent efforts to implement such capabilities in the CHarring Ablator Response (CHAR) code developed at NASA's Johnson Space Center. This work also describes the different numerical methods implemented in the code to compute view factors for radiation problems involving multiple surfaces. Furthermore, verification and validation of the code's radiation capabilities are demonstrated by comparing solutions to analytical results, to other codes, and to radiant test data.

Analysis and design of an ultrahigh temperature hydrogen-fueled MHD generator

NASA Technical Reports Server (NTRS)

Moder, Jeffrey P.; Myrabo, Leik N.; Kaminski, Deborah A.

1993-01-01

A coupled gas dynamics/radiative heat transfer analysis of partially ionized hydrogen, in local thermodynamic equilibrium, flowing through an ultrahigh temperature (10,000-20,000 K) magnetohydrodynamic (MHD) generator is performed. Gas dynamics are modeled by a set of quasi-one-dimensional, nonlinear differential equations which account for friction, convective and radiative heat transfer, and the interaction between the ionized gas and applied magnetic field. Radiative heat transfer is modeled using nongray, absorbing-emitting 2D and 3D P-1 approximations which permit an arbitrary variation of the spectral absorption coefficient with frequency. Gas dynamics and radiative heat transfer are coupled through the energy equation and through the temperature- and density-dependent absorption coefficient. The resulting nonlinear elliptic problem is solved by iterative methods. Design of such MHD generators as onboard, open-cycle, electric power supplies for a particular advanced airbreathing propulsion concept produced an efficient and compact 128-MWe generator characterized by an extraction ratio of 35.5 percent, a power density of 10,500 MWe/cu m, and a specific (extracted) energy of 324 MJe/kg of hydrogen. The maximum wall heat flux and total wall heat load were 453 MW/sq m and 62 MW, respectively.

Investigations of Heat Transfer in Vacuum between Room Temperature and 80 K

NASA Astrophysics Data System (ADS)

Hooks, J.; Demko, J. A.; E Fesmire, J.; Matsumoto, T.

2017-12-01

The heat transfer between room temperature and 80 K is controlled using various insulating material combinations. The modes of heat transfer are well established to be conduction and thermal radiation when in a vacuum. Multi-Layer Insulation (MLI) in a vacuum has long been the best approach. Typically this layered system is applied to the cold surface. This paper investigates the application of MLI to both the cold and warm surface to see whether there is a significant difference. In addition if MLI is on the warm surface, the cold side of the MLI may be below the critical temperature of some high temperature superconducting (HTS) materials. It has been proposed that HTS materials can serve to block thermal radiation. An experiment is conducted to measure this effect. Boil-off calorimetry is the method of measuring the heat transfer.

CFD analysis of a full-scale ceramic kiln module under actual operating conditions

NASA Astrophysics Data System (ADS)

Milani, Massimo; Montorsi, Luca; Stefani, Matteo; Venturelli, Matteo

2017-11-01

The paper focuses on the CFD analysis of a full-scale module of an industrial ceramic kiln under actual operating conditions. The multi-dimensional analysis includes the real geometry of a ceramic kiln module employed in the preheating and firing sections and investigates the heat transfer between the tiles and the burners' flame as well as the many components that comprise the module. Particular attention is devoted to the simulation of the convective flow field in the upper and lower chambers and to the effects of radiation on the different materials is addressed. The assessment of the radiation contribution to the tiles temperature is paramount to the improvement of the performance of the kiln in terms of energy efficiency and fuel consumption. The CFD analysis is combined to a lumped and distributed parameter model of the entire kiln in order to simulate the module behaviour at the boundaries under actual operating conditions. Finally, the CFD simulation is employed to address the effects of the module operating conditions on the tiles' temperature distribution in order to improve the temperature uniformity as well as to enhance the energy efficiency of the system and thus to reduce the fuel consumption.

Modellierung dreidimensionaler Strahlungsfelder im frühen Universum %t Modelling three dimensional radiation fields in the early universe

NASA Astrophysics Data System (ADS)

Meinköhn, Erik

2002-11-01

The present work aims at the modelling of three-dimensional radiation fields in gas clouds from the early universe, in particular as to the influence of varying distributions of density and velocity. In observations of high-redshift gas clouds, the Lyα transition from the first excited energy level to the ground state of the hydrogen atom is usually found to be the only prominent emission lines in the entire spectrum. It is a well-known assumption that high-redshifted hydrogen clouds are the precursors of present-day galaxies. Thus, the investigation of the Lyα line is of paramount importance of the theory of galaxy formation and evolution. The observed Lyα line - or rather, to be precise, its profile - reveals both the complexity of the spatial distribution and of the kinematics of the interstellar gas, and also the nature of the photon source. In this thesis we have developed a code which is capable of solving the three-dimensional frequency-dependent radiative transfer equation for arbitrarily nonrelativistically moving media. The numerical treatment of the associated partial integro-differential equation is an extremely challenging task, since radiation intensity depends on 6 variables, namely 3 space variables, 2 variables describing the direction of photon propagation, and the frequency. With the goal of a quantitative comparison with observational data in mind, the implementation of very efficient methods for a sufficiently accurate solution of the complex radiative transfer problems turned out to be a necessity. The size of the resulting linear system of equations makes the use of parallelization techniques and grid refinement strategies indispensable.

All-optical photochromic spatial light modulators based on photoinduced electron transfer in rigid matrices

NASA Technical Reports Server (NTRS)

Beratan, David N. (Inventor); Perry, Joseph W. (Inventor)

1991-01-01

A single material (not a multi-element structure) spatial light modulator may be written to, as well as read out from, using light. The device has tailorable rise and hold times dependent on the composition and concentration of the molecular species used as the active components. The spatial resolution of this device is limited only by light diffraction as in volume holograms. The device may function as a two-dimensional mask (transmission or reflection) or as a three-dimensional volume holographic medium. This device, based on optically-induced electron transfer, is able to perform incoherent to coherent image conversion or wavelength conversion over a wide spectral range (ultraviolet, visible, or near-infrared regions).

Comparing simulations and test data of a radiation damaged CCD for the Euclid mission

NASA Astrophysics Data System (ADS)

Skottfelt, Jesper; Hall, David; Gow, Jason; Murray, Neil; Holland, Andrew; Prod'homme, Thibaut

2016-07-01

The radiation damage effects from the harsh radiative environment outside the Earth's atmosphere can be a cause for concern for most space missions. With the science goals becoming ever more demanding, the requirements on the precision of the instruments on board these missions also increases, and it is therefore important to investigate how the radiation induced damage affects the Charge-Coupled Devices (CCDs) that most of these instruments rely on. The primary goal of the Euclid mission is to study the nature of dark matter and dark energy using weak lensing and baryonic acoustic oscillation techniques. The weak lensing technique depends on very precise shape measurements of distant galaxies obtained by a large CCD array. It is anticipated that over the 6 year nominal lifetime of mission, the CCDs will be degraded to an extent that these measurements will not be possible unless the radiation damage effects are corrected. We have therefore created a Monte Carlo model that simulates the physical processes taking place when transferring signal through a radiation damaged CCD. The software is based on Shockley-Read-Hall theory, and is made to mimic the physical properties in the CCD as close as possible. The code runs on a single electrode level and takes charge cloud size and density, three dimensional trap position, and multi-level clocking into account. A key element of the model is that it takes device specific simulations of electron density as a direct input, thereby avoiding to make any analytical assumptions about the size and density of the charge cloud. This paper illustrates how test data and simulated data can be compared in order to further our understanding of the positions and properties of the individual radiation-induced traps.

Robust Radar Emitter Recognition Based on the Three-Dimensional Distribution Feature and Transfer Learning

PubMed Central

Yang, Zhutian; Qiu, Wei; Sun, Hongjian; Nallanathan, Arumugam

2016-01-01

Due to the increasing complexity of electromagnetic signals, there exists a significant challenge for radar emitter signal recognition. To address this challenge, multi-component radar emitter recognition under a complicated noise environment is studied in this paper. A novel radar emitter recognition approach based on the three-dimensional distribution feature and transfer learning is proposed. The cubic feature for the time-frequency-energy distribution is proposed to describe the intra-pulse modulation information of radar emitters. Furthermore, the feature is reconstructed by using transfer learning in order to obtain the robust feature against signal noise rate (SNR) variation. Last, but not the least, the relevance vector machine is used to classify radar emitter signals. Simulations demonstrate that the approach proposed in this paper has better performances in accuracy and robustness than existing approaches. PMID:26927111

Robust Radar Emitter Recognition Based on the Three-Dimensional Distribution Feature and Transfer Learning.

PubMed

Yang, Zhutian; Qiu, Wei; Sun, Hongjian; Nallanathan, Arumugam

2016-02-25

Due to the increasing complexity of electromagnetic signals, there exists a significant challenge for radar emitter signal recognition. To address this challenge, multi-component radar emitter recognition under a complicated noise environment is studied in this paper. A novel radar emitter recognition approach based on the three-dimensional distribution feature and transfer learning is proposed. The cubic feature for the time-frequency-energy distribution is proposed to describe the intra-pulse modulation information of radar emitters. Furthermore, the feature is reconstructed by using transfer learning in order to obtain the robust feature against signal noise rate (SNR) variation. Last, but not the least, the relevance vector machine is used to classify radar emitter signals. Simulations demonstrate that the approach proposed in this paper has better performances in accuracy and robustness than existing approaches.

Radiative transfer of X-rays in the solar corona

NASA Technical Reports Server (NTRS)

Acton, L. W.

1978-01-01

The problem of resonance scattering of X-ray emission lines in the solar corona is investigated. For the resonance lines of some helium-like ions, significant optical depths are reached over distances small compared with the size of typical coronal features. A general integral equation for the transfer of resonance-line radiation under solar coronal conditions is derived. This expression is in a form useful for modeling the complex three-dimensional temperature and density structure of coronal active regions. The transfer equation is then cast in a form illustrating the terms which give rise to the attenuation or enhancement of the resonance-line intensity. The source function for helium-like oxygen (O VII) under coronal conditions is computed and discussed in terms of the relative importance of scattering.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khan, Masood; Malik, Rabia, E-mail: rabiamalik.qau@gmail.com; Department of Mathematics and Statistics, International Islamic University Islamabad 44000

In the present paper, we endeavor to perform a numerical analysis in connection with the nonlinear radiative stagnation-point flow and heat transfer to Sisko fluid past a stretching cylinder in the presence of convective boundary conditions. The influence of thermal radiation using nonlinear Rosseland approximation is explored. The numerical solutions of transformed governing equations are calculated through forth order Runge-Kutta method using shooting technique. With the help of graphs and tables, the influence of non-dimensional parameters on velocity and temperature along with the local skin friction and Nusselt number is discussed. The results reveal that the temperature increases however, heatmore » transfer from the surface of cylinder decreases with the increasing values of thermal radiation and temperature ratio parameters. Moreover, the authenticity of numerical solutions is validated by finding their good agreement with the HAM solutions.« less

AirMSPI Data and Information

Atmospheric Science Data Center

2018-05-09

AirMSPI Data and Information   Airborne Multi-angle Spectro Polarimetric ... where 3-D radiative transfer may dominate, and (b) enable retrieval of aerosol and cloud macrophysical properties (distribution, height), ... MISR Home Page DISCOVER-AQ Information AirMSPI Announcements MISR Data Table ...

Four-component numerical simulation model of radiative convective interactions in large-scale oxygen-hydrogen turbulent fire balls

DOE Office of Scientific and Technical Information (OSTI.GOV)

Surzhikov, S.T.

1996-12-31

Two-dimensional radiative gas dynamics model for numerical simulation of oxygen-hydrogen fire ball which may be generated by an explosion of a launch vehicle with cryogenic (LO{sub 2}-LH{sub 2}) fuel components is presented. The following physical-chemical processes are taken into account in the numerical model: and effective chemical reaction between the gaseous components (O{sub 2}-H{sub 2}) of the propellant, turbulent mixing and diffusion of the components, and radiative heat transfer. The results of numerical investigations of the following problems are presented: The influence of radiative heat transfer on fire ball gas dynamics during the first 13 sec after explosion, the effectmore » of the fuel gaseous components afterburning on fire ball gas dynamics, and the effect of turbulence on fire ball gas dynamics (in a framework of algebraic model of turbulent mixing).« less

A simplified analytical solution for thermal response of a one-dimensional, steady state transpiration cooling system in radiative and convective environment

NASA Technical Reports Server (NTRS)

Kubota, H.

1976-01-01

A simplified analytical method for calculation of thermal response within a transpiration-cooled porous heat shield material in an intense radiative-convective heating environment is presented. The essential assumptions of the radiative and convective transfer processes in the heat shield matrix are the two-temperature approximation and the specified radiative-convective heatings of the front surface. Sample calculations for porous silica with CO2 injection are presented for some typical parameters of mass injection rate, porosity, and material thickness. The effect of these parameters on the cooling system is discussed.

A High-Order Transport Scheme for Collisional-Radiative and Nonequilibrium Plasma

DTIC Science & Technology

2009-02-06

of change of the temperature is obtained, ∂E ∂T ∂T ∂t = ∂ ∂x ( κs ∂T ∂x ) (7.6) Assuming a one- dimensional discretization on a uniformly- spaced ...oscillations nor a quantitative analysis of the multi- dimensional shock structure has been provided to date. This dissertation builds upon previous...high-enthalpy nonequilibrium plasmas and is the focus of much of this work. The plasma is described as

Multi-Group Reductions of LTE Air Plasma Radiative Transfer in Cylindrical Geometries

NASA Technical Reports Server (NTRS)

Scoggins, James; Magin, Thierry Edouard Bertran; Wray, Alan; Mansour, Nagi N.

2013-01-01

Air plasma radiation in Local Thermodynamic Equilibrium (LTE) within cylindrical geometries is studied with an application towards modeling the radiative transfer inside arc-constrictors, a central component of constricted-arc arc jets. A detailed database of spectral absorption coefficients for LTE air is formulated using the NEQAIR code developed at NASA Ames Research Center. The database stores calculated absorption coefficients for 1,051,755 wavelengths between 0.04 µm and 200 µm over a wide temperature (500K to 15 000K) and pressure (0.1 atm to 10.0 atm) range. The multi-group method for spectral reduction is studied by generating a range of reductions including pure binning and banding reductions from the detailed absorption coefficient database. The accuracy of each reduction is compared to line-by-line calculations for cylindrical temperature profiles resembling typical profiles found in arc-constrictors. It is found that a reduction of only 1000 groups is sufficient to accurately model the LTE air radiation over a large temperature and pressure range. In addition to the reduction comparison, the cylindrical-slab formulation is compared with the finite-volume method for the numerical integration of the radiative flux inside cylinders with varying length. It is determined that cylindrical-slabs can be used to accurately model most arc-constrictors due to their high length to radius ratios.

Radiated flow of chemically reacting nanoliquid with an induced magnetic field across a permeable vertical plate

NASA Astrophysics Data System (ADS)

Mahanthesh, B.; Gireesha, B. J.; Athira, P. R.

Impact of induced magnetic field over a flat porous plate by utilizing incompressible water-copper nanoliquid is examined analytically. Flow is supposed to be laminar, steady and two-dimensional. The plate is subjected to a regular free stream velocity as well as suction velocity. Flow formulation is developed by considering Maxwell-Garnetts (MG) and Brinkman models of nanoliquid. Impacts of thermal radiation, viscous dissipation, temperature dependent heat source/sink and first order chemical reaction are also retained. The subjected non-linear problems are non-dimensionalized and analytic solutions are presented via series expansion method. The graphs are plotted to analyze the influence of pertinent parameters on flow, magnetism, heat and mass transfer fields as well as friction factor, current density, Nusselt and Sherwood numbers. It is found that friction factor at the plate is more for larger magnetic Prandtl number. Also the rate of heat transfer decayed with increasing nanoparticles volume fraction and the strength of magnetism.

Radiant heat exchange calculations in radiantly heated and cooled enclosures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chapman, K.S.; Zhang, P.

1995-08-01

This paper presents the development of a three-dimensional mathematical model to compute the radiant heat exchange between surfaces separated by a transparent and/or opaque medium. The model formulation accommodates arbitrary arrangements of the interior surfaces, as well as arbitrary placement of obstacles within the enclosure. The discrete ordinates radiation model is applied and has the capability to analyze the effect of irregular geometries and diverse surface temperatures and radiative properties. The model is verified by comparing calculated heat transfer rates to heat transfer rates determined from the exact radiosity method for four different enclosures. The four enclosures were selected tomore » provide a wide range of verification. This three-dimensional model based on the discrete ordinates method can be applied to a building to assist the design engineer in sizing a radiant heating system. By coupling this model with a convective and conductive heat transfer model and a thermal comfort model, the comfort levels throughout the room can be easily and efficiently mapped for a given radiant heater location. In addition, objects such as airplanes, trucks, furniture, and partitions can be easily incorporated to determine their effect on the performance of the radiant heating system.« less

Multi-Resolution Rapid Prototyping of Vehicle Cooling Systems: Approach and Test Results

DTIC Science & Technology

2014-08-01

where the A/C was working. Figure 21: Comparison model/experiment for condenser refrigerant power; heat transfer factor = 0.8 The figure...previously. To demonstrate stable interactions with a more realistic environment, we have connected the four heat exchangers (two radiators, condenser ...simulations of any vehicle (or other) cooling systems. It can be seen that the underHood heat exchangers (transaxle radiator, condenser and ICE

Quantum free energy landscapes from ab initio path integral metadynamics: Double proton transfer in the formic acid dimer is concerted but not correlated.

PubMed

Ivanov, Sergei D; Grant, Ian M; Marx, Dominik

2015-09-28

With the goal of computing quantum free energy landscapes of reactive (bio)chemical systems in multi-dimensional space, we combine the metadynamics technique for sampling potential energy surfaces with the ab initio path integral approach to treating nuclear quantum motion. This unified method is applied to the double proton transfer process in the formic acid dimer (FAD), in order to study the nuclear quantum effects at finite temperatures without imposing a one-dimensional reaction coordinate or reducing the dimensionality. Importantly, the ab initio path integral metadynamics technique allows one to treat the hydrogen bonds and concomitant proton transfers in FAD strictly independently and thus provides direct access to the much discussed issue of whether the double proton transfer proceeds via a stepwise or concerted mechanism. The quantum free energy landscape we compute for this H-bonded molecular complex reveals that the two protons move in a concerted fashion from initial to product state, yet world-line analysis of the quantum correlations demonstrates that the protons are as quantum-uncorrelated at the transition state as they are when close to the equilibrium structure.

A Herschel resolved debris disc around HD 105211

NASA Astrophysics Data System (ADS)

Hengst, S.; Marshall, J. P.; Horner, J.; Marsden, S. C.

2017-07-01

Debris discs are the dusty aftermath of planet formation processes around main-sequence stars. Analysis of these discs is often hampered by the absence of any meaningful constraint on the location and spatial extent of the disc around its host star. Multi-wavelength, resolved imaging ameliorates the degeneracies inherent in the modelling process, making such data indispensable in the interpretation of these systems. The Herschel Space Observatory observed HD 105211 (η Cru, HIP 59072) with its Photodetector Array Camera and Spectrometer (PACS) instrument in three far-infrared wavebands (70, 100 and 160 μm). Here we combine these data with ancillary photometry spanning optical to far-infrared wavelengths in order to determine the extent of the circumstellar disc. The spectral energy distribution and multi-wavelength resolved emission of the disc are simultaneously modelled using a radiative transfer and imaging codes. Analysis of the Herschel/PACS images reveals the presence of extended structure in all three PACS images. From a radiative transfer model we derive a disc extent of 87.0 ± 2.5 au, with an inclination of 70.7 ± 2.2° to the line of sight and a position angle of 30.1 ± 0.5°. Deconvolution of the Herschel images reveals a potential asymmetry but this remains uncertain as a combined radiative transfer and image analysis replicates both the structure and the emission of the disc using a single axisymmetric annulus.

Exoplanet Atmospheres: From Light-Curve Analyses to Radiative-Transfer Modeling

NASA Astrophysics Data System (ADS)

Cubillos, Patricio; Harrington, Joseph; Blecic, Jasmina; Rojo, Patricio; Stemm, Madison; Lust, Nathaniel B.; Foster, Andrew S.; Loredo, Thomas J.

2015-01-01

Multi-wavelength transit and secondary-eclipse light-curve observations are some of the most powerful techniques to probe the thermo-chemical properties of exoplanets. Although the small planet-to-star constrast ratios demand a meticulous data analysis, and the limited available spectral bands can further restrain constraints, a Bayesian approach can robustly reveal what constraints can we set, given the data.We review the main aspects considered during the analysis of Spitzer time-series data by our group with an aplication to WASP-8b and TrES-1. We discuss the applicability and limitations of the most commonly used correlated-noise estimators. We describe our open-source Bayesian Atmospheric Radiative Transfer (BART) code. BART calculates the planetary emission or transmission spectrum by solving a 1D line-by-line radiative-transfer equation. The generated spectra are integrated over determined bandpasses for comparison to the data. Coupled to our Multi-core Markov-chain Monte Carlo (MC3) statistical package, BART constrains the temperature profile and chemical abundances in the planet's atmosphere. We apply the BART retrieval code to the HD 209458b data set to estimate the planet's temperature profile and molecular abundances.This work was supported by NASA Planetary Atmospheres grant NNX12AI69G and NASA Astrophysics Data Analysis Program grant NNX13AF38G. JB holds a NASA Earth and Space Science Fellowship.

Monitoring dynamic reactions of red blood cells to UHF electromagnetic waves radiation using a novel micro-imaging technology.

PubMed

Ruan, Ping; Yong, Junguang; Shen, Hongtao; Zheng, Xianrong

2012-12-01

Multiple state-of-the-art techniques, such as multi-dimensional micro-imaging, fast multi-channel micro-spetrophotometry, and dynamic micro-imaging analysis, were used to dynamically investigate various effects of cell under the 900 MHz electromagnetic radiation. Cell changes in shape, size, and parameters of Hb absorption spectrum under different power density electromagnetic waves radiation were presented in this article. Experimental results indicated that the isolated human red blood cells (RBCs) do not have obviously real-time responses to the ultra-low density (15 μW/cm(2), 31 μW/cm(2)) electromagnetic wave radiation when the radiation time is not more than 30 min; however, the cells do have significant reactions in shape, size, and the like, to the electromagnetic waves radiation with power densities of 1 mW/cm(2) and 5 mW/cm(2). The data also reveal the possible influences and statistical relationships among living human cell functions, radiation amount, and exposure time with high-frequency electromagnetic waves. The results of this study may be significant on protection of human being and other living organisms against possible radiation affections of the high-frequency electromagnetic waves.

Three-dimensional nonsteady heat-transfer analysis of an indirect heating furnace

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ito, H.; Umeda, Y.; Nakamura, Y.

1991-01-01

This paper reports on an accurate design method for industrial furnaces from the viewpoint of heat transfer. The authors carried out a three-dimensional nonsteady heat-transfer analysis for a practical-size heat- treatment furnace equipped with radiant heaters. The authors applied three software package programs, STREAM, MORSE, and TRUMP, for the analysis of the combined heat-transfer problems of radiation, conduction, and convection. The authors also carried out experiments of the heating of a charge consisting of packed bolts. The authors found that the air swirled inside the furnace. As for the temperature in each part in the furnace, analytical results were generallymore » in close agreement with the experimental ones. This suggests that our analytical method is useful for a fundamental heat- transfer-based design of a practical-size industrial furnace with an actual charge such as packed bolts. As for the temperature distribution inside the bolt charge (work), the analytical results were also in close agreement with the experimental ones. Consequently, it was found that the heat transfer in the bolt charge could be described with an effective thermal conductivity.« less

A WENO-Limited, ADER-DT, Finite-Volume Scheme for Efficient, Robust, and Communication-Avoiding Multi-Dimensional Transport

DOE Office of Scientific and Technical Information (OSTI.GOV)

Norman, Matthew R

2014-01-01

The novel ADER-DT time discretization is applied to two-dimensional transport in a quadrature-free, WENO- and FCT-limited, Finite-Volume context. Emphasis is placed on (1) the serial and parallel computational properties of ADER-DT and this framework and (2) the flexibility of ADER-DT and this framework in efficiently balancing accuracy with other constraints important to transport applications. This study demonstrates a range of choices for the user when approaching their specific application while maintaining good parallel properties. In this method, genuine multi-dimensionality, single-step and single-stage time stepping, strict positivity, and a flexible range of limiting are all achieved with only one parallel synchronizationmore » and data exchange per time step. In terms of parallel data transfers per simulated time interval, this improves upon multi-stage time stepping and post-hoc filtering techniques such as hyperdiffusion. This method is evaluated with standard transport test cases over a range of limiting options to demonstrate quantitatively and qualitatively what a user should expect when employing this method in their application.« less

Cloud Forecasting and 3-D Radiative Transfer Model Validation using Citizen-Sourced Imagery

NASA Astrophysics Data System (ADS)

Gasiewski, A. J.; Heymsfield, A.; Newman Frey, K.; Davis, R.; Rapp, J.; Bansemer, A.; Coon, T.; Folsom, R.; Pfeufer, N.; Kalloor, J.

2017-12-01

Cloud radiative feedback mechanisms are one of the largest sources of uncertainty in global climate models. Variations in local 3D cloud structure impact the interpretation of NASA CERES and MODIS data for top-of-atmosphere radiation studies over clouds. Much of this uncertainty results from lack of knowledge of cloud vertical and horizontal structure. Surface-based data on 3-D cloud structure from a multi-sensor array of low-latency ground-based cameras can be used to intercompare radiative transfer models based on MODIS and other satellite data with CERES data to improve the 3-D cloud parameterizations. Closely related, forecasting of solar insolation and associated cloud cover on time scales out to 1 hour and with spatial resolution of 100 meters is valuable for stabilizing power grids with high solar photovoltaic penetrations. Data for cloud-advection based solar insolation forecasting with requisite spatial resolution and latency needed to predict high ramp rate events obtained from a bottom-up perspective is strongly correlated with cloud-induced fluctuations. The development of grid management practices for improved integration of renewable solar energy thus also benefits from a multi-sensor camera array. The data needs for both 3D cloud radiation modelling and solar forecasting are being addressed using a network of low-cost upward-looking visible light CCD sky cameras positioned at 2 km spacing over an area of 30-60 km in size acquiring imagery on 30 second intervals. Such cameras can be manufactured in quantity and deployed by citizen volunteers at a marginal cost of 200-400 and operated unattended using existing communications infrastructure. A trial phase to understand the potential utility of up-looking multi-sensor visible imagery is underway within this NASA Citizen Science project. To develop the initial data sets necessary to optimally design a multi-sensor cloud camera array a team of 100 citizen scientists using self-owned PDA cameras is being organized to collect distributed cloud data sets suitable for MODIS-CERES cloud radiation science and solar forecasting algorithm development. A low-cost and robust sensor design suitable for large scale fabrication and long term deployment has been developed during the project prototyping phase.

Accuracy analysis of automodel solutions for Lévy flight-based transport: from resonance radiative transfer to a simple general model

NASA Astrophysics Data System (ADS)

Kukushkin, A. B.; Sdvizhenskii, P. A.

2017-12-01

The results of accuracy analysis of automodel solutions for Lévy flight-based transport on a uniform background are presented. These approximate solutions have been obtained for Green’s function of the following equations: the non-stationary Biberman-Holstein equation for three-dimensional (3D) radiative transfer in plasma and gases, for various (Doppler, Lorentz, Voigt and Holtsmark) spectral line shapes, and the 1D transport equation with a simple longtailed step-length probability distribution function with various power-law exponents. The results suggest the possibility of substantial extension of the developed method of automodel solution to other fields far beyond physics.

Investigation of Lithium Metal Hydride Materials for Mitigation of Deep Space Radiation

NASA Technical Reports Server (NTRS)

Rojdev, Kristina; Atwell, William

2016-01-01

Radiation exposure to crew, electronics, and non-metallic materials is one of many concerns with long-term, deep space travel. Mitigating this exposure is approached via a multi-faceted methodology focusing on multi-functional materials, vehicle configuration, and operational or mission constraints. In this set of research, we are focusing on new multi-functional materials that may have advantages over traditional shielding materials, such as polyethylene. Metal hydride materials are of particular interest for deep space radiation shielding due to their ability to store hydrogen, a low-Z material known to be an excellent radiation mitigator and a potential fuel source. We have previously investigated 41 different metal hydrides for their radiation mitigation potential. Of these metal hydrides, we found a set of lithium hydrides to be of particular interest due to their excellent shielding of galactic cosmic radiation. Given these results, we will continue our investigation of lithium hydrides by expanding our data set to include dose equivalent and to further understand why these materials outperformed polyethylene in a heavy ion environment. For this study, we used HZETRN 2010, a one-dimensional transport code developed by NASA Langley Research Center, to simulate radiation transport through the lithium hydrides. We focused on the 1977 solar minimum Galactic Cosmic Radiation environment and thicknesses of 1, 5, 10, 20, 30, 50, and 100 g/cm2 to stay consistent with our previous studies. The details of this work and the subsequent results will be discussed in this paper.

Top-of-Atmosphere Albedo Estimation from POLDER Multi-Angle Measurements: Evaluation of Water and Ice Cloud Radiative Transfer Models

NASA Technical Reports Server (NTRS)

Loeb, Norman G.

2005-01-01

This final grant report lists accomplishments from the reporting period, and includes citations and abstracts for published or submitted papers produced under the grant in which a co-investigator is the lead author.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ivanov, Sergei D., E-mail: sergei.ivanov@unirostock.de; Grant, Ian M.; Marx, Dominik

With the goal of computing quantum free energy landscapes of reactive (bio)chemical systems in multi-dimensional space, we combine the metadynamics technique for sampling potential energy surfaces with the ab initio path integral approach to treating nuclear quantum motion. This unified method is applied to the double proton transfer process in the formic acid dimer (FAD), in order to study the nuclear quantum effects at finite temperatures without imposing a one-dimensional reaction coordinate or reducing the dimensionality. Importantly, the ab initio path integral metadynamics technique allows one to treat the hydrogen bonds and concomitant proton transfers in FAD strictly independently andmore » thus provides direct access to the much discussed issue of whether the double proton transfer proceeds via a stepwise or concerted mechanism. The quantum free energy landscape we compute for this H-bonded molecular complex reveals that the two protons move in a concerted fashion from initial to product state, yet world-line analysis of the quantum correlations demonstrates that the protons are as quantum-uncorrelated at the transition state as they are when close to the equilibrium structure.« less

Direct-to-diffuse UV Solar Irradiance Ratio for a UV rotating Shadowband Spectroradiometer and a UV Multi-filter Rotating Shadowband Radiometer

NASA Astrophysics Data System (ADS)

Lantz, K.; Kiedron, P.; Petropavlovskikh, I.; Michalsky, J.; Slusser, J.

2008-12-01

. Two spectroradiometers reside that measure direct and diffuse UV solar irradiance are located at the Table Mountain Test Facility, 8 km north of Boulder, CO. The UV- Rotating Shadowband Spectrograph (UV-RSS) measures diffuse and direct solar irradiance from 290 - 400 nm. The UV Multi-Filter Rotating Shadowband Radiometer (UV-MFRSR) measures diffuse and direct solar irradiance in seven 2-nm wide bands, i.e. 300, 305, 311, 317, 325, and 368 nm. The purpose of the work is to compare radiative transfer model calculations (TUV) with the results from the UV-Rotating Shadowband Spectroradiometer (UV-RSS) and the UV-MFRSR to estimate direct-to-diffuse solar irradiance ratios (DDR) that are used to evaluate the possibility of retrieving aerosol single scattering albedo (SSA) under a variety of atmospheric conditions: large and small aerosol loading, large and small surface albedo. For the radiative transfer calculations, total ozone measurements are obtained from a collocated Brewer spectrophotometer.

Investigation of the shape transferability of nanoscale multi-tip diamond tools in the diamond turning of nanostructures

NASA Astrophysics Data System (ADS)

Luo, Xichun; Tong, Zhen; Liang, Yingchun

2014-12-01

In this article, the shape transferability of using nanoscale multi-tip diamond tools in the diamond turning for scale-up manufacturing of nanostructures has been demonstrated. Atomistic multi-tip diamond tool models were built with different tool geometries in terms of the difference in the tip cross-sectional shape, tip angle, and the feature of tool tip configuration, to determine their effect on the applied forces and the machined nano-groove geometries. The quality of machined nanostructures was characterized by the thickness of the deformed layers and the dimensional accuracy achieved. Simulation results show that diamond turning using nanoscale multi-tip tools offers tremendous shape transferability in machining nanostructures. Both periodic and non-periodic nano-grooves with different cross-sectional shapes can be successfully fabricated using the multi-tip tools. A hypothesis of minimum designed ratio of tool tip distance to tip base width (L/Wf) of the nanoscale multi-tip diamond tool for the high precision machining of nanostructures was proposed based on the analytical study of the quality of the nanostructures fabricated using different types of the multi-tip tools. Nanometric cutting trials using nanoscale multi-tip diamond tools (different in L/Wf) fabricated by focused ion beam (FIB) were then conducted to verify the hypothesis. The investigations done in this work imply the potential of using the nanoscale multi-tip diamond tool for the deterministic fabrication of period and non-periodic nanostructures, which opens up the feasibility of using the process as a versatile manufacturing technique in nanotechnology.

Microwave radiative transfer studies of precipitation

NASA Technical Reports Server (NTRS)

Bringi, V. N.; Vivekanandan, J.; Turk, F. Joseph

1993-01-01

Since the deployment of the DMSP SSM/I microwave imagers in 1987, increased utilization of passive microwave radiometry throughout the 10 - 100 GHz spectrum has occurred for measurement of atmospheric constituents and terrestrial surfaces. Our efforts have focused on observations and analysis of the microwave radiative transfer behavior of precipitating clouds. We have focused particular attention on combining both aircraft and SSM/I radiometer imagery with ground-based multiparameter radar observations. As part of this and the past NASA contract, we have developed a multi-stream, polarized radiative transfer model which incorporates scattering. The model has the capability to be initialized with cloud model output or multiparameter radar products. This model provides the necessary 'link' between the passive microwave radiometer and active microwave radar observations. This unique arrangement has allowed the brightness temperatures (TB) to be compared against quantities such as rainfall, liquid/ice water paths, and the vertical structure of the cloud. Quantification of the amounts of ice and water in precipitating clouds is required for understanding of the global energy balance.

Model reduction of nonsquare linear MIMO systems using multipoint matrix continued-fraction expansions

NASA Technical Reports Server (NTRS)

Guo, Tong-Yi; Hwang, Chyi; Shieh, Leang-San

1994-01-01

This paper deals with the multipoint Cauer matrix continued-fraction expansion (MCFE) for model reduction of linear multi-input multi-output (MIMO) systems with various numbers of inputs and outputs. A salient feature of the proposed MCFE approach to model reduction of MIMO systems with square transfer matrices is its equivalence to the matrix Pade approximation approach. The Cauer second form of the ordinary MCFE for a square transfer function matrix is generalized in this paper to a multipoint and nonsquare-matrix version. An interesting connection of the multipoint Cauer MCFE method to the multipoint matrix Pade approximation method is established. Also, algorithms for obtaining the reduced-degree matrix-fraction descriptions and reduced-dimensional state-space models from a transfer function matrix via the multipoint Cauer MCFE algorithm are presented. Practical advantages of using the multipoint Cauer MCFE are discussed and a numerical example is provided to illustrate the algorithms.

Analytical Solutions for Radiative Transfer: Implications for Giant Planet Formation by Disk Instability

NASA Astrophysics Data System (ADS)

Boss, Alan P.

2009-03-01

The disk instability mechanism for giant planet formation is based on the formation of clumps in a marginally gravitationally unstable protoplanetary disk, which must lose thermal energy through a combination of convection and radiative cooling if they are to survive and contract to become giant protoplanets. While there is good observational support for forming at least some giant planets by disk instability, the mechanism has become theoretically contentious, with different three-dimensional radiative hydrodynamics codes often yielding different results. Rigorous code testing is required to make further progress. Here we present two new analytical solutions for radiative transfer in spherical coordinates, suitable for testing the code employed in all of the Boss disk instability calculations. The testing shows that the Boss code radiative transfer routines do an excellent job of relaxing to and maintaining the analytical results for the radial temperature and radiative flux profiles for a spherical cloud with high or moderate optical depths, including the transition from optically thick to optically thin regions. These radial test results are independent of whether the Eddington approximation, diffusion approximation, or flux-limited diffusion approximation routines are employed. The Boss code does an equally excellent job of relaxing to and maintaining the analytical results for the vertical (θ) temperature and radiative flux profiles for a disk with a height proportional to the radial distance. These tests strongly support the disk instability mechanism for forming giant planets.

Ice particle mass-dimensional parameter retrieval and uncertainty analysis using an Optimal Estimation framework applied to in situ data

NASA Astrophysics Data System (ADS)

Xu, Zhuocan; Mace, Jay; Avalone, Linnea; Wang, Zhien

2015-04-01

The extreme variability of ice particle habits in precipitating clouds affects our understanding of these cloud systems in every aspect (i.e. radiation transfer, dynamics, precipitation rate, etc) and largely contributes to the uncertainties in the model representation of related processes. Ice particle mass-dimensional power law relationships, M=a*(D ^ b), are commonly assumed in models and retrieval algorithms, while very little knowledge exists regarding the uncertainties of these M-D parameters in real-world situations. In this study, we apply Optimal Estimation (OE) methodology to infer ice particle mass-dimensional relationship from ice particle size distributions and bulk water contents independently measured on board the University of Wyoming King Air during the Colorado Airborne Multi-Phase Cloud Study (CAMPS). We also utilize W-band radar reflectivity obtained on the same platform (King Air) offering a further constraint to this ill-posed problem (Heymsfield et al. 2010). In addition to the values of retrieved M-D parameters, the associated uncertainties are conveniently acquired in the OE framework, within the limitations of assumed Gaussian statistics. We find, given the constraints provided by the bulk water measurement and in situ radar reflectivity, that the relative uncertainty of mass-dimensional power law prefactor (a) is approximately 80% and the relative uncertainty of exponent (b) is 10-15%. With this level of uncertainty, the forward model uncertainty in radar reflectivity would be on the order of 4 dB or a factor of approximately 2.5 in ice water content. The implications of this finding are that inferences of bulk water from either remote or in situ measurements of particle spectra cannot be more certain than this when the mass-dimensional relationships are not known a priori which is almost never the case.

Heat transfer in porous medium embedded with vertical plate: Non-equilibrium approach - Part B

DOE Office of Scientific and Technical Information (OSTI.GOV)

Quadir, G. A., E-mail: Irfan-magami@Rediffmail.com, E-mail: gaquadir@gmail.com; Badruddin, Irfan Anjum

2016-06-08

This work is continuation of the paper Part A. Due to large number of results, the paper is divided into two section with section-A (Part A) discussing the effect of various parameters such as heat transfer coefficient parameter, thermal conductivity ratio etc. on streamlines and isothermal lines. Section-B highlights the heat transfer characteristics in terms of Nusselt number The Darcy model is employed to simulate the flow inside the medium. It is assumed that the heat transfer takes place by convection and radiation. The governing partial differential equations are converted into non-dimensional form and solved numerically using finite element method.

Dependence of optimal initial density on laser parameters for multi-keV x-ray radiators generated by nanosecond laser-produced underdense plasma

NASA Astrophysics Data System (ADS)

Tu, Shao-yong; Yuan, Yong-teng; Hu, Guang-yue; Miao, Wen-yong; Zhao, Bin; Zheng, Jian; Jiang, Shao-en; Ding, Yong-kun

2016-01-01

Efficient multi-keV x-ray sources can be produced using nanosecond laser pulse-heated middle-Z underdense plasmas generated using gas or foam. Previous experimental results show that an optimal initial target density exists for efficient multi-keV x-ray emission at which the laser ionization wave is supersonic. Here we explore the influence of the laser intensity and the pulse duration on this optimal initial target density via a one-dimensional radiation hydrodynamic simulation. The simulation shows that the optimal initial density is sensitive to both the laser intensity and the pulse duration. However, the speed of the supersonic ionization wave at the end of the laser irradiation is always maintained at 1.5 to 1.7 times that of the ion acoustic wave under the optimal initial density conditions.

Simulation of one-dimensional heat transfer system based on the blended coal combustion

NASA Astrophysics Data System (ADS)

Jin, Y. G.; Li, W. B.; Cheng, Z. S.; Cheng, J. W.; liu, Y.

2017-12-01

In this paper, the supercritical boiler thermodynamic calculation model is studied. Three types of heat exchangers are proposed, namely furnace (total radiation type), semi-radiation and convection, and discussed. Two cases were simulated - mixing of two bituminous coals and mixing of a bituminous coal and lignite- order to analyze the performance on the flue gas side. The study shows that the influence of flue air leakage and gas distribution coefficient on the system.

Radiation characteristics of water droplets in a fire-inspired environment: A Monte Carlo ray tracing study

NASA Astrophysics Data System (ADS)

Wu, Bifen; Zhao, Xinyu

2018-06-01

The effects of radiation of water mists in a fire-inspired environment are numerically investigated for different complexities of radiative media in a three-dimensional cubic enclosure. A Monte Carlo ray tracing (MCRT) method is employed to solve the radiative transfer equation (RTE). The anisotropic scattering behaviors of water mists are modeled by a combination of the Mie theory and the Henyey-Greestein relation. A tabulation method considering the size and wavelength dependencies is established for water droplets, to reduce the computational cost associated with the evaluation of the nongray spectral properties of water mists. Validation and verification of the coupled MCRT solver are performed using a one-dimensional slab with gray gas in comparison with the analytical solutions. Parametric studies are then performed using a three-dimensional cubic box to examine radiation of two monodispersed and one polydispersed water mist systems. The tabulation method can reduce the computational cost by a factor of one hundred. Results obtained without any scattering model better conform with results obtained from the anisotropic model than the isotropic scattering model, when a highly directional emissive source is applied. For isotropic emissive sources, isotropic and anisotropic scattering models predict comparable results. The addition of different volume fractions of soot shows that soot may have a negative impact on the effectiveness of water mists in absorbing radiation when its volume fraction exceeds certain threshold.

An advanced model of heat and mass transfer in the protective clothing - verification

NASA Astrophysics Data System (ADS)

Łapka, P.; Furmański, P.

2016-09-01

The paper presents an advanced mathematical and numerical models of heat and mass transfer in the multi-layers protective clothing and in elements of the experimental stand subjected to either high surroundings temperature or high radiative heat flux emitted by hot objects. The model included conductive-radiative heat transfer in the hygroscopic porous fabrics and air gaps as well as conductive heat transfer in components of the stand. Additionally, water vapour diffusion in the pores and air spaces as well as phase transition of the bound water in the fabric fibres (sorption and desorption) were accounted for. The thermal radiation was treated in the rigorous way e.g.: semi-transparent absorbing, emitting and scattering fabrics were assumed a non-grey and all optical phenomena at internal or external walls were modelled. The air was assumed transparent. Complex energy and mass balance as well as optical conditions at internal or external interfaces were formulated in order to find exact values of temperatures, vapour densities and radiation intensities at these interfaces. The obtained highly non-linear coupled system of discrete equation was solve by the in-house iterative algorithm which was based on the Finite Volume Method. The model was then successfully partially verified against the results obtained from commercial software for simplified cases.

Development of a radiative heating facility for studying flow and heat transfer in hydrocarbon-cooled structures

NASA Astrophysics Data System (ADS)

Dong, Da; Lu, Yang; Yuan, Yueming; Fan, Xuejun

2018-06-01

An experimental facility was designed to simulate the heat exchange between the hot gas and the fuel-cooled wall in a scramjet combustor. Thermal radiation from an electrically heated graphite plate is employed to unilaterally heat up a multi-channeled cooling plate. A maximum heat flux of over 0.8 MW/m2 was achieved for an effective heating area up to 1000 mm × 40 mm. Precise control of the back pressure of a coolant (up to 5 MPa) in a unique way was also demonstrated. With this facility, studies of flow and heat transfer in hydrocarbon-cooled structures can be performed under a well-controlled manner.

The DMRT-ML Model: Numerical Simulations of the Microwave Emission of Snowpacks Based on the Dense Media Radiative Transfer Theory

NASA Technical Reports Server (NTRS)

Picard, Ghislain; Brucker, Ludovic; Roy, Alexandre; DuPont, FLorent; Champollion, Nicolas; Morin, Samuel

2014-01-01

Microwave radiometer observations have been used to retrieve snow depth and snow water equivalent on both land and sea ice, snow accumulation on ice sheets, melt events, snow temperature, and snow grain size. Modeling the microwave emission from snow and ice physical properties is crucial to improve the quality of these retrievals. It also is crucial to improve our understanding of the radiative transfer processes within the snow cover, and the snow properties most relevant in microwave remote sensing. Our objective is to present a recent microwave emission model and its validation. The model is named DMRT-ML (DMRT Multi-Layer).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sierra Thermal /Fluid Team

The SIERRA Low Mach Module: Fuego along with the SIERRA Participating Media Radiation Module: Syrinx, henceforth referred to as Fuego and Syrinx, respectively, are the key elements of the ASCI fire environment simulation project. The fire environment simulation project is directed at characterizing both open large-scale pool fires and building enclosure fires. Fuego represents the turbulent, buoyantly-driven incompressible flow, heat transfer, mass transfer, combustion, soot, and absorption coefficient model portion of the simulation software. Syrinx represents the participating-media thermal radiation mechanics. This project is an integral part of the SIERRA multi-mechanics software development project. Fuego depends heavily upon the coremore » architecture developments provided by SIERRA for massively parallel computing, solution adaptivity, and mechanics coupling on unstructured grids.« less

Three-dimensional radiation transfer modeling in a dicotyledon leaf

NASA Astrophysics Data System (ADS)

Govaerts, Yves M.; Jacquemoud, Stéphane; Verstraete, Michel M.; Ustin, Susan L.

1996-11-01

The propagation of light in a typical dicotyledon leaf is investigated with a new Monte Carlo ray-tracing model. The three-dimensional internal cellular structure of the various leaf tissues, including the epidermis, the palisade parenchyma, and the spongy mesophyll, is explicitly described. Cells of different tissues are assigned appropriate morphologies and contain realistic amounts of water and chlorophyll. Each cell constituent is characterized by an index of refraction and an absorption coefficient. The objective of this study is to investigate how the internal three-dimensional structure of the tissues and the optical properties of cell constituents control the reflectance and transmittance of the leaf. Model results compare favorably with laboratory observations. The influence of the roughness of the epidermis on the reflection and absorption of light is investigated, and simulation results confirm that convex cells in the epidermis focus light on the palisade parenchyma and increase the absorption of radiation.

Radiative heat transfer in strongly forward scattering media using the discrete ordinates method

NASA Astrophysics Data System (ADS)

Granate, Pedro; Coelho, Pedro J.; Roger, Maxime

2016-03-01

The discrete ordinates method (DOM) is widely used to solve the radiative transfer equation, often yielding satisfactory results. However, in the presence of strongly forward scattering media, this method does not generally conserve the scattering energy and the phase function asymmetry factor. Because of this, the normalization of the phase function has been proposed to guarantee that the scattering energy and the asymmetry factor are conserved. Various authors have used different normalization techniques. Three of these are compared in the present work, along with two other methods, one based on the finite volume method (FVM) and another one based on the spherical harmonics discrete ordinates method (SHDOM). In addition, the approximation of the Henyey-Greenstein phase function by a different one is investigated as an alternative to the phase function normalization. The approximate phase function is given by the sum of a Dirac delta function, which accounts for the forward scattering peak, and a smoother scaled phase function. In this study, these techniques are applied to three scalar radiative transfer test cases, namely a three-dimensional cubic domain with a purely scattering medium, an axisymmetric cylindrical enclosure containing an emitting-absorbing-scattering medium, and a three-dimensional transient problem with collimated irradiation. The present results show that accurate predictions are achieved for strongly forward scattering media when the phase function is normalized in such a way that both the scattered energy and the phase function asymmetry factor are conserved. The normalization of the phase function may be avoided using the FVM or the SHDOM to evaluate the in-scattering term of the radiative transfer equation. Both methods yield results whose accuracy is similar to that obtained using the DOM along with normalization of the phase function. Very satisfactory predictions were also achieved using the delta-M phase function, while the delta-Eddington phase function and the transport approximation may perform poorly.

Radiative Transfer Modeling to Estimate the Impact of CDOM on Light Absorption within Changing Arctic Sea Ice

NASA Astrophysics Data System (ADS)

Carns, R.; Light, B.; Frey, K. E.

2016-12-01

First-year sea ice differs from multi-year sea ice in several ways that can influence its optical properties. It is thinner than multi-year ice, which tends to increase light transmission. Also, first-year ice retains higher brine volumes in comparison to more heavily drained multi-year ice, in isolated pockets and channels. During melt season, patterns of pond formation on first-year sea ice differ from those on multi-year ice. As first-year sea ice comprises an increasingly large fraction of Arctic sea ice, it becomes more important to understand how much sunlight reaches the ecosystems within the ice, and how those changing ecosystems can feed back into the transmission of light. Colored dissolved organic matter (CDOM) and chlorophyll within the ice can absorb light, heating the ice and reducing transmission to the ocean below. Light also encourages algal growth within the ice while degrading CDOM, creating complex feedbacks. We use radiative transfer models to determine the overall effect of colored dissolved organic matter on the light regime within sea ice, both on the overall amount of energy transmitted and on the spectral distribution of energy. Using models allows us to estimate the impact of varying CDOM levels on a wide range of sea ice types, improving our ability to respond to conditions in a rapidly changing Arctic and predict important phenomena such as algal blooms.

Doppler effects on 3-D non-LTE radiation transport and emission spectra.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Giuliani, J. L.; Davis, J.; DasGupta, A.

2010-10-01

Spatially and temporally resolved X-ray emission lines contain information about temperatures, densities, velocities, and the gradients in a plasma. Extracting this information from optically thick lines emitted from complex ions in dynamic, three-dimensional, non-LTE plasmas requires self-consistent accounting for both non-LTE atomic physics and non-local radiative transfer. We present a brief description of a hybrid-structure spectroscopic atomic model coupled to an iterative tabular on-the-spot treatment of radiative transfer that can be applied to plasmas of arbitrary material composition, conditions, and geometries. The effects of Doppler line shifts on the self-consistent radiative transfer within the plasma and the emergent emission andmore » absorption spectra are included in the model. Sample calculations for a two-level atom in a uniform cylindrical plasma are given, showing reasonable agreement with more sophisticated transport models and illustrating the potential complexity - or richness - of radially resolved emission lines from an imploding cylindrical plasma. Also presented is a comparison of modeled L- and K-shell spectra to temporally and radially resolved emission data from a Cu:Ni plasma. Finally, some shortcomings of the model and possible paths for improvement are discussed.« less

Computing Radiative Transfer in a 3D Medium

NASA Technical Reports Server (NTRS)

Von Allmen, Paul; Lee, Seungwon

2012-01-01

A package of software computes the time-dependent propagation of a narrow laser beam in an arbitrary three- dimensional (3D) medium with absorption and scattering, using the transient-discrete-ordinates method and a direct integration method. Unlike prior software that utilizes a Monte Carlo method, this software enables simulation at very small signal-to-noise ratios. The ability to simulate propagation of a narrow laser beam in a 3D medium is an improvement over other discrete-ordinate software. Unlike other direct-integration software, this software is not limited to simulation of propagation of thermal radiation with broad angular spread in three dimensions or of a laser pulse with narrow angular spread in two dimensions. Uses for this software include (1) computing scattering of a pulsed laser beam on a material having given elastic scattering and absorption profiles, and (2) evaluating concepts for laser-based instruments for sensing oceanic turbulence and related measurements of oceanic mixed-layer depths. With suitable augmentation, this software could be used to compute radiative transfer in ultrasound imaging in biological tissues, radiative transfer in the upper Earth crust for oil exploration, and propagation of laser pulses in telecommunication applications.

Effect of Surface Reflectivity Variations On Uv-visible Limb Scattering Measurements of The Atmosphere

NASA Astrophysics Data System (ADS)

Oikarinen, L.

Solar UV and visible radiation scattered at the limb of the Earth's atmosphere is used for measuring density profiles of atmosperic trace gases. For example, the OSIRIS instrument on Odin and SCIAMACHY on Envisat use this technique. A limb-viewing instrument does not see Earth's surface or tropospheric clouds directly. However, in- direct light reflected from the surface or low altitude clouds can make up tens of per cents of the signal. Furthermore, the surface area that contributes to limb intensity ex- tends over 1000 km along the instrument line-of-sight and 200 km across it. Over this area surface reflectivity can vary from almost 0% to 100%. Inaccurate modelling of reflected intensity is a potential source of error in the trace gas retrieval. Generally, radiative transfer models used for analysing limb measure- ments have to assume that the surface has a constant albedo. We have used a three- dimensional Monte Carlo radiative transfer model to study the effects of surface vari- ation to limb radiance. Based on the simulations, we have developed an approximate method for averaging surface albedo for limb scattering measurements with the help of a simple single scattering radiative transfer model.

Transitional flow in thin tubes for space station freedom radiator

NASA Technical Reports Server (NTRS)

Loney, Patrick; Ibrahim, Mounir

1995-01-01

A two dimensional finite volume method is used to predict the film coefficients in the transitional flow region (laminar or turbulent) for the radiator panel tubes. The code used to perform this analysis is CAST (Computer Aided Simulation of Turbulent Flows). The information gathered from this code is then used to augment a Sinda85 model that predicts overall performance of the radiator. A final comparison is drawn between the results generated with a Sinda85 model using the Sinda85 provided transition region heat transfer correlations and the Sinda85 model using the CAST generated data.

Topical Review: Polymer gel dosimetry

PubMed Central

Baldock, C; De Deene, Y; Doran, S; Ibbott, G; Jirasek, A; Lepage, M; McAuley, K B; Oldham, M; Schreiner, L J

2010-01-01

Polymer gel dosimeters are fabricated from radiation sensitive chemicals which, upon irradiation, polymerize as a function of the absorbed radiation dose. These gel dosimeters, with the capacity to uniquely record the radiation dose distribution in three-dimensions (3D), have specific advantages when compared to one-dimensional dosimeters, such as ion chambers, and two-dimensional dosimeters, such as film. These advantages are particularly significant in dosimetry situations where steep dose gradients exist such as in intensity-modulated radiation therapy (IMRT) and stereotactic radiosurgery. Polymer gel dosimeters also have specific advantages for brachytherapy dosimetry. Potential dosimetry applications include those for low-energy x-rays, high-linear energy transfer (LET) and proton therapy, radionuclide and boron capture neutron therapy dosimetries. These 3D dosimeters are radiologically soft-tissue equivalent with properties that may be modified depending on the application. The 3D radiation dose distribution in polymer gel dosimeters may be imaged using magnetic resonance imaging (MRI), optical-computerized tomography (optical-CT), x-ray CT or ultrasound. The fundamental science underpinning polymer gel dosimetry is reviewed along with the various evaluation techniques. Clinical dosimetry applications of polymer gel dosimetry are also presented. PMID:20150687

Multidimensional Modeling of Atmospheric Effects and Surface Heterogeneities on Remote Sensing

NASA Technical Reports Server (NTRS)

Gerstl, S. A. W.; Simmer, C.; Zardecki, A. (Principal Investigator)

1985-01-01

The overall goal of this project is to establish a modeling capability that allows a quantitative determination of atmospheric effects on remote sensing including the effects of surface heterogeneities. This includes an improved understanding of aerosol and haze effects in connection with structural, angular, and spatial surface heterogeneities. One important objective of the research is the possible identification of intrinsic surface or canopy characteristics that might be invariant to atmospheric perturbations so that they could be used for scene identification. Conversely, an equally important objective is to find a correction algorithm for atmospheric effects in satellite-sensed surface reflectances. The technical approach is centered around a systematic model and code development effort based on existing, highly advanced computer codes that were originally developed for nuclear radiation shielding applications. Computational techniques for the numerical solution of the radiative transfer equation are adapted on the basis of the discrete-ordinates finite-element method which proved highly successful for one and two-dimensional radiative transfer problems with fully resolved angular representation of the radiation field.

Synchrotron radiation-based quasi-elastic scattering using time-domain interferometry with multi-line gamma rays.

PubMed

Saito, Makina; Masuda, Ryo; Yoda, Yoshitaka; Seto, Makoto

2017-10-02

We developed a multi-line time-domain interferometry (TDI) system using 14.4 keV Mössbauer gamma rays with natural energy widths of 4.66 neV from 57 Fe nuclei excited using synchrotron radiation. Electron density fluctuations can be detected at unique lengths ranging from 0.1 nm to a few nm on time scales from several nanoseconds to the sub-microsecond order by quasi-elastic gamma-ray scattering (QGS) experiments using multi-line TDI. In this report, we generalize the established expression for a time spectrum measured using an identical single-line gamma-ray emitter pair to the case of a nonidentical pair of multi-line gamma-ray emitters by considering the finite energy width of the incident synchrotron radiation. The expression obtained illustrates the unique characteristics of multi-line TDI systems, where the finite incident energy width and use of a nonidentical emitter pair produces further information on faster sub-picosecond-scale dynamics in addition to the nanosecond dynamics; this was demonstrated experimentally. A normalized intermediate scattering function was extracted from the spectrum and its relaxation form was determined for a relaxation time of the order of 1 μs, even for relatively large momentum transfer of ~31 nm -1 . The multi-line TDI method produces a microscopic relaxation picture more rapidly and accurately than conventional single-line TDI.

Effects of variable electrical conductivity and thermal conductivity on unsteady MHD free convection flow past an exponential accelerated inclined plate

NASA Astrophysics Data System (ADS)

Rana, B. M. Jewel; Ahmed, Rubel; Ahmmed, S. F.

2017-06-01

An analysis is carried out to investigate the effects of variable viscosity, thermal radiation, absorption of radiation and cross diffusion past an inclined exponential accelerated plate under the influence of variable heat and mass transfer. A set of suitable transformations has been used to obtain the non-dimensional coupled governing equations. Explicit finite difference technique has been used to solve the obtained numerical solutions of the present problem. Stability and convergence of the finite difference scheme have been carried out for this problem. Compaq Visual Fortran 6.6a has been used to calculate the numerical results. The effects of various physical parameters on the fluid velocity, temperature, concentration, coefficient of skin friction, rate of heat transfer, rate of mass transfer, streamlines and isotherms on the flow field have been presented graphically and discussed in details.

Mechanical exfoliation of two-dimensional materials

NASA Astrophysics Data System (ADS)

Gao, Enlai; Lin, Shao-Zhen; Qin, Zhao; Buehler, Markus J.; Feng, Xi-Qiao; Xu, Zhiping

2018-06-01

Two-dimensional materials such as graphene and transition metal dichalcogenides have been identified and drawn much attention over the last few years for their unique structural and electronic properties. However, their rise begins only after these materials are successfully isolated from their layered assemblies or adhesive substrates into individual monolayers. Mechanical exfoliation and transfer are the most successful techniques to obtain high-quality single- or few-layer nanocrystals from their native multi-layer structures or their substrate for growth, which involves interfacial peeling and intralayer tearing processes that are controlled by material properties, geometry and the kinetics of exfoliation. This procedure is rationalized in this work through theoretical analysis and atomistic simulations. We propose a criterion to assess the feasibility for the exfoliation of two-dimensional sheets from an adhesive substrate without fracturing itself, and explore the effects of material and interface properties, as well as the geometrical, kinetic factors on the peeling behaviors and the torn morphology. This multi-scale approach elucidates the microscopic mechanism of the mechanical processes, offering predictive models and tools for the design of experimental procedures to obtain single- or few-layer two-dimensional materials and structures.

Detecting Shielded Special Nuclear Materials Using Multi-Dimensional Neutron Source and Detector Geometries

NASA Astrophysics Data System (ADS)

Santarius, John; Navarro, Marcos; Michalak, Matthew; Fancher, Aaron; Kulcinski, Gerald; Bonomo, Richard

2016-10-01

A newly initiated research project will be described that investigates methods for detecting shielded special nuclear materials by combining multi-dimensional neutron sources, forward/adjoint calculations modeling neutron and gamma transport, and sparse data analysis of detector signals. The key tasks for this project are: (1) developing a radiation transport capability for use in optimizing adaptive-geometry, inertial-electrostatic confinement (IEC) neutron source/detector configurations for neutron pulses distributed in space and/or phased in time; (2) creating distributed-geometry, gas-target, IEC fusion neutron sources; (3) applying sparse data and noise reduction algorithms, such as principal component analysis (PCA) and wavelet transform analysis, to enhance detection fidelity; and (4) educating graduate and undergraduate students. Funded by DHS DNDO Project 2015-DN-077-ARI095.

Optical characterization of multi-scale morphologically complex heterogeneous media - Application to snow with soot impurities

NASA Astrophysics Data System (ADS)

Dai, Xiaoyu; Haussener, Sophia

2018-02-01

A multi-scale methodology for the radiative transfer analysis of heterogeneous media composed of morphologically-complex components on two distinct scales is presented. The methodology incorporates the exact morphology at the various scales and utilizes volume-averaging approaches with the corresponding effective properties to couple the scales. At the continuum level, the volume-averaged coupled radiative transfer equations are solved utilizing (i) effective radiative transport properties obtained by direct Monte Carlo simulations at the pore level, and (ii) averaged bulk material properties obtained at particle level by Lorenz-Mie theory or discrete dipole approximation calculations. This model is applied to a soot-contaminated snow layer, and is experimentally validated with reflectance measurements of such layers. A quantitative and decoupled understanding of the morphological effect on the radiative transport is achieved, and a significant influence of the dual-scale morphology on the macroscopic optical behavior is observed. Our results show that with a small amount of soot particles, of the order of 1ppb in volume fraction, the reduction in reflectance of a snow layer with large ice grains can reach up to 77% (at a wavelength of 0.3 μm). Soot impurities modeled as compact agglomerates yield 2-3% lower reduction of the reflectance in a thick show layer compared to snow with soot impurities modeled as chain-like agglomerates. Soot impurities modeled as equivalent spherical particles underestimate the reflectance reduction by 2-8%. This study implies that the morphology of the heterogeneities in a media significantly affects the macroscopic optical behavior and, specifically for the soot-contaminated snow, indicates the non-negligible role of soot on the absorption behavior of snow layers. It can be equally used in technical applications for the assessment and optimization of optical performance in multi-scale media.

Self-consistent analysis of radiation and relativistic electron beam dynamics in a helical wiggler using Lienard-Wiechert fields

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tecimer, M.; Elias, L.R.

1995-12-31

Lienard-Wiechert (LW) fields, which are exact solutions of the Wave Equation for a point charge in free space, are employed to formulate a self-consistent treatment of the electron beam dynamics and the evolution of the generated radiation in long undulators. In a relativistic electron beam the internal forces leading to the interaction of the electrons with each other can be computed by means of retarded LW fields. The resulting electron beam dynamics enables us to obtain three dimensional radiation fields starting from an initial incoherent spontaneous emission, without introducing a seed wave at start-up. Based on the formalism employed here,more » both the evolution of the multi-bucket electron phase space dynamics in the beam body as well as edges and the relative slippage of the radiation with respect to the electrons in the considered short bunch are naturally embedded into the simulation model. In this paper, we present electromagnetic radiation studies, including multi-bucket electron phase dynamics and angular distribution of radiation in the time and frequency domain produced by a relativistic short electron beam bunch interacting with a circularly polarized magnetic undulator.« less

Finite Volume Numerical Methods for Aeroheating Rate Calculations from Infrared Thermographic Data

NASA Technical Reports Server (NTRS)

Daryabeigi, Kamran; Berry, Scott A.; Horvath, Thomas J.; Nowak, Robert J.

2006-01-01

The use of multi-dimensional finite volume heat conduction techniques for calculating aeroheating rates from measured global surface temperatures on hypersonic wind tunnel models was investigated. Both direct and inverse finite volume techniques were investigated and compared with the standard one-dimensional semi-infinite technique. Global transient surface temperatures were measured using an infrared thermographic technique on a 0.333-scale model of the Hyper-X forebody in the NASA Langley Research Center 20-Inch Mach 6 Air tunnel. In these tests the effectiveness of vortices generated via gas injection for initiating hypersonic transition on the Hyper-X forebody was investigated. An array of streamwise-orientated heating striations was generated and visualized downstream of the gas injection sites. In regions without significant spatial temperature gradients, one-dimensional techniques provided accurate aeroheating rates. In regions with sharp temperature gradients caused by striation patterns multi-dimensional heat transfer techniques were necessary to obtain more accurate heating rates. The use of the one-dimensional technique resulted in differences of 20% in the calculated heating rates compared to 2-D analysis because it did not account for lateral heat conduction in the model.

Cellular organization and spectral diversity of GFP-like proteins in live coral cells studied by single and multiphoton imaging and microspectroscopy

NASA Astrophysics Data System (ADS)

Salih, Anya; Cox, Guy C.; Larkum, Anthony W.

2003-07-01

Tissues of many marine invertebrates of class Anthozoa contain intensely fluorescent or brightly coloured pigments. These pigments belong to a family of photoactive proteins closely related to Green Fluorescent Protein (GFP), and their emissions range from blue to red wavelengths. The great diversity of these pigments has only recently been realised. To investigate the role of these proteins in corals, we have performed an in vivo fluorescent pigment (FP) spectral and cellular distribution analyses in live coral cells using single and multi-photon laser scanning imaging and microspectroscopy. These analyses revealed that even single colour corals contain spectroscopically heterogeneous pigment mixtures, with 2-5 major colour types in the same area of tissue. They were typically arranged in step-wise light emission energy gradients (e.g. blue, green, yellow, red). The successive overlapping emission-excitation spectral profiles of differently coloured FPs suggested that they were suited for sequential energy coupling. Traces of red FPs (emission = 570-660 nm) were present, even in non-red corals. We confirmed that radiative energy transfer could occur between separate granules of blue and green FPs and that energy transfer was inversely proportional to the square of the distance between them. Multi-photon micro-spectrofluorometric analysis gave significantly improved spectral resolution by restricting FP excitation to a single point in the focal plane of the sample. Pigment heterogeneity at small scales within granules suggested that fluorescence resonance energy transfer (FRET) might be occurring, and we confirmed that this was the case. Thus, energy transfer can take place both radiatively and by FRET, probably functioning in photoprotection by dissipation of excessive solar radiation.

Amazon forest structure generates diurnal and seasonal variability in light utilization

Treesearch

Douglas C. Morton; Jeremy Rubio; Bruce D. Cook; Jean-Philippe Gastellu-Etchegorry; Marcos Longo; Hyeungu Choi; Maria Hunter; Michael Keller

2016-01-01

The complex three-dimensional (3-D) structure of tropical forests generates a diversity of light environments for canopy and understory trees. Understanding diurnal and seasonal changes in light availability is critical for interpreting measurements of net ecosystem exchange and improving ecosystem models. Here, we used the Discrete Anisotropic Radiative Transfer (DART...

Inverse Heat Conduction Methods in the CHAR Code for Aerothermal Flight Data Reconstruction

NASA Technical Reports Server (NTRS)

Oliver, A Brandon; Amar, Adam J.

2016-01-01

Reconstruction of flight aerothermal environments often requires the solution of an inverse heat transfer problem, which is an ill-posed problem of specifying boundary conditions from discrete measurements in the interior of the domain. This paper will present the algorithms implemented in the CHAR code for use in reconstruction of EFT-1 flight data and future testing activities. Implementation nuances will be discussed, and alternative hybrid-methods that are permitted by the implementation will be described. Results will be presented for a number of one-dimensional and multi-dimensional problems

Three-dimensional radiative transfer models of clumpy tori in Seyfert galaxies

NASA Astrophysics Data System (ADS)

Schartmann, M.; Meisenheimer, K.; Camenzind, M.; Wolf, S.; Tristram, K. R. W.; Henning, T.

2008-04-01

Context: Tori of Active Galactic Nuclei (AGN) are made up of a mixture of hot and cold gas, as well as dust. In order to protect the dust grains from destruction by the surrounding hot gas as well as by the energetic (UV/optical) radiation from the accretion disk, the dust is often assumed to be distributed in clouds. Aims: A new three-dimensional model of AGN dust tori is extensively investigated. The torus is modelled as a wedge-shaped disk within which dusty clouds are randomly distributed throughout the volume, by taking the dust density distribution of the corresponding continuous model into account. We especially concentrate on the differences between clumpy and continuous models in terms of the temperature distributions, the surface brightness distributions and interferometric visibilities, as well as spectral energy distributions. Methods: Radiative transfer calculations with the help of the three-dimensional Monte Carlo radiative transfer code MC3D are used in order to simulate spectral energy distributions as well as surface brightness distributions at various wavelengths. In a second step, interferometric visibilities for various inclination as well as position angles and baselines are calculated, which can be used to directly compare our models to interferometric observations with the MIDI instrument. Results: We find that the radial temperature distributions of clumpy models possess significantly enhanced scatter compared to the continuous cases. Even at large distances, clouds can be heated directly by the central accretion disk. The existence of the silicate 10 μm-feature in absorption or in emission depends sensitively on the distribution, the size and optical depth of clouds in the innermost part of the dust distribution. With this explanation, failure and success of previous modelling efforts of clumpy tori can be understood. The main reason for this outcome are shadowing effects of clouds within the central region. We underline this result with the help of several parameter variations. After adapting the parameters of our clumpy standard model to the circumstances of the Seyfert 2 Circinus galaxy, it can qualitatively explain recent mid-infrared interferometric observations performed with MIDI, as well as high resolution spectral data.

Core-Collapse Supernovae Explored by Multi-D Boltzmann Hydrodynamic Simulations

NASA Astrophysics Data System (ADS)

Sumiyoshi, Kohsuke; Nagakura, Hiroki; Iwakami, Wakana; Furusawa, Shun; Matsufuru, Hideo; Imakura, Akira; Yamada, Shoichi

We report the latest results of numerical simulations of core-collapse supernovae by solving multi-D neutrino-radiation hydrodynamics with Boltzmann equations. One of the longstanding issues of the explosion mechanism of supernovae has been uncertainty in the approximations of the neutrino transfer in multi-D such as the diffusion approximation and ray-by-ray method. The neutrino transfer is essential, together with 2D/3D hydrodynamical instabilities, to evaluate the neutrino heating behind the shock wave for successful explosions and to predict the neutrino burst signals. We tackled this difficult problem by utilizing our solver of the 6D Boltzmann equation for neutrinos in 3D space and 3D neutrino momentum space coupled with multi-D hydrodynamics adding special and general relativistic extensions. We have performed a set of 2D core-collapse simulations from 11M ⊙ and 15M ⊙ stars on K-computer in Japan by following long-term evolution over 400 ms after bounce to reveal the outcome from the full Boltzmann hydrodynamic simulations with a sophisticated equation of state with multi-nuclear species and updated rates for electron captures on nuclei.

Fast and Accurate Hybrid Stream PCRTMSOLAR Radiative Transfer Model for Reflected Solar Spectrum Simulation in the Cloudy Atmosphere

NASA Technical Reports Server (NTRS)

Yang, Qiguang; Liu, Xu; Wu, Wan; Kizer, Susan; Baize, Rosemary R.

2016-01-01

A hybrid stream PCRTM-SOLAR model has been proposed for fast and accurate radiative transfer simulation. It calculates the reflected solar (RS) radiances with a fast coarse way and then, with the help of a pre-saved matrix, transforms the results to obtain the desired high accurate RS spectrum. The methodology has been demonstrated with the hybrid stream discrete ordinate (HSDO) radiative transfer (RT) model. The HSDO method calculates the monochromatic radiances using a 4-stream discrete ordinate method, where only a small number of monochromatic radiances are simulated with both 4-stream and a larger N-stream (N = 16) discrete ordinate RT algorithm. The accuracy of the obtained channel radiance is comparable to the result from N-stream moderate resolution atmospheric transmission version 5 (MODTRAN5). The root-mean-square errors are usually less than 5x10(exp -4) mW/sq cm/sr/cm. The computational speed is three to four-orders of magnitude faster than the medium speed correlated-k option MODTRAN5. This method is very efficient to simulate thousands of RS spectra under multi-layer clouds/aerosols and solar radiation conditions for climate change study and numerical weather prediction applications.

2D Radiative Processes Near Cloud Edges

NASA Technical Reports Server (NTRS)

Varnai, T.

2012-01-01

Because of the importance and complexity of dynamical, microphysical, and radiative processes taking place near cloud edges, the transition zone between clouds and cloud free air has been the subject of intense research both in the ASR program and in the wider community. One challenge in this research is that the one-dimensional (1D) radiative models widely used in both remote sensing and dynamical simulations become less accurate near cloud edges: The large horizontal gradients in particle concentrations imply that accurate radiative calculations need to consider multi-dimensional radiative interactions among areas that have widely different optical properties. This study examines the way the importance of multidimensional shortwave radiative interactions changes as we approach cloud edges. For this, the study relies on radiative simulations performed for a multiyear dataset of clouds observed over the NSA, SGP, and TWP sites. This dataset is based on Microbase cloud profiles as well as wind measurements and ARM cloud classification products. The study analyzes the way the difference between 1D and 2D simulation results increases near cloud edges. It considers both monochromatic radiances and broadband radiative heating, and it also examines the influence of factors such as cloud type and height, and solar elevation. The results provide insights into the workings of radiative processes and may help better interpret radiance measurements and better estimate the radiative impacts of this critical region.

Radiative transfer and spectroscopic databases: A line-sampling Monte Carlo approach

NASA Astrophysics Data System (ADS)

Galtier, Mathieu; Blanco, Stéphane; Dauchet, Jérémi; El Hafi, Mouna; Eymet, Vincent; Fournier, Richard; Roger, Maxime; Spiesser, Christophe; Terrée, Guillaume

2016-03-01

Dealing with molecular-state transitions for radiative transfer purposes involves two successive steps that both reach the complexity level at which physicists start thinking about statistical approaches: (1) constructing line-shaped absorption spectra as the result of very numerous state-transitions, (2) integrating over optical-path domains. For the first time, we show here how these steps can be addressed simultaneously using the null-collision concept. This opens the door to the design of Monte Carlo codes directly estimating radiative transfer observables from spectroscopic databases. The intermediate step of producing accurate high-resolution absorption spectra is no longer required. A Monte Carlo algorithm is proposed and applied to six one-dimensional test cases. It allows the computation of spectrally integrated intensities (over 25 cm-1 bands or the full IR range) in a few seconds, regardless of the retained database and line model. But free parameters need to be selected and they impact the convergence. A first possible selection is provided in full detail. We observe that this selection is highly satisfactory for quite distinct atmospheric and combustion configurations, but a more systematic exploration is still in progress.

An iterative phase-space explicit discontinuous Galerkin method for stellar radiative transfer in extended atmospheres

NASA Astrophysics Data System (ADS)

de Almeida, Valmor F.

2017-07-01

A phase-space discontinuous Galerkin (PSDG) method is presented for the solution of stellar radiative transfer problems. It allows for greater adaptivity than competing methods without sacrificing generality. The method is extensively tested on a spherically symmetric, static, inverse-power-law scattering atmosphere. Results for different sizes of atmospheres and intensities of scattering agreed with asymptotic values. The exponentially decaying behavior of the radiative field in the diffusive-transparent transition region, and the forward peaking behavior at the surface of extended atmospheres were accurately captured. The integrodifferential equation of radiation transfer is solved iteratively by alternating between the radiative pressure equation and the original equation with the integral term treated as an energy density source term. In each iteration, the equations are solved via an explicit, flux-conserving, discontinuous Galerkin method. Finite elements are ordered in wave fronts perpendicular to the characteristic curves so that elemental linear algebraic systems are solved quickly by sweeping the phase space element by element. Two implementations of a diffusive boundary condition at the origin are demonstrated wherein the finite discontinuity in the radiation intensity is accurately captured by the proposed method. This allows for a consistent mechanism to preserve photon luminosity. The method was proved to be robust and fast, and a case is made for the adequacy of parallel processing. In addition to classical two-dimensional plots, results of normalized radiation intensity were mapped onto a log-polar surface exhibiting all distinguishing features of the problem studied.

The potential influence of multiple scattering on longwave flux and heating rate simulations with clouds

NASA Astrophysics Data System (ADS)

Kuo, C. P.; Yang, P.; Huang, X.; Feldman, D.; Flanner, M.; Kuo, C.; Mlawer, E. J.

2017-12-01

Clouds, which cover approximately 67% of the globe, serve as one of the major modulators in adjusting radiative energy on the Earth. Since rigorous radiative transfer computations including multiple scattering are costly, only absorption is considered in the longwave spectral bands in the radiation sub-models of the general circulation models (GCMs). Quantification of the effect of ignoring longwave scattering for flux and heating rate simulations is performed by using the GCM version of the Longwave Rapid Radiative Transfer Model (RRTMG_LW) with an implementation with the 16-stream Discrete Ordinates Radiative Transfer (DISORT) Program for a Multi-Layered Plane-Parallel Medium in conjunction with the 2010 CCCM products that merge satellite observations from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO), the CloudSat, the Clouds and the Earth's Radiant Energy System (CERES) and the Moderate Resolution Imaging Spectrometer (MODIS). One-year global simulations show that neglecting longwave scattering overestimates upward flux at the top of the atmosphere (TOA) and underestimates downward flux at the surface by approximately 2.63 and 1.15 W/m2, respectively. Furthermore, when longwave scattering is included in the simulations, the tropopause is cooled by approximately 0.018 K/day and the surface is heated by approximately 0.028 K/day. As a result, the radiative effects of ignoring longwave scattering and doubling CO2 are comparable in magnitude.

Multiple resonant absorber with prism-incorporated graphene and one-dimensional photonic crystals in the visible and near-infrared spectral range

NASA Astrophysics Data System (ADS)

Zou, X. J.; Zheng, G. G.; Chen, Y. Y.; Xu, L. H.; Lai, M.

2018-04-01

A multi-band absorber constructed from prism-incorporated one-dimensional photonic crystal (1D-PhC) containing graphene defects is achieved theoretically in the visible and near-infrared (vis-NIR) spectral range. By means of the transfer matrix method (TMM), the effect of structural parameters on the optical response of the structure has been investigated. It is possible to achieve multi-peak and complete optical absorption. The simulations reveal that the light intensity is enhanced at the graphene plane, and the resonant wavelength and the absorption intensity can also be tuned by tilting the incidence angle of the impinging light. In particular, multiple graphene sheets are embedded in the arrays, without any demand of manufacture process to cut them into periodic patterns. The proposed concept can be extended to other two-dimensional (2D) materials and engineered for promising applications, including selective or multiplex filters, multiple channel sensors, and photodetectors.

A multi-node model for transient heat transfer analysis of stratospheric airships

NASA Astrophysics Data System (ADS)

Alam, Mohammad Irfan; Pant, Rajkumar S.

2017-06-01

This paper describes a seven-node thermal model for transient heat transfer analysis of a solar powered stratospheric airship in floating condition. The solar array is modeled as a three node system, viz., outer layer, solar cell and substrate. The envelope is also modeled in three nodes, and the contained gas is considered as the seventh node. The heat transfer equations involving radiative, infra-red and conductive heat are solved simultaneously using a fourth order Runge-Kutta Method. The model can be used to study the effect of solar radiation, ambient wind, altitude and location of deployment of the airship on the temperature of the solar array. The model has been validated against some experimental data and numerical results quoted in literature. The effect of change in the value of some operational parameters on temperature of the solar array, and hence on its power output is also discussed.

Effect of Elevated Pressure on the Heat Transfer and Power Requirements During Bridgman Growth of PMN-PT Crystals

NASA Technical Reports Server (NTRS)

Bune, Andris; Ostrogorsky, Aleksandar; Marin, Carlos; Nicoara, Irina; Rose, M. Franklin (Technical Monitor)

2000-01-01

Performance of the furnace during Bridgman growth of the lead magnesium niobate-lead titanate crystal (PMN-PT) is analyzed. PMN-PT is electrostrictive ceramic that has near ideal strain-voltage function. Furthermore piezoelectric (2000 to 2300 pC/N) and coupling (92 to 95%) constants are exceptionally good. Due to these properties PMN-PT has wide range of applications - from sonars to transducers in a high precision optical systems. In this research first attempt to crystallize PMN-PT in a Mellen type vertical Bridgman furnace was not successful, as melting temperature of precursor materials was not achieved. At this point choice was between building a new more powerful facility or finding ways to enhance performance of the existing furnace. Besides adjusting power supply to the individual heating elements, redesigning ampoule holding cartridge and improving furnace insulation one more radical improvement was proposed. The entire furnace was placed into the high pressure chamber. Further experiments confirmed that temperature inside the furnace was increased sufficiently to melt precursor materials to obtain PMN-PT. Numerical modeling is undertaken to find limitations of this technique and to predict temperature distribution inside the ampoule. It is of interest also to account for main factors contributing to a higher temperatures achieved in the furnace under the higher pressure (up to 10 atm.). Numerical model of the furnace is based on general purpose finite - element code FIDAP and on previous efforts to model Bridgman type furnace with multiply heaters. In order to account for all heat transfer mechanism involved - conduction, convection and radiation - different parts of the furnace are modeled in accordance with expected dominant mode of heat transfer - conduction in the solid parts, conduction and radiation in the ampoule, gas convection and conduction in the furnace openings complemented with wall-to-wall radiation. Because of these complicating factors, dimensional rather than non-dimensional modeling is performed using steady-state 2-D and 3-D models. Particular attention is paid to the modeling of radiation in a semitransparent material of ampoule 7 sapphire. The radiation model is validated by solving realistic test problem - conduction and radiation heat transfer in the fused quartz. Results are in agreement with both experimental and analytical data.

A MUSIC-based method for SSVEP signal processing.

PubMed

Chen, Kun; Liu, Quan; Ai, Qingsong; Zhou, Zude; Xie, Sheng Quan; Meng, Wei

2016-03-01

The research on brain computer interfaces (BCIs) has become a hotspot in recent years because it offers benefit to disabled people to communicate with the outside world. Steady state visual evoked potential (SSVEP)-based BCIs are more widely used because of higher signal to noise ratio and greater information transfer rate compared with other BCI techniques. In this paper, a multiple signal classification based method was proposed for multi-dimensional SSVEP feature extraction. 2-second data epochs from four electrodes achieved excellent accuracy rates including idle state detection. In some asynchronous mode experiments, the recognition accuracy reached up to 100%. The experimental results showed that the proposed method attained good frequency resolution. In most situations, the recognition accuracy was higher than canonical correlation analysis, which is a typical method for multi-channel SSVEP signal processing. Also, a virtual keyboard was successfully controlled by different subjects in an unshielded environment, which proved the feasibility of the proposed method for multi-dimensional SSVEP signal processing in practical applications.

Evaluating radiative transfer schemes treatment of vegetation canopy architecture in land surface models

NASA Astrophysics Data System (ADS)

Braghiere, Renato; Quaife, Tristan; Black, Emily

2016-04-01

Incoming shortwave radiation is the primary source of energy driving the majority of the Earth's climate system. The partitioning of shortwave radiation by vegetation into absorbed, reflected, and transmitted terms is important for most of biogeophysical processes, including leaf temperature changes and photosynthesis, and it is currently calculated by most of land surface schemes (LSS) of climate and/or numerical weather prediction models. The most commonly used radiative transfer scheme in LSS is the two-stream approximation, however it does not explicitly account for vegetation architectural effects on shortwave radiation partitioning. Detailed three-dimensional (3D) canopy radiative transfer schemes have been developed, but they are too computationally expensive to address large-scale related studies over long time periods. Using a straightforward one-dimensional (1D) parameterisation proposed by Pinty et al. (2006), we modified a two-stream radiative transfer scheme by including a simple function of Sun zenith angle, so-called "structure factor", which does not require an explicit description and understanding of the complex phenomena arising from the presence of vegetation heterogeneous architecture, and it guarantees accurate simulations of the radiative balance consistently with 3D representations. In order to evaluate the ability of the proposed parameterisation in accurately represent the radiative balance of more complex 3D schemes, a comparison between the modified two-stream approximation with the "structure factor" parameterisation and state-of-art 3D radiative transfer schemes was conducted, following a set of virtual scenarios described in the RAMI4PILPS experiment. These experiments have been evaluating the radiative balance of several models under perfectly controlled conditions in order to eliminate uncertainties arising from an incomplete or erroneous knowledge of the structural, spectral and illumination related canopy characteristics typical of model comparisons with in-situ observations. The structure factor parameters were obtained for each canopy structure through the inversion against direct and diffuse fraction of absorbed photosynthetically active radiation (fAPAR), and albedo PAR. Overall, the modified two-stream approximation consistently showed a good agreement with the RAMI4PILPS reference values under direct and diffuse illumination conditions. It is an efficient and accurate tool to derive PAR absorptance and reflectance for scenarios with different canopy densities, leaf densities and soil background albedos, with especial attention to brighter backgrounds, i.e., snowy. The major difficulty of its applicability in the real world is to acquire the parameterisation parameters from in-situ observations. The derivation of parameters from Digital Hemispherical Photographs (DHP) is highly promising at forest stands scales. DHP provide a permanent record and are a valuable information source for position, size, density, and distribution of canopy gaps. The modified two-stream approximation parameters were derived from gap probability data extracted from DHP obtained in a woody savannah in California, USA. Values of fAPAR and albedo PAR were evaluated against a tree-based vegetation canopy model, MAESPA, which used airborne LiDAR data to define the individual-tree locations, and extract structural information such as tree height and crown diameter. The parameterisation improved the performance of a two-stream approximation by making it achieves comparable results to complex 3D model calculations under observed conditions.

The DMRT-ML Model: Numerical Simulations of the Microwave Emission of Snowpacks Based on the Dense Media Radiative Transfer Theory

NASA Technical Reports Server (NTRS)

Brucker, Ludovic; Picard, Ghislain; Roy, Alexandre; Dupont, Florent; Fily, Michel; Royer, Alain

2014-01-01

Microwave radiometer observations have been used to retrieve snow depth and snow water equivalent on both land and sea ice, snow accumulation on ice sheets, melt events, snow temperature, and snow grain size. Modeling the microwave emission from snow and ice physical properties is crucial to improve the quality of these retrievals. It also is crucial to improve our understanding of the radiative transfer processes within the snow cover, and the snow properties most relevant in microwave remote sensing. Our objective is to present a recent microwave emission model and its validation. The model is named DMRT-ML (DMRT Multi-Layer), and is available at http:lgge.osug.frpicarddmrtml.

The hydrogen tunneling splitting in malonaldehyde: A full-dimensional time-independent quantum mechanical method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Feng; Ren, Yinghui; Bian, Wensheng, E-mail: bian@iccas.ac.cn

The accurate time-independent quantum dynamics calculations on the ground-state tunneling splitting of malonaldehyde in full dimensionality are reported for the first time. This is achieved with an efficient method developed by us. In our method, the basis functions are customized for the hydrogen transfer process which has the effect of greatly reducing the size of the final Hamiltonian matrix, and the Lanczos method and parallel strategy are used to further overcome the memory and central processing unit time bottlenecks. The obtained ground-state tunneling splitting of 24.5 cm{sup −1} is in excellent agreement with the benchmark value of 23.8 cm{sup −1}more » computed with the full-dimensional, multi-configurational time-dependent Hartree approach on the same potential energy surface, and we estimate that our reported value has an uncertainty of less than 0.5 cm{sup −1}. Moreover, the role of various vibrational modes strongly coupled to the hydrogen transfer process is revealed.« less

Allometric constraints to inversion of canopy structure from remote sensing

NASA Astrophysics Data System (ADS)

Wolf, A.; Berry, J. A.; Asner, G. P.

2008-12-01

Canopy radiative transfer models employ a large number of vegetation architectural and leaf biochemical attributes. Studies of leaf biochemistry show a wide array of chemical and spectral diversity that suggests that several leaf biochemical constituents can be independently retrieved from multi-spectral remotely sensed imagery. In contrast, attempts to exploit multi-angle imagery to retrieve canopy structure only succeed in finding two or three of the many unknown canopy arhitectural attributes. We examine a database of over 5000 destructive tree harvests from Eurasia to show that allometry - the covariation of plant form across a broad range of plant size and canopy density - restricts the architectural diversity of plant canopies into a single composite variable ranging from young canopies with many short trees with small crowns to older canopies with fewer trees and larger crowns. Moreover, these architectural attributes are closely linked to biomass via allometric constraints such as the "self-thinning law". We use the measured variance and covariance of plant canopy architecture in these stands to drive the radiative transfer model DISORD, which employs the Li-Strahler geometric optics model. This correlations introduced in the Monte Carlo study are used to determine which attributes of canopy architecture lead to important variation that can be observed by multi-angle or multi-spectral satellite observations, using the sun-view geometry characteristic of MODIS observations in different biomes located at different latitude bands. We conclude that although multi-angle/multi-spectral remote sensing is only sensitive to some of the many unknown canopy attributes that ecologists would wish to know, the strong allometric covariation between these attributes and others permits a large number of inferrences, such as forest biomass, that will be meaningful next-generation vegetation products useful for data assimilation.

Spectral Eclipse Timing

NASA Astrophysics Data System (ADS)

Dobbs-Dixon, Ian; Agol, Eric; Deming, Drake

2015-12-01

We utilize multi-dimensional simulations of varying equatorial jet strength to predict wavelength-dependent variations in the eclipse times of gas-giant planets. A displaced hot spot introduces an asymmetry in the secondary eclipse light curve that manifests itself as a measured offset in the timing of the center of eclipse. A multi-wavelength observation of secondary eclipse, one probing the timing of barycentric eclipse at short wavelengths and another probing at longer wavelengths, will reveal the longitudinal displacement of the hot spot and break the degeneracy between this effect and that associated with the asymmetry due to an eccentric orbit. The effect of time offsets was first explored in the IRAC wavebands by Williams et al. Here we improve upon their methodology, extend to a broad range of wavelengths, and demonstrate our technique on a series of multi-dimensional radiative-hydrodynamical simulations of HD 209458b with varying equatorial jet strength and hot-spot displacement. Simulations with the largest hot-spot displacement result in timing offsets of up to 100 s in the infrared. Though we utilize a particular radiative hydrodynamical model to demonstrate this effect, the technique is model independent. This technique should allow a much larger survey of hot-spot displacements with the James Webb Space Telescope than currently accessible with time-intensive phase curves, hopefully shedding light on the physical mechanisms associated with thermal energy advection in irradiated gas giants.

HELIOS: A new open-source radiative transfer code

NASA Astrophysics Data System (ADS)

Malik, Matej; Grosheintz, Luc; Lukas Grimm, Simon; Mendonça, João; Kitzmann, Daniel; Heng, Kevin

2015-12-01

I present the new open-source code HELIOS, developed to accurately describe radiative transfer in a wide variety of irradiated atmospheres. We employ a one-dimensional multi-wavelength two-stream approach with scattering. Written in Cuda C++, HELIOS uses the GPU’s potential of massive parallelization and is able to compute the TP-profile of an atmosphere in radiative equilibrium and the subsequent emission spectrum in a few minutes on a single computer (for 60 layers and 1000 wavelength bins).The required molecular opacities are obtained with the recently published code HELIOS-K [1], which calculates the line shapes from an input line list and resamples the numerous line-by-line data into a manageable k-distribution format. Based on simple equilibrium chemistry theory [2] we combine the k-distribution functions of the molecules H2O, CO2, CO & CH4 to generate a k-table, which we then employ in HELIOS.I present our results of the following: (i) Various numerical tests, e.g. isothermal vs. non-isothermal treatment of layers. (ii) Comparison of iteratively determined TP-profiles with their analytical parametric prescriptions [3] and of the corresponding spectra. (iii) Benchmarks of TP-profiles & spectra for various elemental abundances. (iv) Benchmarks of averaged TP-profiles & spectra for the exoplanets GJ1214b, HD189733b & HD209458b. (v) Comparison with secondary eclipse data for HD189733b, XO-1b & Corot-2b.HELIOS is being developed, together with the dynamical core THOR and the chemistry solver VULCAN, in the group of Kevin Heng at the University of Bern as part of the Exoclimes Simulation Platform (ESP) [4], which is an open-source project aimed to provide community tools to model exoplanetary atmospheres.-----------------------------[1] Grimm & Heng 2015, ArXiv, 1503.03806[2] Heng, Lyons & Tsai, Arxiv, 1506.05501Heng & Lyons, ArXiv, 1507.01944[3] e.g. Heng, Mendonca & Lee, 2014, ApJS, 215, 4H[4] exoclime.net

3D Cloud Radiative Effects on Polarized Reflectances

NASA Astrophysics Data System (ADS)

Cornet, C.; Matar, C.; C-Labonnote, L.; Szczap, F.; Waquet, F.; Parol, F.; Riedi, J.

2017-12-01

As recognized in the last IPCC report, clouds have a major importance in the climate budget and need to be better characterized. Remote sensing observations are a way to obtain either global observations of cloud from satellites or a very fine description of clouds from airborne measurements. An increasing numbers of radiometers plan to measure polarized reflectances in addition to total reflectances, since this information is very helpful to obtain aerosol or cloud properties. In a near future, for example, the Multi-viewing, Multi-channel, Multi-polarization Imager (3MI) will be part the EPS-SG Eumetsat-ESA mission. It will achieve multi-angular polarimetric measurements from visible to shortwave infrared wavelengths. An airborne prototype, OSIRIS (Observing System Including Polarization in the Solar Infrared Spectrum), is also presently developed at the Laboratoire d'Optique Atmospherique and had already participated to several measurements campaigns. In order to analyze suitably the measured signal, it it necessary to have realistic and accurate models able to simulate polarized reflectances. The 3DCLOUD model (Szczap et al., 2014) was used to generate three-dimensional synthetic cloud and the 3D radiative transfer model, 3DMCPOL (Cornet et al., 2010) to compute realistic polarized reflectances. From these simulations, we investigate the effects of 3D cloud structures and heterogeneity on the polarized angular signature often used to retrieve cloud or aerosol properties. We show that 3D effects are weak for flat clouds but become quite significant for fractional clouds above ocean. The 3D effects are quite different according to the observation scale. For the airborne scale (few tens of meter), solar illumination effects can lead to polarized cloud reflectance values higher than the saturation limit predicted by the homogeneous cloud assumption. In the cloud gaps, corresponding to shadowed areas of the total reflectances, polarized signal can also be enhanced by the molecular signal at the shortest wavelength. At the satellite scale (few kilometers), depending on the wavelength and the molecular contribution, the absolute polarized signal may be increased or decreased in the forward scattering direction and is decreased in the cloudbow directions because of the plan-parallel biases.

Multi-directional radiation detector using photographic film

NASA Astrophysics Data System (ADS)

Junet, L. K.; Majid, Z. A. Abdul; Sapuan, A. H.; Sayed, I. S.; Pauzi, N. F.

2014-11-01

Ionising radiation has always been part of our surrounding and people are continuously exposed to it. Ionising radiation is harmful to human health, thus it is vital to monitor the radiation. To monitor radiation, there are three main points that should be observed cautiously, which are energy, quantity, and direction of the radiation sources. A three dimensional (3D) dosimeter is an example of a radiation detector that provide these three main points. This dosimeter is able to record the radiation dose distribution in 3D. Applying the concept of dose detection distribution, study has been done to design a multi-directional radiation detector of different filter thicknesses. This is obtained by designing a cylinder shaped aluminum filter with several layers of different thickness. Black and white photographic material is used as a radiation-sensitive material and a PVC material has been used as the enclosure. The device is then exposed to a radiation source with different exposure factors. For exposure factor 70 kVp, 16 mAs; the results have shown that optical density (OD) value at 135° is 1.86 higher compared with an OD value at 315° which is 0.71 as the 135° area received more radiation compare to 315° region. Furthermore, with an evidence of different angle of film give different value of OD shows that this device has a multidirectional ability. Materials used to develop this device are widely available in the market, thus reducing the cost of development and making it suitable for commercialisation.

A Subjective Assessment of Alternative Mission Architecture Operations Concepts for the Human Exploration of Mars at NASA Using a Three-Dimensional Multi-Criteria Decision Making Model

NASA Technical Reports Server (NTRS)

Tavana, Madjid

2003-01-01

The primary driver for developing missions to send humans to other planets is to generate significant scientific return. NASA plans human planetary explorations with an acceptable level of risk consistent with other manned operations. Space exploration risks can not be completely eliminated. Therefore, an acceptable level of cost, technical, safety, schedule, and political risks and benefits must be established for exploratory missions. This study uses a three-dimensional multi-criteria decision making model to identify the risks and benefits associated with three alternative mission architecture operations concepts for the human exploration of Mars identified by the Mission Operations Directorate at Johnson Space Center. The three alternatives considered in this study include split, combo lander, and dual scenarios. The model considers the seven phases of the mission including: 1) Earth Vicinity/Departure; 2) Mars Transfer; 3) Mars Arrival; 4) Planetary Surface; 5) Mars Vicinity/Departure; 6) Earth Transfer; and 7) Earth Arrival. Analytic Hierarchy Process (AHP) and subjective probability estimation are used to captures the experts belief concerning the risks and benefits of the three alternative scenarios through a series of sequential, rational, and analytical processes.

Dusty Cloud Acceleration by Radiation Pressure in Rapidly Star-forming Galaxies

NASA Astrophysics Data System (ADS)

Zhang, Dong; Davis, Shane W.; Jiang, Yan-Fei; Stone, James M.

2018-02-01

We perform two-dimensional and three-dimensional radiation hydrodynamic simulations to study cold clouds accelerated by radiation pressure on dust in the environment of rapidly star-forming galaxies dominated by infrared flux. We utilize the reduced speed of light approximation to solve the frequency-averaged, time-dependent radiative transfer equation. We find that radiation pressure is capable of accelerating the clouds to hundreds of kilometers per second while remaining dense and cold, consistent with observations. We compare these results to simulations where acceleration is provided by entrainment in a hot wind, where the momentum injection of the hot flow is comparable to the momentum in the radiation field. We find that the survival time of the cloud accelerated by the radiation field is significantly longer than that of a cloud entrained in a hot outflow. We show that the dynamics of the irradiated cloud depends on the initial optical depth, temperature of the cloud, and intensity of the flux. Additionally, gas pressure from the background may limit cloud acceleration if the density ratio between the cloud and background is ≲ {10}2. In general, a 10 pc-scale optically thin cloud forms a pancake structure elongated perpendicular to the direction of motion, while optically thick clouds form a filamentary structure elongated parallel to the direction of motion. The details of accelerated cloud morphology and geometry can also be affected by other factors, such as the cloud lengthscale, reduced speed of light approximation, spatial resolution, initial cloud structure, and dimensionality of the run, but these have relatively little affect on the cloud velocity or survival time.

The Intercomparison of 3D Radiation Codes (I3RC): Showcasing Mathematical and Computational Physics in a Critical Atmospheric Application

NASA Astrophysics Data System (ADS)

Davis, A. B.; Cahalan, R. F.

2001-05-01

The Intercomparison of 3D Radiation Codes (I3RC) is an on-going initiative involving an international group of over 30 researchers engaged in the numerical modeling of three-dimensional radiative transfer as applied to clouds. Because of their strong variability and extreme opacity, clouds are indeed a major source of uncertainty in the Earth's local radiation budget (at GCM grid scales). Also 3D effects (at satellite pixel scales) invalidate the standard plane-parallel assumption made in the routine of cloud-property remote sensing at NASA and NOAA. Accordingly, the test-cases used in I3RC are based on inputs and outputs which relate to cloud effects in atmospheric heating rates and in real-world remote sensing geometries. The main objectives of I3RC are to (1) enable participants to improve their models, (2) publish results as a community, (3) archive source code, and (4) educate. We will survey the status of I3RC and its plans for the near future with a special emphasis on the mathematical models and computational approaches. We will also describe some of the prime applications of I3RC's efforts in climate models, cloud-resolving models, and remote-sensing observations of clouds, or that of the surface in their presence. In all these application areas, computational efficiency is the main concern and not accuracy. One of I3RC's main goals is to document the performance of as wide a variety as possible of three-dimensional radiative transfer models for a small but representative number of ``cases.'' However, it is dominated by modelers working at the level of linear transport theory (i.e., they solve the radiative transfer equation) and an overwhelming majority of these participants use slow-but-robust Monte Carlo techniques. This means that only a small portion of the efficiency vs. accuracy vs. flexibility domain is currently populated by I3RC participants. To balance this natural clustering the present authors have organized a systematic outreach towards modelers that have used approximate methods in radiation transport. In this context, different, presumably simpler, equations (such as diffusion) are used in order to make a significant gain on the efficiency axis. We will describe in some detail the most promising approaches to approximate 3D radiative transfer in clouds. Somewhat paradoxically, and in spite of its importance in the above-mentioned applications, approximate radiative transfer modeling lags significantly behind its exact counterpart because the required mathematical and computational culture is essentially alien to the native atmospheric radiation community. I3RC is receiving enough funding from NASA/HQ and DOE/ARM for its essential operations out of NASA/GSFC. However, this does not cover the time and effort of any of the participants; so only existing models were entered. At present, none of inherently approximate methods are represented, only severe truncations of some exact methods. We therefore welcome the Math/Geo initiative at NSF which should enable the proper consortia of experts in atmospheric radiation and in applied mathematics to fill an important niche.

Three- and two-dimensional simulations of counter-propagating shear experiments at high energy densities at the National Ignition Facility

DOE PAGES

Wang, Ping; Zhou, Ye; MacLaren, Stephan A.; ...

2015-11-06

Three- and two-dimensional numerical studies have been carried out to simulate recent counter-propagating shear flow experiments on the National Ignition Facility. A multi-physics three-dimensional, time-dependent radiation hydrodynamics simulation code is used. Using a Reynolds Averaging Navier-Stokes model, we show that the evolution of the mixing layer width obtained from the simulations agrees well with that measured from the experiments. A sensitivity study is conducted to illustrate a 3D geometrical effect that could confuse the measurement at late times, if the energy drives from the two ends of the shock tube are asymmetric. Implications for future experiments are discussed.

Modeling the Atmosphere of Solar and Other Stars: Radiative Transfer with PHOENIX/3D

NASA Astrophysics Data System (ADS)

Baron, Edward

The chemical composition of stars is an important ingredient in our understanding of the formation, structure, and evolution of both the Galaxy and the Solar System. The composition of the sun itself is an essential reference standard against which the elemental contents of other astronomical objects are compared. Recently, redetermination of the elemental abundances using three-dimensional, time-dependent hydrodynamical models of the solar atmosphere has led to a reduction in the inferred metal abundances, particularly C, N, O, and Ne. However, this reduction in metals reduces the opacity such that models of the Sun no longer agree with the observed results obtained using helioseismology. Three dimensional (3-D) radiative transfer is an important problem in physics, astrophysics, and meteorology. Radiative transfer is extremely computationally complex and it is a natural problem that requires computation on the exascale. We intend to calculate the detailed compositional structure of the Sun and other stars at high resolution with full NLTE, treating the turbulent velocity flows in full detail in order to compare results from hydrodynamics and helioseismology, and understand the nature of the discrepancies found between the two approaches. We propose to perform 3-D high-resolution radiative transfer calculations with the PHOENIX/3D suite of solar and other stars using 3-D hydrodynamic models from different groups. While NLTE radiative transfer has been treated by the groups doing hydrodynamics, they are necessarily limited in their resolution to the consideration of only a few (4-20) frequency bins, whereas we can calculate full NLTE including thousands of wavelength points, resolving the line profiles, and solving the scattering problem with extremely high angular resolution. The code has been used for the analysis of supernova spectra, stellar and planetary spectra, and for time-dependent modeling of transient objects. PHOENIX/3D runs and scales very well on Cray XC-30 and XC-40 machines (tested up to 100,800 CPU cores) and should scale up to several million cores for large simulations. Non-local problems, particularly radiation hydrodynamics problems, are at the forefront of computational astrophysics and we will share our work with the community. Our research program brings a unified modeling strategy to the results of several disparate groups and thus will provide a unifying framework with which to assess the metal abundance of the stars and the chemical evolution of the galaxy. We will bring together 3-D hydrodynamical models, detailed radiative transfer, and astronomical abundance studies. We will also provide results of interest to the atomic physics and plasma physics communities. Our work will use data from NASA telescopes including the Hubble Space Telescope and the James Webb Space telescope. The ability to work with data from the UV to the far IR is crucial from validating our results. Our work will also extend the exascale computational capabilities, which is a national goal.

Overview of 3D-TRACE, a NASA Initiative in Three-Dimensional Tomography of the Aerosol-Cloud Environment

NASA Astrophysics Data System (ADS)

Davis, Anthony; Diner, David; Yanovsky, Igor; Garay, Michael; Xu, Feng; Bal, Guillaume; Schechner, Yoav; Aides, Amit; Qu, Zheng; Emde, Claudia

2013-04-01

Remote sensing is a key tool for sorting cloud ensembles by dynamical state, aerosol environments by source region, and establishing causal relationships between aerosol amounts, type, and cloud microphysics-the so-called indirect aerosol climate impacts, and one of the main sources of uncertainty in current climate models. Current satellite imagers use data processing approaches that invariably start with cloud detection/masking to isolate aerosol air-masses from clouds, and then rely on one-dimensional (1D) radiative transfer (RT) to interpret the aerosol and cloud measurements in isolation. Not only does this lead to well-documented biases for the estimates of aerosol radiative forcing and cloud optical depths in current missions, but it is fundamentally inadequate for future missions such as EarthCARE where capturing the complex, three-dimensional (3D) interactions between clouds and aerosols is a primary objective. In order to advance the state of the art, the next generation of satellite information processing systems must incorporate technologies that will enable the treatment of the atmosphere as a fully 3D environment, represented more realistically as a continuum. At one end, there is an optically thin background dominated by aerosols and molecular scattering that is strongly stratified and relatively homogeneous in the horizontal. At the other end, there are optically thick embedded elements, clouds and aerosol plumes, which can be more or less uniform and quasi-planar or else highly 3D with boundaries in all directions; in both cases, strong internal variability may be present. To make this paradigm shift possible, we propose to combine the standard models for satellite signal prediction physically grounded in 1D and 3D RT, both scalar and vector, with technologies adapted from biomedical imaging, digital image processing, and computer vision. This will enable us to demonstrate how the 3D distribution of atmospheric constituents, and their associated microphysical properties, can be reconstructed from multi-angle/multi-spectral imaging radiometry and, more and more, polarimetry. Specific technologies of interest are computed tomography (reconstruction from projections), optical tomography (using cross-pixel radiation transport in the diffusion limit), stereoscopy (depth/height retrievals), blind source and scale separation (signal unmixing), and disocclusion (information recovery in the presence of obstructions). Later on, these potentially powerful inverse problem solutions will be fully integrated in a versatile satellite data analysis toolbox. At present, we can report substantial progress at the component level. Specifically, we will focus on the most elementary problems in atmospheric tomography with an emphasis on the vastly under-exploited class of multi-pixel techniques. One basic problem is to infer the outer shape and mean opacity of 3D clouds, along with a bulk measure of cloud particle size. Another is to separate high and low cloud layers based on their characteristically different spatial textures. Yet another is to reconstruct the 3D spatial distribution of aerosol density based on passive imaging. This suite of independent feasibility studies amounts to a compelling proofof- concept for the ambitious 3D-Tomographic Reconstruction of the Aerosol-Cloud Environment (3D-TRACE) project as a whole.

The application of the principles of invariance to the radiative transfer equation in plant canopies

NASA Technical Reports Server (NTRS)

Ganapol, B. D.; Myneni, R. B.

1992-01-01

Solutions of the radiative transfer equation describing photon interactions with vegetation canopies are important in remote sensing since they provide the canopy reflectance distribution required in the interpretation of satellite acquired information. The general one-dimensional two-angle transport problem for a finite copy of arbitrary leaf angle distribution is considered. Analytical solutions are obtained in terms of generalized Chandrasekhar's X- and Y-functions by invoking the principles of invariance. A critical step in the formulation involves the decomposition of the integral of the scattering phase function into a product of known functions of the incident and scattered photon directions. Several simplified cases previously considered in the literature are derived from the generalized solution. Various symmetries obeyed by the scattering operator and reciprocity relations are formally proved.

Application of satellite data in variational analysis for global cyclonic systems

NASA Technical Reports Server (NTRS)

Achtemeier, G. L.

1988-01-01

The goal of the research is a variational data assimilation method that incorporates as dynamical constraints, the primitive equations for a moist, convectively unstable atmosphere and the radiative transfer equation. Variables to be adjusted include the three-dimensional vector wind, height, temperature, and moisture from rawinsonde data, and cloud-wind vectors, moisture, and radiance from satellite data. In order to facilitate thorough analysis of each of the model components, four variational models that divide the problem naturally according to increasing complexity were defined. The research performed during the second year fall into four areas: sensitivity studies involving Model 1; evaluation of Model 2; reformation of Model 1 for greater compatibility with Model 2; development of Model 3 (radiative transfer equation); and making the model more responsive to the observations.

Casimir effect and radiative heat transfer between Chern Insulators

NASA Astrophysics Data System (ADS)

Rodriguez Lopez, Pablo; Grushin, Adolfo; Tse, Wang-Kong; Dalvit, Diego

2015-03-01

Chern Insulators are a class of two-dimensional topological materials. Their electronic properties are different from conventional materials, and lead to interesting new physics as quantum Hall effect in absence of an external magnetic field. Here we will review some of their special properties and, in particular, we will discuss the radiative heat transfer and the Casimir effect between two planar Chern Insulators sheets. Finally, we will see how to control the intensity and sign of this Casimir force and the requirements to observe a repulsive Casimir force in the lab with those materials. The research leading to these results has received funding from the People Programme (Marie Curie Actions) of the European Union's Seventh Framework Programme (FP7/2007-2013) under REA Grant Agreement No. 302005.

Numerical simulations of electromagnetic scattering by Solar system objects

NASA Astrophysics Data System (ADS)

Dlugach, Janna M.

2016-11-01

Having been profoundly stimulated by the seminal work of Viktor V. Sobolev, I have been involved in multi-decadal research in the fields of radiative transfer, electromagnetic scattering by morphologically complex particles and particulate media, and planetary remote sensing. Much of this research has been done in close collaboration with other "descendants" of Academician Sobolev. This tutorial paper gives a representative overview of the results of extensive numerical simulations (in the vast majority carried out in collaboration with Michael Mishchenko) used to analyze remote-sensing observations of Solar system objects and based on highly accurate methods of the radiative transfer theory and direct computer solvers of the Maxwell equations. Using the atmosphere of Jupiter as a proving ground and performing T-matrix and radiative-transfer calculations helps demonstrate the strong effect of aerosol-particle shapes on the accuracy of remote-sensing retrievals. I then discuss the application of the T-matrix method, a numerically exact solution of the vector radiative transfer equation, and the theory of coherent backscattering to an analysis of polarimetric radar observations of Saturn's rings. Numerical modeling performed by using the superposition T-matrix method in application to cometary dust in the form of aggregates serves to reproduce the results of polarimetric observations of the distant comet C/2010 S1. On the basis of direct computer solutions of the Maxwell equations, it is demonstrated that all backscattering effects predicted by the low-density theories of radiative transfer and coherent backscattering can also be identified for media with volume packing densities typically encountered in natural and artificial environments. This result implies that spectacular opposition effects observed for some high-albedo atmoshereless Solar system bodies can be attributed to coherent backscattering of sunlight by regolith layers composed of microscopic particles.

Impact of ejecta morphology and composition on the electromagnetic signatures of neutron star mergers

NASA Astrophysics Data System (ADS)

Wollaeger, Ryan T.; Korobkin, Oleg; Fontes, Christopher J.; Rosswog, Stephan K.; Even, Wesley P.; Fryer, Christopher L.; Sollerman, Jesper; Hungerford, Aimee L.; van Rossum, Daniel R.; Wollaber, Allan B.

2018-04-01

The electromagnetic transients accompanying compact binary mergers (γ-ray bursts, afterglows and 'macronovae') are crucial to pinpoint the sky location of gravitational wave sources. Macronovae are caused by the radioactivity from freshly synthesised heavy elements, e.g. from dynamic ejecta and various types of winds. We study macronova signatures by using multi-dimensional radiative transfer calculations. We employ the radiative transfer code SuperNu and state-of-the art LTE opacities for a few representative elements from the wind and dynamical ejecta (Cr, Pd, Se, Te, Br, Zr, Sm, Ce, Nd, U) to calculate synthetic light curves and spectra for a range of ejecta morphologies. The radioactive power of the resulting macronova is calculated with the detailed input of decay products. We assess the detection prospects for our most complex models, based on the portion of viewing angles that are sufficiently bright, at different cosmological redshifts (z). The brighter emission from the wind is unobscured by the lanthanides (or actinides) in some of the models, permitting non-zero detection probabilities for redshifts up to z = 0.07. We also find the nuclear mass model and the resulting radioactive heating rate are crucial for the detectability. While for the most pessimistic heating rate (from the FRDM model) no reasonable increase in the ejecta mass or velocity, or wind mass or velocity, can possibly make the light curves agree with the observed nIR excess after GRB130603B, a more optimistic heating rate (from the Duflo-Zuker model) leads to good agreement. We conclude that future reliable macronova observations would constrain nuclear heating rates, and consequently help constrain nuclear mass models.

HELIOS: An Open-source, GPU-accelerated Radiative Transfer Code for Self-consistent Exoplanetary Atmospheres

NASA Astrophysics Data System (ADS)

Malik, Matej; Grosheintz, Luc; Mendonça, João M.; Grimm, Simon L.; Lavie, Baptiste; Kitzmann, Daniel; Tsai, Shang-Min; Burrows, Adam; Kreidberg, Laura; Bedell, Megan; Bean, Jacob L.; Stevenson, Kevin B.; Heng, Kevin

2017-02-01

We present the open-source radiative transfer code named HELIOS, which is constructed for studying exoplanetary atmospheres. In its initial version, the model atmospheres of HELIOS are one-dimensional and plane-parallel, and the equation of radiative transfer is solved in the two-stream approximation with nonisotropic scattering. A small set of the main infrared absorbers is employed, computed with the opacity calculator HELIOS-K and combined using a correlated-k approximation. The molecular abundances originate from validated analytical formulae for equilibrium chemistry. We compare HELIOS with the work of Miller-Ricci & Fortney using a model of GJ 1214b, and perform several tests, where we find: model atmospheres with single-temperature layers struggle to converge to radiative equilibrium; k-distribution tables constructed with ≳ 0.01 cm-1 resolution in the opacity function (≲ {10}3 points per wavenumber bin) may result in errors ≳ 1%-10% in the synthetic spectra; and a diffusivity factor of 2 approximates well the exact radiative transfer solution in the limit of pure absorption. We construct “null-hypothesis” models (chemical equilibrium, radiative equilibrium, and solar elemental abundances) for six hot Jupiters. We find that the dayside emission spectra of HD 189733b and WASP-43b are consistent with the null hypothesis, while the latter consistently underpredicts the observed fluxes of WASP-8b, WASP-12b, WASP-14b, and WASP-33b. We demonstrate that our results are somewhat insensitive to the choice of stellar models (blackbody, Kurucz, or PHOENIX) and metallicity, but are strongly affected by higher carbon-to-oxygen ratios. The code is publicly available as part of the Exoclimes Simulation Platform (exoclime.net).

An Epoch of Reionization simulation pipeline based on BEARS

NASA Astrophysics Data System (ADS)

Krause, Fabian; Thomas, Rajat M.; Zaroubi, Saleem; Abdalla, Filipe B.

2018-10-01

The quest to unlock the mysteries of the Epoch of Reionization (EoR) is well poised with many experiments at diverse wavelengths beginning to gather data. Albeit these efforts, we are yet uncertain about the various factors that influence the EoR which include, the nature of the sources, their spectral characteristics (blackbody temperatures, power-law indices), clustering property, efficiency, duty cycle etc. Given these physical uncertainties that define the EoR, we need fast and efficient computational methods to model and analyze the data in order to provide confidence bounds on the parameters that influence the brightness temperature at 21-cm. Towards this goal we developed a pipeline that combines dark matter-only N-body simulations with exact 1-dimensional radiative transfer computations to approximate exact 3-dimensional radiative transfer. Because these simulations are about two to three orders of magnitude faster than the exact 3-dimensional methods, they can be used to explore the parameter space of the EoR systematically. A fast scheme like this pipeline could be incorporated into a Bayesian framework for parameter estimation. In this paper we detail the construction of the pipeline and describe how to use the software which is being made publicly available. We show the results of running the pipeline for four test cases of sources with various spectral energy distributions and compare their outputs using various statistics.

On the Formation of Massive Stars

NASA Technical Reports Server (NTRS)

Yorke, Harold W.; Sonnhalter, Cordula

2002-01-01

We calculate numerically the collapse of slowly rotating, nonmagnetic, massive molecular clumps of masses 30,60, and 120 Stellar Mass, which conceivably could lead to the formation of massive stars. Because radiative acceleration on dust grains plays a critical role in the clump's dynamical evolution, we have improved the module for continuum radiation transfer in an existing two-dimensional (axial symmetry assumed) radiation hydrodynamic code. In particular, rather than using "gray" dust opacities and "gray" radiation transfer, we calculate the dust's wavelength-dependent absorption and emission simultaneously with the radiation density at each wavelength and the equilibrium temperatures of three grain components: amorphous carbon particles. silicates, and " dirty ice " -coated silicates. Because our simulations cannot spatially resolve the innermost regions of the molecular clump, however, we cannot distinguish between the formation of a dense central cluster or a single massive object. Furthermore, we cannot exclude significant mass loss from the central object(s) that may interact with the inflow into the central grid cell. Thus, with our basic assumption that all material in the innermost grid cell accretes onto a single object. we are able to provide only an upper limit to the mass of stars that could possibly be formed. We introduce a semianalytical scheme for augmenting existing evolutionary tracks of pre-main-sequence protostars by including the effects of accretion. By considering an open outermost boundary, an arbitrary amount of material could, in principal, be accreted onto this central star. However, for the three cases considered (30, 60, and 120 Stellar Mass originally within the computation grid), radiation acceleration limited the final masses to 3 1.6, 33.6, and 42.9 Stellar Mass, respectively, for wavelength-dependent radiation transfer and to 19.1, 20.1, and 22.9 Stellar Mass. for the corresponding simulations with gray radiation transfer. Our calculations demonstrate that massive stars can in principle be formed via accretion through a disk. The accretion rate onto the central source increases rapidly after one initial free-fall time and decreases monotonically afterward. By enhancing the nonisotropic character of the radiation field, the accretion disk reduces the effects of radiative acceleration in the radial direction - a process we call the "flashlight effect." The flashlight effect is further amplified in our case by including the effects of frequency-dependent radiation transfer. We conclude with the warning that a careful treatment of radiation transfer is a mandatory requirement for realistic simulations of the formation of massive stars.

FESTR: Finite-Element Spectral Transfer of Radiation spectroscopic modeling and analysis code

DOE PAGES

Hakel, Peter

2016-10-01

Here we report on the development of a new spectral postprocessor of hydrodynamic simulations of hot, dense plasmas. Based on given time histories of one-, two-, and three-dimensional spatial distributions of materials, and their local temperature and density conditions, spectroscopically-resolved signals are computed. The effects of radiation emission and absorption by the plasma on the emergent spectra are simultaneously taken into account. This program can also be used independently of hydrodynamic calculations to analyze available experimental data with the goal of inferring plasma conditions.

Estimating regional evapotranspiration from remotely sensed data by surface energy balance models

NASA Technical Reports Server (NTRS)

Asrar, Ghassem; Kanemasu, Edward; Myneni, R. B.; Lapitan, R. L.; Harris, T. R.; Killeen, J. M.; Cooper, D. I.; Hwang, C.

1987-01-01

Spatial and temporal variations of surface radiative temperatures of the burned and unburned areas of the Konza tallgrass prairie were studied. The role of management practices, topographic conditions and the uncertainties associated with in situ or airborne surface temperature measurements were assessed. Evaluation of diurnal and seasonal spectral characteristics of the burned and unburned areas of the prairie was also made. This was accomplished based on the analysis of measured spectral reflectance of the grass canopies under field conditions, and modelling their spectral behavior using a one dimensional radiative transfer model.

FESTR: Finite-Element Spectral Transfer of Radiation spectroscopic modeling and analysis code

NASA Astrophysics Data System (ADS)

Hakel, Peter

2016-10-01

We report on the development of a new spectral postprocessor of hydrodynamic simulations of hot, dense plasmas. Based on given time histories of one-, two-, and three-dimensional spatial distributions of materials, and their local temperature and density conditions, spectroscopically-resolved signals are computed. The effects of radiation emission and absorption by the plasma on the emergent spectra are simultaneously taken into account. This program can also be used independently of hydrodynamic calculations to analyze available experimental data with the goal of inferring plasma conditions.

Internal Passage Heat Transfer Prediction Using Multiblock Grids and a Kappa-Omega Turbulence Model

NASA Technical Reports Server (NTRS)

Rigby, David L.; Ameri, Ali A.; Steinthorsson, Erlendur

1996-01-01

Numerical simulations of the three-dimensional flow and heat transfer in a rectangular duct with a 180 C bend were performed. Results are presented for Reynolds numbers of 17,000 and 37,000 and for aspect ratios of 0.5 and I.O. A kappa-omega turbulence model with no reference to distance to a wall is used. Direct comparison between single block and multiblock grid calculations are made. Heat transfer and velocity distributions are compared to available literature with good agreement. The multi-block grid system is seen to produce more accurate results compared to a single-block grid with the same number of cells.

Energy transfer simulation for radiantly heated and cooled enclosures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chapman, K.S.; Zhang, P.

1996-11-01

This paper presents the development of a three-dimensional mathematical model to compute heat transfer within a radiantly heated or cooled room, which then calculates the mass-averaged room air temperature and the wall surface temperature distributions. The radiation formulation used in the model accommodates arbitrary placement of walls and objects within the room. The convection model utilizes Nusselt number correlations published in the open literature. The complete energy transfer model is validated by comparing calculated room temperatures to temperatures measured in a radiantly heated room. This three-dimensional model may be applied to a building to assist the heating/cooling system design engineermore » in sizing a radiant heating/cooling system. By coupling this model with a thermal comfort model, the comfort levels throughout the room can be easily and efficiently mapped for a given radiant heater/cooler location. In addition, obstacles such as airplanes, trucks, furniture, and partitions can be easily incorporated to determine their effect on the radiant heating system performance.« less

Space radiator simulation system analysis

NASA Technical Reports Server (NTRS)

Black, W. Z.; Wulff, W.

1972-01-01

A transient heat transfer analysis was carried out on a space radiator heat rejection system exposed to an arbitrarily prescribed combination of aerodynamic heating, solar, albedo, and planetary radiation. A rigorous analysis was carried out for the radiation panel and tubes lying in one plane and an approximate analysis was used to extend the rigorous analysis to the case of a curved panel. The analysis permits the consideration of both gaseous and liquid coolant fluids, including liquid metals, under prescribed, time dependent inlet conditions. The analysis provided a method for predicting: (1) transient and steady-state, two dimensional temperature profiles, (2) local and total heat rejection rates, (3) coolant flow pressure in the flow channel, and (4) total system weight and protection layer thickness.

3D Radiative Transfer in Cloudy Atmospheres

NASA Astrophysics Data System (ADS)

Marshak, Alexander; Davis, Anthony

Developments in three-dimensional cloud radiation over the past few decades are assessed and distilled into this contributed volume. Chapters are authored by subject-matter experts who address a broad audience of graduate students, researchers, and anyone interested in cloud-radiation processes in the solar and infrared spectral regions. After two introductory chapters and a section on the fundamental physics and computational techniques, the volume extensively treats two main application areas: the impact of clouds on the Earth's radiation budget, which is an essential aspect of climate modeling; and remote observation of clouds, especially with the advanced sensors on current and future satellite missions. http://www.springeronline.com/alert/article?a=3D1_1fva7w_1j826l_41z_6

Influence of the Geometric Parameter on the Regimes of Natural Convection and Thermal Surface Radiation in a Closed Parallelepiped

NASA Astrophysics Data System (ADS)

Martyushev, S. G.; Miroshnichenko, I. V.; Sheremet, M. A.

2015-11-01

We have performed a numerical analysis of the stationary regimes of thermogravitational convection and thermal surface radiation in a closed differentially heated parallelepiped. The mathematical model formulated in dimensionless natural velocity-pressure-temperature variables was realized numerically in the control volume approach. Analysis of the radiative heat exchange was carried out on the basis of the surface radiation approach with the use of the balance method in the Polyak variant. We have obtained three-dimensional temperature and velocity fields, as well as dependences for the mean Nusselt number reflecting the influence of the geometric parameter, the Rayleigh number, and the reduced emissive factor of the walls on the flow structure and the heat transfer.

An iterative phase-space explicit discontinuous Galerkin method for stellar radiative transfer in extended atmospheres

DOE Office of Scientific and Technical Information (OSTI.GOV)

de Almeida, Valmor F.

In this work, a phase-space discontinuous Galerkin (PSDG) method is presented for the solution of stellar radiative transfer problems. It allows for greater adaptivity than competing methods without sacrificing generality. The method is extensively tested on a spherically symmetric, static, inverse-power-law scattering atmosphere. Results for different sizes of atmospheres and intensities of scattering agreed with asymptotic values. The exponentially decaying behavior of the radiative field in the diffusive-transparent transition region, and the forward peaking behavior at the surface of extended atmospheres were accurately captured. The integrodifferential equation of radiation transfer is solved iteratively by alternating between the radiative pressure equationmore » and the original equation with the integral term treated as an energy density source term. In each iteration, the equations are solved via an explicit, flux-conserving, discontinuous Galerkin method. Finite elements are ordered in wave fronts perpendicular to the characteristic curves so that elemental linear algebraic systems are solved quickly by sweeping the phase space element by element. Two implementations of a diffusive boundary condition at the origin are demonstrated wherein the finite discontinuity in the radiation intensity is accurately captured by the proposed method. This allows for a consistent mechanism to preserve photon luminosity. The method was proved to be robust and fast, and a case is made for the adequacy of parallel processing. In addition to classical two-dimensional plots, results of normalized radiation intensity were mapped onto a log-polar surface exhibiting all distinguishing features of the problem studied.« less

An iterative phase-space explicit discontinuous Galerkin method for stellar radiative transfer in extended atmospheres

DOE PAGES

de Almeida, Valmor F.

2017-04-19

In this work, a phase-space discontinuous Galerkin (PSDG) method is presented for the solution of stellar radiative transfer problems. It allows for greater adaptivity than competing methods without sacrificing generality. The method is extensively tested on a spherically symmetric, static, inverse-power-law scattering atmosphere. Results for different sizes of atmospheres and intensities of scattering agreed with asymptotic values. The exponentially decaying behavior of the radiative field in the diffusive-transparent transition region, and the forward peaking behavior at the surface of extended atmospheres were accurately captured. The integrodifferential equation of radiation transfer is solved iteratively by alternating between the radiative pressure equationmore » and the original equation with the integral term treated as an energy density source term. In each iteration, the equations are solved via an explicit, flux-conserving, discontinuous Galerkin method. Finite elements are ordered in wave fronts perpendicular to the characteristic curves so that elemental linear algebraic systems are solved quickly by sweeping the phase space element by element. Two implementations of a diffusive boundary condition at the origin are demonstrated wherein the finite discontinuity in the radiation intensity is accurately captured by the proposed method. This allows for a consistent mechanism to preserve photon luminosity. The method was proved to be robust and fast, and a case is made for the adequacy of parallel processing. In addition to classical two-dimensional plots, results of normalized radiation intensity were mapped onto a log-polar surface exhibiting all distinguishing features of the problem studied.« less

Numerical study of radiation effect on the municipal solid waste combustion characteristics inside an incinerator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Jingfu, E-mail: jfwang@bjut.edu.cn; Xue, Yanqing; Zhang, Xinxin

Highlights: • A 3-D model for the MSW incinerator with preheated air was developed. • Gas radiative properties were obtained from a statistical narrow-band model. • Non-gray body radiation model can provide more accurate simulation results. - Abstract: Due to its advantages of high degree volume reduction, relatively stable residue, and energy reclamation, incineration becomes one of the best choices for Municipal Solid Waste (MSW) disposal. However, detailed measurements of temperature and gas species inside a furnace are difficulty by conventional experimental techniques. Therefore, numerical simulation of MSW incineration in the packed bed and gas flow field was applied. Inmore » this work, a three dimensional (3-D) model of incinerator system, including flow, heat transfer, detailed chemical mechanisms, and non-gray gas models, was developed. Radiation from the furnace wall and the flame formed above the bed is of importance for drying and igniting the waste. The preheated air with high temperature is used for the MSW combustion. Under the conditions of high temperature and high pressure, MSW combustion produces a variety of radiating gases. The wavelength-depend radiative properties of flame adopted in non-gray radiation model were obtained from a statistical narrow-band model. The influence of radiative heat transfer on temperature, flow field is researched by adiabatic model (without considering radiation), gray radiation model, and non-gray radiation model. The simulation results show that taking into account the non-gray radiation is essential.« less

Global Precipitation Measurement, Validation, and Applications Integrated Hydrologic Validation to Improve Physical Precipitation Retrievals for GPM

NASA Technical Reports Server (NTRS)

Peters-Lidar, Christa D.; Tian, Yudong; Kenneth, Tian; Harrison, Kenneth; Kumar, Sujay

2011-01-01

Land surface modeling and data assimilation can provide dynamic land surface state variables necessary to support physical precipitation retrieval algorithms over land. It is well-known that surface emission, particularly over the range of frequencies to be included in the Global Precipitation Measurement Mission (GPM), is sensitive to land surface states, including soil properties, vegetation type and greenness, soil moisture, surface temperature, and snow cover, density, and grain size. In order to investigate the robustness of both the land surface model states and the microwave emissivity and forward radiative transfer models, we have undertaken a multi-site investigation as part of the NASA Precipitation Measurement Missions (PMM) Land Surface Characterization Working Group. Specifically, we will demonstrate the performance of the Land Information System (LIS; http://lis.gsfc.nasa.gov; Peters-Lidard et aI., 2007; Kumar et al., 2006) coupled to the Joint Center for Satellite Data Assimilation (JCSDA's) Community Radiative Transfer Model (CRTM; Weng, 2007; van Deist, 2009). The land surface is characterized by complex physical/chemical constituents and creates temporally and spatially heterogeneous surface properties in response to microwave radiation scattering. The uncertainties in surface microwave emission (both surface radiative temperature and emissivity) and very low polarization ratio are linked to difficulties in rainfall detection using low-frequency passive microwave sensors (e.g.,Kummerow et al. 2001). Therefore, addressing these issues is of utmost importance for the GPM mission. There are many approaches to parameterizing land surface emission and radiative transfer, some of which have been customized for snow (e.g., the Helsinki University of Technology or HUT radiative transfer model;) and soil moisture (e.g., the Land Surface Microwave Emission Model or LSMEM).

Long-term records of global radiation, carbon and water fluxes derived from multi-satellite data and a process-based model

NASA Astrophysics Data System (ADS)

Ryu, Youngryel; Jiang, Chongya

2016-04-01

To gain insights about the underlying impacts of global climate change on terrestrial ecosystem fluxes, we present a long-term (1982-2015) global radiation, carbon and water fluxes products by integrating multi-satellite data with a process-based model, the Breathing Earth System Simulator (BESS). BESS is a coupled processed model that integrates radiative transfer in the atmosphere and canopy, photosynthesis (GPP), and evapotranspiration (ET). BESS was designed most sensitive to the variables that can be quantified reliably, fully taking advantages of remote sensing atmospheric and land products. Originally, BESS entirely relied on MODIS as input variables to produce global GPP and ET during the MODIS era. This study extends the work to provide a series of long-term products from 1982 to 2015 by incorporating AVHRR data. In addition to GPP and ET, more land surface processes related datasets are mapped to facilitate the discovery of the ecological variations and changes. The CLARA-A1 cloud property datasets, the TOMS aerosol datasets, along with the GLASS land surface albedo datasets, were input to a look-up table derived from an atmospheric radiative transfer model to produce direct and diffuse components of visible and near infrared radiation datasets. Theses radiation components together with the LAI3g datasets and the GLASS land surface albedo datasets, were used to calculate absorbed radiation through a clumping corrected two-stream canopy radiative transfer model. ECMWF ERA interim air temperature data were downscaled by using ALP-II land surface temperature dataset and a region-dependent regression model. The spatial and seasonal variations of CO2 concentration were accounted by OCO-2 datasets, whereas NOAA's global CO2 growth rates data were used to describe interannual variations. All these remote sensing based datasets are used to run the BESS. Daily fluxes in 1/12 degree were computed and then aggregated to half-month interval to match with the spatial-temporal resolution of LAI3g dataset. The BESS GPP and ET products were compared to other independent datasets including MPI-BGC and CLM. Overall, the BESS products show good agreement with the other two datasets, indicating a compelling potential for bridging remote sensing and land surface models.

SIERRA Low Mach Module: Fuego User Manual Version 4.46.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sierra Thermal/Fluid Team

2017-09-01

The SIERRA Low Mach Module: Fuego along with the SIERRA Participating Media Radiation Module: Syrinx, henceforth referred to as Fuego and Syrinx, respectively, are the key elements of the ASCI fire environment simulation project. The fire environment simulation project is directed at characterizing both open large-scale pool fires and building enclosure fires. Fuego represents the turbulent, buoyantly-driven incompressible flow, heat transfer, mass transfer, combustion, soot, and absorption coefficient model portion of the simulation software. Syrinx represents the participating-media thermal radiation mechanics. This project is an integral part of the SIERRA multi-mechanics software development project. Fuego depends heavily upon the coremore » architecture developments provided by SIERRA for massively parallel computing, solution adaptivity, and mechanics coupling on unstructured grids.« less

SIERRA Low Mach Module: Fuego Theory Manual Version 4.44

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sierra Thermal /Fluid Team

2017-04-01

The SIERRA Low Mach Module: Fuego along with the SIERRA Participating Media Radiation Module: Syrinx, henceforth referred to as Fuego and Syrinx, respectively, are the key elements of the ASCI fire environment simulation project. The fire environment simulation project is directed at characterizing both open large-scale pool fires and building enclosure fires. Fuego represents the turbulent, buoyantly-driven incompressible flow, heat transfer, mass transfer, combustion, soot, and absorption coefficient model portion of the simulation software. Syrinx represents the participating-media thermal radiation mechanics. This project is an integral part of the SIERRA multi-mechanics software development project. Fuego depends heavily upon the coremore » architecture developments provided by SIERRA for massively parallel computing, solution adaptivity, and mechanics coupling on unstructured grids.« less

SIERRA Low Mach Module: Fuego Theory Manual Version 4.46.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sierra Thermal/Fluid Team

The SIERRA Low Mach Module: Fuego along with the SIERRA Participating Media Radiation Module: Syrinx, henceforth referred to as Fuego and Syrinx, respectively, are the key elements of the ASCI fire environment simulation project. The fire environment simulation project is directed at characterizing both open large-scale pool fires and building enclosure fires. Fuego represents the turbulent, buoyantly-driven incompressible flow, heat transfer, mass transfer, combustion, soot, and absorption coefficient model portion of the simulation software. Syrinx represents the participating-media thermal radiation mechanics. This project is an integral part of the SIERRA multi-mechanics software development project. Fuego depends heavily upon the coremore » architecture developments provided by SIERRA for massively parallel computing, solution adaptivity, and mechanics coupling on unstructured grids.« less

FORCE2: A state-of-the-art two-phase code for hydrodynamic calculations

NASA Astrophysics Data System (ADS)

Ding, Jianmin; Lyczkowski, R. W.; Burge, S. W.

1993-02-01

A three-dimensional computer code for two-phase flow named FORCE2 has been developed by Babcock and Wilcox (B & W) in close collaboration with Argonne National Laboratory (ANL). FORCE2 is capable of both transient as well as steady-state simulations. This Cartesian coordinates computer program is a finite control volume, industrial grade and quality embodiment of the pilot-scale FLUFIX/MOD2 code and contains features such as three-dimensional blockages, volume and surface porosities to account for various obstructions in the flow field, and distributed resistance modeling to account for pressure drops caused by baffles, distributor plates and large tube banks. Recently computed results demonstrated the significance of and necessity for three-dimensional models of hydrodynamics and erosion. This paper describes the process whereby ANL's pilot-scale FLUFIX/MOD2 models and numerics were implemented into FORCE2. A description of the quality control to assess the accuracy of the new code and the validation using some of the measured data from Illinois Institute of Technology (UT) and the University of Illinois at Urbana-Champaign (UIUC) are given. It is envisioned that one day, FORCE2 with additional modules such as radiation heat transfer, combustion kinetics and multi-solids together with user-friendly pre- and post-processor software and tailored for massively parallel multiprocessor shared memory computational platforms will be used by industry and researchers to assist in reducing and/or eliminating the environmental and economic barriers which limit full consideration of coal, shale and biomass as energy sources, to retain energy security, and to remediate waste and ecological problems.

TOPAZ2D heat transfer code users manual and thermal property data base

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shapiro, A.B.; Edwards, A.L.

1990-05-01

TOPAZ2D is a two dimensional implicit finite element computer code for heat transfer analysis. This user's manual provides information on the structure of a TOPAZ2D input file. Also included is a material thermal property data base. This manual is supplemented with The TOPAZ2D Theoretical Manual and the TOPAZ2D Verification Manual. TOPAZ2D has been implemented on the CRAY, SUN, and VAX computers. TOPAZ2D can be used to solve for the steady state or transient temperature field on two dimensional planar or axisymmetric geometries. Material properties may be temperature dependent and either isotropic or orthotropic. A variety of time and temperature dependentmore » boundary conditions can be specified including temperature, flux, convection, and radiation. Time or temperature dependent internal heat generation can be defined locally be element or globally by material. TOPAZ2D can solve problems of diffuse and specular band radiation in an enclosure coupled with conduction in material surrounding the enclosure. Additional features include thermally controlled reactive chemical mixtures, thermal contact resistance across an interface, bulk fluid flow, phase change, and energy balances. Thermal stresses can be calculated using the solid mechanics code NIKE2D which reads the temperature state data calculated by TOPAZ2D. A three dimensional version of the code, TOPAZ3D is available. The material thermal property data base, Chapter 4, included in this manual was originally published in 1969 by Art Edwards for use with his TRUMP finite difference heat transfer code. The format of the data has been altered to be compatible with TOPAZ2D. Bob Bailey is responsible for adding the high explosive thermal property data.« less

The Radiative Forcing Model Intercomparison Project (RFMIP): Assessment and characterization of forcing to enable feedback studies

NASA Astrophysics Data System (ADS)

Pincus, R.; Stevens, B. B.; Forster, P.; Collins, W.; Ramaswamy, V.

2014-12-01

The Radiative Forcing Model Intercomparison Project (RFMIP): Assessment and characterization of forcing to enable feedback studies An enormous amount of attention has been paid to the diversity of responses in the CMIP and other multi-model ensembles. This diversity is normally interpreted as a distribution in climate sensitivity driven by some distribution of feedback mechanisms. Identification of these feedbacks relies on precise identification of the forcing to which each model is subject, including distinguishing true error from model diversity. The Radiative Forcing Model Intercomparison Project (RFMIP) aims to disentangle the role of forcing from model sensitivity as determinants of varying climate model response by carefully characterizing the radiative forcing to which such models are subject and by coordinating experiments in which it is specified. RFMIP consists of four activities: 1) An assessment of accuracy in flux and forcing calculations for greenhouse gases under past, present, and future climates, using off-line radiative transfer calculations in specified atmospheres with climate model parameterizations and reference models 2) Characterization and assessment of model-specific historical forcing by anthropogenic aerosols, based on coordinated diagnostic output from climate models and off-line radiative transfer calculations with reference models 3) Characterization of model-specific effective radiative forcing, including contributions of model climatology and rapid adjustments, using coordinated climate model integrations and off-line radiative transfer calculations with a single fast model 4) Assessment of climate model response to precisely-characterized radiative forcing over the historical record, including efforts to infer true historical forcing from patterns of response, by direct specification of non-greenhouse-gas forcing in a series of coordinated climate model integrations This talk discusses the rationale for RFMIP, provides an overview of the four activities, and presents preliminary motivating results.

The Multi-Dimensional Structure of Radiative Shocks: Suppressed Thermal X-rays and Relativistic Ion Acceleration

NASA Astrophysics Data System (ADS)

Steinberg, Elad; Metzger, Brian D.

2018-06-01

Radiative shocks, behind which gas cools faster than the dynamical time, play a key role in many astrophysical transients, including classical novae and young supernovae interacting with circumstellar material. The dense layer behind high Mach number M ≫ 1 radiative shocks is susceptible to thin-shell instabilities, creating a "corrugated" shock interface. We present two and three-dimensional hydrodynamical simulations of optically-thin radiative shocks to study their thermal radiation and acceleration of non-thermal relativistic ions. We employ a moving-mesh code and a specialized numerical technique to eliminate artificial heat conduction across grid cells. The fraction of the shock's luminosity Ltot radiated at X-ray temperatures kT_sh ≈ (3/16)μ m_p v_sh2 expected from a one-dimensional analysis is suppressed by a factor L(>T_sh/3)/L_tot ≈ 4.5/M^{4/3} for M ≈ 4-36. This suppression results in part from weak shocks driven into under-pressured cold filaments by hot shocked gas, which sap thermal energy from the latter faster than it is radiated. Combining particle-in-cell simulation results for diffusive shock acceleration with the inclination angle distribution across the shock (relative to an upstream magnetic field in the shock plane-the expected geometry for transient outflows), we predict the efficiency and energy spectrum of ion acceleration. Though negligible acceleration is predicted for adiabatic shocks, the corrugated shock front enables local regions to satisfy the quasi-parallel magnetic field geometry required for efficient acceleration, resulting in an average acceleration efficiency of ɛnth ˜ 0.005 - 0.02 for M ≈ 12-36, in agreement with modeling of the gamma-ray nova ASASSN-16ma.

The In Vitro Response of Tissue Stem Cells to Irradiation With Different Linear Energy Transfers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nagle, Peter W.; Hosper, Nynke A.; Department of Radiation Oncology, University of Groningen, University Medical Center Groningen, Groningen

Purpose: A reduction in the dose, irradiated volume, and sensitivity of, in particular, normal tissue stem cells is needed to advance radiation therapy. This could be obtained with the use of particles for radiation therapy. However, the radiation response of normal tissue stem cells is still an enigma. Therefore, in the present study, we developed a model to investigate the in vitro response of stem cells to particle irradiation. Methods and Materials: We used the immortalized human salivary gland (HSG) cell line resembling salivary gland (SG) cells to translate the radiation response in 2-dimensional (2D) to 3-dimensional (3D) conditions. This responsemore » was subsequently translated to the response of SG stem cells (SGSCs). Dispersed single cells were irradiated with photons or carbon ions at different linear energy transfers (LETs; 48.76 ± 2.16, 149.9 ± 10.8, and 189 ± 15 keV/μm). Subsequently, 2D or 3D clonogenicity was determined by counting the colonies or secondary stem cell-derived spheres in Matrigel. γH2AX immunostaining was used to assess DNA double strand break repair. Results: The 2D response of HSG cells showed a similar increase in dose response to increasing higher LET irradiation as other cell lines. The 3D response of HSG cells to increasing LET irradiation was reduced compared with the 2D response. Finally, the response of mouse SGSCs to photons was similar to the 3D response of HSG cells. The response to higher LET irradiation was reduced in the stem cells. Conclusions: Mouse SGSC radiosensitivity seems reduced at higher LET radiation compared with transformed HSG cells. The developed model to assess the radiation response of SGSCs offers novel possibilities to study the radiation response of normal tissue in vitro.« less

Recent advances in non-LTE stellar atmosphere models

NASA Astrophysics Data System (ADS)

Sander, Andreas A. C.

2017-11-01

In the last decades, stellar atmosphere models have become a key tool in understanding massive stars. Applied for spectroscopic analysis, these models provide quantitative information on stellar wind properties as well as fundamental stellar parameters. The intricate non-LTE conditions in stellar winds dictate the development of adequate sophisticated model atmosphere codes. The increase in both, the computational power and our understanding of physical processes in stellar atmospheres, led to an increasing complexity in the models. As a result, codes emerged that can tackle a wide range of stellar and wind parameters. After a brief address of the fundamentals of stellar atmosphere modeling, the current stage of clumped and line-blanketed model atmospheres will be discussed. Finally, the path for the next generation of stellar atmosphere models will be outlined. Apart from discussing multi-dimensional approaches, I will emphasize on the coupling of hydrodynamics with a sophisticated treatment of the radiative transfer. This next generation of models will be able to predict wind parameters from first principles, which could open new doors for our understanding of the various facets of massive star physics, evolution, and death.

Numerical study for melting heat transfer and homogeneous-heterogeneous reactions in flow involving carbon nanotubes

NASA Astrophysics Data System (ADS)

Hayat, Tasawar; Muhammad, Khursheed; Alsaedi, Ahmed; Asghar, Saleem

2018-03-01

Present work concentrates on melting heat transfer in three-dimensional flow of nanofluid over an impermeable stretchable surface. Analysis is made in presence of porous medium and homogeneous-heterogeneous reactions. Single and multi-wall CNTs (carbon nanotubes) are considered. Water is chosen as basefluid. Adequate transformations yield the non-linear ordinary differential systems. Solution of emerging problems is obtained using shooting method. Impacts of influential variables on velocity and temperature are discussed graphically. Skin friction coefficient and Nusselt number are numerically discussed. The results for MWCNTs and SWCNTs are compared and examined.

Textile composite processing science

NASA Technical Reports Server (NTRS)

Loos, Alfred C.; Hammond, Vincent H.; Kranbuehl, David E.; Hasko, Gregory H.

1993-01-01

A multi-dimensional model of the Resin Transfer Molding (RTM) process was developed for the prediction of the infiltration behavior of a resin into an anisotropic fiber preform. Frequency dependent electromagnetic sensing (FDEMS) was developed for in-situ monitoring of the RTM process. Flow visualization and mold filling experiments were conducted to verify sensor measurements and model predictions. Test results indicated good agreement between model predictions, sensor readings, and experimental data.

On the attenuation of sound by three-dimensionally segmented acoustic liners in a rectangular duct

NASA Technical Reports Server (NTRS)

Koch, W.

1979-01-01

Axial segmentation of acoustically absorbing liners in rectangular, circular or annual duct configurations is a very useful concept for obtaining higher noise attenuation with respect to the bandwidth of absorption as well as the maximum attenuation. As a consequence, advanced liner concepts are proposed which induce a modal energy transfer in both cross-sectional directions to further reduce the noise radiated from turbofan engines. However, these advanced liner concepts require three-dimensional geometries which are difficult to treat theoretically. A very simple three-dimensional problem is investigated analytically. The results show a strong dependence on the positioning of the liner for some incident source modes while the effect of three-dimensional segmentation appears to be negligible over the frequency range considered.

Computational attributes of the integral form of the equation of transfer

NASA Technical Reports Server (NTRS)

Frankel, J. I.

1991-01-01

Difficulties can arise in radiative and neutron transport calculations when a highly anisotropic scattering phase function is present. In the presence of anisotropy, currently used numerical solutions are based on the integro-differential form of the linearized Boltzmann transport equation. This paper, departs from classical thought and presents an alternative numerical approach based on application of the integral form of the transport equation. Use of the integral formalism facilitates the following steps: a reduction in dimensionality of the system prior to discretization, the use of symbolic manipulation to augment the computational procedure, and the direct determination of key physical quantities which are derivable through the various Legendre moments of the intensity. The approach is developed in the context of radiative heat transfer in a plane-parallel geometry, and results are presented and compared with existing benchmark solutions. Encouraging results are presented to illustrate the potential of the integral formalism for computation. The integral formalism appears to possess several computational attributes which are well-suited to radiative and neutron transport calculations.

Radiative transfer and radiative driving of outflows in active galactic nuclei and starbursts

NASA Astrophysics Data System (ADS)

Novak, G. S.; Ostriker, J. P.; Ciotti, L.

2012-12-01

To facilitate the study of black hole fuelling, star formation and feedback in galaxies, we outline a method for treating the radial forces on interstellar gas due to absorption of photons by dust grains. The method gives the correct behaviour in all of the relevant limits [dominated by the central point source; dominated by the distributed isotropic source; optically thin; optically thick to ultraviolet (UV)/optical; optically thick to infrared (IR)] and reasonably interpolates between the limits when necessary. The method is explicitly energy conserving so that UV/optical photons that are absorbed are not lost, but are rather redistributed to the IR where they may scatter out of the galaxy. We implement the radiative transfer algorithm in a two-dimensional hydrodynamical code designed to study feedback processes in the context of early-type galaxies. We find that the dynamics and final state of simulations are measurably but only moderately affected by radiative forces on dust, even when assumptions about the dust-to-gas ratio are varied from zero to a value appropriate for the Milky Way. In simulations with high gas densities designed to mimic ultraluminous IR galaxies with a star formation rate of several hundred solar masses per year, dust makes a more substantial contribution to the dynamics and outcome of the simulation. We find that, despite the large opacity of dust to UV radiation, the momentum input to the flow from radiation very rarely exceeds L/c due to two factors: the low opacity of dust to the re-radiated IR and the tendency for dust to be destroyed by sputtering in hot gas environments. We also develop a simplification of our radiative transfer algorithm that respects the essential physics but is much easier to implement and requires a fraction of the computational cost.

Chebyshev collocation spectral method for one-dimensional radiative heat transfer in linearly anisotropic-scattering cylindrical medium

NASA Astrophysics Data System (ADS)

Zhou, Rui-Rui; Li, Ben-Wen

2017-03-01

In this study, the Chebyshev collocation spectral method (CCSM) is developed to solve the radiative integro-differential transfer equation (RIDTE) for one-dimensional absorbing, emitting and linearly anisotropic-scattering cylindrical medium. The general form of quadrature formulas for Chebyshev collocation points is deduced. These formulas are proved to have the same accuracy as the Gauss-Legendre quadrature formula (GLQF) for the F-function (geometric function) in the RIDTE. The explicit expressions of the Lagrange basis polynomials and the differentiation matrices for Chebyshev collocation points are also given. These expressions are necessary for solving an integro-differential equation by the CCSM. Since the integrand in the RIDTE is continuous but non-smooth, it is treated by the segments integration method (SIM). The derivative terms in the RIDTE are carried out to improve the accuracy near the origin. In this way, a fourth order accuracy is achieved by the CCSM for the RIDTE, whereas it's only a second order one by the finite difference method (FDM). Several benchmark problems (BPs) with various combinations of optical thickness, medium temperature distribution, degree of anisotropy, and scattering albedo are solved. The results show that present CCSM is efficient to obtain high accurate results, especially for the optically thin medium. The solutions rounded to seven significant digits are given in tabular form, and show excellent agreement with the published data. Finally, the solutions of RIDTE are used as benchmarks for the solution of radiative integral transfer equations (RITEs) presented by Sutton and Chen (JQSRT 84 (2004) 65-103). A non-uniform grid refined near the wall is advised to improve the accuracy of RITEs solutions.

The Development of Layered Photonic Band Gap Structures Using a Micro-Transfer Molding Technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sutherland, Kevin Jerome

Photonic band gap (PBG) crystals are periodic dielectric structures that manipulate electromagnetic radiation in a manner similar to semiconductor devices manipulating electrons. Whereas a semiconductor material exhibits an electronic band gap in which electrons cannot exist, similarly, a photonic crystal containing a photonic band gap does not allow the propagation of specific frequencies of electromagnetic radiation. This phenomenon results from the destructive Bragg diffraction interference that a wave propagating at a specific frequency will experience because of the periodic change in dielectric permitivity. This gives rise to a variety of optical applications for improving the efficiency and effectiveness of opto-electronicmore » devices. These applications are reviewed later. Several methods are currently used to fabricate photonic crystals, which are also discussed in detail. This research involves a layer-by-layer micro-transfer molding ({mu}TM) and stacking method to create three-dimensional FCC structures of epoxy or titania. The structures, once reduced significantly in size can be infiltrated with an organic gain media and stacked on a semiconductor to improve the efficiency of an electronically pumped light-emitting diode. Photonic band gap structures have been proven to effectively create a band gap for certain frequencies of electro-magnetic radiation in the microwave and near-infrared ranges. The objective of this research project was originally two-fold: to fabricate a three dimensional (3-D) structure of a size scaled to prohibit electromagnetic propagation within the visible wavelength range, and then to characterize that structure using laser dye emission spectra. As a master mold has not yet been developed for the micro transfer molding technique in the visible range, the research was limited to scaling down the length scale as much as possible with the current available technology and characterizing these structures with other methods.« less

The Effect of Cumulus Cloud Field Anisotropy on Domain-Averaged Solar Fluxes and Atmospheric Heating Rates

NASA Technical Reports Server (NTRS)

Hinkelman, Laura M.; Evans, K. Franklin; Clothiaux, Eugene E.; Ackerman, Thomas P.; Stackhouse, Paul W., Jr.

2006-01-01

Cumulus clouds can become tilted or elongated in the presence of wind shear. Nevertheless, most studies of the interaction of cumulus clouds and radiation have assumed these clouds to be isotropic. This paper describes an investigation of the effect of fair-weather cumulus cloud field anisotropy on domain-averaged solar fluxes and atmospheric heating rate profiles. A stochastic field generation algorithm was used to produce twenty three-dimensional liquid water content fields based on the statistical properties of cloud scenes from a large eddy simulation. Progressively greater degrees of x-z plane tilting and horizontal stretching were imposed on each of these scenes, so that an ensemble of scenes was produced for each level of distortion. The resulting scenes were used as input to a three-dimensional Monte Carlo radiative transfer model. Domain-average transmission, reflection, and absorption of broadband solar radiation were computed for each scene along with the average heating rate profile. Both tilt and horizontal stretching were found to significantly affect calculated fluxes, with the amount and sign of flux differences depending strongly on sun position relative to cloud distortion geometry. The mechanisms by which anisotropy interacts with solar fluxes were investigated by comparisons to independent pixel approximation and tilted independent pixel approximation computations for the same scenes. Cumulus anisotropy was found to most strongly impact solar radiative transfer by changing the effective cloud fraction, i.e., the cloud fraction when the field is projected on a surface perpendicular to the direction of the incident solar beam.

Landslide Failure Likelihoods Estimated Through Analysis of Suspended Sediment and Streamflow Time Series Data

NASA Astrophysics Data System (ADS)

Stark, C. P.; Rudd, S.; Lall, U.; Hovius, N.; Dadson, S.; Chen, M.-C.

Off-Axis DOAS measurements with non-artificial scattered light, based upon the renowned DOAS technique, allow to optimize the sensitivity of the technique for the trace gas profile in question by strongly increasing the light's path through the relevant atmosphere layers. Multi-Axis-(MAX) DOAS probe several directions simultaneously or sequentially to increase the spatial resolution. Several devices (ground based, air- borne and ship-built) are operated by our group in the framework of the SCIAMACHY validation. Radiative transfer models are an essential requirement for the interpretation of these measurements and their conversion into detailed profile data. Apart from some existing Monte Carlo Models most codes use analytical algorithms to solve the radia- tive transfer equation for given atmospheric conditions. For specific circumstances, e.g. photon scattering within clouds, these approaches are not efficient enough to pro- vide sufficient accuracy. Also horizontal gradients in atmospheric parameters have to be taken into account. To meet the needs of measurement situations for all kinds of scattered light DOAS platforms, a three dimensional full spherical Monte Carlo model was devised. Here we present Air Mass Factors (AMF) to calculate vertical column densities (VCD) from measured slant column densities (SCD). Sensitivity studies on the influence of the wavelength and telescope direction used, of the altitude of profile layers, albedo, refraction and basic aerosols are shown. Also modelled intensity series are compared with radiometer data.

Radiation from advanced solid rocket motor plumes

NASA Technical Reports Server (NTRS)

Farmer, Richard C.; Smith, Sheldon D.; Myruski, Brian L.

1994-01-01

The overall objective of this study was to develop an understanding of solid rocket motor (SRM) plumes in sufficient detail to accurately explain the majority of plume radiation test data. Improved flowfield and radiation analysis codes were developed to accurately and efficiently account for all the factors which effect radiation heating from rocket plumes. These codes were verified by comparing predicted plume behavior with measured NASA/MSFC ASRM test data. Upon conducting a thorough review of the current state-of-the-art of SRM plume flowfield and radiation prediction methodology and the pertinent data base, the following analyses were developed for future design use. The NOZZRAD code was developed for preliminary base heating design and Al2O3 particle optical property data evaluation using a generalized two-flux solution to the radiative transfer equation. The IDARAD code was developed for rapid evaluation of plume radiation effects using the spherical harmonics method of differential approximation to the radiative transfer equation. The FDNS CFD code with fully coupled Euler-Lagrange particle tracking was validated by comparison to predictions made with the industry standard RAMP code for SRM nozzle flowfield analysis. The FDNS code provides the ability to analyze not only rocket nozzle flow, but also axisymmetric and three-dimensional plume flowfields with state-of-the-art CFD methodology. Procedures for conducting meaningful thermo-vision camera studies were developed.

The Geometry of the Stellar Winds and Shock Structure in V444 Cyg

NASA Astrophysics Data System (ADS)

Hoffman, Jennifer

Given the importance of mass loss in the evolution of massive stars, it is imperative that we improve our understanding of the processes by which the outer layers of a star may be lost to its environment. The eclipsing nature of the Wolf-Rayet binary star V444 Cyg provides us with a unique opportunity to study the detailed characteristics of the radiatively driven mass loss in colliding-wind systems. Our multi-technique study combines X-ray spectroscopic and optical spectropolarimetric methods to describe the three-dimensional nature of the shock and wind structure in V444 Cyg. In support of this project, we have won new X-ray observations of V444 Cyg using the XMM-Newton telescope through the Guest Observer program in AO-11 (proposal ID #069281). We will combine these new data with six archival XMM-Newton observations and with optical spectropolarimetry obtained with the newly refurbished Half-Wave Spectropolarimeter (HPOL) at Ritter Observatory in Toledo, OH and archival data from both HPOL and the ESPaDOnS instrument at CFHT. Detailed X-ray light curve analysis and modeling of the X-ray spectra will constrain the location of the wind collision region and the mass-loss properties of the system. Polarized light curves in optical broad bands and emission lines combined with spectropolarimetric line profile analysis and radiative transfer simulations will trace the geometrical structure of various emission and scattering regions within the winds. Joint analysis of these two data sets will allow us to construct a self-consistent, physically realistic three-dimensional model of the complex winds in V444 Cyg and quantify its mass loss characteristics. We request support for data analysis and interpretation of our four new XMM-Newton observations. This will consist primarily of salaries for program personnel, who will analyze the new data in conjunction with previous X-ray results, carry out detailed radiation-hydrodynamic simulations to investigate the effect of radiative braking and other complex effects on the X-ray characteristics of V444 Cyg, and construct a new three-dimensional model of the system incorporating information from both X-ray and spectropolarimetric studies. We also request travel funding to enable collaboration among co-investigators at different institutions and to professional meetings to publicize results, as well as nominal support for the complementary ground-based spectropolarimetric observations (this amount comprises < 25% of the total, in accordance with NASA ADAP program limitations).

Multi-dimensional coherent optical spectroscopy of semiconductor nanostructures: Collinear and non-collinear approaches

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nardin, Gaël; Li, Hebin; Autry, Travis M.

2015-03-21

We review our recent work on multi-dimensional coherent optical spectroscopy (MDCS) of semiconductor nanostructures. Two approaches, appropriate for the study of semiconductor materials, are presented and compared. A first method is based on a non-collinear geometry, where the Four-Wave-Mixing (FWM) signal is detected in the form of a radiated optical field. This approach works for samples with translational symmetry, such as Quantum Wells (QWs) or large and dense ensembles of Quantum Dots (QDs). A second method detects the FWM in the form of a photocurrent in a collinear geometry. This second approach extends the horizon of MDCS to sub-diffraction nanostructures,more » such as single QDs, nanowires, or nanotubes, and small ensembles thereof. Examples of experimental results obtained on semiconductor QW structures are given for each method. In particular, it is shown how MDCS can assess coupling between excitons confined in separated QWs.« less

Numerical study of Free Convective Viscous Dissipative flow along Vertical Cone with Influence of Radiation using Network Simulation method

NASA Astrophysics Data System (ADS)

Kannan, R. M.; Pullepu, Bapuji; Immanuel, Y.

2018-04-01

A two dimensional mathematical model is formulated for the transient laminar free convective flow with heat transfer over an incompressible viscous fluid past a vertical cone with uniform surface heat flux with combined effects of viscous dissipation and radiation. The dimensionless boundary layer equations of the flow which are transient, coupled and nonlinear Partial differential equations are solved using the Network Simulation Method (NSM), a powerful numerical technique which demonstrates high efficiency and accuracy by employing the network simulator computer code Pspice. The velocity and temperature profiles have been investigated for various factors, namely viscous dissipation parameter ε, Prandtl number Pr and radiation Rd are analyzed graphically.

Wave-Particle Interactions in the Earth's Radiation Belts: Recent Advances and Unprecedented Future Opportunities

NASA Astrophysics Data System (ADS)

Li, W.

2017-12-01

In the collisionless heliospheric plasmas, wave-particle interaction is a fundamental physical process in transferring energy and momentum between particles with different species and energies. This presentation focuses on one of the important wave-particle interaction processes: interaction between whistler-mode waves and electrons. Whistler-mode waves have frequencies between proton and electron cyclotron frequency and are ubiquitously present in the heliospheric plasmas including solar wind and planetary magnetospheres. I use Earth's Van Allen radiation belt as "local space laboratory" to discuss the role of whistler-mode waves in energetic electron dynamics using multi-satellite observations, theory and modeling. I further discuss solar wind drivers leading to energetic electron dynamics in the Earth's radiation belts, which is critical in predicting space weather that has broad impacts on our technological systems and society. At last, I discuss the unprecedented future opportunities of exploring space science using multi-satellite observations and state-of-the-art theory and modeling.

A Radiation Transfer Solver for Athena Using Short Characteristics

NASA Astrophysics Data System (ADS)

Davis, Shane W.; Stone, James M.; Jiang, Yan-Fei

2012-03-01

We describe the implementation of a module for the Athena magnetohydrodynamics (MHD) code that solves the time-independent, multi-frequency radiative transfer (RT) equation on multidimensional Cartesian simulation domains, including scattering and non-local thermodynamic equilibrium (LTE) effects. The module is based on well known and well tested algorithms developed for modeling stellar atmospheres, including the method of short characteristics to solve the RT equation, accelerated Lambda iteration to handle scattering and non-LTE effects, and parallelization via domain decomposition. The module serves several purposes: it can be used to generate spectra and images, to compute a variable Eddington tensor (VET) for full radiation MHD simulations, and to calculate the heating and cooling source terms in the MHD equations in flows where radiation pressure is small compared with gas pressure. For the latter case, the module is combined with the standard MHD integrators using operator splitting: we describe this approach in detail, including a new constraint on the time step for stability due to radiation diffusion modes. Implementation of the VET method for radiation pressure dominated flows is described in a companion paper. We present results from a suite of test problems for both the RT solver itself and for dynamical problems that include radiative heating and cooling. These tests demonstrate that the radiative transfer solution is accurate and confirm that the operator split method is stable, convergent, and efficient for problems of interest. We demonstrate there is no need to adopt ad hoc assumptions of questionable accuracy to solve RT problems in concert with MHD: the computational cost for our general-purpose module for simple (e.g., LTE gray) problems can be comparable to or less than a single time step of Athena's MHD integrators, and only few times more expensive than that for more general (non-LTE) problems.

Preliminary skyshine calculations for the Poloidal Diverter Tokamak Experiment

NASA Astrophysics Data System (ADS)

Nigg, D. W.; Wheeler, F. J.

1981-01-01

A calculational model is presented to estimate the radiation dose, due to the skyshine effect, in the control room and at the site boundary of the Poloidal Diverter Experiment (PDX) facility at Princeton University which requires substantial radiation shielding. The required composition and thickness of a water-filled roof shield that would reduce this effect to an acceptable level is computed, using an efficient one-dimensional model with an Sn calculation in slab geometry. The actual neutron skyshine dose is computed using a Monte Carlo model with the neutron source at the roof surface obtained from the slab Sn calculation, and the capture gamma dose is computed using a simple point-kernel single-scatter method. It is maintained that the slab model provides the exact probability of leakage out the top surface of the roof and that it is nearly as accurate as and much less costly than multi-dimensional techniques.

Preliminary skyshine calculations for the Poloidal Diverter Tokamak Experiment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nigg, D.W.; Wheeler, F.J.

1981-01-01

A calculational model is presented to estimate the radiation dose, due to the skyshine effect, in the control room and at the site boundary of the Poloidal Diverter Experiment (PDX) facility at Princeton University which requires substantial radiation shielding. The required composition and thickness of a water-filled roof shield that would reduce this effect to an acceptable level is computed, using an efficient one-dimensional model with an Sn calculation in slab geometry. The actual neutron skyshine dose is computed using a Monte Carlo model with the neutron source at the roof surface obtained from the slab Sn calculation, and themore » capture gamma dose is computed using a simple point-kernel single-scatter method. It is maintained that the slab model provides the exact probability of leakage out the top surface of the roof and that it is nearly as accurate as and much less costly than multi-dimensional techniques.« less

Innovative procedure for computer-assisted genioplasty: three-dimensional cephalometry, rapid-prototyping model and surgical splint.

PubMed

Olszewski, R; Tranduy, K; Reychler, H

2010-07-01

The authors present a new procedure of computer-assisted genioplasty. They determined the anterior, posterior and inferior limits of the chin in relation to the skull and face with the newly developed and validated three-dimensional cephalometric planar analysis (ACRO 3D). Virtual planning of the osteotomy lines was carried out with Mimics (Materialize) software. The authors built a three-dimensional rapid-prototyping multi-position model of the chin area from a medical low-dose CT scan. The transfer of virtual information to the operating room consisted of two elements. First, the titanium plates on the 3D RP model were pre-bent. Second, a surgical guide for the transfer of the osteotomy lines and the positions of the screws to the operating room was manufactured. The authors present the first case of the use of this model on a patient. The postoperative results are promising, and the technique is fast and easy-to-use. More patients are needed for a definitive clinical validation of this procedure. Copyright 2010 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.

The Effect of Carbon Dioxide (CO 2) Ice Cloud Condensation on the Habitable Zone

NASA Astrophysics Data System (ADS)

Lincowski, Andrew; Meadows, Victoria; Robinson, Tyler D.; Crisp, David

2016-10-01

The currently accepted outer limit of the habitable zone (OHZ) is defined by the "maximum greenhouse" limit, where Rayleigh scattering from additional CO2 gas overwhelms greenhouse warming. However, this long-standing definition neglects the radiative effects of CO2 clouds (Kopparapu, 2013); this omission was justified based on studies using the two-stream approximation, which found CO2 clouds to be highly likely to produce a net warming. However, recent comparisons of the radiative effect of CO2 clouds using both a two-stream and multi-stream radiative transfer model (Kitzmann et al, 2013; Kitzmann, 2016) found that the warming effect was reduced when the more sophisticated multi-stream models were used. In many cases CO2 clouds caused a cooling effect, meaning that their impact on climate could not be neglected when calculating the outer edge of the habitable zone. To better understand the impact of CO2 ice clouds on the OHZ, we have integrated CO2 cloud condensation into a versatile 1-D climate model for terrestrial planets (Robinson et al, 2012) that uses the validated multi-stream SMART radiative transfer code (Meadows & Crisp, 1996; Crisp, 1997) with a simple microphysical model. We present preliminary results on the habitable zone with self-consistent CO2 clouds for a range of atmospheric masses, compositions and host star spectra, and the subsequent effect on surface temperature. In particular, we evaluate the habitable zone for TRAPPIST-1d (Gillon et al, 2016) with a variety of atmospheric compositions and masses. We present reflectance and transit spectra of these cold terrestrial planets. We identify any consequences for the OHZ in general and TRAPPIST-1d in particular. This more comprehensive treatment of the OHZ could impact our understanding of the distribution of habitable planets in the universe, and provide better constraints for statistical target selection techniques, such as the habitability index (Barnes et al, 2015), for missions like JWST, WFIRST-AFTA and the LUVOIR mission concept.

Stochastic weighted particle methods for population balance equations with coagulation, fragmentation and spatial inhomogeneity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Kok Foong; Patterson, Robert I.A.; Wagner, Wolfgang

2015-12-15

Graphical abstract: -- Highlights: •Problems concerning multi-compartment population balance equations are studied. •A class of fragmentation weight transfer functions is presented. •Three stochastic weighted algorithms are compared against the direct simulation algorithm. •The numerical errors of the stochastic solutions are assessed as a function of fragmentation rate. •The algorithms are applied to a multi-dimensional granulation model. -- Abstract: This paper introduces stochastic weighted particle algorithms for the solution of multi-compartment population balance equations. In particular, it presents a class of fragmentation weight transfer functions which are constructed such that the number of computational particles stays constant during fragmentation events. Themore » weight transfer functions are constructed based on systems of weighted computational particles and each of it leads to a stochastic particle algorithm for the numerical treatment of population balance equations. Besides fragmentation, the algorithms also consider physical processes such as coagulation and the exchange of mass with the surroundings. The numerical properties of the algorithms are compared to the direct simulation algorithm and an existing method for the fragmentation of weighted particles. It is found that the new algorithms show better numerical performance over the two existing methods especially for systems with significant amount of large particles and high fragmentation rates.« less

Modelling of Titan's middle atmosphere with the IPSL climate model

NASA Astrophysics Data System (ADS)

Vatant d'Ollone, Jan; Lebonnois, Sébastien; Guerlet, Sandrine

2017-04-01

Titan's 3-dimensional Global Climate Model developed at the Institute Pierre-Simon Laplace has already demonstrated its efficiency to reproduce and interpret many features of the Saturnian moon's climate (e.g. Lebonnois et al., 2012). However, it suffered from limits at the top of the model, with temperatures far warmer than the observations and no stratopause simulated. To interpret Cassini's overall observations of seasonal effects in the middle atmosphere (e.g. Vinatier et al., 2015), a satisfying modelling of the temperature profile in this region was first required. Latest developments in the GCM now enable a correct modelling of the temperature profile in the middle atmosphere. In particular, a new, more flexible, radiative transfer scheme based on correlated-k method has been set up, using up-to-date spectroscopic data. Special emphasis is put on the too warm upper stratospheric temperatures in the former model that were due to the absence of the infrared ν4 methane line (7.7 μm) in the radiative transfer. While it was usually neglected in the tropospheric radiative models, this line has a strong cooling effect in Titan's stratospheric conditions and cannot be neglected. In this new version of the GCM, the microphysical model is temporarily switched off and we use a mean profile for haze opacity (Lavvas et al., 2010). The circulation in the middle atmosphere is significantly improved by this new radiative transfer. The new 3-D simulations also show an interesting feature in the modeled vertical profile of the zonal wind as the minimum in low stratosphere is now closer to the observations. Works in progress such as the vertical extension and the computation of the radiative effect of the seasonal variations of trace components will also be presented. - Lavvas P. et al., 2010. Titan's vertical aerosol structure at the Huygens landing site: Constraints on particle size, density, charge, and refractive index. Icarus 210, 832-842. - Lebonnois S. et al., 2012. Titan Global Climate Model: new 3-dimensional version of the IPSL Titan GCM. Icarus 218, 707-722. - Vinatier S. et al., 2015. Seasonal variations in Titan's middle atmosphere during the northern spring derived from Cassini/CIRS observations. Icarus 250, 95-115.

Some New Results in Astrophysical Problems of Nonlinear Theory of Radiative Transfer

NASA Astrophysics Data System (ADS)

Pikichyan, H. V.

2017-07-01

In the interpretation of the observed astrophysical spectra, a decisive role is related to nonlinear problems of radiative transfer, because the processes of multiple interactions of matter of cosmic medium with the exciting intense radiation ubiquitously occur in astrophysical objects, and in their vicinities. Whereas, the intensity of the exciting radiation changes the physical properties of the original medium, and itself was modified, simultaneously, in a self-consistent manner under its influence. In the present report, we show that the consistent application of the principle of invariance in the nonlinear problem of bilateral external illumination of a scattering/absorbing one-dimensional anisotropic medium of finite geometrical thickness allows for simplifications that were previously considered as a prerogative only of linear problems. The nonlinear problem is analyzed through the three methods of the principle of invariance: (i) an adding of layers, (ii) its limiting form, described by differential equations of invariant imbedding, and (iii) a transition to the, so-called, functional equations of the "Ambartsumyan's complete invariance". Thereby, as an alternative to the Boltzmann equation, a new type of equations, so-called "kinetic equations of equivalence", are obtained. By the introduction of new functions - the so-called "linear images" of solution of nonlinear problem of radiative transfer, the linear structure of the solution of the nonlinear problem under study is further revealed. Linear images allow to convert naturally the statistical characteristics of random walk of a "single quantum" or their "beam of unit intensity", as well as widely known "probabilistic interpretation of phenomena of transfer", to the field of nonlinear problems. The structure of the equations obtained for determination of linear images is typical of linear problems.

Two-dimensional vocal tracts with three-dimensional behavior in the numerical generation of vowels.

PubMed

Arnela, Marc; Guasch, Oriol

2014-01-01

Two-dimensional (2D) numerical simulations of vocal tract acoustics may provide a good balance between the high quality of three-dimensional (3D) finite element approaches and the low computational cost of one-dimensional (1D) techniques. However, 2D models are usually generated by considering the 2D vocal tract as a midsagittal cut of a 3D version, i.e., using the same radius function, wall impedance, glottal flow, and radiation losses as in 3D, which leads to strong discrepancies in the resulting vocal tract transfer functions. In this work, a four step methodology is proposed to match the behavior of 2D simulations with that of 3D vocal tracts with circular cross-sections. First, the 2D vocal tract profile becomes modified to tune the formant locations. Second, the 2D wall impedance is adjusted to fit the formant bandwidths. Third, the 2D glottal flow gets scaled to recover 3D pressure levels. Fourth and last, the 2D radiation model is tuned to match the 3D model following an optimization process. The procedure is tested for vowels /a/, /i/, and /u/ and the obtained results are compared with those of a full 3D simulation, a conventional 2D approach, and a 1D chain matrix model.

Accelerated solution of discrete ordinates approximation to the Boltzmann transport equation via model reduction

DOE PAGES

Tencer, John; Carlberg, Kevin; Larsen, Marvin; ...

2017-06-17

Radiation heat transfer is an important phenomenon in many physical systems of practical interest. When participating media is important, the radiative transfer equation (RTE) must be solved for the radiative intensity as a function of location, time, direction, and wavelength. In many heat-transfer applications, a quasi-steady assumption is valid, thereby removing time dependence. The dependence on wavelength is often treated through a weighted sum of gray gases (WSGG) approach. The discrete ordinates method (DOM) is one of the most common methods for approximating the angular (i.e., directional) dependence. The DOM exactly solves for the radiative intensity for a finite numbermore » of discrete ordinate directions and computes approximations to integrals over the angular space using a quadrature rule; the chosen ordinate directions correspond to the nodes of this quadrature rule. This paper applies a projection-based model-reduction approach to make high-order quadrature computationally feasible for the DOM for purely absorbing applications. First, the proposed approach constructs a reduced basis from (high-fidelity) solutions of the radiative intensity computed at a relatively small number of ordinate directions. Then, the method computes inexpensive approximations of the radiative intensity at the (remaining) quadrature points of a high-order quadrature using a reduced-order model constructed from the reduced basis. Finally, this results in a much more accurate solution than might have been achieved using only the ordinate directions used to compute the reduced basis. One- and three-dimensional test problems highlight the efficiency of the proposed method.« less

Accelerated solution of discrete ordinates approximation to the Boltzmann transport equation via model reduction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tencer, John; Carlberg, Kevin; Larsen, Marvin

Radiation heat transfer is an important phenomenon in many physical systems of practical interest. When participating media is important, the radiative transfer equation (RTE) must be solved for the radiative intensity as a function of location, time, direction, and wavelength. In many heat-transfer applications, a quasi-steady assumption is valid, thereby removing time dependence. The dependence on wavelength is often treated through a weighted sum of gray gases (WSGG) approach. The discrete ordinates method (DOM) is one of the most common methods for approximating the angular (i.e., directional) dependence. The DOM exactly solves for the radiative intensity for a finite numbermore » of discrete ordinate directions and computes approximations to integrals over the angular space using a quadrature rule; the chosen ordinate directions correspond to the nodes of this quadrature rule. This paper applies a projection-based model-reduction approach to make high-order quadrature computationally feasible for the DOM for purely absorbing applications. First, the proposed approach constructs a reduced basis from (high-fidelity) solutions of the radiative intensity computed at a relatively small number of ordinate directions. Then, the method computes inexpensive approximations of the radiative intensity at the (remaining) quadrature points of a high-order quadrature using a reduced-order model constructed from the reduced basis. Finally, this results in a much more accurate solution than might have been achieved using only the ordinate directions used to compute the reduced basis. One- and three-dimensional test problems highlight the efficiency of the proposed method.« less

Optical Radiation from Integer Quantum Hall States in Dirac Materials

NASA Astrophysics Data System (ADS)

Gullans, Michael; Taylor, Jacob; Ghaemi, Pouyan; Hafezi, Mohammad

Quantum Hall systems exhibit topologically protected edge states, which can have a macroscopic spatial extent. Such edge states provide a unique opportunity to study a quantum emitter whose size far exceeds the wavelength of emitted light. To better understand this limit, we theoretically characterize the optical radiation from integer quantum Hall states in two-dimensional Dirac materials. We show that the scattered light from the bulk reflects the spatial profile of the wavefunctions, enabling spatial imaging of the disorder landscape. We find that the radiation from the edge states are characterized by the presence of large multipole moments in the far-field. This multipole radiation arises from the transfer of angular momentum from the electrons into the scattered light, enabling the generation of coherent light with high orbital angular momentum.

MHD Forced Convective Laminar Boundary Layer Flow from a Convectively Heated Moving Vertical Plate with Radiation and Transpiration Effect

PubMed Central

Uddin, Md. Jashim; Khan, Waqar A.; Ismail, A. I. Md.

2013-01-01

A two-dimensional steady forced convective flow of a Newtonian fluid past a convectively heated permeable vertically moving plate in the presence of a variable magnetic field and radiation effect has been investigated numerically. The plate moves either in assisting or opposing direction to the free stream. The plate and free stream velocities are considered to be proportional to whilst the magnetic field and mass transfer velocity are taken to be proportional to where is the distance along the plate from the leading edge of the plate. Instead of using existing similarity transformations, we use a linear group of transformations to transform the governing equations into similarity equations with relevant boundary conditions. Numerical solutions of the similarity equations are presented to show the effects of the controlling parameters on the dimensionless velocity, temperature and concentration profiles as well as on the friction factor, rate of heat and mass transfer. It is found that the rate of heat transfer elevates with the mass transfer velocity, convective heat transfer, Prandtl number, velocity ratio and the magnetic field parameters. It is also found that the rate of mass transfer enhances with the mass transfer velocity, velocity ratio, power law index and the Schmidt number, whilst it suppresses with the magnetic field parameter. Our results are compared with the results existing in the open literature. The comparisons are satisfactory. PMID:23741295

Real-time electroholography using a multiple-graphics processing unit cluster system with a single spatial light modulator and the InfiniBand network

NASA Astrophysics Data System (ADS)

Niwase, Hiroaki; Takada, Naoki; Araki, Hiromitsu; Maeda, Yuki; Fujiwara, Masato; Nakayama, Hirotaka; Kakue, Takashi; Shimobaba, Tomoyoshi; Ito, Tomoyoshi

2016-09-01

Parallel calculations of large-pixel-count computer-generated holograms (CGHs) are suitable for multiple-graphics processing unit (multi-GPU) cluster systems. However, it is not easy for a multi-GPU cluster system to accomplish fast CGH calculations when CGH transfers between PCs are required. In these cases, the CGH transfer between the PCs becomes a bottleneck. Usually, this problem occurs only in multi-GPU cluster systems with a single spatial light modulator. To overcome this problem, we propose a simple method using the InfiniBand network. The computational speed of the proposed method using 13 GPUs (NVIDIA GeForce GTX TITAN X) was more than 3000 times faster than that of a CPU (Intel Core i7 4770) when the number of three-dimensional (3-D) object points exceeded 20,480. In practice, we achieved ˜40 tera floating point operations per second (TFLOPS) when the number of 3-D object points exceeded 40,960. Our proposed method was able to reconstruct a real-time movie of a 3-D object comprising 95,949 points.

F--Ray: A new algorithm for efficient transport of ionizing radiation

NASA Astrophysics Data System (ADS)

Mao, Yi; Zhang, J.; Wandelt, B. D.; Shapiro, P. R.; Iliev, I. T.

2014-04-01

We present a new algorithm for the 3D transport of ionizing radiation, called F2-Ray (Fast Fourier Ray-tracing method). The transfer of ionizing radiation with long mean free path in diffuse intergalactic gas poses a special challenge to standard numerical methods which transport the radiation in position space. Standard methods usually trace each individual ray until it is fully absorbed by the intervening gas. If the mean free path is long, the computational cost and memory load are likely to be prohibitive. We have developed an algorithm that overcomes these limitations and is, therefore, significantly more efficient. The method calculates the transfer of radiation collectively, using the Fast Fourier Transform to convert radiation between position and Fourier spaces, so the computational cost will not increase with the number of ionizing sources. The method also automatically combines parallel rays with the same frequency at the same grid cell, thereby minimizing the memory requirement. The method is explicitly photon-conserving, i.e. the depletion of ionizing photons is guaranteed to equal the photoionizations they caused, and explicitly obeys the periodic boundary condition, i.e. the escape of ionizing photons from one side of a simulation volume is guaranteed to be compensated by emitting the same amount of photons into the volume through the opposite side. Together, these features make it possible to numerically simulate the transfer of ionizing photons more efficiently than previous methods. Since ionizing radiation such as the X-ray is responsible for heating the intergalactic gas when first stars and quasars form at high redshifts, our method can be applied to simulate thermal distribution, in addition to cosmic reionization, in three-dimensional inhomogeneous cosmological density field.

Heat Transfer on a Film-Cooled Blade - Effect of Hole Physics

NASA Technical Reports Server (NTRS)

Garg, Vijay K.; Rigby, David L.

1998-01-01

A multi-block, three-dimensional Navier-Stokes code has been used to study the within-hole and near-hole physics in relation to heat transfer on a film-cooled blade. The flow domain consists of the coolant flow through the plenum and hole-pipes for the three staggered rows of shower-head holes on the VK1 rotor, and the main flow over the blade. A multi-block grid is generated that is nearly orthogonal to the various surfaces. It may be noted that for the VK1 rotor the shower-head holes are inclined at 30 deg. to the spanwise direction, and are normal to the streamwise direction on the blade. Wilcox's k-omega turbulence model is used. The present study provides a much better comparison for the heat transfer coefficient at the blade mid-span with the experimental data than an earlier analysis wherein coolant velocity and temperature distributions were specified at the hole exits rather than extending the computational domain into the hole-pipe and plenum. Details of the distributions of coolant velocity, temperature, k and omega at the hole exits are also presented.

DirtyGrid I: 3D Dust Radiative Transfer Modeling of Spectral Energy Distributions of Dusty Stellar Populations

NASA Astrophysics Data System (ADS)

Law, Ka-Hei; Gordon, Karl D.; Misselt, Karl A.

2018-06-01

Understanding the properties of stellar populations and interstellar dust has important implications for galaxy evolution. In normal star-forming galaxies, stars and the interstellar medium dominate the radiation from ultraviolet (UV) to infrared (IR). In particular, interstellar dust absorbs and scatters UV and optical light, re-emitting the absorbed energy in the IR. This is a strongly nonlinear process that makes independent studies of the UV-optical and IR susceptible to large uncertainties and degeneracies. Over the years, UV to IR spectral energy distribution (SED) fitting utilizing varying approximations has revealed important results on the stellar and dust properties of galaxies. Yet the approximations limit the fidelity of the derived properties. There is sufficient computer power now available that it is now possible to remove these approximations and map out of landscape of galaxy SEDs using full dust radiative transfer. This improves upon previous work by directly connecting the UV, optical, and IR through dust grain physics. We present the DIRTYGrid, a grid of radiative transfer models of SEDs of dusty stellar populations in galactic environments designed to span the full range of physical parameters of galaxies. Using the stellar and gas radiation input from the stellar population synthesis model PEGASE, our radiative transfer model DIRTY self-consistently computes the UV to far-IR/sub-mm SEDs for each set of parameters in our grid. DIRTY computes the dust absorption, scattering, and emission from the local radiation field and a dust grain model, thereby physically connecting the UV-optical to the IR. We describe the computational method and explain the choices of parameters in DIRTYGrid. The computation took millions of CPU hours on supercomputers, and the SEDs produced are an invaluable tool for fitting multi-wavelength data sets. We provide the complete set of SEDs in an online table.

Electronic structure of boron based single and multi-layer two dimensional materials

NASA Astrophysics Data System (ADS)

Miyazato, Itsuki; Takahashi, Keisuke

2017-09-01

Two dimensional nanosheets based on boron and Group VA elements are designed and characterized using first principles calculations. B-N, B-P, B-As, B-Sb, and B-Bi are found to possess honeycomb structures where formation energies indicate exothermic reactions. Contrary to B-N, the cases of B-P, B-As, B-Sb, and B-Bi nanosheets are calculated to possess narrow band gaps. In addition, calculations reveal that the electronegativity difference between B and Group VA elements in the designed materials is a good indicator to predict the charge transfer and band gap of the two dimensional materials. Hydrogen adsorption over defect-free B-Sb and B-Bi results in exothermic reactions, while defect-free B-N, B-P, and B-As result in endothermic reactions. The layerability of the designed two dimensional materials is also investigated where the electronic structure of two-layered two dimensional materials is strongly coupled with how the two dimensional materials are layered. Thus, one can consider that the properties of two dimensional materials can be controlled by the composition of two dimensional materials and the structure of layers.

Multi-channel infrared thermometer

DOEpatents

Ulrickson, Michael A.

1986-01-01

A device for measuring the two-dimensional temperature profile of a surface comprises imaging optics for generating an image of the light radiating from the surface; an infrared detector array having a plurality of detectors; and a light pipe array positioned between the imaging optics and the detector array for sampling, transmitting, and distributing the image over the detector surfaces. The light pipe array includes one light pipe for each detector in the detector array.

Influence of nonlinear thermal radiation and viscous dissipation on three-dimensional flow of Jeffrey nano fluid over a stretching sheet in the presence of Joule heating

NASA Astrophysics Data System (ADS)

Ganesh Kumar, K.; Rudraswamy, N. G.; Gireesha, B. J.; Krishnamurthy, M. R.

2017-09-01

Present exploration discusses the combined effect of viscous dissipation and Joule heating on three dimensional flow and heat transfer of a Jeffrey nanofluid in the presence of nonlinear thermal radiation. Here the flow is generated over bidirectional stretching sheet in the presence of applied magnetic field by accounting thermophoresis and Brownian motion of nanoparticles. Suitable similarity transformations are employed to reduce the governing partial differential equations into coupled nonlinear ordinary differential equations. These nonlinear ordinary differential equations are solved numerically by using the Runge-Kutta-Fehlberg fourth-fifth order method with shooting technique. Graphically results are presented and discussed for various parameters. Validation of the current method is proved by comparing our results with the existing results under limiting situations. It can be concluded that combined effect of Joule and viscous heating increases the temperature profile and thermal boundary layer thickness.

Single-footprint retrievals for AIRS using a fast TwoSlab cloud-representation model and the SARTA all-sky infrared radiative transfer algorithm

NASA Astrophysics Data System (ADS)

DeSouza-Machado, Sergio; Larrabee Strow, L.; Tangborn, Andrew; Huang, Xianglei; Chen, Xiuhong; Liu, Xu; Wu, Wan; Yang, Qiguang

2018-01-01

One-dimensional variational retrievals of temperature and moisture fields from hyperspectral infrared (IR) satellite sounders use cloud-cleared radiances (CCRs) as their observation. These derived observations allow the use of clear-sky-only radiative transfer in the inversion for geophysical variables but at reduced spatial resolution compared to the native sounder observations. Cloud clearing can introduce various errors, although scenes with large errors can be identified and ignored. Information content studies show that, when using multilayer cloud liquid and ice profiles in infrared hyperspectral radiative transfer codes, there are typically only 2-4 degrees of freedom (DOFs) of cloud signal. This implies a simplified cloud representation is sufficient for some applications which need accurate radiative transfer. Here we describe a single-footprint retrieval approach for clear and cloudy conditions, which uses the thermodynamic and cloud fields from numerical weather prediction (NWP) models as a first guess, together with a simple cloud-representation model coupled to a fast scattering radiative transfer algorithm (RTA). The NWP model thermodynamic and cloud profiles are first co-located to the observations, after which the N-level cloud profiles are converted to two slab clouds (TwoSlab; typically one for ice and one for water clouds). From these, one run of our fast cloud-representation model allows an improvement of the a priori cloud state by comparing the observed and model-simulated radiances in the thermal window channels. The retrieval yield is over 90 %, while the degrees of freedom correlate with the observed window channel brightness temperature (BT) which itself depends on the cloud optical depth. The cloud-representation and scattering package is benchmarked against radiances computed using a maximum random overlap (RMO) cloud scheme. All-sky infrared radiances measured by NASA's Atmospheric Infrared Sounder (AIRS) and NWP thermodynamic and cloud profiles from the European Centre for Medium-Range Weather Forecasts (ECMWF) forecast model are used in this paper.

RAPTOR. I. Time-dependent radiative transfer in arbitrary spacetimes

NASA Astrophysics Data System (ADS)

Bronzwaer, T.; Davelaar, J.; Younsi, Z.; Mościbrodzka, M.; Falcke, H.; Kramer, M.; Rezzolla, L.

2018-05-01

Context. Observational efforts to image the immediate environment of a black hole at the scale of the event horizon benefit from the development of efficient imaging codes that are capable of producing synthetic data, which may be compared with observational data. Aims: We aim to present RAPTOR, a new public code that produces accurate images, animations, and spectra of relativistic plasmas in strong gravity by numerically integrating the equations of motion of light rays and performing time-dependent radiative transfer calculations along the rays. The code is compatible with any analytical or numerical spacetime. It is hardware-agnostic and may be compiled and run both on GPUs and CPUs. Methods: We describe the algorithms used in RAPTOR and test the code's performance. We have performed a detailed comparison of RAPTOR output with that of other radiative-transfer codes and demonstrate convergence of the results. We then applied RAPTOR to study accretion models of supermassive black holes, performing time-dependent radiative transfer through general relativistic magneto-hydrodynamical (GRMHD) simulations and investigating the expected observational differences between the so-called fast-light and slow-light paradigms. Results: Using RAPTOR to produce synthetic images and light curves of a GRMHD model of an accreting black hole, we find that the relative difference between fast-light and slow-light light curves is less than 5%. Using two distinct radiative-transfer codes to process the same data, we find integrated flux densities with a relative difference less than 0.01%. Conclusions: For two-dimensional GRMHD models, such as those examined in this paper, the fast-light approximation suffices as long as errors of a few percent are acceptable. The convergence of the results of two different codes demonstrates that they are, at a minimum, consistent. The public version of RAPTOR is available at the following URL: http://https://github.com/tbronzwaer/raptor

A microscale three-dimensional urban energy balance model for studying surface temperatures

NASA Astrophysics Data System (ADS)

Krayenhoff, E. Scott; Voogt, James A.

2007-06-01

A microscale three-dimensional (3-D) urban energy balance model, Temperatures of Urban Facets in 3-D (TUF-3D), is developed to predict urban surface temperatures for a variety of surface geometries and properties, weather conditions, and solar angles. The surface is composed of plane-parallel facets: roofs, walls, and streets, which are further sub-divided into identical square patches, resulting in a 3-D raster-type model geometry. The model code is structured into radiation, conduction and convection sub-models. The radiation sub-model uses the radiosity approach and accounts for multiple reflections and shading of direct solar radiation. Conduction is solved by finite differencing of the heat conduction equation, and convection is modelled by empirically relating patch heat transfer coefficients to the momentum forcing and the building morphology. The radiation and conduction sub-models are tested individually against measurements, and the complete model is tested against full-scale urban surface temperature and energy balance observations. Modelled surface temperatures perform well at both the facet-average and the sub-facet scales given the precision of the observations and the uncertainties in the model inputs. The model has several potential applications, such as the calculation of radiative loads, and the investigation of effective thermal anisotropy (when combined with a sensor-view model).

Multiple Scattering in Clouds: Insights from Three-Dimensional Diffusion/P{sub 1} Theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davis, Anthony B.; Marshak, Alexander

2001-03-15

In the atmosphere, multiple scattering matters nowhere more than in clouds, and being a product of its turbulence, clouds are highly variable environments. This challenges three-dimensional (3D) radiative transfer theory in a way that easily swamps any available computational resources. Fortunately, the far simpler diffusion (or P{sub 1}) theory becomes more accurate as the scattering intensifies, and allows for some analytical progress as well as computational efficiency. After surveying current approaches to 3D solar cloud-radiation problems from the diffusion standpoint, a general 3D result in steady-state diffusive transport is derived relating the variability-induced change in domain-average flux (i.e., diffuse transmittance)more » to the one-point covariance of internal fluctuations in particle density and in radiative flux. These flux variations follow specific spatial patterns in deliberately hydrodynamical language: radiative channeling. The P{sub 1} theory proves even more powerful when the photon diffusion process unfolds in time as well as space. For slab geometry, characteristic times and lengths that describe normal and transverse transport phenomena are derived. This phenomenology is used to (a) explain persistent features in satellite images of dense stratocumulus as radiative channeling, (b) set limits on current cloud remote-sensing techniques, and (c) propose new ones both active and passive.« less

Improving the accuracy of S02 column densities and emission rates obtained from upward-looking UV-spectroscopic measurements of volcanic plumes by taking realistic radiative transfer into account

USGS Publications Warehouse

Kern, Christoph; Deutschmann, Tim; Werner, Cynthia; Sutton, A. Jeff; Elias, Tamar; Kelly, Peter J.

2012-01-01

Sulfur dioxide (SO2) is monitored using ultraviolet (UV) absorption spectroscopy at numerous volcanoes around the world due to its importance as a measure of volcanic activity and a tracer for other gaseous species. Recent studies have shown that failure to take realistic radiative transfer into account during the spectral retrieval of the collected data often leads to large errors in the calculated emission rates. Here, the framework for a new evaluation method which couples a radiative transfer model to the spectral retrieval is described. In it, absorption spectra are simulated, and atmospheric parameters are iteratively updated in the model until a best match to the measurement data is achieved. The evaluation algorithm is applied to two example Differential Optical Absorption Spectroscopy (DOAS) measurements conducted at Kilauea volcano (Hawaii). The resulting emission rates were 20 and 90% higher than those obtained with a conventional DOAS retrieval performed between 305 and 315 nm, respectively, depending on the different SO2 and aerosol loads present in the volcanic plume. The internal consistency of the method was validated by measuring and modeling SO2 absorption features in a separate wavelength region around 375 nm and comparing the results. Although additional information about the measurement geometry and atmospheric conditions is needed in addition to the acquired spectral data, this method for the first time provides a means of taking realistic three-dimensional radiative transfer into account when analyzing UV-spectral absorption measurements of volcanic SO2 plumes.

In situ calibration of an infrared imaging video bolometer in the Large Helical Device

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mukai, K., E-mail: mukai.kiyofumi@LHD.nifs.ac.jp; Peterson, B. J.; Pandya, S. N.

The InfraRed imaging Video Bolometer (IRVB) is a powerful diagnostic to measure multi-dimensional radiation profiles in plasma fusion devices. In the Large Helical Device (LHD), four IRVBs have been installed with different fields of view to reconstruct three-dimensional profiles using a tomography technique. For the application of the measurement to plasma experiments using deuterium gas in LHD in the near future, the long-term effect of the neutron irradiation on the heat characteristics of an IRVB foil should be taken into account by regular in situ calibration measurements. Therefore, in this study, an in situ calibration system was designed.

Cosmology on a Mesh

NASA Astrophysics Data System (ADS)

Gill, Stuart P. D.; Knebe, Alexander; Gibson, Brad K.; Flynn, Chris; Ibata, Rodrigo A.; Lewis, Geraint F.

2003-04-01

An adaptive multi grid approach to simulating the formation of structure from collisionless dark matter is described. MLAPM (Multi-Level Adaptive Particle Mesh) is one of the most efficient serial codes available on the cosmological "market" today. As part of Swinburne University's role in the development of the Square Kilometer Array, we are implementing hydrodynamics, feedback, and radiative transfer within the MLAPM adaptive mesh, in order to simulate baryonic processes relevant to the interstellar and intergalactic media at high redshift. We will outline our progress to date in applying the existing MLAPM to a study of the decay of satellite galaxies within massive host potentials.

Integrated multidisciplinary CAD/CAE environment for micro-electro-mechanical systems (MEMS)

NASA Astrophysics Data System (ADS)

Przekwas, Andrzej J.

1999-03-01

Computational design of MEMS involves several strongly coupled physical disciplines, including fluid mechanics, heat transfer, stress/deformation dynamics, electronics, electro/magneto statics, calorics, biochemistry and others. CFDRC is developing a new generation multi-disciplinary CAD systems for MEMS using high-fidelity field solvers on unstructured, solution-adaptive grids for a full range of disciplines. The software system, ACE + MEMS, includes all essential CAD tools; geometry/grid generation for multi- discipline, multi-equation solvers, GUI, tightly coupled configurable 3D field solvers for FVM, FEM and BEM and a 3D visualization/animation tool. The flow/heat transfer/calorics/chemistry equations are solved with unstructured adaptive FVM solver, stress/deformation are computed with a FEM STRESS solver and a FAST BEM solver is used to solve linear heat transfer, electro/magnetostatics and elastostatics equations on adaptive polygonal surface grids. Tight multidisciplinary coupling and automatic interoperability between the tools was achieved by designing a comprehensive database structure and APIs for complete model definition. The virtual model definition is implemented in data transfer facility, a publicly available tool described in this paper. The paper presents overall description of the software architecture and MEMS design flow in ACE + MEMS. It describes current status, ongoing effort and future plans for the software. The paper also discusses new concepts of mixed-level and mixed- dimensionality capability in which 1D microfluidic networks are simulated concurrently with 3D high-fidelity models of discrete components.

Convective Heat Transfer in the Reusable Solid Rocket Motor of the Space Transportation System

NASA Technical Reports Server (NTRS)

Ahmad, Rashid A.; Cash, Stephen F. (Technical Monitor)

2002-01-01

This simulation involved a two-dimensional axisymmetric model of a full motor initial grain of the Reusable Solid Rocket Motor (RSRM) of the Space Transportation System (STS). It was conducted with CFD (computational fluid dynamics) commercial code FLUENT. This analysis was performed to: a) maintain continuity with most related previous analyses, b) serve as a non-vectored baseline for any three-dimensional vectored nozzles, c) provide a relatively simple application and checkout for various CFD solution schemes, grid sensitivity studies, turbulence modeling and heat transfer, and d) calculate nozzle convective heat transfer coefficients. The accuracy of the present results and the selection of the numerical schemes and turbulence models were based on matching the rocket ballistic predictions of mass flow rate, head end pressure, vacuum thrust and specific impulse, and measured chamber pressure drop. Matching these ballistic predictions was found to be good. This study was limited to convective heat transfer and the results compared favorably with existing theory. On the other hand, qualitative comparison with backed-out data of the ratio of the convective heat transfer coefficient to the specific heat at constant pressure was made in a relative manner. This backed-out data was devised to match nozzle erosion that was a result of heat transfer (convective, radiative and conductive), chemical (transpirating), and mechanical (shear and particle impingement forces) effects combined.

Cancer Trials Ireland (ICORG) 06-34: A multi-centre clinical trial using three-dimensional conformal radiation therapy to reduce the toxicity of palliative radiation for lung cancer.

PubMed

McDermott, Ronan L; Armstrong, John G; Thirion, Pierre; Dunne, Mary; Finn, Marie; Small, Cormac; Byrne, Mary; O'Shea, Carmel; O'Sullivan, Lydia; Shannon, Aoife; Kelly, Emma; Hacking, Dayle J

2018-05-01

Cancer Trials Ireland (ICORG) 06-34: A multi-centre clinical trial using three-dimensional conformal radiation therapy to reduce the toxicity of palliative radiation for lung cancer. NCT01176487. Trials of radiation therapy for the palliation of intra-thoracic symptoms from locally advanced non-small cell lung cancer (NSCLC) have concentrated on optimising fractionation and dose schedules. In these trials, the rates of oesophagitis induced by this "palliative" therapy have been unacceptably high. In contrast, this non-randomised, single-arm trial was designed to assess if more technically advanced treatment techniques would result in equivalent symptom relief and reduce the side-effect of symptomatic oesophagitis. Thirty-five evaluable patients with symptomatic locally advanced or metastatic NSCLC were treated using a three-dimensional conformal technique (3-DCRT) and standardised dose regimens of 39 Gy in 13 fractions, 20 Gy in 5 fractions or 17 Gy in 2 fractions. Treatment plans sought to minimise oesophageal dose. Oesophagitis was recorded during treatment, at two weeks, one month and three months following radiation therapy and 3-6 monthly thereafter. Mean dose to the irradiated oesophagus was calculated for all treatment plans. Five patients (14%) had experienced grade 2 oesophagitis or dysphagia or both during treatment and 2 other patients had these side effects at the 2-week follow-up. At follow-up of one month after therapy, there was no grade two or higher oesophagitis or dysphagia reported. 22 patients were eligible for assessment of late toxicity. Five of these patients reported oesophagitis or dysphagia (one had grade 3 dysphagia, two had grade 2 oesophagitis, one of whom also had grade 2 dysphagia). Quality of Life (QoL) data at baseline and at 1-month follow up were available for 20 patients. At 1-month post radiation therapy, these patients had slightly less trouble taking a short walk, less shortness of breath, did not feel as weak, had better appetite and generally had a better overall quality of life than they did at baseline. They did report being slightly more tired. This trial is the first of its kind showing that 3-DCRT provides patients with lower rates of oesophageal toxicity whilst yielding acceptable rates of symptom control. (Sponsored by Cancer Trials Ireland (ICORG) Study number 06-34, the Friends of St. Luke's and the St. Luke's Institute of Cancer Research.). Copyright © 2018 Elsevier B.V. All rights reserved.

A Theoretical Evaluation of Secondary Atomization Effects on Engine Performance for Aluminum Gel Propellants

NASA Technical Reports Server (NTRS)

Mueller, D. C.; Turns, S. R.

1994-01-01

A one-dimensional model of a gel-fueled rocket combustion chamber has been developed. This model includes the processes of liquid hydrocarbon burnout, secondary atomization. aluminum ignition, and aluminum combustion. Also included is a model of radiative heat transfer from the solid combustion products to the chamber walls. Calculations indicate that only modest secondary atomization is required to significantly reduce propellant burnout distances, aluminum oxide residual size and radiation heat wall losses. Radiation losses equal to approximately 2-13 percent of the energy released during combustion were estimated. A two-dimensional, two-phase nozzle code was employed to estimate radiation and nozzle two-phase flow effects on overall engine performance. Radiation losses yielded a 1 percent decrease in engine I(sub sp). Results also indicate that secondary atomization may have less effect on two-phase losses than it does on propellant burnout distance and no effect if oxide particle coagulation and shear induced droplet breakup govern oxide particle size. Engine I(sub sp) was found to decrease from 337.4 to 293.7 seconds as gel aluminum mass loading was varied from 0-70 wt percent. Engine I(sub sp) efficiencies, accounting for radiation and two-phase flow effects, on the order of 0.946 were calculated for a 60 wt percent gel, assuming a fragmentation ratio of 5.

FIBRE AND INTEGRATED OPTICS. OPTICAL PROCESSING OF INFORMATION: Feasibility of using waveguide holograms in systems for the transfer of amplitude—phase information along fibre communication lines

NASA Astrophysics Data System (ADS)

Dianov, Evgenii M.; Zubov, Vladimir A.; Putilin, A. N.

1995-02-01

An analysis is made of a variant of a system for spatial—temporal transformation of spatially one-dimensional information for its transfer along a single-mode fibre waveguide. Information is coupled into a fibre by a waveguide hologram. This hologram forms a light-beam structure which matches the fibre-guided mode. A report is given of the use of ion-exchange planar glass waveguides as waveguide holograms. An amorphous chalcogenide semiconductor film or a photoresist was deposited by evaporation on such a planar waveguide. Reconstruction of the waveguide hologram made it possible to achieve a high read rate, up to 1011 pixels per second, when a short radiation pulse was used. Multisectioned injection semiconductor lasers, operating under Q-switching conditions, were used as the radiation sources.

Apparatus and method for detecting full-capture radiation events

DOEpatents

Odell, D.M.C.

1994-10-11

An apparatus and method are disclosed for sampling the output signal of a radiation detector and distinguishing full-capture radiation events from Compton scattering events. The output signal of a radiation detector is continuously sampled. The samples are converted to digital values and input to a discriminator where samples that are representative of events are identified. The discriminator transfers only event samples, that is, samples representing full-capture events and Compton events, to a signal processor where the samples are saved in a three-dimensional count matrix with time (from the time of onset of the pulse) on the first axis, sample pulse current amplitude on the second axis, and number of samples on the third axis. The stored data are analyzed to separate the Compton events from full-capture events, and the energy of the full-capture events is determined without having determined the energies of any of the individual radiation detector events. 4 figs.

Apparatus and method for detecting full-capture radiation events

DOEpatents

Odell, Daniel M. C.

1994-01-01

An apparatus and method for sampling the output signal of a radiation detector and distinguishing full-capture radiation events from Compton scattering events. The output signal of a radiation detector is continuously sampled. The samples are converted to digital values and input to a discriminator where samples that are representative of events are identified. The discriminator transfers only event samples, that is, samples representing full-capture events and Compton events, to a signal processor where the samples are saved in a three-dimensional count matrix with time (from the time of onset of the pulse) on the first axis, sample pulse current amplitude on the second axis, and number of samples on the third axis. The stored data are analyzed to separate the Compton events from full-capture events, and the energy of the full-capture events is determined without having determined the energies of any of the individual radiation detector events.

Cross diffusion and exponential space dependent heat source impacts in radiated three-dimensional (3D) flow of Casson fluid by heated surface

NASA Astrophysics Data System (ADS)

Zaigham Zia, Q. M.; Ullah, Ikram; Waqas, M.; Alsaedi, A.; Hayat, T.

2018-03-01

This research intends to elaborate Soret-Dufour characteristics in mixed convective radiated Casson liquid flow by exponentially heated surface. Novel features of exponential space dependent heat source are introduced. Appropriate variables are implemented for conversion of partial differential frameworks into a sets of ordinary differential expressions. Homotopic scheme is employed for construction of analytic solutions. Behavior of various embedding variables on velocity, temperature and concentration distributions are plotted graphically and analyzed in detail. Besides, skin friction coefficients and heat and mass transfer rates are also computed and interpreted. The results signify the pronounced characteristics of temperature corresponding to convective and radiation variables. Concentration bears opposite response for Soret and Dufour variables.

A Integrated Service Platform for Remote Sensing Image 3D Interpretation and Draughting based on HTML5

NASA Astrophysics Data System (ADS)

LIU, Yiping; XU, Qing; ZhANG, Heng; LV, Liang; LU, Wanjie; WANG, Dandi

2016-11-01

The purpose of this paper is to solve the problems of the traditional single system for interpretation and draughting such as inconsistent standards, single function, dependence on plug-ins, closed system and low integration level. On the basis of the comprehensive analysis of the target elements composition, map representation and similar system features, a 3D interpretation and draughting integrated service platform for multi-source, multi-scale and multi-resolution geospatial objects is established based on HTML5 and WebGL, which not only integrates object recognition, access, retrieval, three-dimensional display and test evaluation but also achieves collection, transfer, storage, refreshing and maintenance of data about Geospatial Objects and shows value in certain prospects and potential for growth.

Boost-phase discrimination research activities

NASA Technical Reports Server (NTRS)

Cooper, David M.; Deiwert, George S.

1989-01-01

Theoretical research in two areas was performed. The aerothermodynamics research focused on the hard-body and rocket plume flows. Analytical real gas models to describe finite rate chemistry were developed and incorporated into the three-dimensional flow codes. New numerical algorithms capable of treating multi-species reacting gas equations and treating flows with large gradients were also developed. The computational chemistry research focused on the determination of spectral radiative intensity factors, transport properties and reaction rates. Ab initio solutions to the Schrodinger equation provided potential energy curves transition moments (radiative probabilities and strengths) and potential energy surfaces. These surfaces were then coupled with classical particle reactive trajectories to compute reaction cross-sections and rates.

The coupling of MATISSE and the SE-WORKBENCH: a new solution for simulating efficiently the atmospheric radiative transfer and the sea surface radiation

NASA Astrophysics Data System (ADS)

Cathala, Thierry; Douchin, Nicolas; Latger, Jean; Caillault, Karine; Fauqueux, Sandrine; Huet, Thierry; Lubarre, Luc; Malherbe, Claire; Rosier, Bernard; Simoneau, Pierre

2009-05-01

The SE-WORKBENCH workshop, also called CHORALE (French acceptation for "simulated Optronic Acoustic Radar battlefield") is used by the French DGA (MoD) and several other Defense organizations and companies all around the World to perform multi-sensors simulations. CHORALE enables the user to create virtual and realistic multi spectral 3D scenes that may contain several types of target, and then generate the physical signal received by a sensor, typically an IR sensor. The SE-WORKBENCH can be used either as a collection of software modules through dedicated GUIs or as an API made of a large number of specialized toolkits. The SE-WORKBENCH is made of several functional block: one for geometrically and physically modeling the terrain and the targets, one for building the simulation scenario and one for rendering the synthetic environment, both in real and non real time. Among the modules that the modeling block is composed of, SE-ATMOSPHERE is used to simulate the atmospheric conditions of a Synthetic Environment and then to integrate the impact of these conditions on a scene. This software product generates an exploitable physical atmosphere by the SE WORKBENCH tools generating spectral images. It relies on several external radiative transfer models such as MODTRAN V4.2 in the current version. MATISSE [4,5] is a background scene generator developed for the computation of natural background spectral radiance images and useful atmospheric radiative quantities (radiance and transmission along a line of sight, local illumination, solar irradiance ...). Backgrounds include atmosphere, low and high altitude clouds, sea and land. A particular characteristic of the code is its ability to take into account atmospheric spatial variability (temperatures, mixing ratio, etc) along each line of sight. An Application Programming Interface (API) is included to facilitate its use in conjunction with external codes. MATISSE is currently considered as a new external radiative transfer model to be integrated in SE-ATMOSPHERE as a complement to MODTRAN. Compared to the latter which is used as a whole MATISSE can be used step by step and modularly as an API: this can avoid to pre compute large atmospheric parameters tables as it is done currently with MODTRAN. The use of MATISSE will also enable a real coupling between the ray tracing process of the SEWORKBENCH and the radiative transfer model of MATISSE. This will lead to the improvement of the link between a general atmospheric model and a specific 3D terrain. The paper will demonstrate the advantages for the SE WORKEBNCH of using MATISSE as a new atmospheric code, but also for computing the radiative properties of the sea surface.

3-Dimensional Nano-Scale Reinforcement Architecture for Advanced Composite Structures

DTIC Science & Technology

2008-10-01

textile structures on 3TEX equipment. Conduct experimental studies of the spinnability of Multi-Wall Carbon Nanotube ( MWCNT ) forests and...adjacent inner wall when MWNT length is one centimeter (Fig. 1.8). Complete stress transfer to all walls by going to longer nanotube lengths could...between regular IK T300 carbon yarn and 25-ply carbon nanotube yarn. Fig. 5.8 shows the nanotube yarns going through the heddles during weaving with

An asymptotic preserving unified gas kinetic scheme for frequency-dependent radiative transfer equations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Wenjun, E-mail: sun_wenjun@iapcm.ac.cn; Jiang, Song, E-mail: jiang@iapcm.ac.cn; Xu, Kun, E-mail: makxu@ust.hk

This paper presents an extension of previous work (Sun et al., 2015 [22]) of the unified gas kinetic scheme (UGKS) for the gray radiative transfer equations to the frequency-dependent (multi-group) radiative transfer system. Different from the gray radiative transfer equations, where the optical opacity is only a function of local material temperature, the simulation of frequency-dependent radiative transfer is associated with additional difficulties from the frequency-dependent opacity. For the multiple frequency radiation, the opacity depends on both the spatial location and the frequency. For example, the opacity is typically a decreasing function of frequency. At the same spatial region themore » transport physics can be optically thick for the low frequency photons, and optically thin for high frequency ones. Therefore, the optical thickness is not a simple function of space location. In this paper, the UGKS for frequency-dependent radiative system is developed. The UGKS is a finite volume method and the transport physics is modeled according to the ratio of the cell size to the photon's frequency-dependent mean free path. When the cell size is much larger than the photon's mean free path, a diffusion solution for such a frequency radiation will be obtained. On the other hand, when the cell size is much smaller than the photon's mean free path, a free transport mechanism will be recovered. In the regime between the above two limits, with the variation of the ratio between the local cell size and photon's mean free path, the UGKS provides a smooth transition in the physical and frequency space to capture the corresponding transport physics accurately. The seemingly straightforward extension of the UGKS from the gray to multiple frequency radiation system is due to its intrinsic consistent multiple scale transport modeling, but it still involves lots of work to properly discretize the multiple groups in order to design an asymptotic preserving (AP) scheme in all regimes. The current scheme is tested in a few frequency-dependent radiation problems, and the results are compared with the solutions from the well-defined implicit Monte Carlo (IMC) method. The UGKS is much more efficient than IMC, and the computational times of both schemes for all test cases are listed. The UGKS seems to be the first discrete ordinate method (DOM) for the accurate capturing of multiple frequency radiative transport physics from ballistic particle motion to the diffusive wave propagation.« less

Absorption of Solar Radiation by the Cloudy Atmosphere Interpretations of Collocated Aircraft Measurements

NASA Technical Reports Server (NTRS)

Valero, Francisco P. J.; Cess, Robert D.; Zhang, Minghua; Pope, Shelly K.; Bucholtz, Anthony; Bush, Brett; Vitko, John, Jr.

1997-01-01

As part of the Atmospheric Radiation Measurement (ARM) Enhanced Shortwave Experiment (ARESE), we have obtained and analyzed measurements made from collocated aircraft of the absorption of solar radiation within the atmospheric column between the two aircraft. The measurements were taken during October 1995 at the ARM site in Oklahoma. Relative to a theoretical radiative transfer model, we find no evidence for excess solar absorption in the clear atmosphere and significant evidence for its existence in the cloudy atmosphere. This excess cloud solar absorption appears to occur in both visible (0.224-0.68 microns) and near-infrared (0.68-3.30 microns) spectral regions, although not at 0.5 microns for the visible contribution, and it is shown to be true absorption rather than an artifact of sampling errors caused by measuring three-dimensional clouds.

Corrosion and Heat Transfer Characteristics of Water Dispersed with Carboxylate Additives and Multi Walled Carbon Nano Tubes

NASA Astrophysics Data System (ADS)

Moorthy, Chellapilla V. K. N. S. N.; Srinivas, Vadapalli

2016-10-01

This paper summarizes a recent work on anti-corrosive properties and enhanced heat transfer properties of carboxylated water based nanofluids. Water mixed with sebacic acid as carboxylate additive found to be resistant to corrosion and suitable for automotive environment. The carboxylated water is dispersed with very low mass concentration of carbon nano tubes at 0.025, 0.05 and 0.1 %. The stability of nanofluids in terms of zeta potential is found to be good with carboxylated water compared to normal water. The heat transfer performance of nanofluids is carried out on an air cooled heat exchanger similar to an automotive radiator with incoming air velocities across radiator at 5, 10 and 15 m/s. The flow Reynolds number of water is in the range of 2500-6000 indicating developing flow regime. The corrosion resistance of nanofluids is found to be good indicating its suitability to automotive environment. There is a slight increase in viscosity and marginal decrease in the specific heat of nanofluids with addition of carboxylate as well as CNTs. Significant improvement is observed in the thermal conductivity of nanofluids dispersed with CNTs. During heat transfer experimentation, the inside heat transfer coefficient and overall heat transfer coefficient has also improved markedly. It is also found that the velocity of air and flow rate of coolant plays an important role in enhancement of the heat transfer coefficient and overall heat transfer coefficient.

Inverse optimal design of the radiant heating in materials processing and manufacturing

NASA Astrophysics Data System (ADS)

Fedorov, A. G.; Lee, K. H.; Viskanta, R.

1998-12-01

Combined convective, conductive, and radiative heat transfer is analyzed during heating of a continuously moving load in the industrial radiant oven. A transient, quasi-three-dimensional model of heat transfer between a continuous load of parts moving inside an oven on a conveyor belt at a constant speed and an array of radiant heaters/burners placed inside the furnace enclosure is developed. The model accounts for radiative exchange between the heaters and the load, heat conduction in the load, and convective heat transfer between the moving load and oven environment. The thermal model developed has been used to construct a general framework for an inverse optimal design of an industrial oven as an example. In particular, the procedure based on the Levenberg-Marquardt nonlinear least squares optimization algorithm has been developed to obtain the optimal temperatures of the heaters/burners that need to be specified to achieve a prescribed temperature distribution of the surface of a load. The results of calculations for several sample cases are reported to illustrate the capabilities of the procedure developed for the optimal inverse design of an industrial radiant oven.

Multi-channel infrared thermometer

DOEpatents

Ulrickson, M.A.

A device for measuring the two-dimensional temperature profile of a surface comprises imaging optics for generating an image of the light radiating from the surface; an infrared detector array having a plurality of detectors; and optical means positioned between the imaging optics and the detector array for sampling, transmitting, and distributing the image over the detector surfaces. The optical means may be a light pipe array having one light pipe for each detector in the detector array.

DART: Recent Advances in Remote Sensing Data Modeling With Atmosphere, Polarization, and Chlorophyll Fluorescence

NASA Technical Reports Server (NTRS)

Gastellu-Etchegorry, Jean-Phil; Lauret, Nicolas; Yin, Tiangang; Landier, Lucas; Kallel, Abdelaziz; Malenovsky, Zbynek; Bitar, Ahmad Al; Aval, Josselin; Benhmida, Sahar; Qi, Jianbo;

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mueller, Bernhard; Janka, Hans-Thomas; Marek, Andreas, E-mail: bjmuellr@mpa-garching.mpg.de, E-mail: thj@mpa-garching.mpg.de

We present the first two-dimensional general relativistic (GR) simulations of stellar core collapse and explosion with the COCONUT hydrodynamics code in combination with the VERTEX solver for energy-dependent, three-flavor neutrino transport, using the extended conformal flatness condition for approximating the space-time metric and a ray-by-ray-plus ansatz to tackle the multi-dimensionality of the transport. For both of the investigated 11.2 and 15 M{sub Sun} progenitors we obtain successful, though seemingly marginal, neutrino-driven supernova explosions. This outcome and the time evolution of the models basically agree with results previously obtained with the PROMETHEUS hydro solver including an approximative treatment of relativistic effectsmore » by a modified Newtonian potential. However, GR models exhibit subtle differences in the neutrinospheric conditions compared with Newtonian and pseudo-Newtonian simulations. These differences lead to significantly higher luminosities and mean energies of the radiated electron neutrinos and antineutrinos and therefore to larger energy-deposition rates and heating efficiencies in the gain layer with favorable consequences for strong nonradial mass motions and ultimately for an explosion. Moreover, energy transfer to the stellar medium around the neutrinospheres through nucleon recoil in scattering reactions of heavy-lepton neutrinos also enhances the mentioned effects. Together with previous pseudo-Newtonian models, the presented relativistic calculations suggest that the treatment of gravity and energy-exchanging neutrino interactions can make differences of even 50%-100% in some quantities and is likely to contribute to a finally successful explosion mechanism on no minor level than hydrodynamical differences between different dimensions.« less

Nonlinear bioheat transfer models and multi-objective numerical optimization of the cryosurgery operations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kudryashov, Nikolay A.; Shilnikov, Kirill E.

Numerical computation of the three dimensional problem of the freezing interface propagation during the cryosurgery coupled with the multi-objective optimization methods is used in order to improve the efficiency and safety of the cryosurgery operations performing. Prostate cancer treatment and cutaneous cryosurgery are considered. The heat transfer in soft tissue during the thermal exposure to low temperature is described by the Pennes bioheat model and is coupled with an enthalpy method for blurred phase change computations. The finite volume method combined with the control volume approximation of the heat fluxes is applied for the cryosurgery numerical modeling on the tumormore » tissue of a quite arbitrary shape. The flux relaxation approach is used for the stability improvement of the explicit finite difference schemes. The method of the additional heating elements mounting is studied as an approach to control the cellular necrosis front propagation. Whereas the undestucted tumor tissue and destucted healthy tissue volumes are considered as objective functions, the locations of additional heating elements in cutaneous cryosurgery and cryotips in prostate cancer cryotreatment are considered as objective variables in multi-objective problem. The quasi-gradient method is proposed for the searching of the Pareto front segments as the multi-objective optimization problem solutions.« less

GRAMS: A Grid of RSG and AGB Models

NASA Astrophysics Data System (ADS)

Srinivasan, S.; Sargent, B. A.; Meixner, M.

2011-09-01

We present a grid of oxygen- and carbon-rich circumstellar dust radiative transfer models for asymptotic giant branch (AGB) and red supergiant (RSG) stars. The grid samples a large region of the relevant parameter space, and it allows for a quick calculation of bolometric fluxes and dust mass-loss rates from multi-wavelength photometry. This method of fitting observed spectral energy distributions (SEDs) is preferred over detailed radiative transfer calculations, especially for large data sets such as the SAGE (Surveying the Agents of a Galaxy's Evolution) survey of the Magellanic Clouds. The mass-loss rates calculated for SAGE data will allow us to quantify the dust returned to the interstellar medium (ISM) by the entire AGB population. The total injection rate provides an important constraint for models of galactic chemical evolution. Here, we discuss our carbon star models and compare the results to SAGE observations in the Large Magellanic Cloud (LMC).

Babinet-Inverted Optical Yagi-Uda Antenna for Unidirectional Radiation to Free Space

NASA Astrophysics Data System (ADS)

Kim, Jineun; Roh, Young-Geun; Cheon, Sangmo; Choe, Jong-Ho; Lee, Jongcheon; Lee, Jaesoong; Jeong, Heejeong; Kim, Un Jeong; Park, Yeonsang; Song, In Yong; Park, Q.-Han; Hwang, Sung Woo; Kim, Kinam; Lee, Chang-Won

2014-06-01

Plasmonic nanoantennas are key elements in nanophotonics capable of directing radiation or enhancing the transition rate of a quantum emitter. Slot-type magnetic-dipole nanoantennas, which are complementary structures of typical electric-dipole-type antennas, have received little attention, leaving their antenna properties largely unexplored. Here we present a novel magnetic-dipole-fed multi-slot optical Yagi-Uda antenna. By engineering the relative phase of the interacting surface plasmon polaritons between the slot elements, we demonstrate that the optical antenna exhibits highly unidirectional radiation to free space. The unique features of the slot-based magnetic nanoantenna provide a new possibility of achieving integrated features such as energy transfer from one waveguide to another by working as a future optical via.

The Multi-Universe Cosmos. The Origin and Fate of our Universe

NASA Astrophysics Data System (ADS)

Velan, Karel

18 billion yers ago our Universe, one of many in the Cosmos, emerged from a hot, dense fireball of matter and energy created in the 4-dimensional cosmic space-time from virtual particles receiving their rest mass from a powerful primordial radiation field, the missing link to any viable theory of creation. The cloud of elementary particles and radiation collapsed by gravity into a fireball until its trappped thermal radiation caused a titanic explosion that initiated the expansion and evolution of ours universe. As the universe expanded and cooled it spawned galaxies, stars, planets and life. Proven laws of physics, observationsl data and mathematical computations support the new cosmological model which proposes a large number of universes in the cosmos in varying stages of evolution

Manipulation of Liquids Using Phased Array Generation of Acoustic Radiation Pressure

NASA Technical Reports Server (NTRS)

Oeftering, Richard C. (Inventor)

2000-01-01

A phased array of piezoelectric transducers is used to control and manipulate contained as well as uncontained fluids in space and earth applications. The transducers in the phased array are individually activated while being commonly controlled to produce acoustic radiation pressure and acoustic streaming. The phased array is activated to produce a single pulse, a pulse burst or a continuous pulse to agitate, segregate or manipulate liquids and gases. The phased array generated acoustic radiation pressure is also useful in manipulating a drop, a bubble or other object immersed in a liquid. The transducers can be arranged in any number of layouts including linear single or multi- dimensional, space curved and annular arrays. The individual transducers in the array are activated by a controller, preferably driven by a computer.

Efficient radiative transfer methods for continuum and line transfer in large three-dimensional models

NASA Astrophysics Data System (ADS)

Juvela, Mika J.

The relationship between physical conditions of an interstellar cloud and the observed radiation is defined by the radiative transfer problem. Radiative transfer calculations are needed if, e.g., one wants to disentangle abundance variations from excitation effects or wants to model variations of dust properties inside an interstellar cloud. New observational facilities (e.g., ALMA and Herschel) will bring improved accuracy both in terms of intensity and spatial resolution. This will enable detailed studies of the densest sub-structures of interstellar clouds and star forming regions. Such observations must be interpreted with accurate radiative transfer methods and realistic source models. In many cases this will mean modelling in three dimensions. High optical depths and observed wide range of linear scales are, however, challenging for radiative transfer modelling. A large range of linear scales can be accessed only with hierarchical models. Figure 1 shows an example of the use of a hierarchical grid for radiative transfer calculations when the original model cloud (L=10 pc, =500 cm-3) was based a MHD simulation carried out on a regular grid (Juvela & Padoan, 2005). For computed line intensities an accuracy of 10% was still reached when the number of individual cells (and the run time) was reduced by a factor of ten. This illustrates how, as long as cloud is not extremely optically thick, most of the emission comes from a small sub-volume. It is also worth noting that while errors are ~10% for any given point they are much smaller when compared with intensity variations. In particular, calculations on hierarchical grid recovered the spatial power spectrum of line emission with very good accuracy. Monte Carlo codes are used widely in both continuum and line transfer calculations. Like any lambda iteration schemes these suffer from slow convergence when models are optically thick. In line transfer Accelerated Monte Carlo methods (AMC) present a partial solution to this problem (Juvela & Padoan, 2000; Hogerheijde & van der Tak, 2000). AMC methods can be used similarly in continuum calculations to speed up the computation of dust temperatures (Juvela, 2005). The sampling problems associated with high optical depths can be solved with weighted sampling and the handling of models with τV ~ 1000 is perfectly feasible. Transiently heated small dust grains pose another problem because the calculation of their temperature distribution is very time consuming. However, a 3D model will contain thousands of cells at very similar conditions. If dust temperature distributions are calculated only once for such a set an approximate solution can be found in a much shorter time time. (Juvela & Padoan, 2003; see Figure 2a). MHD simulations with Automatic Mesh Refinement (AMR) techniques present an exciting development for the modelling of interstellar clouds. Cloud models consist of a hierarchy of grids with different grid steps and the ratio between the cloud size and the smallest resolution elements can be 106 or even larger. We are currently working on radiative transfer codes (line and continuum) that could be used efficiently on such grids (see Figure 2b). The radiative transfer problem can be solved relatively independently on each of the sub-grids. This means that the use of convergence acceleration methods can be limited to those sub-grids where they are needed and, on the other hand, parallelization of the code is straightforward.

Coupled multi-disciplinary simulation of composite engine structures in propulsion environment

NASA Technical Reports Server (NTRS)

Chamis, Christos C.; Singhal, Surendra N.

1992-01-01

A computational simulation procedure is described for the coupled response of multi-layered multi-material composite engine structural components which are subjected to simultaneous multi-disciplinary thermal, structural, vibration, and acoustic loadings including the effect of hostile environments. The simulation is based on a three dimensional finite element analysis technique in conjunction with structural mechanics codes and with acoustic analysis methods. The composite material behavior is assessed at the various composite scales, i.e., the laminate/ply/constituents (fiber/matrix), via a nonlinear material characterization model. Sample cases exhibiting nonlinear geometrical, material, loading, and environmental behavior of aircraft engine fan blades, are presented. Results for deformed shape, vibration frequency, mode shapes, and acoustic noise emitted from the fan blade, are discussed for their coupled effect in hot and humid environments. Results such as acoustic noise for coupled composite-mechanics/heat transfer/structural/vibration/acoustic analyses demonstrate the effectiveness of coupled multi-disciplinary computational simulation and the various advantages of composite materials compared to metals.

Parameterization and analysis of 3-D radiative transfer in clouds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Varnai, Tamas

2012-03-16

This report provides a summary of major accomplishments from the project. The project examines the impact of radiative interactions between neighboring atmospheric columns, for example clouds scattering extra sunlight toward nearby clear areas. While most current cloud models don't consider these interactions and instead treat sunlight in each atmospheric column separately, the resulting uncertainties have remained unknown. This project has provided the first estimates on the way average solar heating is affected by interactions between nearby columns. These estimates have been obtained by combining several years of cloud observations at three DOE Atmospheric Radiation Measurement (ARM) Climate Research Facility sitesmore » (in Alaska, Oklahoma, and Papua New Guinea) with simulations of solar radiation around the observed clouds. The importance of radiative interactions between atmospheric columns was evaluated by contrasting simulations that included the interactions with those that did not. This study provides lower-bound estimates for radiative interactions: It cannot consider interactions in cross-wind direction, because it uses two-dimensional vertical cross-sections through clouds that were observed by instruments looking straight up as clouds drifted aloft. Data from new DOE scanning radars will allow future radiative studies to consider the full three-dimensional nature of radiative processes. The results reveal that two-dimensional radiative interactions increase overall day-and-night average solar heating by about 0.3, 1.2, and 4.1 Watts per meter square at the three sites, respectively. This increase grows further if one considers that most large-domain cloud simulations have resolutions that cannot specify small-scale cloud variability. For example, the increases in solar heating mentioned above roughly double for a fairly typical model resolution of 1 km. The study also examined the factors that shape radiative interactions between atmospheric columns and found that local effects were often much larger than the overall values mentioned above, and were especially large for high sun and near convective clouds such as cumulus. The study also found that statistical methods such as neural networks appear promising for enabling cloud models to consider radiative interactions between nearby atmospheric columns. Finally, through collaboration with German scientists, the project found that new methods (especially one called stepwise kriging) show great promise in filling gaps between cloud radar scans. If applied to data from the new DOE scanning cloud radars, these methods can yield large, continuous three-dimensional cloud structures for future radiative simulations.« less

Optimal spacing within a tubed, volumetric, cavity receiver suitable for modular molten salt solar towers

NASA Astrophysics Data System (ADS)

Turner, Peter

2016-05-01

A 2-dimensional radiation analysis has been developed to analyse the radiative efficiency of an arrangement of heat transfer tubes distributed in layers but spaced apart to form a tubed, volumetric receiver. Such an arrangement could be suitable for incorporation into a cavity receiver. Much of the benefit of this volumetric approach is gained after using 5 layers although improvements do continue with further layers. The radiation analysis splits each tube into multiple segments in which each segment surface can absorb, reflect and radiate rays depending on its surface temperature. An iterative technique is used to calculate appropriate temperatures depending on the distribution of the net energy absorbed and assuming that the cool heat transfer fluid (molten salt) starts at the front layer and flows back through successive layers to the rear of the cavity. Modelling the finite diameter of each layer of tubes increases the ability of a layer to block radiation scattered at acute angles and this effect is shown to reduce radiation losses by nearly 25% compared to the earlier 1-d analysis. Optimum efficient designs tend to occur when the blockage factor is 0.2 plus the inverse of the number of tube layers. It is beneficial if the distance between successive layers is ≥ 2 times the diameter of individual tubes and in this situation, if the incoming radiation is spread over a range of angles, the performance is insensitive to the degree of any tube positional offset or stagger between layers.

A generalized volumetric dispersion model for a class of two-phase separation/reaction: finite difference solutions

NASA Astrophysics Data System (ADS)

Siripatana, Chairat; Thongpan, Hathaikarn; Promraksa, Arwut

2017-03-01

This article explores a volumetric approach in formulating differential equations for a class of engineering flow problems involving component transfer within or between two phases. In contrast to conventional formulation which is based on linear velocities, this work proposed a slightly different approach based on volumetric flow-rate which is essentially constant in many industrial processes. In effect, many multi-dimensional flow problems found industrially can be simplified into multi-component or multi-phase but one-dimensional flow problems. The formulation is largely generic, covering counter-current, concurrent or batch, fixed and fluidized bed arrangement. It was also intended to use for start-up, shut-down, control and steady state simulation. Since many realistic and industrial operation are dynamic with variable velocity and porosity in relation to position, analytical solutions are rare and limited to only very simple cases. Thus we also provide a numerical solution using Crank-Nicolson finite difference scheme. This solution is inherently stable as tested against a few cases published in the literature. However, it is anticipated that, for unconfined flow or non-constant flow-rate, traditional formulation should be applied.

Overview of aerothermodynamic loads definition study

NASA Technical Reports Server (NTRS)

Gaugler, Raymond E.

1991-01-01

The objective of the Aerothermodynamic Loads Definition Study is to develop methods of accurately predicting the operating environment in advanced Earth-to-Orbit (ETO) propulsion systems, such as the Space Shuttle Main Engine (SSME) powerhead. Development of time averaged and time dependent three dimensional viscous computer codes as well as experimental verification and engine diagnostic testing are considered to be essential in achieving that objective. Time-averaged, nonsteady, and transient operating loads must all be well defined in order to accurately predict powerhead life. Described here is work in unsteady heat flow analysis, improved modeling of preburner flow, turbulence modeling for turbomachinery, computation of three dimensional flow with heat transfer, and unsteady viscous multi-blade row turbine analysis.

Positron emission imaging device and method of using the same

DOEpatents

Bingham, Philip R.; Mullens, James Allen

2013-01-15

An imaging system and method of imaging are disclosed. The imaging system can include an external radiation source producing pairs of substantially simultaneous radiation emissions of a picturization emission and a verification emissions at an emission angle. The imaging system can also include a plurality of picturization sensors and at least one verification sensor for detecting the picturization and verification emissions, respectively. The imaging system also includes an object stage is arranged such that a picturization emission can pass through an object supported on said object stage before being detected by one of said plurality of picturization sensors. A coincidence system and a reconstruction system can also be included. The coincidence can receive information from the picturization and verification sensors and determine whether a detected picturization emission is direct radiation or scattered radiation. The reconstruction system can produce a multi-dimensional representation of an object imaged with the imaging system.

Spatiotemporal and spectral characteristics of X-ray radiation emitted by the Z-pinch during the current implosion of quasispherical multiwire arrays

NASA Astrophysics Data System (ADS)

Gritsuk, A. N.

2017-12-01

For the first time, a quasi-spherical current implosion has been experimentally realized on a multimegaampere facility with the peak current of up to 4 MA and a soft X-ray source has been created with high radiation power density on its surface of up to 3 TW/cm2. An increase in the energy density at the centre of the source of soft X-ray radiation (SXR) was experimentally observed upon compression of quasi-spherical arrays with the linear-mass profiling. In this case, the average power density on the surface of the SXR source is three times higher than for implosions of cylindrical arrays of the same mass and close values of the discharge current. Obtained experimental data are compared with the results of modelling the current implosion of multi-wire arrays performed with the help of a three-dimensional radiation-magneto-hydrodynamic code.

Cosmos Redshift 7 is an Active Black Hole

DOE PAGES

Smidt, Joseph Michael; Wiggins, Brandon Kerry; Johnson, Jarrett L.

2016-09-14

We present the first ab initio cosmological simulations of a CR7-like object which approximately reproduce the observed line widths and strengths. In our model, CR7 is powered by a massive (3:23 107 M ) black hole (BH) the accretion rate of which varies between ' 0.25 and ' 0.9 times the Eddington rate on timescales as short as 103 yr. Our model takes into account multi-dimensional effects, X-ray feedback, secondary ionizations and primordial chemistry. We estimate Ly- line widths by post-processing simulation output with Monte Carlo radiative transfer and calculate emissivity contributions from radiative recombination and collisional excitation. We findmore » the luminosities in the Lyman- and He II 1640 angstrom lines to be 5:0 10 44 and 2:4 10 43 erg s -1, respectively, in agreement with the observed values of > 8:3 10 43 and 2:0 10 43 erg s -1. We also find that the black hole heats the halo and renders it unable to produce stars as required to keep the halo metal free. These results demonstrate the viability of the BH hypothesis for CR7 in a cosmological context. Assuming the BH mass and accretion rate that we find, we estimate the synchrotron luminosity of CR7 to be P ' 10 40 - 10 41 erg s -1, which is sufficiently luminous to be observed in Jy observations and would discriminate this scenario from one where the luminosity is driven by Population III stars.« less

Gas filled panel insulation

DOEpatents

Griffith, Brent T.; Arasteh, Dariush K.; Selkowitz, Stephen E.

1993-01-01

A structural or flexible highly insulative panel which may be translucent, is formed from multi-layer polymeric material in the form of an envelope surrounding a baffle. The baffle is designed so as to minimize heat transfer across the panel, by using material which forms substantially closed spaces to suppress convection of the low conductivity gas fill. At least a portion of the baffle carries a low emissivity surface for suppression of infrared radiation.

Polarization transfer in x-ray transitions due to photoionization in highly charged copper-like ions

NASA Astrophysics Data System (ADS)

Ma, Kun; Chen, Zhan-Bin; Xie, Lu-You; Dong, Chen-Zhong

2018-02-01

Using the density matrix theory and the multi-configuration Dirac-Fock method, the 3{d}3/2 subshell photoionization of highly charged ions is studied, together with their subsequent radiative decay. The effects of polarization transfer on the linear polarization and angular distribution of the 3{d}94{s}2{}2{D}3/2\\to 3{d}104p{}2{P}1/2 characteristic line photoemission for selected Cu-like Zn+, Ba27+, {{{W}}}45+, and {{{U}}}63+ ions are investigated. Our results show that the polarization transfer, arising from the originally polarized incident light, may lead to a considerable change in the alignment parameters and the polarization properties of the radiation, the character of which is highly sensitive to the initial photon polarization, yet virtually independent of the photon energy. These characteristics are very similar to those of the electron bremsstrahlung process reported by Märtin et al (2012 Phys. Rev. Lett. 108 264801). The present results are compared with available experimental results and show a good quantitative agreement.

Development of a new EMP code at LANL

NASA Astrophysics Data System (ADS)

Colman, J. J.; Roussel-Dupré, R. A.; Symbalisty, E. M.; Triplett, L. A.; Travis, B. J.

2006-05-01

A new code for modeling the generation of an electromagnetic pulse (EMP) by a nuclear explosion in the atmosphere is being developed. The source of the EMP is the Compton current produced by the prompt radiation (γ-rays, X-rays, and neutrons) of the detonation. As a first step in building a multi- dimensional EMP code we have written three kinetic codes, Plume, Swarm, and Rad. Plume models the transport of energetic electrons in air. The Plume code solves the relativistic Fokker-Planck equation over a specified energy range that can include ~ 3 keV to 50 MeV and computes the resulting electron distribution function at each cell in a two dimensional spatial grid. The energetic electrons are allowed to transport, scatter, and experience Coulombic drag. Swarm models the transport of lower energy electrons in air, spanning 0.005 eV to 30 keV. The swarm code performs a full 2-D solution to the Boltzmann equation for electrons in the presence of an applied electric field. Over this energy range the relevant processes to be tracked are elastic scattering, three body attachment, two body attachment, rotational excitation, vibrational excitation, electronic excitation, and ionization. All of these occur due to collisions between the electrons and neutral bodies in air. The Rad code solves the full radiation transfer equation in the energy range of 1 keV to 100 MeV. It includes effects of photo-absorption, Compton scattering, and pair-production. All of these codes employ a spherical coordinate system in momentum space and a cylindrical coordinate system in configuration space. The "z" axis of the momentum and configuration spaces is assumed to be parallel and we are currently also assuming complete spatial symmetry around the "z" axis. Benchmarking for each of these codes will be discussed as well as the way forward towards an integrated modern EMP code.

Models for Type Ia Supernovae and Related Astrophysical Transients

NASA Astrophysics Data System (ADS)

Röpke, Friedrich K.; Sim, Stuart A.

2018-06-01

We give an overview of recent efforts to model Type Ia supernovae and related astrophysical transients resulting from thermonuclear explosions in white dwarfs. In particular we point out the challenges resulting from the multi-physics multi-scale nature of the problem and discuss possible numerical approaches to meet them in hydrodynamical explosion simulations and radiative transfer modeling. We give examples of how these methods are applied to several explosion scenarios that have been proposed to explain distinct subsets or, in some cases, the majority of the observed events. In case we comment on some of the successes and shortcoming of these scenarios and highlight important outstanding issues.

Spatial and Temporal Signatures of Flux Transfer Events in Global Simulations of Magnetopause Dynamics

NASA Technical Reports Server (NTRS)

Kuznetsova, Maria M.; Sibeck, David Gary; Hesse, Michael; Berrios, David; Rastaetter, Lutz; Toth, Gabor; Gombosi, Tamas I.

2011-01-01

Flux transfer events (FTEs) were originally identified by transient bipolar variations of the magnetic field component normal to the nominal magnetopause centered on enhancements in the total magnetic field strength. Recent Cluster and THEMIS multi-point measurements provided a wide range of signatures that are interpreted as evidence for FTE passage (e.g., crater FTE's, traveling magnetic erosion regions). We use the global magnetohydrodynamic (MHD) code BATS-R-US developed at the University of Michigan to model the global three-dimensional structure and temporal evolution of FTEs during multi-spacecraft magnetopause crossing events. Comparison of observed and simulated signatures and sensitivity analysis of the results to the probe location will be presented. We will demonstrate a variety of observable signatures in magnetic field profile that depend on space probe location with respect to the FTE passage. The global structure of FTEs will be illustrated using advanced visualization tools developed at the Community Coordinated Modeling Center

A Zero Dimensional Time-Dependent Model of High-Pressure Ablative Capillary Discharge (Preprint)

DTIC Science & Technology

2008-06-01

comprehensive model of capillary discharge is important to understand the physics and engineering aspects of the capillary discharge thruster. A schematic...investigators since the mid-1980s see 1-11 and references therein, satisfy both of these conditions well. These studies investigated the dynamics of high...is a comprehensive description of the radiative heat transfer in the capillary discharge. It is worth noting that in other types of capillary

TRUST. I. A 3D externally illuminated slab benchmark for dust radiative transfer

NASA Astrophysics Data System (ADS)

Gordon, K. D.; Baes, M.; Bianchi, S.; Camps, P.; Juvela, M.; Kuiper, R.; Lunttila, T.; Misselt, K. A.; Natale, G.; Robitaille, T.; Steinacker, J.

2017-07-01

Context. The radiative transport of photons through arbitrary three-dimensional (3D) structures of dust is a challenging problem due to the anisotropic scattering of dust grains and strong coupling between different spatial regions. The radiative transfer problem in 3D is solved using Monte Carlo or Ray Tracing techniques as no full analytic solution exists for the true 3D structures. Aims: We provide the first 3D dust radiative transfer benchmark composed of a slab of dust with uniform density externally illuminated by a star. This simple 3D benchmark is explicitly formulated to provide tests of the different components of the radiative transfer problem including dust absorption, scattering, and emission. Methods: The details of the external star, the slab itself, and the dust properties are provided. This benchmark includes models with a range of dust optical depths fully probing cases that are optically thin at all wavelengths to optically thick at most wavelengths. The dust properties adopted are characteristic of the diffuse Milky Way interstellar medium. This benchmark includes solutions for the full dust emission including single photon (stochastic) heating as well as two simplifying approximations: One where all grains are considered in equilibrium with the radiation field and one where the emission is from a single effective grain with size-distribution-averaged properties. A total of six Monte Carlo codes and one Ray Tracing code provide solutions to this benchmark. Results: The solution to this benchmark is given as global spectral energy distributions (SEDs) and images at select diagnostic wavelengths from the ultraviolet through the infrared. Comparison of the results revealed that the global SEDs are consistent on average to a few percent for all but the scattered stellar flux at very high optical depths. The image results are consistent within 10%, again except for the stellar scattered flux at very high optical depths. The lack of agreement between different codes of the scattered flux at high optical depths is quantified for the first time. Convergence tests using one of the Monte Carlo codes illustrate the sensitivity of the solutions to various model parameters. Conclusions: We provide the first 3D dust radiative transfer benchmark and validate the accuracy of this benchmark through comparisons between multiple independent codes and detailed convergence tests.

Status of a standard for neutron skyshine calculation and measurement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Westfall, R.M.; Wright, R.Q.; Greenborg, J.

1990-01-01

An effort has been under way for several years to prepare a draft standard, ANS-6.6.2, Calculation and Measurement of Direct and Scattered Neutron Radiation from Contained Sources Due to Nuclear Power Operations. At the outset, the work group adopted a three-phase study involving one-dimensional analyses, a measurements program, and multi-dimensional analyses. Of particular interest are the neutron radiation levels associated with dry-fuel storage at reactor sites. The need for dry storage has been investigated for various scenarios of repository and monitored retrievable storage (MRS) facilities availability with the waste stream analysis model. The concern is with long-term integrated, low-level dosesmore » at long distances from a multiplicity of sources. To evaluate the conservatism associated with one-dimensional analyses, the work group has specified a series of simple problems. Sources as a function of fuel exposure were determined for a Westinghouse 17 x 17 pressurized water reactor assembly with the ORIGEN-S module of the SCALE system. The energy degradation of the 35 GWd/ton U sources was determined for two generic designs of dry-fuel storage casks.« less

Increasing of Urban Radiation due to Climate Change and Reduction Strategy using Vegetation

NASA Astrophysics Data System (ADS)

Park, C.; Lee, D.; Heo, H. K.; Ahn, S.

2017-12-01

Urban Heat Island (UHI) which means urban air temperature is higher than suburban area is one of the most important environmental issues in Urban. High density of buildings and high ratio of impervious surfaces increases the radiation fluxes in urban canopy. Furthermore, climate change is expected to make UHI even more seriously in the future. Increased irradiation and air temperature cause high amount of short wave and long wave radiation, respectively. This increases net radiation negatively affects heat condition of pedestrian. UHI threatens citizen's health by increasing violence and heat related diseases. For this reason, understanding how much urban radiation will increase in the future, and exploring radiation reduction strategies is important for reducing UHI. In this research, we aim to reveal how the radiation flux in the urban canyon will change as the climate change and determine how much of urban vegetation will be needed to cover this degradation. The study area is a commercial district in Seoul where highly populated area. Due to the high density of buildings and lack of urban vegetation, this area has a poor thermal condition in summer. In this research, we simulate the radiation flux on the ground using multi-layer urban canopy model. Unlike conventionally used urban canopy model to simulate radiation transfer using vertically single layer, the multi-layer model we used here, enables to consider the vertical heterogeneous of buildings and urban vegetation. As a result, net radiation of urban ground will be increase 2.1 W/m² in the 2050s and 2.7 W/m² in the 2100s. And to prevent the increase of radiation, it is revealed that the urban vegetation should by increased by 10%. This research will be valuable in establishing greening planning as a strategy to reduce UHI effect.

Multi-GPU configuration of 4D intensity modulated radiation therapy inverse planning using global optimization

NASA Astrophysics Data System (ADS)

Hagan, Aaron; Sawant, Amit; Folkerts, Michael; Modiri, Arezoo

2018-01-01

We report on the design, implementation and characterization of a multi-graphic processing unit (GPU) computational platform for higher-order optimization in radiotherapy treatment planning. In collaboration with a commercial vendor (Varian Medical Systems, Palo Alto, CA), a research prototype GPU-enabled Eclipse (V13.6) workstation was configured. The hardware consisted of dual 8-core Xeon processors, 256 GB RAM and four NVIDIA Tesla K80 general purpose GPUs. We demonstrate the utility of this platform for large radiotherapy optimization problems through the development and characterization of a parallelized particle swarm optimization (PSO) four dimensional (4D) intensity modulated radiation therapy (IMRT) technique. The PSO engine was coupled to the Eclipse treatment planning system via a vendor-provided scripting interface. Specific challenges addressed in this implementation were (i) data management and (ii) non-uniform memory access (NUMA). For the former, we alternated between parameters over which the computation process was parallelized. For the latter, we reduced the amount of data required to be transferred over the NUMA bridge. The datasets examined in this study were approximately 300 GB in size, including 4D computed tomography images, anatomical structure contours and dose deposition matrices. For evaluation, we created a 4D-IMRT treatment plan for one lung cancer patient and analyzed computation speed while varying several parameters (number of respiratory phases, GPUs, PSO particles, and data matrix sizes). The optimized 4D-IMRT plan enhanced sparing of organs at risk by an average reduction of 26% in maximum dose, compared to the clinical optimized IMRT plan, where the internal target volume was used. We validated our computation time analyses in two additional cases. The computation speed in our implementation did not monotonically increase with the number of GPUs. The optimal number of GPUs (five, in our study) is directly related to the hardware specifications. The optimization process took 35 min using 50 PSO particles, 25 iterations and 5 GPUs.

Multi-GPU configuration of 4D intensity modulated radiation therapy inverse planning using global optimization.

PubMed

Hagan, Aaron; Sawant, Amit; Folkerts, Michael; Modiri, Arezoo

2018-01-16

We report on the design, implementation and characterization of a multi-graphic processing unit (GPU) computational platform for higher-order optimization in radiotherapy treatment planning. In collaboration with a commercial vendor (Varian Medical Systems, Palo Alto, CA), a research prototype GPU-enabled Eclipse (V13.6) workstation was configured. The hardware consisted of dual 8-core Xeon processors, 256 GB RAM and four NVIDIA Tesla K80 general purpose GPUs. We demonstrate the utility of this platform for large radiotherapy optimization problems through the development and characterization of a parallelized particle swarm optimization (PSO) four dimensional (4D) intensity modulated radiation therapy (IMRT) technique. The PSO engine was coupled to the Eclipse treatment planning system via a vendor-provided scripting interface. Specific challenges addressed in this implementation were (i) data management and (ii) non-uniform memory access (NUMA). For the former, we alternated between parameters over which the computation process was parallelized. For the latter, we reduced the amount of data required to be transferred over the NUMA bridge. The datasets examined in this study were approximately 300 GB in size, including 4D computed tomography images, anatomical structure contours and dose deposition matrices. For evaluation, we created a 4D-IMRT treatment plan for one lung cancer patient and analyzed computation speed while varying several parameters (number of respiratory phases, GPUs, PSO particles, and data matrix sizes). The optimized 4D-IMRT plan enhanced sparing of organs at risk by an average reduction of [Formula: see text] in maximum dose, compared to the clinical optimized IMRT plan, where the internal target volume was used. We validated our computation time analyses in two additional cases. The computation speed in our implementation did not monotonically increase with the number of GPUs. The optimal number of GPUs (five, in our study) is directly related to the hardware specifications. The optimization process took 35 min using 50 PSO particles, 25 iterations and 5 GPUs.

Accessing Multi-Dimensional Images and Data Cubes in the Virtual Observatory

NASA Astrophysics Data System (ADS)

Tody, Douglas; Plante, R. L.; Berriman, G. B.; Cresitello-Dittmar, M.; Good, J.; Graham, M.; Greene, G.; Hanisch, R. J.; Jenness, T.; Lazio, J.; Norris, P.; Pevunova, O.; Rots, A. H.

2014-01-01

Telescopes across the spectrum are routinely producing multi-dimensional images and datasets, such as Doppler velocity cubes, polarization datasets, and time-resolved “movies.” Examples of current telescopes producing such multi-dimensional images include the JVLA, ALMA, and the IFU instruments on large optical and near-infrared wavelength telescopes. In the near future, both the LSST and JWST will also produce such multi-dimensional images routinely. High-energy instruments such as Chandra produce event datasets that are also a form of multi-dimensional data, in effect being a very sparse multi-dimensional image. Ensuring that the data sets produced by these telescopes can be both discovered and accessed by the community is essential and is part of the mission of the Virtual Observatory (VO). The Virtual Astronomical Observatory (VAO, http://www.usvao.org/), in conjunction with its international partners in the International Virtual Observatory Alliance (IVOA), has developed a protocol and an initial demonstration service designed for the publication, discovery, and access of arbitrarily large multi-dimensional images. The protocol describing multi-dimensional images is the Simple Image Access Protocol, version 2, which provides the minimal set of metadata required to characterize a multi-dimensional image for its discovery and access. A companion Image Data Model formally defines the semantics and structure of multi-dimensional images independently of how they are serialized, while providing capabilities such as support for sparse data that are essential to deal effectively with large cubes. A prototype data access service has been deployed and tested, using a suite of multi-dimensional images from a variety of telescopes. The prototype has demonstrated the capability to discover and remotely access multi-dimensional data via standard VO protocols. The prototype informs the specification of a protocol that will be submitted to the IVOA for approval, with an operational data cube service to be delivered in mid-2014. An associated user-installable VO data service framework will provide the capabilities required to publish VO-compatible multi-dimensional images or data cubes.

Near-field heat transfer between graphene/hBN multilayers

NASA Astrophysics Data System (ADS)

Zhao, Bo; Guizal, Brahim; Zhang, Zhuomin M.; Fan, Shanhui; Antezza, Mauro

2017-06-01

We study the radiative heat transfer between multilayer structures made by a periodic repetition of a graphene sheet and a hexagonal boron nitride (hBN) slab. Surface plasmons in a monolayer graphene can couple with hyperbolic phonon polaritons in a single hBN film to form hybrid polaritons that can assist photon tunneling. For periodic multilayer graphene/hBN structures, the stacked metallic/dielectric array can give rise to a further effective hyperbolic behavior, in addition to the intrinsic natural hyperbolic behavior of hBN. The effective hyperbolicity can enable more hyperbolic polaritons that enhance the photon tunneling and hence the near-field heat transfer. However, the hybrid polaritons on the surface, i.e., surface plasmon-phonon polaritons, dominate the near-field heat transfer between multilayer structures when the topmost layer is graphene. The effective hyperbolic regions can be well predicted by the effective medium theory (EMT), thought EMT fails to capture the hybrid surface polaritons and results in a heat transfer rate much lower compared to the exact calculation. The chemical potential of the graphene sheets can be tuned through electrical gating and results in an additional modulation of the heat transfer. We found that the near-field heat transfer between multilayer structures does not increase monotonously with the number of layers in the stack, which provides a way to control the heat transfer rate by the number of graphene layers in the multilayer structure. The results may benefit the applications of near-field energy harvesting and radiative cooling based on hybrid polaritons in two-dimensional materials.

Heat transfer in thermal barrier coated rods with circumferential and radial temperature gradients

NASA Astrophysics Data System (ADS)

Chung, B. T. F.; Kermani, M. M.; Braun, M. J.; Padovan, J.; Hendricks, R.

1984-06-01

To study the heat transfer in ceramic coatings applied to the heated side of internally cooled hot section components of the gas turbine engine, a mathematical model is developed for the thermal response of plasma-sprayed ZrO2-Y2O3 ceramic materials with a Ni-Cr-AL-Y bond coat on a Rene 41 rod substrate subject to thermal cycling. This multilayered cylinder with temperature dependent thermal properties is heated in a cross-flow by a high velocity flame and then cooled by ambient air. Due to high temperature and high velocity of the flame, both gas radiation and forced convection are taken into consideration. Furthermore, the local turbulent heat transfer coefficient is employed which varies with angular position as well as the surface temperature. The transient two-dimensional (heat transfer along axial direction is neglected) temperature distribution of the composite cylinder is determined numerically.

Heat transfer in thermal barrier coated rods with circumferential and radial temperature gradients

NASA Technical Reports Server (NTRS)

Chung, B. T. F.; Kermani, M. M.; Braun, M. J.; Padovan, J.; Hendricks, R.

1984-01-01

To study the heat transfer in ceramic coatings applied to the heated side of internally cooled hot section components of the gas turbine engine, a mathematical model is developed for the thermal response of plasma-sprayed ZrO2-Y2O3 ceramic materials with a Ni-Cr-AL-Y bond coat on a Rene 41 rod substrate subject to thermal cycling. This multilayered cylinder with temperature dependent thermal properties is heated in a cross-flow by a high velocity flame and then cooled by ambient air. Due to high temperature and high velocity of the flame, both gas radiation and forced convection are taken into consideration. Furthermore, the local turbulent heat transfer coefficient is employed which varies with angular position as well as the surface temperature. The transient two-dimensional (heat transfer along axial direction is neglected) temperature distribution of the composite cylinder is determined numerically.

Influence of aerosols, clouds, and sunglint on polarization spectra of Earthshine

NASA Astrophysics Data System (ADS)

Emde, Claudia; Buras-Schnell, Robert; Sterzik, Michael; Bagnulo, Stefano

2017-08-01

Context. Ground-based observations of the Earthshine, I.e., the light scattered by Earth to the Moon, and then reflected back to Earth, simulate space observations of our planet and represent a powerful benchmark for the studies of Earth-like planets. Earthshine spectra are strongly linearly polarized, owing to scattering by molecules and small particles in the atmosphere of the Earth and surface reflection, and may allow us to measure global atmospheric and surface properties of planet Earth. Aims: We aim to interpret already published spectropolarimetric observations of the Earthshine by comparing them with new radiative transfer model simulations including a fully realistic three-dimensional (3D) surface-atmosphere model for planet Earth. Methods: We used the highly advanced Monte Carlo radiative transfer model MYSTIC to simulate polarized radiative transfer in the atmosphere of the Earth without approximations regarding the geometry, taking into account the polarization from surface reflection and multiple scattering by molecules, aerosol particles, cloud droplets, and ice crystals. Results: We have shown that Earth spectropolarimetry is highly sensitive to all these input parameters, and we have presented simulations of a fully realistic Earth atmosphere-surface model including 3D cloud fields and two-dimensional (2D) surface property maps. Our modeling results show that scattering in high ice water clouds and reflection from the ocean surface are crucial to explain the continuum polarization at longer wavelengths as has been reported in Earthshine observations taken at the Very Large Telescope in 2011 (3.8% and 6.6% at 800 nm, depending on which part of Earth was visible from the Moon at the time of the observations). We found that the relatively high degree of polarization of 6.6% can be attributed to light reflected by the ocean surface in the sunglint region. High ice-water clouds reduce the amount of absorption in the O2A band and thus explain the weak O2A band feature in the observations.

A Phase II Study of Submandibular Gland Transfer Prior to Radiation for Prevention of Radiation-Induced Xerostomia in Head and Neck Cancer (Rtog 0244)s

PubMed Central

Jha, Naresh; Harris, Jonathan; Seikaly, Hadi; Jacobs, John R.; McEwan, AJB.; Thomas Robbins, K.; Grecula, John; Sharma, Anand K.; Ang, K. Kian

2012-01-01

Purpose We report the results of a phase II study to determine reproducibility of surgical technique of submandibular salivary gland transfer (SGT) for prevention of radiation (XRT) induced xerostomia in a multi-institutional setting and to assess severity of xerostomia. Methods and Materials Eligible patients had surgery for primary, neck dissection, and SGT followed by XRT during which the transferred salivary gland was shielded. IMRT, amifostine, and pilocarpine were not allowed, but postoperative chemotherapy was allowed. Each operation was reviewed by two and radiation by one reviewer. If 13 or more (out of 43) were “not per protocol”, then technique would be considered not reproducible as per study design. The secondary endpoint was the rate of acute xerostomia, Grade 2 or higher and a rate of ≤ 51% was acceptable. Results 44 of the total 49 patients were analyzable: male (81.8%), oropharynx (63.6%), stage IV (61.4%), median age 56.5 years. SGT was “per protocol” or with acceptable variation in 34 patients (77.3%) and XRT in 79.5%. 9 patients (20.9%) developed grade II acute xerostomia; 2 had grade 0 -1 xerostomia (4.7%) but started on amifostine/pilocarpine. These 11 patients (25.6%) were considered failures for the xerostomia endpoint. 13 patients have died; median follow-up for 31 surviving patients is 2.9 years. Two-year overall and disease-free survival rates are 76.4% and 71.7%, respectively. Conclusions the technique of submandibular salivary gland transfer procedure is reproducible in a multicenter setting. Seventy-four percent of patients had prevention of XRT induced acute xerostomia. PMID:22541957

One-dimensional non-LTE time-dependent radiative transfer of an He-detonation model and the connection to faint and fast-decaying supernovae

NASA Astrophysics Data System (ADS)

Dessart, Luc; Hillier, D. John

2015-02-01

We present non-LTE (non-Local-Thermodynamic-Equilibrium) time-dependent radiative transfer simulations for ejecta produced by the detonation of a helium shell at the surface of a low-mass carbon/oxygen white dwarf (WD). This mechanism is one possible origin for supernovae (SNe) with faint and fast-decaying light curves, such as .Ia SNe and Ca-rich transients. Our initial ejecta conditions at 1 d are given by the 0.18 B explosion model COp45HEp2 of Waldman et al. The 0.2 M⊙ ejecta initially contains 0.11 M⊙ of He, 0.03 M⊙ of Ca, and 0.03 M⊙ of Ti. We obtain an ˜ 5 d rise to a bolometric maximum of 3.59 × 1041 erg s-1, primarily powered by 48V decay. Multi-band light curves show distinct morphologies, with a rise to maximum magnitude (-14.3 to -16.7 mag) that varies between 3 to 9 d from the U to the K bands. Near-IR light curves show no secondary maximum. Because of the presence of both He I and Si II lines at early times we obtain a hybrid Type Ia/Ib classification. During the photospheric phase line blanketing is caused primarily by Ti II. At nebular times, the spectra show strong Ca II lines in the optical (but no [O I] 6300-6364 Å emission), and Ti II in the near-IR. Overall, these results match qualitatively the very disparate properties of .Ia SNe and Ca-rich transients. Although the strong Ti II blanketing and red colours that we predict are rarely observed, they are seen, for example, in OGLE-2013- SN-079. Furthermore, we obtain a faster light-curve evolution than, for example, PTF10iuv, indicating an ejecta mass >0.2 M⊙. An alternate scenario may be the merger of two WDs, one or both composed of He.

High Vertically Resolved Atmospheric and Surface/Cloud Parameters Retrieved with Infrared Atmospheric Sounding Interferometer (IASI)

NASA Technical Reports Server (NTRS)

Zhou, Daniel K.; Liu, Xu; Larar, Allen M.; Smith, WIlliam L.; Taylor, Jonathan P.; Schluessel, Peter; Strow, L. Larrabee; Mango, Stephen A.

2008-01-01

The Joint Airborne IASI Validation Experiment (JAIVEx) was conducted during April 2007 mainly for validation of the IASI on the MetOp satellite. IASI possesses an ultra-spectral resolution of 0.25/cm and a spectral coverage from 645 to 2760/cm. Ultra-spectral resolution infrared spectral radiance obtained from near nadir observations provide atmospheric, surface, and cloud property information. An advanced retrieval algorithm with a fast radiative transfer model, including cloud effects, is used for atmospheric profile and cloud parameter retrieval. This physical inversion scheme has been developed, dealing with cloudy as well as cloud-free radiance observed with ultraspectral infrared sounders, to simultaneously retrieve surface, atmospheric thermodynamic, and cloud microphysical parameters. A fast radiative transfer model, which applies to the cloud-free and/or clouded atmosphere, is used for atmospheric profile and cloud parameter retrieval. A one-dimensional (1-d) variational multi-variable inversion solution is used to improve an iterative background state defined by an eigenvector-regression-retrieval. The solution is iterated in order to account for non-linearity in the 1-d variational solution. It is shown that relatively accurate temperature and moisture retrievals are achieved below optically thin clouds. For optically thick clouds, accurate temperature and moisture profiles down to cloud top level are obtained. For both optically thin and thick cloud situations, the cloud top height can be retrieved with relatively high accuracy (i.e., error < 1 km). Preliminary retrievals of atmospheric soundings, surface properties, and cloud optical/microphysical properties with the IASI observations are obtained and presented. These retrievals will be further inter-compared with those obtained from airborne FTS system, such as the NPOESS Airborne Sounder Testbed - Interferometer (NAST-I), dedicated dropsondes, radiosondes, and ground based Raman Lidar. The capabilities of satellite ultra-spectral sounder such as the IASI are investigated indicating a high vertical structure of atmosphere is retrieved.

Coherent Terahertz Radiation from Multiple Electron Beams Excitation within a Plasmonic Crystal-like structure.

PubMed

Zhang, Yaxin; Zhou, Yucong; Gang, Yin; Jiang, Guili; Yang, Ziqiang

2017-01-23

Coherent terahertz radiation from multiple electron beams excitation within a plasmonic crystal-like structure (a three-dimensional holes array) which is composed of multiple stacked layers with 3 × 3 subwavelength holes array has been proposed in this paper. It has been found that in the structure the electromagnetic fields in each hole can be coupled with one another to construct a composite mode with strong field intensity. Therefore, the multiple electron beams injection can excite and efficiently interact with such mode. Meanwhile, the coupling among the electron beams is taken place during the interaction so that a very strong coherent terahertz radiation with high electron conversion efficiency can be generated. Furthermore, due to the coupling, the starting current density of this mechanism is much lower than that of traditional electron beam-driven terahertz sources. This multi-beam radiation system may provide a favorable way to combine photonics structure with electronics excitation to generate middle, high power terahertz radiation.

Coherent Terahertz Radiation from Multiple Electron Beams Excitation within a Plasmonic Crystal-like structure

PubMed Central

Zhang, Yaxin; Zhou, Yucong; Gang, Yin; Jiang, Guili; Yang, Ziqiang

2017-01-01

Coherent terahertz radiation from multiple electron beams excitation within a plasmonic crystal-like structure (a three-dimensional holes array) which is composed of multiple stacked layers with 3 × 3 subwavelength holes array has been proposed in this paper. It has been found that in the structure the electromagnetic fields in each hole can be coupled with one another to construct a composite mode with strong field intensity. Therefore, the multiple electron beams injection can excite and efficiently interact with such mode. Meanwhile, the coupling among the electron beams is taken place during the interaction so that a very strong coherent terahertz radiation with high electron conversion efficiency can be generated. Furthermore, due to the coupling, the starting current density of this mechanism is much lower than that of traditional electron beam-driven terahertz sources. This multi-beam radiation system may provide a favorable way to combine photonics structure with electronics excitation to generate middle, high power terahertz radiation. PMID:28112234

Thermal Analysis and Design of Multi-layer Insulation for Re-entry Aerodynamic Heating

NASA Technical Reports Server (NTRS)

Daryabeigi, Kamran

2001-01-01

The combined radiation/conduction heat transfer in high-temperature multi-layer insulations was modeled using a finite volume numerical model. The numerical model was validated by comparison with steady-state effective thermal conductivity measurements, and by transient thermal tests simulating re-entry aerodynamic heating conditions. A design of experiments technique was used to investigate optimum design of multi-layer insulations for re-entry aerodynamic heating. It was found that use of 2 mm foil spacing and locating the foils near the hot boundary with the top foil 2 mm away from the hot boundary resulted in the most effective insulation design. A 76.2 mm thick multi-layer insulation using 1, 4, or 16 foils resulted in 2.9, 7.2, or 22.2 percent mass per unit area savings compared to a fibrous insulation sample at the same thickness, respectively.

Some applications of the multi-dimensional fractional order for the Riemann-Liouville derivative

NASA Astrophysics Data System (ADS)

Ahmood, Wasan Ajeel; Kiliçman, Adem

2017-01-01

In this paper, the aim of this work is to study theorem for the one-dimensional space-time fractional deriative, generalize some function for the one-dimensional fractional by table represents the fractional Laplace transforms of some elementary functions to be valid for the multi-dimensional fractional Laplace transform and give the definition of the multi-dimensional fractional Laplace transform. This study includes that, dedicate the one-dimensional fractional Laplace transform for functions of only one independent variable and develop of the one-dimensional fractional Laplace transform to multi-dimensional fractional Laplace transform based on the modified Riemann-Liouville derivative.

An exact solution on unsteady MHD free convection chemically reacting silver nanofluid flow past an exponentially accelerated vertical plate through porous medium

NASA Astrophysics Data System (ADS)

Kumaresan, E.; Vijaya Kumar, A. G.; Rushi Kumar, B.

2017-11-01

This article studies, an exact solution of unsteady MHD free convection boundary-layer flow of a silver nanofluid past an exponentially accelerated moving vertical plate through aporous medium in the presence of thermal radiation, transverse applied amagnetic field, radiation absorption and Heat generation or absorption with chemical reaction are investigated theoretically. We consider nanofluids contain spherical shaped nanoparticle of silverwith a nanoparticle volume concentration range smaller than or equal to 0.04. This phenomenon is modeled in the form of partial differential equations with initial boundary conditions. Some suitable dimensional variables are introduced. The corresponding dimensionless equations with boundary conditions are solved by using Laplace transform technique. The exact solutions for velocity, energy, and species are obtained, also the corresponding numerical values of nanofluid velocity, temperature and concentration profiles are represented graphically. The expressions for skin friction coefficient, the rate of heat transfer and mass transfer are derived. The present study finds applications involving heat transfer, enhancement of thermal conductivity and other applications like transportation, industrial cooling applications, heating buildings and reducing pollution, energy applications and solar absorption. The effect of heat transfer is found to be more pronounced in a silver-water nanofluid than in the other nanofluids.

Generation of shock waves and formation of craters in a solid material irradiated by a short laser pulse

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gus'kov, Sergei Yu; Borodziuk, S; Kasperczuk, A

2004-11-30

The results of investigations are presented which are concerned with laser radiation absorption in a target, the plasma state of its ablated material, the energy transfer to the solid target material, the characteristics of the shock wave and craters on the target surface. The investigation involved irradiation of a planar target by a subnanosecond plasma-producing laser pulse. The experiments were carried out with massive aluminium targets using the PALS iodine laser, whose pulse duration (0.4 ns) was much shorter than the shock wave attenuation and on-target crater formation times (50-200 ns). The investigations were conducted for a laser radiation energymore » of 100 J at two wavelengths of 0.438 and 1.315 {mu}m. For a given pulse energy, the irradiation intensity was varied in a broad range (10{sup 13}-10{sup 16} W cm{sup -2}) by varying the radius of the laser beam. The efficiency of laser radiation-to-shock energy transfer was determined as a function of the intensity and wavelength of laser radiation; also determined were the characteristics of the plasma plume and the shock wave propagating in the solid target, including the experimental conditions under which two-dimensional effects are highly significant. (invited paper)« less

Venus climate stability and volcanic resurfacing rates

NASA Technical Reports Server (NTRS)

Bullock, M. A.; Grinspoon, D. H.; Pollack, J. B.

1994-01-01

The climate of Venus is to a large degree controlled by the radiative properties of its massive atmosphere. In addition, outgassing due to volcanic activity, exospheric escape processes, and surface/atmosphere interactions may all be important in moderating the abundances of atmospheric CO2 and other volatiles. We have developed an evolutionary climate model for Venus using a systems approach that emphasizes feedbacks between elements in the climate system. Modules for atmospheric radiative transfer, surface/atmosphere interactions, tropospheric chemistry, and exospheric escape processes have so far been developed. Climate feedback loops result from interconnections between modules, in the form of the environmental parameters pressure, temperature, and atmospheric mixing ratios. The radiative transfer module has been implemented by using Rosseland mean opacities in a one dimensional grey radiative-convective model. The model has been solved for the static (time independent) case to determine climate equilibrium points. The dynamics of the model have also been explored by employing reaction/diffusion kinetics for possible surface atmosphere heterogeneous reactions over geologic timescales. It was found that under current conditions, the model predicts that the climate of Venus is at or near an unstable equilibrium point. The effects of constant rate volcanism and corresponding exsolution of volatiles on the stability of the climate model were also explored.

Microclimatic modeling of the desert in the United Arab Emirates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khalil, A.K.; Abdrabboh, M.A.; Kamel, K.A.

1996-10-01

The present study is concerned with the prediction of the weather parameters in the microclimate layer (less than 2 m above the ground surface) in the desert and sparsely vegetated areas in the United Arab Emirates. A survey was made of the weather data in these regions including solar radiation, wind speed, screen temperatures and relative humidity. Additionally, wind speed data were obtained at heights below two meters and surface albedo was recorded for various soil and vegetation conditions. A survey was also carried out for the different plant species in various areas of the U.A.E. Data on soil andmore » surface temperature were then analyzed. An energy balance model was formulated including incident short- and long-wave length radiation between earth and sky, convective heat transfer to/from earth surface, surface reflection of solar radiation and soil/plant evapotranspiration. An explicit one dimensional finite difference scheme was adapted to solve the resulting algebraic finite difference equations. The equation for surface nodes included thermal radiation as well as convection effects. The heat transfer coefficient was evaluated on the basis of wind speed and surface roughness at the site where the energy balance was set. Theoretical predictions of air and soil temperatures were accordingly compared to experimental measurements in selected sites, where reasonable agreements were observed.« less

The Extraction of One-Dimensional Flow Properties from Multi-Dimensional Data Sets

NASA Technical Reports Server (NTRS)

Baurle, Robert A.; Gaffney, Richard L., Jr.

2007-01-01

The engineering design and analysis of air-breathing propulsion systems relies heavily on zero- or one-dimensional properties (e.g. thrust, total pressure recovery, mixing and combustion efficiency, etc.) for figures of merit. The extraction of these parameters from experimental data sets and/or multi-dimensional computational data sets is therefore an important aspect of the design process. A variety of methods exist for extracting performance measures from multi-dimensional data sets. Some of the information contained in the multi-dimensional flow is inevitably lost when any one-dimensionalization technique is applied. Hence, the unique assumptions associated with a given approach may result in one-dimensional properties that are significantly different than those extracted using alternative approaches. The purpose of this effort is to examine some of the more popular methods used for the extraction of performance measures from multi-dimensional data sets, reveal the strengths and weaknesses of each approach, and highlight various numerical issues that result when mapping data from a multi-dimensional space to a space of one dimension.

The Art of Extracting One-Dimensional Flow Properties from Multi-Dimensional Data Sets

NASA Technical Reports Server (NTRS)

Baurle, R. A.; Gaffney, R. L.

2007-01-01

The engineering design and analysis of air-breathing propulsion systems relies heavily on zero- or one-dimensional properties (e:g: thrust, total pressure recovery, mixing and combustion efficiency, etc.) for figures of merit. The extraction of these parameters from experimental data sets and/or multi-dimensional computational data sets is therefore an important aspect of the design process. A variety of methods exist for extracting performance measures from multi-dimensional data sets. Some of the information contained in the multi-dimensional flow is inevitably lost when any one-dimensionalization technique is applied. Hence, the unique assumptions associated with a given approach may result in one-dimensional properties that are significantly different than those extracted using alternative approaches. The purpose of this effort is to examine some of the more popular methods used for the extraction of performance measures from multi-dimensional data sets, reveal the strengths and weaknesses of each approach, and highlight various numerical issues that result when mapping data from a multi-dimensional space to a space of one dimension.

Retrieving Biome Types from Multi-angle Spectral Data

NASA Astrophysics Data System (ADS)

Schull, M. A.; Xu, L.; Latorre, P.; Samanta, A.; Myneni, R. B.; Knyazikhin, Y.

2009-12-01

Many studies have been conducted to demonstrate the ability of multi-angle spectral data to discriminate plant dominant species. Most have employed the use of empirically based techniques, which are site specific, requires some initial training based on characteristics of known leaf and/or canopy spectra and therefore may not be extendable to operational use or adapted to changing/unknown land cover. An ancillary objective of the MISR LAI/FPAR algorithm is classification of global vegetation into biome types. The algorithm is based on the 3D radiative transfer equation. Its performance suggests that is has valid LAI retrievals and correct biome identification in about 20% of the pixels. However with a probability of about 70%, uncertainties in LAI retrievals due to biome misclassification do not exceed uncertainties in the observations. In this poster we present an approach to improve reliability of the distribution of biomes and dominant species from multi angle spectral data. The radiative transfer theory of canopy spectral invariants underlies the approach, which facilitates parameterization of the canopy bidirectional reflectance factor in terms of the leaf spectrum and two spectrally invariant and structurally varying variables - recollision and directional escape probabilities. Theoretical and empirical analyses of ground and airborne data acquired by AVIRIS, AirMISR over two sites in New England and CHRIS/PROBA over BARAX site in Spain suggest that the canopy spectral invariants convey information about canopy structure at both the macro and micro scales. These properties allow for the natural separation of biome classes based on the location of points on the total escape probability vs the proportional escape ratio log-log plane.

[A Method to Reconstruct Surface Reflectance Spectrum from Multispectral Image Based on Canopy Radiation Transfer Model].

PubMed

Zhao, Yong-guang; Ma, Ling-ling; Li, Chuan-rong; Zhu, Xiao-hua; Tang, Ling-li

2015-07-01

Due to the lack of enough spectral bands for multi-spectral sensor, it is difficult to reconstruct surface retlectance spectrum from finite spectral information acquired by multi-spectral instrument. Here, taking into full account of the heterogeneity of pixel from remote sensing image, a method is proposed to simulate hyperspectral data from multispectral data based on canopy radiation transfer model. This method first assumes the mixed pixels contain two types of land cover, i.e., vegetation and soil. The sensitive parameters of Soil-Leaf-Canopy (SLC) model and a soil ratio factor were retrieved from multi-spectral data based on Look-Up Table (LUT) technology. Then, by combined with a soil ratio factor, all the parameters were input into the SLC model to simulate the surface reflectance spectrum from 400 to 2 400 nm. Taking Landsat Enhanced Thematic Mapper Plus (ETM+) image as reference image, the surface reflectance spectrum was simulated. The simulated reflectance spectrum revealed different feature information of different surface types. To test the performance of this method, the simulated reflectance spectrum was convolved with the Landsat ETM + spectral response curves and Moderate Resolution Imaging Spectrometer (MODIS) spectral response curves to obtain the simulated Landsat ETM+ and MODIS image. Finally, the simulated Landsat ETM+ and MODIS images were compared with the observed Landsat ETM+ and MODIS images. The results generally showed high correction coefficients (Landsat: 0.90-0.99, MODIS: 0.74-0.85) between most simulated bands and observed bands and indicated that the simulated reflectance spectrum was well simulated and reliable.

Heat transfer in melt ponds with convection and radiative heating: observationally-inspired modelling

NASA Astrophysics Data System (ADS)

Wells, A.; Langton, T.; Rees Jones, D. W.; Moon, W.; Kim, J. H.; Wilkinson, J.

2016-12-01

Melt ponds have key impacts on the evolution of Arctic sea ice and summer ice melt. Small changes to the energy budget can have significant consequences, with a net heat-flux perturbation of only a few Watts per square metre sufficient to explain the thinning of sea ice over recent decades. Whilst parameterisations of melt-pond thermodynamics often assume that pond temperatures remain close to the freezing point, recent in-situ observations show more complex thermal structure with significant diurnal and synoptic variability. We here consider the energy budget of melt ponds and explore the role of internal convective heat transfer in determining the thermal structure within the pond in relatively calm conditions with low winds. We quantify the energy fluxes and temperature variability using two-dimensional direct numerical simulations of convective turbulence within a melt pond, driven by internal radiative heating and surface fluxes. Our results show that the convective flow dynamics are modulated by changes to the incoming radiative flux and sensible heat flux at the pond surface. The evolving pond surface temperature controls the outgoing longwave emissions from the pond. Hence the convective flow modifies the net energy balance of a melt pond, modulating the relative fractions of the incoming heat flux that is re-emitted to the atmosphere or transferred downward into the sea ice to drive melt.

A two-column formalism for time-dependent modelling of stellar convection. I. Description of the method

NASA Astrophysics Data System (ADS)

Stökl, A.

2008-11-01

Context: In spite of all the advances in multi-dimensional hydrodynamics, investigations of stellar evolution and stellar pulsations still depend on one-dimensional computations. This paper devises an alternative to the mixing-length theory or turbulence models usually adopted in modelling convective transport in such studies. Aims: The present work attempts to develop a time-dependent description of convection, which reflects the essential physics of convection and that is only moderately dependent on numerical parameters and far less time consuming than existing multi-dimensional hydrodynamics computations. Methods: Assuming that the most extensive convective patterns generate the majority of convective transport, the convective velocity field is described using two parallel, radial columns to represent up- and downstream flows. Horizontal exchange, in the form of fluid flow and radiation, over their connecting interface couples the two columns and allows a simple circulating motion. The main parameters of this convective description have straightforward geometrical meanings, namely the diameter of the columns (corresponding to the size of the convective cells) and the ratio of the cross-section between up- and downdrafts. For this geometrical setup, the time-dependent solution of the equations of radiation hydrodynamics is computed from an implicit scheme that has the advantage of being unaffected by the Courant-Friedrichs-Lewy time-step limit. This implementation is part of the TAPIR-Code (short for The adaptive, implicit RHD-Code). Results: To demonstrate the approach, results for convection zones in Cepheids are presented. The convective energy transport and convective velocities agree with expectations for Cepheids and the scheme reproduces both the kinetic energy flux and convective overshoot. A study of the parameter influence shows that the type of solution derived for these stars is in fact fairly robust with respect to the constitutive numerical parameters.

Gas filled panel insulation

DOEpatents

Griffith, B.T.; Arasteh, D.K.; Selkowitz, S.E.

1993-12-14

A structural or flexible highly insulative panel which may be translucent, is formed from multi-layer polymeric material in the form of an envelope surrounding a baffle. The baffle is designed so as to minimize heat transfer across the panel, by using material which forms substantially closed spaces to suppress convection of the low conductivity gas fill. At least a portion of the baffle carries a low emissivity surface for suppression of infrared radiation. 18 figures.

The application of CFD to the modelling of fires in complex geometries

NASA Astrophysics Data System (ADS)

Burns, A. D.; Clarke, D. S.; Guilbert, P.; Jones, I. P.; Simcox, S.; Wilkes, N. S.

The application of Computational Fluid Dynamics (CFD) to industrial safety is a challenging activity. In particular it involves the interaction of several different physical processes, including turbulence, combustion, radiation, buoyancy, compressible flow and shock waves in complex three-dimensional geometries. In addition, there may be multi-phase effects arising, for example, from sprinkler systems for extinguishing fires. The FLOW3D software (1-3) from Computational Fluid Dynamics Services (CFDS) is in widespread use in industrial safety problems, both within AEA Technology, and also by CFDS's commercial customers, for example references (4-13). This paper discusses some other applications of FLOW3D to safety problems. These applications illustrate the coupling of the gas flows with radiation models and combustion models, particularly for complex geometries where simpler radiation models are not applicable.

3D Radiative Transfer Effects in Multi-Angle/Multi-Spectral Radio-Polarimetric Signals from a Mixture of Clouds and Aerosols Viewed by a Non-Imaging Sensor

NASA Technical Reports Server (NTRS)

Davis, Anthony B.; Garay, Michael J.; Xu, Feng; Qu, Zheng; Emde, Claudia

2013-01-01

When observing a spatially complex mix of aerosols and clouds in a single relatively large field-of-view, nature entangles their signals non-linearly through polarized radiation transport processes that unfold in the 3D position and direction spaces. In contrast, any practical forward model in a retrieval algorithm will use only 1D vector radiative transfer (vRT) in a linear mixing technique. We assess the difference between the observed and predicted signals using synthetic data from a high-fidelity 3D vRT model with clouds generated using a Large Eddy Simulation model and an aerosol climatology. We find that this difference is signal--not noise--for the Aerosol Polarimetry Sensor (APS), an instrument developed by NASA. Moreover, the worst case scenario is also the most interesting case, namely, when the aerosol burden is large, hence hase the most impact on the cloud microphysics and dynamics. Based on our findings, we formulate a mitigation strategy for these unresolved cloud adjacency effects assuming that some spatial information is available about the structure of the clouds at higher resolution from "context" cameras, as was planned for NASA's ill-fated Glory mission that was to carry the APS but failed to reach orbit. Application to POLDER (POLarization and Directionality of Earth Reflectances) data from the period when PARASOL (Polarization and Anisotropy of Reflectances for Atmospheric Sciences coupled with Observations from a Lidar) was in the A-train is briefly discussed.

A graphical user interface (GUI) toolkit for the calculation of three-dimensional (3D) multi-phase biological effective dose (BED) distributions including statistical analyses.

PubMed

Kauweloa, Kevin I; Gutierrez, Alonso N; Stathakis, Sotirios; Papanikolaou, Niko; Mavroidis, Panayiotis

2016-07-01

A toolkit has been developed for calculating the 3-dimensional biological effective dose (BED) distributions in multi-phase, external beam radiotherapy treatments such as those applied in liver stereotactic body radiation therapy (SBRT) and in multi-prescription treatments. This toolkit also provides a wide range of statistical results related to dose and BED distributions. MATLAB 2010a, version 7.10 was used to create this GUI toolkit. The input data consist of the dose distribution matrices, organ contour coordinates, and treatment planning parameters from the treatment planning system (TPS). The toolkit has the capability of calculating the multi-phase BED distributions using different formulas (denoted as true and approximate). Following the calculations of the BED distributions, the dose and BED distributions can be viewed in different projections (e.g. coronal, sagittal and transverse). The different elements of this toolkit are presented and the important steps for the execution of its calculations are illustrated. The toolkit is applied on brain, head & neck and prostate cancer patients, who received primary and boost phases in order to demonstrate its capability in calculating BED distributions, as well as measuring the inaccuracy and imprecision of the approximate BED distributions. Finally, the clinical situations in which the use of the present toolkit would have a significant clinical impact are indicated. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Study the effect of chemical reaction and variable viscosity on free convection MHD radiating flow over an inclined plate bounded by porous medium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ali, M., E-mail: ali.mehidi93@gmail.com; Department of Mathematics, Chittagong University of Engineering and Technology, Chittagong-4349; Alim, M. A., E-mail: maalim@math.buet.ac.bd

An analysis is performed to study the free convection heat and mass transfer flow of an electrically conducting incompressible viscous fluid about a semi-infinite inclined porous plate under the action of radiation, chemical reaction in presence of magnetic field with variable viscosity. The dimensionless governing equations are steady, two-dimensional coupled and non-linear ordinary differential equation. Nachtsgeim-Swigert shooting iteration technique along with Runge-Kutta integration scheme is used to solve the non-dimensional governing equations. The effects of magnetic parameter, viscosity parameter and chemical reaction parameter on velocity, temperature and concentration profiles are discussed numerically and shown graphically. Therefore, the results of velocitymore » profile decreases for increasing values of magnetic parameter and viscosity parameter but there is no effect for reaction parameter. The temperature profile decreases in presence of magnetic parameter, viscosity parameter and Prandtl number but increases for radiation parameter. Also, concentration profile decreases for the increasing values of magnetic parameter, viscosity parameter and reaction parameter. All numerical calculations are done with respect to salt water and fixed angle of inclination of the plate.« less

A theory of solar type 3 radio bursts

NASA Technical Reports Server (NTRS)

Goldstein, M. L.; Papadopoulos, K.; Smith, R. A.

1979-01-01

Energetic electrons propagating through the interplanetary medium are shown to excite the one dimensional oscillating two stream instability (OTSI). The OTSI is in turn stabilized by anomalous resistivity which completes the transfer of long wavelength Langmuir waves to short wavelengths, out of resonance with the electrons. The theory explains the small energy losses suffered by the electrons in propagating to 1 AU, the predominance of second harmonic radiation, and the observed correlation between radio and electron fluxes.

Thermal effusivity: a promising imaging biomarker to predict radiation-induced skin injuries.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chu, J. C. H.; Templeton, A.; Yao, R.

An effective screening technology is needed to triage individuals at the time of radiation incidents involving a large population. Three-dimensional thermal tomography is a relatively new development in active thermal imaging technology that produces cross-sectional images based on the subject's ability to transfer heat thermal effusivity at the voxel level. This noninvasive imaging modality has been used successfully in nondestructive examination of complex materials; also it has been shown to predict the severity of radiation-induced skin injuries several days before the manifestation of severe moist desquamations or blister formation symptoms in mice at 40 Gy. If these results are confirmedmore » at lower dose levels in human subjects, a thermal tomography imaging device may be an ideal screening tool in radiation emergencies. This imaging method is non-invasive, relatively simple, easily adaptable for field use, and when properly deployed, it will enhance public emergency preparedness for incidents involving unexpected radiation exposure.« less

Some theorems and properties of multi-dimensional fractional Laplace transforms

NASA Astrophysics Data System (ADS)

Ahmood, Wasan Ajeel; Kiliçman, Adem

2016-06-01

The aim of this work is to study theorems and properties for the one-dimensional fractional Laplace transform, generalize some properties for the one-dimensional fractional Lapalce transform to be valid for the multi-dimensional fractional Lapalce transform and is to give the definition of the multi-dimensional fractional Lapalce transform. This study includes: dedicate the one-dimensional fractional Laplace transform for functions of only one independent variable with some of important theorems and properties and develop of some properties for the one-dimensional fractional Laplace transform to multi-dimensional fractional Laplace transform. Also, we obtain a fractional Laplace inversion theorem after a short survey on fractional analysis based on the modified Riemann-Liouville derivative.

A new silicon detector telescope for measuring the linear energy transfer distribution over the range from 0.2 to 400 keV/micrometer in space.

PubMed

Doke, T; Hayashi, T; Hasebe, N; Kikuchi, J; Kono, S; Murakami, T; Sakaguchi, T; Takahashi, K; Takashima, T

1996-12-01

A new telescope consisting of three two-dimensional position-sensitive silicon detectors which can measure the linear energy transfer (LET) distribution over the range from 0.2 to 400keV/micrometers has been developed as a real-time radiation monitor in manned spacecraft. First, the principle of LET measurement and its design method are described. Second, suitable electronic parameters for the LET measurement are experimentally determined. Finally the telescope performance is investigated by using, relativistic heavy ions. The first in-flight test of this type of telescope on the US Space Shuttle (STS-84) is scheduled for May, 1997.

Development of an Unstructured, Three-Dimensional Material Response Design Tool

NASA Technical Reports Server (NTRS)

Schulz, Joseph; Stern, Eric; Palmer, Grant; Muppidi, Suman; Schroeder, Olivia

2017-01-01

A preliminary verification and validation of a new material response model is presented. This model, Icarus, is intended to serve as a design tool for the thermal protection systems of re-entry vehicles. Currently, the capability of the model is limited to simulating the pyrolysis of a material as a result of the radiative and convective surface heating imposed on the material from the surrounding high enthalpy gas. Since the major focus behind the development of Icarus has been model extensibility, the hope is that additional physics can be quickly added. The extensibility is critical since thermal protection systems are becoming increasing complex, e.g. woven carbon polymers. Additionally, as a three-dimensional, unstructured, finite-volume model, Icarus is capable of modeling complex geometries as well as multi-dimensional physics, which have been shown to be important in some scenarios and are not captured by one-dimensional models. In this paper, the mathematical and numerical formulation is presented followed by a discussion of the software architecture and some preliminary verification and validation studies.

Numerical treatment for Carreau nanofluid flow over a porous nonlinear stretching surface

NASA Astrophysics Data System (ADS)

Eid, Mohamed R.; Mahny, Kasseb L.; Muhammad, Taseer; Sheikholeslami, Mohsen

2018-03-01

The impact of magnetic field and nanoparticles on the two-phase flow of a generalized non-Newtonian Carreau fluid over permeable non-linearly stretching surface has been analyzed in the existence of all suction/injection and thermal radiation. The governing PDEs with congruous boundary condition are transformed into a system of non-linear ODEs with appropriate boundary conditions by using similarity transformation. It solved numerically by using 4th-5th order Runge-Kutta-Fehlberg method based on shooting technique. The impacts of non-dimensional controlling parameters on velocity, temperature, and nanoparticles volume concentration profiles are scrutinized with aid of graphs. The Nusselt and the Sherwood numbers are studied at the different situations of the governing parameters. The numerical computations are in excellent consent with previously reported studies. It is found that the heat transfer rate is reduced with an increment of thermal radiation parameter and on contrary of the rising of magnetic field. The opposite trend happens in the mass transfer rate.

Structure Size Enhanced Histogram

NASA Astrophysics Data System (ADS)

Wesarg, Stefan; Kirschner, Matthias

Direct volume visualization requires the definition of transfer functions (TFs) for the assignment of opacity and color. Multi-dimensional TFs are based on at least two image properties, and are specified by means of 2D histograms. In this work we propose a new type of a 2D histogram which combines gray value with information about the size of the structures. This structure size enhanced (SSE) histogram is an intuitive approach for representing anatomical features. Clinicians — the users we are focusing on — are much more familiar with selecting features by their size than by their gradient magnitude value. As a proof of concept, we employ the SSE histogram for the definition of two-dimensional TFs for the visualization of 3D MRI and CT image data.

A RADIATION TRANSFER SOLVER FOR ATHENA USING SHORT CHARACTERISTICS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davis, Shane W.; Stone, James M.; Jiang Yanfei

2012-03-01

We describe the implementation of a module for the Athena magnetohydrodynamics (MHD) code that solves the time-independent, multi-frequency radiative transfer (RT) equation on multidimensional Cartesian simulation domains, including scattering and non-local thermodynamic equilibrium (LTE) effects. The module is based on well known and well tested algorithms developed for modeling stellar atmospheres, including the method of short characteristics to solve the RT equation, accelerated Lambda iteration to handle scattering and non-LTE effects, and parallelization via domain decomposition. The module serves several purposes: it can be used to generate spectra and images, to compute a variable Eddington tensor (VET) for full radiationmore » MHD simulations, and to calculate the heating and cooling source terms in the MHD equations in flows where radiation pressure is small compared with gas pressure. For the latter case, the module is combined with the standard MHD integrators using operator splitting: we describe this approach in detail, including a new constraint on the time step for stability due to radiation diffusion modes. Implementation of the VET method for radiation pressure dominated flows is described in a companion paper. We present results from a suite of test problems for both the RT solver itself and for dynamical problems that include radiative heating and cooling. These tests demonstrate that the radiative transfer solution is accurate and confirm that the operator split method is stable, convergent, and efficient for problems of interest. We demonstrate there is no need to adopt ad hoc assumptions of questionable accuracy to solve RT problems in concert with MHD: the computational cost for our general-purpose module for simple (e.g., LTE gray) problems can be comparable to or less than a single time step of Athena's MHD integrators, and only few times more expensive than that for more general (non-LTE) problems.« less

A Phase II Study of Submandibular Gland Transfer Prior to Radiation for Prevention of Radiation-induced Xerostomia in Head-and-Neck Cancer (RTOG 0244)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jha, Naresh, E-mail: naresh.jha@albertahealthservices.ca; Harris, Jonathan; Seikaly, Hadi

Purpose: We report the results of a phase II study to determine the reproducibility of a submandibular salivary gland transfer (SGT) surgical technique for prevention of radiation (XRT)-induced xerostomia in a multi-institutional setting and to assess severity of xerostomia. Methods and Materials: Eligible patients had surgery for primary, neck dissection, and SGT, followed by XRT, during which the transferred salivary gland was shielded. Intensity modulated radiation therapy, amifostine, and pilocarpine were not allowed, but postoperative chemotherapy was allowed. Each operation was reviewed by 2 reviewers and radiation by 1 reviewer. If 13 or more (of 43) were 'not per protocol,'more » then the technique would be considered not reproducible as per study design. The secondary endpoint was the rate of acute xerostomia, grade 2 or higher, and a rate of {<=}51% was acceptable. Results: Forty-four of the total 49 patients were analyzable: male (81.8%), oropharynx (63.6%), stage IV (61.4%), median age 56.5 years. SGT was 'per protocol' or within acceptable variation in 34 patients (77.3%) and XRT in 79.5%. Nine patients (20.9%) developed grade 2 acute xerostomia; 2 had grade 0-1 xerostomia (4.7%) but started on amifostine/pilocarpine. Treatment for these 11 patients (25.6%) was considered a failure for the xerostomia endpoint. Thirteen patients died; median follow-up for 31 surviving patients was 2.9 years. Two-year overall and disease-free survival rates were 76.4% and 71.7%, respectively. Conclusions: The technique of submandibular SGT is reproducible in a multicenter setting. Seventy-four percent of patients were prevented from XRT-induced acute xerostomia.« less

A phase II study of submandibular gland transfer prior to radiation for prevention of radiation-induced xerostomia in head-and-neck cancer (RTOG 0244).

PubMed

Jha, Naresh; Harris, Jonathan; Seikaly, Hadi; Jacobs, John R; McEwan, A J B; Robbins, K Thomas; Grecula, John; Sharma, Anand K; Ang, K Kian

2012-10-01

We report the results of a phase II study to determine the reproducibility of a submandibular salivary gland transfer (SGT) surgical technique for prevention of radiation (XRT)-induced xerostomia in a multi-institutional setting and to assess severity of xerostomia. Eligible patients had surgery for primary, neck dissection, and SGT, followed by XRT, during which the transferred salivary gland was shielded. Intensity modulated radiation therapy, amifostine, and pilocarpine were not allowed, but postoperative chemotherapy was allowed. Each operation was reviewed by 2 reviewers and radiation by 1 reviewer. If 13 or more (of 43) were "not per protocol," then the technique would be considered not reproducible as per study design. The secondary endpoint was the rate of acute xerostomia, grade 2 or higher, and a rate of ≤ 51% was acceptable. Forty-four of the total 49 patients were analyzable: male (81.8%), oropharynx (63.6%), stage IV (61.4%), median age 56.5 years. SGT was "per protocol" or within acceptable variation in 34 patients (77.3%) and XRT in 79.5%. Nine patients (20.9%) developed grade 2 acute xerostomia; 2 had grade 0-1 xerostomia (4.7%) but started on amifostine/pilocarpine. Treatment for these 11 patients (25.6%) was considered a failure for the xerostomia endpoint. Thirteen patients died; median follow-up for 31 surviving patients was 2.9 years. Two-year overall and disease-free survival rates were 76.4% and 71.7%, respectively. The technique of submandibular SGT is reproducible in a multicenter setting. Seventy-four percent of patients were prevented from XRT-induced acute xerostomia. Copyright © 2012 Elsevier Inc. All rights reserved.

Finite Volume Numerical Methods for Aeroheating Rate Calculations from Infrared Thermographic Data

NASA Technical Reports Server (NTRS)

Daryabeigi, Kamran; Berry, Scott A.; Horvath, Thomas J.; Nowak, Robert J.

2003-01-01

The use of multi-dimensional finite volume numerical techniques with finite thickness models for calculating aeroheating rates from measured global surface temperatures on hypersonic wind tunnel models was investigated. Both direct and inverse finite volume techniques were investigated and compared with the one-dimensional semi -infinite technique. Global transient surface temperatures were measured using an infrared thermographic technique on a 0.333-scale model of the Hyper-X forebody in the Langley Research Center 20-Inch Mach 6 Air tunnel. In these tests the effectiveness of vortices generated via gas injection for initiating hypersonic transition on the Hyper-X forebody were investigated. An array of streamwise orientated heating striations were generated and visualized downstream of the gas injection sites. In regions without significant spatial temperature gradients, one-dimensional techniques provided accurate aeroheating rates. In regions with sharp temperature gradients due to the striation patterns two-dimensional heat transfer techniques were necessary to obtain accurate heating rates. The use of the one-dimensional technique resulted in differences of 20% in the calculated heating rates because it did not account for lateral heat conduction in the model.

Interface- and discontinuity-aware numerical schemes for plasma 3-T radiation diffusion in two and three dimensions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dai, William W., E-mail: dai@lanl.gov; Scannapieco, Anthony J.

2015-11-01

A set of numerical schemes is developed for two- and three-dimensional time-dependent 3-T radiation diffusion equations in systems involving multi-materials. To resolve sub-cell structure, interface reconstruction is implemented within any cell that has more than one material. Therefore, the system of 3-T radiation diffusion equations is solved on two- and three-dimensional polyhedral meshes. The focus of the development is on the fully coupling between radiation and material, the treatment of nonlinearity in the equations, i.e., in the diffusion terms and source terms, treatment of the discontinuity across cell interfaces in material properties, the formulations for both transient and steady states,more » the property for large time steps, and second order accuracy in both space and time. The discontinuity of material properties between different materials is correctly treated based on the governing physics principle for general polyhedral meshes and full nonlinearity. The treatment is exact for arbitrarily strong discontinuity. The scheme is fully nonlinear for the full nonlinearity in the 3-T diffusion equations. Three temperatures are fully coupled and are updated simultaneously. The scheme is general in two and three dimensions on general polyhedral meshes. The features of the scheme are demonstrated through numerical examples for transient problems and steady states. The effects of some simplifications of numerical schemes are also shown through numerical examples, such as linearization, simple average of diffusion coefficient, and approximate treatment for the coupling between radiation and material.« less

Retrieval of Boundary Layer 3D Cloud Properties Using Scanning Cloud Radar and 3D Radiative Transfer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marchand, Roger

Retrievals of cloud optical and microphysical properties for boundary layer clouds, including those widely used by ASR investigators, frequently assume that clouds are sufficiently horizontally homogeneous that scattering and absorption (at all wavelengths) can be treated using one dimensional (1D) radiative transfer, and that differences in the field-of-view of different sensors are unimportant. Unfortunately, most boundary layer clouds are far from horizontally homogeneous, and numerous theoretical and observational studies show that the assumption of horizontal homogeneity leads to significant errors. The introduction of scanning cloud and precipitation radars at the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) programmore » sites presents opportunities to move beyond the horizontally homogeneous assumption. The primary objective of this project was to develop a 3D retrieval for warm-phase (liquid only) boundary layer cloud microphysical properties, and to assess errors in current 1D (non-scanning) approaches. Specific research activities also involved examination of the diurnal cycle of hydrometeors as viewed by ARM cloud radar, and continued assessment of precipitation impacts on retrievals of cloud liquid water path using passive microwaves.« less

Analysis of loss-of-coolant accident for a fast-spectrum lithium-cooled nuclear reactor for space-power applications

NASA Technical Reports Server (NTRS)

Turney, G. E.; Petrik, E. J.; Kieffer, A. W.

1972-01-01

A two-dimensional, transient, heat-transfer analysis was made to determine the temperature response in the core of a conceptual space-power nuclear reactor following a total loss of reactor coolant. With loss of coolant from the reactor, the controlling mode of heat transfer is thermal radiation. In one of the schemes considered for removing decay heat from the core, it was assumed that the 4 pi shield which surrounds the core acts as a constant-temperature sink (temperature, 700 K) for absorption of thermal radiation from the core. Results based on this scheme of heat removal show that melting of fuel in the core is possible only when the emissivity of the heat-radiating surfaces in the core is less than about 0.40. In another scheme for removing the afterheat, the core centerline fuel pin was replaced by a redundant, constant temperature, coolant channel. Based on an emissivity of 0.20 for all material surfaces in the core, the calculated maximum fuel temperature for this scheme of heat removal was 2840 K, or about 90 K less than the melting temperature of the UN fuel.

Turbulent convection driven by internal radiative heating of melt ponds on sea ice

NASA Astrophysics Data System (ADS)

Wells, Andrew; Langton, Tom; Rees Jones, David; Moon, Woosok

2016-11-01

The melting of Arctic sea ice is strongly influenced by heat transfer through melt ponds which form on the ice surface. Melt ponds are internally heated by the absorption of incoming radiation and cooled by surface heat fluxes, resulting in vigorous buoyancy-driven convection in the pond interior. Motivated by this setting, we conduct two-dimensional direct-numerical simulations of the turbulent convective flow of a Boussinesq fluid between two horizontal boundaries, with internal heating predicted from a two-stream radiation model. A linearised thermal boundary condition describes heat exchange with the overlying atmosphere, whilst the lower boundary is isothermal. Vertically asymmetric convective flow modifies the upper surface temperature, and hence controls the partitioning of the incoming heat flux between emission at the upper and lower boundaries. We determine how the downward heat flux into the ice varies with a Rayleigh number based on the internal heating rate, the flux ratio of background surface cooling compared to internal heating, and a Biot number characterising the sensitivity of surface fluxes to surface temperature. Thus we elucidate the physical controls on heat transfer through Arctic melt ponds which determine the fate of sea ice in the summer.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kakoniti, Androula; Georgiou, Gregoria; Neophytou, Marina

Two-dimensional steady-state simulations have been performed using the standard k-e turbulence model coupled with the heat transfer models available in the CFD software FLUENT 6.1, in order to examine the impact of radiation on the Urban Heat Island phenomenon. Specifically, the impact of radiation in three typical urban areas of Cyprus during the summer period is examined. The first geometry considered represents a typical suburban area and is termed as the reference geometry. The second geometry represents an area at the centre of a town with higher buildings and relatively narrower roads. The third geometry, on the other hand, describesmore » a suburban area with wider roads and larger houses than the reference model. Computed values for air temperature in the urban street canyon have indicated that the increase in temperature associated with radiative heat transfer can be reduced by optimising the canyon geometry and, ultimately, help to mitigate the human thermal discomfort. The present study has also revealed that the selection of construction materials can be optimised to offer further reductions in the air temperature of the urban environment. It can be concluded that the combined effect of these remedies can lead to reductions in the energy consumption for building air-conditioning over the summer period.« less

Status of the Combustion Devices Injector Technology Program at the NASA MSFC

NASA Technical Reports Server (NTRS)

Jones, Gregg; Protz, Christopher; Trinh, Huu; Tucker, Kevin; Nesman, Tomas; Hulka, James

2005-01-01

To support the NASA Space Exploration Mission, an in-house program called Combustion Devices Injector Technology (CDIT) is being conducted at the NASA Marshall Space Flight Center (MSFC) for the fiscal year 2005. CDIT is focused on developing combustor technology and analysis tools to improve reliability and durability of upper-stage and in-space liquid propellant rocket engines. The three areas of focus include injector/chamber thermal compatibility, ignition, and combustion stability. In the compatibility and ignition areas, small-scale single- and multi-element hardware experiments will be conducted to demonstrate advanced technological concepts as well as to provide experimental data for validation of computational analysis tools. In addition, advanced analysis tools will be developed to eventually include 3-dimensional and multi- element effects and improve capability and validity to analyze heat transfer and ignition in large, multi-element injectors.

Progress in multi-dimensional upwind differencing

NASA Technical Reports Server (NTRS)

Vanleer, Bram

1992-01-01

Multi-dimensional upwind-differencing schemes for the Euler equations are reviewed. On the basis of the first-order upwind scheme for a one-dimensional convection equation, the two approaches to upwind differencing are discussed: the fluctuation approach and the finite-volume approach. The usual extension of the finite-volume method to the multi-dimensional Euler equations is not entirely satisfactory, because the direction of wave propagation is always assumed to be normal to the cell faces. This leads to smearing of shock and shear waves when these are not grid-aligned. Multi-directional methods, in which upwind-biased fluxes are computed in a frame aligned with a dominant wave, overcome this problem, but at the expense of robustness. The same is true for the schemes incorporating a multi-dimensional wave model not based on multi-dimensional data but on an 'educated guess' of what they could be. The fluctuation approach offers the best possibilities for the development of genuinely multi-dimensional upwind schemes. Three building blocks are needed for such schemes: a wave model, a way to achieve conservation, and a compact convection scheme. Recent advances in each of these components are discussed; putting them all together is the present focus of a worldwide research effort. Some numerical results are presented, illustrating the potential of the new multi-dimensional schemes.

An implicit-iterative solution of the heat conduction equation with a radiation boundary condition

NASA Technical Reports Server (NTRS)

Williams, S. D.; Curry, D. M.

1977-01-01

For the problem of predicting one-dimensional heat transfer between conducting and radiating mediums by an implicit finite difference method, four different formulations were used to approximate the surface radiation boundary condition while retaining an implicit formulation for the interior temperature nodes. These formulations are an explicit boundary condition, a linearized boundary condition, an iterative boundary condition, and a semi-iterative boundary method. The results of these methods in predicting surface temperature on the space shuttle orbiter thermal protection system model under a variety of heating rates were compared. The iterative technique caused the surface temperature to be bounded at each step. While the linearized and explicit methods were generally more efficient, the iterative and semi-iterative techniques provided a realistic surface temperature response without requiring step size control techniques.

Karyotyping of Chromosomes in Human Bronchial Epithelial Cells Transformed by High Energy Fe Ions

NASA Technical Reports Server (NTRS)

Yeshitla, Samrawit; Zhang, Ye; Park, Seongmi; Story, Michael D.; Wilson, Bobby; Wu, Honglu

2015-01-01

Lung cancer induced from exposures to space radiation is one of the most significant health risks for long-term space travels. Evidences show that low- and high- Linear energy transfer (LET)-induced transformation of normal human bronchial epithelial cells (HBEC) that are immortalized through the expression of Cdk4 and hTERT. The cells were exposed to gamma rays and high-energy Fe ions for the selection of transformed clones. Transformed HBEC are identified and analyzed chromosome aberrations (i.e. genomic instability) using the multi-color fluorescent in situ hybridization (mFISH), as well as the multi-banding in situ hybridization (mBAND) techniques. Our results show chromosomal translocations between different chromosomes and several of the breaks occurred in the q-arm of chromosome 3. We also identified copy number variations between the transformed and the parental HBEC regardless of the exposure conditions. We observed chromosomal aberrations in the lowand high-LET radiation-induced transformed clones and they are imperfectly different from clones obtain in spontaneous soft agar growth.

A 2.5-dimensional method for the prediction of structure-borne low-frequency noise from concrete rail transit bridges.

PubMed

Li, Qi; Song, Xiaodong; Wu, Dingjun

2014-05-01

Predicting structure-borne noise from bridges subjected to moving trains using the three-dimensional (3D) boundary element method (BEM) is a time consuming process. This paper presents a two-and-a-half dimensional (2.5D) BEM-based procedure for simulating bridge-borne low-frequency noise with higher efficiency, yet no loss of accuracy. The two-dimensional (2D) BEM of a bridge with a constant cross section along the track direction is adopted to calculate the spatial modal acoustic transfer vectors (MATVs) of the bridge using the space-wave number transforms of its 3D modal shapes. The MATVs calculated using the 2.5D method are then validated by those computed using the 3D BEM. The bridge-borne noise is finally obtained through the MATVs and modal coordinate responses of the bridge, considering time-varying vehicle-track-bridge dynamic interaction. The presented procedure is applied to predict the sound pressure radiating from a U-shaped concrete bridge, and the computed results are compared with those obtained from field tests on Shanghai rail transit line 8. The numerical results match well with the measured results in both time and frequency domains at near-field points. Nevertheless, the computed results are smaller than the measured ones for far-field points, mainly due to the sound radiation from adjacent spans neglected in the current model.

PURDU-WINCOF: A computer code for establishing the performance of a fan-compressor unit with water ingestion

NASA Technical Reports Server (NTRS)

Leonardo, M.; Tsuchiya, T.; Murthy, S. N. B.

1982-01-01

A model for predicting the performance of a multi-spool axial-flow compressor with a fan during operation with water ingestion was developed incorporating several two-phase fluid flow effects as follows: (1) ingestion of water, (2) droplet interaction with blades and resulting changes in blade characteristics, (3) redistribution of water and water vapor due to centrifugal action, (4) heat and mass transfer processes, and (5) droplet size adjustment due to mass transfer and mechanical stability considerations. A computer program, called the PURDU-WINCOF code, was generated based on the model utilizing a one-dimensional formulation. An illustrative case serves to show the manner in which the code can be utilized and the nature of the results obtained.

Low heat transfer, high strength window materials

DOEpatents

Berlad, Abraham L.; Salzano, Francis J.; Batey, John E.

1978-01-01

A multi-pane window with improved insulating qualities; comprising a plurality of transparent or translucent panes held in an essentially parallel, spaced-apart relationship by a frame. Between at least one pair of panes is a convection defeating means comprising an array of parallel slats or cells so designed as to prevent convection currents from developing in the space between the two panes. The convection defeating structures may have reflective surfaces so as to improve the collection and transmittance of the incident radiant energy. These same means may be used to control (increase or decrease) the transmittance of solar energy as well as to decouple the radiative transfer between the interior surfaces of the transparent panes.

Posterior uncertainty of GEOS-5 L-band radiative transfer model parameters and brightness temperatures after calibration with SMOS observations

NASA Astrophysics Data System (ADS)

De Lannoy, G. J.; Reichle, R. H.; Vrugt, J. A.

2012-12-01

Simulated L-band (1.4 GHz) brightness temperatures are very sensitive to the values of the parameters in the radiative transfer model (RTM). We assess the optimum RTM parameter values and their (posterior) uncertainty in the Goddard Earth Observing System (GEOS-5) land surface model using observations of multi-angular brightness temperature over North America from the Soil Moisture Ocean Salinity (SMOS) mission. Two different parameter estimation methods are being compared: (i) a particle swarm optimization (PSO) approach, and (ii) an MCMC simulation procedure using the differential evolution adaptive Metropolis (DREAM) algorithm. Our results demonstrate that both methods provide similar "optimal" parameter values. Yet, DREAM exhibits better convergence properties, resulting in a reduced spread of the posterior ensemble. The posterior parameter distributions derived with both methods are used for predictive uncertainty estimation of brightness temperature. This presentation will highlight our model-data synthesis framework and summarize our initial findings.

Finite element study of three dimensional radiative nano-plasma flow subject to Hall and ion slip currents

NASA Astrophysics Data System (ADS)

Nawaz, M.; Zubair, T.

In this article, we developed a computer code of Galerikan Finite Element method (GFEM) for three dimensional flow equations of nano-plasma fluid (blood) in the presence of uniform applied magnetic field when Hall and ion slip current are significant. Lorentz force is calculated through generalized Ohm's law with Maxwell equations. A series of numerical simulations are carried out to search ηmax and algebraic equations are solved by Gauss-Seidel method with simulation tolerance 10-8 . Simulated results for special case have an excellent agreement with the already published results. Velocity components and temperature of the nano-plasma (blood) are influenced significantly by the inclusion of nano-particles of Copper (Cu) and Silver (Ag). Heat enhancement is observed when copper and silver nonmagnetic nanoparticles are used instead of simple base fluid (conventional fluid). Radiative nature of nano-plasma in the presence of magnetic field causes a decrease in the temperature due to the transfer of heat by the electromagnetic waves. In contrast to this, due to heat dissipated by Joule heating and viscous dissipation phenomena, temperature of nano-plasmaincreases as thermal radiation parameter is increased. Thermal boundary layer thickness can be controlled by using radiative fluid instead of non-radiative fluid. Momentum boundary layer thickness can be reduced by increasing the intensity of the applied magnetic field. Temperature of plasma in the presence magnetic field is higher than the plasma in the absence of magnetic field.

High-order multipole radiation from quantum Hall states in Dirac materials

NASA Astrophysics Data System (ADS)

Gullans, Michael J.; Taylor, Jacob M.; Imamoǧlu, Ataç; Ghaemi, Pouyan; Hafezi, Mohammad

2017-06-01

We investigate the optical response of strongly disordered quantum Hall states in two-dimensional Dirac materials and find qualitatively different effects in the radiation properties of the bulk versus the edge. We show that the far-field radiation from the edge is characterized by large multipole moments (>50 ) due to the efficient transfer of angular momentum from the electrons into the scattered light. The maximum multipole transition moment is a direct measure of the coherence length of the edge states. Accessing these multipole transitions would provide new tools for optical spectroscopy and control of quantum Hall edge states. On the other hand, the far-field radiation from the bulk appears as random dipole emission with spectral properties that vary with the local disorder potential. We determine the conditions under which this bulk radiation can be used to image the disorder landscape. Such optical measurements can probe submicron-length scales over large areas and provide complementary information to scanning probe techniques. Spatially resolving this bulk radiation would serve as a novel probe of the percolation transition near half filling.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lobel, R.

TRUMP is a general finite difference computer program for the solution of transient and steady state heat transfer problems. It is a very general program capable of solving heat transfer problems in one, two or three dimensions for plane, cylindrical or spherical geometry. Because of the variety of possible geometries, the effort required to describe the geometry can be large. GIFT was written to minimize this effort for one-dimensional heat flow problems. After describing the inner and outer boundaries of a region made of a single material along with the modes of heat transfer which thermally connect different regions, GIFTmore » will calculate all the geometric data (BLOCK 04) and thermal network data (BLOCK 05) required by TRUMP for one-dimensional problems. The heat transfer between layers (or shells) of a material may be by conduction or radiation; also, an interface resistance between layers can be specified. Convection between layers can be accounted for by use of an effective thermal conductivity in which the convection effect is included or by a thermal conductance coefficient. GIFT was written for the Sigma 7 computer, a small digital computer with a versatile graphic display system. This system makes it possible to input the desired data in a question and answer mode and to see both the input and the output displayed on a screen in front of the user at all times. (auth)« less

Polarized scattered light from self-luminous exoplanets. Three-dimensional scattering radiative transfer with ARTES

NASA Astrophysics Data System (ADS)

Stolker, T.; Min, M.; Stam, D. M.; Mollière, P.; Dominik, C.; Waters, L. B. F. M.

2017-11-01

Context. Direct imaging has paved the way for atmospheric characterization of young and self-luminous gas giants. Scattering in a horizontally-inhomogeneous atmosphere causes the disk-integrated polarization of the thermal radiation to be linearly polarized, possibly detectable with the newest generation of high-contrast imaging instruments. Aims: We aim to investigate the effect of latitudinal and longitudinal cloud variations, circumplanetary disks, atmospheric oblateness, and cloud particle properties on the integrated degree and direction of polarization in the near-infrared. We want to understand how 3D atmospheric asymmetries affect the polarization signal in order to assess the potential of infrared polarimetry for direct imaging observations of planetary-mass companions. Methods: We have developed a three-dimensional Monte Carlo radiative transfer code (ARTES) for scattered light simulations in (exo)planetary atmospheres. The code is applicable to calculations of reflected light and thermal radiation in a spherical grid with a parameterized distribution of gas, clouds, hazes, and circumplanetary material. A gray atmosphere approximation is used for the thermal structure. Results: The disk-integrated degree of polarization of a horizontally-inhomogeneous atmosphere is maximal when the planet is flattened, the optical thickness of the equatorial clouds is large compared to the polar clouds, and the clouds are located at high altitude. For a flattened planet, the integrated polarization can both increase or decrease with respect to a spherical planet which depends on the horizontal distribution and optical thickness of the clouds. The direction of polarization can be either parallel or perpendicular to the projected direction of the rotation axis when clouds are zonally distributed. Rayleigh scattering by submicron-sized cloud particles will maximize the polarimetric signal whereas the integrated degree of polarization is significantly reduced with micron-sized cloud particles as a result of forward scattering. The presence of a cold or hot circumplanetary disk may also produce a detectable degree of polarization (≲1%) even with a uniform cloud layer in the atmosphere.

Radiation-Tolerant, SpaceWire-Compatible Switching Fabric

NASA Technical Reports Server (NTRS)

Katzman, Vladimir

2011-01-01

Current and future near-Earth and deep space exploration programs and space defense programs require the development of robust intra-spacecraft serial data transfer electronics that must be reconfigurable, fault-tolerant, and have the ability to operate effectively for long periods of time in harsh environmental conditions. Existing data transfer systems based on state-of-the-art serial data transfer protocols or passive backplanes are slow, power-hungry, and poorly reconfigurable. They provide limited expandability and poor tolerance to radiation effects and total ionizing dose (TID) in particular, which presents harmful threats to modern submicron electronics. This novel approach is based on a standard library of differential cells tolerant to TID, and patented, multi-level serial interface architecture that ensures the reliable operation of serial interconnects without application of a data-strobe or other encoding techniques. This proprietary, high-speed differential interface presents a lowpower solution fully compatible with the SpaceWire (SW) protocol. It replaces a dual data-strobe link with two identical independent data channels, thus improving the system s tolerance to harsh environments through additional double redundancy. Each channel incorporates an automatic line integrity control circuitry that delivers error signals in case of broken or shorted lines.

A Numerical Study of Cirrus Clouds. Part I: Model Description.

NASA Astrophysics Data System (ADS)

Liu, Hui-Chun; Wang, Pao K.; Schlesinger, Robert E.

2003-04-01

This article, the first of a two-part series, presents a detailed description of a two-dimensional numerical cloud model directed toward elucidating the physical processes governing the evolution of cirrus clouds. The two primary scientific purposes of this work are (a) to determine the evolution and maintenance mechanisms of cirrus clouds and try to explain why some cirrus can persist for a long time; and (b) to investigate the influence of certain physical factors such as radiation, ice crystal habit, latent heat, ventilation effects, and aggregation mechanisms on the evolution of cirrus. The second part will discuss sets of model experiments that were run to address objectives (a) and (b), respectively.As set forth in this paper, the aforementioned two-dimensional numerical model, which comprises the research tool for this study, is organized into three modules that embody dynamics, microphysics, and radiation. The dynamic module develops a set of equations to describe shallow moist convection, also parameterizing turbulence by using a 1.5-order closure scheme. The microphysical module uses a double-moment scheme to simulate the evolution of the size distribution of ice particles. Heterogeneous and homogeneous nucleation of haze particles are included, along with other ice crystal processes such as diffusional growth, sedimentation, and aggregation. The radiation module uses a two-stream radiative transfer scheme to determine the radiative fluxes and heating rates, while the cloud optical properties are determined by the modified anomalous diffraction theory (MADT) for ice particles. One of the main advantages of this cirrus model is its explicit formulation of the microphysical and radiative properties as functions of ice crystal habit.

The multi-mode modulator: A versatile fluidic device for two-dimensional gas chromatography.

PubMed

Seeley, John V; Schimmel, Nicolaas E; Seeley, Stacy K

2018-02-09

A fluidic device called the multi-mode modulator (MMM) has been developed for use as a comprehensive two-dimensional gas chromatography (GC x GC) modulator. The MMM can be employed in a wide range of capacities including as a traditional heart-cutting device, a low duty cycle GC x GC modulator, and a full transfer GC x GC modulator. The MMM is capable of producing narrow component pulses (widths <50ms) while operating at flows compatible with high resolution chromatography. The sample path of modulated components is confined to the interior of a joining capillary. The joining capillary dimensions and the position of the columns within the joining capillary can be optimized for the selected modulation mode. Furthermore, the joining capillary can be replaced easily and inexpensively if it becomes fouled due to sample matrix components or column bleed. The principles of operation of the MMM are described and its efficacy is demonstrated as a heart-cutting device and as a GC x GC modulator. Copyright © 2017 Elsevier B.V. All rights reserved.

Vertical Plane Oscillation Experiments on a Series of Two-Dimensional SWATH Demi-Hull Sections

DTIC Science & Technology

1988-08-01

32 21. Example of repeatability of hydrodynamic coefficients for the Z1 gage, and wave TF1 , for model A...waves heights from probes 1 and 2 were divided by the heave oscillation amplitude to define radiated wave transfer functions , TF1 and TF2...delta2) and TF1 and TF2 are presented versus kB/2 on a single page for each combination of draft and amplitude tested. The plots are followed by the

Advanced Radiation Theory Support Annual Report 2003, Final Report

DTIC Science & Technology

2004-04-19

diameter wires would lose a higher mass fraction. Table 2. Energy Transfers for Ti Loads Dia. & Case H 2 H13 Mass -a-m Z,DE kJ kJ Pg 1000 - Z 428.2...issues covered are (1) issues and directions for future research, (2) zero- and one-dimensional modeling of DQ experiments, (3) enhanced energy ...coupling and x-ray emission in z-pinch implosions, (4) confinement and compression of magnetic flux by plasma shells, and (6) flashover and energy coupling

Ultra-high resolution computed tomography imaging

DOEpatents

Paulus, Michael J.; Sari-Sarraf, Hamed; Tobin, Jr., Kenneth William; Gleason, Shaun S.; Thomas, Jr., Clarence E.

2002-01-01

A method for ultra-high resolution computed tomography imaging, comprising the steps of: focusing a high energy particle beam, for example x-rays or gamma-rays, onto a target object; acquiring a 2-dimensional projection data set representative of the target object; generating a corrected projection data set by applying a deconvolution algorithm, having an experimentally determined a transfer function, to the 2-dimensional data set; storing the corrected projection data set; incrementally rotating the target object through an angle of approximately 180.degree., and after each the incremental rotation, repeating the radiating, acquiring, generating and storing steps; and, after the rotating step, applying a cone-beam algorithm, for example a modified tomographic reconstruction algorithm, to the corrected projection data sets to generate a 3-dimensional image. The size of the spot focus of the beam is reduced to not greater than approximately 1 micron, and even to not greater than approximately 0.5 microns.

A new Schwarzschild optical system for two-dimensional EUV imaging of MRX plasmas

NASA Astrophysics Data System (ADS)

Bolgert, P.; Bitter, M.; Efthimion, P.; Hill, K. W.; Ji, H.; Myers, C. E.; Yamada, M.; Yoo, J.; Zweben, S.

2013-10-01

This poster describes the design and construction of a new Schwarzschild optical system for two-dimensional EUV imaging of plasmas. This optical system consists of two concentric spherical mirrors with radii R1 and R2, and is designed to operate with certain angles of incidence θ1 and θ2. The special feature of this system resides in the fact that all the rays passing through the system are tangential to a third concentric circle; it assures that the condition for Bragg reflection is simultaneously fulfilled at each point on the two reflecting surfaces if the spherical mirrors are replaced by spherical multi-layer structures. A prototype of this imaging system will be implemented in the Magnetic Reconnection Experiment (MRX) at PPPL to obtain two-dimensional EUV images of the plasma in the energy range from 18 to 62 eV; the relative intensity of the emitted radiation in this energy range was determined from survey measurements with a photodiode. It is thought that the radiation at these energies is due to Bremsstrahlung and line emission caused by suprathermal electrons. This research is supported by DoE Contract Number DE-AC02-09CH11466 and by the Center for Magnetic Self-Organization (CMSO).

Optical coupling between atomically thin black phosphorus and a two dimensional photonic crystal nanocavity

NASA Astrophysics Data System (ADS)

Ota, Yasutomo; Moriya, Rai; Yabuki, Naoto; Arai, Miho; Kakuda, Masahiro; Iwamoto, Satoshi; Machida, Tomoki; Arakawa, Yasuhiko

2017-05-01

Atomically thin black phosphorus (BP) is an emerging two dimensional (2D) material exhibiting bright photoluminescence in the near infrared region. Coupling its radiation to photonic nanostructures will be an important step toward the realization of 2D material based nanophotonic devices that operate efficiently in the near infrared region, which includes the technologically important optical telecommunication wavelength bands. In this letter, we demonstrate the optical coupling between atomically thin BP and a 2D photonic crystal nanocavity. We employed a home-build dry transfer apparatus for placing a thin BP flake on the surface of the nanocavity. Their optical coupling was analyzed through measuring cavity mode emission under optical carrier injection at room temperature.

Network-Oriented Radiation Monitoring System (NORMS)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rahmat Aryaeinejad; David F. Spencer

2007-10-01

We have developed a multi-functional pocket radiation monitoring system capable of detecting and storing gamma ray and neutron data and then sending the data through a wireless connection to a remote central facility upon request. The device has programmable alarm trigger levels that can be modified for specific applications. The device could be used as a stand-alone device or in conjunction with an array to cover a small or large area. The data is stored with a date/time stamp. The device may be remotely configured. Data can be transferred and viewed on a PDA via direct connection or wirelessly. Functional/benchmore » tests have been completed successfully. The device detects low-level neutron and gamma sources within a shielded container in a radiation field of 10 uR/hr above the ambient background level.« less

A portable extruder for in situ wide angle x-ray scattering study on multi-dimensional flow field induced crystallization of polymer

NASA Astrophysics Data System (ADS)

Chang, Jiarui; Wang, Zhen; Tang, Xiaoliang; Tian, Fucheng; Ye, Ke; Li, Liangbin

2018-02-01

We have designed and constructed a portable extruder with a rotatable mandrel, which can be employed to study the multi-dimensional flow field (MDFF) induced crystallization of polymer combined with in situ wide angle x-ray scattering (WAXS). With the piston driving the melt sample to flow along the channel, a direct axial shear field is achieved. At the same time, the central mandrel keeps rotating under a stable speed, providing the sample with an additional circumferential shear field. By presetting different proportions of the two shear fields, namely, axial and circumferential, various flow states of the sample can be obtained, which makes it capable of investigating the effects of MDFF on polymer crystallization. We have performed an in situ WAXS experiment of MDFF induced crystallization of isotactic polypropylene based on the portable extruder at the beam line BL16B in Shanghai Synchrotron Radiation Facility. The rheological and structural information is collected simultaneously, which manifests the viability of the portable extruder on regulating MDFF and can provide guidance for polymer processing.

Multi-anode wire two dimensional proportional counter for detecting Iron-55 X-Ray Radiation

NASA Astrophysics Data System (ADS)

Weston, Michael William James

Radiation detectors in many applications use small sensor areas or large tubes which only collect one-dimensional information. There are some applications that require analyzing a large area and locating specific elements such as contamination on the heat tiles of a space shuttle or features on historical artifacts. The process can be time consuming and scanning a large area in a single pass is beneficial. The use of a two dimensional multi-wire proportional counter provides a large detection window presenting positional information in a single pass. This thesis described the design and implementation of an experimental detector to evaluate a specific design intended for use as a handheld instrument. The main effort of this research was to custom build a detector for testing purposes. The aluminum chamber and all circuit boards were custom designed and built specifically for this application. Various software and programmable logic algorithms were designed to analyze the raw data in real time and attempted to determine what data was useful and what could be discarded. The research presented here provides results useful for designing an improved second generation detector in the future. With the anode wire spacing chosen and the minimal collimation of the radiation source, detected events occurred all over the detection grid at any time. The raw event data did not make determining the source position easy and further data correlation was required. An abundance of samples had multiple wire hits which were not useful because it falsely reported the source to be all over the place and at different energy levels. By narrowing down the results to only use the largest signal pairs on different axes in each event, a much more accurate analysis of where the source existed above the grid was determined. The basic principle and construction method was shown to work, however the gas selection, geometry and anode wire constructs proved to be poor. To provide a system optimized for a specific application would require detailed Monte Carlo simulations. These simulation results together with the details and techniques implemented in this thesis would provide a final instrument of much higher accuracy.

3D-radiative transfer in terrestrial atmosphere: An efficient parallel numerical procedure

NASA Astrophysics Data System (ADS)

Bass, L. P.; Germogenova, T. A.; Nikolaeva, O. V.; Kokhanovsky, A. A.; Kuznetsov, V. S.

2003-04-01

Light propagation and scattering in terrestrial atmosphere is usually studied in the framework of the 1D radiative transfer theory [1]. However, in reality particles (e.g., ice crystals, solid and liquid aerosols, cloud droplets) are randomly distributed in 3D space. In particular, their concentrations vary both in vertical and horizontal directions. Therefore, 3D effects influence modern cloud and aerosol retrieval procedures, which are currently based on the 1D radiative transfer theory. It should be pointed out that the standard radiative transfer equation allows to study these more complex situations as well [2]. In recent year the parallel version of the 2D and 3D RADUGA code has been developed. This version is successfully used in gammas and neutrons transport problems [3]. Applications of this code to radiative transfer in atmosphere problems are contained in [4]. Possibilities of code RADUGA are presented in [5]. The RADUGA code system is an universal solver of radiative transfer problems for complicated models, including 2D and 3D aerosol and cloud fields with arbitrary scattering anisotropy, light absorption, inhomogeneous underlying surface and topography. Both delta type and distributed light sources can be accounted for in the framework of the algorithm developed. The accurate numerical procedure is based on the new discrete ordinate SWDD scheme [6]. The algorithm is specifically designed for parallel supercomputers. The version RADUGA 5.1(P) can run on MBC1000M [7] (768 processors with 10 Gb of hard disc memory for each processor). The peak productivity is equal 1 Tfl. Corresponding scalar version RADUGA 5.1 is working on PC. As a first example of application of the algorithm developed, we have studied the shadowing effects of clouds on neighboring cloudless atmosphere, depending on the cloud optical thickness, surface albedo, and illumination conditions. This is of importance for modern satellite aerosol retrieval algorithms development. [1] Sobolev, V. V., 1972: Light scattering in planetary atmosphere, M.:Nauka. [2] Evans, K. F., 1998: The spherical harmonic discrete ordinate method for three dimensional atmospheric radiative transfer, J. Atmos. Sci., 55, 429 446. [3] L.P. Bass, T.A. Germogenova, V.S. Kuznetsov, O.V. Nikolaeva. RADUGA 5.1 and RADUGA 5.1(P) codes for stationary transport equation solution in 2D and 3D geometries on one and multiprocessors computers. Report on seminar “Algorithms and Codes for neutron physical of nuclear reactor calculations” (Neutronica 2001), Obninsk, Russia, 30 October 2 November 2001. [4] T.A. Germogenova, L.P. Bass, V.S. Kuznetsov, O.V. Nikolaeva. Mathematical modeling on parallel computers solar and laser radiation transport in 3D atmosphere. Report on International Symposium CIS countries “Atmosphere radiation”, 18 21 June 2002, St. Peterburg, Russia, p. 15 16. [5] L.P. Bass, T.A. Germogenova, O.V. Nikolaeva, V.S. Kuznetsov. Radiative Transfer Universal 2D 3D Code RADUGA 5.1(P) for Multiprocessor Computer. Abstract. Poster report on this Meeting. [6] L.P. Bass, O.V. Nikolaeva. Correct calculation of Angular Flux Distribution in Strongly Heterogeneous Media and Voids. Proc. of Joint International Conference on Mathematical Methods and Supercomputing for Nuclear Applications, Saratoga Springs, New York, October 5 9, 1997, p. 995 1004. [7] http://www/jscc.ru

Coarse-grained component concurrency in Earth system modeling: parallelizing atmospheric radiative transfer in the GFDL AM3 model using the Flexible Modeling System coupling framework

NASA Astrophysics Data System (ADS)

Balaji, V.; Benson, Rusty; Wyman, Bruce; Held, Isaac

2016-10-01

Climate models represent a large variety of processes on a variety of timescales and space scales, a canonical example of multi-physics multi-scale modeling. Current hardware trends, such as Graphical Processing Units (GPUs) and Many Integrated Core (MIC) chips, are based on, at best, marginal increases in clock speed, coupled with vast increases in concurrency, particularly at the fine grain. Multi-physics codes face particular challenges in achieving fine-grained concurrency, as different physics and dynamics components have different computational profiles, and universal solutions are hard to come by. We propose here one approach for multi-physics codes. These codes are typically structured as components interacting via software frameworks. The component structure of a typical Earth system model consists of a hierarchical and recursive tree of components, each representing a different climate process or dynamical system. This recursive structure generally encompasses a modest level of concurrency at the highest level (e.g., atmosphere and ocean on different processor sets) with serial organization underneath. We propose to extend concurrency much further by running more and more lower- and higher-level components in parallel with each other. Each component can further be parallelized on the fine grain, potentially offering a major increase in the scalability of Earth system models. We present here first results from this approach, called coarse-grained component concurrency, or CCC. Within the Geophysical Fluid Dynamics Laboratory (GFDL) Flexible Modeling System (FMS), the atmospheric radiative transfer component has been configured to run in parallel with a composite component consisting of every other atmospheric component, including the atmospheric dynamics and all other atmospheric physics components. We will explore the algorithmic challenges involved in such an approach, and present results from such simulations. Plans to achieve even greater levels of coarse-grained concurrency by extending this approach within other components, such as the ocean, will be discussed.

Optimization of a Radiative Transfer Forward Operator for Simulating SMOS Brightness Temperatures over the Upper Mississippi Basin, USA

NASA Technical Reports Server (NTRS)

Lievens, H.; Verhoest, N. E. C.; Martens, B.; VanDenBerg, M. J.; Bitar, A. Al; Tomer, S. Kumar; Merlin, O.; Cabot, F.; Kerr, Y.; DeLannoy, G. J. M.;

Derivation of global vegetation biophysical parameters from EUMETSAT Polar System

NASA Astrophysics Data System (ADS)

García-Haro, Francisco Javier; Campos-Taberner, Manuel; Muñoz-Marí, Jordi; Laparra, Valero; Camacho, Fernando; Sánchez-Zapero, Jorge; Camps-Valls, Gustau

2018-05-01

This paper presents the algorithm developed in LSA-SAF (Satellite Application Facility for Land Surface Analysis) for the derivation of global vegetation parameters from the AVHRR (Advanced Very High Resolution Radiometer) sensor on board MetOp (Meteorological-Operational) satellites forming the EUMETSAT (European Organization for the Exploitation of Meteorological Satellites) Polar System (EPS). The suite of LSA-SAF EPS vegetation products includes the leaf area index (LAI), the fractional vegetation cover (FVC), and the fraction of absorbed photosynthetically active radiation (FAPAR). LAI, FAPAR, and FVC characterize the structure and the functioning of vegetation and are key parameters for a wide range of land-biosphere applications. The algorithm is based on a hybrid approach that blends the generalization capabilities offered by physical radiative transfer models with the accuracy and computational efficiency of machine learning methods. One major feature is the implementation of multi-output retrieval methods able to jointly and more consistently estimate all the biophysical parameters at the same time. We propose a multi-output Gaussian process regression (GPRmulti), which outperforms other considered methods over PROSAIL (coupling of PROSPECT and SAIL (Scattering by Arbitrary Inclined Leaves) radiative transfer models) EPS simulations. The global EPS products include uncertainty estimates taking into account the uncertainty captured by the retrieval method and input errors propagation. A sensitivity analysis is performed to assess several sources of uncertainties in retrievals and maximize the positive impact of modeling the noise in training simulations. The paper discusses initial validation studies and provides details about the characteristics and overall quality of the products, which can be of interest to assist the successful use of the data by a broad user's community. The consistent generation and distribution of the EPS vegetation products will constitute a valuable tool for monitoring of earth surface dynamic processes.

Automated segmentation of thyroid gland on CT images with multi-atlas label fusion and random classification forest

NASA Astrophysics Data System (ADS)

Liu, Jiamin; Chang, Kevin; Kim, Lauren; Turkbey, Evrim; Lu, Le; Yao, Jianhua; Summers, Ronald

2015-03-01

The thyroid gland plays an important role in clinical practice, especially for radiation therapy treatment planning. For patients with head and neck cancer, radiation therapy requires a precise delineation of the thyroid gland to be spared on the pre-treatment planning CT images to avoid thyroid dysfunction. In the current clinical workflow, the thyroid gland is normally manually delineated by radiologists or radiation oncologists, which is time consuming and error prone. Therefore, a system for automated segmentation of the thyroid is desirable. However, automated segmentation of the thyroid is challenging because the thyroid is inhomogeneous and surrounded by structures that have similar intensities. In this work, the thyroid gland segmentation is initially estimated by multi-atlas label fusion algorithm. The segmentation is refined by supervised statistical learning based voxel labeling with a random forest algorithm. Multiatlas label fusion (MALF) transfers expert-labeled thyroids from atlases to a target image using deformable registration. Errors produced by label transfer are reduced by label fusion that combines the results produced by all atlases into a consensus solution. Then, random forest (RF) employs an ensemble of decision trees that are trained on labeled thyroids to recognize features. The trained forest classifier is then applied to the thyroid estimated from the MALF by voxel scanning to assign the class-conditional probability. Voxels from the expert-labeled thyroids in CT volumes are treated as positive classes; background non-thyroid voxels as negatives. We applied this automated thyroid segmentation system to CT scans of 20 patients. The results showed that the MALF achieved an overall 0.75 Dice Similarity Coefficient (DSC) and the RF classification further improved the DSC to 0.81.