Microwave radiative transfer intercomparison study for 3-D dichroic media

International Nuclear Information System (INIS)

Battaglia, A.; Davis, C.P.; Emde, C.; Simmer, C.

2007-01-01

Three different numerical methods capable of solving the radiative transfer of microwave radiation within 3-D dichroic media are compared. A case study, represented by an intense rain shaft populated by perfectly oriented oblate raindrops, is analysed in detail, including a discussion of the behaviour of all four Stokes components. Results demonstrate an acceptable agreement between all Monte Carlo methods. The method based on a discrete ordinates scheme agrees only qualitatively with the Monte Carlo outputs. Because of its lower computational cost the backward Monte Carlo technique based on importance sampling represents the most efficient way to face passive microwave radiative transfer problems related to optically thick 3-D structured clouds including non-spherical preferentially oriented hydrometeors

Radiative transfer equation accounting for rotational Raman scattering and its solution by the discrete-ordinates method

International Nuclear Information System (INIS)

Rozanov, Vladimir V.; Vountas, Marco

2014-01-01

Rotational Raman scattering of solar light in Earth's atmosphere leads to the filling-in of Fraunhofer and telluric lines observed in the reflected spectrum. The phenomenological derivation of the inelastic radiative transfer equation including rotational Raman scattering is presented. The different forms of the approximate radiative transfer equation with first-order rotational Raman scattering terms are obtained employing the Cabannes, Rayleigh, and Cabannes–Rayleigh scattering models. The solution of these equations is considered in the framework of the discrete-ordinates method using rigorous and approximate approaches to derive particular integrals. An alternative forward-adjoint technique is suggested as well. A detailed description of the model including the exact spectral matching and a binning scheme that significantly speeds up the calculations is given. The considered solution techniques are implemented in the radiative transfer software package SCIATRAN and a specified benchmark setup is presented to enable readers to compare with own results transparently. -- Highlights: • We derived the radiative transfer equation accounting for rotational Raman scattering. • Different approximate radiative transfer approaches with first order scattering were used. • Rigorous and approximate approaches are shown to derive particular integrals. • An alternative forward-adjoint technique is suggested as well. • An additional spectral binning scheme which speeds up the calculations is presented

Thermosolutal MHD flow and radiative heat transfer with viscous ...

African Journals Online (AJOL)

This paper investigates double diffusive convection MHD flow past a vertical porous plate in a chemically active fluid with radiative heat transfer in the presence of viscous work and heat source. The resulting nonlinear dimensionless equations are solved by asymptotic analysis technique giving approximate analytic ...

Application of nonlinear Krylov acceleration to radiative transfer problems

International Nuclear Information System (INIS)

Till, A. T.; Adams, M. L.; Morel, J. E.

2013-01-01

The iterative solution technique used for radiative transfer is normally nested, with outer thermal iterations and inner transport iterations. We implement a nonlinear Krylov acceleration (NKA) method in the PDT code for radiative transfer problems that breaks nesting, resulting in more thermal iterations but significantly fewer total inner transport iterations. Using the metric of total inner transport iterations, we investigate a crooked-pipe-like problem and a pseudo-shock-tube problem. Using only sweep preconditioning, we compare NKA against a typical inner / outer method employing GMRES / Newton and find NKA to be comparable or superior. Finally, we demonstrate the efficacy of applying diffusion-based preconditioning to grey problems in conjunction with NKA. (authors)

International symposium on radiative heat transfer: Book of abstracts

International Nuclear Information System (INIS)

1995-01-01

The international symposium on radiative heat transfer was held on 14-18 August 1995 Turkey. The specialists discussed radiation transfer in materials processing and manufacturing, solution of radiative heat transfer equation, transient radiation problem and radiation-turbulence interactions, raditive properties of gases, atmospheric and stellar radiative transfer , radiative transfer and its applications, optical and radiative properties of soot particles, inverse radiation problems, partticles, fibres,thermophoresis and waves and modelling of comprehensive systems at the meeting. Almost 79 papers were presented in the meeting

Light scattering reviews 8 radiative transfer and light scattering

CERN Document Server

Kokhanovsky, Alexander A

2013-01-01

Light scattering review (vol 8) is aimed at the presentation of recent advances in radiative transfer and light scattering optics. The topics to be covered include: scattering of light by irregularly shaped particles suspended in atmosphere (dust, ice crystals), light scattering by particles much larger as compared the wavelength of incident radiation, atmospheric radiative forcing, astrophysical radiative transfer, radiative transfer and optical imaging in biological media, radiative transfer of polarized light, numerical aspects of radiative transfer.

Free Thyroid Transfer: A Novel Procedure to Prevent Radiation-induced Hypothyroidism

International Nuclear Information System (INIS)

Harris, Jeffrey; Almarzouki, Hani; Barber, Brittany; Scrimger, Rufus; Romney, Jacques; O'Connell, Daniel; Urken, Mark; Seikaly, Hadi

2016-01-01

Purpose: The incidence of hypothyroidism after radiation therapy for head and neck cancer (HNC) has been found to be ≤53%. Medical treatment of hypothyroidism can be costly and difficult to titrate. The aim of the present study was to assess the feasibility of free thyroid transfer as a strategy for the prevention of radiation-induced damage to the thyroid gland during radiation therapy for HNC. Methods and Materials: A prospective feasibility study was performed involving 10 patients with a new diagnosis of advanced HNC undergoing ablative surgery, radial forearm free-tissue transfer reconstruction, and postoperative adjuvant radiation therapy. During the neck dissection, hemithyroid dissection was completed with preservation of the thyroid arterial and venous supply for implantation into the donor forearm site. All patients underwent a diagnostic thyroid technetium scan 6 weeks and 12 months postoperatively to examine the functional integrity of the transferred thyroid tissue. Results: Free thyroid transfer was executed in 9 of the 10 recruited patients with advanced HNC. The postoperative technetium scans demonstrated strong uptake of technetium at the forearm donor site at 6 weeks and 12 months for all 9 of the transplanted patients. Conclusions: The thyroid gland can be transferred as a microvascular free transfer with maintenance of function. This technique could represent a novel strategy for maintenance of thyroid function after head and neck irradiation.

Free Thyroid Transfer: A Novel Procedure to Prevent Radiation-induced Hypothyroidism

Energy Technology Data Exchange (ETDEWEB)

Harris, Jeffrey [Division of Otolaryngology-Head and Neck Surgery, Department of Surgery, University of Alberta, Edmonton, Alberta (Canada); Almarzouki, Hani [Division of Otolaryngology-Head and Neck Surgery, Department of Surgery, University of Alberta, Edmonton, Alberta (Canada); Department of Otolaryngology-Head and Neck Surgery, King Abdulaziz University, Jeddah (Saudi Arabia); Barber, Brittany, E-mail: brittanybarber0@gmail.com [Division of Otolaryngology-Head and Neck Surgery, Department of Surgery, University of Alberta, Edmonton, Alberta (Canada); Scrimger, Rufus [Division of Radiation Oncology, Department of Oncology, University of Alberta, Edmonton, Alberta (Canada); Romney, Jacques [Division of Endocrinology and Metabolism, Department of Medicine, University of Alberta, Edmonton, Alberta (Canada); O' Connell, Daniel [Division of Otolaryngology-Head and Neck Surgery, Department of Surgery, University of Alberta, Edmonton, Alberta (Canada); Urken, Mark [Institute for Head and Neck and Thyroid Cancers, Icahn School of Medicine, Mount Sinai Hospital, New York, New York (United States); Seikaly, Hadi [Division of Otolaryngology-Head and Neck Surgery, Department of Surgery, University of Alberta, Edmonton, Alberta (Canada)

2016-09-01

Purpose: The incidence of hypothyroidism after radiation therapy for head and neck cancer (HNC) has been found to be ≤53%. Medical treatment of hypothyroidism can be costly and difficult to titrate. The aim of the present study was to assess the feasibility of free thyroid transfer as a strategy for the prevention of radiation-induced damage to the thyroid gland during radiation therapy for HNC. Methods and Materials: A prospective feasibility study was performed involving 10 patients with a new diagnosis of advanced HNC undergoing ablative surgery, radial forearm free-tissue transfer reconstruction, and postoperative adjuvant radiation therapy. During the neck dissection, hemithyroid dissection was completed with preservation of the thyroid arterial and venous supply for implantation into the donor forearm site. All patients underwent a diagnostic thyroid technetium scan 6 weeks and 12 months postoperatively to examine the functional integrity of the transferred thyroid tissue. Results: Free thyroid transfer was executed in 9 of the 10 recruited patients with advanced HNC. The postoperative technetium scans demonstrated strong uptake of technetium at the forearm donor site at 6 weeks and 12 months for all 9 of the transplanted patients. Conclusions: The thyroid gland can be transferred as a microvascular free transfer with maintenance of function. This technique could represent a novel strategy for maintenance of thyroid function after head and neck irradiation.

Radiative transfer on discrete spaces

CERN Document Server

Preisendorfer, Rudolph W; Stark, M; Ulam, S

1965-01-01

Pure and Applied Mathematics, Volume 74: Radiative Transfer on Discrete Spaces presents the geometrical structure of natural light fields. This book describes in detail with mathematical precision the radiometric interactions of light-scattering media in terms of a few well established principles.Organized into four parts encompassing 15 chapters, this volume begins with an overview of the derivations of the practical formulas and the arrangement of formulas leading to numerical solution procedures of radiative transfer problems in plane-parallel media. This text then constructs radiative tran

The Radiative Heat Transfer Properties of Molten Salts and Their Relevance to the Design of Advanced Reactors

Science.gov (United States)

Chaleff, Ethan Solomon

Molten salts, such as the fluoride salt eutectic LiF-NaF-KF (FLiNaK) or the transition metal fluoride salt KF-ZrF4, have been proposed as coolants for numerous advanced reactor concepts. These reactors are designed to operate at high temperatures where radiative heat transfer may play a significant role. If this is the case, the radiative heat transfer properties of the salt coolants are required to be known for heat transfer calculations to be performed accurately. Chapter 1 describes the existing literature and experimental efforts pertaining to radiative heat transfer in molten salts. The physics governing photon absorption by halide salts is discussed first, followed by a more specific description of experimental results pertaining to salts of interest. The phonon absorption edge in LiF-based salts such as FLiNaK is estimated and the technique described for potential use in other salts. A description is given of various spectral measurement techniques which might plausibly be employed in the present effort, as well as an argument for the use of integral techniques. Chapter 2 discusses the mathematical treatments required to approximate and solve for the radiative flux in participating materials. The differential approximation and the exact solutions to the radiative flux are examined, and methods are given to solve radiative and energy equations simultaneously. A coupled solution is used to examine radiative heat transfer to molten salt coolants. A map is generated of pipe diameters, wall temperatures, and average absorption coefficients where radiative heat transfer will increase expected heat transfer by more than 10% compared to convective methods alone. Chapter 3 presents the design and analysis of the Integral Radiative Absorption Chamber (IRAC). The IRAC employs an integral technique for the measurement of the entire electromagnetic spectrum, negating some of the challenges associated with the methods discussed in Chapter 1 at the loss of spectral

Applications of radiations, radioisotopes and nuclear techniques in biotechnology

International Nuclear Information System (INIS)

Bhatia, C.R.

1994-01-01

Applications of radiations, radioisotopes and other nuclear techniques has contributed a great deal in our understanding of microbial plant and animal biochemistry and molecular biology. Electron microscopy has provided visual evidence for molecular events. Developments in cell tissue culture of both plants and animals and immunology have contributed to advances in what we now refer as biotechnology. This paper focuses on the applications in the high-tech end of biotechnology, limited to the use of recombinant-DNA techniques. Molecular identification of the genes, their cloning and horizontal transfer across the species of microbes, plants and animals and expression of the transferred genes is the major strength of modern biotechnology. The techniques described in this paper have played a significant role in the development of biotechnology. 6 refs

Matrix-exponential description of radiative transfer

International Nuclear Information System (INIS)

Waterman, P.C.

1981-01-01

By appling the matrix-exponential operator technique to the radiative-transfer equation in discrete form, new analytical solutions are obtained for the transmission and reflection matrices in the limiting cases x >1, where x is the optical depth of the layer. Orthongonality of the eigenvectors of the matrix exponential apparently yields new conditions for determining. Chandrasekhar's characteristic roots. The exact law of reflection for the discrete eigenfunctions is also obtained. Finally, when used in conjuction with the doubling method, the matrix exponential should result in reduction in both computation time and loss of precision

Line radiative transfer and statistical equilibrium*

Directory of Open Access Journals (Sweden)

Kamp Inga

2015-01-01

Full Text Available Atomic and molecular line emission from protoplanetary disks contains key information of their detailed physical and chemical structures. To unravel those structures, we need to understand line radiative transfer in dusty media and the statistical equilibrium, especially of molecules. I describe here the basic principles of statistical equilibrium and illustrate them through the two-level atom. In a second part, the fundamentals of line radiative transfer are introduced along with the various broadening mechanisms. I explain general solution methods with their drawbacks and also specific difficulties encountered in solving the line radiative transfer equation in disks (e.g. velocity gradients. I am closing with a few special cases of line emission from disks: Radiative pumping, masers and resonance scattering.

Radiative transfer in atmosphere-sea ice-ocean system

Energy Technology Data Exchange (ETDEWEB)

Jin, Z.; Stamnes, K.; Weeks, W.F. [Univ. of Alaska, Fairbanks, AK (United States); Tsay, S.C. [NASA Goddard Space Flight Center, Greenbelt, MD (United States)

1996-04-01

Radiative energy is critical in controlling the heat and mass balance of sea ice, which significantly affects the polar climate. In the polar oceans, light transmission through the atmosphere and sea ice is essential to the growth of plankton and algae and, consequently, to the microbial community both in the ice and in the ocean. Therefore, the study of radiative transfer in the polar atmosphere, sea ice, and ocean system is of particular importance. Lacking a properly coupled radiative transfer model for the atmosphere-sea ice-ocean system, a consistent study of the radiative transfer in the polar atmosphere, snow, sea ice, and ocean system has not been undertaken before. The radiative transfer processes in the atmosphere and in the ice and ocean have been treated separately. Because the radiation processes in the atmosphere, sea ice, and ocean depend on each other, this separate treatment is inconsistent. To study the radiative interaction between the atmosphere, clouds, snow, sea ice, and ocean, a radiative transfer model with consistent treatment of radiation in the coupled system is needed and is under development.

Radiative transfer through terrestrial atmosphere and ocean: Software package SCIATRAN

International Nuclear Information System (INIS)

Rozanov, V.V.; Rozanov, A.V.; Kokhanovsky, A.A.; Burrows, J.P.

2014-01-01

SCIATRAN is a comprehensive software package for the modeling of radiative transfer processes in the terrestrial atmosphere and ocean in the spectral range from the ultraviolet to the thermal infrared (0.18–40μm) including multiple scattering processes, polarization, thermal emission and ocean–atmosphere coupling. The software is capable of modeling spectral and angular distributions of the intensity or the Stokes vector of the transmitted, scattered, reflected, and emitted radiation assuming either a plane-parallel or a spherical atmosphere. Simulations are done either in the scalar or in the vector mode (i.e. accounting for the polarization) for observations by space-, air-, ship- and balloon-borne, ground-based, and underwater instruments in various viewing geometries (nadir, off-nadir, limb, occultation, zenith-sky, off-axis). All significant radiative transfer processes are accounted for. These are, e.g. the Rayleigh scattering, scattering by aerosol and cloud particles, absorption by gaseous components, and bidirectional reflection by an underlying surface including Fresnel reflection from a flat or roughened ocean surface. The software package contains several radiative transfer solvers including finite difference and discrete-ordinate techniques, an extensive database, and a specific module for solving inverse problems. In contrast to many other radiative transfer codes, SCIATRAN incorporates an efficient approach to calculate the so-called Jacobians, i.e. derivatives of the intensity with respect to various atmospheric and surface parameters. In this paper we discuss numerical methods used in SCIATRAN to solve the scalar and vector radiative transfer equation, describe databases of atmospheric, oceanic, and surface parameters incorporated in SCIATRAN, and demonstrate how to solve some selected radiative transfer problems using the SCIATRAN package. During the last decades, a lot of studies have been published demonstrating that SCIATRAN is a valuable

Comparison of encryption techniques between chaos theory and password for wireless power transfer system: A review

Science.gov (United States)

Hussin, N. H.; Azizan, M. M.; Ali, A.; Albreem, M. A. M.

2017-09-01

This paper reviews the techniques used in Wireless power transfer (WPT). WPT is one of the most useful ways to transfer power. Based on power transfer distances, the WPT system can be divided into three categories, namely, near, medium, and far fields. Inductive coupling and capacitive coupling contactless techniques are used in the near-field WPT. Magnetic resonant coupling technique is used in the medium-field WPT. Electromagnetic radiation is used in the far-field WPT. In addition, energy encryption plays a major role in ensuring that power is transferred to the true receiver. Therefore, this paper reviews the energy encryption techniques in WPT system. A comparison between different technique shows that the distance, efficiency, and number of receivers are the main factors in selecting the suitable energy encryption technique.

Advanced Computational Methods for Thermal Radiative Heat Transfer

Energy Technology Data Exchange (ETDEWEB)

Tencer, John; Carlberg, Kevin Thomas; Larsen, Marvin E.; Hogan, Roy E.,

2016-10-01

Participating media radiation (PMR) in weapon safety calculations for abnormal thermal environments are too costly to do routinely. This cost may be s ubstantially reduced by applying reduced order modeling (ROM) techniques. The application of ROM to PMR is a new and unique approach for this class of problems. This approach was investigated by the authors and shown to provide significant reductions in the computational expense associated with typical PMR simulations. Once this technology is migrated into production heat transfer analysis codes this capability will enable the routine use of PMR heat transfer in higher - fidelity simulations of weapon resp onse in fire environments.

Radiative heat transfer in the extreme near field.

Science.gov (United States)

Kim, Kyeongtae; Song, Bai; Fernández-Hurtado, Víctor; Lee, Woochul; Jeong, Wonho; Cui, Longji; Thompson, Dakotah; Feist, Johannes; Reid, M T Homer; García-Vidal, Francisco J; Cuevas, Juan Carlos; Meyhofer, Edgar; Reddy, Pramod

2015-12-17

Radiative transfer of energy at the nanometre length scale is of great importance to a variety of technologies including heat-assisted magnetic recording, near-field thermophotovoltaics and lithography. Although experimental advances have enabled elucidation of near-field radiative heat transfer in gaps as small as 20-30 nanometres (refs 4-6), quantitative analysis in the extreme near field (less than 10 nanometres) has been greatly limited by experimental challenges. Moreover, the results of pioneering measurements differed from theoretical predictions by orders of magnitude. Here we use custom-fabricated scanning probes with embedded thermocouples, in conjunction with new microdevices capable of periodic temperature modulation, to measure radiative heat transfer down to gaps as small as two nanometres. For our experiments we deposited suitably chosen metal or dielectric layers on the scanning probes and microdevices, enabling direct study of extreme near-field radiation between silica-silica, silicon nitride-silicon nitride and gold-gold surfaces to reveal marked, gap-size-dependent enhancements of radiative heat transfer. Furthermore, our state-of-the-art calculations of radiative heat transfer, performed within the theoretical framework of fluctuational electrodynamics, are in excellent agreement with our experimental results, providing unambiguous evidence that confirms the validity of this theory for modelling radiative heat transfer in gaps as small as a few nanometres. This work lays the foundations required for the rational design of novel technologies that leverage nanoscale radiative heat transfer.

Submandibular salivary gland transfer prevents radiation-induced xerostomia

International Nuclear Information System (INIS)

Jha, Naresh; Seikaly, Hadi; McGaw, Timothy; Coulter, Linda

2000-01-01

Background: Xerostomia is a significant morbidity of radiation therapy in the management of head and neck cancers. We hypothesized that the surgical transfer of one submandibular salivary gland to submental space, outside the proposed radiation field, prior to starting radiation treatment, would prevent xerostomia. Methods: We are conducting a prospective clinical trial where the submandibular gland is transferred as part of the surgical intervention. The patients are followed clinically, with salivary flow studies and University of Washington quality of life questionnaire. Results: We report early results of 16 patients who have undergone this procedure. Seven patients have finished and 2 patients are currently undergoing radiation treatment. In 2 patients, no postoperative radiation treatment was indicated. Two patients are waiting to start radiation treatment and 2 patients refused treatment after surgery. The surgical transfer was abandoned in 1 patient. All of the transferred salivary glands were positioned outside the proposed radiation fields and were functional. The patients did not complain of any xerostomia and developed only minimal oral mucositis. There were no surgical complications. Conclusions: Surgical transfer of a submandibular salivary gland to the submental space (outside the radiation field) preserves its function and prevents the development of radiation-induced xerostomia

Super-Planckian far-field radiative heat transfer

Science.gov (United States)

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.

Assessment of the accuracy of the conventional ray-tracing technique: Implications in remote sensing and radiative transfer involving ice clouds

International Nuclear Information System (INIS)

Bi, Lei; Yang, Ping; Liu, Chao; Yi, Bingqi; Baum, Bryan A.; Diedenhoven, Bastiaan van; Iwabuchi, Hironobu

2014-01-01

A fundamental problem in remote sensing and radiative transfer simulations involving ice clouds is the ability to compute accurate optical properties for individual ice particles. While relatively simple and intuitively appealing, the conventional geometric-optics method (CGOM) is used frequently for the solution of light scattering by ice crystals. Due to the approximations in the ray-tracing technique, the CGOM accuracy is not well quantified. The result is that the uncertainties are introduced that can impact many applications. Improvements in the Invariant Imbedding T-matrix method (II-TM) and the Improved Geometric-Optics Method (IGOM) provide a mechanism to assess the aforementioned uncertainties. The results computed by the II-TM+IGOM are considered as a benchmark because the II-TM solves Maxwell's equations from first principles and is applicable to particle size parameters ranging into the domain at which the IGOM has reasonable accuracy. To assess the uncertainties with the CGOM in remote sensing and radiative transfer simulations, two independent optical property datasets of hexagonal columns are developed for sensitivity studies by using the CGOM and the II-TM+IGOM, respectively. Ice cloud bulk optical properties obtained from the two datasets are compared and subsequently applied to retrieve the optical thickness and effective diameter from Moderate Resolution Imaging Spectroradiometer (MODIS) measurements. Additionally, the bulk optical properties are tested in broadband radiative transfer (RT) simulations using the general circulation model (GCM) version of the Rapid Radiative Transfer Model (RRTMG) that is adopted in the National Center for Atmospheric Research (NCAR) Community Atmosphere Model (CAM, version 5.1). For MODIS retrievals, the mean bias of uncertainties of applying the CGOM in shortwave bands (0.86 and 2.13 μm) can be up to 5% in the optical thickness and as high as 20% in the effective diameter, depending on cloud optical

The solution of radiative transfer problems in molecular bands without the LTE assumption by accelerated lambda iteration methods

Science.gov (United States)

Kutepov, A. A.; Kunze, D.; Hummer, D. G.; Rybicki, G. B.

1991-01-01

An iterative method based on the use of approximate transfer operators, which was designed initially to solve multilevel NLTE line formation problems in stellar atmospheres, is adapted and applied to the solution of the NLTE molecular band radiative transfer in planetary atmospheres. The matrices to be constructed and inverted are much smaller than those used in the traditional Curtis matrix technique, which makes possible the treatment of more realistic problems using relatively small computers. This technique converges much more rapidly than straightforward iteration between the transfer equation and the equations of statistical equilibrium. A test application of this new technique to the solution of NLTE radiative transfer problems for optically thick and thin bands (the 4.3 micron CO2 band in the Venusian atmosphere and the 4.7 and 2.3 micron CO bands in the earth's atmosphere) is described.

Influence of radiation heat transfer during a severe accident

Energy Technology Data Exchange (ETDEWEB)

Cazares R, R. I.; Epinosa P, G.; Varela H, J. R.; Vazquez R, A. [Universidad Autonoma Metropolitana, Unidad Iztapalapa, San Rafael Atlixco No. 186, Col. Vicentina, 09340 Ciudad de Mexico (Mexico); Polo L, M. A., E-mail: ricardo-cazares@hotmail.com [Comision Nacional de Seguridad Nuclear y Salvaguardias, Dr. Barragan No. 779, Col. Narvarte, 03020 Ciudad de Mexico (Mexico)

2016-09-15

The aim of this work is to determine the influence of the radiation heat transfer on an average fuel channel during a severe accident of a BWR nuclear power plant. The analysis considers the radiation heat transfer in a participating medium, where the gases inside the system participate in the radiation heat transfer. We consider the steam-water mixture as an isothermal gray gas, and the boundaries of the system as a gray diffuse isothermal surface for the clad and refractory surfaces for the rest, and consider the average fuel channel as an enclosure system. During a severe accident, generation and diffusion of hydrogen begin at high temperature range (1,273 to 2,100 K), and the fuel rod cladding oxidation, but the hydrogen generated do not participate in the radiation heat transfer because it does not have any radiation properties. The heat transfer process in the fuel assembly is considered with a reduced order model, and from this, the convection and the radiation heat transfer is introduced in the system. In this paper, a system with and without the radiation heat transfer term was calculated and analyzed in order to obtain the influence of the radiation heat transfer on the average fuel channel. We show the behavior of radiation heat transfer effects on the temporal evolution of the hydrogen concentration and temperature profiles in a fuel assembly, where a stream of steam is flowing. Finally, this study is a practical complement for more accurate modeling of a severe accident analysis. (Author)

Influence of radiation heat transfer during a severe accident

International Nuclear Information System (INIS)

Cazares R, R. I.; Epinosa P, G.; Varela H, J. R.; Vazquez R, A.; Polo L, M. A.

2016-09-01

The aim of this work is to determine the influence of the radiation heat transfer on an average fuel channel during a severe accident of a BWR nuclear power plant. The analysis considers the radiation heat transfer in a participating medium, where the gases inside the system participate in the radiation heat transfer. We consider the steam-water mixture as an isothermal gray gas, and the boundaries of the system as a gray diffuse isothermal surface for the clad and refractory surfaces for the rest, and consider the average fuel channel as an enclosure system. During a severe accident, generation and diffusion of hydrogen begin at high temperature range (1,273 to 2,100 K), and the fuel rod cladding oxidation, but the hydrogen generated do not participate in the radiation heat transfer because it does not have any radiation properties. The heat transfer process in the fuel assembly is considered with a reduced order model, and from this, the convection and the radiation heat transfer is introduced in the system. In this paper, a system with and without the radiation heat transfer term was calculated and analyzed in order to obtain the influence of the radiation heat transfer on the average fuel channel. We show the behavior of radiation heat transfer effects on the temporal evolution of the hydrogen concentration and temperature profiles in a fuel assembly, where a stream of steam is flowing. Finally, this study is a practical complement for more accurate modeling of a severe accident analysis. (Author)

Numerical simulations of a coupled radiative?conductive heat transfer model using a modified Monte Carlo method

KAUST Repository

Kovtanyuk, Andrey E.

2012-01-01

Radiative-conductive heat transfer in a medium bounded by two reflecting and radiating plane surfaces is considered. This process is described by a nonlinear system of two differential equations: an equation of the radiative heat transfer and an equation of the conductive heat exchange. The problem is characterized by anisotropic scattering of the medium and by specularly and diffusely reflecting boundaries. For the computation of solutions of this problem, two approaches based on iterative techniques are considered. First, a recursive algorithm based on some modification of the Monte Carlo method is proposed. Second, the diffusion approximation of the radiative transfer equation is utilized. Numerical comparisons of the approaches proposed are given in the case of isotropic scattering. © 2011 Elsevier Ltd. All rights reserved.

A rapid radiative transfer model for reflection of solar radiation

Science.gov (United States)

Xiang, X.; Smith, E. A.; Justus, C. G.

1994-01-01

A rapid analytical radiative transfer model for reflection of solar radiation in plane-parallel atmospheres is developed based on the Sobolev approach and the delta function transformation technique. A distinct advantage of this model over alternative two-stream solutions is that in addition to yielding the irradiance components, which turn out to be mathematically equivalent to the delta-Eddington approximation, the radiance field can also be expanded in a mathematically consistent fashion. Tests with the model against a more precise multistream discrete ordinate model over a wide range of input parameters demonstrate that the new approximate method typically produces average radiance differences of less than 5%, with worst average differences of approximately 10%-15%. By the same token, the computational speed of the new model is some tens to thousands times faster than that of the more precise model when its stream resolution is set to generate precise calculations.

Transient radiative transfer in a scattering slab considering polarization.

Science.gov (United States)

Yi, Hongliang; Ben, Xun; Tan, Heping

2013-11-04

The characteristics of the transient and polarization must be considered for a complete and correct description of short-pulse laser transfer in a scattering medium. A Monte Carlo (MC) method combined with a time shift and superposition principle is developed to simulate transient vector (polarized) radiative transfer in a scattering medium. The transient vector radiative transfer matrix (TVRTM) is defined to describe the transient polarization behavior of short-pulse laser propagating in the scattering medium. According to the definition of reflectivity, a new criterion of reflection at Fresnel surface is presented. In order to improve the computational efficiency and accuracy, a time shift and superposition principle is applied to the MC model for transient vector radiative transfer. The results for transient scalar radiative transfer and steady-state vector radiative transfer are compared with those in published literatures, respectively, and an excellent agreement between them is observed, which validates the correctness of the present model. Finally, transient radiative transfer is simulated considering the polarization effect of short-pulse laser in a scattering medium, and the distributions of Stokes vector in angular and temporal space are presented.

A Computational Study on the Magnetic Resonance Coupling Technique for Wireless Power Transfer

Directory of Open Access Journals (Sweden)

Zakaria N.A.

2017-01-01

Full Text Available Non-radiative wireless power transfer (WPT system using magnetic resonance coupling (MRC technique has recently been a topic of discussion among researchers. This technique discussed more scenarios in mid-range field of wireless power transmission reflected to the distance and efficiency. The WPT system efficiency varies when the coupling distance between two coils involved changes. This could lead to a decisive issue of high efficient power transfer. This paper presents case studies on the relationship of operating range with the efficiency of the MRC technique. Demonstrative WPT system operates at two different frequencies are projected in order to verify performance. The resonance frequencies used are less than 100MHz within range of 10cm to 20cm.

Benchmark numerical solutions for radiative heat transfer in two-dimensional medium with graded index distribution

Energy Technology Data Exchange (ETDEWEB)

Liu, L.H. [School of Energy Science and Engineering, Harbin Institute of Technology, 92 West Dazhi Street, Harbin 150001 (China)]. E-mail: lhliu@hit.edu.cn

2006-11-15

In graded index media, the ray goes along a curved path determined by Fermat principle. Generally, the curved ray trajectory in graded index media is a complex implicit function, and the curved ray tracing is very difficult and complex. Only for some special refractive index distributions, the curved ray trajectory can be expressed as a simple explicit function. Two important examples are the layered and the radial graded index distributions. In this paper, the radiative heat transfer problems in two-dimensional square semitransparent with layered and radial graded index distributions are analyzed. After deduction of the ray trajectory, the radiative heat transfer problems are solved by using the Monte Carlo curved ray-tracing method. Some numerical solutions of dimensionless net radiative heat flux and medium temperature are tabulated as the benchmark solutions for the future development of approximation techniques for multi-dimensional radiative heat transfer in graded index media.

Nonlinear response matrix methods for radiative transfer

International Nuclear Information System (INIS)

Miller, W.F. Jr.; Lewis, E.E.

1987-01-01

A nonlinear response matrix formalism is presented for the solution of time-dependent radiative transfer problems. The essential feature of the method is that within each computational cell the temperature is calculated in response to the incoming photons from all frequency groups. Thus the updating of the temperature distribution is placed within the iterative solution of the spaceangle transport problem, instead of being placed outside of it. The method is formulated for both grey and multifrequency problems and applied in slab geometry. The method is compared to the more conventional source iteration technique. 7 refs., 1 fig., 4 tabs

Discrete diffusion Lyman α radiative transfer

Science.gov (United States)

Smith, Aaron; Tsang, Benny T.-H.; Bromm, Volker; Milosavljević, Miloš

2018-06-01

Due to its accuracy and generality, Monte Carlo radiative transfer (MCRT) has emerged as the prevalent method for Lyα radiative transfer in arbitrary geometries. The standard MCRT encounters a significant efficiency barrier in the high optical depth, diffusion regime. Multiple acceleration schemes have been developed to improve the efficiency of MCRT but the noise from photon packet discretization remains a challenge. The discrete diffusion Monte Carlo (DDMC) scheme has been successfully applied in state-of-the-art radiation hydrodynamics (RHD) simulations. Still, the established framework is not optimal for resonant line transfer. Inspired by the DDMC paradigm, we present a novel extension to resonant DDMC (rDDMC) in which diffusion in space and frequency are treated on equal footing. We explore the robustness of our new method and demonstrate a level of performance that justifies incorporating the method into existing Lyα codes. We present computational speedups of ˜102-106 relative to contemporary MCRT implementations with schemes that skip scattering in the core of the line profile. This is because the rDDMC runtime scales with the spatial and frequency resolution rather than the number of scatterings—the latter is typically ∝τ0 for static media, or ∝(aτ0)2/3 with core-skipping. We anticipate new frontiers in which on-the-fly Lyα radiative transfer calculations are feasible in 3D RHD. More generally, rDDMC is transferable to any computationally demanding problem amenable to a Fokker-Planck approximation of frequency redistribution.

SKIRT: The design of a suite of input models for Monte Carlo radiative transfer simulations

Science.gov (United States)

Baes, M.; Camps, P.

2015-09-01

The Monte Carlo method is the most popular technique to perform radiative transfer simulations in a general 3D geometry. The algorithms behind and acceleration techniques for Monte Carlo radiative transfer are discussed extensively in the literature, and many different Monte Carlo codes are publicly available. On the contrary, the design of a suite of components that can be used for the distribution of sources and sinks in radiative transfer codes has received very little attention. The availability of such models, with different degrees of complexity, has many benefits. For example, they can serve as toy models to test new physical ingredients, or as parameterised models for inverse radiative transfer fitting. For 3D Monte Carlo codes, this requires algorithms to efficiently generate random positions from 3D density distributions. We describe the design of a flexible suite of components for the Monte Carlo radiative transfer code SKIRT. The design is based on a combination of basic building blocks (which can be either analytical toy models or numerical models defined on grids or a set of particles) and the extensive use of decorators that combine and alter these building blocks to more complex structures. For a number of decorators, e.g. those that add spiral structure or clumpiness, we provide a detailed description of the algorithms that can be used to generate random positions. Advantages of this decorator-based design include code transparency, the avoidance of code duplication, and an increase in code maintainability. Moreover, since decorators can be chained without problems, very complex models can easily be constructed out of simple building blocks. Finally, based on a number of test simulations, we demonstrate that our design using customised random position generators is superior to a simpler design based on a generic black-box random position generator.

Radiation transfer and stellar atmospheres

Science.gov (United States)

Swihart, T. L.

This is a revised and expanded version of the author's Basic Physics of Stellar Atmospheres, published in 1971. The equation of transfer is considered, taking into account the intensity and derived quantities, the absorption coefficient, the emission coefficient, the source function, and special integrals for plane media. The gray atmosphere is discussed along with the nongray atmosphere, and aspects of line formation. Topics related to polarization are explored, giving attention to pure polarized radiation, general polarized radiation, transfer in a magnetic plasma, and Rayleigh scattering and the sunlit sky. Physical and astronomical constants, and a number of problems related to the subjects of the book are presented in an appendix.

Performance tuning Weather Research and Forecasting (WRF) Goddard longwave radiative transfer scheme on Intel Xeon Phi

Science.gov (United States)

Mielikainen, Jarno; Huang, Bormin; Huang, Allen H.

2015-10-01

Next-generation mesoscale numerical weather prediction system, the Weather Research and Forecasting (WRF) model, is a designed for dual use for forecasting and research. WRF offers multiple physics options that can be combined in any way. One of the physics options is radiance computation. The major source for energy for the earth's climate is solar radiation. Thus, it is imperative to accurately model horizontal and vertical distribution of the heating. Goddard solar radiative transfer model includes the absorption duo to water vapor,ozone, ozygen, carbon dioxide, clouds and aerosols. The model computes the interactions among the absorption and scattering by clouds, aerosols, molecules and surface. Finally, fluxes are integrated over the entire longwave spectrum.In this paper, we present our results of optimizing the Goddard longwave radiative transfer scheme on Intel Many Integrated Core Architecture (MIC) hardware. The Intel Xeon Phi coprocessor is the first product based on Intel MIC architecture, and it consists of up to 61 cores connected by a high performance on-die bidirectional interconnect. The coprocessor supports all important Intel development tools. Thus, the development environment is familiar one to a vast number of CPU developers. Although, getting a maximum performance out of MICs will require using some novel optimization techniques. Those optimization techniques are discusses in this paper. The optimizations improved the performance of the original Goddard longwave radiative transfer scheme on Xeon Phi 7120P by a factor of 2.2x. Furthermore, the same optimizations improved the performance of the Goddard longwave radiative transfer scheme on a dual socket configuration of eight core Intel Xeon E5-2670 CPUs by a factor of 2.1x compared to the original Goddard longwave radiative transfer scheme code.

Modeling Radiative Heat Transfer and Turbulence-Radiation Interactions in Engines

Energy Technology Data Exchange (ETDEWEB)

Paul, Chandan [Pennsylvania State Univ., University Park, PA (United States); Sircar, Arpan [Pennsylvania State Univ., University Park, PA (United States); Ferreyro-Fernandez, Sebastian [Pennsylvania State Univ., University Park, PA (United States); Imren, Abdurrahman [Pennsylvania State Univ., University Park, PA (United States); Haworth, Daniel C [Pennsylvania State Univ., University Park, PA (United States); Roy, Somesh P [Marquette University (United States); Ge, Wenjun [University of California Merced (United States); Modest, Michael F [University of California Merced (United States)

2017-04-26

Detailed radiation modelling in piston engines has received relatively little attention to date. Recently, it is being revisited in light of current trends towards higher operating pressures and higher levels of exhaust-gas recirculation, both of which enhance molecular gas radiation. Advanced high-efficiency engines also are expected to function closer to the limits of stable operation, where even small perturbations to the energy balance can have a large influence on system behavior. Here several different spectral radiation property models and radiative transfer equation (RTE) solvers have been implemented in an OpenFOAM-based engine CFD code, and simulations have been performed for a full-load (peak pressure ~200 bar) heavy-duty diesel engine. Differences in computed temperature fields, NO and soot levels, and wall heat transfer rates are shown for different combinations of spectral models and RTE solvers. The relative importance of molecular gas radiation versus soot radiation is examined. And the influence of turbulence-radiation interactions is determined by comparing results obtained using local mean values of composition and temperature to compute radiative emission and absorption with those obtained using a particle-based transported probability density function method.

A relativistic radiation transfer benchmark

International Nuclear Information System (INIS)

Munier, A.

1988-01-01

We use the integral form of the radiation transfer equation in an one dimensional slab to determine the time-dependent propagation of the radiation energy, flux and pressure in a collisionless homogeneous medium. First order v/c relativistic terms are included and the solution is given in the fluid frame and the laboratory frame

RRTM: A rapid radiative transfer model

Energy Technology Data Exchange (ETDEWEB)

Mlawer, E.J.; Taubman, S.J.; Clough, S.A. [Atmospheric and Environmental Research, Inc., Cambridge, MA (United States)

1996-04-01

A rapid radiative transfer model (RRTM) for the calculation of longwave clear-sky fluxes and cooling rates has been developed. The model, which uses the correlated-k method, is both accurate and computationally fast. The foundation for RRTM is the line-by-line radiative transfer model (LBLRTM) from which the relevant k-distributions are obtained. LBLRTM, which has been extensively validated against spectral observations e.g., the high-resolution sounder and the Atmospheric Emitted Radiance Interferometer, is used to validate the flux and cooling rate results from RRTM. Validations of RRTM`s results have been performed for the tropical, midlatitude summer, and midlatitude winter atmospheres, as well as for the four Intercomparison of Radiation Codes in Climate Models (ICRCCM) cases from the Spectral Radiance Experiment (SPECTRE). Details of some of these validations are presented below. RRTM has the identical atmospheric input module as LBLRTM, facilitating intercomparisons with LBLRTM and application of the model at the Atmospheric Radiation Measurement Cloud and Radiation Testbed sites.

Neutronics methods for thermal radiative transfer

International Nuclear Information System (INIS)

Larsen, E.W.

1988-01-01

The equations of thermal radiative transfer are time discretized in a semi-implicit manner, yielding a linear transport problem for each time step. The governing equation in this problem has the form of a neutron transport equation with fission but no scattering. Numerical methods are described, whose origins lie in neutron transport, and that have been successfully adapted to this new problem. Acceleration methods that have been developed specifically for the radiative transfer problem, but may have generalizations applicable in neutronics problems, are also discussed

Radiative transfer in type I supernovae atmospheres

International Nuclear Information System (INIS)

Isern, J.; Lopez, R.; Simonneau, E.

1987-01-01

Type I Supernovae are thought to be the result of the thermonuclear explosion of a carbon oxygen white dwarf in a close binary system. As the only direct information concerning the physics and the triggering mechanism of supernova explosions comes from the spectrophotometry of the emitted radiation, it is worthwhile to put considerable effort on the understanding of the radiation transfer in the supernovae envelopes in order to set constraints on the theoretical models of such explosions. In this paper we analyze the role played by the layers curvature on the radiative transfer. (Author)

Fundamental radiation effect on polymers energy transfer from radiation to polymer

International Nuclear Information System (INIS)

Seguchi, T.

2007-01-01

Polymer modification as cross-link, chain scission, and graft-polymerization by radiation is initiated by the quantum energy transferred from radiation to polymers. The active species for chemical reactions are produced through ionization or activation of polymer molecules for any radiation source. The energy transfer occurs mainly by ionic interaction between radiation and polymer molecule, and the contribution from the collision interaction is miner. The radiation of electromagnetic wave as X-ray or γ-ray generates the energetic electron which induces ionic interaction with polymer molecule. The energy loss profile along the penetration to polymer material is much different among the radiation sources of EB, γ-ray, and ion beams in the macroscopic mechanism. In this article, the behavior of single event, that is, the event induced by one electron, γ-ray, ion, and neutron is described by the macroscopic mechanism and by the microscopic mechanism. (authors)

Least-squares collocation meshless approach for radiative heat transfer in absorbing and scattering media

Science.gov (United States)

Liu, L. H.; Tan, J. Y.

2007-02-01

A least-squares collocation meshless method is employed for solving the radiative heat transfer in absorbing, emitting and scattering media. The least-squares collocation meshless method for radiative transfer is based on the discrete ordinates equation. A moving least-squares approximation is applied to construct the trial functions. Except for the collocation points which are used to construct the trial functions, a number of auxiliary points are also adopted to form the total residuals of the problem. The least-squares technique is used to obtain the solution of the problem by minimizing the summation of residuals of all collocation and auxiliary points. Three numerical examples are studied to illustrate the performance of this new solution method. The numerical results are compared with the other benchmark approximate solutions. By comparison, the results show that the least-squares collocation meshless method is efficient, accurate and stable, and can be used for solving the radiative heat transfer in absorbing, emitting and scattering media.

Least-squares collocation meshless approach for radiative heat transfer in absorbing and scattering media

International Nuclear Information System (INIS)

Liu, L.H.; Tan, J.Y.

2007-01-01

A least-squares collocation meshless method is employed for solving the radiative heat transfer in absorbing, emitting and scattering media. The least-squares collocation meshless method for radiative transfer is based on the discrete ordinates equation. A moving least-squares approximation is applied to construct the trial functions. Except for the collocation points which are used to construct the trial functions, a number of auxiliary points are also adopted to form the total residuals of the problem. The least-squares technique is used to obtain the solution of the problem by minimizing the summation of residuals of all collocation and auxiliary points. Three numerical examples are studied to illustrate the performance of this new solution method. The numerical results are compared with the other benchmark approximate solutions. By comparison, the results show that the least-squares collocation meshless method is efficient, accurate and stable, and can be used for solving the radiative heat transfer in absorbing, emitting and scattering media

Towards linearization of atmospheric radiative transfer in spherical geometry

International Nuclear Information System (INIS)

Walter, Holger H.; Landgraf, Jochen

2005-01-01

We present a general approach for the linearization of radiative transfer in a spherical planetary atmosphere. The approach is based on the forward-adjoint perturbation theory. In the first part we develop the theoretical background for a linearization of radiative transfer in spherical geometry. Using an operator formulation of radiative transfer allows one to derive the linearization principles in a universally valid notation. The application of the derived principles is demonstrated for a radiative transfer problem in simplified spherical geometry in the second part of this paper. Here, we calculate the derivatives of the radiance at the top of the atmosphere with respect to the absorption properties of a trace gas species in the case of a nadir-viewing satellite instrument

Higher order perturbation theory applied to radiative transfer in non-plane-parallel media

International Nuclear Information System (INIS)

Box, M.A.; Polonsky, I.N.; Davis, A.B.

2003-01-01

Radiative transfer in non-plane-parallel media is a very challenging problem, which is currently the subject of concerted efforts to develop computational techniques which may be used to tackle different tasks. In this paper we develop the full formalism for another technique, based on radiative perturbation theory. With this approach, one starts with a plane-parallel 'base model', for which many solution techniques exist, and treat the horizontal variability as a perturbation. We show that under the most logical assumption as to the base model, the first-order perturbation term is zero for domain-average radiation quantities, so that it is necessary to go to higher order terms. This requires the computation of the Green's function. While this task is by no means simple, once the various pieces have been assembled they may be re-used for any number of perturbations--that is, any horizontal variations

Development of radiation-induced mutation techniques and functional genomics studies

International Nuclear Information System (INIS)

Kim, Dong Sub; Kang, Si Yong; Kim, Jin Baek

2012-01-01

This project has been performed to develop plant genetic resources using radiation (gamma-rays, ion-beam, space environments), to conduct functional genomics studies with mutant resources, and to develop new radiation plant breeding techniques using various radiation sources during 3 years. In the first section, we developed flower genetic resources, functional crop resources, and bio-industrial plant resources. In the second section, we cloned several mutated genes and studied mechanisms of gene expression and genetic diversity of mutations induced by gamma-rays. In the third section, we developed new plant breeding techniques using gamma-phytotron, heavy ion-beam, and space environments. Based on these results, a total of 8 cultivars containing Chrysanthemum, Hibiscus, kenaf, rice, and soybean were applied for plant variety protection (PVP) and a total of 4 cultivars were registered for PVP. Also, license agreement for the dwarf type Hibiscus mutant 'Ggoma' was conducted with Supro co. and the manufacturing technology for natural antioxidant pear-grape vinegar was transferred into Enzenic co. Also, 8 gene sequences, such as F3'H and LDOX genes associated with flower color in Chrysanthemum and EPSPS gene from Korean lawn grass, were registered in the database of National Center for Biotechnology Information (NCBI). In the future study, we will develop new radiation mutation breeding techniques through the mutation spectrum induced by various radiation sources, the studies for mechanism of the cellular response to radiation, and the comparative·structural·functional genomics studies for useful traits

Strain-induced modulation of near-field radiative transfer.

Science.gov (United States)

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%.

3D radiative transfer in stellar atmospheres

International Nuclear Information System (INIS)

Carlsson, M

2008-01-01

Three-dimensional (3D) radiative transfer in stellar atmospheres is reviewed with special emphasis on the atmospheres of cool stars and applications. A short review of methods in 3D radiative transfer shows that mature methods exist, both for taking into account radiation as an energy transport mechanism in 3D (magneto-) hydrodynamical simulations of stellar atmospheres and for the diagnostic problem of calculating the emergent spectrum in more detail from such models, both assuming local thermodynamic equilibrium (LTE) and in non-LTE. Such methods have been implemented in several codes, and examples of applications are given.

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

Science.gov (United States)

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.

Role of radiation dating technique - one example

Energy Technology Data Exchange (ETDEWEB)

Watanabe, Shigueo [Universidade de Sao Paulo (IF/USP), SP (Brazil). Inst. de Fisica; Etchevarne, Carlos A. [Universidade Federal da Bahia (UFBA), Salvador, BA (Brazil). Fac. de Filosofia e Ciencias Humanas. Dept. Antropologia e Etnologia; Cano, Nilo F.; Munita, C.S. [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

2012-07-01

Full text: The great majority of archaeological or geological dating technique is based on radiation effect. The so called radioactivity method uses radioactive decays of elements. This is the case of the well known radiocarbon or carbon-14 method. Also the method of relating daughter nucleus to decaying nucleus, as in K-40/Ar-40, Th- 230/U-234, etc. Here we will concentrate in the method based on energy deposition in a solid by radiation from the disintegration of U-series and Th-series. {beta}-rays emitted by the decay of K-40 into Ca-40 (80%) and Ar-40 (11%) also contributes. The role of {alpha}, {beta} and {gamma} radiation emitted by radionuclides in the U-238 and Th-232 series and of {beta} rays from the decay of K-40, all of them in the soil irradiate anything in their course. For dating, we can have sediments as well as potteries produced by ancient people and became buried. The important process consists in transferring a fraction of the energy of radiation to the solid, mainly liberating electrons from valence band to conduction band and from there to traps. In many case the energy of the radiation is used to create defects which in turn create energy levels (traps) in the forbidden gap (or energy gap). There are three ways to recover the energy stored in the solid: (1) by emission of light optically stimulated (OSL), (2) by emission of light thermally stimulated (TL), (3) by microwave absorption (EPR or ESR). Using these techniques among several applications, we will present one to find the first settlers in the northeaster region of Brazil. (author)

Role of radiation dating technique - one example

International Nuclear Information System (INIS)

Watanabe, Shigueo

2012-01-01

Full text: The great majority of archaeological or geological dating technique is based on radiation effect. The so called radioactivity method uses radioactive decays of elements. This is the case of the well known radiocarbon or carbon-14 method. Also the method of relating daughter nucleus to decaying nucleus, as in K-40/Ar-40, Th- 230/U-234, etc. Here we will concentrate in the method based on energy deposition in a solid by radiation from the disintegration of U-series and Th-series. β-rays emitted by the decay of K-40 into Ca-40 (80%) and Ar-40 (11%) also contributes. The role of α, β and γ radiation emitted by radionuclides in the U-238 and Th-232 series and of β rays from the decay of K-40, all of them in the soil irradiate anything in their course. For dating, we can have sediments as well as potteries produced by ancient people and became buried. The important process consists in transferring a fraction of the energy of radiation to the solid, mainly liberating electrons from valence band to conduction band and from there to traps. In many case the energy of the radiation is used to create defects which in turn create energy levels (traps) in the forbidden gap (or energy gap). There are three ways to recover the energy stored in the solid: (1) by emission of light optically stimulated (OSL), (2) by emission of light thermally stimulated (TL), (3) by microwave absorption (EPR or ESR). Using these techniques among several applications, we will present one to find the first settlers in the northeaster region of Brazil. (author)

Transfer matrix method for four-flux radiative transfer.

Science.gov (United States)

Slovick, Brian; Flom, Zachary; Zipp, Lucas; Krishnamurthy, Srini

2017-07-20

We develop a transfer matrix method for four-flux radiative transfer, which is ideally suited for studying transport through multiple scattering layers. The model predicts the specular and diffuse reflection and transmission of multilayer composite films, including interface reflections, for diffuse or collimated incidence. For spherical particles in the diffusion approximation, we derive closed-form expressions for the matrix coefficients and show remarkable agreement with numerical Monte Carlo simulations for a range of absorption values and film thicknesses, and for an example multilayer slab.

Radiation scattering techniques

International Nuclear Information System (INIS)

Edmonds, E.A.

1986-01-01

Radiation backscattering techniques are useful when access to an item to be inspected is restricted to one side. These techniques are very sensitive to geometrical effects. Scattering processes and their application to the determination of voids, thickness measuring, well-logging and the use of x-ray fluorescence techniques are discussed. (U.K.)

One-dimensional solar radiative transfer: Perturbation approach and its application to independent-pixel calculations for realistic cloud fields

International Nuclear Information System (INIS)

Jerg, Matthias; Trautmann, Thomas

2007-01-01

The radiative transfer perturbation theory (RTPT), which has already been introduced in atmospheric radiative transfer several years ago, is applied to cloud related problems. The RTPT requires the solution of the radiative transfer equation in the forward and the adjoint mode. The basic principles of this technique are presented as well as its extensions to isotropic surface reflection and its conjunction with the Hermite interpolation. This set of methods is applied to different atmospheric conditions including realistic cloud scenes. The results are compared with the usual (forward) independent-pixel calculations with respect to errors of individual pixels and domain-averaged values. The RTPT turns out to be sufficiently accurate in the case the clouds' internal vertical variations remain moderate. It is also shown that, depending on the specific radiative transfer problem, the RTPT can offer some advantages on computational speed. However, the limitations of the RTPT with regard to realistic clouds are addressed as well

Atmospheric radiative transfer modeling: a summary of the AER codes

Energy Technology Data Exchange (ETDEWEB)

Clough, S.A. [Atmospheric and Environmental Research (AER) Inc., 131 Hartwell Avenue, Lexington, MA 02421-3126 (United States); Shephard, M.W. [Atmospheric and Environmental Research (AER) Inc., 131 Hartwell Avenue, Lexington, MA 02421-3126 (United States)]. E-mail: mshephar@aer.com; Mlawer, E.J. [Atmospheric and Environmental Research (AER) Inc., 131 Hartwell Avenue, Lexington, MA 02421-3126 (United States); Delamere, J.S. [Atmospheric and Environmental Research (AER) Inc., 131 Hartwell Avenue, Lexington, MA 02421-3126 (United States); Iacono, M.J. [Atmospheric and Environmental Research (AER) Inc., 131 Hartwell Avenue, Lexington, MA 02421-3126 (United States); Cady-Pereira, K. [Atmospheric and Environmental Research (AER) Inc., 131 Hartwell Avenue, Lexington, MA 02421-3126 (United States); Boukabara, S. [Atmospheric and Environmental Research (AER) Inc., 131 Hartwell Avenue, Lexington, MA 02421-3126 (United States); Brown, P.D. [Atmospheric and Environmental Research (AER) Inc., 131 Hartwell Avenue, Lexington, MA 02421-3126 (United States)

2005-03-01

The radiative transfer models developed at AER are being used extensively for a wide range of applications in the atmospheric sciences. This communication is intended to provide a coherent summary of the various radiative transfer models and associated databases publicly available from AER (http://www.rtweb.aer.com). Among the communities using the models are the remote sensing community (e.g. TES, IASI), the numerical weather prediction community (e.g. ECMWF, NCEP GFS, WRF, MM5), and the climate community (e.g. ECHAM5). Included in this communication is a description of the central features and recent updates for the following models: the line-by-line radiative transfer model (LBLRTM); the line file creation program (LNFL); the longwave and shortwave rapid radiative transfer models, RRTM{sub L}W and RRTM{sub S}W; the Monochromatic Radiative Transfer Model (MonoRTM); the MT{sub C}KD Continuum; and the Kurucz Solar Source Function. LBLRTM and the associated line parameter database (e.g. HITRAN 2000 with 2001 updates) play a central role in the suite of models. The physics adopted for LBLRTM has been extensively analyzed in the context of closure experiments involving the evaluation of the model inputs (e.g. atmospheric state), spectral radiative measurements and the spectral model output. The rapid radiative transfer models are then developed and evaluated using the validated LBLRTM model.

Development of radiation-induced mutation techniques and functional genomics studies

Energy Technology Data Exchange (ETDEWEB)

Kim, Dong Sub; Kang, Si Yong; Kim, Jin Baek [KAERI, Daejeon (Korea, Republic of); and others

2012-01-15

This project has been performed to develop plant genetic resources using radiation (gamma-rays, ion-beam, space environments), to conduct functional genomics studies with mutant resources, and to develop new radiation plant breeding techniques using various radiation sources during 3 years. In the first section, we developed flower genetic resources, functional crop resources, and bio-industrial plant resources. In the second section, we cloned several mutated genes and studied mechanisms of gene expression and genetic diversity of mutations induced by gamma-rays. In the third section, we developed new plant breeding techniques using gamma-phytotron, heavy ion-beam, and space environments. Based on these results, a total of 8 cultivars containing Chrysanthemum, Hibiscus, kenaf, rice, and soybean were applied for plant variety protection (PVP) and a total of 4 cultivars were registered for PVP. Also, license agreement for the dwarf type Hibiscus mutant 'Ggoma' was conducted with Supro co. and the manufacturing technology for natural antioxidant pear-grape vinegar was transferred into Enzenic co. Also, 8 gene sequences, such as F3'H and LDOX genes associated with flower color in Chrysanthemum and EPSPS gene from Korean lawn grass, were registered in the database of National Center for Biotechnology Information (NCBI). In the future study, we will develop new radiation mutation breeding techniques through the mutation spectrum induced by various radiation sources, the studies for mechanism of the cellular response to radiation, and the comparative{center_dot}structural{center_dot}functional genomics studies for useful traits.

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

Science.gov (United States)

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.

Radiative transfer in disc galaxies - V. The accuracy of the KB approximation

Science.gov (United States)

Lee, Dukhang; Baes, Maarten; Seon, Kwang-Il; Camps, Peter; Verstocken, Sam; Han, Wonyong

2016-12-01

We investigate the accuracy of an approximate radiative transfer technique that was first proposed by Kylafis & Bahcall (hereafter the KB approximation) and has been popular in modelling dusty late-type galaxies. We compare realistic galaxy models calculated with the KB approximation with those of a three-dimensional Monte Carlo radiative transfer code SKIRT. The SKIRT code fully takes into account of the contribution of multiple scattering whereas the KB approximation calculates only single scattered intensity and multiple scattering components are approximated. We find that the KB approximation gives fairly accurate results if optically thin, face-on galaxies are considered. However, for highly inclined (I ≳ 85°) and/or optically thick (central face-on optical depth ≳1) galaxy models, the approximation can give rise to substantial errors, sometimes, up to ≳40 per cent. Moreover, it is also found that the KB approximation is not always physical, sometimes producing infinite intensities at lines of sight with high optical depth in edge-on galaxy models. There is no `simple recipe' to correct the errors of the KB approximation that is universally applicable to any galaxy models. Therefore, it is recommended that the full radiative transfer calculation be used, even though it is slower than the KB approximation.

A passive and active microwave-vector radiative transfer (PAM-VRT) model

International Nuclear Information System (INIS)

Yang, Jun; Min, Qilong

2015-01-01

A passive and active microwave vector radiative transfer (PAM-VRT) package has been developed. This fast and accurate forward microwave model, with flexible and versatile input and output components, self-consistently and realistically simulates measurements/radiation of passive and active microwave sensors. The core PAM-VRT, microwave radiative transfer model, consists of five modules: gas absorption (two line-by-line databases and four fast models); hydrometeor property of water droplets and ice (spherical and nonspherical) particles; surface emissivity (from Community Radiative Transfer Model (CRTM)); vector radiative transfer of successive order of scattering (VSOS); and passive and active microwave simulation. The PAM-VRT package has been validated against other existing models, demonstrating good accuracy. The PAM-VRT not only can be used to simulate or assimilate measurements of existing microwave sensors, but also can be used to simulate observation results at some new microwave sensors. - Highlights: • A novel microwave vector radiative transfer model is developed. • It can simulate passive and active microwave radiative transfer simultaneously. • It can be applied to simulate measurements for different types of viewing geometry. • The accuracy of this model has been validated against other existing models

Experimental study of overall heat transfer coefficient in the application of dilute nanofluids in the car radiator

International Nuclear Information System (INIS)

Peyghambarzadeh, S.M.; Hashemabadi, S.H.; Naraki, M.; Vermahmoudi, Y.

2013-01-01

Heat transfer of coolant flow through the automobile radiators is of great importance for the optimization of fuel consumption. In this study, the heat transfer performance of the automobile radiator is evaluated experimentally by calculating the overall heat transfer coefficient (U) according to the conventional ε-NTU technique. Copper oxide (CuO) and Iron oxide (Fe 2 O 3 ) nanoparticles are added to the water at three concentrations 0.15, 0.4, and 0.65 vol.% with considering the best pH for longer stability. In these experiments, the liquid side Reynolds number is varied in the range of 50–1000 and the inlet liquid to the radiator has a constant temperature which is changed at 50, 65 and 80 °C. The ambient air for cooling of the hot liquid is used at constant temperature and the air Reynolds number is varied between 500 and 700. However, the effects of these variables on the overall heat transfer coefficient are deeply investigated. Results demonstrate that both nanofluids show greater overall heat transfer coefficient in comparison with water up to 9%. Furthermore, increasing the nanoparticle concentration, air velocity, and nanofluid velocity enhances the overall heat transfer coefficient. In contrast, increasing the nanofluid inlet temperature, lower overall heat transfer coefficient was recorded. -- Highlights: ► Overall heat transfer coefficient in the car radiator measured experimentally. ► Nanofluids showed greater heat transfer performance comparing with water. ► Increasing liquid and air Re increases the overall heat transfer coefficient. ► Increasing the inlet liquid temperature decreases the overall heat transfer coefficient

The technique on handling radiation

International Nuclear Information System (INIS)

1997-11-01

This book describes measurement of radiation and handling radiation. The first part deals with measurement of radiation. The contents of this part are characteristic on measurement technique of radiation, radiation detector, measurement of energy spectrum, measurement of radioactivity, measurement for a level of radiation and county's statistics on radiation. The second parts explains handling radiation with treating of sealed radioisotope, treating unsealed source and radiation shield.

A hybrid transport-diffusion Monte Carlo method for frequency-dependent radiative-transfer simulations

International Nuclear Information System (INIS)

Densmore, Jeffery D.; Thompson, Kelly G.; Urbatsch, Todd J.

2012-01-01

Discrete Diffusion Monte Carlo (DDMC) is a technique for increasing the efficiency of Implicit Monte Carlo radiative-transfer simulations in optically thick media. In DDMC, particles take discrete steps between spatial cells according to a discretized diffusion equation. Each discrete step replaces many smaller Monte Carlo steps, thus improving the efficiency of the simulation. In this paper, we present an extension of DDMC for frequency-dependent radiative transfer. We base our new DDMC method on a frequency-integrated diffusion equation for frequencies below a specified threshold, as optical thickness is typically a decreasing function of frequency. Above this threshold we employ standard Monte Carlo, which results in a hybrid transport-diffusion scheme. With a set of frequency-dependent test problems, we confirm the accuracy and increased efficiency of our new DDMC method.

Some fundamental considerations of the equation of radiative transfer

International Nuclear Information System (INIS)

Kuriyan, J.G.; Sudarshan, E.C.G.

1978-10-01

The radiation transfer of the vector electromagnetic field was first formulated by Chandrasekhar while deriving the polarization characteristics of a sunlit sky. There are two subtle problems underlying this treatment. The first concerns the crucial identification of a Stokes parameter with the specific intensity of radiation. While both depend on position in 3-D space, the latter has, intrinsic to it, an additional angular dependence defining the flow of the radiation field. How can this inadequacy be remedied without damaging the results obtained heretofore from Chandrasekhar's formalism. The second problem arises from the fact that the radiative transfer equation describes the transport of an incoherent radiation field through space. This, however, seems to contradict the results of the Van Cittert-Zernike-Wolf theorem which implies that an incoherent field develops coherence as it passes through free space implying, of course, that the radiative transfer equation must involve not incoherent but partially coherent fields. The vector transfer equation of the direct beam (Beer's law) is derived from first principles. The analysis of this equation provides a satisfactory resolution of these two problems. The result also shows that the Beer's law will have to be modified to a matrix law to accommodate systems that are not spherically symmetric. 13 references

Radiation techniques in crop and plant breeding. Multiplying the benefits

International Nuclear Information System (INIS)

Ahloowalia, B.S.

1998-01-01

World food production is based on growing a wide variety of fruits, vegetables, and crops developed through advances in science. Plant breeders have produced multiple varieties that grow well in various types of soils and under diverse climates in different regions of the world. Conventionally, this is done by sexual hybridization. This involves transferring pollen from one parent plant to another to obtain hybrids. The subsequent generations of these hybrids are grown to select plants which combine the desired characters of the parents. However, another method exists by which the genetic make-up of a given plant variety can be changed without crossing with another variety. With this method, a variety retains all its original attributes but is upgraded in one or two changed characteristics. This method is based on radiation-induced genetic changes, and its referred to as ''induced mutations''. During the past thirty years, more than 1800 mutant varieties of plants have been released, many, of which were induced with radiation. Plant tissue and cell culture (also called in vitro culture) in combination with radiation is a powerful technique to induce mutations, particularly for the improvement of vegetatively propagated crops. These crops include cassava, garlic, potato, sweet potato, yams, sugarcane, ornamentals such as chrysanthemum, carnation, roses, tulips, daffodil, and many fruits (e.g. apple, banana, plantain, citrus, date palm, grape, papaya, passion fruit, and kiwi fruit). In some of these plants, either there is no seed set (e.g. banana) or the seed progeny produces plants which do not have the right combination of the desired characteristics. These techniques are also useful in the improvement of forest trees having a long lifespan before they produce fruit and seed. This article briefly reviews advances in plant breeding techniques, with a view towards improving the transfer of technologies to more countries

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

Science.gov (United States)

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.

SEURAT: SPH scheme extended with ultraviolet line radiative transfer

Science.gov (United States)

Abe, Makito; Suzuki, Hiroyuki; Hasegawa, Kenji; Semelin, Benoit; Yajima, Hidenobu; Umemura, Masayuki

2018-05-01

We present a novel Lyman alpha (Ly α) radiative transfer code, SEURAT (SPH scheme Extended with Ultraviolet line RAdiative Transfer), where line scatterings are solved adaptively with the resolution of the smoothed particle hydrodynamics (SPH). The radiative transfer method implemented in SEURAT is based on a Monte Carlo algorithm in which the scattering and absorption by dust are also incorporated. We perform standard test calculations to verify the validity of the code; (i) emergent spectra from a static uniform sphere, (ii) emergent spectra from an expanding uniform sphere, and (iii) escape fraction from a dusty slab. Thereby, we demonstrate that our code solves the {Ly} α radiative transfer with sufficient accuracy. We emphasize that SEURAT can treat the transfer of {Ly} α photons even in highly complex systems that have significantly inhomogeneous density fields. The high adaptivity of SEURAT is desirable to solve the propagation of {Ly} α photons in the interstellar medium of young star-forming galaxies like {Ly} α emitters (LAEs). Thus, SEURAT provides a powerful tool to model the emergent spectra of {Ly} α emission, which can be compared to the observations of LAEs.

Maximal near-field radiative heat transfer between two plates

Science.gov (United States)

Nefzaoui, Elyes; Ezzahri, Younès; Drévillon, Jérémie; Joulain, Karl

2013-09-01

Near-field radiative transfer is a promising way to significantly and simultaneously enhance both thermo-photovoltaic (TPV) devices power densities and efficiencies. A parametric study of Drude and Lorentz models performances in maximizing near-field radiative heat transfer between two semi-infinite planes separated by nanometric distances at room temperature is presented in this paper. Optimal parameters of these models that provide optical properties maximizing the radiative heat flux are reported and compared to real materials usually considered in similar studies, silicon carbide and heavily doped silicon in this case. Results are obtained by exact and approximate (in the extreme near-field regime and the electrostatic limit hypothesis) calculations. The two methods are compared in terms of accuracy and CPU resources consumption. Their differences are explained according to a mesoscopic description of nearfield radiative heat transfer. Finally, the frequently assumed hypothesis which states a maximal radiative heat transfer when the two semi-infinite planes are of identical materials is numerically confirmed. Its subsequent practical constraints are then discussed. Presented results enlighten relevant paths to follow in order to choose or design materials maximizing nano-TPV devices performances.

Unsteady coupling of Navier-Stokes and radiative heat transfer solvers applied to an anisothermal multicomponent turbulent channel flow

International Nuclear Information System (INIS)

Amaya, J.; Cabrit, O.; Poitou, D.; Cuenot, B.; El Hafi, M.

2010-01-01

Direct numerical simulations (DNS) of an anisothermal reacting turbulent channel flow with and without radiative source terms have been performed to study the influence of the radiative heat transfer on the optically non-homogeneous boundary layer structure. A methodology for the study of the emitting/absorbing turbulent boundary layer (TBL) is presented. Details on the coupling strategy and the parallelization techniques are exposed. An analysis of the first order statistics is then carried out. It is shown that, in the studied configuration, the global structure of the thermal boundary layer is not significantly modified by radiation. However, the radiative transfer mechanism is not negligible and contributes to the heat losses at the walls. The classical law-of-the-wall for temperature can thus be improved for RANS/LES simulations taking into account the radiative contribution.

Asymptotic equilibrium diffusion analysis of time-dependent Monte Carlo methods for grey radiative transfer

International Nuclear Information System (INIS)

Densmore, Jeffery D.; Larsen, Edward W.

2004-01-01

The equations of nonlinear, time-dependent radiative transfer are known to yield the equilibrium diffusion equation as the leading-order solution of an asymptotic analysis when the mean-free path and mean-free time of a photon become small. We apply this same analysis to the Fleck-Cummings, Carter-Forest, and N'kaoua Monte Carlo approximations for grey (frequency-independent) radiative transfer. Although Monte Carlo simulation usually does not require the discretizations found in deterministic transport techniques, Monte Carlo methods for radiative transfer require a time discretization due to the nonlinearities of the problem. If an asymptotic analysis of the equations used by a particular Monte Carlo method yields an accurate time-discretized version of the equilibrium diffusion equation, the method should generate accurate solutions if a time discretization is chosen that resolves temperature changes, even if the time steps are much larger than the mean-free time of a photon. This analysis is of interest because in many radiative transfer problems, it is a practical necessity to use time steps that are large compared to a mean-free time. Our asymptotic analysis shows that: (i) the N'kaoua method has the equilibrium diffusion limit, (ii) the Carter-Forest method has the equilibrium diffusion limit if the material temperature change during a time step is small, and (iii) the Fleck-Cummings method does not have the equilibrium diffusion limit. We include numerical results that verify our theoretical predictions

Nonlinear radiative heat transfer to stagnation-point flow of Sisko fluid past a stretching cylinder

Energy Technology Data Exchange (ETDEWEB)

Khan, Masood [Department of Mathematics, Quaid-i-Azam University, Islamabad 44000 (Pakistan); Malik, Rabia, E-mail: rabiamalik.qau@gmail.com [Department of Mathematics, Quaid-i-Azam University, Islamabad 44000 (Pakistan); Department of Mathematics and Statistics, International Islamic University Islamabad 44000 (Pakistan); Hussain, M. [Department of Sciences and Humanities, National University of Computer and Emerging Sciences, Islamabad 44000 (Pakistan)

2016-05-15

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, heat 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.

Nonlinear radiative heat transfer to stagnation-point flow of Sisko fluid past a stretching cylinder

Directory of Open Access Journals (Sweden)

Masood Khan

2016-05-01

Full Text Available 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, heat 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.

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

Science.gov (United States)

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.

Discontinuous Galerkin finite element methods for radiative transfer in spherical symmetry

Science.gov (United States)

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.

Radiative transfer in molecular lines

Science.gov (United States)

Asensio Ramos, A.; Trujillo Bueno, J.; Cernicharo, J.

2001-07-01

The highly convergent iterative methods developed by Trujillo Bueno and Fabiani Bendicho (1995) for radiative transfer (RT) applications are generalized to spherical symmetry with velocity fields. These RT methods are based on Jacobi, Gauss-Seidel (GS), and SOR iteration and they form the basis of a new NLTE multilevel transfer code for atomic and molecular lines. The benchmark tests carried out so far are presented and discussed. The main aim is to develop a number of powerful RT tools for the theoretical interpretation of molecular spectra.

Simulation of Radiation Heat Transfer in a VAR Furnace Using an Electrical Resistance Network

Science.gov (United States)

Ballantyne, A. Stewart

The use of electrical resistance networks to simulate heat transfer is a well known analytical technique that greatly simplifies the solution of radiation heat transfer problems. In a VAR furnace, radiative heat transfer occurs between the ingot, electrode, and crucible wall; and the arc when the latter is present during melting. To explore the relative heat exchange between these elements, a resistive network model was developed to simulate the heat exchange between the electrode, ingot, and crucible with and without the presence of an arc. This model was then combined with an ingot model to simulate the VAR process and permit a comparison between calculated and observed results during steady state melting. Results from simulations of a variety of alloys of different sizes have demonstrated the validity of the model. Subsequent simulations demonstrate the application of the model to the optimization of both steady state and hot top melt practices, and raises questions concerning heat flux assumptions at the ingot top surface.

Three-dimensional transfer of solar radiation in clouds

International Nuclear Information System (INIS)

Davies, R.

1976-01-01

The results of a theoretical study of the effects of cloud geometry on the transfer of incident solar radiation is presented. These results indicate that a three-dimensional description of cloud geometry is a necessary prerequisite to the accurate determination of the emerging radiation field. Models which make the plane parallel assumption are therefore frequently inadequate. Both a Monte Carlo method and an analytic method were used to model the three-dimensional transfer of radiation. At the expense of considerable computation time the Monte Carlo model provides accurate values of the fluxes and intensities (averages over π/30 steradians) emerging from clouds which can be described as a set of connected cuboidal cells, each cell being homogeneous with respect to extinction coefficient, single scatter albedo and phase function. The analytic model, based on an extension of Eddington's approximation to three dimensions and to anisotropic scattering, is efficient to use, but is restricted to clouds made up of a single cuboidal cell and is more accurate for large clouds than small ones. By an iterated approach, involving integration of the source function along line of sight, the analytic model provides both fluxes and intensities of the emerging radiation at any specified point on the cloud's surface. These models were both applied to a systematic study of the transfer of solar radiation in isolated cuboidal clouds of arbitraty dimensions, the results of which illustrate the importance of considering the total cloud geometry in any attempt at realistic modelling. A study of the transfer of radiation in stratiform clouds with turretted top surfaces also indicated that even for these clouds the plane parallel assumption was often not tenable

Radiation techniques for acromegaly

Directory of Open Access Journals (Sweden)

Minniti Giuseppe

2011-12-01

Full Text Available Abstract Radiotherapy (RT remains an effective treatment in patients with acromegaly refractory to medical and/or surgical interventions, with durable tumor control and biochemical remission; however, there are still concerns about delayed biochemical effect and potential late toxicity of radiation treatment, especially high rates of hypopituitarism. Stereotactic radiotherapy has been developed as a more accurate technique of irradiation with more precise tumour localization and consequently a reduction in the volume of normal tissue, particularly the brain, irradiated to high radiation doses. Radiation can be delivered in a single fraction by stereotactic radiosurgery (SRS or as fractionated stereotactic radiotherapy (FSRT in which smaller doses are delivered over 5-6 weeks in 25-30 treatments. A review of the recent literature suggests that pituitary irradiation is an effective treatment for acromegaly. Stereotactic techniques for GH-secreting pituitary tumors are discussed with the aim to define the efficacy and potential adverse effects of each of these techniques.

Radiation techniques for acromegaly

International Nuclear Information System (INIS)

Minniti, Giuseppe; Scaringi, Claudia; Enrici, Riccardo Maurizi

2011-01-01

Radiotherapy (RT) remains an effective treatment in patients with acromegaly refractory to medical and/or surgical interventions, with durable tumor control and biochemical remission; however, there are still concerns about delayed biochemical effect and potential late toxicity of radiation treatment, especially high rates of hypopituitarism. Stereotactic radiotherapy has been developed as a more accurate technique of irradiation with more precise tumour localization and consequently a reduction in the volume of normal tissue, particularly the brain, irradiated to high radiation doses. Radiation can be delivered in a single fraction by stereotactic radiosurgery (SRS) or as fractionated stereotactic radiotherapy (FSRT) in which smaller doses are delivered over 5-6 weeks in 25-30 treatments. A review of the recent literature suggests that pituitary irradiation is an effective treatment for acromegaly. Stereotactic techniques for GH-secreting pituitary tumors are discussed with the aim to define the efficacy and potential adverse effects of each of these techniques

Simulation of solar radiative transfer in cumulus clouds

Energy Technology Data Exchange (ETDEWEB)

Zuev, V.E.; Titov, G.A. [Institute of Atmospheric Optics, Tomsk (Russian Federation)

1996-04-01

This work presents a 3-D model of radiative transfer which is used to study the relationship between the spatial distribution of cumulus clouds and fluxes (albedo and transmittance) of visible solar radiation.

Radiative heat transfer by the Monte Carlo method

CERN Document Server

Hartnett †, James P; Cho, Young I; Greene, George A; Taniguchi, Hiroshi; Yang, Wen-Jei; Kudo, Kazuhiko

1995-01-01

This book presents the basic principles and applications of radiative heat transfer used in energy, space, and geo-environmental engineering, and can serve as a reference book for engineers and scientists in researchand development. A PC disk containing software for numerical analyses by the Monte Carlo method is included to provide hands-on practice in analyzing actual radiative heat transfer problems.Advances in Heat Transfer is designed to fill the information gap between regularly scheduled journals and university level textbooks by providing in-depth review articles over a broader scope than journals or texts usually allow.Key Features* Offers solution methods for integro-differential formulation to help avoid difficulties* Includes a computer disk for numerical analyses by PC* Discusses energy absorption by gas and scattering effects by particles* Treats non-gray radiative gases* Provides example problems for direct applications in energy, space, and geo-environmental engineering

Radiation effects on heat transfer in heat exchangers, (2)

International Nuclear Information System (INIS)

Mori, Yasuo; Watanabe, Kenji; Taira, Tatsuji.

1980-01-01

In a high temperature gas-cooled reactor system, in which the working fluid exchanges heat at high temperature near 1000 deg C, the heat transfer acceleration by positively utilizing the radiation heat transfer between solid surfaces should be considered. This paper reports on the results of experiment and analysis for the effects of radiant heat on the heat transfer performance at elevated temperature by applying the heat transfer-accelerating method using radiators to the heat exchanger with tube bundle composed of two channels of heating and heated sides. As the test heat exchangers, a parallel counter flow exchanger and the cross flow exchanger simulating helical tubes were employed, and the results studied on the characteristics of each heat exchanger are described. The plates placed in parallel to flow in every space of the tube bundle arranged in a matrix were used as the heat transfer accelerator. The effects of acceleration with the plates were the increase of heat transmission from 12 to 24% and 12 to 38% in the parallel flow and cross flow heat exchangers, respectively. Also, it was clarified that the theoretical analysis, in which it was assumed that the region within pitch S and two radiator plates, with a heat-transferring tube placed at the center, is the minimum domain for calculation, and that the heat exchange by radiation occurs only between the domain and the adjacent domains, can estimate the heat transfer-accelerating effect and the temperature distribution in a heat exchanger with sufficient accuracy. (Wakatsuki, Y.)

Heat transfer in Rockwool modelling and method of measurement. Modelling radiative heat transfer in fibrous materials

Energy Technology Data Exchange (ETDEWEB)

Dyrboel, Susanne

1998-05-01

Fibrous materials are some of the most widely used materials for thermal insulation. In this project the focus of interest has been on fibrous materials for building application. Interest in improving the thermal properties of insulation materials is increasing as legislation is being tightened to reduce the overall energy consumption. A knowledge of the individual heat transfer mechanisms - whereby heat is transferred within a particular material is an essential tool to improve continuously the thermal properties of the material. Heat is transferred in fibrous materials by four different transfer mechanisms: conduction through air, conduction through fibres, thermal radiation and convection. In a particular temperature range the conduction through air can be regarded as a constant, and conduction through fibres is an insignificant part of the total heat transfer. Radiation, however, constitutes 25-40% of the total heat transfer in light fibrous materials. In Denmark and a number of other countries convection in fibrous materials is considered as non-existent when calculating heat transmission as well as when designing building structures. Two heat transfer mechanisms have been the focus of the current project: radiation heat transfer and convection. The radiation analysis serves to develop a model that can be used in further work to gain a wider knowledge of the way in which the morphology of the fibrous material, i.e. fibre diameter distribution, fibre orientation distribution etc., influences the radiation heat transfer under different conditions. The convection investigation serves to examine whether considering convection as non-existent is a fair assumption to use in present and future building structures. The assumption applied in practically is that convection makes a notable difference only in very thick insulation, at external temperatures below -20 deg. C, and at very low densities. For lager thickness dimensions the resulting heat transfer through the

Non-Gaussian Stochastic Radiation Transfer in Finite Planar Media with Quadratic Scattering

International Nuclear Information System (INIS)

Sallah, M.

2016-01-01

The stochastic radiation transfer is considered in a participating planar finite continuously fluctuating medium characterized by non-Gaussian variability. The problem is considered for diffuse-reflecting boundaries with quadratic Rayleigh scattering. Random variable transformation (RVT) technique is used to get the complete average for the solution functions that are represented by the probability-density function (PDF) of the solution process. RVT algorithm applies a simple integral transformation to the input stochastic process (the extinction function of the medium). This linear transformation enables us to rewrite the stochastic transport equations in terms of the optical random variable (x) and the optical random thickness (L). Then the radiation transfer equation is solved deterministically to get a closed form for the solution as a function of x and L. So, the solution is used to obtain the PDF of the solution functions applying the RVT technique among the input random variable (L) and the output process (the solution functions). The obtained averages of the solution functions are used to get the complete analytical averages for some interesting physical quantities, namely, reflectivity, transmissivity and partial heat fluxes at the medium boundaries. Numerical results are represented graphically for different non-Gaussian probability distribution functions that compared with the corresponding Gaussian PDF.

A computer simulation model to compute the radiation transfer of mountainous regions

Science.gov (United States)

Li, Yuguang; Zhao, Feng; Song, Rui

2011-11-01

In mountainous regions, the radiometric signal recorded at the sensor depends on a number of factors such as sun angle, atmospheric conditions, surface cover type, and topography. In this paper, a computer simulation model of radiation transfer is designed and evaluated. This model implements the Monte Carlo ray-tracing techniques and is specifically dedicated to the study of light propagation in mountainous regions. The radiative processes between sun light and the objects within the mountainous region are realized by using forward Monte Carlo ray-tracing methods. The performance of the model is evaluated through detailed comparisons with the well-established 3D computer simulation model: RGM (Radiosity-Graphics combined Model) based on the same scenes and identical spectral parameters, which shows good agreements between these two models' results. By using the newly developed computer model, series of typical mountainous scenes are generated to analyze the physical mechanism of mountainous radiation transfer. The results show that the effects of the adjacent slopes are important for deep valleys and they particularly affect shadowed pixels, and the topographic effect needs to be considered in mountainous terrain before accurate inferences from remotely sensed data can be made.

Radiation heat transfer within an open-cycle MHD generator channel

Science.gov (United States)

Delil, A. A. M.

1983-05-01

Radiation heat transfer in an MHD generator was modeled using the Sparrow and Cess model for radiation in an emitting, absorbing and scattering medium. The resulting general equations can be considerably reduced by introducing simplifying approximations for the channel and MHD gas properties. The simplifications lead to an engineering model, which is very useful for one-dimensional channel flow approximation. The model can estimate thermo-optical MHD gas properties, which can be substituted in the energy equation. The model considers the contribution of solid particles in the MHD gas to radiation heat transfer, considerable in coal-fired closed cycle MHD generators. The modeling is applicable also for other types of flow at elevated temperatures, where radiation heat transfer is an important quantity.

Radiation heat transfer model for the SCDAP code

International Nuclear Information System (INIS)

Sohal, M.S.

1984-01-01

A radiation heat transfer model has been developed for severe fuel damage analysis which accounts for anisotropic effects of reflected radiation. The model simplifies the view factor calculation which results in significant savings in computational cost with little loss of accuracy. Radiation heat transfer rates calculated by the isotropic and anisotropic models compare reasonably well with those calculated by other models. The model is applied to an experimental nuclear rod bundle during a slow boiloff of the coolant liquid, a situation encountered during a loss of coolant accident with severe fuel damage. At lower temperatures and also lower temperature gradients in the core, the anisotropic effect was not found to be significant

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

Science.gov (United States)

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

Food physics and radiation techniques

International Nuclear Information System (INIS)

Szabo, A. S.

1999-01-01

In the lecture information is given about food physics, which is a rather new, interdisciplinary field of science, connecting food science and applied physics. The topics of radioactivity of foodstuffs and radiation techniques in the food industry are important parts of food physics detailed information will be given about the main fields (e.g. radio stimulation, food preservation) of radiation techniques in the agro-food sector. Finally some special questions of radioactive contamination of foodstuffs in hungary and applicability of radioanalytical techniques (e.g. Inaa) for food investigation will be analyzed and discussed

Comptonization in Ultra-Strong Magnetic Fields: Numerical Solution to the Radiative Transfer Problem

Science.gov (United States)

Ceccobello, C.; Farinelli, R.; Titarchuk, L.

2014-01-01

We consider the radiative transfer problem in a plane-parallel slab of thermal electrons in the presence of an ultra-strong magnetic field (B approximately greater than B(sub c) approx. = 4.4 x 10(exp 13) G). Under these conditions, the magnetic field behaves like a birefringent medium for the propagating photons, and the electromagnetic radiation is split into two polarization modes, ordinary and extraordinary, that have different cross-sections. When the optical depth of the slab is large, the ordinary-mode photons are strongly Comptonized and the photon field is dominated by an isotropic component. Aims. The radiative transfer problem in strong magnetic fields presents many mathematical issues and analytical or numerical solutions can be obtained only under some given approximations. We investigate this problem both from the analytical and numerical point of view, provide a test of the previous analytical estimates, and extend these results with numerical techniques. Methods. We consider here the case of low temperature black-body photons propagating in a sub-relativistic temperature plasma, which allows us to deal with a semi-Fokker-Planck approximation of the radiative transfer equation. The problem can then be treated with the variable separation method, and we use a numerical technique to find solutions to the eigenvalue problem in the case of a singular kernel of the space operator. The singularity of the space kernel is the result of the strong angular dependence of the electron cross-section in the presence of a strong magnetic field. Results. We provide the numerical solution obtained for eigenvalues and eigenfunctions of the space operator, and the emerging Comptonization spectrum of the ordinary-mode photons for any eigenvalue of the space equation and for energies significantly lesser than the cyclotron energy, which is on the order of MeV for the intensity of the magnetic field here considered. Conclusions. We derived the specific intensity of the

Near-field radiative heat transfer between clusters of dielectric nanoparticles

International Nuclear Information System (INIS)

Dong, J.; Zhao, J.M.; Liu, L.H.

2017-01-01

In this work, we explore the near-field radiative heat transfer between two clusters of silicon carbide (SiC) nanoparticles using the many-body radiative heat transfer theory. The effects of fractal dimension of clusters, many-body interaction between nanoparticles and relative orientation of clusters on the thermal conductance are studied. Meanwhile, the applicability of the equivalent volume spheres (EVS) approximation for near-field radiative heat transfer between clusters is examined. It is observed that the thermal conductance is larger for clusters with larger fractal dimension, which is more significant in the near-field. The thermal conductance of EVS resembles that of the clusters, but EVS overestimates the conductance of clusters, especially in the near-field. Compared to the case of two nanoparticles, the conductance of nanoparticle clusters decays much slower with increasing distance in the near-field, but shares similar dependence on the distance in the far-field. The thermal conductance of SiC nanoparticle clusters is inhibited by the many-body interaction when surface phonon polariton is supported but enhanced at frequencies close to the resonance frequency. The total thermal conductance is decreased due to many-body interaction among particles in the cluster. The relative orientation between the clusters is also an important factor in the near-field, especially for clusters with lower fractal dimension. - Highlights: • Near-field radiative heat transfer between clusters of nanoparticles is studied. • The many-body radiative heat transfer theory is applied for rigorous analysis. • The accuracy of equivalent volume spheres approximation is examined. • Clusters with larger fractal dimension have larger radiative thermal conductance. • Many-body interaction inhibits the total radiative thermal conductance.

Maximal near-field radiative heat transfer between two plates

OpenAIRE

Nefzaoui, Elyes; Ezzahri, Younès; Drevillon, Jérémie; Joulain, Karl

2013-01-01

International audience; Near-field radiative transfer is a promising way to significantly and simultaneously enhance both thermo-photovoltaic (TPV) devices power densities and efficiencies. A parametric study of Drude and Lorentz models performances in maximizing near-field radiative heat transfer between two semi-infinite planes separated by nanometric distances at room temperature is presented in this paper. Optimal parameters of these models that provide optical properties maximizing the r...

SCIATRAN 3.1: A new radiative transfer model and retrieval package

Science.gov (United States)

Rozanov, Alexei; Rozanov, Vladimir; Kokhanovsky, Alexander; Burrows, John P.

The SCIATRAN 3.1 package is a result of further development of the SCIATRAN 2.X software family which, similar to previous versions, comprises a radiative transfer model and a retrieval block. After an implementation of the vector radiative transfer model in SCIATRAN 3.0 the spectral range covered by the model has been extended into the thermal infrared ranging to approximately 40 micrometers. Another major improvement has been done accounting for the underlying surface effects. Among others, a sophisticated representation of the water surface with a bidirectional reflection distribution function (BRDF) has been implemented accounting for the Fresnel reflection of the polarized light and for the effect of foam. A newly developed representation for a snow surface allows radiative transfer calculations to be performed within an unpolluted or soiled snow layer. Furthermore, a new approach has been implemented allowing radiative transfer calculations to be performed for a coupled atmosphere-ocean system. This means that, the underlying ocean is not considered as a purely reflecting surface any more. Instead, full radiative transfer calculations are performed within the water allowing the user to simulate the radiance within both the atmosphere and the ocean. Similar to previous versions, the simulations can be performed for any viewing geometry typi-cal for atmospheric observations in the UV-Vis-NIR-TIR spectral range (nadir, limb, off-axis, etc.) as well as for any observer location within or outside the Earth's atmosphere including underwater observations. Similar to the precursor version, the new model is freely available for non-commercial use via the web page of the University of Bremen. In this presentation a short description of the software package, especially of the new features of the radiative transfer model is given, including remarks on the availability for the scientific community. Furthermore, some application examples of the radiative transfer model are

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

Science.gov (United States)

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

Polarimetric and angular light-scattering from dense media: Comparison of a vectorial radiative transfer model with analytical, stochastic and experimental approaches

International Nuclear Information System (INIS)

Riviere, Nicolas; Ceolato, Romain; Hespel, Laurent

2013-01-01

Our work presents computations via a vectorial radiative transfer model of the polarimetric and angular light scattered by a stratified dense medium with small and intermediate optical thickness. We report the validation of this model using analytical results and different computational methods like stochastic algorithms. Moreover, we check the model with experimental data from a specific scatterometer developed at the Onera. The advantages and disadvantages of a radiative approach are discussed. This paper represents a step toward the characterization of particles in dense media involving multiple scattering. -- Highlights: • A vectorial radiative transfer model to simulate the light scattered by stratified layers is developed. • The vectorial radiative transfer equation is solved using an adding–doubling technique. • The results are compared to analytical and stochastic data. • Validation with experimental data from a scatterometer developed at Onera is presented

Utrecht Radiative Transfer Courses

Science.gov (United States)

Rutten, R. J.

2003-01-01

The Utrecht course ``The Generation and Transport of Radiation'' teaches basic radiative transfer to second-year students. It is a much-expanded version of the first chapter of Rybicki & Lightman's ``Radiative Processes in Astrophysics''. After this course, students understand why intensity is measured per steradian, have an Eddington-Barbier feel for optically thick line formation, and know that scattering upsets LTE. The text is a computer-aided translation by Ruth Peterson of my 1992 Dutch-language course. My aim is to rewrite this course in non-computer English and make it web-available at some time. In the meantime, copies of the Peterson translation are made yearly at Uppsala -- ask them, not me. Eventually it should become a textbook. The Utrecht course ``Radiative Transfer in Stellar Atmospheres'' is a 30-hour course for third-year students. It treats NLTE line formation in plane-parallel stellar atmospheres at a level intermediate between the books by Novotny and Boehm-Vitense, and Mihalas' ``Stellar Atmospheres''. After this course, students appreciate that epsilon is small, that radiation can heat or cool, and that computers have changed the field. This course is web-available since 1995 and is regularly improved -- but remains incomplete. Eventually it should become a textbook. The three Utrecht exercise sets ``Stellar Spectra A: Basic Line Formation'', ``Stellar Spectra B: LTE Line Formation'', and ``Stellar Spectra C: NLTE Line Formation'' are IDL-based computer exercises for first-year, second-year, and third-year students, respectively. They treat spectral classification, Saha-Boltzmann population statistics, the curve of growth, the FAL-C solar atmosphere model, the role of H-minus in the solar continuum, LTE formation of Fraunhofer lines, inversion tactics, the Feautrier method, classical lambda iteration, and ALI computation. The first two sets are web-available since 1998; the third will follow. Acknowledgement. Both courses owe much to previous

Introduction of Parallel GPGPU Acceleration Algorithms for the Solution of Radiative Transfer

Science.gov (United States)

Godoy, William F.; Liu, Xu

2011-01-01

General-purpose computing on graphics processing units (GPGPU) is a recent technique that allows the parallel graphics processing unit (GPU) to accelerate calculations performed sequentially by the central processing unit (CPU). To introduce GPGPU to radiative transfer, the Gauss-Seidel solution of the well-known expressions for 1-D and 3-D homogeneous, isotropic media is selected as a test case. Different algorithms are introduced to balance memory and GPU-CPU communication, critical aspects of GPGPU. Results show that speed-ups of one to two orders of magnitude are obtained when compared to sequential solutions. The underlying value of GPGPU is its potential extension in radiative solvers (e.g., Monte Carlo, discrete ordinates) at a minimal learning curve.

One-dimensional transient radiative transfer by lattice Boltzmann method.

Science.gov (United States)

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.

Monte Carlo method for polarized radiative transfer in gradient-index media

International Nuclear Information System (INIS)

Zhao, J.M.; Tan, J.Y.; Liu, L.H.

2015-01-01

Light transfer in gradient-index media generally follows curved ray trajectories, which will cause light beam to converge or diverge during transfer and induce the rotation of polarization ellipse even when the medium is transparent. Furthermore, the combined process of scattering and transfer along curved ray path makes the problem more complex. In this paper, a Monte Carlo method is presented to simulate polarized radiative transfer in gradient-index media that only support planar ray trajectories. The ray equation is solved to the second order to address the effect induced by curved ray trajectories. Three types of test cases are presented to verify the performance of the method, which include transparent medium, Mie scattering medium with assumed gradient index distribution, and Rayleigh scattering with realistic atmosphere refractive index profile. It is demonstrated that the atmospheric refraction has significant effect for long distance polarized light transfer. - Highlights: • A Monte Carlo method for polarized radiative transfer in gradient index media. • Effect of curved ray paths on polarized radiative transfer is considered. • Importance of atmospheric refraction for polarized light transfer is demonstrated

Formal Solutions for Polarized Radiative Transfer. III. Stiffness and Instability

Science.gov (United States)

Janett, Gioele; Paganini, Alberto

2018-04-01

Efficient numerical approximation of the polarized radiative transfer equation is challenging because this system of ordinary differential equations exhibits stiff behavior, which potentially results in numerical instability. This negatively impacts the accuracy of formal solvers, and small step-sizes are often necessary to retrieve physical solutions. This work presents stability analyses of formal solvers for the radiative transfer equation of polarized light, identifies instability issues, and suggests practical remedies. In particular, the assumptions and the limitations of the stability analysis of Runge–Kutta methods play a crucial role. On this basis, a suitable and pragmatic formal solver is outlined and tested. An insightful comparison to the scalar radiative transfer equation is also presented.

BARTTest: Community-Standard Atmospheric Radiative-Transfer and Retrieval Tests

Science.gov (United States)

Harrington, Joseph; Himes, Michael D.; Cubillos, Patricio E.; Blecic, Jasmina; Challener, Ryan C.

2018-01-01

Atmospheric radiative transfer (RT) codes are used both to predict planetary and brown-dwarf spectra and in retrieval algorithms to infer atmospheric chemistry, clouds, and thermal structure from observations. Observational plans, theoretical models, and scientific results depend on the correctness of these calculations. Yet, the calculations are complex and the codes implementing them are often written without modern software-verification techniques. The community needs a suite of test calculations with analytically, numerically, or at least community-verified results. We therefore present the Bayesian Atmospheric Radiative Transfer Test Suite, or BARTTest. BARTTest has four categories of tests: analytically verified RT tests of simple atmospheres (single line in single layer, line blends, saturation, isothermal, multiple line-list combination, etc.), community-verified RT tests of complex atmospheres, synthetic retrieval tests on simulated data with known answers, and community-verified real-data retrieval tests.BARTTest is open-source software intended for community use and further development. It is available at https://github.com/ExOSPORTS/BARTTest. We propose this test suite as a standard for verifying atmospheric RT and retrieval codes, analogous to the Held-Suarez test for general circulation models. This work was supported by NASA Planetary Atmospheres grant NX12AI69G, NASA Astrophysics Data Analysis Program grant NNX13AF38G, and NASA Exoplanets Research Program grant NNX17AB62G.

Line radiative transfer and statistical equilibrium

NARCIS (Netherlands)

Kamp, Inga

Atomic and molecular line emission from protoplanetary disks contains key information of their detailed physical and chemical structures. To unravel those structures, we need to understand line radiative transfer in dusty media and the statistical equilibrium, especially of molecules. I describe

Numerical studies of heat transfer by simultaneous radiative-conduction and radiative-convection in a two dimensional semi-transparent medium

International Nuclear Information System (INIS)

Draoui, Abdeslam

1989-01-01

The works we present here are on numerical approaches of heat transfer coupling radiation-conduction and radiation-convection within semi-transparent two-dimensional medium. The first part deals with a review of equations of radiative transfer and introduces three numerical methods (Pl, P3, Hottel's zones) which enable one to solve this problem in a two-dimensional environment. After comparing the three methods in the case where radiation is the only mode of transfer, we introduce in the second chapter a study of the coupling of radiation with conduction. So, a fourth method is used to solve this problem. These comparisons lead us to various methods which enable us to show the interest of the spherical harmonics approximations. In the third part, the Pl approximation is kept because it is simple to use, moreover it enables us to introduce both the coupling of radiative transfers with laminar convective equations in a thermally driven two-dimensional cavity. The results show a significant influence of the radiative participation of the fluid on heat and dynamic transfer we met in this type of problem. (author) [fr

Heat transfer analysis in a calorimeter for concentrated solar radiation measurements

Energy Technology Data Exchange (ETDEWEB)

Estrada, C.A.; Jaramillo, O.A.; Arancibia-Bulnes, C.A. [Universidad Nacional Autonoma de Mexico, Centro de Investigacion en Energia, Privada Xochicalco S/N, Col. Centro. Temixco, Morelos 62580 (Mexico); Acosta, R. [Universidad de Quintana Roo, Boulevard Bahia s/n Esq. I. Comonfort, Chetumal Quintana Roo 77019 (Mexico)

2007-10-15

A calorimeter was built for measuring the concentrated solar power produced by a point focus solar concentrator that was developed at CIE - UNAM. In order to obtain a thermal characterization of the calorimeter a theoretical and experimental heat transfer study is carried out. This study addresses the heat transfer in the circular flat plate of the calorimeter, which acts as receiver for the concentrating system. Temperatures are measured at different points of this plate and fit with a theoretical model that considers heat conduction with convective and radiative boundary conditions. In particular, it is possible to calculate the temperature distribution on the irradiated surface. This allows to examine the validity of the assumptions of cold water calorimetry, which was the technique applied to this system in previous works. (author)

Techniques of radiation dosimetry

International Nuclear Information System (INIS)

Mahesk, K.

1985-01-01

A text and reference with an interdisciplinary approach to physics, atomic energy, radiochemistry, and radiobiology. Chapters examine basic principles, experimental techniques, the methodology of dose experiments, and applications. Treats 14 different dosimetric techniques, including ionization chamber, thermoluminescence, and lyoluminescence. Considers the conceptual aspects and characteristic features of radiation

Intercomparison of three microwave/infrared high resolution line-by-line radiative transfer codes

Science.gov (United States)

Schreier, Franz; Milz, Mathias; Buehler, Stefan A.; von Clarmann, Thomas

2018-05-01

An intercomparison of three line-by-line (lbl) codes developed independently for atmospheric radiative transfer and remote sensing - ARTS, GARLIC, and KOPRA - has been performed for a thermal infrared nadir sounding application assuming a HIRS-like (High resolution Infrared Radiation Sounder) setup. Radiances for the 19 HIRS infrared channels and a set of 42 atmospheric profiles from the "Garand dataset" have been computed. The mutual differences of the equivalent brightness temperatures are presented and possible causes of disagreement are discussed. In particular, the impact of path integration schemes and atmospheric layer discretization is assessed. When the continuum absorption contribution is ignored because of the different implementations, residuals are generally in the sub-Kelvin range and smaller than 0.1 K for some window channels (and all atmospheric models and lbl codes). None of the three codes turned out to be perfect for all channels and atmospheres. Remaining discrepancies are attributed to different lbl optimization techniques. Lbl codes seem to have reached a maturity in the implementation of radiative transfer that the choice of the underlying physical models (line shape models, continua etc) becomes increasingly relevant.

Matrix formulations of radiative transfer including the polarization effect in a coupled atmosphere-ocean system

International Nuclear Information System (INIS)

Ota, Yoshifumi; Higurashi, Akiko; Nakajima, Teruyuki; Yokota, Tatsuya

2010-01-01

A vector radiative transfer model has been developed for a coupled atmosphere-ocean system. The radiative transfer scheme is based on the discrete ordinate and matrix operator methods. The reflection/transmission matrices and source vectors are obtained for each atmospheric or oceanic layer through the discrete ordinate solution. The vertically inhomogeneous system is constructed using the matrix operator method, which combines the radiative interaction between the layers. This radiative transfer scheme is flexible for a vertically inhomogeneous system including the oceanic layers as well as the ocean surface. Compared with the benchmark results, the computational error attributable to the radiative transfer scheme has been less than 0.1% in the case of eight discrete ordinate directions. Furthermore, increasing the number of discrete ordinate directions has produced computations with higher accuracy. Based on our radiative transfer scheme, simulations of sun glint radiation have been presented for wavelengths of 670 nm and 1.6 μm. Results of simulations have shown reasonable characteristics of the sun glint radiation such as the strongly peaked, but slightly smoothed radiation by the rough ocean surface and depolarization through multiple scattering by the aerosol-loaded atmosphere. The radiative transfer scheme of this paper has been implemented to the numerical model named Pstar as one of the OpenCLASTR/STAR radiative transfer code systems, which are widely applied to many radiative transfer problems, including the polarization effect.

Radiatively driven relativistic spherical winds under relativistic radiative transfer

Science.gov (United States)

Fukue, J.

2018-05-01

We numerically investigate radiatively driven relativistic spherical winds from the central luminous object with mass M and luminosity L* under Newtonian gravity, special relativity, and relativistic radiative transfer. We solve both the relativistic radiative transfer equation and the relativistic hydrodynamical equations for spherically symmetric flows under the double-iteration processes, to obtain the intensity and velocity fields simultaneously. We found that the momentum-driven winds with scattering are quickly accelerated near the central object to reach the terminal speed. The results of numerical solutions are roughly fitted by a relation of \\dot{m}=0.7(Γ _*-1)\\tau _* β _* β _out^{-2.6}, where \\dot{m} is the mass-loss rate normalized by the critical one, Γ* the central luminosity normalized by the critical one, τ* the typical optical depth, β* the initial flow speed at the central core of radius R*, and βout the terminal speed normalized by the speed of light. This relation is close to the non-relativistic analytical solution, \\dot{m} = 2(Γ _*-1)\\tau _* β _* β _out^{-2}, which can be re-expressed as β _out^2/2 = (Γ _*-1)GM/c^2 R_*. That is, the present solution with small optical depth is similar to that of the radiatively driven free outflow. Furthermore, we found that the normalized luminosity (Eddington parameter) must be larger than unity for the relativistic spherical wind to blow off with intermediate or small optical depth, i.e. Γ _* ≳ \\sqrt{(1+β _out)^3/(1-β _out)}. We briefly investigate and discuss an isothermal wind.

On similarity and scaling of the radiative transfer equation

International Nuclear Information System (INIS)

Mitrescu, C.; Stephens, G.L.

2004-01-01

The present paper shows how the well-known similarity and scaling concepts are properties of the radiative transfer equation and not specifically of the degree of anisotropy of the phase function. It is shown that the key assumption regarding the angular dependence of the radiative field is essential in determining both the value for the parameter used to scale the radiative transfer, as well as the number of streams used in calculating the radiances for various atmospheric problems. Simulations performed on realistic type of cirrus clouds, characterized by strongly anisotropic functions, demonstrates the superior computational advantage for accurately simulating radiances. A new approach for determining the scaling parameter is introduced

Heat transfer augmentation of a car radiator using nanofluids

Science.gov (United States)

Hussein, Adnan M.; Bakar, R. A.; Kadirgama, K.; Sharma, K. V.

2014-05-01

The car radiator heat transfer enhancement by using TiO2 and SiO2 nanoparticles dispersed in water as a base fluid was studied experimentally. The test rig is setup as a car radiator with tubes and container. The range of Reynolds number and volume fraction are (250-1,750) and (1.0-2.5 %) respectively. Results showed that the heat transfer increases with increasing of nanofluid volume fraction. The experimental data is agreed with other investigator.

A study of Monte Carlo radiative transfer through fractal clouds

Energy Technology Data Exchange (ETDEWEB)

Gautier, C.; Lavallec, D.; O`Hirok, W.; Ricchiazzi, P. [Univ. of California, Santa Barbara, CA (United States)] [and others

1996-04-01

An understanding of radiation transport (RT) through clouds is fundamental to studies of the earth`s radiation budget and climate dynamics. The transmission through horizontally homogeneous clouds has been studied thoroughly using accurate, discreet ordinates radiative transfer models. However, the applicability of these results to general problems of global radiation budget is limited by the plane parallel assumption and the fact that real clouds fields show variability, both vertically and horizontally, on all size scales. To understand how radiation interacts with realistic clouds, we have used a Monte Carlo radiative transfer model to compute the details of the photon-cloud interaction on synthetic cloud fields. Synthetic cloud fields, generated by a cascade model, reproduce the scaling behavior, as well as the cloud variability observed and estimated from cloud satellite data.

A fast infrared radiative transfer model for overlapping clouds

International Nuclear Information System (INIS)

Niu Jianguo; Yang Ping; Huang Hunglung; Davies, James E.; Li Jun; Baum, Bryan A.; Hu, Yong X.

2007-01-01

A fast infrared radiative transfer model (FIRTM2) appropriate for application to both single-layered and overlapping cloud situations is developed for simulating the outgoing infrared spectral radiance at the top of the atmosphere (TOA). In FIRTM2 a pre-computed library of cloud reflectance and transmittance values is employed to account for one or two cloud layers, whereas the background atmospheric optical thickness due to gaseous absorption can be computed from a clear-sky radiative transfer model. FIRTM2 is applicable to three atmospheric conditions: (1) clear-sky (2) single-layered ice or water cloud, and (3) two simultaneous cloud layers in a column (e.g., ice cloud overlying water cloud). Moreover, FIRTM2 outputs the derivatives (i.e., Jacobians) of the TOA brightness temperature with respect to cloud optical thickness and effective particle size. Sensitivity analyses have been carried out to assess the performance of FIRTM2 for two spectral regions, namely the longwave (LW) band (587.3-1179.5 cm -1 ) and the short-to-medium wave (SMW) band (1180.1-2228.9 cm -1 ). The assessment is carried out in terms of brightness temperature differences (BTD) between FIRTM2 and the well-known discrete ordinates radiative transfer model (DISORT), henceforth referred to as BTD (F-D). The BTD (F-D) values for single-layered clouds are generally less than 0.8 K. For the case of two cloud layers (specifically ice cloud over water cloud), the BTD (F-D) values are also generally less than 0.8 K except for the SMW band for the case of a very high altitude (>15 km) cloud comprised of small ice particles. Note that for clear-sky atmospheres, FIRTM2 reduces to the clear-sky radiative transfer model that is incorporated into FIRTM2, and the errors in this case are essentially those of the clear-sky radiative transfer model

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

Science.gov (United States)

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.

Gas Temperature and Radiative Heat Transfer in Oxy-fuel Flames

DEFF Research Database (Denmark)

Bäckström, Daniel; Johansson, Robert; Andersson, Klas

This work presents measurements of the gas temperature, including fluctuations, and its influence on the radiative heat transfer in oxy-fuel flames. The measurements were carried out in the Chalmers 100 kW oxy-fuel test unit. The in-furnace gas temperature was measured by a suction pyrometer...... on the radiative heat transfer shows no effect of turbulence-radiation interaction. However, by comparing with temperature fluctuations in other flames it can be seen that the fluctuations measured here are relatively small. Further research is needed to clarify to which extent the applied methods can account...

Bridging the Radiative Transfer Models for Meteorology and Solar Energy Applications

Science.gov (United States)

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.

On the derivation of vector radiative transfer equation for polarized radiative transport in graded index media

International Nuclear Information System (INIS)

Zhao, J.M.; Tan, J.Y.; Liu, L.H.

2012-01-01

Light transport in graded index media follows a curved trajectory determined by Fermat's principle. Besides the effect of variation of the refractive index on the transport of radiative intensity, the curved ray trajectory will induce geometrical effects on the transport of polarization ellipse. This paper presents a complete derivation of vector radiative transfer equation for polarized radiation transport in absorption, emission and scattering graded index media. The derivation is based on the analysis of the conserved quantities for polarized light transport along curved trajectory and a novel approach. The obtained transfer equation can be considered as a generalization of the classic vector radiative transfer equation that is only valid for uniform refractive index media. Several variant forms of the transport equation are also presented, which include the form for Stokes parameters defined with a fixed reference and the Eulerian forms in the ray coordinate and in several common orthogonal coordinate systems.

Near-field radiative heat transfer between graphene-covered hyperbolic metamaterials

Science.gov (United States)

Hong, Xiao-Juan; Li, Jian-Wen; Wang, Tong-Biao; Zhang, De-Jian; Liu, Wen-Xing; Liao, Qing-Hua; Yu, Tian-Bao; Liu, Nian-Hua

2018-04-01

We propose the use of graphene-covered silicon carbide (SiC) nanowire arrays (NWAs) for theoretical studies of near-field radiative heat transfer. The SiC NWAs exhibit a hyperbolic characteristic at an appropriately selected filling-volume fraction. The surface plasmon supported by graphene and the hyperbolic modes supported by SiC NWAs significantly affect radiative heat transfer. The heat-transfer coefficient (HTC) between the proposed structures is larger than that between SiC NWAs. We also find that the chemical potential of graphene plays an important role in modulating the HTC. The tunability of chemical potential through gate voltage enables flexible control of heat transfer using the graphene-covered SiC NWAs.

Analysing CMS transfers using Machine Learning techniques

CERN Document Server

Diotalevi, Tommaso

2016-01-01

LHC experiments transfer more than 10 PB/week between all grid sites using the FTS transfer service. In particular, CMS manages almost 5 PB/week of FTS transfers with PhEDEx (Physics Experiment Data Export). FTS sends metrics about each transfer (e.g. transfer rate, duration, size) to a central HDFS storage at CERN. The work done during these three months, here as a Summer Student, involved the usage of ML techniques, using a CMS framework called DCAFPilot, to process this new data and generate predictions of transfer latencies on all links between Grid sites. This analysis will provide, as a future service, the necessary information in order to proactively identify and maybe fix latency issued transfer over the WLCG.

IPRT polarized radiative transfer model intercomparison project - Three-dimensional test cases (phase B)

Science.gov (United States)

Emde, Claudia; Barlakas, Vasileios; Cornet, Céline; Evans, Frank; Wang, Zhen; Labonotte, Laurent C.; Macke, Andreas; Mayer, Bernhard; Wendisch, Manfred

2018-04-01

Initially unpolarized solar radiation becomes polarized by scattering in the Earth's atmosphere. In particular molecular scattering (Rayleigh scattering) polarizes electromagnetic radiation, but also scattering of radiation at aerosols, cloud droplets (Mie scattering) and ice crystals polarizes. Each atmospheric constituent produces a characteristic polarization signal, thus spectro-polarimetric measurements are frequently employed for remote sensing of aerosol and cloud properties. Retrieval algorithms require efficient radiative transfer models. Usually, these apply the plane-parallel approximation (PPA), assuming that the atmosphere consists of horizontally homogeneous layers. This allows to solve the vector radiative transfer equation (VRTE) efficiently. For remote sensing applications, the radiance is considered constant over the instantaneous field-of-view of the instrument and each sensor element is treated independently in plane-parallel approximation, neglecting horizontal radiation transport between adjacent pixels (Independent Pixel Approximation, IPA). In order to estimate the errors due to the IPA approximation, three-dimensional (3D) vector radiative transfer models are required. So far, only a few such models exist. Therefore, the International Polarized Radiative Transfer (IPRT) working group of the International Radiation Commission (IRC) has initiated a model intercomparison project in order to provide benchmark results for polarized radiative transfer. The group has already performed an intercomparison for one-dimensional (1D) multi-layer test cases [phase A, 1]. This paper presents the continuation of the intercomparison project (phase B) for 2D and 3D test cases: a step cloud, a cubic cloud, and a more realistic scenario including a 3D cloud field generated by a Large Eddy Simulation (LES) model and typical background aerosols. The commonly established benchmark results for 3D polarized radiative transfer are available at the IPRT website (http

Best estimate radiation heat transfer model developed for TRAC-BD1

International Nuclear Information System (INIS)

Spore, J.W.; Giles, M.M.; Shumway, R.W.

1981-01-01

A best estimate radiation heat transfer model for analysis of BWR fuel bundles has been developed and compared with 8 x 8 fuel bundle data. The model includes surface-to-surface and surface-to-two-phase fluid radiation heat transfer. A simple method of correcting for anisotropic reflection effects has been included in the model

Intramolecular transfer of radiation damage in γ-irradiated nucleotides: 8,5'-cyclonucleotides

International Nuclear Information System (INIS)

Fuciarelli, A.F.; Raleigh, J.A.

1984-01-01

The transfer of radiation damage initiated in the sugar phosphate moiety to a nucleotide base as exemplified by 8,5'-cyclonucleotide formation may be important in double-stranded nucleic acids where the bases are shielded to direct hydroxyl attack. With this in mind the authors have renewed a study of the radiation chemistry of cyclonucleotides including further development of an in situ immunochemical assay for their formation in nucleic acids. 8,5'-cycloadenosine 5'-monophosphate has been prepared by radiation chemical synthesis for this purpose. The authors have discovered that the Erlanger and Bieser technique in which the cyclonucleotide hapten is attached to bovine serum albumin (BSA) through the sugar moiety may not be the best approach for preparing cyclonucleotide-containing immunogens as conformational changes may occur in the cyclonucleotide structure during this procedure. The authors are presently using an alternate approach in which the cyclonucleotide hapten is linked to BSA through the phosphate group of the nucleotide. The authors report on these experiments as well as on the basic radiation chemistry of 8,5'-cyclonucleotides

Graphene-assisted near-field radiative heat transfer between corrugated polar materials

International Nuclear Information System (INIS)

Liu, X. L.; Zhang, Z. M.

2014-01-01

Graphene has attracted great attention in nanoelectronics, optics, and energy harvesting. Here, the near-field radiative heat transfer between graphene-covered corrugated silica is investigated based on the exact scattering theory. It is found that graphene can improve the radiative heat flux between silica gratings by more than one order of magnitude and alleviate the performance sensitivity to lateral shift. The underlying mechanism is mainly attributed to the improved photon tunneling of modes away from phonon resonances. Besides, coating with graphene leads to nonlocal radiative transfer that breaks Derjaguin's proximity approximation and enables corrugated silica to outperform bulk silica in near-field radiation.

The response matrix discrete ordinates solution to the 1D radiative transfer equation

International Nuclear Information System (INIS)

Ganapol, Barry D.

2015-01-01

The discrete ordinates method (DOM) of solution to the 1D radiative transfer equation has been an effective method of solution for nearly 70 years. During that time, the method has experienced numerous improvements as numerical and computational techniques have become more powerful and efficient. Here, we again consider the analytical solution to the discrete radiative transfer equation in a homogeneous medium by proposing a new, and consistent, form of solution that improves upon previous forms. Aided by a Wynn-epsilon convergence acceleration, its numerical evaluation can achieve extreme precision as demonstrated by comparison with published benchmarks. Finally, we readily extend the solution to a heterogeneous medium through the star product formulation producing a novel benchmark for closed form Henyey–Greenstein scattering as an example. - Highlights: • Presents a new solution to the RTE called the response matrix DOM (RM/DOM). • Solution representations avoid the instability common in exponential solutions. • Explicit form in terms of matrix hyperbolic functions. • Extreme accuracy through Wynn-epsilon acceleration checked by published benchmarks. • Provides a more transparent numerical evaluation than found previously

Near-field radiative heat transfer in mesoporous alumina

International Nuclear Information System (INIS)

Li Jing; Feng Yan-Hui; Zhang Xin-Xin; Huang Cong-Liang; Wang Ge

2015-01-01

The thermal conductivity of mesoporous material has aroused the great interest of scholars due to its wide applications such as insulation, catalyst, etc. Mesoporous alumina substrate consists of uniformly distributed, unconnected cylindrical pores. Near-field radiative heat transfer cannot be ignored, when the diameters of the pores are less than the characteristic wavelength of thermal radiation. In this paper, near-field radiation across a cylindrical pore is simulated by employing the fluctuation dissipation theorem and Green function. Such factors as the diameter of the pore, and the temperature of the material are further analyzed. The research results show that the radiative heat transfer on a mesoscale is 2∼4 orders higher than on a macroscale. The heat flux and equivalent thermal conductivity of radiation across a cylindrical pore decrease exponentially with pore diameter increasing, while increase with temperature increasing. The calculated equivalent thermal conductivity of radiation is further developed to modify the thermal conductivity of the mesoporous alumina. The combined thermal conductivity of the mesoporous alumina is obtained by using porosity weighted dilute medium and compared with the measurement. The combined thermal conductivity of mesoporous silica decreases gradually with pore diameter increasing, while increases smoothly with temperature increasing, which is in good agreement with the experimental data. The larger the porosity, the more significant the near-field effect is, which cannot be ignored. (paper)

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

Science.gov (United States)

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.

Technology transfer of nuclear techniques and nucleonic control systems in the mineral industry

International Nuclear Information System (INIS)

1990-11-01

Among the many beneficial applications of radiation and radioisotopes in industry which are now well established in advanced countries, the applications of nuclear techniques and nucleonic control systems in the mineral industry have great potential for developing Member States. The use of nucleonic on-stream analyzers in the coal industry has resulted in enormous technical and economic benefits in addition to minimization of environmental pollution. Large savings have also resulted from the use of such analyzers in the processing of other minerals. Nuclear borehole logging techniques have demonstrated great potential in oil and gas evaluation. Radiotracer investigations have led to process optimisation and trouble shooting in various stages in ore processing and metallurgy. Though the technical and economic benefits of applications of nuclear techniques in the mineral industry are well recognised, technology transfer in these areas has been hampered by a variety of factors. In order to review the status and trends in nuclear techniques and nucleonic control systems in the mineral industry and the problems and considerations in their technology transfer to developing Member States, the IAEA convened an Advisory Group Meeting in Bombay, India, 15-19 January 1990. The present publication is based on the 7 contributions presented at this meeting. A separate abstract was prepared for each of these papers. Refs, figs and tabs

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

Science.gov (United States)

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.

Benchmark results in radiative transfer

International Nuclear Information System (INIS)

Garcia, R.D.M.; Siewert, C.E.

1986-02-01

Several aspects of the F N method are reported, and the method is used to solve accurately some benchmark problems in radiative transfer in the field of atmospheric physics. The method was modified to solve cases of pure scattering and an improved process was developed for computing the radiation intensity. An algorithms for computing several quantities used in the F N method was done. An improved scheme to evaluate certain integrals relevant to the method is done, and a two-term recursion relation that has proved useful for the numerical evaluation of matrix elements, basic for the method, is given. The methods used to solve the encountered linear algebric equations are discussed, and the numerical results are evaluated. (M.C.K.) [pt

Near-field radiative heat transfer between metasurfaces

DEFF Research Database (Denmark)

Dai, Jin; Dyakov, Sergey A.; Bozhevolnyi, Sergey I.

2016-01-01

Metamaterials possess artificial bulk and surface electromagnetic states. Tamed dispersion properties of surface waves allow one to achieve a controllable super-Planckian radiative heat transfer (RHT) process between two closely spaced objects. We numerically demonstrate enhanced RHT between two...... and highly geometrically tailorable. Our simulation also reveals thermally excited nonresonant surface waves in constituent metallic materials may play a prevailing role for RHT at an extremely small separation between two metal plates, rendering metamaterial modes insignificant for the energy-transfer...

TRUST. I. A 3D externally illuminated slab benchmark for dust radiative transfer

Science.gov (United States)

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

Spectral tuning of near-field radiative heat transfer by graphene-covered metasurfaces

Science.gov (United States)

Zheng, Zhiheng; Wang, Ao; Xuan, Yimin

2018-03-01

When two gratings are respectively covered by a layer of graphene sheet, the near-field radiative heat transfer between two parallel gratings made of silica (SiO2) could be greatly improved. As the material properties of doped silicon (n-type doping concentration is 1020 cm-3, marked as Si-20) and SiO2 differ greatly, we theoretically investigate the near-field radiative heat transfer between two parallel graphene-covered gratings made of Si-20 to explore some different phenomena, especially for modulating the spectral properties. The radiative heat flux between two parallel bulks made of Si-20 can be enhanced by using gratings instead of bulks. When the two gratings are respectively covered by a layer of graphene sheet, the radiative heat flux between two gratings made of Si-20 can be further enhanced. By tuning graphene chemical potential μ and grating filling factor f, due to the interaction between surface plasmon polaritons (SPPs) of graphene sheets and grating structures, the spectral properties of the radiative heat flux between two parallel graphene-covered gratings can be effectively regulated. This work will develop and supplement the effects of materials on the near-field radiative heat transfer for this kind of system configuration, paving a way to modulate the spectral properties of near-field radiative heat transfer.

Literature survey of heat transfer enhancement techniques in refrigeration applications

Energy Technology Data Exchange (ETDEWEB)

Jensen, M.K.; Shome, B. [Rensselaer Polytechnic Inst., Troy, NY (United States). Dept. of Mechanical Engineering, Aeronautical Engineering and Mechanics

1994-05-01

A survey has been performed of the technical and patent literature on enhanced heat transfer of refrigerants in pool boiling, forced convection evaporation, and condensation. Extensive bibliographies of the technical literature and patents are given. Many passive and active techniques were examined for pure refrigerants, refrigerant-oil mixtures, and refrigerant mixtures. The citations were categorized according to enhancement technique, heat transfer mode, and tube or shell side focus. The effects of the enhancement techniques relative to smooth and/or pure refrigerants were illustrated through the discussion of selected papers. Patented enhancement techniques also are discussed. Enhanced heat transfer has demonstrated significant improvements in performance in many refrigerant applications. However, refrigerant mixtures and refrigerant-oil mixtures have not been studied extensively; no research has been performed with enhanced refrigerant mixtures with oil. Most studies have been of the parametric type; there has been inadequate examination of the fundamental processes governing enhanced refrigerant heat transfer, but some modeling is being done and correlations developed. It is clear that an enhancement technique must be optimized for the refrigerant and operating condition. Fundamental processes governing the heat transfer must be examined if models for enhancement techniques are to be developed; these models could provide the method to optimize a surface. Refrigerant mixtures, with and without oil present, must be studied with enhancement devices; there is too little known to be able to estimate the effects of mixtures (particularly NARMs) with enhanced heat transfer. Other conclusions and recommendations are offered.

Non-grey benchmark results for two temperature non-equilibrium radiative transfer

International Nuclear Information System (INIS)

Su, B.; Olson, G.L.

1999-01-01

Benchmark solutions to time-dependent radiative transfer problems involving non-equilibrium coupling to the material temperature field are crucial for validating time-dependent radiation transport codes. Previous efforts on generating analytical solutions to non-equilibrium radiative transfer problems were all restricted to the one-group grey model. In this paper, a non-grey model, namely the picket-fence model, is considered for a two temperature non-equilibrium radiative transfer problem in an infinite medium. The analytical solutions, as functions of space and time, are constructed in the form of infinite integrals for both the diffusion description and transport description. These expressions are evaluated numerically and the benchmark results are generated. The asymptotic solutions for large and small times are also derived in terms of elementary functions and are compared with the exact results. Comparisons are given between the transport and diffusion solutions and between the grey and non-grey solutions. (Copyright (c) 1999 Elsevier Science B.V., Amsterdam. All rights reserved.)

A 1D radiative transfer benchmark with polarization via doubling and adding

Science.gov (United States)

Ganapol, B. D.

2017-11-01

Highly precise numerical solutions to the radiative transfer equation with polarization present a special challenge. Here, we establish a precise numerical solution to the radiative transfer equation with combined Rayleigh and isotropic scattering in a 1D-slab medium with simple polarization. The 2-Stokes vector solution for the fully discretized radiative transfer equation in space and direction derives from the method of doubling and adding enhanced through convergence acceleration. Updates to benchmark solutions found in the literature to seven places for reflectance and transmittance as well as for angular flux follow. Finally, we conclude with the numerical solution in a partially randomly absorbing heterogeneous medium.

Principles of the radiosity method versus radiative transfer for canopy reflectance modeling

Science.gov (United States)

Gerstl, Siegfried A. W.; Borel, Christoph C.

1992-01-01

The radiosity method is introduced to plant canopy reflectance modeling. We review the physics principles of the radiosity method which originates in thermal radiative transfer analyses when hot and cold surfaces are considered within a given enclosure. The radiosity equation, which is an energy balance equation for discrete surfaces, is described and contrasted with the radiative transfer equation, which is a volumetric energy balance equation. Comparing the strengths and weaknesses of the radiosity method and the radiative transfer method, we conclude that both methods are complementary to each other. Results of sample calculations are given for canopy models with up to 20,000 discrete leaves.

Validation of the community radiative transfer model

International Nuclear Information System (INIS)

Ding Shouguo; Yang Ping; Weng Fuzhong; Liu Quanhua; Han Yong; Delst, Paul van; Li Jun; Baum, Bryan

2011-01-01

To validate the Community Radiative Transfer Model (CRTM) developed by the U.S. Joint Center for Satellite Data Assimilation (JCSDA), the discrete ordinate radiative transfer (DISORT) model and the line-by-line radiative transfer model (LBLRTM) are combined in order to provide a reference benchmark. Compared with the benchmark, the CRTM appears quite accurate for both clear sky and ice cloud radiance simulations with RMS errors below 0.2 K, except for clouds with small ice particles. In a computer CPU run time comparison, the CRTM is faster than DISORT by approximately two orders of magnitude. Using the operational MODIS cloud products and the European Center for Medium-range Weather Forecasting (ECMWF) atmospheric profiles as an input, the CRTM is employed to simulate the Atmospheric Infrared Sounder (AIRS) radiances. The CRTM simulations are shown to be in reasonably close agreement with the AIRS measurements (the discrepancies are within 2 K in terms of brightness temperature difference). Furthermore, the impact of uncertainties in the input cloud properties and atmospheric profiles on the CRTM simulations has been assessed. The CRTM-based brightness temperatures (BTs) at the top of the atmosphere (TOA), for both thin (τ 30) clouds, are highly sensitive to uncertainties in atmospheric temperature and cloud top pressure. However, for an optically thick cloud, the CRTM-based BTs are not sensitive to the uncertainties of cloud optical thickness, effective particle size, and atmospheric humidity profiles. On the contrary, the uncertainties of the CRTM-based TOA BTs resulting from effective particle size and optical thickness are not negligible in an optically thin cloud.

Efficient weakly-radiative wireless energy transfer: An EIT-like approach

International Nuclear Information System (INIS)

Hamam, Rafif E.; Karalis, Aristeidis; Joannopoulos, J.D.; Soljacic, Marin

2009-01-01

Inspired by a quantum interference phenomenon known in the atomic physics community as electromagnetically induced transparency (EIT), we propose an efficient weakly radiative wireless energy transfer scheme between two identical classical resonant objects, strongly coupled to an intermediate classical resonant object of substantially different properties, but with the same resonance frequency. The transfer mechanism essentially makes use of the adiabatic evolution of an instantaneous (so called 'dark') eigenstate of the coupled 3-object system. Our analysis is based on temporal coupled mode theory (CMT), and is general enough to be valid for various possible sorts of coupling, including the resonant inductive coupling on which witricity-type wireless energy transfer is based. We show that in certain parameter regimes of interest, this scheme can be more efficient, and/or less radiative than other, more conventional approaches. A concrete example of wireless energy transfer between capacitively-loaded metallic loops is illustrated at the beginning, as a motivation for the more general case. We also explore the performance of the currently proposed EIT-like scheme, in terms of improving efficiency and reducing radiation, as the relevant parameters of the system are varied.

An anisotropic diffusion approximation to thermal radiative transfer

International Nuclear Information System (INIS)

Johnson, Seth R.; Larsen, Edward W.

2011-01-01

This paper describes an anisotropic diffusion (AD) method that uses transport-calculated AD coefficients to efficiently and accurately solve the thermal radiative transfer (TRT) equations. By assuming weak gradients and angular moments in the radiation intensity, we derive an expression for the radiation energy density that depends on a non-local function of the opacity. This nonlocal function is the solution of a transport equation that can be solved with a single steady-state transport sweep once per time step, and the function's second angular moment is the anisotropic diffusion tensor. To demonstrate the AD method's efficacy, we model radiation flow down a channel in 'flatland' geometry. (author)

Heat transfer enhancement of car radiator using aqua based magnesium oxide nanofluids

OpenAIRE

Ali Hafiz Muhammad; Azhar Muhammad Danish; Saleem Musab; Saeed Qazi Samie; Saieed Ahmed

2015-01-01

The focus of this research paper is on the application of water based MgO nanofluids for thermal management of a car radiator. Nanofluids of different volumetric concentrations (i.e. 0.06%, 0.09% and 0.12%) were prepared and then experimentally tested for their heat transfer performance in a car radiator. All concentrations showed enhancement in heat transfer compared to the pure base fluid. A peak heat transfer enhancement of 31% was obtained at 0.12 % vol...

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

Science.gov (United States)

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.

Enhancing radiative energy transfer through thermal extraction

Directory of Open Access Journals (Sweden)

Tan Yixuan

2016-06-01

Full Text Available Thermal radiation plays an increasingly important role in many emerging energy technologies, such as thermophotovoltaics, passive radiative cooling and wearable cooling clothes [1]. One of the fundamental constraints in thermal radiation is the Stefan-Boltzmann law, which limits the maximum power of far-field radiation to P0 = σT4S, where σ is the Boltzmann constant, S and T are the area and the temperature of the emitter, respectively (Fig. 1a. In order to overcome this limit, it has been shown that near-field radiations could have an energy density that is orders of magnitude greater than the Stefan-Boltzmann law [2-7]. Unfortunately, such near-field radiation transfer is spatially confined and cannot carry radiative heat to the far field. Recently, a new concept of thermal extraction was proposed [8] to enhance far-field thermal emission, which, conceptually, operates on a principle similar to oil immersion lenses and light extraction in light-emitting diodes using solid immersion lens to increase light output [62].Thermal extraction allows a blackbody to radiate more energy to the far field than the apparent limit of the Stefan-Boltzmann law without breaking the second law of thermodynamics.

Linearized vector radiative transfer model MCC++ for a spherical atmosphere

International Nuclear Information System (INIS)

Postylyakov, O.V.

2004-01-01

Application of radiative transfer models has shown that optical remote sensing requires extra characteristics of radiance field in addition to the radiance intensity itself. Simulation of spectral measurements, analysis of retrieval errors and development of retrieval algorithms are in need of derivatives of radiance with respect to atmospheric constituents under investigation. The presented vector spherical radiative transfer model MCC++ was linearized, which allows the calculation of derivatives of all elements of the Stokes vector with respect to the volume absorption coefficient simultaneously with radiance calculation. The model MCC++ employs Monte Carlo algorithm for radiative transfer simulation and takes into account aerosol and molecular scattering, gas and aerosol absorption, and Lambertian surface albedo. The model treats a spherically symmetrical atmosphere. Relation of the estimated derivatives with other forms of radiance derivatives: the weighting functions used in gas retrieval and the air mass factors used in the DOAS retrieval algorithms, is obtained. Validation of the model against other radiative models is overviewed. The computing time of the intensity for the MCC++ model is about that for radiative models treating sphericity of the atmosphere approximately and is significantly shorter than that for the full spherical models used in the comparisons. The simultaneous calculation of all derivatives (i.e. with respect to absorption in all model atmosphere layers) and the intensity is only 1.2-2 times longer than the calculation of the intensity only

A Phase II Study of Submandibular Gland Transfer Prior to Radiation for Prevention of Radiation-induced Xerostomia in Head-and-Neck Cancer (RTOG 0244)

International Nuclear Information System (INIS)

Jha, Naresh; Harris, Jonathan; Seikaly, Hadi; Jacobs, John R.; McEwan, A.J.B.; Robbins, K. Thomas; Grecula, John; Sharma, Anand K.; Ang, K. Kian

2012-01-01

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,” 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.

A Phase II Study of Submandibular Gland Transfer Prior to Radiation for Prevention of Radiation-induced Xerostomia in Head-and-Neck Cancer (RTOG 0244)

Energy Technology Data Exchange (ETDEWEB)

Jha, Naresh, E-mail: naresh.jha@albertahealthservices.ca [University of Alberta, Cross Cancer Institute, Edmonton, Alberta (Canada); Harris, Jonathan [Radiation Therapy Oncology Group Statistical Center, Philadelphia, Pennsylvania (United States); Seikaly, Hadi [University of Alberta, Edmonton, Alberta (Canada); Jacobs, John R. [Wayne State University School of Medicine, Detroit, Michigan (United States); McEwan, A.J.B. [University of Alberta, Cross Cancer Institute, Edmonton, Alberta (Canada); Robbins, K. Thomas [St. John' s Hospital Cancer Institute, Springfield, Illinois (United States); Grecula, John [Ohio State University Medical Center, Columbus, Ohio (United States); Sharma, Anand K. [Medical University of South Carolina, Charleston, South Carolina (United States); Ang, K. Kian [University of Texas MD Anderson Cancer Center, Houston, Texas (United States)

2012-10-01

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,' 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.

Enhancing radiative energy transfer through thermal extraction

Science.gov (United States)

Tan, Yixuan; Liu, Baoan; Shen, Sheng; Yu, Zongfu

2016-06-01

Thermal radiation plays an increasingly important role in many emerging energy technologies, such as thermophotovoltaics, passive radiative cooling and wearable cooling clothes [1]. One of the fundamental constraints in thermal radiation is the Stefan-Boltzmann law, which limits the maximum power of far-field radiation to P0 = σT4S, where σ is the Boltzmann constant, S and T are the area and the temperature of the emitter, respectively (Fig. 1a). In order to overcome this limit, it has been shown that near-field radiations could have an energy density that is orders of magnitude greater than the Stefan-Boltzmann law [2-7]. Unfortunately, such near-field radiation transfer is spatially confined and cannot carry radiative heat to the far field. Recently, a new concept of thermal extraction was proposed [8] to enhance far-field thermal emission, which, conceptually, operates on a principle similar to oil immersion lenses and light extraction in light-emitting diodes using solid immersion lens to increase light output [62].Thermal extraction allows a blackbody to radiate more energy to the far field than the apparent limit of the Stefan-Boltzmann law without breaking the second law of thermodynamics. Thermal extraction works by using a specially designed thermal extractor to convert and guide the near-field energy to the far field, as shown in Fig. 1b. The same blackbody as shown in Fig. 1a is placed closely below the thermal extractor with a spacing smaller than the thermal wavelength. The near-field coupling transfers radiative energy with a density greater than σT4. The thermal extractor, made from transparent and high-index or structured materials, does not emit or absorb any radiation. It transforms the near-field energy and sends it toward the far field. As a result, the total amount of far-field radiative heat dissipated by the same blackbody is greatly enhanced above SσT4, where S is the area of the emitter. This paper will review the progress in thermal

Monte Carlo techniques in radiation therapy

CERN Document Server

Verhaegen, Frank

2013-01-01

Modern cancer treatment relies on Monte Carlo simulations to help radiotherapists and clinical physicists better understand and compute radiation dose from imaging devices as well as exploit four-dimensional imaging data. With Monte Carlo-based treatment planning tools now available from commercial vendors, a complete transition to Monte Carlo-based dose calculation methods in radiotherapy could likely take place in the next decade. Monte Carlo Techniques in Radiation Therapy explores the use of Monte Carlo methods for modeling various features of internal and external radiation sources, including light ion beams. The book-the first of its kind-addresses applications of the Monte Carlo particle transport simulation technique in radiation therapy, mainly focusing on external beam radiotherapy and brachytherapy. It presents the mathematical and technical aspects of the methods in particle transport simulations. The book also discusses the modeling of medical linacs and other irradiation devices; issues specific...

Adaptation of the delta-m and δ-fit truncation methods to vector radiative transfer: Effect of truncation on radiative transfer accuracy

International Nuclear Information System (INIS)

Sanghavi, Suniti; Stephens, Graeme

2015-01-01

In the presence of aerosol and/or clouds, the use of appropriate truncation methods becomes indispensable for accurate but cost-efficient radiative transfer computations. Truncation methods allow the reduction of the large number (usually several hundreds) of Fourier components associated with particulate scattering functions to a more manageable number, thereby making it possible to carry out radiative transfer computations with a modest number of streams. While several truncation methods have been discussed for scalar radiative transfer, few rigorous studies have been made of truncation methods for the vector case. Here, we formally derive the vector form of Wiscombe's delta-m truncation method. Two main sources of error associated with delta-m truncation are identified as the delta-separation error (DSE) and the phase-truncation error (PTE). The view angles most affected by truncation error occur in the vicinity of the direction of exact backscatter. This view geometry occurs commonly in satellite based remote sensing applications, and is hence of considerable importance. In order to deal with these errors, we adapt the δ-fit approach of Hu et al. (2000) [17] to vector radiative transfer. The resulting δBGE-fit is compared with the vectorized delta-m method. For truncation at l=25 of an original phase matrix consisting of over 300 Fourier components, the use of the δBGE-fit minimizes the error due to truncation at these view angles, while practically eliminating error at other angles. We also show how truncation errors have a distorting effect on hyperspectral absorption line shapes. The choice of the δBGE-fit method over delta-m truncation minimizes errors in absorption line depths, thus affording greater accuracy for sensitive retrievals such as those of XCO 2 from OCO-2 or GOSAT measurements. - Highlights: • Derives vector form for delta-m truncation method. • Adapts δ-fit truncation approach to vector RTE as δBGE-fit. • Compares truncation

Practical applications of radiative wireless power transfer

NARCIS (Netherlands)

Pflug, H.; Visser, H.J.; Keyrouz, S.

2015-01-01

For practical use of radiative wireless power transfer (WPT), it is necessary to design a system which is able to supply circuits with a dynamic loading characteristic. In this paper we present a practical way to obtain efficiency and dc output power characteristics of a WPT system. An Avago

SMRT: A new, modular snow microwave radiative transfer model

Science.gov (United States)

Picard, Ghislain; Sandells, Melody; Löwe, Henning; Dumont, Marie; Essery, Richard; Floury, Nicolas; Kontu, Anna; Lemmetyinen, Juha; Maslanka, William; Mätzler, Christian; Morin, Samuel; Wiesmann, Andreas

2017-04-01

Forward models of radiative transfer processes are needed to interpret remote sensing data and derive measurements of snow properties such as snow mass. A key requirement and challenge for microwave emission and scattering models is an accurate description of the snow microstructure. The snow microwave radiative transfer model (SMRT) was designed to cater for potential future active and/or passive satellite missions and developed to improve understanding of how to parameterize snow microstructure. SMRT is implemented in Python and is modular to allow easy intercomparison of different theoretical approaches. Separate modules are included for the snow microstructure model, electromagnetic module, radiative transfer solver, substrate, interface reflectivities, atmosphere and permittivities. An object-oriented approach is used with carefully specified exchanges between modules to allow future extensibility i.e. without constraining the parameter list requirements. This presentation illustrates the capabilities of SMRT. At present, five different snow microstructure models have been implemented, and direct insertion of the autocorrelation function from microtomography data is also foreseen with SMRT. Three electromagnetic modules are currently available. While DMRT-QCA and Rayleigh models need specific microstructure models, the Improved Born Approximation may be used with any microstructure representation. A discrete ordinates approach with stream connection is used to solve the radiative transfer equations, although future inclusion of 6-flux and 2-flux solvers are envisioned. Wrappers have been included to allow existing microwave emission models (MEMLS, HUT, DMRT-QMS) to be run with the same inputs and minimal extra code (2 lines). Comparisons between theoretical approaches will be shown, and evaluation against field experiments in the frequency range 5-150 GHz. SMRT is simple and elegant to use whilst providing a framework for future development within the

RAPTOR. I. Time-dependent radiative transfer in arbitrary spacetimes

Science.gov (United States)

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

Heat transfer including radiation and slag particles evolution in MHD channel-I

International Nuclear Information System (INIS)

Im, K.H.; Ahluwalia, R.K.

1980-01-01

Accurate estimates of convective and radiative heat transfer in the magnetohydrodynamic channel are provided. Calculations performed for a base load-size channel indicate that heat transfer by gas radiation almost equals that by convection for smooth walls, and amounts to 70% as much as the convective heat transfer for rough walls. Carbon dioxide, water vapor, and potassium atoms are the principal participating gases. The evolution of slag particles by homogeneous nucleation and condensation is also investigated. The particle-size spectrum so computed is later utilized to analyze the radiation enhancement by slag particles in the MHD diffuser. The impact of the slag particle spectrum on the selection of a workable and design of an efficient seed collection system is discussed

Radiation techniques in the formulation of synthetic biomaterials

International Nuclear Information System (INIS)

Kaetsu, Isao

1992-01-01

This chapter reviews the uses of various radiation techniques, such as radiation polymerization, grafting, and crosslinking, for the formulation of synthetic biomaterials. The biomaterials are divided into four categories: Biocompatible polymers, immobilized proteins, immobilized cells, and drug delivery systems. The recent achievements in each category are described, and the contributions of novel radiation techniques to this field are discussed. Work on drug delivery systemsis also reviewed, and the status of the practical applications of drug delivery systems for therapy is summarized. Future trends in the field of radiation-synthesized biomaterials are indicated. (orig.)

On radiative transfer in water spray curtains using the discrete ordinates method

Energy Technology Data Exchange (ETDEWEB)

Collin, A. [Laboratoire d' Energetique et de Mecanique Theorique and Appliquee (LEMTA), CNRS UMR 7563, Faculte des Sciences et Techniques BP 239 - 54506 VANDOEUVRE Cedex (France); Boulet, P. [Laboratoire d' Energetique et de Mecanique Theorique and Appliquee (LEMTA), CNRS UMR 7563, Faculte des Sciences et Techniques BP 239 - 54506 VANDOEUVRE Cedex (France)]. E-mail: Pascal.Boulet@lemta.uhp-nancy.fr; Lacroix, D. [Laboratoire d' Energetique et de Mecanique Theorique and Appliquee (LEMTA), CNRS UMR 7563, Faculte des Sciences et Techniques BP 239 - 54506 VANDOEUVRE Cedex (France); Jeandel, G. [Laboratoire d' Energetique et de Mecanique Theorique and Appliquee (LEMTA), CNRS UMR 7563, Faculte des Sciences et Techniques BP 239 - 54506 VANDOEUVRE Cedex (France)

2005-04-15

Radiative transfer through water spray curtains has been presently addressed in conditions similar to devices used in fire protection systems. The radiation propagation from the heat source through the medium is simulated using a 2D Discrete Ordinates Method. The curtain is treated as an absorbing and anisotropically scattering medium, made of droplets injected in a mixing of air, water vapor and carbon dioxide. Such a participating medium requires a careful treatment of its spectral response in order to model the radiative transfer accurately. This particular problem is dealt with using a correlated-K method. Radiative properties for the droplets are calculated applying the Mie theory. Transmissivities under realistic conditions are then simulated after a validation thanks to comparisons with some experimental data available in the literature. Owing to promising results which are already observed in this case of uncoupled radiative problem, next step will be to combine the present study with a companion work dedicated to the careful treatment of the spray dynamics and of the induced heat transfer phenomena.

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

Science.gov (United States)

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

Techniques for materials research with synchrotron radiation x-rays

International Nuclear Information System (INIS)

Bowen, D.K.

1983-01-01

A brief introductory survey is presented of the properties and generation of synchrotron radiation and the main techniques developed so far for its application to materials problems. Headings are:synchrotron radiation; X-ray techniques in synchrotron radiation (powder diffraction; X-ray scattering; EXAFS (Extended X-ray Absorption Fine Structure); X-ray fluorescent analysis; microradiography; white radiation topography; double crystal topography); future developments. (U.K.)

Unsteady hydromagnetic free-convection flow with radiative heat transfer in a rotating fluid - I: Incompressible optically thin fluid

International Nuclear Information System (INIS)

Bestman, A.R.; Adjepong, S.K.

1987-11-01

We study the unsteady free convection flow near a moving infinite flat plate in a rotating medium by imposing a time dependent perturbation on a constant plate temperature. The temperatures involved are assumed to be very large so that radiative heat transfer is significant, which renders the problem very nonlinear even on the assumption of a differential approximation for the radiative flux. When the perturbation is small, the transient flow is tackled by the Laplace transform technique. Complete first order solutions are deduced for an impulsive motion. (author). 12 refs, 2 figs

Upper-limb biomechanical analysis of wheelchair transfer techniques in two toilet configurations.

Science.gov (United States)

Tsai, Chung-Ying; Boninger, Michael L; Bass, Sarah R; Koontz, Alicia M

2018-06-01

Using proper technique is important for minimizing upper limb kinetics during wheelchair transfers. The objective of the study was to 1) evaluate the transfer techniques used during toilet transfers and 2) determine the impact of technique on upper limb joint loading for two different toilet configurations. Twenty-six manual wheelchair users (23 men and 3 women) performed transfers in a side and front wheelchair-toilet orientation while their habitual transfer techniques were evaluated using the Transfer Assessment Instrument. A motion analysis system and force sensors were used to record biomechanical data during the transfers. More than 20% of the participants failed to complete five transfer skills in the side setup compared to three skills in the front setup. Higher quality skills overall were associated with lower peak forces and moments in both toilet configurations (-0.68 perform these skills correctly (p ≤ 0.04). In the front setup, positioning the wheelchair within three inches of the transfer target was associated with reduced peak trailing forces and moments across all three upper limb joints (p = 0.02). Transfer skills training, making toilet seats level with the wheelchair seat, positioning the wheelchair closer to the toilet and mounting grab bars in a more ideal location for persons who do sitting pivot transfers may facilitate better quality toilet transfers. Published by Elsevier Ltd.

Application of the Radiative Transfer Equation (RTE) to Scattering by ...

African Journals Online (AJOL)

Application of the Radiative Transfer Equation (RTE) to Scattering by a Dust Aerosol Layer. ... Incident radiation in its journey through the atmosphere before reaching the earth surface encounters particles of different sizes and composition such as dust aerosols resulting in interactions that lead to absorption and scattering.

Radiative heat transfer analysis in pure water heater used for semiconductor processing

International Nuclear Information System (INIS)

Liu, L.H.; Kudo, K.; Mochida, A.; Ogawa, T.; Kadotani, K.

2004-01-01

A simplified one-dimensional model is presented to analyze the non-gray radiative transfer in pure water heater used in the rinsing processes within semiconductor production lines, and the ray-tracing method is extended to simulate the radiative heat transfer. To examine the accuracy of the simplified model, the distribution of radiation absorption is determined by the ray-tracing method based the simplified model and compared with the data obtained by three-dimensional non-gray model in combination with Monte Carlo method in reference, and the effects of the water thickness on the radiation absorption are analyzed. The results show that the simplified model has a good accuracy in solving the radiation absorption in the pure water heater. The radiation absorption increases with the water thickness, but when the water thickness is greater than 50 mm, the radiation absorption increases very slowly with the water thickness

Finite element method for radiation heat transfer in multi-dimensional graded index medium

International Nuclear Information System (INIS)

Liu, L.H.; Zhang, L.; Tan, H.P.

2006-01-01

In graded index medium, ray goes along a curved path determined by Fermat principle, and curved ray-tracing is very difficult and complex. To avoid the complicated and time-consuming computation of curved ray trajectories, a finite element method based on discrete ordinate equation is developed to solve the radiative transfer problem in a multi-dimensional semitransparent graded index medium. Two particular test problems of radiative transfer are taken as examples to verify this finite element method. The predicted dimensionless net radiative heat fluxes are determined by the proposed method and compared with the results obtained by finite volume method. The results show that the finite element method presented in this paper has a good accuracy in solving the multi-dimensional radiative transfer problem in semitransparent graded index medium

Fast and simple model for atmospheric radiative transfer

NARCIS (Netherlands)

Seidel, F.C.; Kokhanovsky, A.A.; Schaepman, M.E.

2010-01-01

Radiative transfer models (RTMs) are of utmost importance for quantitative remote sensing, especially for compensating atmospheric perturbation. A persistent trade-off exists between approaches that prefer accuracy at the cost of computational complexity, versus those favouring simplicity at the

Radiative transfer in spherical circumstellar dust envelopes. III. Dust envelope models of some well known infrared stars

International Nuclear Information System (INIS)

Apruzese, J.P.

1975-01-01

The radiative transfer techniques described elsewhere by the author have been employed to construct dust envelope models of several well known infrared stars. The resulting calculations indicate that the infrared emissivity of circumstellar grains generally must be higher than that which many calculations of small nonsilicate grains yield. This conclusion is dependent to some degree on the (unknown) size of the stellar envelopes considered, but is quite firm in the case of the spatially resolved envelope of IRC+10216. Further observations of the spatial distribution of the infrared radiation from stellar envelopes will be invaluable in deciphering the properties of the circumstellar grains

Development of dual stream PCRTM-SOLAR for fast and accurate radiative transfer modeling in the cloudy atmosphere with solar radiation

Science.gov (United States)

Yang, Q.; Liu, X.; Wu, W.; Kizer, S.; Baize, R. R.

2016-12-01

Fast and accurate radiative transfer model is the key for satellite data assimilation and observation system simulation experiments for numerical weather prediction and climate study applications. We proposed and developed a dual stream PCRTM-SOLAR model which may simulate radiative transfer in the cloudy atmosphere with solar radiation quickly and accurately. Multi-scattering of multiple layers of clouds/aerosols is included in the model. The root-mean-square errors are usually less than 5x10-4 mW/cm2.sr.cm-1. The computation speed is 3 to 4 orders of magnitude faster than the medium speed correlated-k option MODTRAN5. This model will enable a vast new set of scientific calculations that were previously limited due to the computational expenses of available radiative transfer models.

Heat transfer enhancement of car radiator using aqua based magnesium oxide nanofluids

Directory of Open Access Journals (Sweden)

Ali Hafiz Muhammad

2015-01-01

Full Text Available The focus of this research paper is on the application of water based MgO nanofluids for thermal management of a car radiator. Nanofluids of different volumetric concentrations (i.e. 0.06%, 0.09% and 0.12% were prepared and then experimentally tested for their heat transfer performance in a car radiator. All concentrations showed enhancement in heat transfer compared to the pure base fluid. A peak heat transfer enhancement of 31% was obtained at 0.12 % volumetric concentration of MgO in basefluid. The fluid flow rate was kept in a range of 8-16 liter per minute. Lower flow rates resulted in greater heat transfer rates as compared to heat transfer rates at higher flow rates for the same volumetric concentration. Heat transfer rates were found weakly dependent on the inlet fluid temperature. An increase of 8°C in inlet temperature showed only a 6% increase in heat transfer rate.

Radiatively-suppressed spherical accretion under relativistic radiative transfer

Science.gov (United States)

Fukue, Jun

2018-03-01

We numerically examine radiatively-suppressed relativistic spherical accretion flows on to a central object with mass M under Newtonian gravity and special relativity. We simultaneously solve both the relativistic radiative transfer equation and the relativistic hydrodynamical equations for spherically symmetric flows under the double iteration process in the case of the intermediate optical depth. We find that the accretion flow is suppressed, compared with the freefall case in the nonrelativistic regime. For example, in the case of accretion on to a luminous core with accretion luminosity L*, the freefall velocity v normalized by the speed of light c under the radiative force in the nonrelativistic regime is β (\\hat{r}) = v/c = -√{(1-Γ _*)/(\\hat{r}+1-Γ _*)}, where Γ* (≡ L*/LE, LE being the Eddington luminosity) is the Eddington parameter and \\hat{r} (= r/rS, rS being the Schwarzschild radius) the normalized radius, whereas the infall speed at the central core is ˜0.7β(1), irrespective of the mass-accretion rate. This is due to the relativistic effect; the comoving flux is enhanced by the advective flux. We briefly examine and discuss an isothermal case, where the emission takes place in the entire space.

A difference quotient-numerical integration method for solving radiative transfer problems

International Nuclear Information System (INIS)

Ding Peizhu

1992-01-01

A difference quotient-numerical integration method is adopted to solve radiative transfer problems in an anisotropic scattering slab medium. By using the method, the radiative transfer problem is separated into a system of linear algebraic equations and the coefficient matrix of the system is a band matrix, so the method is very simple to evaluate on computer and to deduce formulae and easy to master for experimentalists. An example is evaluated and it is shown that the method is precise

PN solutions of radiative heat transfer in a slab with reflective boundaries

International Nuclear Information System (INIS)

Atalay, M.A.

2006-01-01

The spherical harmonics method is used to obtain solution for the radiative heat transfer equation for a slab with reflective boundaries. An absorbing, emitting, non-isothermal, gray medium is considered with linearly anisotropic scattering. Under the condition of the thermal equilibrium, the slab boundaries are subjected to specular and diffuse reflection. The analytical form of solutions is obtained for both conservative and non-conservative cases. The accuracy of the method was verified by benchmark comparisons against the solutions of an earlier work performed by the normal-mode expansion technique. The present predictions of heat flux were found to be in good agreement with the benchmark data. a

Homogenization of some radiative heat transfer models: application to gas-cooled reactor cores

International Nuclear Information System (INIS)

El Ganaoui, K.

2006-09-01

In the context of homogenization theory we treat some heat transfer problems involving unusual (according to the homogenization) boundary conditions. These problems are defined in a solid periodic perforated domain where two scales (macroscopic and microscopic) are to be taken into account and describe heat transfer by conduction in the solid and by radiation on the wall of each hole. Two kinds of radiation are considered: radiation in an infinite medium (non-linear problem) and radiation in cavity with grey-diffuse walls (non-linear and non-local problem). The derived homogenized models are conduction problems with an effective conductivity which depend on the considered radiation. Thus we introduce a framework (homogenization and validation) based on mathematical justification using the two-scale convergence method and numerical validation by simulations using the computer code CAST3M. This study, performed for gas cooled reactors cores, can be extended to other perforated domains involving the considered heat transfer phenomena. (author)

Numerical simulations of a coupled radiative?conductive heat transfer model using a modified Monte Carlo method

KAUST Repository

Kovtanyuk, Andrey E.; Botkin, Nikolai D.; Hoffmann, Karl-Heinz

2012-01-01

Radiative-conductive heat transfer in a medium bounded by two reflecting and radiating plane surfaces is considered. This process is described by a nonlinear system of two differential equations: an equation of the radiative heat transfer

Enhancement of heat transfer from a continuously moving porous fin exposed in convective–radiative environment

International Nuclear Information System (INIS)

Bhanja, Dipankar; Kundu, Balaram; Aziz, Abdul

2014-01-01

Highlights: • Analytical model for thermal analysis of moving porous fins. • Heat transfer from the fin surface due to convection and radiation. • For practical design aspects, optimization analysis was carried out. • Comparative study was made between the solid and porous moving fins. • Porous moving fin has more heat transfer ability than the stationary fin. - Abstract: In the present article, an exercise has been devoted to establish an analytical model for the determination of temperature distribution, fin efficiency and optimum design parameters of a porous moving fin which is losing heat by simultaneous convection and radiation to its surroundings. For the adaptation of this consideration, the governing equation becomes highly nonlinear. An analytical technique called Adomian decomposition method (ADM) is proposed for the solution methodology. The accuracy of the analytic solution is validated by using a numeric scheme called finite difference method. The results indicate that the numerical data and analytical approach are in agreement with each other. As the present study is an analytic, it is extended to the analysis for determination of optimum dimensions of said fin by satisfying either the maximization of rate of heat transfer for a given fin volume or by the minimization of fin volume for a desired heat transfer rate. The study is further extended to the porous fin in stationary condition and it is found that porous fin in moving condition transfers more heat than stationary condition. Investigation has also been made on solid moving fin to compare the outcomes of these parameters

Computing Radiative Transfer in a 3D Medium

Science.gov (United States)

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.

Radiative Transfer Modeling in Proto-planetary Disks

Science.gov (United States)

Kasper, David; Jang-Condell, Hannah; Kloster, Dylan

2016-01-01

Young Stellar Objects (YSOs) are rich astronomical research environments. Planets form in circumstellar disks of gas and dust around YSOs. With ever increasing capabilities of the observational instruments designed to look at these proto-planetary disks, most notably GPI, SPHERE, and ALMA, more accurate interfaces must be made to connect modeling of the disks with observation. PaRTY (Parallel Radiative Transfer in YSOs) is a code developed previously to model the observable density and temperature structure of such a disk by self-consistently calculating the structure of the disk based on radiative transfer physics. We present upgrades we are implementing to the PaRTY code to improve its accuracy and flexibility. These upgrades include: creating a two-sided disk model, implementing a spherical coordinate system, and implementing wavelength-dependent opacities. These upgrades will address problems in the PaRTY code of infinite optical thickness, calculation under/over-resolution, and wavelength-independent photon penetration depths, respectively. The upgraded code will be used to better model disk perturbations resulting from planet formation.

ANALYTICAL MODELS OF EXOPLANETARY ATMOSPHERES. II. RADIATIVE TRANSFER VIA THE TWO-STREAM APPROXIMATION

Energy Technology Data Exchange (ETDEWEB)

Heng, Kevin; Mendonça, João M.; Lee, Jae-Min, E-mail: kevin.heng@csh.unibe.ch, E-mail: joao.mendonca@csh.unibe.ch, E-mail: lee@physik.uzh.ch [University of Bern, Center for Space and Habitability, Sidlerstrasse 5, CH-3012 Bern (Switzerland)

2014-11-01

We present a comprehensive analytical study of radiative transfer using the method of moments and include the effects of non-isotropic scattering in the coherent limit. Within this unified formalism, we derive the governing equations and solutions describing two-stream radiative transfer (which approximates the passage of radiation as a pair of outgoing and incoming fluxes), flux-limited diffusion (which describes radiative transfer in the deep interior), and solutions for the temperature-pressure profiles. Generally, the problem is mathematically underdetermined unless a set of closures (Eddington coefficients) is specified. We demonstrate that the hemispheric (or hemi-isotropic) closure naturally derives from the radiative transfer equation if energy conservation is obeyed, while the Eddington closure produces spurious enhancements of both reflected light and thermal emission. We concoct recipes for implementing two-stream radiative transfer in stand-alone numerical calculations and general circulation models. We use our two-stream solutions to construct toy models of the runaway greenhouse effect. We present a new solution for temperature-pressure profiles with a non-constant optical opacity and elucidate the effects of non-isotropic scattering in the optical and infrared. We derive generalized expressions for the spherical and Bond albedos and the photon deposition depth. We demonstrate that the value of the optical depth corresponding to the photosphere is not always 2/3 (Milne's solution) and depends on a combination of stellar irradiation, internal heat, and the properties of scattering in both the optical and infrared. Finally, we derive generalized expressions for the total, net, outgoing, and incoming fluxes in the convective regime.

Electron beam instrumentation techniques using coherent radiation

International Nuclear Information System (INIS)

Wang, D.X.

1997-01-01

Much progress has been made on coherent radiation research since coherent synchrotron radiation was first observed in 1989. The use of coherent radiation as a bunch length diagnostic tool has been studied by several groups. In this paper, brief introductions to coherent radiation and far-infrared measurement are given, the progress and status of their beam diagnostic application are reviewed, different techniques are described, and their advantages and limitations are discussed

Mathematical models of the theory of the radiative transfer

International Nuclear Information System (INIS)

Lin, Ch.

2007-06-01

We are interested in various different models arising in radiative transfer, which describe the interactions between the medium and the photons. The radiation is described in terms of energy and energy flux in the macroscopic view, the material being described by the Euler equations (radiative hydrodynamic model). In another way, the radiation can be seen as a collection of photons, in the microscopic view point; the photons can be absorbed or emitted by the material. The absorption and the emission of photons depend on the internal excitation and ionization state of the material. We begin with the local existence (in time) of smooth solutions to a system coupling the Euler equations and the transfer equation. This system describes the exchange of energy and moment between the radiation and the material. Next, we give an asymptotic discussion for this model in the NON-LTE regime and get a simple system: coupling the Euler equations with an elliptic equation. We show the existence of (smooth) shock profiles to this system and the regularity of the shock profile as a function of the strength of the shock. Then we study the asymptotic stability of the shock profile. Finally, we study a system describing the radiation and the internal state of the material, in the microscopic view point. We prove the existence of the solution to this system and study the convergence towards the statistical equilibrium. The theoretical results are illustrated by numerical simulations. (author)

Radiative transfer model for heterogeneous 3-D scenes

Science.gov (United States)

Kimes, D. S.; Kirchner, J. A.

1982-01-01

A general mathematical framework for simulating processes in heterogeneous 3-D scenes is presented. Specifically, a model was designed and coded for application to radiative transfers in vegetative scenes. The model is unique in that it predicts (1) the directional spectral reflectance factors as a function of the sensor's azimuth and zenith angles and the sensor's position above the canopy, (2) the spectral absorption as a function of location within the scene, and (3) the directional spectral radiance as a function of the sensor's location within the scene. The model was shown to follow known physical principles of radiative transfer. Initial verification of the model as applied to a soybean row crop showed that the simulated directional reflectance data corresponded relatively well in gross trends to the measured data. However, the model can be greatly improved by incorporating more sophisticated and realistic anisotropic scattering algorithms

General relativistic radiative transfer code in rotating black hole space-time: ARTIST

Science.gov (United States)

Takahashi, Rohta; Umemura, Masayuki

2017-02-01

We present a general relativistic radiative transfer code, ARTIST (Authentic Radiative Transfer In Space-Time), that is a perfectly causal scheme to pursue the propagation of radiation with absorption and scattering around a Kerr black hole. The code explicitly solves the invariant radiation intensity along null geodesics in the Kerr-Schild coordinates, and therefore properly includes light bending, Doppler boosting, frame dragging, and gravitational redshifts. The notable aspect of ARTIST is that it conserves the radiative energy with high accuracy, and is not subject to the numerical diffusion, since the transfer is solved on long characteristics along null geodesics. We first solve the wavefront propagation around a Kerr black hole that was originally explored by Hanni. This demonstrates repeated wavefront collisions, light bending, and causal propagation of radiation with the speed of light. We show that the decay rate of the total energy of wavefronts near a black hole is determined solely by the black hole spin in late phases, in agreement with analytic expectations. As a result, the ARTIST turns out to correctly solve the general relativistic radiation fields until late phases as t ˜ 90 M. We also explore the effects of absorption and scattering, and apply this code for a photon wall problem and an orbiting hotspot problem. All the simulations in this study are performed in the equatorial plane around a Kerr black hole. The ARTIST is the first step to realize the general relativistic radiation hydrodynamics.

Radiative transfer modeling through terrestrial atmosphere and ocean accounting for inelastic processes: Software package SCIATRAN

International Nuclear Information System (INIS)

Rozanov, V.V.; Dinter, T.; Rozanov, A.V.; Wolanin, A.; Bracher, A.; Burrows, J.P.

2017-01-01

SCIATRAN is a comprehensive software package which is designed to model radiative transfer processes in the terrestrial atmosphere and ocean in the spectral range from the ultraviolet to the thermal infrared (0.18–40 μm). It accounts for multiple scattering processes, polarization, thermal emission and ocean–atmosphere coupling. The main goal of this paper is to present a recently developed version of SCIATRAN which takes into account accurately inelastic radiative processes in both the atmosphere and the ocean. In the scalar version of the coupled ocean–atmosphere radiative transfer solver presented by Rozanov et al. we have implemented the simulation of the rotational Raman scattering, vibrational Raman scattering, chlorophyll and colored dissolved organic matter fluorescence. In this paper we discuss and explain the numerical methods used in SCIATRAN to solve the scalar radiative transfer equation including trans-spectral processes, and demonstrate how some selected radiative transfer problems are solved using the SCIATRAN package. In addition we present selected comparisons of SCIATRAN simulations with those published benchmark results, independent radiative transfer models, and various measurements from satellite, ground-based, and ship-borne instruments. The extended SCIATRAN software package along with a detailed User's Guide is made available for scientists and students, who are undertaking their own research typically at universities, via the web page of the Institute of Environmental Physics (IUP), University of Bremen: (http://www.iup.physik.uni-bremen.de). - Highlights: • A new version of the software package SCIATRAN is presented. • Inelastic scattering in water and atmosphere is implemented in SCIATRAN. • Raman scattering and fluorescence can be included in radiative transfer calculations. • Comparisons to other radiative transfer models show excellent agreement. • Comparisons to observations show consistent results.

Radiative Transfer Through Discs of Cataclysmic Variables

Czech Academy of Sciences Publication Activity Database

Korčáková, Daniela; Nagel, T.; Werner, K.; Suleimanov, V.; Votruba, Viktor

2010-01-01

Roč. 1273, - (2010), s. 350-353 ISSN 1551-7616. [European White Dwarf Workshop /17./. Tübingen, 16.08.2010-20.08.2010] R&D Projects: GA ČR GP205/09/P476 Institutional research plan: CEZ:AV0Z10030501 Keywords : radiative transfer * Doppler effect, * accretion disks Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

Discrete-ordinates finite-element method for atmospheric radiative transfer and remote sensing

International Nuclear Information System (INIS)

Gerstl, S.A.W.; Zardecki, A.

1985-01-01

Advantages and disadvantages of modern discrete-ordinates finite-element methods for the solution of radiative transfer problems in meteorology, climatology, and remote sensing applications are evaluated. After the common basis of the formulation of radiative transfer problems in the fields of neutron transport and atmospheric optics is established, the essential features of the discrete-ordinates finite-element method are described including the limitations of the method and their remedies. Numerical results are presented for 1-D and 2-D atmospheric radiative transfer problems where integral as well as angular dependent quantities are compared with published results from other calculations and with measured data. These comparisons provide a verification of the discrete-ordinates results for a wide spectrum of cases with varying degrees of absorption, scattering, and anisotropic phase functions. Accuracy and computational speed are also discussed. Since practically all discrete-ordinates codes offer a builtin adjoint capability, the general concept of the adjoint method is described and illustrated by sample problems. Our general conclusion is that the strengths of the discrete-ordinates finite-element method outweight its weaknesses. We demonstrate that existing general-purpose discrete-ordinates codes can provide a powerful tool to analyze radiative transfer problems through the atmosphere, especially when 2-D geometries must be considered

Radiative transfer in silylidene molecule

Directory of Open Access Journals (Sweden)

Sharma M.

2014-01-01

Full Text Available In order to search for silylidene (H2CSi in the interstellar medium, Izuha et al. (1996 recorded microwave spectrum of H2CSi in laboratory and made an unsuccessful attempt of its identification in IRC +10216, Ori KL, Sgr B2, through its 717-616 transition at 222.055 GHz. For finding out if there are other transitions of H2CSi which may help in its identification in the interstellar medium, we have considered 25 rotational levels of ortho-H2CSi connected by collisional transitions and 35 radiative transitions, and solved radiative transfer problem using the LVG approximation. We have found that the brightness temperatures of 919-818, 918-817, 101,10-919, 1019-918, 111,11-101,10, 111,10-1019 and 121,12-111,11 transition are larger than that of 717-616 transition. Thus, these transitions may help in detection of H2CSi in the interstellar medium.

The use of recombinant DNA techniques to study radiation-induced damage, repair and genetic change in mammalian cells

International Nuclear Information System (INIS)

Thacker, J.

1986-01-01

A brief introduction is given to appropriate elements of recombinant DNA techniques and applications to problems in radiobiology are reviewed with illustrative detail. Examples are included of studies with both 254 nm ultraviolet light and ionizing radiation and the review progresses from the molecular analysis of DNA damage in vitro through to the nature of consequent cellular responses. The review is dealt with under the following headings: Molecular distribution of DNA damage, The use of DNA-mediated gene transfer to assess damage and repair, The DNA double strand break: use of restriction endonucleases to model radiation damage, Identification and cloning of DNA repair genes, Analysis of radiation-induced genetic change. (UK)

Towards convective heat transfer enhancement: surface modification, characterization and measurement techniques

NARCIS (Netherlands)

Taha, T.J.; Thakur, D.B.; van der Meer, Theodorus H.

2012-01-01

In this work, heat transfer surface modification and heat transfer measurement technique is developed. Heat transfer investigation was aimed to study the effect of carbon nano fibers (extremely high thermal conductive material) on the enhancement level in heat transfer. Synthesis of these carbon

Light scattering reviews 9 light scattering and radiative transfer

CERN Document Server

Kokhanovsky, Alexander A

2014-01-01

This book details modern methods of the radiative transfer theory. It presents recent advances in light scattering (measurements and theory) and highlights the newest developments in remote sensing of aerosol and cloud properties.

Ultra thin metallic coatings to control near field radiative heat transfer

Science.gov (United States)

Esquivel-Sirvent, R.

2016-09-01

We present a theoretical calculation of the changes in the near field radiative heat transfer between two surfaces due to the presence of ultra thin metallic coatings on semiconductors. Depending on the substrates, the radiative heat transfer is modulated by the thickness of the ultra thin film. In particular we consider gold thin films with thicknesses varying from 4 to 20 nm. The ultra-thin film has an insulator-conductor transition close to a critical thickness of dc = 6.4 nm and there is an increase in the near field spectral heat transfer just before the percolation transition. Depending on the substrates (Si or SiC) and the thickness of the metallic coatings we show how the near field heat transfer can be increased or decreased as a function of the metallic coating thickness. The calculations are based on available experimental data for the optical properties of ultrathin coatings.

PRECONDITIONED BI-CONJUGATE GRADIENT METHOD FOR RADIATIVE TRANSFER IN SPHERICAL MEDIA

International Nuclear Information System (INIS)

Anusha, L. S.; Nagendra, K. N.; Paletou, F.; Leger, L.

2009-01-01

A robust numerical method called the Preconditioned Bi-Conjugate Gradient (Pre-BiCG) method is proposed for the solution of the radiative transfer equation in spherical geometry. A variant of this method called Stabilized Preconditioned Bi-Conjugate Gradient (Pre-BiCG-STAB) is also presented. These are iterative methods based on the construction of a set of bi-orthogonal vectors. The application of the Pre-BiCG method in some benchmark tests shows that the method is quite versatile, and can handle difficult problems that may arise in astrophysical radiative transfer theory.

Martian Radiative Transfer Modeling Using the Optimal Spectral Sampling Method

Science.gov (United States)

Eluszkiewicz, J.; Cady-Pereira, K.; Uymin, G.; Moncet, J.-L.

2005-01-01

The large volume of existing and planned infrared observations of Mars have prompted the development of a new martian radiative transfer model that could be used in the retrievals of atmospheric and surface properties. The model is based on the Optimal Spectral Sampling (OSS) method [1]. The method is a fast and accurate monochromatic technique applicable to a wide range of remote sensing platforms (from microwave to UV) and was originally developed for the real-time processing of infrared and microwave data acquired by instruments aboard the satellites forming part of the next-generation global weather satellite system NPOESS (National Polarorbiting Operational Satellite System) [2]. As part of our on-going research related to the radiative properties of the martian polar caps, we have begun the development of a martian OSS model with the goal of using it to perform self-consistent atmospheric corrections necessary to retrieve caps emissivity from the Thermal Emission Spectrometer (TES) spectra. While the caps will provide the initial focus area for applying the new model, it is hoped that the model will be of interest to the wider Mars remote sensing community.

Vector Green's function algorithm for radiative transfer in plane-parallel atmosphere

International Nuclear Information System (INIS)

Qin Yi; Box, Michael A.

2006-01-01

Green's function is a widely used approach for boundary value problems. In problems related to radiative transfer, Green's function has been found to be useful in land, ocean and atmosphere remote sensing. It is also a key element in higher order perturbation theory. This paper presents an explicit expression of the Green's function, in terms of the source and radiation field variables, for a plane-parallel atmosphere with either vacuum boundaries or a reflecting (BRDF) surface. Full polarization state is considered but the algorithm has been developed in such way that it can be easily reduced to solve scalar radiative transfer problems, which makes it possible to implement a single set of code for computing both the scalar and the vector Green's function

Relations between radiation risks and radiation protection measuring techniques

International Nuclear Information System (INIS)

Herrmann, K.; Kraus, W.

Relations between radiation risks and radiation protection measuring techniques are considered as components of the radiation risk. The influence of the exposure risk on type and extent of radiation protection measurements is discussed with regard to different measuring tasks. Based upon measuring results concerning the frequency of certain external and internal occupational exposures in the GDR, it has been shown that only a small fraction of the monitored persons are subjected to a high exposure risk. As a consequence the following recommendations are presented: occupationally exposed persons with small exposure risk should be monitored using only a long-term desimeter (for instance a thermoluminescence desimeter). In the case of internal exposure, the surface and air contamination levels should be controlled so strictly that routine measurements of internal contamination need not be performed

Spectral element method for vector radiative transfer equation

International Nuclear Information System (INIS)

Zhao, J.M.; Liu, L.H.; Hsu, P.-F.; Tan, J.Y.

2010-01-01

A spectral element method (SEM) is developed to solve polarized radiative transfer in multidimensional participating medium. The angular discretization is based on the discrete-ordinates approach, and the spatial discretization is conducted by spectral element approach. Chebyshev polynomial is used to build basis function on each element. Four various test problems are taken as examples to verify the performance of the SEM. The effectiveness of the SEM is demonstrated. The h and the p convergence characteristics of the SEM are studied. The convergence rate of p-refinement follows the exponential decay trend and is superior to that of h-refinement. The accuracy and efficiency of the higher order approximation in the SEM is well demonstrated for the solution of the VRTE. The predicted angular distribution of brightness temperature and Stokes vector by the SEM agree very well with the benchmark solutions in references. Numerical results show that the SEM is accurate, flexible and effective to solve multidimensional polarized radiative transfer problems.

System for selection of radiation source transfer trucks

International Nuclear Information System (INIS)

Tanimoto, Yoshinori; Ito, Kojiro.

1970-01-01

A device for selection of trucks each of which load and transfer a radiation source to an irradiation room above a water pool is installed at the end of a pair of rails fixed to the bottom of the pool. This device is equipped with a number of laterally shiftable rail pairs which may be brought into successive alignment with the fixed rails and is adapted to receive, carry and fix a truck on each rail pair. If one of said trucks is selected for irradiation in a desired irradiation room, the rail pair carrying this truck is shifted to align and couple with the fixed rail pair whereupon the truck is driven and transferred to a position on the fixed rails below the desired room and elevated thereinto. Accordingly, a plurality of trucks can optionally be shunted on a line of fixed rails without unloading the respective radiation sources. (Ohno, Y.)

Fuel Transfer Cask; Procedure Option and Radiation Protection during Transferring the Spent Fuel

International Nuclear Information System (INIS)

Muhammad Khairul Ariff Mustafa; Nurhayati Ramli; Ahmad Nabil Abdul Rahim; Mohd Fazli Zakaria

2011-01-01

Reactor TRIGA PUSPATI (RTP) has been operating almost 30 years. Many components are ageing. Nuclear Malaysia has taken an initiative to manage this ageing problem to prolong the life of the reactor. Hence, reactor upgrading project already commence started with the reactor console. To upgrade the core, all the fuel must be taken out from the core. A conceptual design of fuel transfer cask already done. This paper will discuss about the option of safe working procedure for transferring the fuel to the spent fuel pool for temporary. Hence, radiation protection for operator should be considered during the process. (author)

A second order radiative transfer equation and its solution by meshless method with application to strongly inhomogeneous media

Energy Technology Data Exchange (ETDEWEB)

Zhao, J.M., E-mail: jmzhao@hit.edu.cn [School of Energy Science and Engineering, Harbin Institute of Technology, 92 West Dazhi Street, Harbin 150001, People' s Republic of China (China); Tan, J.Y., E-mail: tanjy@hit.edu.cn [School of Auto Engineering, Harbin Institute of Technology at Weihai, 2 West Wenhua Road, Weihai 264209, People' s Republic of China (China); Liu, L.H., E-mail: lhliu@hit.edu.cn [School of Energy Science and Engineering, Harbin Institute of Technology, 92 West Dazhi Street, Harbin 150001, People' s Republic of China (China); School of Auto Engineering, Harbin Institute of Technology at Weihai, 2 West Wenhua Road, Weihai 264209, People' s Republic of China (China)

2013-01-01

A new second order form of radiative transfer equation (named MSORTE) is proposed, which overcomes the singularity problem of a previously proposed second order radiative transfer equation [J.E. Morel, B.T. Adams, T. Noh, J.M. McGhee, T.M. Evans, T.J. Urbatsch, Spatial discretizations for self-adjoint forms of the radiative transfer equations, J. Comput. Phys. 214 (1) (2006) 12-40 (where it was termed SAAI), J.M. Zhao, L.H. Liu, Second order radiative transfer equation and its properties of numerical solution using finite element method, Numer. Heat Transfer B 51 (2007) 391-409] in dealing with inhomogeneous media where some locations have very small/zero extinction coefficient. The MSORTE contains a naturally introduced diffusion (or second order) term which provides better numerical property than the classic first order radiative transfer equation (RTE). The stability and convergence characteristics of the MSORTE discretized by central difference scheme is analyzed theoretically, and the better numerical stability of the second order form radiative transfer equations than the RTE when discretized by the central difference type method is proved. A collocation meshless method is developed based on the MSORTE to solve radiative transfer in inhomogeneous media. Several critical test cases are taken to verify the performance of the presented method. The collocation meshless method based on the MSORTE is demonstrated to be capable of stably and accurately solve radiative transfer in strongly inhomogeneous media, media with void region and even with discontinuous extinction coefficient.

How do laboratory embryo transfer techniques affect IVF outcomes? A review of current literature.

Science.gov (United States)

Sigalos, George; Triantafyllidou, Olga; Vlahos, Nikos

2017-04-01

Over the last few years, many studies have focused on embryo selection methods, whereas little attention has been given to the standardization of the procedure of embryo transfer. In this review, several parameters of the embryo transfer procedure are examined, such as the: (i) culture medium volume and loading technique; (ii) syringe and catheters used for embryo transfer; (iii) viscosity and composition of the embryo transfer medium; (iv) environment of embryo culture; (v) timing of embryo transfer; (vi) and standardization of the embryo transfer techniques. The aim of this manuscript is to review these factors and compare the existing embryo transfer techniques and highlight the need for better embryo transfer standardization.

Use of radiation to transfer alien chromosome segments to wheat

International Nuclear Information System (INIS)

Sears, E.R.

1993-01-01

Ionizing radiation can accomplish the transfer of genetic information from species so distantly related to wheat (Triticum aestivum L. em Thell.) that their chromosomes pair very little, if at all, with those of wheat, even in the absence of the homoeologous-pairing suppressor Ph1. In a successful transfer, the alien segment must almost always replace a homoeologous wheat segment, but radiation induces translocations largely at random; therefore automatic selection in favor of desirable translocations must be provided if the size of the project is to be kept within reasonable limits. Pollen selection will occur if seeds or plants monosomic for both an alien chromosome and one of its wheat homoeologues are irradiated. Making the plants also deficient for Ph1 may increase the number of suitable transfers. High-frequency occurrence of the desired alien character in M2 head-rows from plants grown from irradiated seed can identify favorable transfers with little cytological work. Irradiation of plants shortly before meiosis, using them to pollinate ditelosomics or double ditelosomics for the wheat arm or chromosome concerned, and cytologically examining offspring which have the alien character can not only identify the desirable transfers, but also reveal the lengths of the alien segments involved

Casimir friction and near-field radiative heat transfer in graphene structures

Energy Technology Data Exchange (ETDEWEB)

Volokitin, A.I. [Forschungszentrum Juelich (Germany). Peter Gruenberg Inst.; Samara State Technical Univ. (Russian Federation). Physical Dept.

2017-05-01

The dependence of the Casimir friction force between a graphene sheet and a (amorphous) SiO{sub 2} substrate on the drift velocity of the electrons in the graphene sheet is studied. It is shown that the Casimir friction is strongly enhanced for the drift velocity above the threshold velocity when the friction is determined by the resonant excitation of the surface phonon-polaritons in the SiO{sub 2} substrate and the electron-hole pairs in graphene. The theory agrees well with the experimental data for the current-voltage dependence for unsuspended graphene on the SiO{sub 2} substrate. The theories of the Casimir friction and the near-field radiative energy transfer are used to study the heat generation and dissipation in graphene due to the interaction with phonon-polaritons in the (amorphous) SiO{sub 2} substrate and acoustic phonons in graphene. For suspended graphene, the energy transfer coefficient at nanoscale gap is ∝ three orders of magnitude larger than the radiative heat transfer coefficient of the blackbody radiation limit.

Casimir friction and near-field radiative heat transfer in graphene structures

International Nuclear Information System (INIS)

Volokitin, A.I.; Samara State Technical Univ.

2017-01-01

The dependence of the Casimir friction force between a graphene sheet and a (amorphous) SiO 2 substrate on the drift velocity of the electrons in the graphene sheet is studied. It is shown that the Casimir friction is strongly enhanced for the drift velocity above the threshold velocity when the friction is determined by the resonant excitation of the surface phonon-polaritons in the SiO 2 substrate and the electron-hole pairs in graphene. The theory agrees well with the experimental data for the current-voltage dependence for unsuspended graphene on the SiO 2 substrate. The theories of the Casimir friction and the near-field radiative energy transfer are used to study the heat generation and dissipation in graphene due to the interaction with phonon-polaritons in the (amorphous) SiO 2 substrate and acoustic phonons in graphene. For suspended graphene, the energy transfer coefficient at nanoscale gap is ∝ three orders of magnitude larger than the radiative heat transfer coefficient of the blackbody radiation limit.

Reconstruction of mandibular defects after radiation, using a free, living bone, graft transferred by microvascular anastomoses. An experimental study

International Nuclear Information System (INIS)

Ostrup, L.T.; Fredrickson, J.M.

1975-01-01

The replacement of a mandibular defect by a free, composite rib graft, transferred by microvascular anastomoses of the posterior intercostal vessels to donor vessels in the neck was described previously. We now present data which demonstrate that successful results can be achieved even after radical mandibular radiation. This technique, done in dogs, has obvious implications in the management of oral cancer in man

Modeling Loss-of-Flow Accidents and Their Impact on Radiation Heat Transfer

Directory of Open Access Journals (Sweden)

Jivan Khatry

2017-01-01

Full Text Available Long-term high payload missions necessitate the need for nuclear space propulsion. The National Aeronautics and Space Administration (NASA investigated several reactor designs from 1959 to 1973 in order to develop the Nuclear Engine for Rocket Vehicle Application (NERVA. Study of planned/unplanned transients on nuclear thermal rockets is important due to the need for long-term missions. In this work, a system model based on RELAP5 is developed to simulate loss-of-flow accidents on the Pewee I test reactor. This paper investigates the radiation heat transfer between the fuel elements and the structures around it. In addition, the impact on the core fuel element temperature and average core pressure was also investigated. The following expected results were achieved: (i greater than normal fuel element temperatures, (ii fuel element temperatures exceeding the uranium carbide melting point, and (iii average core pressure less than normal. Results show that the radiation heat transfer rate between fuel elements and cold surfaces increases with decreasing flow rate through the reactor system. However, radiation heat transfer decreases when there is a complete LOFA. When there is a complete LOFA, the peripheral coolant channels of the fuel elements handle most of the radiation heat transfer. A safety system needs to be designed to counteract the decay heat resulting from a post-LOFA reactor scram.

Unsteady MHD radiative flow and heat transfer of a dusty nanofluid over an exponentially stretching surface

Directory of Open Access Journals (Sweden)

N. Sandeep

2016-03-01

Full Text Available We analyzed the unsteady magnetohydrodynamic radiative flow and heat transfer characteristics of a dusty nanofluid over an exponentially permeable stretching surface in presence of volume fraction of dust and nano particles. We considered two types of nanofluids namely Cu-water and CuO-water embedded with conducting dust particles. The governing equations are transformed into nonlinear ordinary differential equations by using similarity transformation and solved numerically using Runge–Kutta based shooting technique. The effects of non-dimensional governing parameters namely magneticfield parameter, mass concentration of dust particles, fluid particle interaction parameter, volume fraction of dust particles, volume fraction of nano particles, unsteadiness parameter, exponential parameter, radiation parameter and suction/injection parameter on velocity profiles for fluid phase, dust phase and temperature profiles are discussed and presented through graphs. Also, friction factor and Nusselt numbers are discussed and presented for two dusty nanofluids separately. Comparisons of the present study were made with existing studies under some special assumptions. The present results have an excellent agreement with existing studies. Results indicated that the enhancement in fluid particle interaction increases the heat transfer rate and depreciates the wall friction. Also, radiation parameter has the tendency to increase the temperature profiles of the dusty nanofluid.

User's Manual: Routines for Radiative Heat Transfer and Thermometry

Science.gov (United States)

Risch, Timothy K.

2016-01-01

Determining the intensity and spectral distribution of radiation emanating from a heated surface has applications in many areas of science and engineering. Areas of research in which the quantification of spectral radiation is used routinely include thermal radiation heat transfer, infrared signature analysis, and radiation thermometry. In the analysis of radiation, it is helpful to be able to predict the radiative intensity and the spectral distribution of the emitted energy. Presented in this report is a set of routines written in Microsoft Visual Basic for Applications (VBA) (Microsoft Corporation, Redmond, Washington) and incorporating functions specific to Microsoft Excel (Microsoft Corporation, Redmond, Washington) that are useful for predicting the radiative behavior of heated surfaces. These routines include functions for calculating quantities of primary importance to engineers and scientists. In addition, the routines also provide the capability to use such information to determine surface temperatures from spectral intensities and for calculating the sensitivity of the surface temperature measurements to unknowns in the input parameters.

Techniques for radiation measurements: Micro-dosimetry and dosimetry

International Nuclear Information System (INIS)

Waker, A. J.

2006-01-01

Experimental Micro-dosimetry is concerned with the determination of radiation quality and how this can be specified in terms of the distribution of energy deposition arising from the interaction of a radiation field with a particular target site. This paper discusses various techniques that have been developed to measure radiation energy deposition over the three orders of magnitude of site-size; nano-meter, micrometer and millimetre, which radiation biology suggests is required to fully account for radiation quality. Inevitably, much of the discussion will concern the use of tissue-equivalent proportional counters and variants of this device, but other technologies that have been studied, or are under development, for their potential in experimental Micro-dosimetry are also covered. Through an examination of some of the quantities used in radiation metrology and dosimetry the natural link with Micro-dosimetric techniques will be shown and the particular benefits of using Micro-dosimetric methods for dosimetry illustrated. (authors)

A facile alternative technique for large-area graphene transfer via sacrificial polymer

Directory of Open Access Journals (Sweden)

Eric Auchter

2017-12-01

Full Text Available A novel method of transferring large-area graphene sheets onto a variety of substrates using Formvar (polyvinyl formal is presented. Due to the ease at which formvar can be dissolved in chloroform this method allows for a consistent, a clean, and a more rapid transfer than other techniques including the PMMA assisted one. This novel transfer method is demonstrated by transferring large-area graphene onto a range of substrates including commercial TEM grids, silicon dioxide and glass. Raman spectroscopy was used to confirm the presence of graphene and characterize the morphological properties of the large-area sheets. SEM and AFM analyses demonstrated the effectiveness of our rapid transfer technique for clean crystalline large-area graphene sheets. The removal of the sacrificial polymer was found to be one to two orders of magnitude faster than PMMA methods. Ultimately this facile transfer technique offers new opportunities for a wide range of applications for large-area graphene through the utilization of a new sacrificial polymer.

Natural element method for radiative heat transfer in a semitransparent medium with irregular geometries

Energy Technology Data Exchange (ETDEWEB)

Zhang, Yong [School of Energy Science and Engineering, Harbin Institute of Technology, 92 West Dazhi Street, Harbin 150001 (China); Yi, Hong-Liang, E-mail: yihongliang@hit.edu.cn [School of Energy Science and Engineering, Harbin Institute of Technology, 92 West Dazhi Street, Harbin 150001 (China); Tan, He-Ping, E-mail: tanheping@hit.edu.cn [School of Energy Science and Engineering, Harbin Institute of Technology, 92 West Dazhi Street, Harbin 150001 (China)

2013-05-15

This paper develops a numerical solution to the radiative heat transfer problem coupled with conduction in an absorbing, emitting and isotropically scattering medium with the irregular geometries using the natural element method (NEM). The walls of the enclosures, having temperature and mixed boundary conditions, are considered to be opaque, diffuse as well as gray. The NEM as a meshless method is a new numerical scheme in the field of computational mechanics. Different from most of other meshless methods such as element-free Galerkin method or those based on radial basis functions, the shape functions used in NEM are constructed by the natural neighbor interpolations, which are strictly interpolant and the essential boundary conditions can be imposed directly. The natural element solutions in dealing with the coupled heat transfer problem for the mixed boundary conditions have been validated by comparison with those from Monte Carlo method (MCM) generated by the authors. For the validation of the NEM solution to radiative heat transfer in the semicircular medium with an inner circle, the results by NEM have been compared with those reported in the literatures. For pure radiative transfer, the upwind scheme is employed to overcome the oscillatory behavior of the solutions in some conditions. The steady state and transient heat transfer problem combined with radiation and conduction in the semicircular enclosure with an inner circle are studied. Effects of various parameters such as the extinction coefficient, the scattering albedo, the conduction–radiation parameter and the boundary emissivity are analyzed on the radiative and conductive heat fluxes and transient temperature distributions.

Modelling radiative heat transfer inside a basin type solar still

International Nuclear Information System (INIS)

Madhlopa, A.

2014-01-01

Radiative heat transfer inside a basin type solar still has been investigated using two models with (model 1) and without (model 2) taking into account optical view factors. The coefficient of radiative heat exchange (h r,w-gc ) between the water and cover surfaces of a practical solar still was computed using the two models. Simulation results show that model 1 yields lower values of h r,w-gc and the root mean square error than model 2. It is therefore concluded that the accuracy of modelling the performance of a basin-type solar still can be improved by incorporating view factors. - Highlights: • Radiative heat transfer in a basin type solar still has been investigated. • Two models with and without view factors were used. • The model with view factors exhibits a lower magnitude of root mean square error. • View factors affect the accuracy of modelling the performance of the solar still

A hybrid transport-diffusion method for Monte Carlo radiative-transfer simulations

International Nuclear Information System (INIS)

Densmore, Jeffery D.; Urbatsch, Todd J.; Evans, Thomas M.; Buksas, Michael W.

2007-01-01

Discrete Diffusion Monte Carlo (DDMC) is a technique for increasing the efficiency of Monte Carlo particle-transport simulations in diffusive media. If standard Monte Carlo is used in such media, particle histories will consist of many small steps, resulting in a computationally expensive calculation. In DDMC, particles take discrete steps between spatial cells according to a discretized diffusion equation. Each discrete step replaces many small Monte Carlo steps, thus increasing the efficiency of the simulation. In addition, given that DDMC is based on a diffusion equation, it should produce accurate solutions if used judiciously. In practice, DDMC is combined with standard Monte Carlo to form a hybrid transport-diffusion method that can accurately simulate problems with both diffusive and non-diffusive regions. In this paper, we extend previously developed DDMC techniques in several ways that improve the accuracy and utility of DDMC for nonlinear, time-dependent, radiative-transfer calculations. The use of DDMC in these types of problems is advantageous since, due to the underlying linearizations, optically thick regions appear to be diffusive. First, we employ a diffusion equation that is discretized in space but is continuous in time. Not only is this methodology theoretically more accurate than temporally discretized DDMC techniques, but it also has the benefit that a particle's time is always known. Thus, there is no ambiguity regarding what time to assign a particle that leaves an optically thick region (where DDMC is used) and begins transporting by standard Monte Carlo in an optically thin region. Also, we treat the interface between optically thick and optically thin regions with an improved method, based on the asymptotic diffusion-limit boundary condition, that can produce accurate results regardless of the angular distribution of the incident Monte Carlo particles. Finally, we develop a technique for estimating radiation momentum deposition during the

A RADIATION TRANSFER SOLVER FOR ATHENA USING SHORT CHARACTERISTICS

International Nuclear Information System (INIS)

Davis, Shane W.; Stone, James M.; Jiang Yanfei

2012-01-01

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.

Light scattering by multiple spheres: comparison between Maxwell theory and radiative-transfer-theory calculations.

Science.gov (United States)

Voit, Florian; Schäfer, Jan; Kienle, Alwin

2009-09-01

We present a methodology to compare results of classical radiative transfer theory against exact solutions of Maxwell theory for a high number of spheres. We calculated light propagation in a cubic scattering region (20 x 20 x 20 microm(3)) consisting of different concentrations of polystyrene spheres in water (diameter 2 microm) by an analytical solution of Maxwell theory and by a numerical solution of radiative transfer theory. The relative deviation of differential as well as total scattering cross sections obtained by both approaches was evaluated for each sphere concentration. For the considered case, we found that deviations due to radiative transfer theory remain small, even for concentrations up to ca. 20 vol. %.

Radiative heat transfer in 2D Dirac materials

International Nuclear Information System (INIS)

Rodriguez-López, Pablo; Tse, Wang-Kong; Dalvit, Diego A R

2015-01-01

We compute the radiative heat transfer between two sheets of 2D Dirac materials, including topological Chern insulators and graphene, within the framework of the local approximation for the optical response of these materials. In this approximation, which neglects spatial dispersion, we derive both numerically and analytically the short-distance asymptotic of the near-field heat transfer in these systems, and show that it scales as the inverse of the distance between the two sheets. Finally, we discuss the limitations to the validity of this scaling law imposed by spatial dispersion in 2D Dirac materials. (paper)

Stochastic radiative transfer model for mixture of discontinuous vegetation canopies

International Nuclear Information System (INIS)

Shabanov, Nikolay V.; Huang, D.; Knjazikhin, Y.; Dickinson, R.E.; Myneni, Ranga B.

2007-01-01

Modeling of the radiation regime of a mixture of vegetation species is a fundamental problem of the Earth's land remote sensing and climate applications. The major existing approaches, including the linear mixture model and the turbid medium (TM) mixture radiative transfer model, provide only an approximate solution to this problem. In this study, we developed the stochastic mixture radiative transfer (SMRT) model, a mathematically exact tool to evaluate radiation regime in a natural canopy with spatially varying optical properties, that is, canopy, which exhibits a structured mixture of vegetation species and gaps. The model solves for the radiation quantities, direct input to the remote sensing/climate applications: mean radiation fluxes over whole mixture and over individual species. The canopy structure is parameterized in the SMRT model in terms of two stochastic moments: the probability of finding species and the conditional pair-correlation of species. The second moment is responsible for the 3D radiation effects, namely, radiation streaming through gaps without interaction with vegetation and variation of the radiation fluxes between different species. We performed analytical and numerical analysis of the radiation effects, simulated with the SMRT model for the three cases of canopy structure: (a) non-ordered mixture of species and gaps (TM); (b) ordered mixture of species without gaps; and (c) ordered mixture of species with gaps. The analysis indicates that the variation of radiation fluxes between different species is proportional to the variation of species optical properties (leaf albedo, density of foliage, etc.) Gaps introduce significant disturbance to the radiation regime in the canopy as their optical properties constitute major contrast to those of any vegetation species. The SMRT model resolves deficiencies of the major existing mixture models: ignorance of species radiation coupling via multiple scattering of photons (the linear mixture model

Entropy flow and generation in radiative transfer between surfaces

Energy Technology Data Exchange (ETDEWEB)

Zhang, Z.M.; Basu, S. [Georgia Institute of Technolgy, Atlanta, GA (United States). George W. Woodruff School of Mechanical Engineering

2007-02-15

Entropy of radiation has been used to derive the laws of blackbody radiation and determine the maximum efficiency of solar energy conversion. Along with the advancement in thermophotovoltaic technologies and nanoscale heat radiation, there is an urgent need to determine the entropy flow and generation in radiative transfer between nonideal surfaces when multiple reflections are significant. This paper investigates entropy flow and generation when incoherent multiple reflections are included, without considering the effects of interference and photon tunneling. The concept of partial equilibrium is applied to interpret the monochromatic radiation temperature of thermal radiation, T{sub l}(l,{omega}), which is dependent on both wavelength l and direction {omega}. The entropy flux and generation can thus be evaluated for nonideal surfaces. It is shown that several approximate expressions found in the literature can result in significant errors in entropy analysis even for diffuse-gray surfaces. The present study advances the thermodynamics of nonequilibrium thermal radiation and will have a significant impact on the future development of thermophotovoltaic and other radiative energy conversion devices. (author)

Radio galaxies radiation transfer, dynamics, stability and evolution of a synchrotron plasmon

CERN Document Server

Pacholczyk, A G

1977-01-01

Radio Galaxies: Radiation Transfer, Dynamics, Stability and Evolution of a Synchrotron Plasmon deals with the physics of a region in space containing magnetic field and thermal and relativistic particles (a plasmon). The synchrotron emission and absorption of this region are discussed, along with the properties of its spectrum; its linear and circular polarization; transfer of radiation through such a region; its dynamics and expansion; and interaction with external medium.Comprised of eight chapters, this volume explores the stability, turbulence, and acceleration of particles in a synchrotro

Machine learning based cloud mask algorithm driven by radiative transfer modeling

Science.gov (United States)

Chen, N.; Li, W.; Tanikawa, T.; Hori, M.; Shimada, R.; Stamnes, K. H.

2017-12-01

Cloud detection is a critically important first step required to derive many satellite data products. Traditional threshold based cloud mask algorithms require a complicated design process and fine tuning for each sensor, and have difficulty over snow/ice covered areas. With the advance of computational power and machine learning techniques, we have developed a new algorithm based on a neural network classifier driven by extensive radiative transfer modeling. Statistical validation results obtained by using collocated CALIOP and MODIS data show that its performance is consistent over different ecosystems and significantly better than the MODIS Cloud Mask (MOD35 C6) during the winter seasons over mid-latitude snow covered areas. Simulations using a reduced number of satellite channels also show satisfactory results, indicating its flexibility to be configured for different sensors.

A new approach to radiative transfer theory using Jones's vectors. I

International Nuclear Information System (INIS)

Fymat, A.L.; Vasudevan, R.

1975-01-01

Radiative transfer of partially polarized radiation in an anisotropically scattering, inhomogeneous atmosphere containing arbitrary polydispersion of particles is described using Jones's amplitude vectors and matrices. This novel approach exploits the close analogy between the quantum mechanical states of spin 1/2 systems and the polarization states of electromagnetic radiation described by Jones's vector, and draws on the methodology of such spin 1/2 systems. The complete equivalence between the transport equation for Jones's vectors and the classical radiative transfer equation for Stokes's intensity vectors is demonstrated in two independent ways after deriving the transport equations for the polarization coherency matrices and for the quaternions corresponding to the Jones's vectors. A compact operator formulation of the theory is provided, and used to derive the necessary equations for both a local and a global description of the transport of Jones's vectors. Lastly, the integro-differential equations for the amplitude reflection and transmission matrices are derived, and related to the usual corresponding equations. The present formulation is the most succinct and the most convenient one for both theoretical and experimental studies. It yields a simpler analysis than the classical formulation since it reduces by a factor of two the dimensionality of transfer problems. It preserves information on phases, and thus can be used directly across the entire electromagnetic spectrum without any further conversion into intensities. (Auth.)

Fractional integration and radiative transfer in a multifractal atmosphere

Energy Technology Data Exchange (ETDEWEB)

Naud, C.; Schertzer, D. [Universite Pierre et Marie Curie, Paris (France); Lovejoy, S. [McGill Univ., Montreal (Canada)

1996-04-01

Recently, Cess et al. (1995) and Ramathan et al. (1995) cited observations which exhibit an anomalous absorption of cloudy skies in comparison with the value predicted by usual models and which thus introduce large uncertainties for climatic change assessments. These observation raise questions concerning the way general circulation models have been tuned for decades, relying on classical methods, of both radiative transfer and dynamical modeling. The observations also tend to demonstrate that homogeneous models are simply not relevant in relating the highly variable properties of clouds and radiation fields. However smoothed, the intensity of cloud`s multi-scattered radiation fields reflect this extreme variability.

Polarized Radiative Transfer in Fluctuating Stochastic Media

International Nuclear Information System (INIS)

Sallah, M.; Degheidy, A.R.; Selim, M.M.

2009-01-01

The problem of polarized radiative transfer in a planar cluttered atmospheric medium (like cloudy atmosphere) is proposed. The solution is presented for an arbitrary absorption and scattering cross sections. The extinction function of the medium is assumed to be a continuous random function of position, with fluctuations about the mean taken as Gaussian distributed. The joint probability distribution function of these Gaussian random variables is used to calculate the ensemble-averaged quantities, such as reflectivity, radiative energy and radiative flux, for an arbitrary correlation function. A modified Gaussian probability distribution function is also used to average the solution in order to exclude the probable negative values of the optical variable. The problem is considered in half space medium which has specular reflecting boundary exposed to unit external incident flux. Numerical results of the average reflectivity, average radiant energy and average net flux are obtained for both Gaussian and modified Gaussian probability density functions at different degrees of polarization

Direct Collapse to Supermassive Black Hole Seeds with Radiation Transfer: Cosmological Halos

Science.gov (United States)

Ardaneh, Kazem; Luo, Yang; Shlosman, Isaac; Nagamine, Kentaro; Wise, John H.; Begelman, Mitchell C.

2018-06-01

We have modeled direct collapse of a primordial gas within dark matter halos in the presence of radiative transfer, in high-resolution zoom-in simulations in a cosmological framework, down to the formation of the photosphere and the central object. Radiative transfer has been implemented in the flux-limited diffusion (FLD) approximation. Adiabatic models were run for comparison. We find that (a) the FLD flow forms an irregular central structure and does not exhibit fragmentation, contrary to adiabatic flow which forms a thick disk, driving a pair of spiral shocks, subject to Kelvin-Helmholtz shear instability forming fragments; (b) the growing central core in the FLD flow quickly reaches ˜10 M⊙ and a highly variable luminosity of 1038 - 1039 erg s-1, comparable to the Eddington luminosity. It experiences massive recurrent outflows driven by radiation force and thermal pressure gradients, which mix with the accretion flow and transfer the angular momentum outwards; and (c) the interplay between these processes and a massive accretion, results in photosphere at ˜10 AU. We conclude that in the FLD model (1) the central object exhibits dynamically insignificant rotation and slower than adiabatic temperature rise with density; (2) does not experience fragmentation leading to star formation, thus promoting the fast track formation of a supermassive black hole (SMBH) seed; (3) inclusion of radiation force leads to outflows, resulting in the mass accumulation within the central 10-3 pc, which is ˜100 times larger than characteristic scale of star formation. The inclusion of radiative transfer reveals complex early stages of formation and growth of the central structure in the direct collapse scenario of SMBH seed formation.

Process techniques of charge transfer time reduction for high speed CMOS image sensors

International Nuclear Information System (INIS)

Cao Zhongxiang; Li Quanliang; Han Ye; Qin Qi; Feng Peng; Liu Liyuan; Wu Nanjian

2014-01-01

This paper proposes pixel process techniques to reduce the charge transfer time in high speed CMOS image sensors. These techniques increase the lateral conductivity of the photo-generated carriers in a pinned photodiode (PPD) and the voltage difference between the PPD and the floating diffusion (FD) node by controlling and optimizing the N doping concentration in the PPD and the threshold voltage of the reset transistor, respectively. The techniques shorten the charge transfer time from the PPD diode to the FD node effectively. The proposed process techniques do not need extra masks and do not cause harm to the fill factor. A sub array of 32 × 64 pixels was designed and implemented in the 0.18 μm CIS process with five implantation conditions splitting the N region in the PPD. The simulation and measured results demonstrate that the charge transfer time can be decreased by using the proposed techniques. Comparing the charge transfer time of the pixel with the different implantation conditions of the N region, the charge transfer time of 0.32 μs is achieved and 31% of image lag was reduced by using the proposed process techniques. (semiconductor devices)

Radiative transfer modeling through terrestrial atmosphere and ocean accounting for inelastic processes: Software package SCIATRAN

Science.gov (United States)

Rozanov, V. V.; Dinter, T.; Rozanov, A. V.; Wolanin, A.; Bracher, A.; Burrows, J. P.

2017-06-01

SCIATRAN is a comprehensive software package which is designed to model radiative transfer processes in the terrestrial atmosphere and ocean in the spectral range from the ultraviolet to the thermal infrared (0.18-40 μm). It accounts for multiple scattering processes, polarization, thermal emission and ocean-atmosphere coupling. The main goal of this paper is to present a recently developed version of SCIATRAN which takes into account accurately inelastic radiative processes in both the atmosphere and the ocean. In the scalar version of the coupled ocean-atmosphere radiative transfer solver presented by Rozanov et al. [61] we have implemented the simulation of the rotational Raman scattering, vibrational Raman scattering, chlorophyll and colored dissolved organic matter fluorescence. In this paper we discuss and explain the numerical methods used in SCIATRAN to solve the scalar radiative transfer equation including trans-spectral processes, and demonstrate how some selected radiative transfer problems are solved using the SCIATRAN package. In addition we present selected comparisons of SCIATRAN simulations with those published benchmark results, independent radiative transfer models, and various measurements from satellite, ground-based, and ship-borne instruments. The extended SCIATRAN software package along with a detailed User's Guide is made available for scientists and students, who are undertaking their own research typically at universities, via the web page of the Institute of Environmental Physics (IUP), University of Bremen: http://www.iup.physik.uni-bremen.de.

Transfer of ERR for radiation-related leukemia from Japanese population to Chinese population

International Nuclear Information System (INIS)

Huang Liqiong; Sun Zhijuan; Zhao Yongcheng; Wang Jixian

2011-01-01

Objective: To establish a transfer model for excess relative risk (ERR) for radiation-related leukemia from Japanese population to Chinese population. Methods: Combined ERR of several subtypes of leukemia published in 1994, with the corresponding leukemia baseline incidence rates obtained from Cancer Incidence in Five Continents Vol. Ⅸ (CI5-Ⅸ) for Japanese population and Chinese population, a weighted risk transfer model was employed between an additive model and a multiplicative model, to execute ERR transfer. Results: A range of weighing factors was proposed for risk transfer models: weighing factor was 0.4 for male and 0.3 for female, acute lymphoblastic leukemia, acute myeloid leukemia and chronic myeloid leukemia. The uncertainty for ERR transfer was characterized by lognormal distribution. Conclusions: Based on the difference of baseline incidence rate for subtypes of leukemia between Japanese population and Chinese population, the transfer model and these weighing factors discussed in the present study could be applicable to transfer ERR for radiation-related leukemia from Japanese population to Chinese population. (authors)

Radiative heat transfer between nanoparticles enhanced by intermediate particle

Directory of Open Access Journals (Sweden)

Yanhong Wang

2016-02-01

Full Text Available Radiative heat transfer between two polar nanostructures at different temperatures can be enhanced by resonant tunneling of surface polaritons. Here we show that the heat transfer between two nanoparticles is strongly varied by the interactions with a third nanoparticle. By controlling the size of the third particle, the time scale of thermalization toward the thermal bath temperature can be modified over 5 orders of magnitude. This effect provides control of temperature distribution in nanoparticle aggregation and facilitates thermal management at nanoscale.

Radiation technologies and techniques friendly for environment and men

International Nuclear Information System (INIS)

Chmielewski, A.G.; Walis, L.

1995-01-01

Development of radiation technologies and techniques in Poland has been shown. Especially thermoshrinkable olefins with shape memory, fast thermistors and radiation sterilization have been presented. Also the radiometric gages produced in the Institute of Nuclear Chemistry and Technology, Warsaw for air monitoring have been described. A broad group of radiotracer techniques being used for environmental study have been presented as well. Radiation technologies with electron beam use for flue gas purification, sewage sludge hygienization and food processing have been shown and their development has been discussed

Development of a GPU-based high-performance radiative transfer model for the Infrared Atmospheric Sounding Interferometer (IASI)

International Nuclear Information System (INIS)

Huang Bormin; Mielikainen, Jarno; Oh, Hyunjong; Allen Huang, Hung-Lung

2011-01-01

Satellite-observed radiance is a nonlinear functional of surface properties and atmospheric temperature and absorbing gas profiles as described by the radiative transfer equation (RTE). In the era of hyperspectral sounders with thousands of high-resolution channels, the computation of the radiative transfer model becomes more time-consuming. The radiative transfer model performance in operational numerical weather prediction systems still limits the number of channels we can use in hyperspectral sounders to only a few hundreds. To take the full advantage of such high-resolution infrared observations, a computationally efficient radiative transfer model is needed to facilitate satellite data assimilation. In recent years the programmable commodity graphics processing unit (GPU) has evolved into a highly parallel, multi-threaded, many-core processor with tremendous computational speed and very high memory bandwidth. The radiative transfer model is very suitable for the GPU implementation to take advantage of the hardware's efficiency and parallelism where radiances of many channels can be calculated in parallel in GPUs. In this paper, we develop a GPU-based high-performance radiative transfer model for the Infrared Atmospheric Sounding Interferometer (IASI) launched in 2006 onboard the first European meteorological polar-orbiting satellites, METOP-A. Each IASI spectrum has 8461 spectral channels. The IASI radiative transfer model consists of three modules. The first module for computing the regression predictors takes less than 0.004% of CPU time, while the second module for transmittance computation and the third module for radiance computation take approximately 92.5% and 7.5%, respectively. Our GPU-based IASI radiative transfer model is developed to run on a low-cost personal supercomputer with four GPUs with total 960 compute cores, delivering near 4 TFlops theoretical peak performance. By massively parallelizing the second and third modules, we reached 364x

Analysis of radiative heat transfer impact in cross-flow tube and fin heat exchangers

Directory of Open Access Journals (Sweden)

Hanuszkiewicz-Drapała Małgorzata

2016-03-01

Full Text Available A cross-flow, tube and fin heat exchanger of the water – air type is the subject of the analysis. The analysis had experimental and computational form and was aimed for evaluation of radiative heat transfer impact on the heat exchanger performance. The main element of the test facility was an enlarged recurrent segment of the heat exchanger under consideration. The main results of measurements are heat transfer rates, as well as temperature distributions on the surface of the first fin obtained by using the infrared camera. The experimental results have been next compared to computational ones coming from a numerical model of the test station. The model has been elaborated using computational fluid dynamics software. The computations have been accomplished for two cases: without radiative heat transfer and taking this phenomenon into account. Evaluation of the radiative heat transfer impact in considered system has been done by comparing all the received results.

Using Neural Networks to Improve the Performance of Radiative Transfer Modeling Used for Geometry Dependent LER Calculations

Science.gov (United States)

Fasnacht, Z.; Qin, W.; Haffner, D. P.; Loyola, D. G.; Joiner, J.; Krotkov, N. A.; Vasilkov, A. P.; Spurr, R. J. D.

2017-12-01

In order to estimate surface reflectance used in trace gas retrieval algorithms, radiative transfer models (RTM) such as the Vector Linearized Discrete Ordinate Radiative Transfer Model (VLIDORT) can be used to simulate the top of the atmosphere (TOA) radiances with advanced models of surface properties. With large volumes of satellite data, these model simulations can become computationally expensive. Look up table interpolation can improve the computational cost of the calculations, but the non-linear nature of the radiances requires a dense node structure if interpolation errors are to be minimized. In order to reduce our computational effort and improve the performance of look-up tables, neural networks can be trained to predict these radiances. We investigate the impact of using look-up table interpolation versus a neural network trained using the smart sampling technique, and show that neural networks can speed up calculations and reduce errors while using significantly less memory and RTM calls. In future work we will implement a neural network in operational processing to meet growing demands for reflectance modeling in support of high spatial resolution satellite missions.

3D-radiative transfer in terrestrial atmosphere: An efficient parallel numerical procedure

Science.gov (United States)

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

Stochastic Radiative Transfer Model for Contaminated Rough Surfaces: A Framework for Detection System Design

Science.gov (United States)

2013-11-01

example for the detection of a potassium chlorate contaminated “car” with a CO2 tunable laser system. 15. SUBJECT TERMS Radiative transfer...detector m-out-of-n detector Potassium chlorate Probability theory System performance Probability of detection and false alarm iii...for the detection of a potassium chlorate contaminated “car” with a CO2 tunable laser system. Subject Terms Radiative transfer, contaminated

Interference-exact radiative transfer equation

DEFF Research Database (Denmark)

Partanen, Mikko; Haÿrynen, Teppo; Oksanen, Jani

2017-01-01

Maxwell's equations with stochastic or quantum optical source terms accounting for the quantum nature of light. We show that both the nonlocal wave and local particle features associated with interference and emission of propagating fields in stratified geometries can be fully captured by local damping...... and scattering coefficients derived from the recently introduced quantized fluctuational electrodynamics (QFED) framework. In addition to describing the nonlocal optical interference processes as local directionally resolved effects, this allows reformulating the well known and widely used radiative transfer...... equation (RTE) as a physically transparent interference-exact model that extends the useful range of computationally efficient and quantum optically accurate interference-aware optical models from simple structures to full optical devices....

Analytical research using synchrotron radiation based techniques

International Nuclear Information System (INIS)

Jha, Shambhu Nath

2015-01-01

There are many Synchrotron Radiation (SR) based techniques such as X-ray Absorption Spectroscopy (XAS), X-ray Fluorescence Analysis (XRF), SR-Fourier-transform Infrared (SRFTIR), Hard X-ray Photoelectron Spectroscopy (HAXPS) etc. which are increasingly being employed worldwide in analytical research. With advent of modern synchrotron sources these analytical techniques have been further revitalized and paved ways for new techniques such as microprobe XRF and XAS, FTIR microscopy, Hard X-ray Photoelectron Spectroscopy (HAXPS) etc. The talk will cover mainly two techniques illustrating its capability in analytical research namely XRF and XAS. XRF spectroscopy: XRF spectroscopy is an analytical technique which involves the detection of emitted characteristic X-rays following excitation of the elements within the sample. While electron, particle (protons or alpha particles), or X-ray beams can be employed as the exciting source for this analysis, the use of X-ray beams from a synchrotron source has been instrumental in the advancement of the technique in the area of microprobe XRF imaging and trace level compositional characterisation of any sample. Synchrotron radiation induced X-ray emission spectroscopy, has become competitive with the earlier microprobe and nanoprobe techniques following the advancements in manipulating and detecting these X-rays. There are two important features that contribute to the superb elemental sensitivities of microprobe SR induced XRF: (i) the absence of the continuum (Bremsstrahlung) background radiation that is a feature of spectra obtained from charged particle beams, and (ii) the increased X-ray flux on the sample associated with the use of tunable third generation synchrotron facilities. Detection sensitivities have been reported in the ppb range, with values of 10 -17 g - 10 -14 g (depending on the particular element and matrix). Keeping in mind its demand, a microprobe XRF beamline has been setup by RRCAT at Indus-2 synchrotron

Bivariational calculations for radiation transfer in an inhomogeneous participating media

International Nuclear Information System (INIS)

El Wakil, S.A.; Machali, H.M.; Haggag, M.H.; Attia, M.T.

1986-07-01

Equations for radiation transfer are obtained for dispersive media with space dependent albedo. Bivariational bound principle is used to calculate the reflection and transmission coefficients for such media. Numerical results are given and compared. (author)

Linear circuit transfer functions an introduction to fast analytical techniques

CERN Document Server

Basso, Christophe P

2016-01-01

Linear Circuit Transfer Functions: An introduction to Fast Analytical Techniques teaches readers how to determine transfer functions of linear passive and active circuits by applying Fast Analytical Circuits Techniques. Building on their existing knowledge of classical loop/nodal analysis, the book improves and expands their skills to unveil transfer functions in a swift and efficient manner. Starting with simple examples, the author explains step-by-step how expressing circuits time constants in different configurations leads to writing transfer functions in a compact and insightful way. By learning how to organize numerators and denominators in the fastest possible way, readers will speed-up analysis and predict the frequency resp nse of simple to complex circuits. In some cases, they will be able to derive the final expression by inspection, without writing a line of algebra. Key features: * Emphasizes analysis through employing time constant-based methods discussed in other text books but not widely us...

Chirality transfer technique between liquid crystal microdroplets using microfluidic systems

Science.gov (United States)

Guo, Jin-kun; Lee, Doyeon; Song, Jang-kun

2018-02-01

Cholesteric liquid crystal (LC) microdroplet is applied in many areas, such as tunable laser, biosensor, information display and security identification, due to its unique optical properties. The topological structure, defects, and photonic crystallinity in the cholesteric liquid crystal (LC) microdroplet can be controlled through the chirality. Here we report an interesting phenomenon that chirality information can be shared among dispersed LC microdroplets in surfactant aqueous solution, which is driven by the transferring of chiral dopant molecules. As a result, we developed an artificial molecule transfer technology which could in situ vary the material composition within the isolated dispersed microdroplets. The molecular transfer is switchable and the transfer speed is controllable by tuning the molecular solubility in continuous phase. Based on this technique, we manipulated, forward and backward, the topological evolution and the photonic crystal band-gap of the dispersed LC droplet. This technique is an easy and powerful experimental tool, and it may be applicable to other fields in optical application, biology, chemistry and material science.

Radiative transfer in a strongly magnetized plasma. I. Effects of Anisotropy

International Nuclear Information System (INIS)

Nagel, W.

1981-01-01

We present results of radiative transfer calculations for radiating slabs and columns of strongly magnetized plasma. The angular dependence of the escaping radiation was found numerically by Feautrier's method, using the differential scattering cross sections derived by Ventura. We also give an approximate analytical expression for the anisotropy of the outgoing radiation, based on a system of two coupled diffusion equations for ordinary and extraordinary photons. Giving the polarization dependence of the beaming pattern of radiating slabs as well as columns, we generalize previous results of Basko and Kanno. Some implications for models of the pulsating X-ray source Her X-1 are discussed

Analytical heat transfer modeling of a new radiation calorimeter

Energy Technology Data Exchange (ETDEWEB)

Obame Ndong, Elysée [Department of Industrial Engineering and Maintenance, University of Sciences and Technology of Masuku (USTM), BP 941 Franceville (Gabon); Grenoble Electrical Engineering Laboratory (G2Elab), University Grenoble Alpes and CNRS, G2Elab, F38000 Grenoble (France); Gallot-Lavallée, Olivier [Grenoble Electrical Engineering Laboratory (G2Elab), University Grenoble Alpes and CNRS, G2Elab, F38000 Grenoble (France); Aitken, Frédéric, E-mail: frederic.aitken@g2elab.grenoble-inp.fr [Grenoble Electrical Engineering Laboratory (G2Elab), University Grenoble Alpes and CNRS, G2Elab, F38000 Grenoble (France)

2016-06-10

Highlights: • Design of a new calorimeter for measuring heat power loss in electrical components. • The calorimeter can operate in a temperature range from −50 °C to 150 °C. • An analytical model of heat transfers for this new calorimeter is presented. • The theoretical sensibility of the new apparatus is estimated at ±1 mW. - Abstract: This paper deals with an analytical modeling of heat transfers simulating a new radiation calorimeter operating in a temperature range from −50 °C to 150 °C. The aim of this modeling is the evaluation of the feasibility and performance of the calorimeter by assessing the measurement of power losses of some electrical devices by radiation, the influence of the geometry and materials. Finally a theoretical sensibility of the new apparatus is estimated at ±1 mW. From these results the calorimeter has been successfully implemented and patented.

Analytical heat transfer modeling of a new radiation calorimeter

International Nuclear Information System (INIS)

Obame Ndong, Elysée; Gallot-Lavallée, Olivier; Aitken, Frédéric

2016-01-01

Highlights: • Design of a new calorimeter for measuring heat power loss in electrical components. • The calorimeter can operate in a temperature range from −50 °C to 150 °C. • An analytical model of heat transfers for this new calorimeter is presented. • The theoretical sensibility of the new apparatus is estimated at ±1 mW. - Abstract: This paper deals with an analytical modeling of heat transfers simulating a new radiation calorimeter operating in a temperature range from −50 °C to 150 °C. The aim of this modeling is the evaluation of the feasibility and performance of the calorimeter by assessing the measurement of power losses of some electrical devices by radiation, the influence of the geometry and materials. Finally a theoretical sensibility of the new apparatus is estimated at ±1 mW. From these results the calorimeter has been successfully implemented and patented.

Natural convective magneto-nanofluid flow and radiative heat transfer past a moving vertical plate

Directory of Open Access Journals (Sweden)

S. Das

2015-03-01

Full Text Available An investigation of the hydromagnetic boundary layer flow past a moving vertical plate in nanofluids in the presence of a uniform transverse magnetic field and thermal radiation has been carried out. Three different types of water-based nanofluids containing copper, aluminum oxide and titanium dioxide are taken into consideration. The governing equations are solved using Laplace transform technique and the solutions are presented in closed form. The numerical values of nanofluid temperature, velocity, the rate of heat transfer and the shear stress at the plate are presented graphically for several values of the pertinent parameters. The present study finds applications in engineering devices.

Performance Analysis of GFDL's GCM Line-By-Line Radiative Transfer Model on GPU and MIC Architectures

Science.gov (United States)

Menzel, R.; Paynter, D.; Jones, A. L.

2017-12-01

Due to their relatively low computational cost, radiative transfer models in global climate models (GCMs) run on traditional CPU architectures generally consist of shortwave and longwave parameterizations over a small number of wavelength bands. With the rise of newer GPU and MIC architectures, however, the performance of high resolution line-by-line radiative transfer models may soon approach those of the physical parameterizations currently employed in GCMs. Here we present an analysis of the current performance of a new line-by-line radiative transfer model currently under development at GFDL. Although originally designed to specifically exploit GPU architectures through the use of CUDA, the radiative transfer model has recently been extended to include OpenMP in an effort to also effectively target MIC architectures such as Intel's Xeon Phi. Using input data provided by the upcoming Radiative Forcing Model Intercomparison Project (RFMIP, as part of CMIP 6), we compare model results and performance data for various model configurations and spectral resolutions run on both GPU and Intel Knights Landing architectures to analogous runs of the standard Oxford Reference Forward Model on traditional CPUs.

Numerical simulation of heat transfer process in solar enhanced natural draft dry cooling tower with radiation model

International Nuclear Information System (INIS)

Wang, Qiuhuan; Zhu, Jialing; Lu, Xinli

2017-01-01

Graphical abstract: A 3-D numerical model integrated with a discrete ordinate (DO) solar radiation model (considering solar radiation effect in the room of solar collector) was developed to investigate the influence of solar radiation intensity and ambient pressure on the efficiency and thermal characteristics of the SENDDCT. Our study shows that introducing such a radiation model can more accurately simulate the heat transfer process in the SENDDCT. Calculation results indicate that previous simulations overestimated solar energy obtained by the solar collector and underestimated the heat loss. The cooling performance is improved when the solar radiation intensity or ambient pressure is high. Air temperature and velocity increase with the increase of solar radiation intensity. But ambient pressure has inverse effects on the changes of air temperature and velocity. Under a condition that the solar load increases but the ambient pressure decreases, the increased rate of heat transferred in the heat exchanger is not obvious. Thus the performance of the SENDDCT not only depends on the solar radiation intensity but also depends on the ambient pressure. - Highlights: • A radiation model has been introduced to accurately simulate heat transfer process. • Heat transfer rate would be overestimated if the radiation model was not introduced. • The heat transfer rate is approximately proportional to solar radiation intensity. • The higher the solar radiation or ambient pressure, the better SENDDCT performance. - Abstract: Solar enhanced natural draft dry cooling tower (SENDDCT) is more efficient than natural draft dry cooling tower by utilizing solar radiation in arid region. A three-dimensional numerical model considering solar radiation effect was developed to investigate the influence of solar radiation intensity and ambient pressure on the efficiency and thermal characteristics of SENDDCT. The numerical simulation outcomes reveal that a model with consideration of

Development of Plant Application Technique of Low Dose Radiation

Energy Technology Data Exchange (ETDEWEB)

Chung, Byung Yeoup; Kim, Jae Sung; Lim, Yong Taek (and others)

2007-07-15

The project was carried out to achieve three aims. First, development of application techniques of cell-stimulating effects by low-dose radiation. Following irradiation with gamma-rays of low doses, beneficial effects in crop germination, early growth, and yield were investigated using various plant species and experimental approaches. For the actual field application, corroborative studies were also carried out with a few concerned experimental stations and farmers. Moreover, we attempted to establish a new technique of cell cultivation for industrial mass-production of shikonin, a medicinal compound from Lithospermum erythrorhizon and thereby suggested new application fields for application techniques of low-dose radiation. Second, elucidation of action mechanisms of ionizing radiation in plants. By investigating changes in plant photosynthesis and physiological metabolism, we attempted to elucidate physiological activity-stimulating effects of low-dose radiation and to search for radiation-adaptive cellular components. Besides, analyses of biochemical and molecular biological mechanisms for stimulus-stimulating effects of low-dose radiation were accomplished by examining genes and proteins inducible by low-dose radiation. Third, development of functional crop plants using radiation-resistant factors. Changes in stress-tolerance of plants against environmental stress factors such as light, temperature, salinity and UV-B stress after exposed to low-dose gamma-rays were investigated. Concerned reactive oxygen species, antioxidative enzymes, and antioxidants were also analyzed to develop high value-added and environment-friendly functional plants using radiation-resistant factors. These researches are important to elucidate biological activities increased by low-dose radiation and help to provide leading technologies for improvement of domestic productivity in agriculture and development of high value-added genetic resources.

Development of Plant Application Technique of Low Dose Radiation

International Nuclear Information System (INIS)

Chung, Byung Yeoup; Kim, Jae Sung; Lim, Yong Taek

2007-07-01

The project was carried out to achieve three aims. First, development of application techniques of cell-stimulating effects by low-dose radiation. Following irradiation with gamma-rays of low doses, beneficial effects in crop germination, early growth, and yield were investigated using various plant species and experimental approaches. For the actual field application, corroborative studies were also carried out with a few concerned experimental stations and farmers. Moreover, we attempted to establish a new technique of cell cultivation for industrial mass-production of shikonin, a medicinal compound from Lithospermum erythrorhizon and thereby suggested new application fields for application techniques of low-dose radiation. Second, elucidation of action mechanisms of ionizing radiation in plants. By investigating changes in plant photosynthesis and physiological metabolism, we attempted to elucidate physiological activity-stimulating effects of low-dose radiation and to search for radiation-adaptive cellular components. Besides, analyses of biochemical and molecular biological mechanisms for stimulus-stimulating effects of low-dose radiation were accomplished by examining genes and proteins inducible by low-dose radiation. Third, development of functional crop plants using radiation-resistant factors. Changes in stress-tolerance of plants against environmental stress factors such as light, temperature, salinity and UV-B stress after exposed to low-dose gamma-rays were investigated. Concerned reactive oxygen species, antioxidative enzymes, and antioxidants were also analyzed to develop high value-added and environment-friendly functional plants using radiation-resistant factors. These researches are important to elucidate biological activities increased by low-dose radiation and help to provide leading technologies for improvement of domestic productivity in agriculture and development of high value-added genetic resources

Radiative and conductive heat transfer in a nongrey semitransparent medium. Application to fire protection curtains

Energy Technology Data Exchange (ETDEWEB)

Berour, Nacer; Lacroix, David E-mail: david.lacroix@lemta.uhp-nancy.fr; Boulet, Pascal; Jeandel, Gerard

2004-06-01

This paper deals with heat transfer in nongrey media which scatter, absorb and emit radiation. Considering a two dimensional geometry, radiative and conductive phenomena through the medium have been taken into account. The radiative part of the problem was solved using the discrete ordinate method with classical S{sub n} quadratures. The absorption and scattering coefficients involved in the radiative transfer equation (RTE) were obtained from the Mie theory. Conduction inside the medium was linked to the RTE through the energy conservation. Validation of the model has been achieved with several simulation of water spray curtains used as fire protection walls.

Radiative Heat Transfer with Nanowire/Nanohole Metamaterials for Thermal Energy Harvesting Applications

Science.gov (United States)

Chang, Jui-Yung

Recently, nanostructured metamaterials have attracted lots of attentions due to its tunable artificial properties. In particular, nanowire/nanohole based metamaterials which are known of the capability of large area fabrication were intensively studied. Most of the studies are only based on the electrical responses of the metamaterials; however, magnetic response, is usually neglected since magnetic material does not exist naturally within the visible or infrared range. For the past few years, artificial magnetic response from nanostructure based metamaterials has been proposed. This reveals the possibility of exciting resonance modes based on magnetic responses in nanowire/nanohole metamaterials which can potentially provide additional enhancement on radiative transport. On the other hand, beyond classical far-field radiative heat transfer, near-field radiation which is known of exceeding the Planck's blackbody limit has also become a hot topic in the field. This PhD dissertation aims to obtain a deep fundamental understanding of nanowire/nanohole based metamaterials in both far-field and near-field in terms of both electrical and magnetic responses. The underlying mechanisms that can be excited by nanowire/nanohole metamaterials such as electrical surface plasmon polariton, magnetic hyperbolic mode, magnetic polariton, etc., will be theoretically studied in both far-field and near-field. Furthermore, other than conventional effective medium theory which only considers the electrical response of metamaterials, the artificial magnetic response of metamaterials will also be studied through parameter retrieval of far-field optical and radiative properties for studying near-field radiative transport. Moreover, a custom-made AFM tip based metrology will be employed to experimentally study near-field radiative transfer between a plate and a sphere separated by nanometer vacuum gaps in vacuum. This transformative research will break new ground in nanoscale radiative heat

Reconstruction of solar spectral surface UV irradiances using radiative transfer simulations.

Science.gov (United States)

Lindfors, Anders; Heikkilä, Anu; Kaurola, Jussi; Koskela, Tapani; Lakkala, Kaisa

2009-01-01

UV radiation exerts several effects concerning life on Earth, and spectral information on the prevailing UV radiation conditions is needed in order to study each of these effects. In this paper, we present a method for reconstruction of solar spectral UV irradiances at the Earth's surface. The method, which is a further development of an earlier published method for reconstruction of erythemally weighted UV, relies on radiative transfer simulations, and takes as input (1) the effective cloud optical depth as inferred from pyranometer measurements of global radiation (300-3000 nm); (2) the total ozone column; (3) the surface albedo as estimated from measurements of snow depth; (4) the total water vapor column; and (5) the altitude of the location. Reconstructed daily cumulative spectral irradiances at Jokioinen and Sodankylä in Finland are, in general, in good agreement with measurements. The mean percentage difference, for instance, is mostly within +/-8%, and the root mean square of the percentage difference is around 10% or below for wavelengths over 310 nm and daily minimum solar zenith angles (SZA) less than 70 degrees . In this study, we used pseudospherical radiative transfer simulations, which were shown to improve the performance of our method under large SZA (low Sun).

Comparing radiation exposure during percutaneous vertebroplasty using one- vs. two-fluoroscopic technique

Directory of Open Access Journals (Sweden)

Li Yen-Yao

2013-01-01

Full Text Available Abstract Background Percutaneous vertebroplasty (PV requires relatively lengthy fluoroscopic guidance, which might lead to substantial radiation exposure to patients or operators. The two-fluoroscopic technique (two-plane radiographs obtained using two fluoroscopes during PV can provide simultaneous two-planar projections with reducing operative time. However, the two-fluoroscopic technique may expose the operator or patient to increased radiation dose. The aim of this study was to quantify the amount of radiation exposure to the patient or operator that occurs during PV using one- vs. two-fluoroscopic technique. Methods Two radiation dosimeters were placed on the right flank of each patient and on the upper sternum of each operator during 26 single-level PV procedures by one senior surgeon. The use of two-fluoroscopic technique (13 patients and one-fluoroscopic technique (13 patients were allocated in a consecutive and alternative manner. The operative time and mean radiation dose to each patient and operator were monitored and compared between groups. Results Mean radiation dose to the patient was 1.97 ± 1.20 mSv (95% CI, 0.71 to 3.23 for the one-fluoroscopic technique group vs. 0.95 ± 0.34 mSv (95% CI, 0.85 to 1.23 for the two-fluoroscopic technique group (P =0.031. Mean radiation dose to the operator was 0.27 ± 0.12 mSv (95% CI, 0.17–0.56 for the one-fluoroscopic technique group vs. 0.25 ± 0.14 mSv (95% CI, 0.06–0.44 for the two-fluoroscopic technique group (P = 0.653. The operative time was significantly different between groups: 47.15 ± 13.48 min (range, 20–75 for the one-fluoroscopic technique group vs. 36.62 ± 8.42 min (range, 21–50 for the two-fluoroscopic technique group (P =0.019. Conclusion Compared to the one-fluoroscopic technique, the two-fluoroscopic technique used during PV provides not only shorter operative times but also reduces the radiation exposure to the patient. There was no

The Role of IAEA in Coordinating Research and Transferring Technology in Radiation Chemistry and Processing of Polymers

International Nuclear Information System (INIS)

Haji Saeid, M.

2006-01-01

The IAEA has been playing a significant role in fostering developments in radiation technology in general and radiation processing of polymers in particular, among its Member States (MS) and facilitate know-how/technology transfer to developing MS. The former is usually achieved through coordinated research projects (CRP) and thematic technical meetings, while the latter is mainly accomplished through Technical Cooperation (TC) projects. Coordinated research projects encourage research on, and development and practical application of, radiation technology to foster exchange of scientific and technical information. The CRP brings together typically 10 - 15 groups of participants to share and complement core competencies and work on specific areas of development needed to benefit from an emerging radiation technique and its applications. The technical cooperation (TC) programme helps Member States realize their development priorities through the application of appropriate radiation technology. TC builds national capacities through training, expert advice and delivery of equipment. The impact of the IAEA's efforts is visible by the progress noticeable in adoption of radiation technology and/or growth in the range of activities in several MS in different regions. The IAEA has implemented several coordinated research projects (CRP) recently, including one on-going project, in the field of radiation processing of polymeric materials. The CRPs facilitated the acquisition and dissemination of know-how and technology for controlling of degradation effects in radiation processing of polymers, radiation synthesis of stimuli-responsive membranes, hydrogels and absorbents for separation purposes and the use of radiation processing to prepare biomaterials for applications in medicine. A number of technical cooperation projects have been implemented in this field to strengthen the capability of developing Member States and to create awareness in the industries about the technical

Using analytic derivatives to assess the impact of phase function Fourier decomposition technique on the accuracy of a radiative transfer model

International Nuclear Information System (INIS)

Sanghavi, Suniti; Natraj, Vijay

2013-01-01

Fourier decomposition of the phase function is essential to decouple the azimuthal component of the radiative transfer equation for multiple scattering calculations. This decomposition can be carried out by means of a direct numerical method based on the definition of the Fourier transform (numFT), or by an expansion of the phase function in terms of spherical Legendre polynomials (sphFT). numFT requires interpolation of the phase function between discrete angles, leading to spurious errors in the final computations. This error is difficult to quantify by means of intensity-only computations, since it is hard to determine the absolute accuracy of any given approach. We show that a linearization (analytic computation of derivatives) of the intensity with respect to parameters governing the phase function can be compared against results using the finite difference method, thereby providing a self-consistency test for characterizing and quantifying the error. We have applied this approach to two linearized versions of the Matrix Operator Method, which are identical in all respects except that one uses numFT while the other uses sphFT. In both cases, we compute the derivatives of the intensity with respect to aerosol parameters governing scattering in the simulated atmosphere. Comparison of the derivatives against their finite difference estimates shows a reduction of error by several orders of magnitude when Legendre polynomials are employed. We have also examined the effect of the angular resolution of the phase function on the error due to the numFT technique. A general reduction of error is seen with increasing angular resolution, indicating that interpolation is indeed the major error source. Also, we have pointed out a related source of error in numFT computations that occurs when Fourier decomposition is carried out on the composite phase function of a layer consisting of more than one scatterer. We conclude that an expansion of the phase function in terms of

Principles and techniques of radiation hardening. Volume 2. Transient radiation effects in electronics (TREE)

International Nuclear Information System (INIS)

Rudie, N.J.

1976-01-01

The three-volume book is intended to serve as a review of the effects of thermonuclear explosion induced radiation (x-rays, gamma rays, and beta particles) and the resulting electromagnetic pulse (EMP). Volume 2 deals with the following topics: radiation effects on quartz crystals, tantalum capacitors, bipolar semiconductor devices and integrated circuits, field effect transistors, and miscellaneous electronic devices; hardening electronic systems to photon and neutron radiation; nuclear radiation source and/or effects simulation techniques; and radiation dosimetry

Homogenization of a Conductive-Radiative Heat Transfer Problem

Directory of Open Access Journals (Sweden)

Habibi Zakaria

2012-04-01

Full Text Available This paper focuses on the contribution of the second order corrector in periodic homogenization applied to a conductive-radiative heat transfer problem. Especially, for a heat conduction problem in a periodically perforated domain with a non-local boundary condition modelling the radiative heat transfer, if this model contains an oscillating thermal source and a thermal exchange with the perforations, the second order corrector helps us to model the gradients which appear between the source area and the perforations. Ce papier est consacré à montrer l’influence du correcteur de second ordre en homogénéisation périodique. Dans l’homogénéisation d’un problème de conduction rayonnement dans un domaine périodiquement perforé par plusieurs trous, on peut voir une contribution non négligeable de ce correcteur lors de la présence d’une source thermique oscillante et d’un échange thermique dans les perforations. Ce correcteur nous permet de modéliser les gradients qui apparaissent entre la zone de la source thermique et les perforations.

Spectral collocation method with a flexible angular discretization scheme for radiative transfer in multi-layer graded index medium

Science.gov (United States)

Wei, Linyang; Qi, Hong; Sun, Jianping; Ren, Yatao; Ruan, Liming

2017-05-01

The spectral collocation method (SCM) is employed to solve the radiative transfer in multi-layer semitransparent medium with graded index. A new flexible angular discretization scheme is employed to discretize the solid angle domain freely to overcome the limit of the number of discrete radiative direction when adopting traditional SN discrete ordinate scheme. Three radial basis function interpolation approaches, named as multi-quadric (MQ), inverse multi-quadric (IMQ) and inverse quadratic (IQ) interpolation, are employed to couple the radiative intensity at the interface between two adjacent layers and numerical experiments show that MQ interpolation has the highest accuracy and best stability. Variable radiative transfer problems in double-layer semitransparent media with different thermophysical properties are investigated and the influence of these thermophysical properties on the radiative transfer procedure in double-layer semitransparent media is also analyzed. All the simulated results show that the present SCM with the new angular discretization scheme can predict the radiative transfer in multi-layer semitransparent medium with graded index efficiently and accurately.

Cytogenetic techniques as biological indicator and dosimeter of radiation damage

International Nuclear Information System (INIS)

Hadjidekova, V.; Hristova, R.

2006-01-01

Full text: The cytogenetic methods are established techniques for bio monitoring and bio dosimetry of professionally and accidentally exposed to ionizing radiation subjects. They are applied to continue the evaluation of the physical dosimetry and to consider the individual radiosensitivity. The results of cytogenetic monitoring and dosimetry of radiation exposed subjects carried out during the last 5 years in laboratory of Radiation Genetics, NCRRP is reported. Laboratory of Radiation genetics performs cytogenetic monitoring of low dose radiation professionally or medically exposed subjects: workers in Kozloduy NPP, radioactive waste repository workers, X-rays diagnostically exposed patients, and radiotherapy exposed as well. Three cytogenetic indicators are applied as the most sensitive indicators for human radiation exposure: analysis of micronuclei (MN), chromosomal aberrations (CA) and stable translocations (FISH). The optimized methodology for application of different cytogenetic techniques for radiation estimation is discussed

Intensity-modulated radiation therapy clinical evidence and techniques

CERN Document Server

Nishimura, Yasumasa

2015-01-01

Successful clinical use of intensity-modulated radiation therapy (IMRT) represents a significant advance in radiation oncology. Because IMRT can deliver high-dose radiation to a target with a reduced dose to the surrounding organs, it can improve the local control rate and reduce toxicities associated with radiation therapy. Since IMRT began being used in the mid-1990s, a large volume of clinical evidence of the advantages of IMRT has been collected. However, treatment planning and quality assurance (QA) of IMRT are complicated and difficult for the clinician and the medical physicist. This book, by authors renowned for their expertise in their fields, provides cumulative clinical evidence and appropriate techniques for IMRT for the clinician and the physicist. Part I deals with the foundations and techniques, history, principles, QA, treatment planning, radiobiology and related aspects of IMRT. Part II covers clinical applications with several case studies, describing contouring and dose distribution with cl...

Directional radiometry and radiative transfer: A new paradigm

International Nuclear Information System (INIS)

Mishchenko, Michael I.

2011-01-01

Measurements with directional radiometers and calculations based on the radiative transfer equation (RTE) have been at the very heart of weather and climate modeling and terrestrial remote sensing. The quantification of the energy budget of the Earth's climate system requires exquisite measurements and computations of the incoming and outgoing electromagnetic energy, while global characterization of climate system's components relies heavily on theoretical inversions of observational data obtained with various passive and active instruments. The same basic problems involving electromagnetic energy transport and its use for diagnostic and characterization purposes are encountered in numerous other areas of science, biomedicine, and engineering. Yet both the discipline of directional radiometry and the radiative transfer theory (RTT) have traditionally been based on phenomenological concepts many of which turn out to be profound misconceptions. Contrary to the widespread belief, a collimated radiometer does not, in general, measure the flow of electromagnetic energy along its optical axis, while the specific intensity does not quantify the amount of electromagnetic energy transported in a given direction. The recently developed microphysical approach to radiative transfer and directional radiometry is explicitly based on the Maxwell equations and clarifies the physical nature of measurements with collimated radiometers and the actual content of the RTE. It reveals that the specific intensity has no fundamental physical meaning besides being a mathematical solution of the RTE, while the RTE itself is nothing more than an intermediate auxiliary equation. Only under special circumstances detailed in this review can the solution of the RTE be used to compute the time-averaged local Poynting vector as well as be measured by a collimated radiometer. These firmly established facts make the combination of the RTE and a collimated radiometer useful in a well-defined range of

Free convection effects and radiative heat transfer in MHD Stokes ...

Indian Academy of Sciences (India)

... radiative heat transfer is useful for predicting the heat feedback to the burning surface ... petroleum technology, to study the movement of natural gas, oil and water ... (e.g. sea water, rain water, and sewage) past an impulsively started infinite ...

An asymptotic preserving unified gas kinetic scheme for frequency-dependent radiative transfer equations

Energy Technology Data Exchange (ETDEWEB)

Sun, Wenjun, E-mail: sun_wenjun@iapcm.ac.cn [Institute of Applied Physics and Computational Mathematics, P.O. Box 8009, Beijing 100088 (China); Jiang, Song, E-mail: jiang@iapcm.ac.cn [Institute of Applied Physics and Computational Mathematics, P.O. Box 8009, Beijing 100088 (China); Xu, Kun, E-mail: makxu@ust.hk [Department of Mathematics and Department of Mechanical and Aerospace Engineering, Hong Kong University of Science and Technology, Hong Kong (China); Li, Shu, E-mail: li_shu@iapcm.ac.cn [Institute of Applied Physics and Computational Mathematics, P.O. Box 8009, Beijing 100088 (China)

2015-12-01

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 the 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

Experimental investigation of convective heat transfer augmentation for car radiator using ZnO–water nanofluids

International Nuclear Information System (INIS)

Ali, Hafiz Muhammad; Ali, Hassan; Liaquat, Hassan; Bin Maqsood, Hafiz Talha; Nadir, Malik Ahmed

2015-01-01

New experimental data are reported for water based nanofluids to enhance the heat transfer performance of a car radiator. ZnO nanoparticles have been added into base fluid in different volumetric concentrations (0.01%, 0.08%, 0.2% and 0.3%). The effect of these volumetric concentrations on the heat transfer performance for car radiator is determined experimentally. Fluid flow rate has been varied in a range of 7–11 LPM (liter per minute) (corresponding Reynolds number range was 17,500–27,600). Nanofluids showed heat transfer enhancement compared to the base fluid for all concentrations tested. The best heat transfer enhancement up to 46% was found compared to base fluid at 0.2% volumetric concentration. A further increase in volumetric concentration to 0.3% has shown a decrease in heat transfer enhancement compared to 0.2% volumetric concentration. Fluid inlet temperature was kept in a range of 45–55 °C. An increase in fluid inlet temperature from 45 °C to 55 °C showed increase in heat transfer rate up to 4%. - Highlights: • ZnO–water nanofluids were used for car radiator thermal enhancement. • Heat transfer enhancement up to 46% was achieved comparing pure water. • 0.2% vol. concentration of ZnO found to be optimum for heat transfer. • Heat transfer was found weakly dependant on the fluid inlet temperature

Spatial discretizations for self-adjoint forms of the radiative transfer equations

International Nuclear Information System (INIS)

Morel, Jim E.; Adams, B. Todd; Noh, Taewan; McGhee, John M.; Evans, Thomas M.; Urbatsch, Todd J.

2006-01-01

There are three commonly recognized second-order self-adjoint forms of the neutron transport equation: the even-parity equations, the odd-parity equations, and the self-adjoint angular flux equations. Because all of these equations contain second-order spatial derivatives and are self-adjoint for the mono-energetic case, standard continuous finite-element discretization techniques have proved quite effective when applied to the spatial variables. We first derive analogs of these equations for the case of time-dependent radiative transfer. The primary unknowns for these equations are functions of the angular intensity rather than the angular flux, hence the analog of the self-adjoint angular flux equation is referred to as the self-adjoint angular intensity equation. Then we describe a general, arbitrary-order, continuous spatial finite-element approach that is applied to each of the three equations in conjunction with backward-Euler differencing in time. We refer to it as the 'standard' technique. We also introduce an alternative spatial discretization scheme for the self-adjoint angular intensity equation that requires far fewer unknowns than the standard method, but appears to give comparable accuracy. Computational results are given that demonstrate the validity of both of these discretization schemes

The log mean heat transfer rate method of heat exchanger considering the influence of heat radiation

International Nuclear Information System (INIS)

Wong, K.-L.; Ke, M.-T.; Ku, S.-S.

2009-01-01

The log mean temperature difference (LMTD) method is conventionally used to calculate the total heat transfer rate of heat exchangers. Because the heat radiation equation contains the 4th order exponential of temperature which is very complicate in calculations, thus LMTD method neglects the influence of heat radiation. From the recent investigation of a circular duct in some practical situations, it is found that even in the situation of the temperature difference between outer duct surface and surrounding is low to 1 deg. C, the heat radiation effect can not be ignored in the situations of lower ambient convective heat coefficient and greater surface emissivities. In this investigation, the log mean heat transfer rate (LMHTR) method which considering the influence of heat radiation, is developed to calculate the total heat transfer rate of heat exchangers.

Synchrotron radiation based analytical techniques (XAS and XRF)

International Nuclear Information System (INIS)

Jha, Shambhu Nath

2014-01-01

A brief description of the principles of X-ray absorption spectroscopy (XAS) and X-ray fluorescence (XRF) techniques is given in this article with emphasis on the advantages of using synchrotron radiation-based instrumentation/beamline. XAS technique is described in more detail to emphasize the strength of the technique as a local structural probe. (author)

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

International Nuclear Information System (INIS)

Kevin Jerome Sutherland

2001-01-01

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-electronic 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

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

Energy Technology Data Exchange (ETDEWEB)

Sutherland, Kevin Jerome [Iowa State Univ., Ames, IA (United States)

2001-01-01

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-electronic 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.

Evaluation of radiation heat transfer in porous medial: Application for a pebble bed modular reactor cooled by CO2 gas

Directory of Open Access Journals (Sweden)

Sidi-Ali Kamel

2013-01-01

Full Text Available This work analyses the contribution of radiation heat transfer in the cooling of a pebble bed modular reactor. The mathematical model, developed for a porous medium, is based on a set of equations applied to an annular geometry. Previous major works dealing with the subject have considered the forced convection mode and often did not take into account the radiation heat transfer. In this work, only free convection and radiation heat transfer are considered. This can occur during the removal of residual heat after shutdown or during an emergency situation. In order to derive the governing equations of radiation heat transfer, a steady-state in an isotropic and emissive porous medium (CO2 is considered. The obtained system of equations is written in a dimensionless form and then solved. In order to evaluate the effect of radiation heat transfer on the total heat removed, an analytical method for solving the system of equations is used. The results allow quantifying both radiation and free convection heat transfer. For the studied situation, they show that, in a pebble bed modular reactor, more than 70% of heat is removed by radiation heat transfer when CO2 is used as the coolant gas.

A NUMERICAL SCHEME FOR SPECIAL RELATIVISTIC RADIATION MAGNETOHYDRODYNAMICS BASED ON SOLVING THE TIME-DEPENDENT RADIATIVE TRANSFER EQUATION

Energy Technology Data Exchange (ETDEWEB)

Ohsuga, Ken; Takahashi, Hiroyuki R. [National Astronomical Observatory of Japan, Osawa, Mitaka, Tokyo 181-8588 (Japan)

2016-02-20

We develop a numerical scheme for solving the equations of fully special relativistic, radiation magnetohydrodynamics (MHDs), in which the frequency-integrated, time-dependent radiation transfer equation is solved to calculate the specific intensity. The radiation energy density, the radiation flux, and the radiation stress tensor are obtained by the angular quadrature of the intensity. In the present method, conservation of total mass, momentum, and energy of the radiation magnetofluids is guaranteed. We treat not only the isotropic scattering but also the Thomson scattering. The numerical method of MHDs is the same as that of our previous work. The advection terms are explicitly solved, and the source terms, which describe the gas–radiation interaction, are implicitly integrated. Our code is suitable for massive parallel computing. We present that our code shows reasonable results in some numerical tests for propagating radiation and radiation hydrodynamics. Particularly, the correct solution is given even in the optically very thin or moderately thin regimes, and the special relativistic effects are nicely reproduced.

Performance of the dot product function in radiative transfer code SORD

Science.gov (United States)

Korkin, Sergey; Lyapustin, Alexei; Sinyuk, Aliaksandr; Holben, Brent

2016-10-01

The successive orders of scattering radiative transfer (RT) codes frequently call the scalar (dot) product function. In this paper, we study performance of some implementations of the dot product in the RT code SORD using 50 scenarios for light scattering in the atmosphere-surface system. In the dot product function, we use the unrolled loops technique with different unrolling factor. We also considered the intrinsic Fortran functions. We show results for two machines: ifort compiler under Windows, and pgf90 under Linux. Intrinsic DOT_PRODUCT function showed best performance for the ifort. For the pgf90, the dot product implemented with unrolling factor 4 was the fastest. The RT code SORD together with the interface that runs all the mentioned tests are publicly available from ftp://maiac.gsfc.nasa.gov/pub/skorkin/SORD_IP_16B (current release) or by email request from the corresponding (first) author.

Modeling of the coupled radiative and conductive heat transfer within fibrous media at high temperature

International Nuclear Information System (INIS)

Dauvois, Yann

2016-01-01

In the present work, the effective heat transfer properties of fibrous medium are determined by taking into account a coupling of heat conduction and radiation. A virtual, statistically homogeneous, two-phase fibrous sample has been built by stacking finite absorbing cylinders in vacuum. These cylinders are dispersed according to prescribed distribution functions defining the cylinder positions and orientations. Cylinder overlappings are allowed. Extinction, absorption and scattering are characterised by radiative statistical functions which allow the Beerian behaviour of a medium to be assessed (or not). They are accurately determined with a Monte Carlo method. Whereas the gaseous phase exhibits a Beerian behaviour, the fibre phase is strongly non Beerian. The radiative power field deposited within the fibrous material is calculated by resolving a model which couples a Generalized Radiative Transfer Equation (GRTE) and a classic Radiative Transfer Equation (RTE). The model of conduction transfer is based on a random walk method without meshing. The simulation of Brownian motion of walkers in fibres allows the energy equation to be solved. The idea of the method is to characterize the temperature in an elementary volume by the density of walkers, which roam the medium. The problem is governed by boundary conditions; A constant concentration of walkers (or a constant flux) is associated with a fixed temperature (or flux). (author) [fr

GAUSS-SEIDEL AND SUCCESSIVE OVERRELAXATION METHODS FOR RADIATIVE TRANSFER WITH PARTIAL FREQUENCY REDISTRIBUTION

International Nuclear Information System (INIS)

Sampoorna, M.; Bueno, J. Trujillo

2010-01-01

The linearly polarized solar limb spectrum that is produced by scattering processes contains a wealth of information on the physical conditions and magnetic fields of the solar outer atmosphere, but the modeling of many of its strongest spectral lines requires solving an involved non-local thermodynamic equilibrium radiative transfer problem accounting for partial redistribution (PRD) effects. Fast radiative transfer methods for the numerical solution of PRD problems are also needed for a proper treatment of hydrogen lines when aiming at realistic time-dependent magnetohydrodynamic simulations of the solar chromosphere. Here we show how the two-level atom PRD problem with and without polarization can be solved accurately and efficiently via the application of highly convergent iterative schemes based on the Gauss-Seidel and successive overrelaxation (SOR) radiative transfer methods that had been previously developed for the complete redistribution case. Of particular interest is the Symmetric SOR method, which allows us to reach the fully converged solution with an order of magnitude of improvement in the total computational time with respect to the Jacobi-based local accelerated lambda iteration method.

Gauss-Seidel and Successive Overrelaxation Methods for Radiative Transfer with Partial Frequency Redistribution

Science.gov (United States)

Sampoorna, M.; Trujillo Bueno, J.

2010-04-01

The linearly polarized solar limb spectrum that is produced by scattering processes contains a wealth of information on the physical conditions and magnetic fields of the solar outer atmosphere, but the modeling of many of its strongest spectral lines requires solving an involved non-local thermodynamic equilibrium radiative transfer problem accounting for partial redistribution (PRD) effects. Fast radiative transfer methods for the numerical solution of PRD problems are also needed for a proper treatment of hydrogen lines when aiming at realistic time-dependent magnetohydrodynamic simulations of the solar chromosphere. Here we show how the two-level atom PRD problem with and without polarization can be solved accurately and efficiently via the application of highly convergent iterative schemes based on the Gauss-Seidel and successive overrelaxation (SOR) radiative transfer methods that had been previously developed for the complete redistribution case. Of particular interest is the Symmetric SOR method, which allows us to reach the fully converged solution with an order of magnitude of improvement in the total computational time with respect to the Jacobi-based local accelerated lambda iteration method.

A statewide teleradiology system reduces radiation exposure and charges in transferred trauma patients.

Science.gov (United States)

Watson, Justin J J; Moren, Alexis; Diggs, Brian; Houser, Ben; Eastes, Lynn; Brand, Dawn; Bilyeu, Pamela; Schreiber, Martin; Kiraly, Laszlo

2016-05-01

Trauma transfer patients routinely undergo repeat imaging because of inefficiencies within the radiology system. In 2009, the virtual private network (VPN) telemedicine system was adopted throughout Oregon allowing virtual image transfer between hospitals. The startup cost was a nominal $3,000 per hospital. A retrospective review from 2007 to 2012 included 400 randomly selected adult trauma transfer patients based on a power analysis (200 pre/200 post). The primary outcome evaluated was reduction in repeat computed tomography (CT) scans. Secondary outcomes included cost savings, emergency department (ED) length of stay (LOS), and spared radiation. All data were analyzed using Mann-Whitney U and chi-square tests. P less than .05 indicated significance. Spared radiation was calculated as a weighted average per body region, and savings was calculated using charges obtained from Oregon Health and Science University radiology current procedural terminology codes. Four-hundred patients were included. Injury Severity Score, age, ED and overall LOS, mortality, trauma type, and gender were not statistically different between groups. The percentage of patients with repeat CT scans decreased after VPN implementation: CT abdomen (13.2% vs 2.8%, P < .01) and cervical spine (34.4% vs 18.2%, P < .01). Post-VPN, the total charges saved in 2012 for trauma transfer patients was $333,500, whereas the average radiation dose spared per person was 1.8 mSV. Length of stay in the ED for patients with Injury Severity Score less than 15 transferring to the ICU was decreased (P < .05). Implementation of a statewide teleradiology network resulted in fewer total repeat CT scans, significant savings, decrease in radiation exposure, and decreased LOS in the ED for patients with less complex injuries. The potential for health care savings by widespread adoption of a VPN is significant. Copyright © 2016 Elsevier Inc. All rights reserved.

Efficacy of Radiative Transfer Model Across Space, Time and Hydro-climates

Science.gov (United States)

Mohanty, B.; Neelam, M.

2017-12-01

The efficiency of radiative transfer model for better soil moisture retrievals is not yet clearly understood over natural systems with great variability and heterogeneity with respect to soil, land cover, topography, precipitation etc. However, this knowledge is important to direct and strategize future research direction and field campaigns. In this work, we present global sensitivity analysis (GSA) technique to study the influence of heterogeneity and uncertainties on radiative transfer model (RTM) and to quantify climate-soil-vegetation interactions. A framework is proposed to understand soil moisture mechanisms underlying these interactions, and influence of these interactions on soil moisture retrieval accuracy. Soil moisture dynamics is observed to play a key role in variability of these interactions, i.e., it enhances both mean and variance of soil-vegetation coupling. The analysis is conducted for different support scales (Point Scale, 800 m, 1.6 km, 3.2 km, 6.4 km, 12.8 km, and 36 km), seasonality (time), hydro-climates, aggregation (scaling) methods and across Level I and Level II ecoregions of contiguous USA (CONUS). For undisturbed natural environments such as SGP'97 (Oklahoma, USA) and SMEX04 (Arizona, USA), the sensitivity of TB to land surface variables remain nearly uniform and are not influenced by extent, support scales or averaging method. On the contrary, for anthropogenically-manipulated environments such as SMEX02 (Iowa, USA) and SMAPVEX12 (Winnipeg, Canada), the sensitivity to variables are highly influenced by the distribution of land surface heterogeneity and upscaling methods. The climate-soil-vegetation interactions analyzed across all ecoregions are presented through a probability distribution function (PDF). The intensity of these interactions are categorized accordingly to yield "hotspots", where the RTM model fails to retrieve soil moisture. A ecoregion specific scaling function is proposed for these hotspots to rectify RTM for

Calculations of combined radiation and convection heat transfer in rod bundles under emergency cooling conditions

International Nuclear Information System (INIS)

Sun, K.H.; Gonzalez-Santalo, J.M.; Tien, C.L.

1976-01-01

A model has been developed to calculate the heat transfer coefficients from the fuel rods to the steam-droplet mixture typical of Boiling Water Reactors under Emergency Core Cooling System (ECCS) operation conditions during a postulated loss-of-coolant accident. The model includes the heat transfer by convection to the vapor, the radiation from the surfaces to both the water droplets and the vapor, and the effects of droplet evaporation. The combined convection and radiation heat transfer coefficient can be evaluated with respect to the characteristic droplet size. Calculations of the heat transfer coefficient based on the droplet sizes obtained from the existing literature are consistent with those determined empirically from the Full-Length-Emergency-Cooling-Heat-Transfer (FLECHT) program. The present model can also be used to assess the effects of geometrical distortions (or deviations from nominal dimensions) on the heat transfer to the cooling medium in a rod bundle

New radiative transfer models for obscuring tori in active galaxies

NARCIS (Netherlands)

van Bemmel, IM; Dullemond, CP

Two-dimensional radiative transfer is employed to obtain the broad-band infrared spectrum of active galaxies. In the models we vary the geometry and size of the obscuring medium, the surface density, the opacity and the grain size distribution. Resulting spectral energy distributions are constructed

Preliminary study of human breast tissue using synchrotron radiation combining WAXS and SAXS techniques

International Nuclear Information System (INIS)

Conceicao, A.L.C.; Antoniassi, M.; Poletti, M.E.; Caldas, L.V.E.

2010-01-01

Using synchrotron radiation, we combined simultaneously wide angle X-ray scattering (WAXS) and small angle X-ray scattering (SAXS) techniques to obtain the scattering profiles of normal and neoplastic breast tissues samples at the momentum transfer range 6.28 nm -1 ≤Q(=4π.sin(θ/2)/λ)≤50.26 nm -1 and 0.15 nm -1 ≤Q≤1.90 nm -1 , respectively. The results obtained show considerable differences between the scattering profiles of these tissues. We verified that the combination of some parameters (ratio between glandular and adipose peak intensity and third-order axial peak intensity) extracted from scattering profiles can be used for identifying breast cancer.

Environmental monitoring with advanced data transfer and presentation techniques

International Nuclear Information System (INIS)

Toivonen, H.; Lahtinen, J.; Koivukoski, J.; Rantanen, H.; Haaslahti, J.

1995-01-01

In an emergency, the needs for information are overwhelming, as was shown during the Chernobyl accident in 1986. To improve environmental radiation monitoring and to make communication easy, the Finnish authorities launched an extensive development project in 1991. VTKK Group Ltd took over the software design. A brief description of system architecture, automatic data collection, manual input, mobile units, transfer of results and handling of alarms is given. 2 figs

Atmospheric radiative transfer in the UV: special emphasis on photolysis frequencies J(O1D) and J(NO2)

International Nuclear Information System (INIS)

Pfister, G.

2000-11-01

The amount of solar UV-radiation penetrating to the lower atmosphere and the Earth's surface is of special interest for biological as well as photochemical processes. The present work deals with theoretical (modeling) as well as experimental methods for investigating the interaction between solar radiation and the atmosphere. Two international model intercomparisons showed, that for cloudless conditions and provided that atmospheric and surface conditions are known, simulations agree to within about 5-10 % among one another as well as with measurements. Differences are strongly dependent on the wavelength and the solar zenith angle. The radiative transfer model was not only used for comprehensive sensitivity studies, but also for investigating and analyzing measurement methods as well as measured data. Two techniques, which were applied in frame of two aircraft campaigns, are dealt with in more detail in this work: filter radiometry and spectro radiometry. Analysis of the airborne measurements mainly concentrated on the influence of clouds on the radiation field in the atmosphere. (author)

Radiation Effects and Hardening Techniques for Spacecraft Microelectronics

Science.gov (United States)

Gambles, J. W.; Maki, G. K.

2002-01-01

The natural radiation from the Van Allen belts, solar flares, and cosmic rays found outside of the protection of the earth's atmosphere can produce deleterious effects on microelectronics used in space systems. Historically civil space agencies and the commercial satellite industry have been able to utilize components produced in special radiation hardened fabrication process foundries that were developed during the 1970s and 1980s under sponsorship of the Departments of Defense (DoD) and Energy (DoE). In the post--cold war world the DoD and DoE push to advance the rad--hard processes has waned. Today the available rad--hard components lag two-plus technology node generations behind state- of-the-art commercial technologies. As a result space craft designers face a large performance gap when trying to utilize available rad--hard components. Compounding the performance gap problems, rad--hard components are becoming increasingly harder to get. Faced with the economic pitfalls associated with low demand versus the ever increasing investment required for integrated circuit manufacturing equipment most sources of rad--hard parts have simply exited this market in recent years, leaving only two domestic US suppliers of digital rad--hard components. This paper summarizes the radiation induced mechanisms that can cause digital microelectronics to fail in space, techniques that can be applied to mitigate these failure mechanisms, and ground based testing used to validate radiation hardness/tolerance. The radiation hardening techniques can be broken down into two classes, Hardness By Process (HBP) and Hardness By Design (HBD). Fortunately many HBD techniques can be applied to commercial fabrication processes providing space craft designer with radiation tolerant Application Specific Integrated Circuits (ASICs) that can bridge the performance gap between the special HBP foundries and the commercial state-of-the-art performance.

Patient radiation exposure during different kyphoplasty techniques.

Science.gov (United States)

Panizza, Denis; Barbieri, Massimo; Parisoli, Francesco; Moro, Luca

2014-01-01

The scope of this study was to quantify patient radiation exposure during two different techniques of kyphoplasty (KP), which differ by a cement delivery method, in order to assess whether or not one of the two used methods can reduce the patient dose. Twenty patients were examined for this investigation. One X-ray fluoroscopy unit was used for localization, navigation and monitoring of cement delivery. The patient biometric data, the setting of the fluoroscope, the exposure time and the kerma-area product (KAP) were monitored in all the procedures for anteroposterior (AP) and lateral (LL) fluoroscopic projections in order to assess the range of radiation doses imparted to the patient. Theoretical entrance skin dose (ESD) and effective dose (E) were calculated from intraoperatively measured KAP. An average ET per procedure was 1.5±0.5 min for the manual injection technique (study A) and 1.4±0.4 min for the distance delivery technique (study B) in the AP plane, while 3.2±0.7 and 5.1±0.6 min in the lateral plane, respectively. ESD was estimated as an average of 0.10±0.06 Gy for study A and 0.13±0.13 Gy for study B in the AP or/and 0.59±0.46 and 1.05±0.36 Gy in the lateral view, respectively. The cumulative mean E was 1.9±1.0 mSv procedure(-1) for study A and 3.6±0.9 mSv procedure(-1) for study B. Patient radiation exposure and associated effective dose from KP may be considerable. The technique of distance cement delivery appears to be slower than the manual injection technique and it requires a more protracted fluoroscopic control in the lateral projection, so that this system entails a higher amount of dose to the patient.

Semi-analog Monte Carlo (SMC) method for time-dependent non-linear three-dimensional heterogeneous radiative transfer problems

International Nuclear Information System (INIS)

Yun, Sung Hwan

2004-02-01

Radiative transfer is a complex phenomenon in which radiation field interacts with material. This thermal radiative transfer phenomenon is composed of two equations which are the balance equation of photons and the material energy balance equation. The two equations involve non-linearity due to the temperature and that makes the radiative transfer equation more difficult to solve. During the last several years, there have been many efforts to solve the non-linear radiative transfer problems by Monte Carlo method. Among them, it is known that Semi-Analog Monte Carlo (SMC) method developed by Ahrens and Larsen is accurate regard-less of the time step size in low temperature region. But their works are limited to one-dimensional, low temperature problems. In this thesis, we suggest some method to remove their limitations in the SMC method and apply to the more realistic problems. An initially cold problem was solved over entire temperature region by using piecewise linear interpolation of the heat capacity, while heat capacity is still fitted as a cubic curve within the lowest temperature region. If we assume the heat capacity to be linear in each temperature region, the non-linearity still remains in the radiative transfer equations. We then introduce the first-order Taylor expansion to linearize the non-linear radiative transfer equations. During the linearization procedure, absorption-reemission phenomena may be described by a conventional reemission time sampling scheme which is similar to the repetitive sampling scheme in particle transport Monte Carlo method. But this scheme causes significant stochastic errors, which necessitates many histories. Thus, we present a new reemission time sampling scheme which reduces stochastic errors by storing the information of absorption times. The results of the comparison of the two schemes show that the new scheme has less stochastic errors. Therefore, the improved SMC method is able to solve more realistic problems with

Directional radiometry and radiative transfer: The convoluted path from centuries-old phenomenology to physical optics

International Nuclear Information System (INIS)

Mishchenko, Michael I.

2014-01-01

This Essay traces the centuries-long history of the phenomenological disciplines of directional radiometry and radiative transfer in turbid media, discusses their fundamental weaknesses, and outlines the convoluted process of their conversion into legitimate branches of physical optics. - Highlights: • History of phenomenological radiometry and radiative transfer is described. • Fundamental weaknesses of these disciplines are discussed. • The process of their conversion into legitimate branches of physical optics is summarized

Solving transient conduction and radiation heat transfer problems using the lattice Boltzmann method and the finite volume method

International Nuclear Information System (INIS)

Mishra, Subhash C.; Roy, Hillol K.

2007-01-01

The lattice Boltzmann method (LBM) was used to solve the energy equation of a transient conduction-radiation heat transfer problem. The finite volume method (FVM) was used to compute the radiative information. To study the compatibility of the LBM for the energy equation and the FVM for the radiative transfer equation, transient conduction and radiation heat transfer problems in 1-D planar and 2-D rectangular geometries were considered. In order to establish the suitability of the LBM, the energy equations of the two problems were also solved using the FVM of the computational fluid dynamics. The FVM used in the radiative heat transfer was employed to compute the radiative information required for the solution of the energy equation using the LBM or the FVM (of the CFD). To study the compatibility and suitability of the LBM for the solution of energy equation and the FVM for the radiative information, results were analyzed for the effects of various parameters such as the scattering albedo, the conduction-radiation parameter and the boundary emissivity. The results of the LBM-FVM combination were found to be in excellent agreement with the FVM-FVM combination. The number of iterations and CPU times in both the combinations were found comparable

CFD analysis of heat transfer performance of graphene based hybrid nanofluid in radiators

Science.gov (United States)

Bharadwaj, Bharath R.; Sanketh Mogeraya, K.; Manjunath, D. M.; Rao Ponangi, Babu; Rajendra Prasad, K. S.; Krishna, V.

2018-04-01

For Improved performance of an automobile engine, Cooling systems are one of the critical systems that need attention. With increased capacity to carry away large amounts of wasted heat, performance of an engine is increased. Current research on Nano-fluids suggests that they offer higher heat transfer rate compared to that of conventional coolants. Hence this project seeks to investigate the use of hybrid-nanofluids in radiators so as to increase its heat transfer performance. Carboxyl Graphene and Graphene Oxide based nanoparticles were selected due to the very high thermal conductivity of Graphene. System Analysis of the radiator was performed by considering a small part of the whole automobile radiator modelled using SEIMENS NX. CFD analysis was conducted using ANSYS FLUENT® for the nanofluid defined and the increase in effectiveness was compared to that of conventional coolants. Usage of such nanofluids for a fixed cooling requirement in the future can lead to significant downsizing of the radiator.

Comparison of Two Models for Radiative Heat Transfer in High Temperature Thermal Plasmas

Directory of Open Access Journals (Sweden)

Matthieu Melot

2011-01-01

Full Text Available Numerical simulation of the arc-flow interaction in high-voltage circuit breakers requires a radiation model capable of handling high-temperature participating thermal plasmas. The modeling of the radiative transfer plays a critical role in the overall accuracy of such CFD simulations. As a result of the increase of computational power, CPU intensive methods based on the radiative transfer equation, leading to more accurate results, are now becoming attractive alternatives to current approximate models. In this paper, the predictive capabilities of the finite volume method (RTE-FVM and the P1 model are investigated. A systematic comparison between these two models and analytical solutions are presented for a variety of relevant test cases. Two implementations of each approach are compared, and a critical evaluation is presented.

Vector Green's function algorithm for radiative transfer in plane-parallel atmosphere

Energy Technology Data Exchange (ETDEWEB)

Qin Yi [School of Physics, University of New South Wales (Australia)]. E-mail: yi.qin@csiro.au; Box, Michael A. [School of Physics, University of New South Wales (Australia)

2006-01-15

Green's function is a widely used approach for boundary value problems. In problems related to radiative transfer, Green's function has been found to be useful in land, ocean and atmosphere remote sensing. It is also a key element in higher order perturbation theory. This paper presents an explicit expression of the Green's function, in terms of the source and radiation field variables, for a plane-parallel atmosphere with either vacuum boundaries or a reflecting (BRDF) surface. Full polarization state is considered but the algorithm has been developed in such way that it can be easily reduced to solve scalar radiative transfer problems, which makes it possible to implement a single set of code for computing both the scalar and the vector Green's function.

Analysis of radiative heat transfer in the presence of obscurations

International Nuclear Information System (INIS)

Finkelstein, L.; Weissman, Y.

1981-05-01

Numerical simulation of radiative heat transfer problems in general axisymmetric geometry in the presence of an active gas is considered. Such simulation requires subdivision of the radiating surfaces into discrete elements, which are in the present case radiating rings. While the effect of a participating medium is easily taken into account by integration along the lines of vision between the surface elements, the calculation of the different obscurations poses the main difficulty. We have written a closed expression which formulates the problem exactly, and then developed a systematic and compact computational approach to the obscuration problem in complex configurations. The present procedure is particularly suited to computer calculations associated with engineering applications in the aircraft and furnace industries. (author)

Underground processing method for radiation-contaminated material and transferring method for buffer molding material

International Nuclear Information System (INIS)

Akasaka, Hidenari; Shimura, Satoshi; Asano, Eiichi; Yamagata, Junji; Ninomiya, Nobuo; Kawakami, Susumu.

1995-01-01

A bottomed molding material (buffer molding material) is formed into a bottomed cylindrical shape by solidifying, under pressure, powders such as of bentonite into a highly dense state by a cold isotropic pressing or the like, having a hole for accepting and containing a vessel for radiation-contaminated materials. The bottomed cylindrical molding material is loaded on a transferring vessel, and transferred to a position near the site for underground disposal. The bottomed cylindrical molding material having a upwarded containing hole is buried in the cave for disposal. The container for radiation-contaminated material is loaded and contained in the containing hole of the bottomed cylindrical molding material. A next container for radiation-contaminated materials is juxtaposed thereover. Then, a bottomed cylindrical molding material having a downwarded containing hole is covered to the container for the radiation-contaminated material in a state being protruded upwardly. The radiation-contaminated material is thus closed by a buffer material of the same material at the circumference thereof. (I.N.)

BACKWARD AND FORWARD MONTE CARLO METHOD IN POLARIZED RADIATIVE TRANSFER

Energy Technology Data Exchange (ETDEWEB)

Yong, Huang; Guo-Dong, Shi; Ke-Yong, Zhu, E-mail: huangy_zl@263.net [School of Aeronautical Science and Engineering, Beihang University, Beijing 100191 (China)

2016-03-20

In general, the Stocks vector cannot be calculated in reverse in the vector radiative transfer. This paper presents a novel backward and forward Monte Carlo simulation strategy to study the vector radiative transfer in the participated medium. A backward Monte Carlo process is used to calculate the ray trajectory and the endpoint of the ray. The Stocks vector is carried out by a forward Monte Carlo process. A one-dimensional graded index semi-transparent medium was presented as the physical model and the thermal emission consideration of polarization was studied in the medium. The solution process to non-scattering, isotropic scattering, and the anisotropic scattering medium, respectively, is discussed. The influence of the optical thickness and albedo on the Stocks vector are studied. The results show that the U, V-components of the apparent Stocks vector are very small, but the Q-component of the apparent Stocks vector is relatively larger, which cannot be ignored.

General Eulerian formulation of the comoving-frame equation of radiative transfer

International Nuclear Information System (INIS)

Riffert, H.

1986-01-01

For a wide range of problems in radiation hydrodynamics the motion of the matter is best described in an Eulerian coordinate system, and here a comoving-frame equation of radiation transfer in such fixed coordinates is derived, using the radiation quantities measured in the comoving frame. The choice of coordinates is arbitrary, and the equation is given explicitly for an arbitrary diagonal metric, correct to all orders in v/c. All comoving frame equations derived earlier are included as special cases. An example is given for the case of a spherically symmetric flow in a Schwarzschild metric. 9 references

Fast radiative transfer models for retrieval of cloud properties in the back-scattering region: application to DSCOVR-EPIC sensor

Science.gov (United States)

Molina Garcia, Victor; Sasi, Sruthy; Efremenko, Dmitry; Doicu, Adrian; Loyola, Diego

2017-04-01

In this work, the requirements for the retrieval of cloud properties in the back-scattering region are described, and their application to the measurements taken by the Earth Polychromatic Imaging Camera (EPIC) on board the Deep Space Climate Observatory (DSCOVR) is shown. Various radiative transfer models and their linearizations are implemented, and their advantages and issues are analyzed. As radiative transfer calculations in the back-scattering region are computationally time-consuming, several acceleration techniques are also studied. The radiative transfer models analyzed include the exact Discrete Ordinate method with Matrix Exponential (DOME), the Matrix Operator method with Matrix Exponential (MOME), and the approximate asymptotic and equivalent Lambertian cloud models. To reduce the computational cost of the line-by-line (LBL) calculations, the k-distribution method, the Principal Component Analysis (PCA) and a combination of the k-distribution method plus PCA are used. The linearized radiative transfer models for retrieval of cloud properties include the Linearized Discrete Ordinate method with Matrix Exponential (LDOME), the Linearized Matrix Operator method with Matrix Exponential (LMOME) and the Forward-Adjoint Discrete Ordinate method with Matrix Exponential (FADOME). These models were applied to the EPIC oxygen-A band absorption channel at 764 nm. It is shown that the approximate asymptotic and equivalent Lambertian cloud models give inaccurate results, so an offline processor for the retrieval of cloud properties in the back-scattering region requires the use of exact models such as DOME and MOME, which behave similarly. The combination of the k-distribution method plus PCA presents similar accuracy to the LBL calculations, but it is up to 360 times faster, and the relative errors for the computed radiances are less than 1.5% compared to the results when the exact phase function is used. Finally, the linearized models studied show similar behavior

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

Science.gov (United States)

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.

Fire Intensity Data for Validation of the Radiative Transfer Equation

Energy Technology Data Exchange (ETDEWEB)

Blanchat, Thomas K. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Jernigan, Dann A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

2016-01-01

A set of experiments and test data are outlined in this report that provides radiation intensity data for the validation of models for the radiative transfer equation. The experiments were performed with lightly-sooting liquid hydrocarbon fuels that yielded fully turbulent fires 2 m diameter). In addition, supplemental measurements of air flow and temperature, fuel temperature and burn rate, and flame surface emissive power, wall heat, and flame height and width provide a complete set of boundary condition data needed for validation of models used in fire simulations.

Analytical properties of the radiance in atmospheric radiative transfer theory

International Nuclear Information System (INIS)

Otto, Sebastian

2014-01-01

It is demonstrated mathematically strictly that state density functions, as the radiance (specific intensity), exist to describe certain state properties of transported photons on microscopic and the state of the radiation field on macroscopic scale, which have independent physical meanings. Analytical properties as boundedness, continuity, differentiability and integrability of these functions to describe the photon transport are discussed. It is shown that the density functions may be derived based on the assumption of photons as real particles of non-zero and finite size, independently of usual electrodynamics, and certain historically postulated functional relationships between them were proved, that is, these functions can be derived mathematically strictly and consistently within the framework of the theory of the phenomenological radiative transfer if one takes the theory seriously by really assuming photons as particles. In this sense these functions may be treated as fundamental physical quantities within the scope of this theory, if one considers the possibility of the existence of photons. -- Highlights: • Proof of existence of the radiance within the scope of the theory of atmospheric radiative transfer. • Proof of relations between the photon number and photon energy density function and the radiance. • Strictly mathematical derivation of the analytical properties of these state density functions

Hybrid finite volume/ finite element method for radiative heat transfer in graded index media

Science.gov (United States)

Zhang, L.; Zhao, J. M.; Liu, L. H.; Wang, S. Y.

2012-09-01

The rays propagate along curved path determined by the Fermat principle in the graded index medium. The radiative transfer equation in graded index medium (GRTE) contains two specific redistribution terms (with partial derivatives to the angular coordinates) accounting for the effect of the curved ray path. In this paper, the hybrid finite volume with finite element method (hybrid FVM/FEM) (P.J. Coelho, J. Quant. Spectrosc. Radiat. Transf., vol. 93, pp. 89-101, 2005) is extended to solve the radiative heat transfer in two-dimensional absorbing-emitting-scattering graded index media, in which the spatial discretization is carried out using a FVM, while the angular discretization is by a FEM. The FEM angular discretization is demonstrated to be preferable in dealing with the redistribution terms in the GRTE. Two stiff matrix assembly schemes of the angular FEM discretization, namely, the traditional assembly approach and a new spherical assembly approach (assembly on the unit sphere of the solid angular space), are discussed. The spherical assembly scheme is demonstrated to give better results than the traditional assembly approach. The predicted heat flux distributions and temperature distributions in radiative equilibrium are determined by the proposed method and compared with the results available in other references. The proposed hybrid FVM/FEM method can predict the radiative heat transfer in absorbing-emitting-scattering graded index medium with good accuracy.

Hybrid finite volume/ finite element method for radiative heat transfer in graded index media

International Nuclear Information System (INIS)

Zhang, L.; Zhao, J.M.; Liu, L.H.; Wang, S.Y.

2012-01-01

The rays propagate along curved path determined by the Fermat principle in the graded index medium. The radiative transfer equation in graded index medium (GRTE) contains two specific redistribution terms (with partial derivatives to the angular coordinates) accounting for the effect of the curved ray path. In this paper, the hybrid finite volume with finite element method (hybrid FVM/FEM) (P.J. Coelho, J. Quant. Spectrosc. Radiat. Transf., vol. 93, pp. 89-101, 2005) is extended to solve the radiative heat transfer in two-dimensional absorbing-emitting-scattering graded index media, in which the spatial discretization is carried out using a FVM, while the angular discretization is by a FEM. The FEM angular discretization is demonstrated to be preferable in dealing with the redistribution terms in the GRTE. Two stiff matrix assembly schemes of the angular FEM discretization, namely, the traditional assembly approach and a new spherical assembly approach (assembly on the unit sphere of the solid angular space), are discussed. The spherical assembly scheme is demonstrated to give better results than the traditional assembly approach. The predicted heat flux distributions and temperature distributions in radiative equilibrium are determined by the proposed method and compared with the results available in other references. The proposed hybrid FVM/FEM method can predict the radiative heat transfer in absorbing-emitting-scattering graded index medium with good accuracy.

Global existence of a generalized solution for the radiative transfer equations

International Nuclear Information System (INIS)

Golse, F.; Perthame, B.

1984-01-01

We prove global existence of a generalized solution of the radiative transfer equations, extending Mercier's result to the case of a layer with an initially cold area. Our Theorem relies on the results of Crandall and Ligett [fr

Characterizing convective heat transfer using infrared thermography and the heated-thin-foil technique

International Nuclear Information System (INIS)

Stafford, Jason; Walsh, Ed; Egan, Vanessa

2009-01-01

Convective heat transfer, due to axial flow fans impinging air onto a heated flat plate, is investigated with infrared thermography to assess the heated-thin-foil technique commonly used to quantify two-dimensional heat transfer performance. Flow conditions generating complex thermal profiles have been considered in the analysis to account for dominant sources of error in the technique. Uncertainties were obtained in the measured variables and the influences on the resultant heat transfer data are outlined. Correction methods to accurately account for secondary heat transfer mechanisms were developed and results show that as convective heat transfer coefficients and length scales decrease, the importance of accounting for errors increases. Combined with flow patterns that produce large temperature gradients, the influence of heat flow within the foil on the resultant heat transfer becomes significant. Substantial errors in the heat transfer coefficient are apparent by neglecting corrections to the measured data for the cases examined. Methods to account for these errors are presented here, and demonstrated to result in an accurate measurement of the local heat transfer map on the surface

Comparison of a new noncoplanar intensity-modulated radiation therapy technique for craniospinal irradiation with 3 coplanar techniques

DEFF Research Database (Denmark)

Hansen, Anders T; Lukacova, Slavka; Lassen-Ramshad, Yasmin A.

2015-01-01

When standard conformal x-ray technique for craniospinal irradiation is used, it is a challenge to achieve satisfactory dose coverage of the target including the area of the cribriform plate, while sparing organs at risk. We present a new intensity-modulated radiation therapy (IMRT), noncoplanar...... patient using the noncoplanar IMRT-based technique, a coplanar IMRT-based technique, and a coplanar volumetric-modulated arch therapy (VMAT) technique. Dosimetry data for all patients were compared with the corresponding data from the conventional treatment plans. The new noncoplanar IMRT technique...... substantially reduced the mean dose to organs at risk compared with the standard radiation technique. The 2 other coplanar techniques also reduced the mean dose to some of the critical organs. However, this reduction was not as substantial as the reduction obtained by the noncoplanar technique. Furthermore...

Application of PSA techniques to synchrotron radiation source facilities

International Nuclear Information System (INIS)

Sanyasi Rao, V.V.S.; Vinod, G.; Vaze, K.K.; Sarkar, P.K.

2011-01-01

Synchrotron radiation sources are increasingly being used in research and medical applications. Various instances of overexposure in these facilities have been reported in literature. These instances have lead to the investigation of the risks associated with them with a view to minimise the risks and thereby increasing the level of safety. In nuclear industry, Probabilistic Safety Assessment (PSA) methods are widely used to assess the risk from nuclear power plants. PSA presents a systematic methodology to evaluate the likelihood of various accident scenarios and their possible consequences using fault/event tree techniques. It is proposed to extend similar approach to analyse the risk associated with synchrotron radiation sources. First step for such an analysis is establishing the failure criteria, considering the regulatory stipulations on acceptable limits of dose due to ionization radiation from normal as well as beam loss scenarios. Some possible scenarios considered in this study are (1) excessive Bremsstrahlung in the ring due to loss of vacuum, (2) Target failure due to excessively focused beam (3) mis-directed/mis-steered beam (4) beam loss and sky shine. Hazard analysis needs to cover the beam transfer line, storage ring and experimental beam line areas. Various safety provisions are in place to minimize the hazards from these facilities such as access control interlock systems, radiation shielding for storage ring and beam lines and safety shutters (for beam lines). Experimental beam line area is the most vulnerable locations that need to be critically analysed. There are multiple beam lines, that have different safety provisions and consequences from postulated beam strikes will also be different and this increases the complexity of analysis. Similar studies conducted for such experimental facilities have identified that the radiation safety interlock system, used to control access to areas inside ring and the hutches of beamline facilities has an

A Novel Iterative Scheme for the Very Fast and Accurate Solution of Non-LTE Radiative Transfer Problems

Science.gov (United States)

Trujillo Bueno, J.; Fabiani Bendicho, P.

1995-12-01

Iterative schemes based on Gauss-Seidel (G-S) and optimal successive over-relaxation (SOR) iteration are shown to provide a dramatic increase in the speed with which non-LTE radiation transfer (RT) problems can be solved. The convergence rates of these new RT methods are identical to those of upper triangular nonlocal approximate operator splitting techniques, but the computing time per iteration and the memory requirements are similar to those of a local operator splitting method. In addition to these properties, both methods are particularly suitable for multidimensional geometry, since they neither require the actual construction of nonlocal approximate operators nor the application of any matrix inversion procedure. Compared with the currently used Jacobi technique, which is based on the optimal local approximate operator (see Olson, Auer, & Buchler 1986), the G-S method presented here is faster by a factor 2. It gives excellent smoothing of the high-frequency error components, which makes it the iterative scheme of choice for multigrid radiative transfer. This G-S method can also be suitably combined with standard acceleration techniques to achieve even higher performance. Although the convergence rate of the optimal SOR scheme developed here for solving non-LTE RT problems is much higher than G-S, the computing time per iteration is also minimal, i.e., virtually identical to that of a local operator splitting method. While the conventional optimal local operator scheme provides the converged solution after a total CPU time (measured in arbitrary units) approximately equal to the number n of points per decade of optical depth, the time needed by this new method based on the optimal SOR iterations is only √n/2√2. This method is competitive with those that result from combining the above-mentioned Jacobi and G-S schemes with the best acceleration techniques. Contrary to what happens with the local operator splitting strategy currently in use, these novel

Parallel-plate submicron gap formed by micromachined low-density pillars for near-field radiative heat transfer

International Nuclear Information System (INIS)

Ito, Kota; Miura, Atsushi; Iizuka, Hideo; Toshiyoshi, Hiroshi

2015-01-01

Near-field radiative heat transfer has been a subject of great interest due to the applicability to thermal management and energy conversion. In this letter, a submicron gap between a pair of diced fused quartz substrates is formed by using micromachined low-density pillars to obtain both the parallelism and small parasitic heat conduction. The gap uniformity is validated by the optical interferometry at four corners of the substrates. The heat flux across the gap is measured in a steady-state and is no greater than twice of theoretically predicted radiative heat flux, which indicates that the parasitic heat conduction is suppressed to the level of the radiative heat transfer or less. The heat conduction through the pillars is modeled, and it is found to be limited by the thermal contact resistance between the pillar top and the opposing substrate surface. The methodology to form and evaluate the gap promotes the near-field radiative heat transfer to various applications such as thermal rectification, thermal modulation, and thermophotovoltaics

Parallel-plate submicron gap formed by micromachined low-density pillars for near-field radiative heat transfer

Energy Technology Data Exchange (ETDEWEB)

Ito, Kota, E-mail: kotaito@mosk.tytlabs.co.jp [Toyota Central Research and Development Laboratories, Nagakute, Aichi 480-1192 (Japan); Research Center for Advanced Science and Technology (RCAST), The University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8904 (Japan); Miura, Atsushi; Iizuka, Hideo [Toyota Central Research and Development Laboratories, Nagakute, Aichi 480-1192 (Japan); Toshiyoshi, Hiroshi [Research Center for Advanced Science and Technology (RCAST), The University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8904 (Japan)

2015-02-23

Near-field radiative heat transfer has been a subject of great interest due to the applicability to thermal management and energy conversion. In this letter, a submicron gap between a pair of diced fused quartz substrates is formed by using micromachined low-density pillars to obtain both the parallelism and small parasitic heat conduction. The gap uniformity is validated by the optical interferometry at four corners of the substrates. The heat flux across the gap is measured in a steady-state and is no greater than twice of theoretically predicted radiative heat flux, which indicates that the parasitic heat conduction is suppressed to the level of the radiative heat transfer or less. The heat conduction through the pillars is modeled, and it is found to be limited by the thermal contact resistance between the pillar top and the opposing substrate surface. The methodology to form and evaluate the gap promotes the near-field radiative heat transfer to various applications such as thermal rectification, thermal modulation, and thermophotovoltaics.

Radiative heat transfer in honeycomb structures-New simple analytical and numerical approaches

International Nuclear Information System (INIS)

Baillis, D; Coquard, R; Randrianalisoa, J

2012-01-01

Porous Honeycomb Structures present the interest of combining, at the same time, high thermal insulating properties, low density and sufficient mechanical resistance. However, their thermal properties remain relatively unexplored. The aim of this study is the modelling of the combined heat transfer and especially radiative heat transfer through this type of anisotropic porous material. The equivalent radiative properties of the material are determined using ray-tracing procedures inside the honeycomb porous structure. From computational ray-tracing results, simple new analytical relations have been deduced. These useful analytical relations permit to determine radiative properties such as extinction, absorption and scattering coefficients and phase function functions of cell dimensions and optical properties of cell walls. The radiative properties of honeycomb material strongly depend on the direction of propagation. From the radiative properties computed, we have estimated the radiative heat flux passing through slabs of honeycomb core materials submitted to a 1-D temperature difference between a hot and a cold plate. We have compared numerical results obtained from Discrete Ordinate Method with analytical results obtained from Rosseland-Deissler approximation. This approximation is usually used in the case of isotropic materials. We have extended it to anisotropic honeycomb materials. Indeed a mean over incident directions of Rosseland extinction coefficient is proposed. Results tend to show that Rosseland-Deissler extended approximation can be used as a first approximation. Deviation on radiative conductivity obtained from Rosseland-Deissler approximation and from the Discrete Ordinated Method are lower than 6.7% for all the cases studied.

New type of radiation instrumentation system

International Nuclear Information System (INIS)

Matsuo, Keichi; Takaoka, Akira; Uranaka, Yasuo

2000-01-01

The Mitsubishi Electric Co., Ltd. developed a radiation instrumentation system introduced some recent techniques such as computation technique, network technique and so on into conventional radiation detection aiming at general market except power generation company. In a conventional system, a detector and an operation processing board was placed at a field and center, respectively, and a feeble pulse signal from the detector was transferred to the operation processing board. Then, on establishment of cables, detectors and operation processing board, it is essential to carry out engineering planning and field engineering conceiving on noise countermeasure. Noise resistance of the new type of radiation instrumentation system, not by adding operation processing function and network interface function into a detector unit in a field to transfer feeble signal, but by transferring testing result as a digital signal. And, noise removing function capable of selectively passing only signal pulse waveform from the detector to judge its signal waveform was also added to a detector unit in the field, to carry out a thoroughly removing noise. In addition, by connecting between each apparatus placed at the field with a network a system capable of reducing some cable engineering could be executed. Here were introduced on abstract of this new type of radiation instrumentation system and on noise removing function of its characteristics. (G.K.)

Radiative Transfer Reconsidered as a Quantum Kinetic Theory

Indian Academy of Sciences (India)

Radiative transfer—quantum kinetic theory—anomalous dispersion. 1. ... able for the elaboration of transport codes (e.g. based on the Monte-Carlo technique ... this function is not a true probability density function but rather a quasiprobability.

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

International Nuclear Information System (INIS)

Sun, Wenjun; Jiang, Song; Xu, Kun

2015-01-01

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 transport 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

Multidimensional radiative transfer with multilevel atoms. II. The non-linear multigrid method.

Science.gov (United States)

Fabiani Bendicho, P.; Trujillo Bueno, J.; Auer, L.

1997-08-01

A new iterative method for solving non-LTE multilevel radiative transfer (RT) problems in 1D, 2D or 3D geometries is presented. The scheme obtains the self-consistent solution of the kinetic and RT equations at the cost of only a few (iteration (Brandt, 1977, Math. Comp. 31, 333; Hackbush, 1985, Multi-Grid Methods and Applications, springer-Verlag, Berlin), an efficient multilevel RT scheme based on Gauss-Seidel iterations (cf. Trujillo Bueno & Fabiani Bendicho, 1995ApJ...455..646T), and accurate short-characteristics formal solution techniques. By combining a valid stopping criterion with a nested-grid strategy a converged solution with the desired true error is automatically guaranteed. Contrary to the current operator splitting methods the very high convergence speed of the new RT method does not deteriorate when the grid spatial resolution is increased. With this non-linear multigrid method non-LTE problems discretized on N grid points are solved in O(N) operations. The nested multigrid RT method presented here is, thus, particularly attractive in complicated multilevel transfer problems where small grid-sizes are required. The properties of the method are analyzed both analytically and with illustrative multilevel calculations for Ca II in 1D and 2D schematic model atmospheres.

The weighted-sum-of-gray-gases model for arbitrary solution methods in radiative transfer

International Nuclear Information System (INIS)

Modest, M.F.

1991-01-01

In this paper the weighted-sum-of-gray-gases approach for radiative transfer in non-gray participating media, first developed by Hottel in the context of the zonal method, has been shown to be applicable to the general radiative equation of transfer. Within the limits of the weighted-sum-of-gray-gases model (non-scattering media within a black-walled enclosure) any non-gray radiation problem can be solved by any desired solution method after replacing the medium by an equivalent small number of gray media with constant absorption coefficients. Some examples are presented for isothermal media and media at radiative equilibrium, using the exact integral equations as well as the popular P-1 approximation of the equivalent gray media solution. The results demonstrate the equivalency of the method with the quadrature of spectral results, as well as the tremendous computer times savings (by a minimum of 95%) which are achieved

Effect of thermal radiation and suction on convective heat transfer of nanofluid along a wedge in the presence of heat generation/absorption

Energy Technology Data Exchange (ETDEWEB)

Kasmani, Ruhaila Md; Bhuvaneswari, M. [Centre for Foundation Studies in Science, University of Malaya, 50603 Kuala Lumpur (Malaysia); Sivasankaran, S.; Siri, Zailan [Institute of Mathematical Science, University of Malaya, 50603 Kuala Lumpur (Malaysia)

2015-10-22

An analysis is presented to find the effects of thermal radiation and heat generation/absorption on convection heat transfer of nanofluid past a wedge in the presence of wall suction. The governing partial differential equations are transformed into a system of ordinary differential equations using similarity transformation. The resulting system is solved numerically using a fourth-order Runge–Kutta method with shooting technique. Numerical computations are carried out for different values of dimensionless parameters to predict the effects of wedge angle, thermophoresis, Brownian motion, heat generation/absorption, thermal radiation and suction. It is found that the temperature increases significantly when the value of the heat generation/absorption parameter increases. But the opposite observation is found for the effect of thermal radiation.

Radiation Heat Transfer Effect on Thermal Sizing of Air-Cooling Heat Exchanger of Emergency Cooldown Tank

Energy Technology Data Exchange (ETDEWEB)

Moon, Joo Hyung; Kim, Young In; Kim, Keung Koo [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Kim, Myoung Jun; Lee, Hee Joon [School of Mechanical Eng., Kookmin University, Seoul (Korea, Republic of)

2014-10-15

An attempt has begun to extend the life time of emergency cooldown tank (ECT) by Korea Atomic Energy Research Institute (KAERI) researchers. Moon et al. recently reported a basic concept upon how to keep the ECT in operation beyond 72 hours after an accident occurs without any active corrective actions for the postulated design basis accidents. When the SMART (System-integrated Modular Advanced Reac-Tor) received its Standard Design Approval (SDA) for the first time in the world, hybrid safety systems are applied. However, the passive safety systems of SMART are being enforced in response to the public concern for much safer reactors since the Fukushima accident occurred. The ECT is a major component of a passive residual heat removal system (PRHRS), which is one of the most important systems to enhance the safety of SMART. It is being developed in a SMART safety enhancement project to contain enough cooling water to remove a sensible heat and a decay heat from reactor core for 72 hours since an accident occurs. Moon et al. offered to install another heat exchanger above the ECT and to recirculate an evaporated steam into water, which enables the ECT to be in operation, theoretically, indefinitely. An investigation was made to determine how long and how many tubes were required to meet the purpose of the study. In their calculation, however, a radiation heat transfer effect was neglected. The present study is to consider the radiation heat transfer for the design of air-cooling heat exchanger. Radiation heat transfer is normally ignored in many situations, but this is not the case for the present study. Kim et al. conducted thermal sizing of scaled-down ECT heat exchanger, which will be used to validate experimentally the basic concept of the present study. Their calculation is also examined to see if a radiation heat transfer effect was taken into consideration. The thermal sizing of an air-cooling heat exchanger was conducted including radiation heat transfer

The progress of molecular biology in radiation research

International Nuclear Information System (INIS)

Wei Kang

1989-01-01

The recent progress in application of molecular biology techniques in the study of radiation biology is reviewed. The three sections are as follows: (1) the study of DNA damage on molecular level, (2) the molecular mechanism of radiation cell genetics, including chromosome abberation and cell mutation, (3) the study on DNA repair gene with DNA mediated gene transfer techniques

Prevention of radiation induced xerostomia by surgical transfer of submandibular salivary gland into the submental space

International Nuclear Information System (INIS)

Jha, Naresh; Seikaly, Hadi; Harris, Jeff; Williams, David; Liu, Richard; McGaw, Timothy; Hofmann, Henry; Robinson, Don; Hanson, John; Barnaby, Pam

2003-01-01

Background and purpose: Xerostomia is a significant morbidity of radiation treatment in the management of head and neck cancers. We hypothesized that the surgical transfer of one submandibular salivary gland to the submental space, where it can be shielded from radiation treatment (XRT), would prevent xerostomia. Materials and methods: We conducted a prospective Phase II clinical trial and the patients were followed clinically with salivary flow studies and the University of Washington Quality of Life questionnaire. Results: We report the results on 76 evaluable patients. The salivary gland transfer was done in 60 patients. Nine patients (of 60) did not have postoperative XRT and in eight patients (of 60) the transferred gland was not shielded from XRT due to proximity of disease. The median follow up is 14 months. Of the 43 patients with the salivary gland transfer and post-operative XRT with protection of the transferred gland, 81% have none or minimal xerostomia, and 19% developed moderate to severe xerostomia. Three patients (6.9%) developed local recurrence, five patients (11.6%) developed distant metastases and five patients (11.6%) have died. There were no complications attributed to the surgical procedure. Conclusion: Surgical transfer of a submandibular salivary gland to the submental space preserves its function and prevents the development of radiation induced xerostomia

Sublimation-assisted graphene transfer technique based on small polyaromatic hydrocarbons

Science.gov (United States)

Chen, Mingguang; Stekovic, Dejan; Li, Wangxiang; Arkook, Bassim; Haddon, Robert C.; Bekyarova, Elena

2017-06-01

Advances in the chemical vapor deposition (CVD) growth of graphene have made this material a very attractive candidate for a number of applications including transparent conductors, electronics, optoeletronics, biomedical devices and energy storage. The CVD method requires transfer of graphene on a desired substrate and this is most commonly accomplished with polymers. The removal of polymer carriers is achieved with organic solvents or thermal treatment which makes this approach inappropriate for application to plastic thin films such as polyethylene terephthalate substrates. An ultraclean graphene transfer method under mild conditions is highly desired. In this article, we report a naphthalene-assisted graphene transfer technique which provides a reliable route to residue-free transfer of graphene to both hard and flexible substrates. The quality of the transferred graphene was characterized with atomic force microscopy, scanning electron microscopy, and Raman spectroscopy. Field effect transistors, based on the naphthalene-transfered graphene, were fabricated and characterized. This work has the potential to broaden the applications of CVD graphene in fields where ultraclean graphene and mild graphene transfer conditions are required.

Linear energy transfer (LET) effects in the radiation-induced inactivation of papain

International Nuclear Information System (INIS)

Bisby, R.H.; Cundall, R.B.; Sims, H.E.; Burns, W.G.

1977-01-01

The inactivation of dilute aqueous solutions of papain by radiations of varying linear energy transfer has been studied in N 2 , N 2 0 and O 2 -saturated solutions. The results obtained with low LET radiation are very similar to those previously reported by Lin et al (Radiation Res.;62:438(1975)). The additional data obtained at higher LET, when radical product yields are reduced and the yield of hydrogen peroxide is increased, show that the hydrogen atom is more important in the inactivation of papain than previously considered. (author)

Arcmancer: Geodesics and polarized radiative transfer library

Science.gov (United States)

Pihajoki, Pauli; Mannerkoski, Matias; Nättilä, Joonas; Johansson, Peter H.

2018-05-01

Arcmancer computes geodesics and performs polarized radiative transfer in user-specified spacetimes. The library supports Riemannian and semi-Riemannian spaces of any dimension and metric; it also supports multiple simultaneous coordinate charts, embedded geometric shapes, local coordinate systems, and automatic parallel propagation. Arcmancer can be used to solve various problems in numerical geometry, such as solving the curve equation of motion using adaptive integration with configurable tolerances and differential equations along precomputed curves. It also provides support for curves with an arbitrary acceleration term and generic tools for generating ray initial conditions and performing parallel computation over the image, among other tools.

Numerical analysis of the effects of radiation heat transfer and ionization energy loss on the cavitation Bubble's dynamics

International Nuclear Information System (INIS)

Mahdi, M.; Ebrahimi, R.; Shams, M.

2011-01-01

A numerical scheme for simulating the acoustic and hydrodynamic cavitation was developed. Bubble instantaneous radius was obtained using Gilmore equation which considered the compressibility of the liquid. A uniform temperature was assumed for the inside gas during the collapse. Radiation heat transfer inside the bubble and the heat conduction to the bubble was considered. The numerical code was validated with the experimental data and a good correspondence was observed. The dynamics of hydrofoil cavitation bubble were also investigated. It was concluded that the thermal radiation heat transfer rate strongly depended on the cavitation number, initial bubble radius and hydrofoil angle of attack. -- Highlights: → Heat transfer and ionization energy losses were analyzed in the cavitation bubble. → Radiation of hydrodynamic bubble was approximately equal to the black body. → Radiation heat transfer did not affect the bubble dynamic. → Conduction decreased the bubble pressure and increased the bubble temperature. → Ionization decreased the temperature and increased the pressure in the bubble.

Cost-effective computational method for radiation heat transfer in semi-crystalline polymers

Science.gov (United States)

Boztepe, Sinan; Gilblas, Rémi; de Almeida, Olivier; Le Maoult, Yannick; Schmidt, Fabrice

2018-05-01

This paper introduces a cost-effective numerical model for infrared (IR) heating of semi-crystalline polymers. For the numerical and experimental studies presented here semi-crystalline polyethylene (PE) was used. The optical properties of PE were experimentally analyzed under varying temperature and the obtained results were used as input in the numerical studies. The model was built based on optically homogeneous medium assumption whereas the strong variation in the thermo-optical properties of semi-crystalline PE under heating was taken into account. Thus, the change in the amount radiative energy absorbed by the PE medium was introduced in the model induced by its temperature-dependent thermo-optical properties. The computational study was carried out considering an iterative closed-loop computation, where the absorbed radiation was computed using an in-house developed radiation heat transfer algorithm -RAYHEAT- and the computed results was transferred into the commercial software -COMSOL Multiphysics- for solving transient heat transfer problem to predict temperature field. The predicted temperature field was used to iterate the thermo-optical properties of PE that varies under heating. In order to analyze the accuracy of the numerical model experimental analyses were carried out performing IR-thermographic measurements during the heating of the PE plate. The applicability of the model in terms of computational cost, number of numerical input and accuracy was highlighted.

Review of the afterloading techniques in gynecologic radiation therapy

International Nuclear Information System (INIS)

Rotte, K.

1975-01-01

A review of clinically used afterloading techniques - remote controlled and manually operated ones - is given by tables. The advantages of afterloading techniques are discussed with regard to radiation protection as well as to the therapy of gynecologic carcinomas. (orig.) [de

Patient radiation exposure during different kyphoplasty techniques

International Nuclear Information System (INIS)

Panizza, D.; Barbieri, M.; Parisoli, F.; Moro, L.

2014-01-01

The scope of this study was to quantify patient radiation exposure during two different techniques of kyphoplasty (KP), which differ by a cement delivery method, in order to assess whether or not one of the two used methods can reduce the patient dose. Twenty patients were examined for this investigation. One X-ray fluoroscopy unit was used for localization, navigation and monitoring of cement delivery. The patient bio-metric data, the setting of the fluoroscope, the exposure time and the kerma-area product (KAP) were monitored in all the procedures for anteroposterior (AP) and lateral (LL) fluoroscopic projections in order to assess the range of radiation doses imparted to the patient. Theoretical entrance skin dose (ESD) and effective dose (E) were calculated from intraoperatively measured KAP. An average ET per procedure was 1.5±0.5 min for the manual injection technique (study A) and 1.4±0.4 min for the distance delivery technique (study B) in the AP plane, while 3.2±0.7 and 5.1±0.6 min in the lateral plane, respectively. ESD was estimated as an average of 0.10±0.06 Gy for study A and 0.13±0.13 Gy for study B in the AP or/and 0.59±0.46 and 1.05±0.36 Gy in the lateral view, respectively. The cumulative mean E was 1.9±1.0 mSv procedure -1 for study A and 3.6±0.9 mSv procedure -1 for study B. Patient radiation exposure and associated effective dose from KP may be considerable. The technique of distance cement delivery appears to be slower than the manual injection technique and it requires a more protracted fluoroscopic control in the lateral projection, so that this system entails a higher amount of dose to the patient. (authors)

Radiation hardening techniques for rare-earth based optical fibers and amplifiers

International Nuclear Information System (INIS)

Girard, Sylvain; Marcandella, Claude; Vivona, Marilena; Prudenzano, Luciano Mescia F.; Laurent, Arnaud; Robin, Thierry; Cadier, Benoit; Pinsard, Emmanuel; Ouerdane, Youcef; Boukenter, Aziz; Cannas, Marco; Boscaino, Roberto

2012-01-01

Er/Yb doped fibers and amplifiers have been shown to be very radiation sensitive, limiting their integration in space. We present an approach including successive hardening techniques to enhance their radiation tolerance. The efficiency of our approach is demonstrated by comparing the radiation responses of optical amplifiers made with same lengths of different rare-earth doped fibers and exposed to gamma-rays. Previous studies indicated that such amplifiers suffered significant degradation for doses exceeding 10 krad. Applying our techniques significantly enhances the amplifier radiation resistance, resulting in a very limited degradation up to 50 krad. Our optimization techniques concern the fiber composition, some possible pre-treatments and the interest of simulation tools used to harden by design the amplifiers. We showed that adding cerium inside the fiber phospho-silicate-based core strongly decreases the fiber radiation sensitivity compared to the standard fiber. For both fibers, a pre-treatment with hydrogen permits to enhance again the fiber resistance. Furthermore, simulations tools can also be used to improve the tolerance of the fiber amplifier by helping identifying the best amplifier configuration for operation in the radiative environment. (authors)

Ionizing and ultraviolet radiation enhances the efficiency of DNA mediated gene transfer in vitro

International Nuclear Information System (INIS)

Perez, C.F.

1984-08-01

The enhancement effects of ionizing and non-ionizing radiation on the efficiency of DNA mediated gene transfer were studied. Confluent Rat-2 cells were transfected with purified SV40 viral DNA, irradiated with either X-rays or ultraviolet, trypsinized, plated, and assayed for the formation of foci on Rat-2 monolayers. Both ionizing and ultraviolet radiation enhanced the frequency of A-gene transformants/survivor compared to unirradiated transfected cells. These enhancements were non-linear and dose dependent. A recombinant plasmid, pOT-TK5, was constructed that contained the SV40 virus A-gene and the Herpes Simplex virus (HSV) thymidine kinase (TK) gene. Confluent Rat-2 cells transfected with pOT-TK5 DNA and then immediately irradiated with either X-rays or 330 MeV/amu argon particles at the Berkeley Bevalac showed a higher frequency of HAT + colonies/survivor than unirradiated transfected cells. Rat-2 cells transfected with the plasmid, pTK2, containing only the HSV TK-gene were enhanced for TK-transformation by both X-rays and ultraviolet radiation. The results demonstrate that radiation enhancement of the efficiency of DNA mediated gene transfer is not explained by increased nuclear uptake of the transfected DNA. Radiation increases the competence of the transfected cell population for genetic transformation. Three models for this increased competence are presented. The targeted integration model, the inducible recombination model, the partition model, and the utilization of DNA mediated gene transfer for DNA repair studies are discussed. 465 references

Ionizing and ultraviolet radiation enhances the efficiency of DNA mediated gene transfer in vitro

Energy Technology Data Exchange (ETDEWEB)

Perez, C.F.

1984-08-01

The enhancement effects of ionizing and non-ionizing radiation on the efficiency of DNA mediated gene transfer were studied. Confluent Rat-2 cells were transfected with purified SV40 viral DNA, irradiated with either X-rays or ultraviolet, trypsinized, plated, and assayed for the formation of foci on Rat-2 monolayers. Both ionizing and ultraviolet radiation enhanced the frequency of A-gene transformants/survivor compared to unirradiated transfected cells. These enhancements were non-linear and dose dependent. A recombinant plasmid, pOT-TK5, was constructed that contained the SV40 virus A-gene and the Herpes Simplex virus (HSV) thymidine kinase (TK) gene. Confluent Rat-2 cells transfected with pOT-TK5 DNA and then immediately irradiated with either X-rays or 330 MeV/amu argon particles at the Berkeley Bevalac showed a higher frequency of HAT/sup +/ colonies/survivor than unirradiated transfected cells. Rat-2 cells transfected with the plasmid, pTK2, containing only the HSV TK-gene were enhanced for TK-transformation by both X-rays and ultraviolet radiation. The results demonstrate that radiation enhancement of the efficiency of DNA mediated gene transfer is not explained by increased nuclear uptake of the transfected DNA. Radiation increases the competence of the transfected cell population for genetic transformation. Three models for this increased competence are presented. The targeted integration model, the inducible recombination model, the partition model, and the utilization of DNA mediated gene transfer for DNA repair studies are discussed. 465 references.

Pomarning-eddington approximation for time-dependent radiation transfer in finite slab media

International Nuclear Information System (INIS)

El-Wakil, S.A.; Degheidy, A.R.; Sallah, M.

2005-01-01

The time-dependent monoenergetic radiation transfer equation with linear anisotropic scattering is proposed. Pomraning-Eddington approximation is used to calculate the radiation intensity in finite plane-parallel media. Numerical results are done for the isotropic media. Shielding calculations are shown for reflectivity and transmissivity at different times. The medium is assumed to have specular-reflecting boundaries. Two different weight functions are introduced to force the boundary conditions to be fulfilled

Radiation transfer effects on the spectra of laser-generated plasmas

Czech Academy of Sciences Publication Activity Database

Renner, Oldřich; Kerr, F.M.; Wolfrum, E.; Hawreliak, J.; Chambers, D.; Rose, S. J.; Wark, J. S.; Scott, H.A.; Patel, P.

2006-01-01

Roč. 96, č. 18 (2006), 185002/1-185002/4 ISSN 0031-9007 R&D Projects: GA MŠk(CZ) LC528 Institutional research plan: CEZ:AV0Z10100523 Keywords : laser-produced plasma * spectral line shapes * plasma modeling * radiative transfer effects Subject RIV: BH - Optics, Masers, Lasers Impact factor: 7.072, year: 2006

Free convection effects and radiative heat transfer in MHD Stokes ...

Indian Academy of Sciences (India)

The present note deals with the effects of radiative heat transfer and free convection in MHD for a flow of an electrically conducting, incompressible, dusty viscous fluid past an impulsively started vertical non-conducting plate, under the influence of transversely applied magnetic field. The heat due to viscous dissipation and ...

Thermal radiation influence on MHD flow of a rotating fluid with heat transfer through EFGM solutions

Science.gov (United States)

Prasad, D. V. V. Krishna; Chaitanya, G. S. Krishna; Raju, R. Srinivasa

2018-05-01

The aim of this research work is to find the EFGM solutions of the unsteady magnetohydromagnetic natural convection heat transfer flow of a rotating, incompressible, viscous, Boussinesq fluid is presented in this study in the presence of radiative heat transfer. The Rosseland approximation for an optically thick fluid is invoked to describe the radiative flux. Numerical results obtained show that a decrease in the temperature boundary layer occurs when the Prandtl number and the radiation parameter are increased and the flow velocity approaches steady state as the time parameter t is increased. These findings are in quantitative agreement with earlier reported studies.

Study on production of useful metabolites by development of advanced cell culture techniques using radiation

Energy Technology Data Exchange (ETDEWEB)

Chung, Byung Yeoup; Kim, Jinhong; Lee, Seung Sik; Bai, Hyounwoo; An, Byung Chull; Lee, Eun Mi; Lee, Jae Taek; Kim, Mi Ja

2010-12-15

The purpose of this project is improvement of investigation, materialization and evaluation techniques on effectiveness for functional natural compounds throughout development of tissue/cell culture techniques for mass production of useful metabolites using radiation. Research scope includes Development of a technique for radiation tissue and cell culture, Database construction for radiation response in plants and radiation effects, Construction of general-purpose national based techniques of cell culture technique using radiation. Main results are as follow: Isolation and identification of radiation induced basI gene; Determination of stresses sensitivities by transformating basI gene into arabidopsis; Isolation and identification of radiation induced chaperon proteins (PaAhpC and yPrxII) from Pseudomonas and yeast, and structural and functional analysis of the proteins; Determination of oxidative and heat resistance by transformating PaAhpC; Isolation and identification of maysin and its derivatives from centipedgrass; Investigation of enhancement technique for improving maysin and its derivatives production using radiation; Investigation of removing undesirable color in maysin and its derivatives using radiation; Determination of the effect of radiation on physiological functions of centipedgrass extracts; Identification of H{sub 2}O{sub 2} removing enzyme in radiation irradiated plant (Spinach); Determination of the effects of centipedgrass extracts on anti-obesity and anti-cancer activities.

Study on production of useful metabolites by development of advanced cell culture techniques using radiation

International Nuclear Information System (INIS)

Chung, Byung Yeoup; Kim, Jinhong; Lee, Seung Sik; Bai, Hyounwoo; An, Byung Chull; Lee, Eun Mi; Lee, Jae Taek; Kim, Mi Ja

2010-12-01

The purpose of this project is improvement of investigation, materialization and evaluation techniques on effectiveness for functional natural compounds throughout development of tissue/cell culture techniques for mass production of useful metabolites using radiation. Research scope includes Development of a technique for radiation tissue and cell culture, Database construction for radiation response in plants and radiation effects, Construction of general-purpose national based techniques of cell culture technique using radiation. Main results are as follow: Isolation and identification of radiation induced basI gene; Determination of stresses sensitivities by transformating basI gene into arabidopsis; Isolation and identification of radiation induced chaperon proteins (PaAhpC and yPrxII) from Pseudomonas and yeast, and structural and functional analysis of the proteins; Determination of oxidative and heat resistance by transformating PaAhpC; Isolation and identification of maysin and its derivatives from centipedgrass; Investigation of enhancement technique for improving maysin and its derivatives production using radiation; Investigation of removing undesirable color in maysin and its derivatives using radiation; Determination of the effect of radiation on physiological functions of centipedgrass extracts; Identification of H 2 O 2 removing enzyme in radiation irradiated plant (Spinach); Determination of the effects of centipedgrass extracts on anti-obesity and anti-cancer activities

A research program on radiative transfer model development in support of the ARM program

International Nuclear Information System (INIS)

Clough, S.A.

1993-01-01

The objective of this research effort is to develop radiative transfer models that are consistent with ARM spectral radiance measurements for clear and cloudy atmospheres. Our approach is to develop the model physics and related databases with a line-by-line model in the context of available spectral radiance measurements. The line-by-line model then functions as an intermediate standard to both develop and validate rapid radiative transfer models appropriate to GCM applications. A preprint of an extended abstract for the 1994 AMS volume describing a Quality Measurement Experiment using the ARM spectral data is included as an attachment

The Palaeoclimate and Terrestrial Exoplanet Radiative Transfer Model Intercomparison Project (PALAEOTRIP: experimental design and protocols

Directory of Open Access Journals (Sweden)

C. Goldblatt

2017-11-01

Full Text Available Accurate radiative transfer calculation is fundamental to all climate modelling. For deep palaeoclimate, and increasingly terrestrial exoplanet climate science, this brings both the joy and the challenge of exotic atmospheric compositions. The challenge here is that most standard radiation codes for climate modelling have been developed for modern atmospheric conditions and may perform poorly away from these. The palaeoclimate or exoclimate modeller must either rely on these or use bespoke radiation codes, and in both cases rely on either blind faith or ad hoc testing of the code. In this paper, we describe the protocols for the Palaeoclimate and Terrestrial Exoplanet Radiative Transfer Model Intercomparison Project (PALAEOTRIP to systematically address this. This will compare as many radiation codes used for palaeoclimate or exoplanets as possible, with the aim of identifying the ranges of far-from-modern atmospheric compositions in which the codes perform well. This paper describes the experimental protocol and invites community participation in the project through 2017–2018.

Repeated CT scans in trauma transfers: An analysis of indications, radiation dose exposure, and costs

International Nuclear Information System (INIS)

Hinzpeter, Ricarda; Sprengel, Kai; Wanner, Guido A.; Mildenberger, Peter; Alkadhi, Hatem

2017-01-01

Highlights: • Repetition of CT in trauma patients occurs relatively often. • Repetition of CT is mainly caused by inadequate image data transfer. • Potentially preventable CT examinations add radiation dose to patients. • Repeated CT is associated with excess costs to the health care system. - Abstract: Objectives: To identify the number of CT scans repeated in acute trauma patients receiving imaging before being referred to a trauma center, to define indications, and to assess radiation doses and costs of repeated CT. Methods: This retrospective study included all adult trauma patients transferred from other hospitals to a Level-I trauma center during 2014. Indications for repeated CT scans were categorized into: inadequate CT image data transfer, poor image quality, repetition of head CT after head injury together with completion to whole-body CT (WBCT), and follow-up of injury known from previous CT. Radiation doses from repeated CT were determined; costs were calculated using a nation-wide fee schedule. Results: Within one year, 85/298 (28.5%) trauma patients were transferred from another hospital because of severe head injury (n = 45,53%) and major body trauma (n = 23;27%) not manageable in the referring hospital, repatriation from a foreign country (n = 14;16.5%), and no ICU-capacity (n = 3;3.5%). Of these 85 patients, 74 (87%) had repeated CT in our center because of inadequate CT data transfer (n = 29;39%), repetition of head CT with completion to WBCT (n = 24;32.5%), and follow-up of known injury (n = 21;28.5%). None occurred because of poor image quality. Cumulative dose length product (DLP) and annual costs of potential preventable, repeated CT (inadequate data transfer) was 631mSv (81′304mGy*cm) and 35′233€, respectively. Conclusion: A considerable number of transferred trauma patients undergo potentially preventable, repeated CT, adding radiation dose to patients and costs to the health care system.

Repeated CT scans in trauma transfers: An analysis of indications, radiation dose exposure, and costs

Energy Technology Data Exchange (ETDEWEB)

Hinzpeter, Ricarda, E-mail: Ricarda.Hinzpeter@usz.ch [Institute of Diagnostic and Interventional Radiology, University Hospital Zurich, University of Zurich, Raemistr. 100, Zurich CH-8091 (Switzerland); Sprengel, Kai, E-mail: Kai.Sprengel@usz.ch [Division of Trauma Surgery, Department of Surgery, University Hospital Zurich, University of Zurich, Raemistr. 100, CH-8091 Zurich (Switzerland); Wanner, Guido A., E-mail: Guido.Wanner@sbk-vs.de [Division of Trauma Surgery, Department of Surgery, University Hospital Zurich, University of Zurich, Raemistr. 100, CH-8091 Zurich (Switzerland); Department of General Surgery, Schwarzwald-Baar Klinikum, University of Freiburg, Klinikstr. 11, D-78052 Villingen-Schwenningen (Germany); Mildenberger, Peter, E-mail: peter.mildenberger@unimedizin-mainz.de [Department of Diagnostic and Interventional Radiology, University Hospital of Mainz, Langenbeckstr. 1, D-55131 Mainz (Germany); Alkadhi, Hatem, E-mail: hatem.alkadhi@usz.ch [Institute of Diagnostic and Interventional Radiology, University Hospital Zurich, University of Zurich, Raemistr. 100, Zurich CH-8091 (Switzerland)

2017-03-15

Highlights: • Repetition of CT in trauma patients occurs relatively often. • Repetition of CT is mainly caused by inadequate image data transfer. • Potentially preventable CT examinations add radiation dose to patients. • Repeated CT is associated with excess costs to the health care system. - Abstract: Objectives: To identify the number of CT scans repeated in acute trauma patients receiving imaging before being referred to a trauma center, to define indications, and to assess radiation doses and costs of repeated CT. Methods: This retrospective study included all adult trauma patients transferred from other hospitals to a Level-I trauma center during 2014. Indications for repeated CT scans were categorized into: inadequate CT image data transfer, poor image quality, repetition of head CT after head injury together with completion to whole-body CT (WBCT), and follow-up of injury known from previous CT. Radiation doses from repeated CT were determined; costs were calculated using a nation-wide fee schedule. Results: Within one year, 85/298 (28.5%) trauma patients were transferred from another hospital because of severe head injury (n = 45,53%) and major body trauma (n = 23;27%) not manageable in the referring hospital, repatriation from a foreign country (n = 14;16.5%), and no ICU-capacity (n = 3;3.5%). Of these 85 patients, 74 (87%) had repeated CT in our center because of inadequate CT data transfer (n = 29;39%), repetition of head CT with completion to WBCT (n = 24;32.5%), and follow-up of known injury (n = 21;28.5%). None occurred because of poor image quality. Cumulative dose length product (DLP) and annual costs of potential preventable, repeated CT (inadequate data transfer) was 631mSv (81′304mGy*cm) and 35′233€, respectively. Conclusion: A considerable number of transferred trauma patients undergo potentially preventable, repeated CT, adding radiation dose to patients and costs to the health care system.

Some New Results in Astrophysical Problems of Nonlinear Theory of Radiative Transfer

Science.gov (United States)

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.

Radiative heat transfer in a heat generating and turbulently convecting fluid layer

International Nuclear Information System (INIS)

Cheung, F.B.; Chan, S.H.; Chawla, T.C.; Cho, D.H.

1980-01-01

The coupled problem of radiative transport and turbulent natural convection in a volumetrically heated, horizontal gray fluid medium, bounded from above by a rigid, isothermal wall and below by a rigid, adiabatic wall, is investigated analytically. An approximate method based upon the boundary layer approach is employed to obtain the dependence of heat transfer at the upper wall on the principal parameters of the problem, which, for moderate Prandtl number, are the Rayleigh number, Ra, the optical thickness, KL, and the conduction-radiation coupling parameter, N. Also obtained in this study is the behaviour of the thermal boundary layer at the upper wall. At large kL, the contribution of thermal radiation to heat transfer in the layer is found to be negligible for N > 10, moderate for N approximately 1, and overwhelming for N < 0.1. However, at small kL, thermal radiation is found to be important only for N < 0.01. While a higher level of turbulence results in a thinner boundary layer, a larger effect of radiation is found to result in a thicker one. Thus, in the presence of strong thermal radiation, a much larger value of Ra is required for the boundary layer approach to remain valid. Under severe radiation conditions, no boundary layer flow regime is found to exist even at very high Rayleigh numbers. Accordingly, the ranges of applicability of the present results are determined and the approximate method justified. In particular, the validity of the present analysis is tested in three limiting cases, ie those of kL → infinity, N → infinity, and Ra → infinity, and is further confirmed by comparison with the numerical solution (author)

Comparison of vibrational conductivity and radiative energy transfer methods

Science.gov (United States)

Le Bot, A.

2005-05-01

This paper is concerned with the comparison of two methods well suited for the prediction of the wideband response of built-up structures subjected to high-frequency vibrational excitation. The first method is sometimes called the vibrational conductivity method and the second one is rather known as the radiosity method in the field of acoustics, or the radiative energy transfer method. Both are based on quite similar physical assumptions i.e. uncorrelated sources, mean response and high-frequency excitation. Both are based on analogies with some equations encountered in the field of heat transfer. However these models do not lead to similar results. This paper compares the two methods. Some numerical simulations on a pair of plates joined along one edge are provided to illustrate the discussion.

Radiative charge-transfer lifetime of the excited state of (NaCa)+

International Nuclear Information System (INIS)

Makarov, Oleg P.; Cote, R.; Michels, H.; Smith, W.W.

2003-01-01

New experiments were proposed recently to investigate the regime of cold atomic and molecular ion-atom collision processes in a special hybrid neutral-atom-ion trap under high-vacuum conditions. We study the collisional cooling of laser precooled Ca + ions by ultracold Na atoms. Modeling this process requires knowledge of the radiative lifetime of the excited singlet A 1 Σ + state of the (NaCa) + molecular system. We calculate the rate coefficient for radiative charge transfer using a semiclassical approach. The dipole radial matrix elements between the ground and the excited states, and the potential curves were calculated using complete active space self-consistent field and Moeller-Plesset second-order perturbation theory with an extended Gaussian basis, 6-311+G (3df). The semiclassical charge-transfer rate coefficient was averaged over a thermal Maxwellian distribution. In addition, we also present elastic collision cross sections and the spin-exchange cross section. The rate coefficient for charge transfer was found to be 2.3x10 -16 cm 3 /sec, while those for the elastic and spin-exchange cross sections were found to be several orders of magnitude higher (1.1x10 -8 cm 3 /sec and 2.3x10 -9 cm 3 /sec, respectively). This confirms our assumption that the milli-Kelvin regime of collisional cooling of calcium ions by sodium atoms is favorable with the respect to low loss of calcium ions due to the charge transfer

Radiative transfer configuration factor catalog: A listing of relations for common geometries

International Nuclear Information System (INIS)

Howell, John R.; Menguec, M. Pinar

2011-01-01

An on-line compilation of radiation configuration factors for over 300 common geometries is provided as a supplementary material from the JQSRT web site at doi: (10.1016/j.jqsrt.2010.10.002). The factors are gathered from references across the radiative transfer and illumination engineering literature, as well as from applications in such diverse fields from combustion systems to human factors engineering. These factors are useful in standard surface-surface radiation exchange calculations, and are based on the assumptions that the surfaces exchanging radiation are diffuse, and that the radiosity from each surface is uniform across that surface. The catalog is updated annually, and can be downloaded from JQSRT in .PDF format.

A new vector radiative transfer model as a part of SCIATRAN 3.0 software package.

Science.gov (United States)

Rozanov, Alexei; Rozanov, Vladimir; Burrows, John P.

The SCIATRAN 3.0 package is a result of further development of the SCIATRAN 2.x software family which, similar to previous versions, comprises a radiative transfer model and a retrieval block. A major improvement was achieved in comparison to previous software versions by adding the vector mode to the radiative transfer model. Thus, the well-established Discrete Ordinate solver can now be run in the vector mode to calculate the scattered solar radiation including polarization, i.e., to simulate all four components of the Stockes vector. Similar to the scalar version, the simulations can be performed for any viewing geometry typical for atmospheric observations in the UV-Vis-NIR spectral range (nadir, limb, off-axis, etc.) as well as for any observer position within or outside the Earth's atmosphere. Similar to the precursor version, the new model is freely available for non-commercial use via the web page of the University of Bremen. In this presentation a short description of the software package, especially of the new vector radiative transfer model will be given, including remarks on the availability for the scientific community. Furthermore, comparisons to other vector models will be shown and some example problems will be considered where the polarization of the observed radiation must be accounted for to obtain high quality results.

Combined Natural Convection and Radiation Heat Transfer of Various Absorbing-Emitting-Scattering Media in a Square Cavity

Directory of Open Access Journals (Sweden)

Xianglong Liu

2014-01-01

Full Text Available A numerical model is developed to simulate combined natural convection and radiation heat transfer of various anisotropic absorbing-emitting-scattering media in a 2D square cavity based on the discrete ordinate (DO method and Boussinesq assumption. The effects of Rayleigh number, optical thickness, scattering ratio, scattering phase function, and aspect ratio of square cavity on the behaviors of heat transfer are studied. The results show that the heat transfer of absorbing-emitting-scattering media is the combined results of radiation and natural convection, which depends on the physical properties and the aspect ratio of the cavity. When the natural convection becomes significant, the convection heat transfer is enhanced, and the distributions of NuR and Nuc along the walls are obviously distorted. As the optical thickness increases, NuR along the hot wall decreases. As the scattering ratio decreases, the NuR along the walls decreases. At the higher aspect ratio, the more intensive thermal radiation and natural convection are formed, which increase the radiation and convection heat fluxes. This paper provides the theoretical research for the optimal thermal design and practical operation of the high temperature industrial equipments.

Multiple Scattering Principal Component-based Radiative Transfer Model (PCRTM) from Far IR to UV-Vis

Science.gov (United States)

Liu, X.; Wu, W.; Yang, Q.

2017-12-01

Modern satellite hyperspectral satellite remote sensors such as AIRS, CrIS, IASI, CLARREO all require accurate and fast radiative transfer models that can deal with multiple scattering of clouds and aerosols to explore the information contents. However, performing full radiative transfer calculations using multiple stream methods such as discrete ordinate (DISORT), doubling and adding (AD), successive order of scattering order of scattering (SOS) are very time consuming. We have developed a principal component-based radiative transfer model (PCRTM) to reduce the computational burden by orders of magnitudes while maintain high accuracy. By exploring spectral correlations, the PCRTM reduce the number of radiative transfer calculations in frequency domain. It further uses a hybrid stream method to decrease the number of calls to the computational expensive multiple scattering calculations with high stream numbers. Other fast parameterizations have been used in the infrared spectral region reduce the computational time to milliseconds for an AIRS forward simulation (2378 spectral channels). The PCRTM has been development to cover spectral range from far IR to UV-Vis. The PCRTM model have been be used for satellite data inversions, proxy data generation, inter-satellite calibrations, spectral fingerprinting, and climate OSSE. We will show examples of applying the PCRTM to single field of view cloudy retrievals of atmospheric temperature, moisture, traces gases, clouds, and surface parameters. We will also show how the PCRTM are used for the NASA CLARREO project.

Techniques of production and analysis of polarized synchrotron radiation

International Nuclear Information System (INIS)

Mills, D.M.

1992-01-01

The use of the unique polarization properties of synchrotron radiation in the hard x-ray spectral region (E>3 KeV) is becoming increasingly important to many synchrotron radiation researchers. The radiation emitted from bending magnets and conventional (planar) insertion devices (IDs) is highly linearly polarized in the plane of the particle's orbit. Elliptically polarized x-rays can also be obtained by going off axis on a bending magnet source, albeit with considerable loss of flux. The polarization properties of synchrotron radiation can be further tailored to the researcher's specific needs through the use of specialized insertion devices such as helical and crossed undulators and asymmetrical wigglers. Even with the possibility of producing a specific polarization, there is still the need to develop x-ray optical components which can manipulate the polarization for both analysis and further modification of the polarization state. A survey of techniques for producing and analyzing both linear and circular polarized x-rays will be presented with emphasis on those techniques which rely on single crystal optical components

New theory of radiative energy transfer in free electromagnetic fields

International Nuclear Information System (INIS)

Wolf, E.

1976-01-01

A new theory of radiative energy transfer in free, statistically stationary electromagnetic fields is presented. It provides a model for energy transport that is rigorous both within the framework of the stochastic theory of the classical field as well as within the framework of the theory of the quantized field. Unlike the usual phenomenological model of radiative energy transfer that centers around a single scalar quantity (the specific intensity of radiation), our theory brings into evidence the need for characterizing the energy transport by means of two (related) quantities: a scalar and a vector that may be identified, in a well-defined sense, with ''angular components'' of the average electromagnetic energy density and of the average Poynting vector, respectively. Both of them are defined in terms of invariants of certain new electromagnetic correlation tensors. In the special case when the field is statistically homogeneous, our model reduces to the usual one and our angular component of the average electromagnetic energy density, when multiplied by the vacuum speed of light, then acquires all the properties of the specific intensity of radiation. When the field is not statistically homogeneous our model approximates to the usual phenomenological one, provided that the angular correlations between plane wave modes of the field extend over a sufficiently small solid angle of directions about the direction of propagation of each mode. It is tentatively suggested that, when suitably normalized, our angular component of the average electromagnetic energy density may be interpreted as a quasi-probability (general quantum-mechancial phase-space distribution function, such as Wigner's) for the position and the momentum of a photon

Application of advanced model of radiative heat transfer in a rod geometry to QUENCH and PARAMETER tests

International Nuclear Information System (INIS)

Vasiliev, A.D.; Kobelev, G.V.; Astafieva, V.O.

2007-01-01

Radiative heat transfer is very important in different fields of mechanical engineering and related technologies including nuclear reactors, heat transfer in furnaces, aerospace, different high-temperature assemblies. In particular, in the course of a hypothetical severe accident at PWR-type nuclear reactor the temperatures inside the reactor vessel reach high values at which taking into account of radiative heat exchange between the structures of reactor (including core and other reactor vessel elements) gets important. Radiative heat transfer dominates the late phase of severe accident because radiative heat fluxes (proportional to T4, where T is the temperature) are generally considerably higher than convective and conductive heat fluxes in a system. In particular, heat transfer due to radiation determines the heating and degradation of the core and surrounding steel in-vessel structures and finally influences the composition, temperature and mass of materials pouring out of the reactor vessel after its loss of integrity. Existing models of radiative heat exchange use many limitations and approximations: approximate estimation of view factors and beam lengths; the geometry change in the course of the accident is neglected; the database for emissivities of materials is not complete; absorption/emission by steam-noncondensable medium is taken into account approximately. The module MRAD was developed in this paper to model the radiative heat exchange in rod-like geometry typical of PWR-type reactor. Radiative heat exchange is computed using dividing on zones (zonal method) as in existing radiation models implemented to severe accident numerical codes such as ICARE, SCDAP/RELAP, MELCOR but improved in following aspects: new approach to evaluation of view factors and mean beam length; detailed evaluation of gas absorptivity and emissivity; account of effective radiative thermal conductivity for the large core; account of geometry modification in the course of severe

Theory of many-body radiative heat transfer without the constraint of reciprocity

Science.gov (United States)

Zhu, Linxiao; Guo, Yu; Fan, Shanhui

2018-03-01

Using a self-consistent scattered field approach based on fluctuational electrodynamics, we develop compact formulas for radiative heat transfer in many-body systems without the constraint of reciprocity. The formulas allow for efficient numerical calculation for a system consisting of a large number of bodies, and are in principle exact. As a demonstration, for a nonreciprocal many-body system, we investigate persistent heat current at thermal equilibrium and directional heat transfer when the system is away from thermal equilibrium.

Radiative transfer with finite elements. Pt. 1. Basic method and tests

Energy Technology Data Exchange (ETDEWEB)

Richling, S. [Heidelberg Univ. (Germany). Inst. fuer Theoretische Astrophysik; Meinkoehn, E. [Heidelberg Univ. (Germany). Inst. fuer Theoretische Astrophysik]|[Heidelberg Univ. (Germany). Inst. fuer Angewandte Mathematik; Kryzhevoi, N. [Heidelberg Univ. (Germany). Inst. fuer Theoretische Astrophysik]|[Heidelberg Univ. (DE). Interdisziplinaeres Zentrum fuer Wissenschaftliches Rechnen (IWR); Kanschat, G. [Heidelberg Univ. (Germany). Inst. fuer Angewandte Mathematik]|[Heidelberg Univ. (DE). Interdisziplinaeres Zentrum fuer Wissenschaftliches Rechnen (IWR)

2001-10-01

A finite element method for solving the monochromatic radiation transfer equation including scattering in three dimensions is presented. The algorithm employs unstructured grids which are adaptively refined. Adaptivity as well as ordinate parallelization reduce memory requirements and execution time and make it possible to calculate the radiation field across several length scales for objects with strong opacity gradients. An a posteriori error estimate for one particular quantity is obtained by solving the dual problem. The application to a sample of test problems reveals the properties of the implementation. (orig.)

An introduction to heat transfer principles and calculations

CERN Document Server

Ede, A J; Ower, E

1967-01-01

An Introduction to Heat Transfer Principles and Calculations is an introductory text to the principles and calculations of heat transfer. The theory underlying heat transfer is described, and the principal results and formulae are presented. Available techniques for obtaining rapid, approximate solutions to complicated problems are also considered. This book is comprised of 12 chapters and begins with a brief account of some of the concepts, methods, nomenclature, and other relevant information about heat transfer. The reader is then introduced to radiation, conduction, convection, and boiling

Effect of radiation heat transfer on the performance of high temperature heat exchanger, (2)

International Nuclear Information System (INIS)

Yamada, Yukio; Mori, Yasuo; Hijikata, Kunio.

1977-01-01

In high temperature helium gas-cooled reactors, the nuclear energy can be utilized effectively, and the safety is excellent as compared with conventional reactors. They are advantageous also in view of environmental problems. In this report, the high temperature heat exchanger used for heating steam with the helium from a high temperature gas reactor is modeled, and the case that radiating gas flow between parallel plates is considered. Analysis was made on the case of one channel and constant heat flux and on the model for a counter-flow type heat exchanger with two channels, and the effect of radiation on the heat transfer in laminar flow and turbulent flow regions was clarified theoretically. The basic equations, the method of approximate solution and the results of calculation are explained. When one dimensional radiation was considered, the representative temperature Tr regarding fluid radiation was introduced, and its relation to mean mixing temperature Tm was determined. It was clarified that the large error in the result did not arise even if Tr was taken equally to Tm, especially in case of turbulent flow. The error was practically negligible when the rate of forced convection heat transfer in case of radiating medium flow was taken same as that in the case without radiation. (Kako, I.)

Unravelling radiative energy transfer in solid-state lighting

Science.gov (United States)

Melikov, Rustamzhon; Press, Daniel Aaron; Ganesh Kumar, Baskaran; Sadeghi, Sadra; Nizamoglu, Sedat

2018-01-01

Today, a wide variety of organic and inorganic luminescent materials (e.g., phosphors, quantum dots, etc.) are being used for lighting and new materials (e.g., graphene, perovskite, etc.) are currently under investigation. However, the understanding of radiative energy transfer is limited, even though it is critical to understand and improve the performance levels of solid-state lighting devices. In this study, we derived a matrix approach that includes absorption, reabsorption, inter-absorption and their iterative and combinatorial interactions for one and multiple types of fluorophores, which is simplified to an analytical matrix. This mathematical approach gives results that agree well with the measured spectral and efficiency characteristics of color-conversion light-emitting diodes. Moreover, it also provides a deep physical insight by uncovering the entire radiative interactions and their contribution to the output optical spectrum. The model is universal and applicable for all kinds of fluorophores.

Investigation of transient conduction–radiation heat transfer in a ...

Indian Academy of Sciences (India)

Mohammad Mehdi Keshtkar

2018-04-17

Apr 17, 2018 ... For absorbing, emitting and anisotropically scattering medium, the radiative heat transfer in any discrete direction s_m with direction index m is given as. dIm dsm. ¼ s_m. :rImрr; s_m. ЮјАbIm ю Sm. р16Ю .... thermore, V is the volume of the cell defined as dx В dy and. Im p and Sm p are the intensities and ...

The COBAIN (COntact Binary Atmospheres with INterpolation) Code for Radiative Transfer

Science.gov (United States)

Kochoska, Angela; Prša, Andrej; Horvat, Martin

2018-01-01

Standard binary star modeling codes make use of pre-existing solutions of the radiative transfer equation in stellar atmospheres. The various model atmospheres available today are consistently computed for single stars, under different assumptions - plane-parallel or spherical atmosphere approximation, local thermodynamical equilibrium (LTE) or non-LTE (NLTE), etc. However, they are nonetheless being applied to contact binary atmospheres by populating the surface corresponding to each component separately and neglecting any mixing that would typically occur at the contact boundary. In addition, single stellar atmosphere models do not take into account irradiance from a companion star, which can pose a serious problem when modeling close binaries. 1D atmosphere models are also solved under the assumption of an atmosphere in hydrodynamical equilibrium, which is not necessarily the case for contact atmospheres, as the potentially different densities and temperatures can give rise to flows that play a key role in the heat and radiation transfer.To resolve the issue of erroneous modeling of contact binary atmospheres using single star atmosphere tables, we have developed a generalized radiative transfer code for computation of the normal emergent intensity of a stellar surface, given its geometry and internal structure. The code uses a regular mesh of equipotential surfaces in a discrete set of spherical coordinates, which are then used to interpolate the values of the structural quantites (density, temperature, opacity) in any given point inside the mesh. The radiaitive transfer equation is numerically integrated in a set of directions spanning the unit sphere around each point and iterated until the intensity values for all directions and all mesh points converge within a given tolerance. We have found that this approach, albeit computationally expensive, is the only one that can reproduce the intensity distribution of the non-symmetric contact binary atmosphere and

Review of retrospective dosimetry techniques for external ionising radiation exposures

International Nuclear Information System (INIS)

Ainsbury, E. A.; Bakhanova, E.; Barquinero, J. F.; Brai, M.; Chumak, V.; Correcher, V.; Darroudi, F.; Fattibene, P.; Gruel, G.; Guclu, I.; Horn, S.; Jaworska, A.; Kulka, U.; Lindholm, C.; Lloyd, D.; Longo, A.; Marrale, M.; Monteiro Gil, O.; Oestreicher, U.; Pajic, J.; Rakic, B.; Romm, H.; Trompier, F.; Veronese, I.; Voisin, P.; Vral, A.; Whitehouse, C. A.; Wieser, A.; Woda, C.; Wojcik, A.; Rothkamm, K.

2011-01-01

The current focus on networking and mutual assistance in the management of radiation accidents or incidents has demonstrated the importance of a joined-up approach in physical and biological dosimetry. To this end, the European Radiation Dosimetry Working Group 10 on 'Retrospective Dosimetry' has been set up by individuals from a wide range of disciplines across Europe. Here, established and emerging dosimetry methods are reviewed, which can be used immediately and retrospectively following external ionising radiation exposure. Endpoints and assays include dicentrics, translocations, premature chromosome condensation, micronuclei, somatic mutations, gene expression, electron paramagnetic resonance, thermoluminescence, optically stimulated luminescence, neutron activation, haematology, protein biomarkers and analytical dose reconstruction. Individual characteristics of these techniques, their limitations and potential for further development are reviewed, and their usefulness in specific exposure scenarios is discussed. Whilst no single technique fulfils the criteria of an ideal dosemeter, an integrated approach using multiple techniques tailored to the exposure scenario can cover most requirements. (authors)

Physics of nuclear radiations concepts, techniques and applications

CERN Document Server

Rangacharyulu, Chary

2013-01-01

Physics of Nuclear Radiations: Concepts, Techniques and Applications makes the physics of nuclear radiations accessible to students with a basic background in physics and mathematics. Rather than convince students one way or the other about the hazards of nuclear radiations, the text empowers them with tools to calculate and assess nuclear radiations and their impact. It discusses the meaning behind mathematical formulae as well as the areas in which the equations can be applied. After reviewing the physics preliminaries, the author addresses the growth and decay of nuclear radiations, the stability of nuclei or particles against radioactive transformations, and the behavior of heavy charged particles, electrons, photons, and neutrons. He then presents the nomenclature and physics reasoning of dosimetry, covers typical nuclear facilities (such as medical x-ray machines and particle accelerators), and describes the physics principles of diverse detectors. The book also discusses methods for measuring energy a...

Salivary gland transfer to prevent radiation-induced xerostomia: a systematic review and meta-analysis.

Science.gov (United States)

Sood, Amit J; Fox, Nyssa F; O'Connell, Brendan P; Lovelace, Tiffany L; Nguyen, Shaun A; Sharma, Anand K; Hornig, Joshua D; Day, Terry A

2014-02-01

Salivary gland transfer (SGT) has the potential to prevent radiation-induced xerostomia. We attempt to analyze the efficacy of SGT in prevention of xerostomia and maintenance of salivary flow rates after radiation treatment (XRT). Systematic review and meta-analysis. Primary endpoint was efficacy of SGT in prevention of radiation-induced xerostomia. Secondary endpoint was change from baseline of unstimulated and stimulated salivary flow rates after XRT. Seven articles, accruing data from 12 institutions, met inclusion criteria. In a total of 177 patients at mean follow-up of 22.7months, SGT prevented radiation-induced xerostomia in 82.7% (95% CI, 76.6-87.7%) of patients. Twelve months after XRT, unstimulated and stimulated salivary flow rates rose to 88% and 76% of baseline values, respectively. In comparison to control subjects twelve months after XRT, SGT subjects' unstimulated (75% vs. 11%) and stimulated (86% vs. 8%) salivary flow rates were drastically higher in SGT patients. Salivary gland transfer appears to be highly effective in preventing the incidence of xerostomia in patients receiving definitive head and neck radiation therapy. Copyright © 2013 Elsevier Ltd. All rights reserved.

Study on production of useful metabolites by development of advanced cell culture techniques using radiation

Energy Technology Data Exchange (ETDEWEB)

Chung, Byung Yeoup; Lee, Seung Sik; Bai, Hyounwoo; Singh, Sudhir; Lee, Eun Mi; Hong, Sung Hyun; Park, Chul Hong; Srilatha, B.; Kim, Mi Ja; Lee, Ohchul

2012-01-15

The purpose of this project is improvement of investigation, materialization and evaluation techniques on effectiveness for functional natural compounds throughout development of tissue/cell culture techniques for mass production of useful metabolites using radiation. Research scope includes Development of a technique for radiation tissue and cell culture, Database construction for radiation response in plants and radiation effects, Construction of general-purpose national based techniques of cell culture technique using radiation. Main results are as follow: Development of a technique for radiation tissue and cell culture for Erigeron breviscapus (Vant.) Hand. Mazz.; Identification and functional analysis of AtTDX (chaperone and peroxidase activities); Functional analysis of radiation(gamma ray, electron beam, and proton beam) induced chaperon protein activities (AtTDX); Determine the action mechanism of yPrx2; Development of transgenic plant with bas I gene from Arabidopsis; Development of transgenic plant with EoP gene from centipedegrass; Identification of radiation induced multi functional compounds from Aloe; Determination of the effects of radiation on removing undesirable color and physiological activities (Schizandra chinensis baillon, centipedegrass); Determine the action mechanism of transgenic plant with 2-Cys Prx for heat stress resistance; Determination of the effects of centipedegrass extracts on anti-cancer activities; Functional analysis of centipedegrass extracts (anti-virus effects)

Primary processes in radiation chemistry. LET (Linear Energy Transfer) effect in water radiolysis

International Nuclear Information System (INIS)

Trupin-Wasselin, V.

2000-01-01

The effect of ionizing radiations on aqueous solutions leads to water ionization and then to the formation of radical species and molecular products (e - aq , H . , OH . , H 2 O 2 , H 2 ). It has been shown that the stopping power, characterized by the LET value (Linear Energy Transfer) becomes different when the nature of the ionizing radiations is different. Few data are nowadays available for high LET radiations such as protons and high energy heavy ions. These particles have been used to better understand the primary processes in radiation chemistry. The yield of a chemical dosimeter (the Fricke dosimeter) and those of the hydrogen peroxide have been determined for different LET. The effect of the dose rate on the Fricke dosimeter yield and on the H 2 O 2 yield has been studied too. When the dose rate increases, an increase of the molecular products yield is observed. At very high dose rate, this yield decreases on account of the attack of the molecular products by radicals. The H 2 O 2 yield in alkaline medium decreases when the pH reaches 12. This decrease can be explained by a slowing down of the H 2 O 2 formation velocity in alkaline medium. Superoxide radical has also been studied in this work. A new detection method: the time-resolved chemiluminescence has been perfected for this radical. This technique is more sensitive than the absorption spectroscopy. Experiments with heavy ions have allowed to determine the O 2 .- yield directly in the irradiation cell. The experimental results have been compared with those obtained with a Monte Carlo simulation code. (O.M.)

ARTS, the Atmospheric Radiative Transfer Simulator - version 2.2, the planetary toolbox edition

Science.gov (United States)

Buehler, Stefan A.; Mendrok, Jana; Eriksson, Patrick; Perrin, Agnès; Larsson, Richard; Lemke, Oliver

2018-04-01

This article describes the latest stable release (version 2.2) of the Atmospheric Radiative Transfer Simulator (ARTS), a public domain software for radiative transfer simulations in the thermal spectral range (microwave to infrared). The main feature of this release is a planetary toolbox that allows simulations for the planets Venus, Mars, and Jupiter, in addition to Earth. This required considerable model adaptations, most notably in the area of gaseous absorption calculations. Other new features are also described, notably radio link budgets (including the effect of Faraday rotation that changes the polarization state) and the treatment of Zeeman splitting for oxygen spectral lines. The latter is relevant, for example, for the various operational microwave satellite temperature sensors of the Advanced Microwave Sounding Unit (AMSU) family.

Polymers under ionizing radiation: the study of energy transfers to radiation induced defects

International Nuclear Information System (INIS)

Ventura, A.

2013-01-01

Radiation-induced defects created in polymers submitted to ionizing radiations, under inert atmosphere, present the same trend as a function of the dose. When the absorbed dose increases, their concentrations increase then level off. This behavior can be assigned to energy transfers from the polymer to the previously created macromolecular defects; the latter acting as energy sinks. During this thesis, we aimed to specify the influence of a given defect, namely the trans-vinylene, in the behavior of polyethylene under ionizing radiations. For this purpose, we proposed a new methodology based on the specific insertion, at various concentrations, of trans-vinylene groups in the polyethylene backbone through chemical synthesis. This enables to get rid of the variety of created defects on one hand and on the simultaneity of their creation on the other hand. Modified polyethylenes, containing solely trans-vinylene as odd groups, were irradiated under inert atmosphere, using either low LET beams (gamma, beta) or high LET beams (swift heavy ions). During irradiations, both macromolecular defects and H 2 emission were quantified. According to experimental results, among all defects, the influence of the trans-vinylene on the behavior of polyethylene is predominant. (author) [fr

Radiation technique in conservation of antique objects - achievement in Poland

International Nuclear Information System (INIS)

Perkowski, J.

2002-01-01

In this work the progress of the radiation technique in conservation of antique objects in Poland was presented. From two, quite different problems: radiation's disinfection or consolidation, only the first one was applied in our country. The technique of radiation disinfection and desinsection was applied only in the nine cases, in spite of numerous propaganda's information's and advertisement's actions. It were both wooden antiques (altars, sculptures, furniture), sandstone sculpture and prison footwear. In the first case it was connected with destruction of the wood's pest, in the second with bacteria which were destroying of the object inside and in the third with the elimination of the moulds, fungus and bacteria. Differ dose of gamma radiation was applied, depending on the kind and size of initial infection. The time of the operation depended on the quality of the dose rate which was connected first of all with the size and shape of the object. Decisive significance for obtained values of irregular distribution absorbed radiation dose had the type of the material in which the object was done and it's size. (author)

Transfer printing techniques for materials assembly and micro/nanodevice fabrication.

Science.gov (United States)

Carlson, Andrew; Bowen, Audrey M; Huang, Yonggang; Nuzzo, Ralph G; Rogers, John A

2012-10-09

Transfer printing represents a set of techniques for deterministic assembly of micro-and nanomaterials into spatially organized, functional arrangements with two and three-dimensional layouts. Such processes provide versatile routes not only to test structures and vehicles for scientific studies but also to high-performance, heterogeneously integrated functional systems, including those in flexible electronics, three-dimensional and/or curvilinear optoelectronics, and bio-integrated sensing and therapeutic devices. This article summarizes recent advances in a variety of transfer printing techniques, ranging from the mechanics and materials aspects that govern their operation to engineering features of their use in systems with varying levels of complexity. A concluding section presents perspectives on opportunities for basic and applied research, and on emerging use of these methods in high throughput, industrial-scale manufacturing. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

ANALYTICAL SOLUTIONS FOR RADIATIVE TRANSFER: IMPLICATIONS FOR GIANT PLANET FORMATION BY DISK INSTABILITY

International Nuclear Information System (INIS)

Boss, Alan P.

2009-01-01

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.

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

Science.gov (United States)

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

The fourth phase of the radiative transfer model imtercomparison (RAMI) exercise

Czech Academy of Sciences Publication Activity Database

Widlowski, J. L.; Mio, C.; Disney, M.; Adams, J.; Andredakis, I.; Atzberger, C.; Brennan, J.; Busetto, L.; Chelle, M.; Ceccherini, G.; Colombo, R.; Coté, J. F.; Eenmäe, A.; Essery, R.; Gastellu-Etchegory, J.P.; Gobron, N.; Grau, E.; Haverd, V.; Homolová, Lucie; Huang, H.; Hunt, L.; Kobayashi, H.; Koetz, B.; Kuusk, A.; Kuusk, J.; Lang, M.; Lewis, P. E.; Lovell, J. L.; Malenovský, Z.; Michele, M.; Mordsorf, F.; Mottus, M.; Ni-Meister, W.; Pinty, B.; Rautianien, M.; Schlerf, M.; Somers, B.; Stuckens, J.; Vestraete, M. M.; Yang, W.; Zhao, F.; Zenone, T.

2015-01-01

Roč. 169, nov (2015), s. 418-437 ISSN 0034-4257 Institutional support: RVO:67179843 Keywords : conformity testing * radiative transfer * model benchmarking * 3D virtual plant canopy * digital hemispherical photography * optical remote sensing * shared risk * guarded acceptance * GCOS * ISO -13528 Subject RIV: EH - Ecology, Behaviour Impact factor: 5.881, year: 2015

Experimental study on the heat transfer of MWCNT/water nanofluid flowing in a car radiator

International Nuclear Information System (INIS)

Oliveira, Guilherme Azevedo; Cardenas Contreras, Edwin Martin; Bandarra Filho, Enio Pedone

2017-01-01

This study is concerned with an experimental evaluation of the thermal performance of multi-walled carbon nanotubes (MWCNT) dispersed in distilled water flowing inside an automotive radiator. A two-step method called high-pressure homogenization was used to disperse the MWCNT nanoparticles in water, in concentrations varying between 0.05 and 0.16 wt%. Experiments have been carried out in an experimental set up composed by a wind tunnel that simulates the air flow through a car radiator, and a hot fluid circuit, that circulates the nanofluid inside the radiator. The air flow rate was maintained constant at 0.175 kg/s. The mass flow rate of the hot fluid varied from 30 up to 70 g/s and the inlet temperature was maintained constant at 50, 60, 70 and 80 °C, respectively. The temperature drop and heat transfer rate have been investigated. A slight-decrease on the heat transfer rate, up to 5%, was found for all test conditions. On the other hand as the nanoparticle concentration increased, the heat transfer rate decreased.

Dose measurement techniques for high-energy photon and electron radiation

International Nuclear Information System (INIS)

Hohlfeld, K.; Roos, M.

1992-08-01

By law the Federal Institute of Physics and Technology (PTB) has been assigned the tasks of representing, preserving and passing on dose units. The analogous continuation of these tasks consists in improving, at the user level, dosimetry techniques in radiation therapy for the benefit of patients. The PTB had an essential share in working out the scientific foundations of dosimetry for high-energy radiation, and the corresponding DIN standards were established with the PTB playing a prominent part. The seminar aimed at presenting the measuring techniques fixed in the new DIN standard 6800 part 2 'Dose measurement techniques according to the probe method - ionization dosimetry', to discuss their physical background and practical implications resulting from them. (orig.) [de

Vehicle tracking based technique for radiation monitoring during nuclear or radiological emergency

International Nuclear Information System (INIS)

Saindane, Shashank S.; Otari, Anil D.; Suri, M.M.K.; Patil, S.S.; Pradeepkumar, K.S.; Sharma, D.N.

2010-01-01

Radiation Safety Systems Division, BARC has developed an advanced online radiation measurement cum vehicle tracking system for use. For the preparedness for response to any nuclear/radiological emergency scenario which may occur anywhere, the system designed is a Global System for Mobile (GSM) based Radiation Monitoring System (GRaMS) along with a Global Positioning System (GPS). It uses an energy compensated GM detector for radiation monitoring and is attached with commercially available Global Positioning System (GPS) for online acquisition of positional coordinates with time, and GSM modem for online data transfer to a remote control centre. The equipment can be operated continuously while the vehicle is moving

Radiative heat transfer enhancement using geometric and spectral control for achieving high-efficiency solar-thermophotovoltaic systems

Science.gov (United States)

Kohiyama, Asaka; Shimizu, Makoto; Yugami, Hiroo

2018-04-01

We numerically investigate radiative heat transfer enhancement using spectral and geometric control of the absorber/emitter. A high extraction of the radiative heat transfer from the emitter as well as minimization of the optical losses from the absorber leads to high extraction and solar thermophotovoltaic (STPV) system efficiency. The important points for high-efficiency STPV design are discussed for the low and high area ratio of the absorber/emitter. The obtained general guideline will support the design of various types of STPV systems.

Active control of near-field radiative heat transfer between graphene-covered metamaterials

Science.gov (United States)

Zhao, Qimei; Zhou, Ting; Wang, Tongbiao; Liu, Wenxing; Liu, Jiangtao; Yu, Tianbao; Liao, Qinghua; Liu, Nianhua

2017-04-01

In this study, the near-field radiative heat transfer between graphene-covered metamaterials is investigated. The electric surface plasmons (SPs) supported by metamaterials can be coupled with the SPs supported by graphene. The near-field heat transfer between the graphene-covered metamaterials is significantly larger than that between metamaterials because of the strong coupling in our studied frequency range. The relationship between heat flux and chemical potential is studied for different vacuum gaps. Given that the chemical potential of graphene can be tuned by the external electric field, heat transfer can be actively controlled by modulating the chemical potential. The heat flux for certain vacuum gaps can reach a maximum value when the chemical potential is at a particular value. The results of this study are beneficial for actively controlling energy transfer.

Radiation heat transfer model in a spent fuel pool by TRACE code

International Nuclear Information System (INIS)

Sanchez-Saez, F.; Carlos, S.; Villanueva, J.F.; Martorell, S.

2014-01-01

Nuclear policies have experienced an important change since Fukushima Daiichi nuclear plant accident and the safety of spent fuels has been in the spot issue among all the safety concerns. The work presented consists of the thermohydraulic simulation of spent fuel pool behavior after a loss of coolant throughout transfer channel with loss of cooling transient is produced. The simulation is done with the TRACE code. One of the most important variables that define the behavior of the pool is cladding temperature, which evolution depends on the heat emission. In this work convection and radiation heat transfer is considered. When both heat transfer models are considered, a clear delay in achieving the maximum peak cladding temperature (1477 K) is observed compared with the simulation in which only convection heat transfer is considered. (authors)

Active control of near-field radiative heat transfer between graphene-covered metamaterials

International Nuclear Information System (INIS)

Zhao, Qimei; Zhou, Ting; Wang, Tongbiao; Liu, Wenxing; Liu, Jiangtao; Yu, Tianbao; Liao, Qinghua; Liu, Nianhua

2017-01-01

In this study, the near-field radiative heat transfer between graphene-covered metamaterials is investigated. The electric surface plasmons (SPs) supported by metamaterials can be coupled with the SPs supported by graphene. The near-field heat transfer between the graphene-covered metamaterials is significantly larger than that between metamaterials because of the strong coupling in our studied frequency range. The relationship between heat flux and chemical potential is studied for different vacuum gaps. Given that the chemical potential of graphene can be tuned by the external electric field, heat transfer can be actively controlled by modulating the chemical potential. The heat flux for certain vacuum gaps can reach a maximum value when the chemical potential is at a particular value. The results of this study are beneficial for actively controlling energy transfer. (paper)

Impact of melting heat transfer and nonlinear radiative heat flux mechanisms for the generalized Burgers fluids

Directory of Open Access Journals (Sweden)

Waqar Azeem Khan

Full Text Available The present paper deals with the analysis of melting heat and mass transfer characteristics in the stagnation point flow of an incompressible generalized Burgers fluid over a stretching sheet in the presence of non-linear radiative heat flux. A uniform magnetic field is applied normal to the flow direction. The governing equations in dimensional form are reduced to a system of dimensionless expressions by implementation of suitable similarity transformations. The resulting dimensionless problem governing the generalized Burgers is solved analytically by using the homotopy analysis method (HAM. The effects of different flow parameters like the ratio parameter, magnetic parameter, Prandtl number, melting parameter, radiation parameter, temperature ratio parameter and Schmidt number on the velocity, heat and mass transfer characteristics are computed and presented graphically. Moreover, useful discussions in detail are carried out with the help of plotted graphs and tables. Keywords: Generalized Burgers fluid, Non-linear radiative flow, Magnetic field, Melting heat transfer

Monitoring glycolipid transfer protein activity and membrane interaction with the surface plasmon resonance technique.

Science.gov (United States)

Ohvo-Rekilä, Henna; Mattjus, Peter

2011-01-01

The glycolipid transfer protein (GLTP) is a protein capable of binding and transferring glycolipids. GLTP is cytosolic and it can interact through its FFAT-like (two phenylalanines in an acidic tract) motif with proteins localized on the surface of the endoplasmic reticulum. Previous in vitro work with GLTP has focused mainly on the complete transfer reaction of the protein, that is, binding and subsequent removal of the glycolipid from the donor membrane, transfer through the aqueous environment, and the final release of the glycolipid to an acceptor membrane. Using bilayer vesicles and surface plasmon resonance spectroscopy, we have now, for the first time, analyzed the binding and lipid removal capacity of GLTP with a completely label-free technique. This technique is focused on the initial steps in GLTP-mediated transfer and the parameters affecting these steps can be more precisely determined. We used the new approach for detailed structure-function studies of GLTP by examining the glycolipid transfer capacity of specific GLTP tryptophan mutants. Tryptophan 96 is crucial for the transfer activity of the protein and tryptophan 142 is an important part of the proteins membrane interacting domain. Further, we varied the composition of the used lipid vesicles and gained information on the effect of membrane properties on GLTP activity. GLTP prefers to interact with more tightly packed membranes, although GLTP-mediated transfer is faster from more fluid membranes. This technique is very useful for the study of membrane-protein interactions and lipid-transfer rates and it can easily be adapted to other membrane-interacting proteins. Copyright © 2010 Elsevier B.V. All rights reserved.

Simplification of Bovine Somatic Cell Nuclear Transfer by Application of a Zona-Free Manipulation Technique

DEFF Research Database (Denmark)

Booth, Paul J; Tan, Shijian; Reipurth, Rikke

2001-01-01

Contemporary nuclear transfer techniques often require the involvement of skilled personnel and extended periods of micromanipulation. Here, we present details of the development of a nuclear transfer technique for somatic cells that is both simpler and faster than traditional methods. The techni......Contemporary nuclear transfer techniques often require the involvement of skilled personnel and extended periods of micromanipulation. Here, we present details of the development of a nuclear transfer technique for somatic cells that is both simpler and faster than traditional methods....... The technique comprises the bisection of zona-free oocytes and the reconstruction of embryos comprising two half cytoplasts and a somatic cell by adherence using phytohaemagglutinin-P (PHA) followed by an electropulse and subsequent culture in microwells (termed WOWs--well of the well). The development......-intact zygotes were not different in either blastocyst yield (44.6 +/- 2.4% versus 51.8 +/- 13.5% [mean +/- SEM]) or quality (126.3 +/- 48.4 versus 119.9 +/- 32.6 total cells), and exposure of zygotes to PHA-P did not reduce blastocyst yields compared to vehicle control (40.8 +/- 11.6% versus 47.1 +/- 20...

An Accurate Technique for Calculation of Radiation From Printed Reflectarrays

DEFF Research Database (Denmark)

Zhou, Min; Sorensen, Stig B.; Jorgensen, Erik

2011-01-01

The accuracy of various techniques for calculating the radiation from printed reflectarrays is examined, and an improved technique based on the equivalent currents approach is proposed. The equivalent currents are found from a continuous plane wave spectrum calculated by use of the spectral dyadic...... Green's function. This ensures a correct relation between the equivalent electric and magnetic currents and thus allows an accurate calculation of the radiation over the entire far-field sphere. A comparison to DTU-ESA Facility measurements of a reference offset reflectarray designed and manufactured...

Heterodyne technique for measuring the amplitude and phase transfer functions of an optical modulator

DEFF Research Database (Denmark)

Romstad, Francis Pascal; Birkedal, Dan; Mørk, Jesper

2002-01-01

In this letter, we propose a technique based on heterodyne detection for accurately and simultaneously measuring the amplitude and phase transfer functions of an optical modulator. The technique is used to characterize an InGaAsp multiple quantum-well electroabsorption modulator. From the measure...... the measurements we derive the small-signal alpha-parameter and the time-dependent chirp for different operation conditions.......In this letter, we propose a technique based on heterodyne detection for accurately and simultaneously measuring the amplitude and phase transfer functions of an optical modulator. The technique is used to characterize an InGaAsp multiple quantum-well electroabsorption modulator. From...

Role of cytogenetic techniques in biological dosimetry of absorbed radiation

International Nuclear Information System (INIS)

Rao, B.S.

2016-01-01

In most of the radiation accidents, physical dosimetric information is rarely available. Further, most of the accidental exposures are non-uniform involving either partial body or localized exposure to significant doses. In such situations, physical dosimetry does not provide reliable dose estimate. It has now been realized that biological dosimetric techniques can play an important role in the assessment of absorbed dose. In recent years, a number of biological indicators of radiation have been identified. These include the kinetics of onset and persistence of prodromal syndromes (radiation sickness), cytogenetic changes in peripheral blood lymphocytes, hematological changes, biochemical indicators, ESR spectroscopy of biological samples, induction of gene mutations in red blood cells, cytogenetic and physiological changes in skin and neurophysiological changes. In general, dosimetric information is derived by a combination of several different methods, as they have potential to serve as prognostic indicators. The role of cytogenetic techniques in peripheral blood lymphocytes (PBL) as biological indicators of absorbed radiation is reviewed here

Study of mixed radiative thermal mass transfer in the case of spherical liquide particle evaporation in a high temperature thermal air plasma

International Nuclear Information System (INIS)

Garandeau, S.

1984-01-01

Radiative transfer in a semi-transparent non-isothermal medium with spherical configuration has been studied. Limit conditions have been detailed, among which the semi-transparent inner sphere case is a new case. Enthalpy and matter transfer equations related to these different cases have been established. An adimensional study of local conservation laws allowed to reveal a parameter set characteristic of radiation coupled phenomena thermal conduction, convection, diffusion. Transfer equations in the case of evaporation of a liquid spherical particle in an air thermal plasma have been simplified. An analytical solution for matter transfer is proposed. Numerical solution of radiative problems and matter transfer has been realized [fr

Assessing a new gene expression analysis technique for radiation biodosimetry applications

Energy Technology Data Exchange (ETDEWEB)

Manning, Grainne; Kabacik, Sylwia; Finnon, Paul; Paillier, Francois; Bouffler, Simon [Cancer Genetics and Cytogenetics, Biological Effects Department, Centre for Radiation, Chemical and Environmental Hazards, Health Protection Agency, Chilton, Didcot, Oxfordshire OX11 ORQ (United Kingdom); Badie, Christophe, E-mail: christophe.badie@hpa.org.uk [Cancer Genetics and Cytogenetics, Biological Effects Department, Centre for Radiation, Chemical and Environmental Hazards, Health Protection Agency, Chilton, Didcot, Oxfordshire OX11 ORQ (United Kingdom)

2011-09-15

The response to any radiation accident or incident involving actual or potential ionising radiation exposure requires accurate and rapid assessment of the doses received by individuals. The techniques available today for biodosimetry purposes are not fully adapted to rapid high-throughput measurements of exposures in large numbers of individuals. A recently emerging technique is based on gene expression analysis, as there are a number of genes which are radiation responsive in a dose-dependent manner. The present work aimed to assess a new technique which allows the detection of the level of expression of up to 800 genes without need of enzymatic reactions. In order to do so, human peripheral blood was exposed ex vivo to a range of x-ray doses from 5 mGy to 4 Gy of x-rays and the transcriptional expression of five radiation-responsive genes PHPT1, PUMA, CCNG1, DDB2 and MDM2 was studied by both the nCounter Digital Analyzer and Multiplex Quantitative Real-Time Polymerase Chain Reaction (MQRT-PCR) as the benchmark technology. Results from both techniques showed good correlation for all genes with R{sup 2} values ranging between 0.8160 and 0.9754. The reproducibility of the nCounter Digital Analyzer was also assessed in independent biological replicates and proved to be good. Although the slopes of the correlation of results obtained by the techniques suggest that MQRT-PCR is more sensitive than the nCounter Digital Analyzer, the nCounter Digital Analyzer provides sensitive and reliable data on modifications in gene expression in human blood exposed to radiation without enzymatic amplification of RNA prior to analysis.